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introduction-to-gprs-egprs-

  1. 1. EVOLIUM Base Station Subsystem INTRODUCTION TO GPRS/EGPRS TRAINING MANUAL 3FL10472ACAAWBZZA2 – MARCH 2006 © All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 1
  2. 2. Nt of the page Safety Warning Both lethal and dangerous voltages are present within the equipment. Do not wear conductive jewellery while working on the equipment. Always observe all safety precautions and do not work on the equipment alone. Caution To see the content of the page The equipment used during this course is electrostatic sensitive. Please observe correct anti-static precautions. Trade Marks Use the comment view Alcatel and MainStreet are trademarks of Alcatel. All other trademarks, service marks and logos (“Marks”) are the property of their respective holders including Alcatel. Users are not permitted to use these Marks without the prior consent of Alcatel or such third party owning the Mark. The absence of a Mark identifier is not a representation that a particular product or service name is not a Mark. Copyright 1 This document contains information that is proprietary to Alcatel and may be used for training purposes only. No other use or transmission of all or any part of this document is permitted without Alcatel’s written permission, and must include all copyright and other proprietary notices. No other use or transmission of all or any part of its contents may be used, copied, disclosed or conveyed to any party in any manner whatsoever without prior written permission from Alcatel. 2 Use or transmission of all or any part of this document in violation of any applicable Canadian or other All rights reserved © 2004, Alcatel legislation is hereby expressly prohibited. Introduction to GPRS/EGPRS User obtains no rights in the information or in any product, process, technology or trademark which it includes or describes, and is expressly prohibited from modifying the information or creating derivative works without the express written consent of Alcatel. Alcatel, The Alcatel logo, MainStreet and Newbridge are registered trademarks of Alcatel. All other trademarks are the property of their respective owners. Alcatel assumes no responsibility for the accuracy of the information presented, which is subject to change without notice. © 2004 Alcatel. All rights reserved . Disclaimer In no event will Alcatel be liable for any direct, indirect, special, incidental or consequential damages, including lost profits, lost business or lost data, resulting from the use of or reliance upon the information, whether or not Alcatel has been advised of the possibility of such damages. Mention of non-Alcatel products or services is for information purposes only and constitutes neither an endorsement nor a recommendation. Please refer to technical practices supplied by Alcatel for current information concerning Alcatel equipment and its operation. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 2
  3. 3. Contents 1 What is GPRS ? 6 1.1 Definition 8 1.2 General architecture 9 1.3 MS Class 10 1.4 MS Multislot Class 11 1.5 GPRS Main Concepts 12 1.6 The benefits of GPRS 17 1.7 EGPRS 18 1.8 Quality of service profile 19 1.9 Services 20 2 GPRS Operation 23 2.1 Main Entities 25 2.2 MS Mobility Management States 30 2.3 MS Radio Resource Operating Modes 31 2.4 Basic procedures 32 2.5 Charging 45 2.6 Security 47 3 The Base Station Subsystem 52 3.1 3GPP Position 54 3.2 Alcatel’s Choice 55 3.3 Layered Model 56 3.4 Gb Interface 58 3.5 Radio Interface 60 4 Alcatel Solution 71 4.1 GPRS Network Overview 73 4.2 Alcatel 9135 MFS 74 4.3 Packet Switched Core Network 80 4.4 GPRS Network Management 82 4.5 Alcatel QoS offer 83 5 Annex and Glossary © Alcatel University – 3FL10472ACAAWBZZA Ed.02 88 Page 3
  4. 4. Self assessment of the objectives Contract number : Course title : Client (Company, centre) : Language : English dates from : Number of trainees : to : Location : Surname, First name : Did you meet the following objectives ? Tick the corresponding box Please, return this sheet to the trainer at the end of the training Yes (or Globally yes) Instructional objectives 1 To be able todescribe the organization of a GPRS network,architecture, interfaces and protocols. 3 To be able todescribe the main data interchange mechanisms on a GPRS network 4 Comments To be able toidentify the benefits of GPRS 2 No (or globally no) To be able tocharacterize the solution offered by Alcatel Other comments © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 4
  5. 5. Self assessment of the objectives (continued) Yes (or Globally yes) Instructional objectives No (or globally no) Comments Other comments Thank you for your answers to this questionnaire © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 5
  6. 6. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 6
  7. 7. 1 What is GPRS ? Session presentation > Objective: to be able to identify the technical and commercial benefit of GPRS. > Program: • 1.1 Definition • 1.2 General architecture • 1.3 MS Class • 1.4 MS Multislot Class • 1.5 GPRS Main Concepts • 1.6 GPRS Benefits • 1.7 EGPRS • 1.8 Quality of Service profile • 1.9 Services Introduction to GPRS/EGPRS 7 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 7
  8. 8. 1 What is GPRS ? 1.1 Definition > Definition (3GPP TS 22.060) • GPRS provides data transfer capabilities between a sending entity and one or more receiving entities. • These entities may be an MS or a Terminal Equipment, the latter being attached either to a GPRS network or to an external data network. • The base station provides radio channel access for MSs to the GPRS network. Introduction to GPRS/EGPRS 8 All rights reserved © 2004, Alcatel w PDN (Packet Data Network) IP networks = Internet (connectionless) © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 8
  9. 9. 1 What is GPRS ? 1.2 General architecture RADIO ACCESS NETWORK circuit switching A PSTN NSS BSS GPRS Gb PDN Core Network IP IP / PPP Packet switching Introduction to GPRS/EGPRS Gi 9 All rights reserved © 2004, Alcatel w GPRS Core Network The GPRS Core Network is also called GSS (GPRS Sub-System). It is an IP network, and therefore contains routers (machines handling the packet switching function.) w Routing Function Data transmission between GPRS Support Node (GSN), may occur across external data networks that provide their own internal routing functions, for example X.25 [34], Frame Relay or ATM networks. w IP interworking The GPRS Core Network supports interworking with networks based on the Internet protocol (IP). The GPRS Core Network may provide compression of the TCP/IP header when an IP datagram is used within the context of a TCP connection. w X.25 X.25 PDP Type have been removed from the standard since R99. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 9
  10. 10. 1 What is GPRS ? 1.3 MS Class > Class A • Operates GPRS and other GSM services simultaneously. > Class B • Monitors control channels for GSM GPRS and other GSM services simultaneously, • but can only operate one set of services at one time. > Class C • Exclusively operates GPRS services. Introduction to GPRS/EGPRS 10 All rights reserved © 2004, Alcatel w Classes A and B Require dual scanning by the mobile for both GSM and GPRS service requests. Class A or B mobiles are "attached" simultaneously to both networks. w Class B The exchange of packets is suspended to answer to an incoming GSM call (the GPRS subscriber is considered to be in the "busy" or “on hold" state). The PDP contexts are still active on the SGSN side until the Purge_Timer elapses. w Class C Exclusively operates GPRS services. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 10
  11. 11. 1 What is GPRS ? 1.4 MS multislot class Multi-slot class 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 to 29 like 10 Type Rx Tx Sum Ttb Tra Trb 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 1 2 2 3 2 3 3 4 3 4 4 4 3 4 5 6 7 8 1 1 2 1 2 2 3 1 2 2 3 4 3 4 5 6 7 8 2 3 3 4 4 4 4 5 5 5 5 5 NA NA NA NA NA NA 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 4 3 3 3 3 3 3 2 2 2 2 2 3 3 3 2 1 0 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 x x NA Introduction to GPRS/EGPRS 11 All rights reserved © 2004, Alcatel w MS type Type 1 are simplex MS, i.e. without duplexer: they are not able to transmit and receive at the same time Type 2 are duplex MS, i.e. with duplexer: they are able to transmit and receive at the same time w Rx Maximum number of received timeslots that the MS can use per TDMA frame. The receive TS shall be allocated within window of size Rx, but they need not be contiguous. For SIMPLEX MS, no transmit TS shall occur between receive TS within a TDMA frame. This does not take into account measurement window (Mx). w Tx Maximum number of transmitted timeslots that the MS can use per TDMA frame. The transmit TS shall be allocated within window of size Tx, but they need not be contiguous. For SIMPLEX MS, no receive TS shall occur between transmit TS within a TDMA frame. w SUM Maximum number of transmit and receive timeslot (without Mx) per TDMA frame w Meaning of Ttb, Tra et Trb changes regarding MS types. For SIMPLEX MS (type 1): Ttb Minimum time (in timeslot) necessary between Rx and Tx windows Tra Minimum time between the last Tx window and the first Rx window of next TDMA in order to be able to open a measurement window Trb same as Tra without opening a measurement window For DUPLEX MS (type 2): Ttb Minimum time necessary between 2 Tx windows belonging to different frames Tra Minimum time necessary between 2 Rx windows belonging to different frames in order to be able to open a measurement window Trb same as Tra without opening a measurement window © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 11
