Your SlideShare is downloading. ×
Umts rno subject 2 g3g interoperation analysis guide-r2.0
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Umts rno subject 2 g3g interoperation analysis guide-r2.0

2,519

Published on

Published in: Education, Technology, Business
0 Comments
5 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
2,519
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
363
Comments
0
Likes
5
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. 2G-3G Interoperation Analysis Guide R2.0
  • 2. 2G-3G Interoperation Analysis Guide Internal Use Only▲ LEGAL INFORMATION By accepting this certain document of ZTE CORPORATION you agree to the following terms. If you do not agree to the following terms, please notice that you are not allowed to use this document. Copyright © 2014 ZTE CORPORATION. Any rights not expressly granted herein are reserved. This document contains proprietary information of ZTE CORPORATION. Any reproduction, transfer, distribution, use or disclosure of this document or any portion of this document, in any form by any means, without the prior written consent of ZTE CORPORATION is prohibited. and are registered trademarks of ZTE CORPORATION. ZTE’s company name, logo and product names referenced herein are either trademarks or registered trademarks of ZTE CORPORATION. Other product and company names mentioned herein may be trademarks or trade names of their respective owners. Without the prior written consent of ZTE CORPORATION or the third party owner thereof, anyone’s access to this document should not be construed as granting, by implication, estopped or otherwise, any license or right to use any marks appearing in the document. The design of this product complies with requirements of environmental protection and personal security. This product shall be stored, used or discarded in accordance with product manual, relevant contract or laws and regulations in relevant country (countries). This document is provided “as is” and “as available”. Information contained in this document is subject to continuous update without further notice due to improvement and update of ZTE CORPORATION’s products and technologies. ZTE CORPORATION Address: NO. 55 Hi-tech Road South ShenZhen P.R.China 518057 Website: http://support.zte.com.cn Email: 800@zte.com.cn ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. I
  • 3. 2G-3G Interoperation Analysis Guide Internal Use Only▲ Revision History Product Version RNC V3.07 Document Version Serial Number R1.0 Reason for Revision First published 1. RNC V3.09 2. R2.0 3. 4. Add the analysis of key 2G-3G networking parameters and configuration suggestions. Delete some old parts. Optimize the document structure. Replace some unclear figures. Author Date Document Version Prepared by Reviewed by Approved by 2009-12-20 R1.0 Song Jianjun Expert group Expert group 2012-05-16 R2.0 Ma Wei Wang Zhenhai Wang Zhenhai ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. II
  • 4. 2G-3G Interoperation Analysis Guide Internal Use Only▲ Intended audience: Radio network optimization engineers Proposal: Before reading this document, you had better have the following knowledge and skills. SEQ 1 Knowledge and skills Null Reference material Null 2 3 Follow-up document: After reading this document, you may need the following information. SEQ 1 Reference material Null Information Null 2 ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. III
  • 5. 2G-3G Interoperation Analysis Guide Internal Use Only▲ About This Document Summary Chapter 1 Preface Description Gives a brief introduction to this guide. 2 Introduction to 2G/3G Interoperability Describes the PLMN selection and reselection, cell selection and reselection, and inter-RAT handover. 3 2G/3G Interoperability Parameters Describes the key parameters of 2G-3G interoperation. 4 Interoperability Problems Analysis and Optimization Describes the analysis of common 2G-3G interoperation problems and optimization suggestions. 5 Gives some typical cases of 2G-3G interoperation. Cases Study ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. IV
  • 6. 2G-3G Interoperation Analysis Guide Internal Use Only▲ TABLE OF CONTENTS 1 Preface ............................................................................................................ 1 2 2.1 2.2 2.2.1 2.2.2 2.3 2.3.1 2.3.2 2.3.3 2.3.4 2.3.5 2.4 2.4.1 2.4.2 2.4.3 2.4.4 Introduction to 2G/3G Interoperability .......................................................... 2 Network Elements Structure for 2G/3G Interoperability ..................................... 2 PLMN Selection and Reselection...................................................................... 3 Process Description .......................................................................................... 3 Application Analysis for PLMN Selection and Reselection ................................ 5 Cell Selection and Reselection ......................................................................... 6 Process Description for Cell Selection .............................................................. 6 Scenario of Inter-RAT Cell Reselection............................................................. 7 Policy of Inter-RAT Cell Reselection ................................................................. 8 Reselection from 3G to 2G ............................................................................... 8 Reselection from 2G to 3G ............................................................................. 12 Inter-RAT Handover........................................................................................ 12 Inter-RAT Handover Scenario ......................................................................... 12 Inter-RAT Handover Strategies ....................................................................... 12 Measurements and Decisions before Inter-RAT Handover ............................. 13 Inter-RAT Handover Processes ...................................................................... 17 3 3.1 3.2 3.2.1 3.2.2 3.2.3 3.3 3.3.1 3.3.2 3.3.3 3.3.4 3.4 2G/3G Interoperability Parameters .............................................................. 33 2G/3G Interconnection Parameters ................................................................ 33 Typical Selection and Reselection Parameters ............................................... 33 Key 2G->3G Reselection Parameters ............................................................. 34 Key 3G->2G Reselection Parameters ............................................................. 36 Recommended Values of Key Reselection Parameters .................................. 46 Typical Inter-RAT Handover Parameters ........................................................ 48 2D/2F Event Threshold ................................................................................... 48 3A/3C Event Threshold ................................................................................... 49 Hysteresis(Rat) ............................................................................................... 51 Recommended Values of Key Inter-RAT Handover Parameters ..................... 53 Setting for 2G/3G Inter-RAT Neighbor Cells ................................................... 53 4 4.1 4.2 4.2.1 4.2.2 4.2.3 4.2.4 4.2.5 4.2.6 Interoperability Problems Analysis and Optimization................................ 55 Reselection Problems Analysis and Optimization ........................................... 56 Handover Problems Analysis and Optimization .............................................. 57 Physical Channel Failure ................................................................................ 58 Wrong Configuration ....................................................................................... 59 Protocol Error ................................................................................................. 59 Parameter Configuration ................................................................................. 59 Neighbor Cell Configuration ............................................................................ 60 Resource Refusing ......................................................................................... 60 5 5.1 5.1.1 Cases Study .................................................................................................. 61 PLMN Selection and Reselection.................................................................... 61 Case 1 ............................................................................................................ 61 ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. V
  • 7. 2G-3G Interoperation Analysis Guide 5.2 5.2.1 5.2.2 5.3 5.3.1 5.3.2 5.3.3 5.3.4 5.3.5 5.3.6 Internal Use Only▲ Cell Selection and Reselection ....................................................................... 62 Case 1 ............................................................................................................ 62 Case 2 ............................................................................................................ 62 Inter-RAT Handover........................................................................................ 63 Case 1 ............................................................................................................ 63 Case 2 ............................................................................................................ 66 Case 3 ............................................................................................................ 67 Case 4 ............................................................................................................ 67 Case 5 ............................................................................................................ 69 Case 6 ............................................................................................................ 71 ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. VI
  • 8. 2G-3G Interoperation Analysis Guide Internal Use Only▲ FIGURES Figure 2-1 Network Elements Structure for 2G/3G Interoperability ....................................... 2 Figure 2-2 Idle Mode Process Description ............................................................................ 3 Figure 2-3 Scenario of 2G/3G Inter-RAT Cell Reselection for UE ......................................... 8 Figure 2-4 General Process of Reselection from 3G to 2G ................................................. 11 Figure 2-5 Reselection Process for the Case that WCDMA Signal Strength is too Weak to Maintain Normal Network Service ......................................................................................... 12 Figure 2-6 Handover from WCDMA to GSM in CS Domain ................................................ 14 Figure 2-7 Handover from GSM to WCDMA in CS Domain ................................................ 15 Figure 2-8 Signaling Process of Inter-RAT Handover in MSC: WCDMA->GSM .................. 17 Figure 2-9 Signaling Process of Handover from WCDMA to GSM ...................................... 20 Figure 2-10 Inter-RAT Handover in SGSN From UTUE To GSM (Group Domain).............. 22 Figure 2-11 Handover between SGSNs From UMTS To GSM (group domain) .................. 24 Figure 2-12 nter-RAT Handover From GSM To UMTS in SGSN (Group Domain) .............. 27 Figure 2-13 Inter-RAT Handover From GSM To UMTS in SGSN (Group Domain) ............. 29 Figure 4-1 RR Cause Information Element ......................................................................... 57 Figure 5-1 Sites Locations of 3A Event Trigger and 3C Event Trigger ................................ 65 Figure 5-2 TRI358 Site Location ......................................................................................... 66 Figure 5-3 Relative Location of TRI119W and TRI191 ........................................................ 68 Figure 5-4 Success Rate of Handover after Deleting 2G Neighbor Cells ............................ 68 Figure 5-5 Relocation Failure.............................................................................................. 70 Figure 5-6 Signaling Flowchart of Inter-RAT Handover ....................................................... 70 Figure 5-7 Inter-RAT Handover .......................................................................................... 71 Figure 5-8 Failure Signaling of Security Mode .................................................................... 72 Figure 5-9 Value of Failure Reason .................................................................................... 72 Figure 5-10 Encryption Algorithm for PS Service ................................................................ 72 Figure 5-11 Encryption Algorithm for CS Service ................................................................ 72 Figure 5-12 Encryption Algorithm ....................................................................................... 73 TABLES Table 2-1 WCDMA Cell Selection Parameters...................................................................... 6 Table 2-2 WCDMA Cell Reselection Parameters .................................................................. 9 ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. VII
  • 9. 2G-3G Interoperation Analysis Guide Internal Use Only▲ Table 2-3 GSM Important Control Parameters of Handover Measurement ......................... 16 Table 3-1 Parameters Provided to 3G by 2G ...................................................................... 33 Table 3-2 Parameters Provided to 2G by 3G ...................................................................... 33 Table 3-3 Key 2G->3G Cell Reselection Parameters .......................................................... 34 Table 3-4 Key 3G->2G Cell Reselection Parameters .......................................................... 34 Table 3-5 Qqualmin Description ......................................................................................... 36 Table 3-6 SsearchRAT Description .................................................................................... 37 Table 3-7 QRxLevMin Description ...................................................................................... 38 Table 3-8 QHyst1S Description .......................................................................................... 39 Table 3-9 Qoffset1s,n in SIB11(dB) Description ................................................................. 40 Table 3-10 Qoffset1s,nin SIB12(dB) Description................................................................. 42 Table 3-11 Treselection Description ................................................................................... 43 Table 3-12 Qhyst2s(dB) Description ................................................................................... 44 Table 3-13 Qoffset2s,n in SIB11(dB) Description................................................................ 45 Table 3-14 Qoffset2s,n in SIB12(dB) Description................................................................ 46 Table 3-15 Recommended Values of Key 3G ->2G Reselection Parameters ..................... 47 Table 3-16 Key 2G ->3G Reselection Parameters .............................................................. 47 Table 3-17 2D/2F Event Configured Threshold ................................................................... 48 Table 3-18 3A/3C Threshold Parameter ............................................................................. 50 Table 3-19 Hysteresis(Rat) Parameter Description ............................................................. 51 Table 3-20 3G->2G Parameters List ................................................................................... 53 Table 4-1 Optimization Methods of Typical Scenarios ........................................................ 55 Table 4-2 Inter-RAT Handover Failure ................................................................................ 57 Table 5-1 3C Handover Trigger Parameters for the Whole Network and Sites Distribution of 3A Handover Trigger Parameters ......................................................................................... 64 ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. VIII
  • 10. 2G-3G Interoperation Analysis Guide 1 Internal Use Only▲ Preface The low-speed data services of 2G voice, short message and circuit field have been widely used in every corner of the world, in order to meet the new requirements for the human communications better. Symbolized by high-speed data services, video telephone, and a variety of online services, 3G communications have been pushed to the front. In the current 3G and 2G development, 3G WCDMA and 2G GSM/GPRS are most widely used; therefore, in the evolution from GSM/GPRS to WCDMA, the coexistence and complementarity between the two parties are considered as a very important factor for the seamless connection between 3G and 2G. Generally speaking, 3G networks are not easy to be constructed, and it takes some time to achieve better coverage and capacity. In the early stage of 3G network construction, they cannot reach the scale as big as 2G due to the limited coverage. How 3G can provide seamless services by using 2G, and how 2G can provide the newest services by using 2G are urgent and actual problems. The better coexistence between 3G and 2G depends on the seamless connection between 3G and 2G, which makes users experience continuous and omnipresent services. The seamless connection here means the interoperability between 3G and 2G, including reselection and handover between 3G and 2G. This article first describes the principles and policies of 2G/3G interoperability, and then it makes an analysis on the key parameters involved in the interoperability. According to the baseline of the ZXWR RNC radio parameters in the WCDMA network of China Unicom, it also provides the recommended values of the main related parameters for the 2G/3G interoperability, which is a reference for commercial configuration in each field. Finally it makes a detailed analysis on the various solutions to the problems of the 2G/3G interoperability, and provides some cases for analysis. Note: Taking into account the complexity of the actual radio environment, the final values of the parameters in different fields should be adjusted reasonably based on the actual radio environment. It should not ignore the flexibility of network optimization and only comply with the recommendations in this article completely. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 1