  12. 12. 1 What is GPRS ? 1.5 GPRS Main Concepts (1/5) > Use of radio resources in case of circuit switching Radio interface Access node <CS <->PS Radio timeslot GSM network CS PDN PS Fixed Rate Introduction to GPRS/EGPRS 12 All rights reserved © 2004, Alcatel w Drawbacks of CS for data services one radio channel at 9.6 kbit/s per user fixed bit rate => waste (in the case of discontinuous service) and limitation on bit rate © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 12
  13. 13. 1 What is GPRS ? 1.5 GPRS Main Concepts (2/5) > Use of radio resources in case of packet switching Radio interface GPRS PDN network PS PS Radio timeslot Variable Rate Introduction to GPRS/EGPRS 13 All rights reserved © 2004, Alcatel w Benefits of Packet Switching Variable bit rate becomes possible One MS uses several RTSs. The maximum number of RTSs is given by the Operator (O&M parameters) and MS capabilities (MS multislot class) One RTS is shared by several MSs. The maximum number of MSs per RTS is given by the Operator (O&M parameters) and 3GPP specifications (limitation due to addressing availability) © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 13
  14. 14. 1 What is GPRS ? 1.5 GPRS Main Concepts (3/5) > Radio resource assigned according to requirement • Radio resource shared between users • Various radio channel coding schemes are specified to allow bit rates from 9 to more than 150 kb/s per user (according also to the quality of radio transmission and the modulation used) • High bit rates if several channels are assigned to one MS • Low bit rates if one channel is shared by several MSs. > Optimized use of the radio resource • Use of the radio resources only when data is transferred • Uplink and downlink resources reserved separately Introduction to GPRS/EGPRS 14 All rights reserved © 2004, Alcatel w Radio resource sharing The radio resources are shared by statistical multiplexing. As in GSM, no subscriber has their own permanent radio resource. w Bit rate Maximum instantaneous bit rate provides 171,2 kb/s by the allocation of eight RTSs to one subscriber. The stated maximum bit rates are different, because different coding schemes are used, which impacts the bit rate over a RTS. (see Annex) w Up link (UL) and downlink (DL) It is possible to use a different bit rates in each transmission direction, whereas in CS (Circuit Switching) mode, there is a maximum limit of 9.6 kb/s, in both directions and at all times. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 14
  15. 15. 1 What is GPRS ? 1.5 GPRS Main Concepts (4/5) > Dynamic allocation and sharing of radio resources 1 RESOURCE USED BY ONE USER NOT SHARED TCH User 1 User 1 User 2 User 3 User 4 User 5 1 RESOURCE SHARED BY X USERS (PDCH) USER1 USES 3 RESOURCES (3 PDCH) User 1 Number of resources according to the capability of the MS Introduction to GPRS/EGPRS 15 All rights reserved © 2004, Alcatel w Caution: Animated slide that does not make sense if not in the slide-show mode. w Optimized use A radio resource (set of Radio Blocks over one or several RTS) is allocated only when data is being transferred, by establishing and releasing Temporary Block Flow (TBF), that can be presented as micro-connections, each time a data transfer has to be sent over the radio interface. w Radio resource sharing One TS can be shared by several MSs, by dynamic time multiplexing under control of the BSS. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 15
  16. 16. 1 What is GPRS ? 1.5 GPRS Main Concepts (5/5) > Variable useful transmission rate per Radio resource When the radio transmission has a good quality the security can be reduced in order to increase the useful transmission rate Maximum security Minimum security Channel Transmission rate about 22 k with GMSK about 60k with 8PSK (Edge) minimum throughput Introduction to GPRS/EGPRS Maximum throughput 16 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 16
  17. 17. 1 What is GPRS ? 1.6 The benefits of GPRS > GPRS benefits • BSS hardware (included OMC-R) is re-used from GSM • Smooth GPRS introduction • Higher data throughput thanks to EGPRS (EDGE) • Data transfers can billed by volume instead of time • An MS can exchange data by GPRS in parallel with a conventional GSM call (if MS Class A) Introduction to GPRS/EGPRS 17 All rights reserved © 2004, Alcatel w BSS is re-used The same Radio Access Network is re-used, and a Packet Control Unit (PCU) function is implemented in the BSS. w Compared to the GSM BSS same frequency bands same TDMA frame structure same burst structure same frequency hopping laws ... © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 17
  18. 18. 1 What is GPRS ? 1.7 EGPRS > EGPRS is an enhancement of GPRS • allows higher bit rates on the radio interface • achieved by using – – a new modulation (8-PSK) and new coding schemes (MCS-1 to MCS-9) in the MS and the BSS. > The same set of services provided by GPRS is available in EGPRS. Introduction to GPRS/EGPRS 18 All rights reserved © 2004, Alcatel w Shared = in other words: "the radio resources are shared by statistical multiplexing". As in GSM, no subscriber has their own permanent radio resource. w High or low bit rates = more than one time slot per MS or conversely, more than MS on the same TS (one TDMA frame occupies 4.615 ms and is divided into 8 TS or channels). w Maximum instantaneous bit rate provided = 171,2 kbps through the allocation of eight TSs to one subscriber. The stated maximum bit rates are different (according to the BSS release), because different ways of encoding the data, or "coding schemes", are used, which impacts the bit rate over a TS. (cf Annex) w Optimized use:refer to Radio resource allocation in the slides to come + radio resource management in the BSS Chapter.The radio resource allocation is suitable for variable, bursty traffic (downloading Web pages). w Up link (UL) and downlink (DL): It is possible to use a different bandwidth (bit rate) in each transmission direction, whereas in CS (circuit switching) mode, there is a maximum limit of 9,6 kbps, in both directions and at all times. w QoS: Henceforth, QoS parameters are part of subscription data, according to the wide range of services provided to a subscriber. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 18
  19. 19. 1 What is GPRS ? 1.8 Quality of service profile 9 classes 19 classes 5 classes 4 classes 3 classes Peak throughput Class the maximum data rate allowed to the user Throughput class Mean throughput Class maximum data rate during a period Reliability Class acknowledgement of packets Delay Class total delay measured between R or S point and Gi Precedence Class relative importance of service under congestion Introduction to GPRS/EGPRS 19 All rights reserved © 2004, Alcatel w Precedence class According to the class, user data packet can be discarded during the transfer due to a congestion state. 3 classes are defined : any, normal, high w Delay class The delay class depends on the operator network because a measurement is done between the R or S interface (between the Mobile Terminal and the Terminal Equipment) and the Gi interface. For each operator, delay values are different so delay classes are a reference not a strict value. 4 classes are defined : best effort, 1, 2, 3 w Reliability class The reliability means that user data packets are acknwoledged during the transfer. The reliability classes are defined according to the acknowledgement or not of the packet. 5 classes are defined w Throughput class The throughput class is defined by the 2 following parameters: Mean Throughput : 9 classes are defined (from best effort to 111 Kb/s) Peak Throughput : 19 classes are defined (from 8 Kb/s to 2048 Kb/s) © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 19