  • 11. 2G-3G Interoperation Analysis Guide Internal Use Only▲ 2 Introduction to 2G/3G Interoperability 2.1 Network Elements Structure for 2G/3G Interoperability Figure 2-1 Network Elements Structure for 2G/3G Interoperability ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 2
  • 12. 2G-3G Interoperation Analysis Guide 2.2 PLMN Selection and Reselection 2.2.1 Internal Use Only▲ Process Description When a UE powers up or roams, its primary task is to find the network and contact with it, in order to obtain the network service. The UE behaviors in the idle mode can be divided into PLMN selection and reselection, cell selection and reselection, and location registration. The relationship among the three processes is as follows. Figure 2-2 Idle Mode Process Description Automatic/ Manual selection User selection of PLMN PLMN Selection and Reselection Indication to user Location Registration response PLMNs available PLMN selected NAS Control Cell Selection and Reselection Radio measurements Registration area changes CM requests Location Registration After the UE powers up, firstly it should select one PLMN. After one PLMN is selected, it starts to select one cell which belongs to the PLMN. After the cell is founded, it can get the information of the neighbor cells from system information broadcast, thus the UE can choose one cell with the best signal to reside from all the cells. Then the UE initiates the process of location registration, after success, the UE resides in the cell successfully. There are four functions for cell residence:  UE can receive the system information broadcasted by PLMN.  It can initiate random access process within the cell.  It can receive network paging.  It can receive the broadcast service from the cell. After the UE resides in the cell and registers successfully, as it moves, the signal strength of the current cell and the neighbor cell is changing constantly. The UE needs to choose ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 3
  • 13. 2G-3G Interoperation Analysis Guide Internal Use Only▲ the most suitable cell, which is just the cell reselection process. There are some rules for the cell reselection, and it will be described later. After the UE reselects the cell and another cell is selected, it finds that this cell belongs to another LA or RA, the UE needs to initiate the location update process, so that the network can get the latest MS location information. The system information SIB1 includes CN common GSM-MAP NAS system information and PS domain system information, in which LAC and RAC information exists, so the UE can know whether LA or RA changes. If location registration or update is not successful (for example, when the network refuses the MS), or the UE leaves the current PLMN coverage area, the UE can reselect the PLMN and select another available PLMN. The purpose of PLMN selection/reselection is to select an available PLMN. To achieve this purpose, the UE will maintain a PLMN list, in which PLMN is ordered by priority, and then is searched from the high priority to find one PLMN with the highest priority. Additionally, there are two modes for the PLMN selection and reselection: auto and manual. The auto selection is that UE selects one PLMN automatically according to the PLMN priority, the manual selection is to show all the available networks for the user, and ask the user to choose one PLMN. In the list, RPLMN (Registered PLMN) has the highest priority. The RPLMN is the PLMN which registered successfully last time. There are two files in the USIM card, EFLOCI and EFLOCI, which record the RPLMN information. In these two files, LAI (=MCC+MNC+LAC) and RAI (=LAI+RAC) include MCC and MNC, which are just RPLMN. No matter auto or manual selection, after the UE powers up, firstly it will try to select RPLMN; if it is successful, there will be no subsequent operation. If not, the UE will generate a PLMN list (ordered by priority): HPLMN  The PLMN in the USIM file ―User Controlled PLMN Selector with Access Technology‖.  The PLMN in the USIM file ―Operator Controlled PLMN Selector with Access Technology‖.  PLMN with better signal quality (random order).  Other PLMN (order from high to low signal quality). In the USIM card, the file EFIMSI records IMSI (MCC + MNC + MSIN), from which the UE can get HPLMN. 2) and 3) are the files EFPLMNwAcT and EFOPLMNwACT in the USIM. 4) and 5) are obtained through searching the frequency one by one by the UE. The UE searches the PLMN one by one according to the PLMN list ordered by the priority above, and attempts the location registration. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 4
  • 14. 2G-3G Interoperation Analysis Guide Internal Use Only▲ UMTS is evaluated from GSM and both access technologies are different completely (GERAN vs. UTRAN), so it needs to specify the preferred access technology for each PLMN. The priority of the access technologies is specified in the file ―...with Access Technology‖. If it is not specified, generally, GERAN is preferred. In addition, PLMN needs to be reselected for the following two cases:  In any case, the user can request to initiate PLMN reselection manually.  VPLMN (visited PLMN) reselection: After the user registers to VPLMN for the reason of handover/roaming, as the MCC is the same between VPLMN and HPLMN (home PLMN), only MNC is different from each other, and this case can be judged by the UE. For this case, the UE will return to the home network as much as possible. The method is to search the home network periodically. This period is specified by USIM and defined in the file EFHPLMN, from 6 minutes to 8 hours. The operator can also forbid this function, in this way the value is set to 0 in the file EFHPLMN. Note: HPLMN is the registration handover and HLR information, and it is defined as follows in the protocol: The HPLMN is the GSM network that a GSM user is a subscriber of. That implies that GSM user‘s subscription data resides in the HLR in that PLMN. The HLR may transfer the subscription data to a VLR (during registration in a PLMN) or a GMSC (during mobile terminating call handling). The HPLMN may also contain various service nodes, such as a short message service centre (SMSC), service control point (SCP), etc. VPLMN is the roaming handover information, and it is defined as follows in the protocol: The VPLMN is the GSM network where a subscriber is currently registered. The subscriber may be registered in her HPLMN or in another PLMN. In the latter case, the subscriber is outbound roaming (from HPLMN‘s perspective) and inbounds roaming (from VPLMN‘s perspective). When the subscriber is currently registered in her HPLMN, then the HPLMN is at the same time VPLMN. 2.2.2 Application Analysis for PLMN Selection and Reselection By using the functions of PLMN selection and reselection, the inter-RAT selection and roaming functions can be implemented without any upgrading for the GSM and WCDMA networks. The user can return to the WCDMA network from the GSM network by PLMN reselection. For the WCDMA user can handover to the WCDMA network from the GSM network when entering the coverage area of WCDMA, you can set different PLMNs for the WCDMA and GSM networks and set HPLMN for the WCDMA network in the USIM. And the selection time can be controlled by the operator. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 5
  • 15. 2G-3G Interoperation Analysis Guide 2.3 Cell Selection and Reselection 2.3.1 Internal Use Only▲ Process Description for Cell Selection Cell selection process includes cell searching and reading broadcast channel.  Cell searching Firstly, if a UE has stored some relevant information of this PLMN, such as frequency, scrambling code, etc, the UE will use this information to search the cell (stored information cell selection) and find the network quickly. The information is stored in the USIM card or in the non-volatile memory of the cell phone. The purpose of cell searching is to find a cell, and the steps are as follows: Time slot synchronization by the synchronization code of PSCH. Frame synchronization, implemented by the synchronization code of SSCH, and the scrambling code group of the cell is confirmed. Obtaining the main scrambling code of the cell through CPICH, and then the UE can read the broadcast channel. Obviously, if the UE has already known some information of this cell, such as frequency and main scrambling code, the steps mentioned above can be speeded up.  Reading broadcast channel Main information block MIB‘s dispatching information is already known, that is SIB_POS = 0, SIB_REP = 8. The UE can read out the MIB in the radio frame of SFN = 0, 8, 16 ... After reading out the MIB, the UE can judge whether the founded PLMN is the one expected by the field PLMN identity in the MIB. If yes, according to the other SIB‘s dispatching information in the MIB, the UE can the find the other SIB and obtain its content. If not, the UE needs to find the next frequency and start the process again from the cell searching. If the current PLMN is the one that the UE is looking for, the UE reads SIB3 and obtains ―Cell selection and re-selection info‖, in this IE, it reads out Qqualmin, Qrxlevmin, and Maximum allowed UL TX power (UE_TXPWR_MAX_RACH), it calculates according to the formula below: Table 2-1 WCDMA Cell Selection Parameters Parameter ZTE Confidential Proprietary Description © 2014 ZTE CORPORATION. All rights reserved. 6
  • 16. 2G-3G Interoperation Analysis Guide Parameter Internal Use Only▲ Description Squal Cell Selection quality value, (dB) Not applicable for TDD cells or GSM cells. Srxlev Cell Selection RX level value (dB) Qqualmeas Measured cell quality value. The quality of the received signal expressed in CPICH Ec/No (dB) for FDD cells. Not applicable for TDD cells or GSM cells. Qrxlevmeas Measured cell RX level value. This is received signal, CPICH RSCP for FDD cells (dBm), P-CCPCH RSCP for TDD cells (dBm) and RXLEV for GSM cells (dBm). Qqualmin Minimum required quality level in the cell (dB). Not applicable for TDD cells or GSM cells. (read in system information) Qrxlevmin Minimum required RX level in the cell (dBm). (read in system information) Pcompensation Max(UE_TXPWR_MAX_RACH - P_MAX, 0) (dB) UE_TXPWR_MAX_RACH Maximum TX power level a UE may use when accessing the cell on RACH (read in system information), (dBm) P_MAX Maximum RF output power of the UE, (dBm) If Then the UE considers this cell as a suitable cell, it resides and reads the other system information as needed, then the UE initiates the location registration process. If the criteria above is not satisfied, the UE reads the SIB11 to obtain the main scrambling code and the frequency of the neighbor cell, it can measure the Qqualmeas and Qrxlevmeas of the neighbor cell, in the IE ―Cell Selection and Re-selection info for SIB11/12‖, the UE can know the neighbor cell‘s Maximum allowed UL TX power, Qqualmin and Qrxlevmin, thus the UE can calculate the neighbor cell‘s Squal and Srxlev, and judge whether the neighbor cell satisfies the criteria above. If the UE can find any neighbor cell that satisfy the selection criteria, it will reside in the cell and read the other system information as needed, then initiate the process of location registration. If the UE cannot find a cell that satisfies the selection criteria, the UE will consider that it is not covered and continue to select and reselect PLMN. 2.3.2 Scenario of Inter-RAT Cell Reselection The 2G/3G inter-RAT cell reselection mainly occurs in the following two modes.  Idle Mode ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 7
  • 17. 2G-3G Interoperation Analysis Guide Internal Use Only▲ A UE performs the inter-RAT cell reselection in the idle states of WCDMA, GSM and GPRS. The UE measures the serving cell according to the parameters of network broadcast and determines whether to reselect another cell.  Connected Mode A UE performs the inter-RAT cell reselection in the group connected states of Cell_FACH and Cell_PCH/URA_PCH. Figure 2-3 2.3.3 Scenario of 2G/3G Inter-RAT Cell Reselection for UE Policy of Inter-RAT Cell Reselection The current policy of inter-RAT cell reselection for the 2G/3G interoperability is a bidirectional reselection between 2G and 3G. However, it performs the cell reselection from 3G to 2G only when a UE moves out the scale of 3G coverage. And once it returns to the scale of 3G coverage, the UE will initiate the cell reselection from 2G to 3G. 2.3.4 Reselection from 3G to 2G 1. Planning for the cell reselection measurement When a UE is in the idle mode, it needs to monitor the signal quality of the current and neighbor cells at any moment for selecting the best cell to provide service, this is called cell reselection. In the following rules, the UE uses Squal for FDD cells and Srxlev for TDD for Sx. i. If Sx > Sintrasearch, the UE does not perform co-frequency measurement; if Sx < Sintrasearch, the UE performs co-frequency measurement. If the current cell does not send Sintrasearch to the UE, the UE performs co-frequency measurement. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 8
  • 18. 2G-3G Interoperation Analysis Guide Internal Use Only▲ ii. If Sx > Sintersearch, the UE does not perform inter-frequency measurement; if Sx < Sintersearch, the UE performs inter-frequency measurement. If the current cell does not send Sintersearch to the UE, the UE performs inter-frequency measurement. iii. If Sx > SsearchRATn, the UE does not perform system measurement; if Sx < SsearchRATn, the UE performs inter-RAT measurement. If the current cell does not send SsearchRATn to the UE, the UE performs inter-RAT system measurement. Sintrasearch, Sintersearch and SsearchRATn are specified in the SIB3‘s ―Cell selection and re-selection info‖. The UE measures the neighbor cells which satisfy the conditions mentioned above, firstly it calculates the S values for all the cells (including the current and neighbor cells) according to the cell selection method, for the all the cells which meet the condition S>0, calculate the R according to the formulas below. Rs = Qmeas,s + Qhysts Rn = Qmeas,n - Qoffsets,n Rs: the R value of the serving cell Rn: the R value of the neighbor cell Qmeas: the signal measurement value of a cell, it adopts CPICH Ec/No or CPICH RSCP for the FDD cell Qoffset1s,n: the offset between two cells, it is used for the FDD cell when the measurements of the cell selection and reselection are set to be CPICH RSCP. Qoffset2s,n: the offset between two cells, it is used for the FDD cell when the measurements of the cell selection and reselection are set to be CPICH Ec/No. Qhyst1s: the hysteresis value, it is used for the FDD cell when the measurements of the cell selection and reselection are set to be CPICH RSCP. Qhyst2s: it is used for the FDD cell when the measurements of the cell selection and reselection are set to be CPICH Ec/No. Treselection: the timer value for the cell reselection Table 2-2 WCDMA Cell Reselection Parameters Parameter Description Cell_selection_and_reselection_quality_ measure (FDD only) Choice of measurement (CPICH Ec/N0 or CPICH RSCP) that is used to derive ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 9
  • 19. 2G-3G Interoperation Analysis Guide Parameter Internal Use Only▲ Description quality measures Qmap,n and Qmap,s, (read in system information). Qmeas,s Quality of the serving cell, derived from CPICH Ec/N0 or CPICH RSCP for FDD cells, from RXLEV for GSM cells. For FDD cells, the measurement that is used to derive the quality value is set by the Cell_selection_and_reselection_quality_ measure information element. Qmeas,n Quality of the neighboring cell, derived from CPICH Ec/N0 or CPICH RSCP for FDD cells, from RXLEV for GSM cells. For FDD cells, the measurement that is used to derive the quality value is set by the Cell_selection_and_reselection_quality_ measure information element. Qoffset1s,n Offset value 1between the two cells considered in the evaluation (read in system information). Qoffset2s,n, Offset value 2 between the two cells considered in the evaluation (read in system information). Qhyst1s Hysteresis value of the serving cell. Qhyst2s Hysteresis value of the serving cell. Treselections Time-to-trigger for cell reselection, (s) 2. General process of reselection A: When ―the pilot Ec/No of the WCDMA serving cell‖ is smaller than ―Qqualmin+SsearchRAT‖, the UE starts to measure the signal strength of the neighbor GSM/GPRS cells. The SsearchRAT parameter is broadcasted in SIB3/4. A -> B: The UE starts to rank the signal strength of WCDMA serving cells and GSM/GPRS neighbor cells. Rank of serving WCDMA = RSCP_WCDMA + QHyst1s Rank of neighbor GSM/GPRSn = RSSIGSMn - Qoffset1s,n B: When a GSM cell ranks the top, the Treselection timer is started. C: When a GSM cell ranks the top and it keeps for Treselection seconds, the UE reselects to the corresponding GSM cell as shown in the following figure. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 10