  20. 20. 1 What is GPRS ? 1.9 Services Media Always-on Fun • Games (Hangman, Poker, …) • Screen Saver • Ring Tone • Horoscope • Biorhythm Directories • Yellow/White Pages • International Directories • Operator Services Mobile Office • Voice (!) • E-mail • Agenda • IntraNet/InterNet • Corporate Applications • Database Access Music • Downloading of music files or video clips Transportation • Flight/train Schedule • reservation Vertical application •Traffic Management •Automation •Mobile branches •Health News (general/specific) • International/National News • Local News • Sport News • Weather • Lottery Results • Finance News… • Traffic Conditions • Itineraries • Nearest Restaurant, Cinema, Chemist, Parking;, ATM ... M-commerce Non physical • on-line Banking • Ticketing • Auction • Gambling…. Introduction to GPRS/EGPRS Location services Physical • on-line shopping • on-line food 20 All rights reserved © 2004, Alcatel w Retrieval services Provide the capability of accessing information stored in data base centers. The information is sent to the user on demand only. An example of one such service in the Internet's World Wide Web (WWW). w Messaging services Offer user-to-user communication between individual users via storage units with store-and-forward mailbox, and/or message handling (e.g., information editing, processing and conversion) functions; w Conversational services Provide bi-directional communication by means of real-time (no store-and-forward) end-to-end information transfer from user to user. An example of such a service is the Internet's Telnet application; w Tele-action services Characterized by low data-volume (short) transactions, for example credit card validations, lottery transactions, utility meter readings and electronic monitoring and surveillance systems. w Distribution services Characterized by the unidirectional flow of information from a given point in the network to other (multiple) locations. Examples may include news, weather and traffic reports, as well as product or service advertisements; w Dispatching services Characterized by the bi-directional flow of information from a given point in the network (dispatcher) and other (multiple) users. Examples include taxi and public utility fleet services; w Conferencing services Provide multi-directional communication by means of real-time (no store-and-forward) information transfer between multiple users. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 20
  21. 21. 1 What is GPRS ? Exercise – True or False ? – – – – – – – – – GPRS is a circuit switching technology The GSS is an IP network Data transfers are often conducted at variable bit rates With a class B mobile, a web page can be downloaded while speaking Billing by volume allows subscribers to be permanently on line Several channels can be assigned to a MS One channel is shared by several MSs EGPRS is GPRS with better Throughput The useful transmission rate depends on the radio quality Time allowed : 5 minutes Introduction to GPRS/EGPRS 21 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 21
  22. 22. 1 What is GPRS ? Evaluation > Objective : to be able to identify the technical and commercial benefit of GPRS Thank you for answering the self-assessment of the objectives sheet Introduction to GPRS/EGPRS 22 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 22
  23. 23. 2 GPRS Operation All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 23
  24. 24. 2 GPRS Operation Session presentation > Objective: to be able to describe the organization of a GPRS network architecture, interfaces and protocols. > Program: • 2.1 Main Entities • 2.2 MS Mobility Management States • 2.3 MS Radio Resource Operating Modes • 2.4 Basic Procedures • 2.5 Charging • 2.6 Security Introduction to GPRS/EGPRS 24 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 24
  25. 25. 2 GPRS Operation 2.1 Main Entities > Overview To PSTN PCU included in BSS BTS AUC BSC EIR circuits CELLS MSC VLR N7 HLR NSS CALL PROCESSING BSS RADIO ACCESS NTP DNS SGSN GGSN To IP Networks IP GPRS BG SGSN DHCP To other operator IP Networks 25 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w PCU functions LLC PDU segmentation / re-assembly into RLC/MAC PDU PDCH scheduling (resource multiplexing) Channel access control (access requests and grants) ARQ function (RLC block Ack / Nak, buffering and retransmission of RLC blocks) Radio channel management (power control, congestion control, broadcast control information). w DNS (Domain Name Server) and DHCP (Dynamic Host Convergence Protocol) w NTP server (Network Time Protocol) for GSN synchronization. In general an NTP application does not run on a dedicated server. The OMC-G can play this role. w HLR (Home Location Register) is involved in MS attachment to the GPRS network (authentication + services subscribed to) © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 25
  26. 26. 2 GPRS Operation 2.1 Main Entities > SGSN and GGSN IP network 1 SGSN1 GGSN1 IP network 1 SGSN2 IP IP network 1 backbone SGSN3 GGSN2 IP network 1 SGSN4 IP network 1 SGSN5 GGSN3 GSS 26 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w The SGSN (Serving GPRS Support Node) stores subscriber data: Subscription information IMSI one or more temporary identities (P-TMSI) zero or more PDP addresses Location information the cell or the RA where the MS is registered the VLR number of the associated VLR (if the Gs interface is implemented) the GGSN address of each GGSN for which an active PDP context exists It also manages: the transfer and routing of user data packets from the GSS towards the BSS the mobility (GPRS attach/detach, data retrieval from the HLR, RA / Cell update) the authentication and encryption (Access control and security) the sessions (PDP context activation/deactivation) The transfer of charging data. w The GGSN (Gateway GPRS Support Node) stores subscriber data received from the HLR and the SGSN: Subscription information IMSI zero or more PDP addresses Location information the SGSN address of the SGSN where the MS is registered It also manages: the allocation and use of dynamic @IP for MS, the tunneling and encryption of user data at Gi interface, the transfer of user data packets, the charging data. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 26
  27. 27. 2 GPRS Operation 2.1 Main Entities > Servers NTP SGSN GGSN Alcatel.fr 256.167.123.34 DNS GPRS BACKBONE DHCP IP add 27 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w DNS Resolve a name into an IP address Use in Mobility procedure w DHCP Provide dynamically IP addresses Split Users into pool of IP addresses w NTP Provide one time reference for all the network Have a very precise time reference Synchronization from satellite © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 27
  28. 28. 2 GPRS Operation 2.1 Main Entities > Border gateway VISITED PLMN BSS SGSN GGSN VPLMN BG MS INTER PLMN NETWORK HOME PLMN BG HPLMN GGSN PDN 28 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w Border Gateway functions Inter-PLMN routing and forwarding of user packets (IP router) Security functions (firewall, access-list filtering) w Connection of two Border Gateways Via a private or public IP network, through the Gp interface. w Choice of GGSN If a subscriber wants to access an Intranet (PDN) in his home country, from the visited PLMN, the selected GGSN is the one from the home PLMN For Internet access a GGSN in the visited country could be used. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 28
  29. 29. 2 GPRS Operation 2.1 Main Entities > Interfaces Um Mobile GPRS BSS A MSC Gs Gb SMSGMSC HLR Gd Gr Gc SGSN Gn Signaling + data Signaling Gi SGSN GGSN PDN GPRS network 29 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w Signaling protocols MAP/TCAP/SCCP/MTP on Gr, Gd and Gc, GTP/UDP/IP on Gn, BSSAP+/SCCP/MTP on Gs, GMM/SM/LLC on Gb/Um. w Gc interface Used for network-requested PDP contexts activation (GGSN asks the HLR for SGSN routing information). w Gs interface Defines the Network Mode of Operation I (NMOI). It allows to perform LA + RA combined Location Update, and PS and CS paging coordination (refer to ANNEX). w Gr interface Exchange of subscription information at GPRS attachment phase w Additional interfaces Gf (to the EIR) Gd to deliver the SMS to the mobiles via the GPRS network (SGSN option and subscriber feature) © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 29
  30. 30. 2 GPRS Operation 2.2 MS Mobility Management States Autonomous cell reselection > MS MM states READY timer expiry Stand-by Location at CELL level Location at RA level PDU transmission Ready GPRS Attach Autonomous cell reselection NCO Or controled by network NC 2 ( In paquet transfert mode ) GPRS Detach Idle Introduction to GPRS/EGPRS 30 All rights reserved © 2004, Alcatel w IDLE (GPRS) State In GPRS IDLE state, the subscriber is not attached to GPRS mobility management. The MS and SGSN contexts hold no valid location or routeing information for the subscriber. The subscriber-related mobility management procedures are not performed. Data transmission to and from the mobile subscriber and the paging of the subscriber is not possible. The GPRS MS is seen as not reachable in this case. In order to establish MM contexts in the MS and the SGSN, the MS shall perform the GPRS Attach procedure. w STANDBY State In STANDBY state, the subscriber is attached to GPRS mobility management. Pages for data or signalling information transfers may be received. It is also possible to receive pages for the CS services via the SGSN. Data reception and transmission are not possible in this state. The MS performs GPRS Routeing Area (RA) and GPRS cell selection and re-selection locally. The MS executes mobility management procedures to inform the SGSN when it has entered a new RA. The MS does not inform the SGSN on a change of cell in the same RA. Therefore, the location information in the SGSN MM context contains only the GPRS RAI for MSs in STANDBY state. The MS may initiate activation or deactivation of PDP contexts while in STANDBY state. A PDP context shall be activated before data can be transmitted or received for this PDP context. w READY State In READY state, the SGSN MM context corresponds to the STANDBY MM context extended by location information for the subscriber on the cell level. The MS performs mobility management procedures to provide the network with the actual selected cell. GPRS cell selection and re-selection is done locally by the MS, or may optionally be controlled by the network. An identifier of the cell, the Cell Global Identity including RAC and LAC, is included in the BSSGP header of the data packet from the MS; see GSM 08.18 [21]. The MS may send and receive PDP PDUs in this state. The network initiates no GPRS pages for an MS in READY state. Pages for other services may be done via the SGSN. The SGSN transfers downlink data to the BSS responsible for the subscriber's actual GPRS cell. The MS may activate or deactivate PDP contexts while in READY state. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 30
  31. 31. 2 GPRS Operation 2.3 MS Radio Resource Operating Modes > MS RR operating modes vs MS MM states RR Packet transfer mode MM Packet idle mode Ready Packet idle mode Standby > Packet idle mode In packet idle mode no Temporary Block Flow. Upper layers can require the transfer of a LLC PDU which, implicitly, may trigger the establishment of TBF and transition to packet transfer mode. > Packet transfer mode In packet transfer mode, the mobile station is allocated radio resource providing a Temporary Block Flow (TBF) on one or more physical channels. Continuous transfer of one or more LLC PDUs is possible. Concurrent TBFs may be established in opposite directions. Transfer of LLC PDUs in RLC acknowledged or RLC unacknowledged mode is provided. Introduction to GPRS/EGPRS 31 All rights reserved © 2004, Alcatel w Packet idle mode While operating in packet idle mode, a mobile station belonging to GPRS MS class A may simultaneously enter the different RR service modes. A mobile station belonging to either of GPRS MS class B or C leaves both packet idle mode and packet transfer modes before entering dedicated mode, group receive mode or group transmit mode. w Packet transfer mode When selecting a new cell, mobile station leaves the packet transfer mode, enters the packet idle mode where it switches to the new cell, read the system information and may then resume to packet transfer mode in the new cell. While operating in packet transfer mode, a mobile station belonging to GPRS MS class A may simultaneously enter the different RR service modes. A mobile station belonging to either of GPRS MS class B or C leaves both packet idle mode and packet transfer modes before entering dedicated mode, group receive mode or group transmit mode. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 31
  32. 32. 2 GPRS Operation 2.4 Basic Procedures > IP overview http ftp wap smtp http ftp smtp wap gtp tcp 1 1 tcp Routers ip ip SGSN ip ip ip IP network GGSN Introduction to GPRS/EGPRS 32 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 32
  33. 33. 2 GPRS Operation 2.4 Basic Procedures nK bytes MESSAGE L4 L3 L2 x 4k TCP packets TCP 4K bytes PACKET IP TCP IP TCP 4K bytes PACKET Y Datagrams IP IP IP TCP Introduction to GPRS/EGPRS Z Ethernet 1.5k frames 33 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 33
  34. 34. 2 GPRS Operation 2.4 Basic Procedures IP / X25 SNDCP SNDCP LLC HEADER DATAS HEADER DATAS HEADER DATAS HEADER DATAS CRC Max 1600Bytes SGSN to MS RLC/ PCU HEADER TRE / CCU 456 456 AIR INTERFACE 57 X 8 57 57 Introduction to GPRS/EGPRS 34 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 34
  35. 35. 2 GPRS Operation 2.4 Basic Procedures > Transmission plane TCP HTTP FTP SMTP Application IP IP relay SNDCP SNDCP LLC LLC GTP GTP UDP UDP IP IP L2 L2 Physical layer Physical layer relay RLC RLC BSSGP MAC MAC (Frame Relay) Physical layer Physical layer (Frame Relay) Physical layer Um Introduction to GPRS/EGPRS L2 MAC BSSGP Physical layer BSS (with PCU) MS IP SGSN Gb Physical layer GGSN Gn Gi 35 All rights reserved © 2004, Alcatel w GTP (GPRS Tunnelling Protocol) tunnels user data between GPRS Support Nodes in the backbone network. The GPRS Tunnelling Protocol shall encapsulate all PDP PDUs. w UDP (User Datagram Protocol) carries GTP PDUs for protocols that do not need a reliable data link (e.g., IP), and provides protection against corrupted GTP PDUs. w IP (Internet Protocol) is the backbone network protocol used for routing user data and control signalling. The backbone network may initially be based on the IPv4. Ultimately, IPv6 shall be used. w SNDCP (SubNetwork Dependent Convergence Protocol ) maps network-level characteristics onto the characteristics of the underlying network. w LLC (Logical Link Control) provides a highly reliable ciphered logical link. LLC shall be independent of the underlying radio interface protocols in order to allow introduction of alternative GPRS radio solutions with minimum changes to the NSS. w Relay. In the BSS, this function relays LLC PDUs between the Um and Gb interfaces. In the SGSN, this function relays PDP PDUs between the Gb and Gn interfaces. w BSSGP (Base Station System GPRS Protocol) conveys routing and QoS-related information between the BSS and the SGSN. BSSGP does not perform error correction. w (NS) Network Service transports BSSGP PDUs. NS is based on the Frame Relay connection between the BSS and the SGSN, and may - multi-hop and traverse a network of Frame Relay switching nodes. w RLC/MAC (Radio Link Control / Medium Access Control). The Radio Link Control function provides a radio-solutiondependent reliable link. The Medium Access Control function controls the access signalling (request and grant) procedures for the radio channel, and the mapping of LLC frames onto the GSM physical channel. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 35
  36. 36. 2 GPRS Operation 2.4 Basic Procedures > MS high protocol layers GMM/SM SMS IP NSAPIi SNDCP TLLI LLC NSAPI TLLI NSAPI Radio layers 36 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w SNDCP (Sub-Network Dependent Convergence Protocol) Data compression, segmentation of large packets, recognition of PDP-PDU sessions (according to their NSAPI), inclusion of QoS (use of SAPIs on the LLC link). w NSAPI (Network Service Access Point Identifier) This is used for a particular MS to distinguish different PDP contexts (= sessions) by the PDP-type: X.25 or IP, or mainly by the APN to be reached, or by the required QoS. w LLC (Logical Link Control) Provides a safe link, encrypted and independent of the physical bearer, independent to BSS brand. w TLLI (Temporary Logical Link Identity) Identifies a logical link with the MS (one TLLI per MS) w GMM/SM (GPRS Mobility Management / Session Management) MS-SGSN signaling protocol for Gprs Mobility Management/ Session Management w SMS (Short Message Service) © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 36