  • 20. 2G-3G Interoperation Analysis Guide Figure 2-4 3. Internal Use Only▲ General Process of Reselection from 3G to 2G Reselection process for special cell When the signal strength of WCDMA is too weak to maintain a normal network service, the process of cell reselection is as follows. A: The WCDMA serving cell cannot maintain a normal network service (pilot Ec/No > Qqualmin, but pilot RSCP < Qrxlevmin) A -> B: The WCDMA serving cell cannot maintain a normal network service, and it lasts for a period of ―Nserv DRX Cycles‖. B: UE measures and ranks all the neighbor cells in the neighbor cell list. It starts a timer when a GSM cell ranks the top. Rank of WCDMA = RSCP_WCDMA + QHyst1s Rank of neighbor GSM/GPRSn = RSSIGSMn - Qoffset1s,n C: When a GSM cell ranks the top and it lasts for Treselection seconds, the UE reselects to the corresponding GSM cell as shown in the following figure. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 11
  • 21. 2G-3G Interoperation Analysis Guide Internal Use Only▲ Figure 2-5 Reselection Process for the Case that WCDMA Signal Strength is too Weak to Maintain Normal Network Service 2.3.5 Reselection from 2G to 3G In the idle state, inter-RAT selection can be implemented by cell selection and reselection. Additionally, the standards for the signal quality in the two GU systems are different, so the parameters setting for the selection and reselection needs to be very cautious, or it may occur inappropriate cell selection or ping-pong selection. 2.4 Inter-RAT Handover 2.4.1 Inter-RAT Handover Scenario The handover between WCDMA and GSM/GPRS occurs in the Cell_DCH state of the connected mode, and an effective handover between WCDMA and GSM/GPRS can ensure that the users can use the current service continuously. The typical process of inter-RAT handover: once UE is in the connection state (the CELL_DCH state in WCDMA), it performs the ―measurement‖ instruction from network, and reports the result to the network by period or event, the network judges the UE signal quality based on the reported result, and determines whether the cell phone to handover. 2.4.2 Inter-RAT Handover Strategies 2.4.2.1 Inter-RAT Handover Strategies for Different Stages 1. Coverage Handover ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 12
  • 22. 2G-3G Interoperation Analysis Guide Internal Use Only▲ In the initial stage of 3G construction, given the network condition of continuous GSM coverage and limited 3G coverage, it adopts the handover based on coverage for the places with poor coverage. 2. Load Handover In the middle and late stages of 3G construction, 3G network extends very fast, 3G and 2G networks overlap basically, 2G network needs to share load for 3G network, it adopts load handover that is based on the load of 3G network. 3. Service Handover In the middle and late stages of 3G construction, the RNC of 3G network receives RAB assignment message, the services should be handed over to 2G according to the requirement from core network, thus 3G users are handed over to 2G network, and it is called service handover. 2.4.2.2 Current Inter-RAT Handover Strategy At present, given the network condition of continuous GSM coverage and limited 3G coverage, it adopts the handover based on coverage for the places with poor coverage. The specific handover strategy is as follows: it is a one-way handover from 3G to 2G for CS, and it is a two-way handover from 3G to 2G for PS. So the handover process from 2G to 3G for CS will not be described in this article. 2.4.3 Measurements and Decisions before Inter-RAT Handover The typical process of inter-RAT handover: once UE is in the connection state (the CELL_DCH state in WCDMA), it performs the ―measurement‖ instruction from network, and reports the result to the network by period or event, the network judges the UE signal quality based on the reported result, and determines whether the cell phone to handover. The inter-RAT measurement processes in WCDMA and GSM are introduced below. 2.4.3.1 Start Measurement to GSM in WCDMA The process of starting measurement to GSM: When a UE finds that the value of carrier evaluation quality in the current system is lower than the assigned threshold in the measurement control, it reports a 2D event to the network. The WCDMA system requests the UE to start the compact mode, and the UE starts to measure the inter-RAT signal quality (if the UE finds that the value of carrier evaluation quality in the current system is higher than the assigned threshold in the measurement control, it stops the compact mode and inter-RAT measurement). When it satisfies the condition of 3A (or 3C) event trigger threshold, the UE reports the 3A (or 3C) event to the network. And the network triggers the inter-RAT handover command according to the information of measurement report and GSM neighbor cell in order to that the UE can switches to the destination cell. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 13
  • 23. 2G-3G Interoperation Analysis Guide Internal Use Only▲ Note: The UE also can report the signal quality periodically and the network determines whether the trigger condition of 3A (or 3C) is satisfied. The related process is as follows. Figure 2-6 2.4.3.2 Handover from WCDMA to GSM in CS Domain Start Measurement to WCDMA in GSM The process of starting measurement to WCDMA: When a UE enters a GSM cell with 3G neighbor cells, the information of 3G neighbor cells and 3G measurement parameters are included in the ―measurement information‖ instruction from the network, which requires the UE to measure the assigned 3G neighbor cells and report the result. Thus whether to perform an inter-RAT handover is determined by the 2G network. The related process is as follows. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 14
  • 24. 2G-3G Interoperation Analysis Guide Figure 2-7 2.4.3.3 Internal Use Only▲ Handover from GSM to WCDMA in CS Domain Handover Measurement Parameter Setting – Preferred 3G 1. GSM Parameter Setting The main 3G parameters in ―Measurement Information‖ include ―3G Neighbour Cell Description‖ and ―3G MEASUREMENT PARAMETERS Description‖. The information of 3G neighbor cells is defined in the first parameter, and the informaiton of 3G measurement parameters setting is defined in the second parameter. In some foreign PLMNs, there is no information of 3G measurement parameters, which means that it will read the Qsearch_C_Initial parameter broadcasted on BCCH, and the handover measurement is carried out through the definition of the parameter. Other main parameters are in the SYSTEM_INFORMATION_2QUATER. Qsearch_C is set to 7, which shows an unconditional inter-RAT measurement. It is same to the Qsearch_I in the inter-RAT reselection parameters. REPORT_TYPE shows the type of measurement report, generally it is the enhanced ―Extended Measurement Report‖, but the default value is Common Measurement Report. 3G_SEARCH_PRIO shows that it can scan on the frame that is generally used for BSIC decoding, because the 3G neighbor cells do not need BSIC decoding (If indicated by the parameter 3G_SEARCH_PRIO, the UE may use up to 25 search frames per 13 seconds without considering the need for BSIC decoding in these frames). The default value is TRUE. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 15
  • 25. 2G-3G Interoperation Analysis Guide Internal Use Only▲ FDD_REP_QUANT shows the reported type, RSCP or Ec/No. Table 2-3 GSM Important Control Parameters of Handover Measurement Parameter name Description Range Bits Message Qsearch_C_Initial Indicates the Qsearch value to be used in connected mode before Qsearch_C is received, 0 = use Qsearch_I, 1 = (always). Default value = use Qsearch_I. 0/1 1 BCCH D/L Qsearch_C Same to Qsearch_I 0-15 4 SACCH D/L REPORT_TYPE Indicates which report type the UE shall use, 0 = enhanced, 1 = normal Default value = normal 0/1 1 BCCH D/L SACCH D/L 3G_SEARCH_PRIO Indicates if 3G cells may be searched when BSIC decoding is required, 0 = no, 1 = yes Default value = yes 0/1 1 SACCH D/L 1 PBCCH D/L PCCCH D/L PACCH D/L (**) FDD_REP_QUANT 2. Indicates the reporting quantity for UTRAN FDD cells, 0 = RSCP, 1 = Ec/No 0/1 GSM Signal Measurement The measurement to a GSM cell can be divided into two modes: ―BSIC check‖ and ―no BSIC check‖. It only needs to measure ―GSM carrier RSSI‖ for the ―no BSIC check‖ mode. For the ―BSIC check‖ mode, the two processes of ―Initial BSIC identification‖ and ―BSIC re-confirmation‖ are also needed. Initial BSIC identification: the process of BSIC searching and decoding BSIC re-confirmation: the tracing and decoding processes to the BSIC of a GSM cell after the ―Initial BSIC identification‖ If the measurement to a GSM cell is ―BSIC check‖, the UE behaviors are as follows: The UE performs the ―GSM carrier RSSI‖ measurement according to the TGPS setting with a target of ―GSM carrier RSSI measurements‖. The UE performs the initial BSIC identification according to the TGPS setting with a target of ―GSM Initial BSIC identification‖. If there are multiple GSM cells, ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 16
  • 26. 2G-3G Interoperation Analysis Guide Internal Use Only▲ it will perform the process according to the order of signal strength in the recent GSM carrier RSSI measurement. The UE performs the BSIC reconfirmation according to the TGPS setting with a target of ―GSM BSIC re-confirmation‖. Judging the ―BSIC check‖: The UE decodes the SCH on BCCH and identifies the BSIC for at least one time, after that, the BSIC is confirmed again for each Tre-confirm_abort seconds, then the BSIC of GSM cell is considered to be ―checked‖. Otherwise it is considered to be ―unchecked‖. Accepting or discarding the ―BSIC check‖: There may be multiple cells with the same ARFCN but different BSICs among the GSM cells in WCDMA. For the measurements without the ―BSIC check‖, which means that the BSIC is not judged, the network cannot distinguish which GSM cell each measurement belongs to, and the handover may fail as the destination is not clear. Therefore it must adopt the ―BSIC check‖. 2.4.4 Inter-RAT Handover Processes 2.4.4.1 Handover From 3G to 2G in CS Domain In the initial stage of 3G construction, in order to keep the continuity of service in the edge of 3G coverage, it is necessary to support the handover from WCDMA to GSM. 1. Intra-MSC Figure 2-8 Signaling Process of Inter-RAT Handover in MSC: WCDMA->GSM UE/MS UE/MS RNS-A 3G_MSC-A BSS-B Relocation-Required[1] HO-Request[2] HO-Request-Ack[3] Relocation-Command[4] RRC-HO-Command RI-HO-Access HO-Detect[5] RI-HO-Complete HO-Complete[6] Iu-Release-Command[7] Iu-Release-Complete[8] ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 17
  • 27. 2G-3G Interoperation Analysis Guide Internal Use Only▲ RNS-A is the RNS where the cell phone locates before handover; BSS-B is the BSS where the cell phone locates after handover. All the messages above can be tracked in the user interface, Iu interface, and A interface. RI is Radio Interface. RRC is Radio Resource Control. 3G_MSC-A is the MSC where the cell phone locates before handover. i. RNS-A sends the RELOCATION_REQUIRED message to 3G_MSC-A. The available cell list and handover reason are included in this message. 3G_MSC-A choose one cell in the list as the destination cell. 3G_MSC-A queries the location of the destination cell according to the destination cell number, and determines the handover is intra-office or interoffice. ii. 3G_MSC-A sends the HO_REQUEST message to BSS-B. After receiving the handover request, 3G_MSC-A queries in the corresponding tables and finds that the destination cell is the cell controlled by its subordinated BSS. Then 3G_MSC-A constructs the corresponding GSM handover request message according to the handover request, and sends the message to BSS-B. When constructing the request message, 3G_MSC-A needs to complete the interworking between UMTS and GSM handover request messages. Then 3G_MSC-A can send the HO_REQUEST message to BSC-B. iii. BSS-B sends the HO_REQUEST_ACK message to 3G_MSC-A. After BSS-B applies the radio resource and gets the circuit ready, it sends this message to 3G_MSC-A, the HANDOVER_COMMAND message is included in this message and will be transmitted transparently by RNS-A to the handover request side, which is called RNS-A. iv. 3G_MSC-A sends the RELOCATION_COMMAND message to RNS-A. After MSC-A receives the HO_REQUEST_ACK message from BSS-B, it means that the radio resource of new interface A is ready and the cell phone can hand over to BSS-B from RNS-A, at this time it sends handover command message to notify the cell phone to hand over. v. BSS-B sends the HO_DETECT message to 3G_MSC-A. At this time the cell phone has already detected the new channel and has the condition to access the new radio channel, but actually has not accessed yet. As it is voice handover, the voice channel must be built up, so 3G_MSC-A connects the time slot of the opposite end to time slot of new interface, and continues to call by using the resource applied in the process of handover. vi. BSS-B sends the HO_COMPLETE message to 3G_MSC-A. The new channel has been built up, the user continues to call or be in the process of other services. BSS-B reports the handover completion message to 3G_MSC-A. vii. 3G_MSC-A sends the LU RELEASE_COMMAND message to RNS-A. After the handover is completed, 3G_MSC-A sends RRC HO Command message to the source RNS-A, and releases the original radio resource. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 18
  • 28. 2G-3G Interoperation Analysis Guide Internal Use Only▲ viii. RNS-A sends the LU RELEASE COMPLETE message to 3G_MSC-A. RNS-A releases the radio resource. 2. Inter-MSC For the inter-RAT handover, if a UE only has the circuit domain service, it follows the handover process of the circuit domain from WCDMA to GSM. The typical handover process includes: measurement control -> measurement report -> handover judge->handover execute. In the stage of measurement control, the network tells UE the measurement parameters by sending measurement control message. In the stage of measurement report, the UE sends measurement report to the network. In the stage of handover judge, the network determines to handover according to the measurement report. In the stage of handover execute, the UE and the network follow the signaling process, and take actions according to the signaling. For the handover from WCDMA to GSM, when the user is in the edge of WCDMA system and needs to handover between systems, WCDMA RNC notices the UE to start an inter-RAT measurement. The UE carries out the inter-RAT measurement and reports the result, RNC determines whether to execute the signaling process for inter-RAT handover according to the result. As the access mode of WCDMA is code division multiple access, all the connected UEs work under the specified frequency for all time, in order to continue to call in the process of inter-RAT measurement, WCDMA system and the UE may need to start the compression mode (if the UE only has one transceiver, it must start the compression mode; if the UE has two transceivers, the UE can test GSM cell without starting the compression mode). The signaling process of handover from WCDMA to GSM is as follows. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 19
  • 29. 2G-3G Interoperation Analysis Guide Figure 2-9 Internal Use Only▲ Signaling Process of Handover from WCDMA to GSM UE Node B RNC Serving RANAP CN 1. Relocation Required MSC BSC BTS RANAP MAP/E 2. Prepare Handover MAP/E BSSMAP 3. Handover Request BSSMAP 4. Handover Request Ack BSSMAP MAP/E 5. Prepare Handover Response BSSMAP MAP/E 6. Relocation Command RANAP RANAP 7. DCCH : Inter-System Handover Command RRC RRC [Hard Handover] 8. Handover Detect BSSMAP BSSMAP 9. Handover Complete RR RR 10. Handover Complete BSSMAP MAP/E RANAP 12. Iu Release Command 11. Send End Signal Request BSSMAP MAP/E RANAP 13. Iu Release Complete RANAP RANAP 14. Send End Signal Response MAP/E MAP/E i. When URRAN determines to handover between systems based on the measurement, SRNC sends RANAP message RELOCATION REQUIRED to CN, and requests the other system to prepare for the handover. ii. WCDMA CN forwards this request to GSM UEC (through MAP/E message PREPARE HANDOVER). iii. GSM UEC sends the HANDOVER REQUEST message to BSC. iv. After GSM BSS gets the resource ready for the handover between systems, BSC replies the HANDOVER REQUEST ACK message to GSM UEC. v. GSM UEC sends MAP/E message PREPARE HANDOVER RESPONSE to WCDMA CN. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 20
  • 30. 2G-3G Interoperation Analysis Guide Internal Use Only▲ vi. WCDMA CN answers the initial request from SRNC through sending RANAP message RELOCATION COMMAND. vii. SRNC sends the message HANDOVER FROM UTRAN COMMAND to UE through the existing RRC connection, and requests UE to handover from WCDMA to GSM. viii. UE hands over from WCDMA to GSM (hard handover), UE sends the message HANDOVER COMPLETE to BSC, notices BSC that the handover is completed, BSC sends the message HANDOVER COMPLETE to GSM UEC. ix. Combined with Step viii. x. Combined with Step viii. xi. When detecting that UE is in the area covered by GSM, GSM UEC sends the message SEND END SIGNAL REQUEST to WCDMA CN and notices WCDMA CN that the handover is completed, and the WCDMA resource occupied by this UE can be freed. xii. CN sends LU RELEASE COMMAND to RNC and notifies the original SRNC to free the resource. When the relevant resource in WCDMA is completed to free, WCDMA responses to GSM UEC and then the handover process is finished. xiii. Combined with Step xii. xiv. Combined with Step xii. 2.4.4.2 Handover From 3G to 2G in PS Domain Group domain handover from 3G to 2.5G is supported, and GSM BSS does not need to change. The version of GTP is negotiated between GSM SGSN and WCDMA SGSN by using the standard program. The backward compatibility of GTP protocol can assure the compatibility of GSM/WCDMA. The destination GSM SGSN will contact with the source WCDMA SGSN. If both the source and destination SGSNs support 3GPP R99, it adopts GTP v1; if GSM SGSN does not support 3GPP R99, it adopts GTP v0. In this case, some services may be degraded. The destination GSM SGSN will degrade the PDP contexts (such as Real time PDP contexts) which cannot be processed. If HLR does not support the version of 3GPP R99 MAP either, the version of MAP infoRetrievalContext will be rollback to v2. If it is WCDMA user, the HLR where it locates must support MAP v3. 1. Intra-SGSN ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 21