  37. 37. 2 GPRS Operation 2.4 Basic Procedures > HLR GPRS data For each MS NMC-NSS ¨IMSI & MSISDN ¥ network access mode : GPRS | NSS | both ¥ subscribed « PDP contexts » (maximum of n) : • PDP type : IP | PPP • [PDP address (IP@) ] MS HLR • Access point name (APN) or * (= wild card) n times • APN accessible through FPLMN-GGSN ? • QoS profile • etc ... HPLMN Introduction to GPRS/EGPRS 37 All rights reserved © 2004, Alcatel w PDP address Almost always empty. The network then dynamically assigns (using a DHCP server) an IP address to the subscriber when he activates his PDP context (seen later). w PDP contexts Each PDP context can be considered as a BS (basic service = telephony, fax, etc). A PDP context is a dialog session with an external IP network, identified with an APN. It is not always mandatory to subscribe (in the HLR) to PDP contexts, access to some networks is free. For a user, the traffic of his different sessions will be recognized in the messages by the use of different NSAPIs. A user can declare one of his PDP contexts as the default. w APN (Access Point Name) The APN represents an IP network. An APN has two parts: the APN-Network Id (example: wanadoo.fr) and the APN-oper Id (example: mnc...gprs) Examples of APN: wanadoo.fr.mnc001.mcc208.gprs, APN = * (wildcard) potentially authorizes the MS to activate any APN. w Valid APN Boolean, if YES, indicates that this APN can be reached through the GGSN of the visited FPLMN. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 37
  38. 38. 2 GPRS Operation 2.4 Basic Procedures > GPRS attachment HLR Update_loc_ack() MS_authentication_procedure  GGSN ~ } Ž Œ Insert_subs_data() PLMN N7 Update_loc_req() Authent_info_req() Attach-Request (IMSI) | Authent_info_respq)  SGSN Attach_resp (P_TMSI) GPRS IP backbone Attach_complete () € BSS 38 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w Attach Request. The attach_request message is placed in an LLC frame. x The MS sends its IMSI. w Authentication The SGSN gets the “authentication triplets” from the HLR: triplets request message y triplets response message z The SGSN performs the “authentication procedure” with the MS: { triplets request message y triplets response message z w Location Update The SGSN performs the “location_update procedure” with the HLR: location_update request message | the HLR transfers the MS_subscription data to the SGSN } the HLR terminates the location_update procedure ~ w Attach Complete The SGSN terminates the attach_procedure with the MS : attach_accept message  (with a new P_TMSI allocation) attach_complete message € (since a new P_TMSI has been allocated) © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 38
  39. 39. 2 GPRS Operation 2.4 Basic Procedures > GPRS attachment After a GPRS_Attach procedure The mobile is « connected » to the serving SGSN TLLI1 GGSN 1 SGSN 1 PDN 1 GPRS IP backbone SGSN 2 LLC layer Introduction to GPRS/EGPRS GGSN 2 PDN 2 GPRS - CN 39 All rights reserved © 2004, Alcatel w Attached MS After running the attach procedure, the MS is “GPRS_attached”: a logical connection is established between the MS and the SGSN connection established between the peer LLC layers in the MS and the SGSN this connection is identified by the TLLI (Temporary Logical Link Identity) this logical connection remains established until the MS detaches the MS can now access to GPRS services and is reachable for GPRS services © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 39
  40. 40. 2 GPRS Operation 2.4 Basic Procedures > PDP context activation DNS DHCP 2 Activate_PDP_req (PDN2) PLMN 4 Œ TLLI1 GGSN PDN 1 GPRS SGSN backbone GGSN Activate_PDP_resp(@IP_MS) } PDN 2 Create_PDP_req (PDN2) 3 BSS 5 Create_PDP_resp (@IP_MS) GPRS Core Network Introduction to GPRS/EGPRS 40 All rights reserved © 2004, Alcatel w MS IP address In case of IP PDP_type access with no additional mobile authentication procedure, the MS IP address is provided by the PLMN, using either the subscription data, or the backbone DHCP server. No additional user authentication is needed on top of the GPRS authentication mechanisms (i.e. using IMSI and authentication triplets) w PDP Context Activation Œ MS requests for a PDP_context activation, providing the name of target Packet Data Network (PDN2 parameter).  SGSN queries the backbone Name Server (here DNS) to identify the GGSN giving access to the Data Network PDN2 (here GGSN2). Ž SGSN sends a Create_PDP message to the corresponding GGSN2, in order to setup a GTP tunnel.  GGSN2 allocates an IP address to the MS (@IP_MS), using the backbone DHCP server.  GGSN2 acknowledges the Create_PDP message to the SGSN, returning the @IP_MS allocated to the MS. ‘ SGSN acknowledges the Activate_PDP message to the MS, with the allocated @IP_MS. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 40
  41. 41. 2 GPRS Operation 2.4 Basic Procedures > PDP context activation Authentication and accounting DNS 2 PLMN Activate_PDP_req (PDN2) RADIUS Œ TLLI1 GGSN SGSN 4 GPRS backbone Activate_PDP_resp(@IP_MS) } ISP INTRANET GGSN Create_PDP_req (PDN2) 3 BSS 6 Create_PDP_resp (@IP_MS) GPRS Core Network 5 DHCP Address allocation Introduction to GPRS/EGPRS 41 All rights reserved © 2004, Alcatel w MS address IP PDP_type access with mobile authentication via a RADIUS. The address allocation server (i.e. DHCP) and/or authentication server (i.e. RADIUS) may be located within the PLMN or in the ISP/Intranet network. Non-transparent access is aimed for corporate intranet access, where additional user authentication is often required. w PDP Context Activation The authentication data are piggybacked in the Protocol Configuration Options (PCO) field of the PDP context activation messages Œ and ’. Œ ,  , Ž same as for IP PDP_type in transparent access.  GGSN performs the user authentication towards a RADIUS server.  GGSN allocates an @IP to the MS using the intranet/ISP DHCP server. ‘, ’ same as for a PDP context in transparent access. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 41
  42. 42. 2 GPRS Operation 2.4 Basic Procedures > PDP context activation after PDP_context_activation procedures LLC layer by the GTP layer TLLI1 SGSN TID 1 = IMSI + NSAPI 1 1 TID 2 =I MS GPRS IP I+ backbone NS AP SGSN 2 GGSN 1 PDN 1 I2 GGSN 2 PDN 2 GPRS - CN Introduction to GPRS/EGPRS 42 All rights reserved © 2004, Alcatel w User data transfer In order to achieve a proper transfer of User Data, two main protocols are used: GTP (between GGSN and SGSN) and LLC (between SGSN and MS), and two types of logical connections are established: MS <-> SGSN. Logical Link used for signaling and data transfer, created at GPRS attach (unique per MS), identified by a TLLI value; SGSN <-> GGSN. Created with the activation of PDP context = when opening a session (several per MS), identified each by a TID value. w TLLI (Temporary Logical Link Identity) Identifies uniquely a MS attached to the GPRS core network (Standby or Ready state). w TID (Tunnel Identity) Identifies a logical connection ("tunnel") between GGSN and SGSN (for each session of each MS). TID= IMSI+NSAPI. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 42
  43. 43. 2 GPRS Operation 2.4 Basic Procedures > PDP context activation after PDP_context_activation procedures LLC layer by the GTP layer TLLI1 SGSN TID 1 = IMSI + NSAPI 1 1 TID 2 =I MS GPRS IP I+ backbone NS AP SGSN 2 GGSN 1 PDN 1 ul/dl data_transfers I2 GGSN 2 PDN 2 GPRS - CN Introduction to GPRS/EGPRS 43 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 43
  44. 44. 2 GPRS Operation 2.4 Basic Procedures > User data transfer SGSN over the Gi interface GGSN over the Gn interface @ MS @server U-data @ MS @server U-data MS U-data within the MS @ggsn @sgsn UDP header @ MS @server GTP header GTP header @server @ MS UDP header @sgsn @ggsn PDN U-data server @server @ MS @server @ MS U-data Introduction to GPRS/EGPRS U-data 44 All rights reserved © 2004, Alcatel w User data transfer Data are transferred from header translation, then encapsulation in underlined protocol data unit. At the GGSN, the IP address of the MS is used to retrieve a PDP context and therefore a TID and the address of the current SGSN. At the SGSN, the TID is used to work out the NSAPI and the IMSI (therefore the TLLI). If the MS is ready, no need for paging because the MS is located to the exact cell. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 44
  45. 45. 2 GPRS Operation 2.5 Charging > Charging process CCBS FTP CG GTP MS BSS SGSN GPRS TLLI GGSN BACKBONE Attachment PDN G_CDR M_CDR S_CDR PDP CONTEXT ACTIVATION AND DATA TRANSFERT Introduction to GPRS/EGPRS 45 All rights reserved © 2004, Alcatel w CDR (Call Detail Record) CDRs are used for subscriber charging, statistics and location purposes. Three types of CDR are managed within the GPRS backbone: M-CDR related to the GPRS mobility of a mobile station S-CDR related to PDP-contexts activation and data transfers as seen by the SGSN G-CDR related to PDP-contexts activation and data transfers as seen by the GGSN CDRs, generated by the xGSN, are then sent to the CG (Charging Gateway) : periodically, using reliable transfers (GTP over TCP) The CG forwards those CDRs to external CCBS (Customer Care and Billing System) w CDR content Here are the main information in the CDR : IMSI location information (LAC + RAC + Cell) APN PDP-context identifier PDP-context start time and duration negotiated QoS volume of data sent / received source and destination PDP addresses, …. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 45
  46. 46. 2 GPRS Operation 2.5 Charging > Charging process VISITED PLMN TLLI SGSN VPLMN BG BSS MS CG CCBS INTER PLMN NETWORK HOME PLMN S_CDR CCBS BG HPLMN CG GGSN PDN G_CDR 46 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w Charging data collection for inter-PLMN charging Use of G_CDR and S-CDR as specified by GSM 12.15 Inter-operator agreement to transfer between Billing Systems © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 46
  47. 47. 2 GPRS Operation 2.6 Security 1- Secured network access • Authentication of MSs and confidentiality of their identity • Possibility of encrypting user data • Possibility of verifying IMEI with an EIR (Gf) 2- Secured backbone IP network Firewall = application-level filtering Filtering by access lists (in the GGSNs) GPRS Network Public Internet 3- Secured intranet access APN with mandatory subscription APN with access lists APN with tunneling on Gi (IPsec) Introduction to GPRS/EGPRS 47 All rights reserved © 2004, Alcatel w Authentication and confidentiality As in GSM, by security triplets and the use of the TLLI/P_TMSI instead of the IMSI. w Encryption The LLC frame is encrypted, so encryption from the MS to the SGSN and not just on Um. w Firewall Filtering function installed on routers (ex: GGSN). Packets are rejected by filtering at application level (for example: in http, some URLs are barred). Also makes it possible to hide the IP addresses of MSs and backbone entities from external hosts (Network Address Translation function). w Access Lists (IP addresses lists) A function of Cisco routers (and therefore of GGSNs). Each APN is linked to two lists of IP addresses to be checked during the PDP context activation phase (calling address and called address in both UL and DL directions). These lists are therefore used to protect access to the operator's backbone IP, but also to filter the access to external PDNs. At the GGSN, some APNs can be declared "with mandatory subscription" (at the HLR) and therefore inaccessible to other MSs. w Tunneling Several ways: by IPsec (Secured IP) = IP version in which the user data is encrypted (IP datagrams payload but not their header). Or by Generic Routing Encapsulation (GRE) by PPTP (Point-To-Point Tunneling Protocol). Refer to ANNEX for PPP Tunneling. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 47
  48. 48. 2 GPRS Operation Exercise (1/3) – True or False? – The GGSN reads the header of user packets arriving from the PDN – The GPRS HLR knows the location of an MS to the nearest RA – With each web page downloaded, a new PDP context must be activated – A CDR is generated for each packet sent or received – The SGSN can be considered as PMSC and PVLR – A TLLI is a virtual connection between a GPRS attached mobile and the GGSN Time allowed : 5 minutes Introduction to GPRS/EGPRS 48 All rights reserved © 2004, Alcatel w PMSC: Packet MSC. w PVLR: Packet VLR. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 48
  49. 49. 2 GPRS Operation Exercise (2/3) – True or False ? – The Charging gateway provides a single interface towards the billing centers – No need for paging to send a packet to a mobile in the "Ready" state – Attachment to the network does not involve GGSN Time allowed : 5 minutes Introduction to GPRS/EGPRS 49 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 49
  50. 50. 2 GPRS Operation Exercise (3/3) – What interfaces of the GPRS NSS does a packet cross from a PDN to an MS? – Why , theoretically, is an RA smaller than an LA? Time allowed : 5 minutes Introduction to GPRS/EGPRS 50 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 50
  51. 51. 2 GPRS Operation Evaluation > Objective : to be able to describe the organization of a GPRS network : architecture, interfaces, protocols,… Thank you for answering the self-assessment of the objectives sheet Introduction to GPRS/EGPRS 51 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 51
  52. 52. 3 The Base Station Subsystem All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 52
  53. 53. 3 The Base Station Subsystem Session presentation > Objectives : • To be able to briefly describe the data interchange mechanisms through the BSS > Program : • 3.1 3GPP Position • 3.2 Alcatel’s Choice • 3.3 Layered Model • 3.4 Gb Interface • 3.5 Radio Interface Introduction to GPRS/EGPRS 53 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 53
  54. 54. 3 The Base Station Subsystem 3.1 3GPP Position > PCU function BSS BTS CCU BSC SGSN PCU BTS CCU BSC BSS SGSN PCU BTS BSC BSS PCU CCU Introduction to GPRS/EGPRS SGSN 54 All rights reserved © 2004, Alcatel w PCU functions RLC and MAC layers: LLC frame transportation (segmentation/reassembly), Gb interface end point, network access functions (radio resource management), radio channel management (power control, congestion control, etc). w CCU functions encoding suited to radio channels, radio measurements (receive quality, signal level, "timing advance" management). © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 54
  55. 55. 3 The Base Station Subsystem 3.2 Alcatel’s Choice > PCU function MFS is just the name of the rack containing PCU functions Abis Ater GSL BTS BSC Gb MFS SGSN PCU CCU BSS LLC Transmission check between SGSN and MS RLC Transmission check between PCU and MS GCH transmission check between PCU and TRE Introduction to GPRS/EGPRS 55 All rights reserved © 2004, Alcatel w The Multi BSS Fast packet Server (MFS): w MFS is just the namee of the rack containing PCU functions performs the GPRS Packet Control Unit (PCU) functions (3GPP 03.60 standard), manages the Gb interface with the GPRS & EGPRS core network, performs the Serving Mobile Location Center (SMLC) functions, manages the SAGI interface with the A-GPS server. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 55
  56. 56. 3 The Base Station Subsystem 3.3 Layered Model > User plane IP SNDCP SM GMM SM GMM LLC SNDCP LLC PCU RLC RLC MS Frame relay Frame relay L2-GCH L1-GCH Physical layer Physical layer relay Physical L2-GCH layer L1-GCH Um BTS Introduction to GPRS/EGPRS BSSGP BSS GP MAC MAC Physical layer relay Abis/Ater MFS Gb SGSN 56 All rights reserved © 2004, Alcatel w For GPRS TRAFFIC, the BSS simply relays the LLC frames between the MS and the SGSN. w BSSGP = BSS Gprs Protocol. Functions: to relay LLC frame over the Gb, with no guarantee of integrity (relaying user data and GMM / SM messages : session, RA_update and paging procedures). Conceals the FR layers for the LLC layer. SGSN-MFS signaling = management of Gb interface objects (flush, paging, resume suspend, LLC-discarded and other procedures). cell-SGSN traffic management (identified by BssgpVCs): in particular cell update management (in the same RA): the BSSGP header always indicates the current cell so if a "ready" MS moves into a new cell, then the SGSN stores this new cell and sends all the unacknowledged LLC_PDUs to it (DL). w The concept of handover has no meaning in packet switching (GPRS). There is no "circuit" to re-establish! w RLC = Radio Link Control. (Provides a safe link for transporting LLC-PDUs in acknowledged or unacknowledged mode, LLC-PDU segmentation into blocks and reassembly, management of TBF contexts. RLC depends on the physical bearer: data encoding, error control and flow control suited to GSM channels. w MAC = Medium Access Control. Multiplexing of RLC frames onto PDCH (transfer of blocks over the different PDCHi). Including traffic sharing over several TSs or, conversely, the use of one TS for several users. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 56
  57. 57. 3 The Base Station Subsystem 3.3 Layered Model > Signaling plane BSCGP BSCGP L2-GSL L1-GSL L2-GSL L1-GSL RRM RRM relay relay physical layer physical layer MS Um BTS Abis BSC Ater MFS Gb 57 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w BSCGP protocol administration interface of Radio Resource management : (de)allocation of PDCH and MPDCH within a cell activation / release of PDCH System control information: BSC reset procedure cell and GIC group state management Radio signalling : GSM / GPRS paging, GPRS access procedure w RMM protocol dynamic allocation of Radio Resources to a MS : radio blocks from one or several PDCH for uplink or downlink data transfers © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 57