  • 31. 2G-3G Interoperation Analysis Guide Internal Use Only▲ It occurs when a UE radio interface hands over from UTRAN interface to GSM interface, UTRAN interface and GSM interface are connected to one SGSN. Figure 2-10 Inter-RAT Handover in SGSN From UTUE To GSM (Group Domain) BSS UE/MS SRNS 2G+3G-SGSN new MSC/VLR HLR old MSC/VLR 1. Intersystem change decision 2. Routeing Area Update Request 3. SRNS Context Request 4. SRNS Context Response 5. Security Functions 6. SRNS Data Forward Command 7. Forward Packets 8. Iu Release Command 8. Iu Release Complete 9. Location Update Request 10a. Update Location 10b. Cancel Location 10c. Cancel Location Ack 10d. Insert Subscriber Data 10e. Insert Subscriber Data Ack 10f. Update Location 11. Location Update Accept 12. Routeing Area Update Accept C1 13. Routeing Area Update Complete 14. TMSI Reallocation Complete 15. BSS Packet Flow Context Procedure i. The UE hands over from UTRAN to the cell which supports GSM interface. ii. The UE initiates routing area update request. iii. 2G+3G-SGSN sends the SRNS CONTEXT REQthe UEST (IMSI) message to SRNS, after SRNS receives the request, it begins to stop sending the downlink data and caches, at the same time it notices SGSN the serial number of datagram (GTP-SNDs, GTP-SNUs, PDCP-SNDs, PDCP-SNUs) through the SRNS CONTEXT RESPONSE message. iv. Combined with Step iii. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 22
  • 32. 2G-3G Interoperation Analysis Guide Internal Use Only▲ v. Execute security function (optional). vi. 2G+3G-SGSN sends the SRNS DATA FORWARD COMMAND message to SRNS, and notices SRNS to start to send the cached data back to SGSN, SRNS forwards the cached data. vii. Combined with Step vi. viii. The cached data is completed to forward, 2G+3G-SGSN releases the lu link. ix. If it is joint routing update and attached by IMSI or the location area changes, 2G+3G-SGSN sends the location update message to VLR. x. If the user data in VLR is not confirmed by HLR, the new VLR notices HLR to delete the user data in the old VLR, and inserts users in the new VLR. xi. The new VLR assigns new VLR TMSI and notices SGSN. xii. 2G+3G-SGSN checks whether the user is forbidden to roam, if it is allowed, 2G+3G-SGSN can assign new P-TMSI, and send the ROUTING AREA UPDATE ACCEPT message to notice the UE. xiii. the UE can send the ROUTING AREA UPDATE COMPLETE (Receive N-PDU Number) message to SGSN, and notice SGSN that the serial number of datagram has been received. SGSN continues to forward the datagram that is after this serial number to the UE. xiv. If the UE has accepted VLR Tthe UEI, 2G+3G-SGSN sends the Tthe UEI REALLOCATION COMPLETE message to the new VLR. xv. 2G+3G-SGSN and BSS‗s optional BSS Packet Flow Context flow, build up BSS Packet Flow. If UE is CAMEL user, the following processes will be triggered: i. ii. 2. CAMEL_GPRS_Routeing_Area_Update_Session CAMEL_GPRS_Routeing_Area_Update_Context Inter-SGSN The process of group domain handover between SGSNs from UMTS to GSM is as shown in figure below. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 23
  • 33. 2G-3G Interoperation Analysis Guide Figure 2-11 UE/MS BSS SRNS Internal Use Only▲ Handover between SGSNs From UMTS To GSM (group domain) new 2G -SGSN old 3G -SGSN GGSN new MSC/VLR HLR old MSC/VLR 1. Inter-RAT change decision 2. Routing Area Update Request 3. SGSN Context Request 4. SRNS Context Request 4. SRNS Context Response 5. SGSN Context Response 6. Security Functions 7. SGSN Context Acknowledge C1 8. SRNS Data Forward Command 8a. Forward Packets 9. Forward Packets 10. Update PDP Context Request 10. Update PDP Context Response 11. Update GPRS Location 12. Cancel Location 13. Iu Release Command 13. Iu Release Complete 12. Cancel Location Ack 14. Insert Subscriber Data 14. Insert Subscriber Data Ack 15. Update GPRS Location Ack 16. Location Update Request 17a. Update Location 17b. Cancel Location 17c. Cancel Location Ack 17d. Insert Subscriber Data 17e. Insert Subscriber Data Ack 18. Location Update Accept 17f. Update Location Ack C2 19. Routing Area Update Accept C3 20. Routing Area Update Complete 21. TMSI Reallocation Complete 22. BSS Packet Flow Context Procedure i. The UE (UE is in the non-Cell-DCH state) or UTRAN (the UE is in the state of Cell-DCH or Cell_FACH) determines to initiate the group domain inter-RAT handover, in this way the UE is handed over to another new cell which supports GSM, at the same time the data transmission between the UE and network is stopped. ii. The UE initiates routing area update request to 2G-SGSN, routing area update or joint RA/LA update or joint RA/LA update with IMSI attached will be specified for the update type, before the message is sent to SGSN, BSS will add the CGI with RAC and LAC where it locates to the message received. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 24
  • 34. 2G-3G Interoperation Analysis Guide Internal Use Only▲ iii. The new 2G-SGSN sends the SGSN Context Request message to the old 3G-SGSN for obtaining MM and PDP contexts, the old 3G-SGSN verifies the PTMSI signature of the UE. If it is successful, the old SGSN will start a timer; if the old SGSN does not recognize the UE, it will reply an appropriate error reason. iv. If the UE is in the state of PMM-CONNECTED before handover, the old 3G-SGSN sends SGSN Context Request message to SRNS, after receiving this message, SRNS starts to cache and stops to send data to PDU, and replies SRNS CONTEXT RESPONSE message to the old 3G-SGSN. v. The old 3G-SGSN sends the SGSN CONTEXT RESPONSE message to 2G-SGSN, in which MM and PDP contexts are included. vi. Execute security function. vii. The new 2G-SGSN sends the SGSN CONTEXT ACKNOWLEDGE message to 3G-SGSN, and notices 3G SGSN that the current 2G SGSN can accept the relevant data PPDU of activated PDP context. viii. If the cell phone is in the state of PMM-CONNECTED, the old 3G-SGSN sends data forward command to SRNS. After receiving the command, SRNS starts the data forward timer, SNNS sends the cached data PDU to the old SGSN. ix. The old 3G-SGSN sends GTP PDUs to 2G-SGSN by tunnel mode, the serial number in the head of GTP (obtained from the number of PDCP) does not change. x. The new 2G-SGSN sends the Update PDP CONTEXT REQUEST message to each relevant GGSN. GGSN updates PDP context and returns Update PDP Context Response. xi. The new 2G-SGSN sends the UPDATE GPRS LOCATION message to notice HLR to change SGSN number. xii. HLR sends the CANCEL LOCATION message to notice the old 3G-SGSN to cancel the location. The old 3G SGSN responses by the CANCEL LOCATION ACK message. After the clocking of operation timeout is completed, the old 3G-SGSN deletes MM and PDP Context. xiii. If the UE is in the state of PMM-CONNECTED, 3G-SGSN sends the LU RELEASE COMMAND message to SRNS, after the clocking of data forwarding is completed, SRNS responses by the LU RELEASE COMPLETE message. xiv. HLR sends the INSERT SUBSCRIBER DATA message to the new 2G-SGSN, 2G SGSN inserts subscription data to MM context and PDP context, and responses by the INSERT SUBSCRIBER DATA ACK message. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 25
  • 35. 2G-3G Interoperation Analysis Guide xv. Internal Use Only▲ HLR confirms the modification is completed, and sends the UPDATE GPRS LOCATION message to 2G-SGSN. xvi. If the association is to be built up, the new 2G SGSN sends the LOCATION UPDATE REQUEST message to VLR, and notices the new the UEC/VLR to initiate location update; VLR can create or update association by saving SGSN number. xvii. If the user data mark in the VLR is not confirmed by HLR, VLR will notice HLR. HLR cancels the old VLR and inserts the user data to the new VLR: a) The new VLR sends the UPDATE LOCATION message to HLR. b) HLR cancels the data in the old VLR by sending the CANCEL LOCATION message to the old VLR. c) The old VLR responses by the CANCEL LOCATION message. d) HLR sends the INSERT SUBSCRIBER DATA ACK message to the new VLR. e) The new VLR responses by the INSERT SUBSCRIBER DATA ACK message. f) HLR responses to the new VLR by the UPDATE LOCATION ACK message. xviii. The new VLR assigns TMSI for the UE, and sends the LOCATION UPDATE ACCEPT message to notice 2G-SGSN. xix. The new 2G-SGSN verifies the validity of the UE in the new routing area, if all the checks are successful, 2G SGSN builds up MM context and PDP context, and establishes a logical link between the UE and 2G SGSN through 2G SGSN, 2G SGSN responses the ROUTING AREA UPDATE ACCEPT message to the UE. xx. The UE confirms the new assigned PTMSI by sending the ROUTING AREA UPDATE COMPLETE message, including confirming the data PDU sent to the UE successfully before the routing area update is initiated. xxi. After confirmed by the UE, 2G-SGSN sends the TMSI REALLOCATION COMPLETE message to notice VLR TMSI that the assignment is completed again. xxii. 2G-SGSN and BSS execute BSS Packet Flow Context procedure. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 26
  • 36. 2G-3G Interoperation Analysis Guide 2.4.4.3 Internal Use Only▲ Handover From 2G to 3G in PS Domain 1. Intra-SGSN When a UE radio interface hands over from GSM interface to UTRAN interface, UTRAN interface and GSM interface are connected to one SGSN. Figure 2-12 Inter-RAT Handover From GSM To UMTS in SGSN (Group Domain) UE/MS BSS SRNS 2G+3G-SGSN new MSC/VLR HLR old MSC/VLR 1. Intersystem change decision 2. Routing Area Update Request 3. Security Functions 4. Location Update Request 5a. Update Location 5b. Cancel Location 5c. Cancel Location Ack 5d. Insert Subscriber Data 5e. Insert Subscriber Data 5f. Update Location 6. Location Update Accept 7. Routing Area Update Accept C1 8. Routing Area Update Complete 9. TMSI Reallocation Complete 10. Service Request 11. RAB Assignment Request Set up Radio Resources 11. RAB Assignment Response 12. Packet Transfer Resume 13. Packet Transfer Resume i. The UE hands over from UTRAN to the cell which supports UTRAN interface. ii. The UE initiates routing update request, the 2G+3G-SGSN stops forwarding data to the UE and caches. iii. Execute security function (optional). iv. If it is joint routing update and attached by IMSI or the location area changes, the 2G+3G-SGSN sends the LOCATION UPDATE message to VLR. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 27
  • 37. 2G-3G Interoperation Analysis Guide Internal Use Only▲ v. If the user data in VLR is not confirmed by HLR, the new VLR notices HLR to delete the user data in the old VLR, and inserts users in the new VLR. vi. The new VLR assigns new VLR TUEI and notices the SGSN. vii. The 2G+3G-SGSN checks whether the user is forbidden to roam, if it is allowed, the 2G+3G-SGSN can assign new P-TUEI, and send the ROUTING AREA UPDATE ACCEPT message to notice UE. viii. The UE sends the ROUTING AREA UPDATE COMPLETE message to the SGSN by using the new P-TUEI. ix. If the UE accepts VLR TUEI, 2G+3G-SGSN sends the TUEI REALLOCATION COMPLETE message to the new VLR. x. If the UE needs to send signaling or uplink data, the UE can initiate the service request process. If the 2G+3G-SGSN needs to forward signaling or downlink data, the 2G+3G-SGSN will initiate the paging process. xi. The 2G+3G-SGSN requests SRNS to build radio bearer by RAB assignment. xii. Data forwarding recovers. xiii. Combined with Step xii. If the UE is CAMEL user, the following processes will be triggered: i. ii. 2. CAMEL_GPRS_Routeing_Area_Update_Session CAMEL_GPRS_Routeing_Area_Update_Context. Inter-SGSN The process of group domain handover between SGSNs from GSM to UNTS is as shown in figure below. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 28
  • 38. 2G-3G Interoperation Analysis Guide Figure 2-13 UE/M S Internal Use Only▲ Inter-RAT Handover From GSM To UMTS in SGSN (Group Domain) BS S SRN S ne 3 w -SGS G N 1. Inter-RAT change decision 2.Routing Area Update Request ol d 2 -SGS G N GGS N ne w MSC/VLR HLR ol d MSC/VLR 3. SGSN Context Request 4. SGSN Context Response 5. Security Functions 6. SGSN Context Acknowledge C 1 7. Forward Packets 8. Update PDP Context Request 8. Update PDP Context Response 9. Update GPRS Location 10. Cancel Location 10. Cancel Location 11. Insert Subscriber DataInsert Subscriber 11. Ack Data 12. Update GPRS Ack Location 13. Location Update Request Ack 14a. Update Location 14b. Cancel Location 14b. Cancel Location 14c. Insert Subscriber Data 14d. Insert Subscriber Ack Data Routing Area Update 16. Accept Routing Area Update 17. Complete 19. Service Request Set up Radio Resources ZTE Confidential Proprietary 15. Location Update Accept C 2 14e. Update Location Ack C 3 18. TMSI Reallocation Complete 20. RAB Assignment Request 20. RAB Assignment Response © 2014 ZTE CORPORATION. All rights reserved. 29 Ack
  • 39. 2G-3G Interoperation Analysis Guide Internal Use Only▲ i. The UE or BSS determines to handover between systems for group domain, which makes the UE handover to another new WCDMA cell, at the same time the data transmission is stopped between the UE and the network. ii. The UE sends routing area update request to the new 3G-SGSN. Routing area update or joint RA/LA update or joint RA/LA update with IMSI attached will be specified for the Update Type, before the message is sent to SGSN. Before sending the user message to SGSN, SRNC will add the RAC and LAC routing identifiers of the area where the UE locates. iii. The 3G-SGSN obtains the address of the old 2G-SGSN through the old routing area identifier from the UE, and then sends the SGSN CONTEXT REQUEST message to the old 2G-SGSN, in order to obtain MM context and PDP context of the user. The old 2G-SGSN verifies the P-TMSI signature of the UE, if the P-TMSI signature is valid or 3G-SGSN indicates that the UE has already been authenticated, the 2G-SGSN starts a timer. iv. The old 2G-SGSN responds through the SGSN CONTEXT RESPONSE message, which includes MM Context and PDP Context. v. A security function process is initiated. vi. The 3G-SGSN sends the SGSN CONTEXT ACKNOWLEDGE message to the 2G-SGSN, so the 2G-SGSN knows that the 3G-SGSN can accept the relevant data packet of the activated PDP context. vii. The 2G-SGSN copies and caches N-PDUs, and it starts to send data packet to the 3G-SGSN. Before the timer times out, the extra N-PDUs received from GGSN will be copied and sent to 3G-SGSN. After the timer times out, no N-PDUs will be sent to 3G-SGSN. viii. The 3G-SGSN sends the UPDATE PDP CONTEXT REQUEST message to each GGSN related. Each GGSN updates its PDP context and responses the UPDATE PDP CONTEXT RESPONSE message. ix. The 3G-SGSN notices HLR that the SGSN has changed by sending the UPDATE GPRS LOCATION message. x. The HLR sends the CANCEL LOCATION message to the old 2G-SGSN. After the 2G-SGSN timer times out, the old 2G- SGSN will delete MM context and PDP context. The 2G-SGSN responds by sending the CANCEL LOCATION ACK message. xi. The HLR sends the INSERT SUBSCRIBER DATA message to the 3G-SGSN. The 3G-SGSN builds up MM context and replies the INSERT SUBSCRIBER DATA ACK message to the HLR. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 30
  • 40. 2G-3G Interoperation Analysis Guide xii. Internal Use Only▲ The HLR confirms that the modification is completed, and responds to the 3G-SGSN through the UPDATE GPRS LOCATION message by returning an UPDATE GPRS LOCATION ACK. xiii. If the association is to be built up, and the joint RA/LA update attached by IUEI is specified for Update Type, or the LA changes in the routing area update, the new SGSN will sends the LOCATION UPDATE REQUEST message to the VLR, and notices the new VLR to initiate location update, the VLR creates or updates association by saving SGSN number. xiv. If the user data identifier in the VLR is not confirmed by the HLR, the VLR will notice the HLR. The HLR cancels the old VLR and inserts user data to the new VLR. a) b) The HLR cancels the old data in the VLR by sending the CANCEL LOCATION message to the old VLR. c) The old VLR responds through the CANCEL LOCATION message. d) The HLR sends the INSERT SUBSCRIBER DATA ACK to the new VLR. e) The new VLR responds through the INSERT SUBSCRIBER DATA ACK message. f) xv. The new VLR sends Update Location to the HLR. The HLR responds to the new VLR through the UPDATE LOCATION ACK message. The new VLR assigns a new TUEI and notices the 3G-SGSN through the LOCATION UPDATE ACCEPT message. xvi. The 3G-SGSN verifies the UE in the new routing area, if all the checks are passed, the 3G-SGSN builds up the MM context and PDP context of the user. The 3G-SGSN sends the ROUTING AREA UPDATE ACCEPT message to the UE. xvii. The UE confirms the new assigned PTMSI by sending the ROUTING AREA UPDATE COMPLETE message. xviii. If the confirmation is obtained from the UE, the 3G-SGSN sends the TMSI REALLOCATION COMPLETE message to the new VLR. xix. If the UE has uplink data or signaling, it will send the SERVICE REQUEST message to the SGSN. The requested service will be specified in Service Type (data or signaling) xx. If the UE has sent the service request, the 3G-SGSN sends the RAB ASSIGNMENT REQUEST message to request SRNS to build a radio access ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 31
  • 41. 2G-3G Interoperation Analysis Guide Internal Use Only▲ bearer. The SRNS sends the RADIO BEARER SETUP REQUEST message to the UE. The UE responds through the RADIO BEARER SETUP COMPLETE message. The SRNS sends the RAB ASSIGNMENT RESPONSE message to the SGSN. The SRNS sends N-PDUs to the UE. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 32
  • 42. 2G-3G Interoperation Analysis Guide Internal Use Only▲ 3 2G/3G Interoperability Parameters 3.1 2G/3G Interconnection Parameters 1. Parameters Provided to 3G by 2G The radio parameters provided to 3G by 2G include the country code (MCC), network code (MNC), location area code (LAC), cell ID (CI), network color code (NCC), base station color code (BCC), band indication (900 or 1800) and BCCH. Error! Reference source not found. shows an example of parameters for 2G, and all the parameters are decimal in the example. Table 3-1 Parameters Provided to 3G by 2G MCC MNC 460 2. 2 LAC CI 2 2 NCC 0 BCC 0 Band Indication 900 BCCH 10 Parameters Provided to 2G by 3G The radio parameters provided to 2G by 3G include country code (MCC), network code (MNC), location area code (LAC), RNC ID (RNC ID), cell ID (C_ID), downlink frequency point, primary scrambling code, and frequency bandwidth. Error! Reference source not found. shows an example of parameters for 3G, and all the parameters are decimal in the example. Table 3-2 MCC 460 3.2 Parameters Provided to 2G by 3G MNC 2 LAC 20 RNC ID 1 C_ID Downlink ARFCN Primary Scrambling Code Frequency Bandwidth 1501 10687 126 5 Typical Selection and Reselection Parameters The reselection parameters from WCDMA to GSM/GPRS are delivered in the SIB3 and SIB11 WCDMA messages. The content of the current cell is delivered in the SIB3 message, and the content of the neighbor cells is delivered in the SIB11 message. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 33
  • 43. 2G-3G Interoperation Analysis Guide Table 3-3 Internal Use Only▲ Key 2G->3G Cell Reselection Parameters FDD_Qoffset FDD Reselection Offset 0 (–∝) FDD_Qmin Minimum value of Ec/No of UTRAN reselection cell 7(–12 dB) Qsearch_I Threshold for UE to start UTRAN cell reselection measurement 7 (always) Table 3-4 Key 3G->2G Cell Reselection Parameters Parameter Description Baseline Value Qqualmin Lowest access quality of 3G cell signal –18 dB QRxLevMin Lowest access strength of 3G cell signal –115 dBm SSearchRat Inter-RAT measurement trigger threshold for cell reselection 6 dB QHyst1S Reselection delay of serving cell 1 10 dB Qoffset1SNSib11 Quality offset 1 of serving and neighbor cells in SIB11 10 dB Qoffset1SNSib12 Quality offset 2 of serving and neighbor cells in SIB12 0 dB Treselection Time duration of cell reselection timer 1s 3.2.1 Key 2G->3G Reselection Parameters 3.2.1.1 FDD_Qoffset  Description If a UTRAN neighbor cell has been switched on (a 3G cell itself should meet certain conditions) and it satisfies the demand of starting measurement that is set in the cell, a UE can reselect the UTRAN neighbor cell after it meets the three conditions below: The RSCP (received signal code power) of the neighbor cell is higher than the RLA_C. The RSCP of the neighbor cell is higher than the RLA_Cs of all the GSM neighbor cells by at least FDD_Qoffset (FDD reselection offset), and it lasts at least 5 seconds (if it reselected a GSM cell 15 seconds ago, the FDD_Qoffset still needs 5 dB increment). The Ec/No of the neighbor cell is higher than or equal to the FDD_Qmin set in the cell (the minimum Ec/No of the UTRAN reselection cell). ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 34
  • 44. 2G-3G Interoperation Analysis Guide Internal Use Only▲ If there are more than one UTRAN cells that can meet the conditions above, the cell with the highest RSCP is selected.  Impact on the network performance This parameter is set to 8, which shows that the signal offset between GSM and 3G is 0. However, the 3G system is usually in the 2G band, and the propagation loss is large. It is better to set to 0 according to the actual experience, which means that the impact of the 3G signal is not taken into account in the reselection process from GSM to 3G, in order to improve the reselection success rate from 2G to 3G.  Parameter configuration (iBSC V6.20.614C) OMC GERAN Subnet User ID BSC Management NE User ID Configuration Set ID BSC Global Resource ID BS Configuration BS ID Cell ID UTRAN Cell Control Basic Attribute 1 3.2.1.2 FDD_Qmin  Description When it reselects the UTRAN neighbor cell, it requires that the value of Ec/No is not less than the value of the cell.  Impact on the network performance It is a key 2G->3G reselection parameter and the recommended value is 7(-12 dB) for network optimization. The difference of the reselection judgment thresholds between the WCDMA and GSM/GPRS systems should be at least 4 dB, such as the SsearchRAT parameter for WCDMA and the FDD_Qmin parameter for GSM/GPRS. It is set to 7 in order to improve the reselection success rate from 2G to 3G.  Parameter configuration (iBSC V6.20.614C) OMC GERAN Subnet User ID BSC Management NE User ID Configuration Set ID BSC Global Resource ID BS Configuration BS ID Cell ID UTRAN Cell Control Basic Attribute 1 3.2.1.3 Qsearch_I  Description When the RLA_C of the cell is lower (0~6) or higher (8~14) than the threshold, a UE starts the measurement of the UTRAN reselection cells. 7 refers to always and 15 refers to never. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 35
  • 45. 2G-3G Interoperation Analysis Guide  Internal Use Only▲ Impact on the network performance For the Qsearch_I parameter, the UE measures the inter-RAT cells all the time after it enters the cell that is expected for interoperability. As long as the 3G system signal condition is satisfied for residence, it will reselect the system. If the system is requested to support the GSM->3G reselection, it is recommended to set to 7 for a cell with inter-RAT neighbor cells, in order to improve the reselection success rate from 2G to 3G. It is set to 15 for closing the measurement.  Parameter configuration (iBSC V6.20.614C) OMC GERAN Subnet User ID BSC Management NE User ID Configuration Set ID BSC Global Resource ID BS Configuration BS ID Cell ID UTRAN Cell Control Basic Attribute 1 3.2.2 Key 3G->2G Reselection Parameters 3.2.2.1 Qqualmin  Description This parameter shows the minimum level of quality demand for selection and reselection which is satisfied by a cell. When it is CPICH Ec/No for measurement, as long as the quality value of the measured cell is bigger than the Qqualmin, it can satisfy the condition of cell selection. The default value is -18 dB. Table 3-5 Qqualmin Description Wireless Parameter Name Full Name Qqualmin(dB) Abbreviation QQualMin Description This parameter shows the minimum level of quality demand for selection and reselection which is satisfied by a cell. When it is CPICH Ec/No for measurement, as long as the quality value of the measured cell is bigger than the Qqualmin, it can satisfy the condition of cell selection. The default value is -18 dB. Value Range and Stepsize [-24, 0] dB; Step 1 dB Unit dB Default Value (Remarks) -18 dB  Impact on the network performance ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 36
  • 46. 2G-3G Interoperation Analysis Guide Internal Use Only▲ If the value of this parameter increases, the condition of cell selection is difficult to be satisfied; if the value of this parameter decreases, the condition of cell selection is easy to be satisfied. However, it is likely that a UE cannot receive the system message borne by the PCCPCH correctly after it resides in the cell.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: view Configuration Management RNC NE RNC Radio Resource Management Utran cell Utran cell xx Modify Advanced Parameter SCCPCH 3.2.2.2 SsearchRAT  Description This parameter shows the trigger threshold Ssearch,RAT of inter-RAT measurement for reselection. The UE is used to determine whether to carry out the inter-RAT measurement. When the HCS is not used, if the quality of the serving cell is higher than the Ssearch,RAT , the inter-RAT measurement will not be performed, if the quality of the serving cell is not higher than the Ssearch,RAT or the Ssearch,RAT is not configured, the inter-RAT measurement will be performed. For details, refer to TS 25.304. Table 3-6 SsearchRAT Description Wireless Parameter Name Full Name Ssearch, RAT(dB) Abbreviation SSearchRat Description This parameter shows the trigger threshold Ssearch, RAT of inter-RAT measurement for reselection. The UE is used to determine whether to carry out the inter-RAT measurement. When the HCS is not used, if the quality of the serving cell is higher than the Ssearch, RAT, the inter-RAT measurement will not be performed, if the quality of the serving cell is not higher than the Ssearch, RAT or the Ssearch, RAT is not configured, the inter-RAT measurement will be performed. For details, refer to TS 25.304. Value Range and Stepsize [0, 20] dB; Step 2 dB Unit dB Default Value (Remarks) 6 dB  Impact on the network performance This parameter works as the trigger threshold of inter-RAT measurement in the selection and reselection processes for the HCS cell. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 37
  • 47. 2G-3G Interoperation Analysis Guide Internal Use Only▲ The factors that should be taken into account for parameter configuration include: cell residence and UE battery consumption. The higher the parameter is, the easier the inter-RAT measurement is triggered and the more the UE battery consumes. The smaller the parameter is, the more difficult the inter-RAT measurement is triggered; and it cannot reside in the cell with good quality in time, which causes call loss easily.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: View Configuration Management RNC NE RNC Radio Resource Management Advanced Parameter Manage ueCnst Waiting Time for Receiving "In Sync" from L1 in Connected Mode (T312 in Connected Mode) 3.2.2.3 QRxLevMin  Description This parameter shows the minimum threshold of received level for selection and reselection which is satisfied by a cell. When it is CPICH RSCP for measurement, the quality value of the measured cell is bigger than the Qrxlevmin, which can just satisfy the condition of cell selection. Table 3-7 QRxLevMin Description Wireless Parameter Name Full Name Qrxlevmin(dBm) Abbreviation QRxLevMin Description This parameter shows the minimum threshold of received level for selection and reselection which is satisfied by a cell. When it is CPICH RSCP for measurement, the quality value of the measured cell is bigger than the Qrxlevmin, which can just satisfy the condition of cell selection. Value Range and Stepsize [-115,-25] dBm step 2dBm Unit dBm Default Value (Remarks) -115 dBm  Impact on the network performance The higher this parameter is, the more difficult UE resides in the cell, which leads to be off the network. The lower this parameter is, the easier it is to reside, but it may lead to that a UE cannot receive the system message borne by PCCPCH correctly after it resides in the cell. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 38
  • 48. 2G-3G Interoperation Analysis Guide Internal Use Only▲ Adjustment recommendation: it is not adjusted generally, and it is not recommended to be adjusted.  Parameter configuration Log on the OMC-R and set in the path below. OMC path: View Configuration Management RNC NE RNC Radio Resource Management UltranCell UltranCellXXX Modify Advanced Parameter UTRAN Cell Indicator of Cell Re-establishment when OCNS Codes Changed 3.2.2.4 QHyst1S  Description This parameter shows the delay parameter of FDD cell reselection for judgment when the measurement value is CPICH RSCP or Cpich EcNo. In the rule of value R ordering for reselection, the R value of serving cell is equal to the measurement value and reselection delay. When the measurement value is Cpich RSCP, calculate and order the R values according to the Qhyst1s. When the measurement value is Cpich EcNo, first calculate and order the R values according to the Qhyst1s, the UTRAN cell ranks at the top, then calculate and order the R values according to the signal quality of Cpich EcNo. Table 3-8 QHyst1S Description Wireless Parameter Name Full Name Qhyst1s(dB) Abbreviation QHyst1S Description This parameter shows the delay parameter of FDD cell reselection for judgment when the measurement value is CPICH RSCP or Cpich EcNo. In the rule of value R ordering for reselection, the R value of serving cell is equal to the measurement value and reselection delay. When the measurement value is Cpich RSCP, calculate and order the R values according to the Qhyst1s. When the measurement value is Cpich EcNo, first calculate and order the R values according to the Qhyst1s, the UTRAN cell ranks at the top, then calculate and order the R values according to the signal quality of Cpich EcNo. Value Range and Stepsize [0, 40] dB; Step2 dB Unit dB Default Value (Remarks) 10 dB  Impact on the network performance ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 39
  • 49. 2G-3G Interoperation Analysis Guide Internal Use Only▲ The higher this parameter is, the more difficult the reselection is triggered, and the less sensitive it is relatively for the signal variation. The lower this parameter is, the easier the reselection is triggered, and the more ping-pong reselections occur, which increase the signaling load. Adjustment recommendation: It can be set to be higher properly for the scenario where the signal changes fast.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: view Configuration Management RNC NE RNC Radio Resource Management Utran cell Utran cell xx Modify Advanced Parameter PICH 3.2.2.5 Qoffset1s,n in SIB11(dB)  Description This parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH RSCP. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB11. The R value of the neighbor cell is equal to be the measured signal quality of the neighbor cell subtracting this offset. Note: For idle or connected mode, when the SIB12 is not broadcast, it is equal to the value of Qoffset1SNSib11 when the reselection measurement value is RSCP; for connected mode, when the SIB12 is broadcast, it is equal to the value of Qoffset1SNSib12 when the reselection measurement value is RSCP. Table 3-9 Qoffset1s,n in SIB11(dB) Description Wireless Parameter Name Full Name Qoffset1s,n in SIB11(dB) Abbreviation Qoffset1SNSib11 Description This parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH RSCP. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB11. Value Range and Stepsize OMCR: [-50, 50] dB; Unit dB ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 40
  • 50. 2G-3G Interoperation Analysis Guide Internal Use Only▲ Wireless Parameter Name Default Value (Remarks)  0 dB Impact on the network performance The factors that should be taken into account for configuring this parameter include the degree of difficulty for reselection and the tendentiousness of reselection. The lower this parameter is, the easier it reselects this neighbor cell. The higher this parameter is, the more difficult it reselects this neighbor cell. It can be set to be different values for different GSM neighbor cells, in order to control the tendentiousness of reselection for different GSM neighbor cells. Adjustment recommendation: For a co-frequency neighbor cell, adjust the value of this parameter in order to reselect cell when the neighbor cell is better than the source cell. For a different-frequency or inter-RAT neighbor cell, it is configured according to the service planning of the multi-carrier networking.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: View Configuration Management RNC NE RNC Radio Resource Management UltranCell UltranCellXXX Neighboring Cell Advanced Parameter Manager Qoffset1s,n in SIB11(dB) 3.2.2.6 Qoffset1s,n in SIB12(dB)  Description This parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH RSCP. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB12. Note: For idle or connected mode, when the SIB12 is not broadcast, it is equal to the value of Qoffset1SNSib11 when the reselection measurement value is RSCP; for connected mode, when the SIB12 is broadcast, it is equal to the value of Qoffset1SNSib12 when the reselection measurement value is RSCP. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 41
  • 51. 2G-3G Interoperation Analysis Guide Table 3-10 Internal Use Only▲ Qoffset1s,nin SIB12(dB) Description Wireless Parameter Name Full Name Qoffset1s,n in SIB12(dB) Abbreviation Qoffset1SNSib12 Description This parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH RSCP. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB12. Value Range and Stepsize OMCR: [-50, 50]dB Unit dB Default Value (Remarks) 0 dB  Impact on the network performance The factors that should be taken into account for configuring this parameter include the degree of difficulty for reselection and the tendentiousness of reselection. The lower this parameter is, the easier it reselects this neighbor cell. The higher this parameter is, the more difficult it reselects this neighbor cell. It can be different values for different UMTS neighbor cells, in order to control the tendentiousness of reselection for different UMTS neighbor cells. Adjustment recommendation: Generally the SIB12 is not used, it is not recommended to adjust this parameter.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: View -> Configuration Management -> RNC NE -> RNC Radio Resource Management -> UltranCell -> UltranCellXXX -> Neighboring Cell -> Advanced Parameter Manager -> Qoffset1s,n in SIB12(dB) 3.2.2.7 Treselection  Description This parameter shows the timer duration of reselection. To be a serving cell, a new cell must be the best cell according to the ordering R principle, and it lasts for Treselections, which can be selected the new serving cell. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 42