  58. 58. 3 The Base Station Subsystem 3.4 Gb Interface > Managed entities BSS side GPRS Core Network side BVCI=2 PCM BC BVCI=2 BVCI=1 BVCI=3 BSC1 NSVC1 PCM PVC BC BVCI=1 NSE1 NSE1 PCM BC NSVC2 PCM PVC BC BVCI=3 F.R Network PCM BC BVCI=5 BVCI=4 BVCI=6 BSC2 NSVC3 BVCI=5 BVCI=4 PCM PVC BC NSE2 NSE2 PCM BC NSVC4 PCM PVC BC BVCI=6 SGSN Introduction to GPRS/EGPRS 58 All rights reserved © 2004, Alcatel w For GPRS TRAFFIC, the BSS simply relays the LLC frames between the MS and the SGSN. w BSSGP = BSS Gprs Protocol. Functions: to relay LLC frame over the Gb, with no guarantee of integrity (relaying user data and GMM / SM messages : session, RA_update and paging procedures). Conceals the FR layers for the LLC layer. SGSN-MFS signaling = management of Gb interface objects (flush, paging, resume suspend, LLC-discarded and other procedures). cell-SGSN traffic management (identified by BssgpVCs): in particular cell update management (in the same RA): the BSSGP header always indicates the current cell so if a "ready" MS moves into a new cell, then the SGSN stores this new cell and sends all the unacknowledged LLC_PDUs to it (DL). w The concept of handover has no meaning in packet switching (GPRS). There is no "circuit" to re-establish! w RLC = Radio Link Control. (Provides a safe link for transporting LLC-PDUs in acknowledged or unacknowledged mode, LLC-PDU segmentation into blocks and reassembly, management of TBF contexts. RLC depends on the physical bearer: data encoding, error control and flow control suited to GSM channels. w MAC = Medium Access Control. Multiplexing of RLC frames onto PDCH (transfer of blocks over the different PDCHi). Including traffic sharing over several TSs or, conversely, the use of one TS for several users. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 58
  59. 59. 3 The Base Station Subsystem 3.4 Gb Interface > Protocols BSS side GPRS Core Network side BVCI=2 BVCI=1 BSC1 BVCI=3 BSS GPRS Protocol BSS GPRS Protocol BVC (BSSGP) (BSSGP) BVCI=5 BVCI=4 BVCI= 6 BSC2 NSE Network Service Control Network Service Control (NSC) NS-VC (NSC) Sub-Network Service PVC Sub-Network Service (SNS) Physical layer PCM Packet Control Unit function (PCU) Introduction to GPRS/EGPRS (SNS) BC PCM Physical layer Frame Relay SGSN 59 All rights reserved © 2004, Alcatel w For GPRS TRAFFIC, the BSS simply relays the LLC frames between the MS and the SGSN. w BSSGP = BSS Gprs Protocol. Functions: to relay LLC frame over the Gb, with no guarantee of integrity (relaying user data and GMM / SM messages : session, RA_update and paging procedures). Conceals the FR layers for the LLC layer. SGSN-MFS signaling = management of Gb interface objects (flush, paging, resume suspend, LLC-discarded and other procedures). cell-SGSN traffic management (identified by BssgpVCs): in particular cell update management (in the same RA): the BSSGP header always indicates the current cell so if a "ready" MS moves into a new cell, then the SGSN stores this new cell and sends all the unacknowledged LLC_PDUs to it (DL). w The concept of handover has no meaning in packet switching (GPRS). There is no "circuit" to re-establish! w RLC = Radio Link Control. (Provides a safe link for transporting LLC-PDUs in acknowledged or unacknowledged mode, LLC-PDU segmentation into blocks and reassembly, management of TBF contexts. RLC depends on the physical bearer: data encoding, error control and flow control suited to GSM channels. w MAC = Medium Access Control. Multiplexing of RLC frames onto PDCH (transfer of blocks over the different PDCHi). Including traffic sharing over several TSs or, conversely, the use of one TS for several users. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 59
  60. 60. 3 The Base Station Subsystem 3.5 Radio Interface 1/8 > GPRS / EGPRS throughput EGPRS Modulation Maximum rate per PDCH (kb/s) CS4 CS3 CS2 CS1 GMSK GMSK GMSK GMSK 21.4 15.6 13.4 9.05 MCS9 MCS8 MCS7 MCS6 MCS5 8-PSK 8-PSK 8-PSK 8-PSK 8-PSK 59.2 54.4 44.8 29.6 / 27.2* 22.4 MCS4 MCS3 GMSK GMSK 17.6 14.8 / 13.6* MCS2 MCS1 GPRS Coding Scheme GMSK GMSK 11.2 8.8 * in case of padding Introduction to GPRS/EGPRS 60 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 60
  61. 61. 3 The Base Station Subsystem 3.5 Radio Interface 2/8 > Coding schemes Bad radio condition Max security CS1 Good radio condition Min security CS2 CS3 Max number of bits for user data Maximum number of bits to have security BETTER USER BIT RATE POOR USER BIT RATE Introduction to GPRS/EGPRS CS4 61 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 61
  62. 62. 3 The Base Station Subsystem 3.5 Radio Interface 3/8 > GMSK / 8-PSK modulations 1 1 bit per Symbol 0 1 1 Gross bit rate per carrier GMSK 270 kb/s GMSK One TS 142 symbols 142 Bits ONE TS One TS 142 symbols 426 Bits ONE TS 001 3 bitS per Symbol 101 011 001 8-PSK 810 kb/s 8-PSK 8 PSK has 3times more capacity than GMSK Introduction to GPRS/EGPRS 62 All rights reserved © 2004, Alcatel w Transmission and reception data flows are the same for GPRS and EGPRS, except for EGPRS MCS-9, MCS-8 and MCS-7, where 4 normal bursts carry 2 RLC blocks (1 RLC block within 2 bursts for MCS-9 and MCS-8). w Radio blocks are transported on the air interface (Um) over 4 consecutive normal bursts of the TDMA frame. w The GMSK normal burst is composed of 156.25 symbols (1 bit for 1 symbol): 6 tail symbols, 26 training sequence symbols, 114 encrypted symbols, 2 stealing flags (2 symbols), 8.25 guard period (symbols). For GMSK, the radio blocks are transported by 114 x 4 = 456 symbols. w The 8-PSK normal burst is composed of 156.25 symbols (3 bits for 1 symbol): 6 tail symbols, 26 training sequence symbols, 116 encrypted symbols (there is stealing flags), 8.25 guard period (symbols). For 8-PSK, the radio blocks are transported by 116 x 4 = 456 symbols. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 62
  63. 63. 3 The Base Station Subsystem 3.5 Radio Interface 4/8 > Transmission Rate with 8 PSK modulation CHANNEL Bad radio condition Good radio condition MCS9 MCS8 MCS7 MCS6 MCS1 8,8k MCS2 MCS3 11,2k MCS4 14,8k 17,6k MCS5 22,4k 29,6k Maximum number of bits to have security Introduction to GPRS/EGPRS 44,8k 54,4k 59,2k Max number of bits for user data 63 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 63
  64. 64. 3 The Base Station Subsystem 3.5 Radio Interface 5/8 > Impact of EGPRS (Edge) on terrestrial transmissions in BSS CS1 about 9K PDCH BTS TRX GMSk and Not a good transmission BSC 16k resource relay Abis MFS 16k resource PCU Ater MCS9 ABOUT 59K BTS PDCH TRX BSC Extra capacity relay MFS Extra capacity Extra capacity Extra capacity 8PSK good transmission Extra capacity Extra capacity Extra capacity PCU Extra capacity Introduction to GPRS/EGPRS 64 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 64
  65. 65. 3 The Base Station Subsystem 3.5 Radio Interface 6/8 > Resources allocation according to the MCS MCS n PDCH BTS TRX Extra capacity BSC Extra capacity relay Extra capacity Extra capacity Extra capacity MFS PCU Extra capacity QUALITY OF TRANSMISSION LOT OF BITS LOST INCREASE SECURITY DECREASE USEFUL TRANSMISSION RATE PDCH BTS TRX Extra capacity BSC Extra capacity relay Extra capacity Extra capacity Extra capacity MFS PCU Extra capacity MCS n-1 Can be allocated to another PDCH Introduction to GPRS/EGPRS Can be allocated to other PDCH 65 All rights reserved © 2004, Alcatel w When the operator decide that the TRX will run MCS n all the terrestrial resources will be allocated , but if the quality of the radio transmission is bad the PCU decides to increase the security on the air interface, the useful transmission rate on the PDCH will be decreased and less capacity will be needed on the terrestrial transmission . w The resource which is not used a that time can be allocated to another TRX if needed at BTS level w The RLC blocks coming from different are multiplexed on the common resource for all the PDCH in the TRX which is called M EGCH (Multiplexed EGCH) © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 65
  66. 66. 3 The Base Station Subsystem 3.5 Radio interface 7/8 > UL transfer TBF start of TBF1 MS end of TBF1 TBF2 MAC network TBF3 TBF4 fULi time Packet Channel Request Packet Resource Assignment (list of PDCHi, token=T,TFIk) PCU MS starts listening to all DL blocks token value on the allocated PDCHi DL PDCHi N Ø Ø T T Ø T Ø T T T Ø TFIk TFIk Ø TFIk Ø TFIk TFIk TFIk in block b token =T ? Y SEND on block b+1 (TFIk) UL PDCHi ? Ø Ø Introduction to GPRS/EGPRS 66 All rights reserved © 2004, Alcatel w This slide demonstrate that the radio resources (blocks) are used only when data need to be transferred (LLC-PDU) : dynamic radio resource allocation. As a matter of fact, an MS shall specify its radio resource request at initiation of each TBF for a better optimization of radio resource & MS capabilities. w A TBF (the blue shape) comprises one or more consecutive LLC-PDUs. w Temporary (Block) Flow Identity = TLLI + sequential number, used by the network to recognize data from different MSs. Identifies uniquely a TBF in one direction within a cell. The blocks are dynamically allocated upon the use of a token (Uplink State Flag) allocated to the MS at TBF establishment. Any DL block includes a USF in the header. The mobile "listens" to the PDCHi assigned, when block b (in DL) contains USF = T, the MS shall send one PDTCH in UL on block b+1 on the UL PDCHi. w The theoretical maximum of 160 kbit/s is given for one MS which would have 8 PDCHs of 21.4 kbit/s each. Those MS are yet to be available on the market place. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 66