  • 52. 2G-3G Interoperation Analysis Guide Table 3-11 Internal Use Only▲ Treselection Description Wireless Parameter Name Full Name Treselection(s) Abbreviation TReselection Description This parameter shows the timer duration of reselection. To be a serving cell, a new cell must be the best cell according to the ordering R principle, and it lasts for Treselections, which can be selected the new serving cell. Value Range and Stepsize [0, 31]s; step 1s Unit S Default Value (Remarks) 1s  Impact on the network performance The factors that should be taken into account for configuring this parameter include the signal quality variation and ping-pong reselection. This parameter is used to avoid the ping-pong reselection. If it is set to be too lower, the ping-pong reselection is easy to occur. If it is set to be too higher, the reselection is slower, which may lead to call loss. Adjustment recommendation: In the scenario of high-speed railway or highway, it is set to be lower in order to speed up the reselection speed and improve the call success rate.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: View Configuration Management RNC NE RNC Radio Resource Management Advanced Parameter Manage ueCnst Waiting Time for Completion of Cell Update When Radio Link Fails and Radio Bearer(s) Associated with T315 Exist (T315) 3.2.2.8 Qhyst2s(dB)  Description This parameter shows the delay parameter of FDD cell reselection for judgment when the measurement value is CPICH Ec/No. In the rule of value R ordering for reselection, the R value of serving cell is equal to the measurement value and reselection delay. Refer to TS 25.304 for details. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 43
  • 53. 2G-3G Interoperation Analysis Guide Table 3-12 Internal Use Only▲ Qhyst2s(dB) Description Wireless Parameter Name Full Name Qhyst2s(dB) Abbreviation QHyst2S Description This parameter shows the delay parameter of FDD cell reselection for judgment when the measurement value is CPICH Ec/No. In the rule of value R ordering for reselection, the R value of serving cell is equal to the measurement value and reselection delay. Refer to TS 25.304 for details. Value Range and Stepsize [0, 40] dB; Step 2 dB Unit dB Default Value (Remarks) 2 dB  Impact on the network performance The factors that should be taken into account for configuring this parameter include the signal variation and ping-pong reselection. The higher this parameter is, the more difficult the reselection is triggered, and the less sensitive it is relatively for the signal variation. The lower this parameter is, the easier the reselection is triggered, and the more ping-pong reselections occur, which increase the signaling load. Adjustment recommendation: it can be set to be higher properly for the scenario where the signal varies very fast.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: View -> Configuration Management -> RNC NE -> RNC Radio Resource Management -> RCP Scrambling Code Configuration Information -> Ending No. of RCP Scrambling Code 3.2.2.9 Qoffset2s,n in SIB11(dB)  Description This parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH Ec/No. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB11. The R value of the neighbor cell is equal to be the measured signal quality of the neighbor cell subtracting this offset. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 44
  • 54. 2G-3G Interoperation Analysis Guide Table 3-13 Internal Use Only▲ Qoffset2s,n in SIB11(dB) Description Wireless Parameter Name Full Name Qoffset2s,n in SIB11(dB) Abbreviation Qoffset2SNSib11 Description This parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH Ec/No. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB11. The R value of the neighbor cell is equal to be the measured signal quality of the neighbor cell subtracting this offset. Value Range and Stepsize OMCR: [-50, 50] dB; Unit dB Default Value (Remarks) 0 dB  Impact on the network performance The factors that should be taken into account for configuring this parameter include the degree of difficulty for reselection and the tendentiousness of reselection. The lower this parameter is, the easier it reselects this neighbor cell. The higher this parameter is, the more difficult it reselects this neighbor cell. It can be set to be different values for different UMTS neighbor cells, in order to control the tendentiousness of reselection for different UMTS neighbor cells. Adjustment recommendation: For a co-frequency neighbor cell, adjust the value of this parameter in order to reselect cell when the neighbor cell is better than the source cell. For a different-frequency or inter-RAT neighbor cell, it is configured according to the service planning of the multi-carrier networking.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: View -> Configuration Management -> RNC NE -> RNC Radio Resource Management -> UltranCell -> UltranCellXXX -> Neighboring Cell -> Advanced Parameter Manager -> Qoffset2s,n in SIB11(dB) 3.2.2.10 Qoffset2s,n in SIB12(dB)  Description ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 45
  • 55. 2G-3G Interoperation Analysis Guide Internal Use Only▲ This parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH Ec/No. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB12. Table 3-14 Qoffset2s,n in SIB12(dB) Description Wireless Parameter Name Full Name Qoffset2s,n in SIB12(dB) Abbreviation Qoffset2SNSib12 Description This parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH Ec/No. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB12. Value Range and Stepsize OMCR: [-50, 50] dB;RNC: D=P+50, [0, 100] Unit dB Default Value (Remarks) 0 dB  Impact on the network performance The factors that should be taken into account for configuring this parameter include the degree of difficulty for reselection and the tendentiousness of reselection. The lower this parameter is, the easier it reselects this neighbor cell. The higher this parameter is, the more difficult it reselects this neighbor cell. It can be set to be different values for different UMTS neighbor cells, in order to control the tendentiousness of reselection for different UMTS neighbor cells. Adjustment recommendation: Generally the SIB12 is not used, it is not recommended to adjust this parameter.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: View -> Configuration Management -> RNC NE -> RNC Radio Resource Management -> UltranCell -> UltranCellXXX -> Neighboring Cell -> Advanced Parameter Manager -> Qoffset2s,n in SIB12(dB) 3.2.3 Recommended Values of Key Reselection Parameters 1. 3G->2G Reselection ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 46
  • 56. 2G-3G Interoperation Analysis Guide Table 3-15 Internal Use Only▲ Recommended Values of Key 3G ->2G Reselection Parameters Parameter Description Baseline Value Value of Unicom Qqualmin Lowest access quality of 3G cell signal -18 dB -18 dB QRxLevMin Lowest access strength of 3G cell signal -115 dBm -115 dBm SSearchRat inter-RAT measurement trigger threshold for cell reselection 6 dB 4dB QHyst1S Reselection delay of serving cell 1 10 dB 10 dB Qoffset1SNSib11 Quality offset 1 of serving and neighbor cells in SIB11 10 dB 0 dB Qoffset1SNSib12 Quality offset 2 of serving and neighbor cells in SIB12 0 dB 0 dB Treselection Time duration of cell reselection timer 1s 1s Note: The values of Unicom are different according to the different requirements from each city. The values above are only for reference, the values for each project depend on the actual. 2. 2G->3G Reselection Table 3-16 Key 2G ->3G Reselection Parameters FDD_Qoffset FDD Reselection Offset 0 (–∝) FDD_Qmin Minimum value of Ec/No of UTRAN reselection cell 7(-12 dB) Qsearch_I Threshold for UE to start UTRAN cell reselection measurement 7 (always) Note: It shows -∝ when the FDD_Qoffset is set to 0. The reason for setting it to be 0 is that UE does not need to consider the strength comparison between 2G and 3G. If it requires the UE to select 3G as far as possible in the field, this parameter can be set to 0. It is only reference for 2G parameters, which should be set according to the demands of each project. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 47
  • 57. 2G-3G Interoperation Analysis Guide 3.3 Internal Use Only▲ Typical Inter-RAT Handover Parameters The key handover control parameters from WCDMA to 2G are mainly determined by the parameters that trigger the 2D, 2F and 3A events. The lower the trigger thresholds of 2D and 3A are, the more traffic stays in the 3G network. But the lower the two parameters are, the worse 3G signal there is for handover and the easier the call drops occur. The 2D and 3A parameters are set to be higher, thus the service can be switched to 2G cell before the WCDMA signal gets worse, in order to decrease the call drop rate. Through the test results, in order to avoid the call drop in the edge of 3G network, it should start the inter-RAT measurement in the condition of a better 3G signal, which means that the 2D event trigger level should be too lower for the circuit domain service in the different system. However, the thresholds of 2D and 3A cannot be too higher, or it will lead to that a large number of 3G subscribers switch to the 2G cells and the GSM traffic increases. These key parameters are described below. 3.3.1 2D/2F Event Threshold  Description This parameter shows the absolute threshold configured for 2D/2F event (used for judging the quality of the carrier frequency being used). Table 3-17 2D/2F Event Configured Threshold Wireless Parameter Name Full Name Absolute threshold configured for 2D/2F event (used for judging the quality of the carrier frequency being used). Abbreviation ThreshUsedFreq[MAX_INTER_MEAS_EVENT] Description This parameter shows the absolute threshold configured for 2D/2F event (used for judging the quality of the carrier frequency being used). The MAX_INTER_MEAS_EVENT is the maximum number of inter-frequency measurement event, and the value is 6. Value Range and Stepsize CPICH RSCP: [-115,-25] dBm;CPICH Ec/No: [-24,0] dB Pathloss: [30,165] dB Unit dBm /dB Default Value (Remarks) Reported parameter of UE periodical measurement when the measurement value is CPICH Ec/No: Reported parameter of UE inter-frequency event when the measurement value is CPICH Ec/No: [-13, -5]dB Reported parameter of UE periodical measurement when the measurement value is CPICH RSCP: Reported parameter of UE inter-frequency event when the measurement value is CPICH RSCP: [-95, -80] dBm  Impact on the network performance ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 48
  • 58. 2G-3G Interoperation Analysis Guide Internal Use Only▲ The 2D and 2F events are the switch of the compact model. The lower the 2D threshold is, the more difficult the 2D is triggered. The lower the 2F threshold is, the easier the 2F is triggered. As the requested signal quality and inter-RAT handover policies are different according to different service types, so the inter-RAT measurement thresholds are divided into CS and PS signaling. When a cell is in the center of carrier frequency coverage, it will use the Ec/No measurement value as the criterion of the 2D and 2F events. Therefore, if the compact model is expected to start as early as possible, set the 2D event threshold to be higher, otherwise set it to be lower. If the ping-pong handover is expected to decrease in the start and stop processes of the compact model, it can increase the difference between the 2D and 2F thresholds. The easier the event is triggered, the more number of average handover time there is, which increases the handover success rate, but consumes the system resources. Note: It can choose Ec/Io or RSCP as the trigger threshold of each event, according to the actual situation. At the edge of the cell coverage, the system is usually limited for the uplink loss, which triggers the inter-RAT handover caused by coverage. The range of Ec/Io is relatively smaller, which is not suitable for the handover caused by coverage as it varies very fast, so it is recommended to adopt the RSCP. For the center of the cell coverage, there is more interference and the system is usually limited for the downlink interference, which triggers the inter-RAT handover. Therefore, the Ec/Io can better reflect the interference degree of the system. Currently it adopts RSCP for the trigger threshold of each event.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: View->Configuration Management->RNC NE->RNC Radio Resource Management->Modify Advanced Parameter->UE Inter-frequency Measurement Configuration-> Absolute Threshold of the Quality of the Currently Used Frequency for 2B/2D/2F 3.3.2 3A/3C Event Threshold  Description This parameter shows the absolute threshold value for judging the quality of other system, which is configured for 3A/3C event. The value range and unit of this parameter are related to the measurement value of other system cell, which is only for the GSM Carrier RSSI of GSM system now, corresponding to the CPICH RSCP ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 49
  • 59. 2G-3G Interoperation Analysis Guide Internal Use Only▲ of local system. Therefore, the value range and unit of this parameter correspond to the CPICH RSCP. Table 3-18 3A/3C Threshold Parameter Wireless Parameter Name Full Name Absolute threshold value for judging the quality of other system, which is configured for 3A/3C event Abbreviation ThreshSys[MAX_RAT_MEAS_EVENT] Description This parameter shows the absolute threshold value for judging the quality of other system, which is configured for 3A/3C event. The value range and unit of this parameter are related to the measurement value of other system cell, which is only for the GSM Carrier RSSI of GSM system now, corresponding to the CPICH RSCP of local system. Therefore, the value range and unit of this parameter correspond to the CPICH RSCP. MAX_RAT_MEAS_EVENT is the maximum number of inter-RAT measurement event, and the value is 4. Value Range and Stepsize CPICH RSCP: [-115,-25]dBm step 1dBm CPICH Ec/No: [-24,0] dB step 1dB Unit dBm /dB Default Value (Remarks) Periodically-reported parameter when the measurement value is CPICH Ec/No of local system: Reported parameter by UE event when the measurement value is CPICH Ec/No of local system: [-6, -24] Periodically-reported parameter when the measurement value is CPICH RSCP of local system: Reported parameter by UE event when the measurement value is CPICH RSCP of local system: [-95, -115]  Impact on the network performance The factors that should be taken into account for configuration include the compression moulding start time, the average handover times, and the handover success rate. For the 3A/3C, the lower it is, the more difficult it is triggered, or the higher it is, the easier it is triggered. For the 3B, the higher it is, the more difficult it is triggered, or the lower it is, the easier it is triggered. Adjustment recommendation: i. In order to avoid the capacity loss caused by starting compression moulding, as long as the compression moulding of inter-RAT measurement is enabled by 2D event trigger, it is expected to switch to the 2G system as soon as possible, so the 2G system threshold should not be higher. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 50
  • 60. 2G-3G Interoperation Analysis Guide ii. Internal Use Only▲ If the quality of inter-RAT neighbor cell is also poor, the service switches rashly. There is a high rate of call drop, and the service quality cannot be guaranteed after handover. So this threshold cannot be set to be lower, in order to guarantee the service to be normal. Note: According to the current 3G strategy, let the 3G subscribers enjoy the 3G services as far as possible, and it adopts the 3A event trigger for the network.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: View->Configuration Management->RNC NE->RNC Radio Resource Management-> Modify Advanced Parameter->UE Inter-RAT Measurement Configuration Information-> Absolute Threshold of the Quality of Other RAT for 3A/3B/3C 3.3.3 Hysteresis(Rat)  Description This parameter shows the delay for judging whether a event satisfies the event trigger condition. Table 3-19 Hysteresis(Rat) Parameter Description Wireless Parameter Name Full Name Hystersis(dB) Abbreviation Hysteresis[MAX_RAT_MEAS_EVENT] Description This parameter shows the delay for judging whether a event satisfies the event trigger condition. Using this parameter will generate a difference value between the state of triggering an event and the left state of triggering an event, which avoids that even a little variation can change the trigger state. It is configured for different events individually with different values. The MAX_INTER_MEAS_EVENT is the maximum number of inter-frequency measurement event, and the value is 6. Value Range and Stepsize (0, 0.5..14.5) dB step 0.5 dB Unit dB Default Value (Remarks) Periodically-Reported parameter by UE when the measurement value is CPICH Ec/No: Reported parameter by UE inter-frequency event when the ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 51
  • 61. 2G-3G Interoperation Analysis Guide Internal Use Only▲ Wireless Parameter Name measurement value is CPICH Ec/No: [4,4,4,4,4,4]dB Periodically-Reported parameter by UE when the measurement value is CPICH RSCP: Reported parameter by UE inter-frequency event when the measurement value is CPICH RSCP: [4,4,4,4,4,4]dB Reported parameter by UE inter-frequency event when the measurement value is CPICH Ec/No (GSM): [4, 4]dB Reported parameter by UE inter-frequency event when the measurement value is CPICH RSCP (GSM): [4, 4]dB  Impact on the network performance The factors that should be taken into account for configuration include the average handover times, handover success rate, terminal movement speed and the handover area size. The higher this parameter is, the less probability the inter-frequency event is triggered, and the less times of average handover there are, which increases the risk of call drop. The lower this parameter is, the more probability the inter-frequency event is triggered, and the more times of average handover there are, which may lead to a mistake handover. Adjustment recommendation: For the scenario of small handover area or terminal moving fast, in order to complete the handover timely, it can be set to be lower properly. On the contrary, it needs to be set to be a little higher. This parameter is related to the measurement value and event type. If decreasing the delay, it can increase the probability of reporting the corresponding events. On the contrary, it can decrease the probability of reporting the corresponding events if increasing the delay.  Parameter configuration Log on the OMC-R and set in the path below. Interface Path: View->Configuration Management->RNC NE->RNC Radio Resource Management-> Modify Advanced Parameter->UE Inter-RAT Measurement Configuration Information-> Hysteresis ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 52
  • 62. 2G-3G Interoperation Analysis Guide 3.3.4 Internal Use Only▲ Recommended Values of Key Inter-RAT Handover Parameters Table 3-20 3G->2G Parameters List Parameter Definition Class Baseline Value of Value Unicom Unit CS dB –13 -13 PS dB –13 -13 CS dBm –95 -95 PS dBm –95 -105 Delay range for 2D judgment CS/PS dB 4 4 TimeToTrigger2D Timer to trigger Event 2D CS/PS ms 640 640 CPICH Ec/Io 2F Threshold 2F quality threshold CS dB –5 -5 PS dB –5 -5 CPICH RSCP 2F Threshold 2F strength threshold CS dBm –80 -90 PS dBm –80 -100 Hysteresis2F Delay range for 2D judgment CS/PS dB 4 4 TimeToTrigger2F Timer to trigger Event 2F CS/PS ms 640 640 3A quality threshold CS dB –6 -6 3A quality threshold PS dB –6 -6 CS dBm –95 -92 PS dBm –95 -102 CPICH Ec/Io 2D Threshold 2D quality threshold CPICH RSCP 2D Threshold 2D strength threshold Hysteresis2D CPICH Ec/Io 3A Threshold CPICH RSCP 3A Threshold 3A strength threshold Hysteresis3A 3A delay window CS/PS dB 4 4 TimeToTrigger3A Timer to trigger Event 3A CS/PS ms 100 100 Note: The values of Unicom are different according to the different requirements from each city. The values above are only for reference, the values for each project depend on the actual. 3.4 Setting for 2G/3G Inter-RAT Neighbor Cells To set the 2G/3G inter-RAT neighbor cells, the general methods are as follows: ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 53
  • 63. 2G-3G Interoperation Analysis Guide Internal Use Only▲  The setting for the neighbor cell is based on the different interoperability strategies of 2G/3G.  When the coverage is not continuous within the UMTS network, the interoperability between the whole network and 2G system should be taken into account. The method of configuring 2G neighbor cells for the whole network is the same as the method of configuring neighbor cells within the system, and the traffic congestion of the neighbor cells should also be taken into account.  When the coverage is continuous within the UMTS network, and it only switches between the edge of the UMTS system and 2G system, it only needs to configure the neighbor cells for the edge base stations, and the principles below should be considered: The co-location and co-direction cells are set to be the neighbor cells. Generally, GSM900 is preferred, and the traffic-balancing and capacity of GSM900/1800 also should be considered. The congestion GSM cells are not to be set as far as possible. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 54
  • 64. 2G-3G Interoperation Analysis Guide 4 Internal Use Only▲ Interoperability Problems Analysis and Optimization The main points for evaluating the quality of inter-RAT interoperability is that, dual-mode terminal can move smoothly from one network to another network, without off the network or calls dropped. The key to achieve a smooth migration is how to adjust the relationship between GSM and WCDMA, after a long period of optimization, the signal distribution of GSM network has become more reasonable, so the adjustment should be primarily focused on the WCDMA side. Specific adjustment principles are as follows:  Avoid a sudden decline of the signal in the border area of WCDMA coverage, if there is a sudden decline in the border area of ECDMA, it is suggested to optimize the network, increase the signal strength or reselect the WCDMA signal. This principle also applies to the signal of internal WCDMA for different frequency handover.  Avoid the overlap between the borders of WCDMA and GSM. if GSM has a good coverage in the border of WCDMA, it helps to handover from WCDMA to GSM successfully, on the contrary if the border of WCDMA is not set properly, the signal strength of GSM network is not enough while handing over, it will increase the failure possibility of inter-RAT measurement or signaling interaction, which causes the dropped call.  Continuous signal coverage in WCDMA should be implemented as much as possible, reduce the signal blind and weak zones, especially in the places with many people, The WCDMA signal usually declines suddenly in these place, and it is too late to handover and measure between systems and leads to a higher failure probability of the system handover. By increasing the coverage, the inter-RAT handover can be pushed to the edge of 3G coverage, which reduces the number of inter-RAT handover.  The border of WCDMA network should be chosen in the area of low density people, avoiding the area of higher density (stations, terminals, etc.). This will not only reduce the number of inter-RAT handover, but also avoid signaling exchange delay/failure due to lack of processing power, and eventually leading to dropped calls. In addition, according to the specific environment, optimizing WCDMA measurements and switching algorithm parameters to further improve the success rate of inter-RAT handover. Table 4-1 Optimization Methods of Typical Scenarios Scenario General scenario FAQ Rapid changes in local signal or high-speed ZTE Confidential Proprietary Optimization Method 1. First to improve the coverage through network planning and optimization. © 2014 ZTE CORPORATION. All rights reserved. 55
  • 65. 2G-3G Interoperation Analysis Guide Scenario FAQ mobile users, easily dropped calls Internal Use Only▲ Optimization Method 2. Trying the optimization method in the scenario of fast signal changing, but pay attention to the optimized performance of the whole network Still, low-speed If you use CPICH RSCP measurement of the whole network, indoor still scenario prone to frequent handover of PS / reselection 1. Using Ec / Io measurement, 3A events reporting 2. Lower PS handover threshold, reducing the probability of frequent handover / reselection. Fast signal changing Elevator coverage scenario, better coverage outside the elevator, it does not meet the inter-RAT measurement conditions, the coverage of the elevator after closing is poor, leading to high rate of dropped calls 1. Increasing 3G coverage in the lift, 2G-3G handover needs to be avoided. 2. Increasing 2D/2F threshold, 3A handover quality threshold appropriately or reducing 2D delay, so that UE (outside the elevator) can start the inter-RAT measurement as soon as possible. 3. PS service can rebuild automatically, in this scenario, rebuilding is not obvious for the users after calls are dropped, and it does not need to optimize specially. The analysis of typical reselection and handover problems are described below. 4.1 Reselection Problems Analysis and Optimization Avoid the problems of excessive and failed reselections from WCDMA to GSM/GPRS for dual-mode terminals in the edge of a WCDMA network, which decreases the inter-RAT reselection probability and increases the paging success rate of the system. The solution is to set the inter-RAT parameters of cell reselection reasonably, such as the SsearchRAT parameter, if this parameter is set to be too small, the reselection from WCDMA to GSM/GPRS may fail. However, it also cannot be set to be too higher, otherwise the users in some places will reselect GSM/GPRS network too early or ping-pong reselection may occur between systems, which does not meet the 3G preferred strategy. So the inter-RAT parameters of cell reselection should be set reasonably. The parameters SsearchRAT of WCDMA and FDD_Qmin of GSM/GPRS should have the interval of more than 4 dB. Additionally, the edge of WCDMA network reselection cannot be set in the densely populated areas, in order to reduce the probability of cell reselection between WCDMA and GSM/GPRS. At the same time it also reduces the signaling interaction between systems and saves the resource of air interface, and the terminal will save more energy. In the update period of the location area and routing area after system reselection, the terminal will be barred for the outgoing calls as the calling party, and barred for the incoming calls as the called party, so reducing the inter-RAT ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 56
  • 66. 2G-3G Interoperation Analysis Guide Internal Use Only▲ reselection probability can improve the paging success rate of the system correspondingly. 4.2 Handover Problems Analysis and Optimization The prerequisite is that the cell phone is set to dual-mode automatic network selection. This configuration can be queried through the multiRAT_CapabilityList.supportOfGSM and multiRAT_CapabilityList.supportOfMulticarrier parameters in the RRCCONNECTIONSETUPCOMPLETE message. Generally, the dual-mode is set to True. The reason for the inter-RAT failure handover is as shown in the table below. Table 4-2 Inter-RAT Handover Failure Information Element/ Group Name Inter-RAT handover failure cause Need MD Multi Type and Reference Enumerated(Configuration unacceptable, physical channel failure, protocol error, inter-RAT protocol error, unspecified) Semantics Description Default value is "unspecified". 11 spare values are needed. The returned message cell shows that gsm_MessageList is 06 28 XX. XX refers to the GSM information as follows. Figure 4-1 RR Cause Information Element ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 57
  • 67. 2G-3G Interoperation Analysis Guide 4.2.1 Internal Use Only▲ Physical Channel Failure If interRAT_HO_FailureCause.t = 2, it corresponds to the physical channel failure. This phenomenon is due to the access failure on the air interface when the UE attempts to access 2G interface. It may be caused by wrong configuration (handover to a cell that does not exist) of neighbor cell (CGI), poor 2G signal (The threshold set in RNC for handover to 2G is too small), external interference, or UE natural defects (Qualcomm cell phones of Version 4240 have such kind of problem). Currently the most common failure is that, the timer T3124 times out, the 2G RACH channel cannot be accessed. If the neighbor cell is configured correctly, there are three possible reasons as follows: 1. Uplink interference Analysis The GSM channel cannot be synchronized, and the engineers should check the handover success rate of each 2G cell at the same time. Solution Delete the poor 2G neighbor cells. In some areas different frequencies vary widely, the poor frequencies interfere a lot. If the handover success rate is lower than 80%, it needs to summarize the rule of the deleted neighbor cells, and perform the RNC neighbor cell deletion according to the rule. 2. Handover destination was refused before. Analysis For the operator's business marketing strategy, a part of the users are not allowed to subscribe to 2G network. Solution Fundamental solutions: CN supports the service handover based on IUEI, which the user attribute can be known by the access network. Avoidance solution: Cancel the inter-RAT handover. 3. Abnormal cell phone Analysis The problem is related with the cell phone. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 58
  • 68. 2G-3G Interoperation Analysis Guide Internal Use Only▲ Solution If it is PS domain, avoid the handover of such kind of users, if it is CS domain, no handle it or communicate with the cell phone users. 4.2.2 Wrong Configuration Analysis interRAT_HO_FailureCause.t = 1, corresponding to Configuration unacceptable handoverFromUTRANFailure.interRATMessage.gsm_MessageList = 06 28 6f This phenomenon is the most common failure in the foreign countries; it shows that most inter-RAT handovers have failed, only individual cell phones with better compatibility are successful: encryption configuration information is not filled completely. Solution Upgrade BSC or adopt with the CN from ZTE. 4.2.3 Protocol Error interRAT_HO_FailureCause.t = 3, corresponding to protocol error. There is protocol error in the location update request message received; the network sends location update refuse message, the reasons are as follows:  Mandatory information unit error  Information unit does not exist or cannot be achieved  Invalid information unit content  Protocol error interRAT_HO_FailureCause.t = 3, corresponding to inter-RAT protocol error "inter-RAT protocol error" or "configuration unacceptable": UE does not accept the HANDOVER FROM UTRAN COMMAND message issued by RNC, the message format issued by RNC may have problem, or maybe UE does not support the inter-RAT handover. 4.2.4 Parameter Configuration  2D event threshold is not set reasonably, generally the threshold is not advised to set to be too high, it is recommended to set more than 100 dBm, in order to assure the handover success rate; 2D event delay also should be set reasonably. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 59
  • 69. 2G-3G Interoperation Analysis Guide  Internal Use Only▲ 3A event parameter is not set reasonably. When UE is moved from outdoor to indoor, WCDMA signal declines sharply, however the signal in GSM cell is still very strong due to it has indoor distribution system. In this scenario, if the parameter of inter-RAT handover in the WCDMA cell is not set reasonably, it also can lead to the failure of inter-RAT handover.  4.2.5 Relocation failure: Check whether the LAC set by CN is complete; check the radio of relocation failure, if it is more than 20%, please ask CN to check together. Neighbor Cell Configuration   4.2.6 The configuration of neighbor cell is missing; the current WCDMA cell misses the destination GSM neighbor cell (The detected most powerful GSM cell is not the neighbor cell of the current service cell). The configuration of neighbor cell is excessive: the configuration of GSM neighbor cell in for the current WCDMA is excessive, agreement: the maximum quantity of GSM cells measured by UE is 32. Resource Refusing There is no available radio resource in the current destination GSM cell. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 60
  • 70. 2G-3G Interoperation Analysis Guide 5 Cases Study 5.1 PLMN Selection and Reselection 5.1.1 Internal Use Only▲ Case 1 Phenomenon In the A network, the handover from 3G->2G and reselection could not be performed by using MOTO, NOKIA cell phones. Case analysis 1. The voice could be handed over from 3G to 2G, but after hooking on, it returned to 3G from 2G at once, it could not reside in 2G even if it met the condition to reside. 2. The handover failed when the data service met the condition to hand over from 3G to 2G. 3. UE in the 3G IDLE mode could not reselect 2G even if the condition was satisfied. A network adopted different PLMN schemes for 3G/2G, The current 2G did not need to change, and 3G adopted the different PLMN from that of 2G. Network reselection scheme: While UE is residing in 3G, it can reselect 2G through the normal cell reselection; while UE is residing in 2G, it can reselect 3G through equivalent PLMN reselection. Network handover scheme: The voice can be handed over from 3G to 2G, and it reselects 3G back through equivalent PLMN after hooking on. PS data service can be handed over from 3G to 2G, and it reselects 3G back through equivalent PLMN. Problem location The equivalent PLMN was used in PLMN selection, cell selection, reselection and handover. When UE was reselecting, it could access normally only when it detected that the cell was the permitted PLMN; for the case of different PLMNs, if 2G‘s PLMN was not set to be equivalent PLMN in 3G, the following phenomenon shows:  The voice could be handed over from 3G to 2G successfully, but after hooking on in 2G, the cell phone would not update location at once, but research PLMN, the phenomenon was that the cell phone was off the network temporarily. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 61
  • 71. 2G-3G Interoperation Analysis Guide Internal Use Only▲  When the data service met the condition to handover from 3G to 2G, after receiving the CELL CHANGE ORDER issued by RNC, UE failed to search the 2G network, and it returned CELL CHANGE ORDER FAIL.  UE in the 3G IDLE mode could not reselect 2G. Solution Set 2G‘s PLMN to be equivalent PLMN on both 3G‘s UEC and SGSN, the handover from 3G to 2G and reselection were normal. Experience Understand the restrictions of different PLMNs networking, and set the parameters reasonably. 5.2 Cell Selection and Reselection 5.2.1 Case 1 Phenomenon It could not reselect from 3G to 2G due to the measurement for different system was not enabled by UE. Problem location If it was not set to enable the measurement for different systems in the FACH (MOD CELLMEAS), RNC would not issue the information of GSM neighbor cell in SIB 11, even if it already met the condition to enable the measurement for different systems in 3G, it would not reselect due to there was no neighbor cell in the different systems. Solution Enable the measurement for different systems. 5.2.2 Case 2 Phenomenon UE could not reselect from 2G to 3G due to 3G neighbor cell relationship was not set. Problem location After setting the reselection parameters for 2G=>3G, the radio signal had met the condition for reselection to 3G, but the cell phone still could not reselect. The most direct method was to use the background software of the cell phone to track the 2G message ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 62
  • 72. 2G-3G Interoperation Analysis Guide Internal Use Only▲ issued by the network and signal quality measured by UE. If the neighbor cell relationship of 3G was not set in 2G, then there was no 2quater (2ter) message in the system message. Solution Add the 3G cell as the neighbor cell of different systems for 2G cell on the 2G BSC. 5.3 Inter-RAT Handover 5.3.1 Case 1 Phenomenon Frequent handover from 3G to 2G in the cell was caused by the handover parameters configuration for RNC1 and RNC10. Case analysis We performed coverage test for this site by using Agilent tester, but the result showed that the 3G signal of the three cells in the site was good, so the coverage problem was excluded. We performed CQT dialing test in one cell at TRI722W, in the process of test, both parties called in 3G, and handed over to 2G within several seconds, and the call must be ended for handing over to 3G, This 3G/2G handover always occurred in the tests of dozens of times. While moving from one cell (12552) of TRI255W which was the neighbor site of TRI722W to another cell (17223) of TRI722W, in the soft handover area, UE remained in 3G network when 12552 was the best cell, when 17223 became the best cell, UE handed over to 2G network after 3 seconds. So we doubted that the problem existed in the 3 cells of TRI722W. Problem location From the analysis above, we doubted that the inter-RAT handover parameters or strategies of the 3 cells in TRI722W had problem, which speeded up the handover from 3G to 2G. We found that the judgment method of different system event of the 3 cells in TRI722W was ―3C Event Trigger‖, and the absolute threshold value of 3C event was -90 dBm, thus the 2G signal was very easy to achieve -90 dBm in the 3G coverage of the 3 cells in TRI722W, so the handover from 3G to 2G was easy to occur. Solution We modify the judgment method of different system event of the 3 cells in TRI722W to be ―3A Event Trigger", in this way, the handover from 3G to 2G could happen only when the ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 63
  • 73. 2G-3G Interoperation Analysis Guide Internal Use Only▲ 3G signal RSCP tested by UE was below -95 dBm and the 2G signal RSCP was above -90 dBm, this method was hard to achieve. we tested afer the modification, there was no handover from 3G to 2G in the call process within the coverage of TRI722W3G. For the whole network We found that the handover from 3G to 2G was very easy for the configuration 3C Event Trigger and the 2G neighbor cell was configured, thus many call traffic volume of 3G was absorbed by 2G, then we checked the sites distribution of 3C and 3A handover trigger parameters for the whole network, as shown in the table below. Table 5-1 3C Handover Trigger Parameters for the Whole Network and Sites Distribution of 3A Handover Trigger Parameters RNC ID Number of NodeBs With “3A Event Trigger” for Inter-RAT Handover Number of NodeBs With “3C Event Trigger” for Inter-RAT Handover Number of NodeBs With “3C Event Trigger” for Inter-RAT Handover (Configured With 2G Neighbors) RNC1 68 106 20 RNC10 40 50 36 RNC2 120 0 0 Sum 228 156 56 1. If the judgment method of different system event was ―3C Event Trigger‖, and the absolute threshold value of 3C event was -90 dBm, thus the base station of 3C different system trigger (2G neighbor cell was configured) could achieve -90 dBm very easily, so the handover from 3G to 2G occurred very easily, from the statistic form we could see that RNC1 had 20 base stations, and RNC10 had 36 base stations, which belonged to this case, the 56 base stations totally were very easy to handover from 3G to 2G, These sites mainly located around the airport highway and TRIPOLI, but also there were some sites locating in the places where there were high internal call traffic volume in TRIPOLI (for example, Fatah University, Libya's largest university). Fortunately, it was better for the border sites; the handover to 2G was easy, which could ensure the success rate of handover from 3G to 2G and reduced the call drop rate due to the handover from 3G to 2G; However, for the places where had relative densely 3G sites within TRIPOLI, the frequent handover from 3G to 2G would result in the loss of many users and a decline in traffic. For this case there were 2 methods to suggest: The first method was to remove the 2G neighbor cells of the base stations which has relative high call traffic volume in TRIPOLI, and ensure the users within the city reside in the 3G network, but this method would lead to that 3G could not handover to 2G in case of call drop for the indoor places where the signal was not good. The second method was to change the judgment method of different system event from ―3C Event Trigger‖ to ―3A Event Trigger" for cells of base stations which had ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 64
  • 74. 2G-3G Interoperation Analysis Guide Internal Use Only▲ relative high call traffic volume in TRIPOLI, which also could ensure that the users in the city reside in the 3G network. 2. The judgment method of different system event was ―3A Event Trigger", which made the handover from 3G to 2G occur only when the 3G signal RSCP tested by UE was below -95 dBm and the 2G signal RSCP was above -90 dBm, this method was hard to achieve. 3. The current locations of ―3A Event Trigger" sites and ―3C Event Trigger‖ sites in RNC1 and RNC10 were disordered. The locations are shown in the figure below. Figure 5-1 Sites Locations of 3A Event Trigger and 3C Event Trigger is ―3A Event Trigger" site; is ―3C Event Trigger‖ site; is ―3C Event Trigger‖ with 2G neighbor sites configured (56). Experience For the ―3C Event Trigger‖ sites with 2G neighbor sites configured, we determined to test th 2 sites in the dense area, on 28 Aug we tested the ―3C Event Trigger‖ sites with 2G neighbor sites configured, RNC10‘s TRI101W and RNC1‘s TRI119W, in the test process we found that the RSCP on the ground is around from -81 dBm to -86 dBm, which met the requirement in the contract, it is around from -90 dBm to -100dBm in the car when UE is in the different locations, thus 3C event is easy to be triggered by compression mode, so it is easy to enter 2G, as the dense areas are the sensitive places for the customer and there are many users, the 3G signal is the room is easy to be below -95 dBm, and the users often enter 2G, which will cause the dissatisfaction of the 3G users, so change the judgment method of different system event from ―3C Event Trigger‖ to ―3A Event Trigger", which ensures that the users reside in the 3G network. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 65
  • 75. 2G-3G Interoperation Analysis Guide 5.3.2 Internal Use Only▲ Case 2 Phenomenon 3G neighbor cells were missed to configure for 2G, which resulted in the low call traffic volume in the far 3G sites and no 3G signal. Case analysis To resolve the customer complaint, we added the site TRI358, the nearest 3G site from the site was 16 km away, after the site operated normally, by observing KPI we found that CS call traffic volume of each cell was lower, it was around 0.1 erl, and the customer complained that there was no 3G signal, as shown in the figure below. Figure 5-2 TRI358 Site Location Problem location Firstly we checked the cell parameters configuration in the 3G site, and there was no error and alarm. 3G signal was normal by testing on site, and CS and PS services are normal. For the test of inter-RAT handover, we found that 2G cannot handover to 3G, and it We contacted with the engineer for 2G, and confirmed that the cell was missed to be configured as neighbor cell in 2G. The site was a single site, and there was only 2G site around within 16km, many local users use 3G/2G terminals, the cell was missed to be configured as neighbor cell in 2G, it caused that the cell phone in 2G cell cannot reselect to 3G cell, so the user complained that there was no 3G signal, and there were few 3G users under the site. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 66
  • 76. 2G-3G Interoperation Analysis Guide Internal Use Only▲ Solution The configuration of 2G neighbor cell was completed and the problem was solved. Experience For the scenario of single 3G site or few sites, DO configure the 2G neighbor cells reasonably, at the same time the information of 3G sites should also be configured reasonably in 2G. 5.3.3 Case 3 Phenomenon A failure 2G/3G handover case in Unicom of Chongqing Wanzhou Case analysis In the 2G/3G handover test, the cell phone did not hangover regularly, the data configuration was correct by checking, but we found that no increment synchronization was performed after data configuration, which led to the failure handover due to no data issued to RNC. Problem location After the increment synchronization, the handover remained to fail, we captured the signaling of RNC, and we knew that the 2G/3G handover switch of core network was not enabled. Solution   5.3.4 Perform increment synchronization for the data configuration, and issue the configuration to RNC. Enable the 2G/3G handover switch of core network Case 4 Phenomenon The success rate of 3G/2G handover was low due to the wrong configuration of neighbor cell. Case analysis The success rate of handover for RNC1 was around 89%, after troubleshooting we found that each of the three sectors in TRI119W was configured a wrong 2G neighbor cell, so the success rates of handover were low for the site and the sites around, it was around ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 67
  • 77. 2G-3G Interoperation Analysis Guide Internal Use Only▲ 18%, which resulted in that the success rate of handover was only 89% for the whole network. Problem location 1. We checked the handover parameters configuration of the relative sites, the strategy was 3A event, the 2D threshold was -95dBm; the absolute threshold of the cell was -95 dBm/-4; the absolute threshold of 2G cell was -90 dBm, so there was no problem with the parameter configuration. 2. We checked the configuration of the neighbor cell, and found that a wrong 2G neighbor cell TRI191 was configured for the site TRI119W, as shown in the figure below. Figure 5-3 Relative Location of TRI119W and TRI191 So far, the low success rate of handover was founded. At the same time we found that TRI006W-1, TRI006W-3, TRI007W-1, TRI007W-2, TRI007W-3 and TRI011W-3 were the 3G neighbor cells of TRI119W and the 3G cells in the same active set could handover with the commutative 2G cells, so the success rates of handover were low for these cells, too. Solution After the 2G neighbor cells of TRI119W were removed, the success rate of handover increased to 93.5% for the whole network, as shown in the figure below. Figure 5-4 Success Rate of Handover after Deleting 2G Neighbor Cells ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 68
  • 78. 2G-3G Interoperation Analysis Guide Internal Use Only▲ Experience For the success rate of 3G/2G handover, we not only need to pay attention to the neighbor cell of 3G cell , but also need to check whether the configuration of 2G neighbor cell is correct as the neighbor cell of 3G cell. 5.3.5 Case 5 Phenomenon The information of 2G LAC was missed in CN, which lead to the inter-RAT handover cannot be performed. Case analysis For one new 3G site in Indonesia, the service was normal by testing, but the terminal could not handover from 3G to 2G, finally the 3G signal turned to be weak and the call was dropped. The information of 2G neighbor cell could be tested from TEMS; for the handover between 2G/3G systems, generally we analyze it from the points below:  Missed/Wrong configuration for 2G neighbor cell  Problem of GSM network equipment  Problem of parameters (UEC, GSM) configuration Problem location 1. We got the list of 2G neighbor cells from the customer and compared it with the actual configuration, they were identical. 2. The number of sites without inter-RAT handover were around 4 or 5, the other sites were normal, handed over to the cells under the same BSC, so the parameters problem could be excluded; from the sites location figure we could see that, the sites could not handover normally were from the same area, the related 2G sites belonged to one LAC area, and there was no wrong configuration for LAC. 3. We traced the signaling of the cells which could not handover normally in the OMC network management, and found that CN would fail to relocate directly each time after RNC sent the request of relocation, as shown in the figure below. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 69
  • 79. 2G-3G Interoperation Analysis Guide Figure 5-5 Relocation Failure Figure 5-6 Internal Use Only▲ Signaling Flowchart of Inter-RAT Handover From the signaling above we could find that after RNC sent the request of relocation, CN refused directly, the reason was TRANAP_semantic_error, it is a kind of syntax error, generally it is due to that the data does not match, so the problem was located at CN or 2G, finally the LAC codes of these related cells were not added in CN. Solution We created these LACs again in CN and the problem was solved, from OMC traffic statistics, we could see the handover related specifications and the value of counter, the figure below shows the chart of a typical site for inter-RAT handover. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 70
  • 80. 2G-3G Interoperation Analysis Guide Figure 5-7 Internal Use Only▲ Inter-RAT Handover Experience   5.3.6 If the GSM parameter were modified in the 2G system, the GSM parameters in the 3G system must be modified synchronously. The problem analysis follows the principle from the whole to the part, and gradually narrows the range until the problem is solved. Case 6 Phenomenon WCDMA system could not use PS and CS at the same time due to the configuration of encryption algorithm in PS domain. Case analysis When a user used CS voice service firstly, then he used PS service simultaneously in the process of calling, at this time the two services could be used at the same time; but when the user used PS service first, and used CS voice service simultaneously (no matter calling or called), the voice service could not be used, and it was busy tone in the telephone, there was the RNAP_SECURITY_MODE_REJECT message in the traced signaling. Problem location After the user used PS service first and made voice call simultaneously, there was the RNAP_SECURITY_MODE_REJECT message found in the traced signaling, as shown in the figure below. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 71
  • 81. 2G-3G Interoperation Analysis Guide Figure 5-8 Internal Use Only▲ Failure Signaling of Security Mode The detailed reason was as follows. Figure 5-9 Value of Failure Reason The value of failure reason showed that the latest issued integrity protection or encryption information did not match the previous configuration; according to the analysis above, the two services should be configured with different encryption algorithm; Then we checked the encryption algorithm of each service separately: For PS: two encryption algorithms were configured — No Encryption and UEA1. Figure 5-10 Encryption Algorithm for PS Service For CS: Only one encryption algorithm UEA1 was configured here. Figure 5-11 Encryption Algorithm for CS Service According to the protocol: ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 72
  • 82. 2G-3G Interoperation Analysis Guide Internal Use Only▲ The CN initiates the procedure by sending the SECURITY MODE COMMAND message. The message may contain the Encryption Information IE and shall contain the Integrity Protection Information IE, specifying, in preferred order with the most preferred first in the list, which ciphering, if any, and integrity protection algorithms may be used by the UTRAN. RNC will give priority to the first encryption algorithm in the list issued by core network. The user first used PS service, so RNC chose the first encryption algorithm (No Encryption) directly in the list issued by CN. Then at the same time he used voice service, but UEC encryption algorithm for CS is UEA1. But before that RNC has recorded that the user's encryption algorithm was No Encryption, then it was UEA1 at this time, the two were founded to be different, so the RNAP_SECURITY_MODE_REJECT message was issued, which led to that the voice service cannot be established. But PS service always could be used. Solution We adjusted the order of encryption algorithm for PS service, ranked UEA1 at first as follows. Figure 5-12 Encryption Algorithm Encryption algorithm UEA1 ranked first or only UEA1 was configured. When only using only one service, no matter what encryption algorithm was configured for PS or CS, the rejection phenomenon security mode would not appear, but there would be such problem when using the concurrent services. Experience Why was it possible to use CS service first and then use PS service in the process of calling? The reason is as follows: For the case of using CS voice service, RNC will choose the first encryption algorithm directly in the list issued by CN, and there is only one encryption algorithm UEA1. Then use PS service in the process of calling, at this time RNC will not choose the first encryption algorithm directly in the list issued by CN as above, because PS is not the first service, so it will not choose the first encryption algorithm in the list, but it checks what encryption algorithm has been configured for PS service and compares, then it finds that UEA1 has indeed been configured for PS service, So PS is available. As the rule of RNC choosing the first encryption algorithm in the list issued by CN, it is only for the first service. ZTE Confidential Proprietary © 2014 ZTE CORPORATION. All rights reserved. 73

×