  67. 67. 3 The Base Station Subsystem 3.5 Radio interface 8/8 > DL transfer PCU SGSN PS Paging Paging Request ("packet") MS PDU MS IN STANB BY MODE Packet Paging Response UL TBF: refer to previous slide MS IN READY MODE Packet Resource Assignment (list (PDCHj),TFIz) MS starts listening to all DL blocks TFI value on the allocated PDCHj DL PDCHj Ø Ø Z Z Ø Z Ø Z Z N in block b, TFI=TFIz ? Y The MS consumes the content of block b Introduction to GPRS/EGPRS 67 All rights reserved © 2004, Alcatel w In DL, each time an LLC-PDU is received, if there is no TBF in progress, it is essential to “establish" one. w To respond to the paging, the MS needs to send a "paging response" to the SGSN (GMM) encapsulated in an LLC_PDU. This response is carried by an UL TBF. w Upon reception of the Paging response, the SGSN can send the DL PDU (LLC frame) to the MS through the MFS. The MFS shall establish a DL TBF with the MS. w DL TBF: each block of the DL TBF are identified by the DL TFI = TFIz w After completion of the TBF establishment phase, the MS listen to all the DL blocks on the allocated PDCHs and keeps the blocks tagged with the TFIz. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 67
  68. 68. 3 The Base Station Subsystem Exercise (1/2) – True or False? – – For each cell, the number of channels which can be used for GPRS traffic is operator-configurable – If a user packet is lost at the Gb interface, it can be recovered using frame relay protocol mechanisms – Time allowed : The SGSN is linked to the BSS by an interface based on the Frame Relay protocol The LLC protocol is independent of the type of BSS employed 5 minutes Introduction to GPRS/EGPRS 68 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 68
  69. 69. 3 The Base Station Subsystem Exercise (2/2) – True or False? – In a cell, a TRX can carry eight PDCHs – One PDCH can be allocated in its entirety to a single user – If necessary, blocks on different PDCHs can be allocated to a single user – The NSEI is the identifier used by the SGSN to indicate the destination cell of a LLC frame to the MFS – Time allowed :The same quantity of PVCs is declared on the MFS and SGSN 5 minutes sides Introduction to GPRS/EGPRS 69 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 69
  70. 70. 3 The Base Station Subsystem Evaluation > Objective : To be able to briefly describe the data interchange mechanisms through the BSS Thank you for answering the self-assessment of the objectives sheet Introduction to GPRS/EGPRS 70 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 70
  71. 71. 4 Alcatel Solution All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 71
  72. 72. 4 Alcatel Solution Session presentation > Objectives: to be able to characterize the solution offered by Alcatel > Program: • 4.1 GPRS Network Overview • 4.2 Alcatel 9135 MFS • 4.3 Packet Switched Core Network • 4.4 GPRS Network Management • 4.5 Alcatel QoS Offer Introduction to GPRS/EGPRS 72 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 72
  73. 73. 4 Alcatel Solution 4.1 GPRS Network Overview Radio subsystem B T S GSM/GPRS common servers BSS1 MSC HLR CAMEL & IP based Prepaid SCP Services SMS-C BSC B T S GPRS Core Network A9135 MFS BSS2 B T S SGSN Intranet BSC GPRS IP backbone Frame Relay network B T S Firewall iGGSN access router Internet BSS-- B T S SGSN BSC Charging Gateway A9135 MFS B T S Border Gateway Inter-PLMN backbone OMC-CN 73 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w Within the radio subsystem : Existing Alcatel BTS and BSC from GSM are reused for GPRS : no need of hardware change to provide GPRS features need just software upgrade The GSM-BSS now includes a proprietary equipment : Alcatel A9135 = MFS (Multi BSS Fast packet Server) which deals with the GPRS PCU functions w Within the GPRS Core Network : both SGSN and iGGSN are Alcatel proprietary equipments Charging Gateway and OMC-CN are Alcatel components based on HP platform Firewalls, Border gateway and access routers are standard IT components w The HLR, MSC, SCP and SMS-C are reused from the GSM-NSS © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 73
  74. 74. 4 Alcatel Solution 4.2 Alcatel 9135 MFS > Functional architecture Control Subsystem OMC-R M F S LAN x 2 A-ter if B T S Gb if BSC1 GPU1 PCU B T S S GPU2 PCU G Telecom Subsystem B T S S GPU1 BSC2 PCU B T S GPU1 N PCU 74 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w The duplex "Control subsystem" (two DS10 in active/standby mode, with 2 shared disks) : controls the “telecom subsystem” (initialization, supervision, defence) provides the management interface (OMC-R or local maintenance terminal) w The “Telecom subsystem” is composed of GPU boards : 1. GPRS Processing Unit (GPU). 2. Each GPU board performs the PCU functions towards the BSC and the SGSN 16 PCM ports per GPU board some PCM ports connected to the BSS, the other to the SGSN w There are two different configurations regarding the support of BSC by the GPU boards : only one GPU board supporting each BSC (in the B6.2 release) multiple GPU boards supporting each BSC (from the B7 release) © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 74
  75. 75. 4 Alcatel Solution 4.2 Alcatel 9135 MFS CONNECTIONS 120 CICs TC SM BSC MSC BSC BSC 120 GICs 16K A Interf PVC PCU BSC PCU FRAME PCU SGSN RELAY PCU PMSC PVLR BSC PCU MFS Muxed ATer Introduction to GPRS/EGPRS 75 Gb BEARER CHANNEL All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 75
  76. 76. 4 Alcatel Solution 4.2 Alcatel 9135 MFS > Rack layout 1 BSXTU 1 BSXTU 11 GPU (+1) 11 GPU (+1) maxi maxi 1 BSXTU 1 BSXTU 11 GPU (+1) 11 GPU (+1) maxi maxi 2 DS 10 2 DS 10 Control Control sub-rack sub-rack 2 or 4 2 or 4 Switches Switches 3 COM 3300 3 COM 3300 + IOLAN module + IOLAN module Introduction to GPRS/EGPRS 76 All rights reserved © 2004, Alcatel w The "Control sub-rack" part is duplex (two DS10 in active/standby modes). w each BSXTU sub-rack contains a maximum of 12 JBGPU boards. The GPRS traffic of one BSC can be handled by several GPUs (up to six are foreseen from the same MFS rack) Since B7, a full MFS contains from 4 to 22 BSS (BSC), due to multi-GPU feature 4 BSS per MFS: 2* (1 BSS / 6 GPU)+(1 BSS / 5 GPU) 22 BSS per MFS: 22*(1 BSS/GPU) w One JBGPU board (= 1 PCU) offers 480 PDCH. Two uses of JBGPUs : 1. One JBGPU for each BSC, (Ater interface), so one MFS serves a maximum of 22 BSCs. 2. With 240 PDCH per GPU, a BSC can offer up to 6*240 = 1440 PDCH 3. To be connected to the FR network (Gb interface). w Fast ethernet Switches (100 Mb/s) made by 3COM: 2 or 4 (as needed) to build LANs to which are connected the Nectar stations (DS10) GPU boards printers and craft terminals (for local management, the terminal is called IMT = Installation & Maintenance Terminal) © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 76
  77. 77. 4 Alcatel Solution 4.2 Alcatel 9130 MFS (1/3) ATCA shelf ATCA shelf Introduction to GPRS/EGPRS 77 All rights reserved © 2004, Alcatel w This platform is a high availability distributed platform composed of blades compliant with the Advanced Telecom Computing Architecture (ATCA) open standard w ATCA has been developed by the PCI Industrial Computers Manufacturers Group (PICMG). w The related specifications are described in the PICMG 3.0 R1.0. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 77
  78. 78. 4 Alcatel Solution 4.2 Alcatel 9130 MFS (2/3) General Option 1 Option 2 ATCA shelf content MFS ATCA shelf G P MFS MFS LIU G P G P G P O S S O M S S M C ATCA shelf G P W W G P G P G P G P G P C LIU Introduction to GPRS/EGPRS P P 78 All rights reserved © 2004, Alcatel w LIU: Line Interface Unit – to collect the external PCM connections w GP: GPRS Processing module w OMCP: O&M Control Processing board – the control stations, w SSW: Subrack SWitch © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 78
  79. 79. 4 Alcatel Solution 4.2 Alcatel 9130 MFS (3/3) E1 connections Abis L I U 16 LIU X 16 E1 Ater M M U UX X L I U S S S S W W GP GP GP GP GP GP GP GP GP GP MFS 9 PCU + 1SPARE OMCP OMCP 79 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w LIU shelf: Multiplexes/demultiplexes and cross connects all E1 external links to/from NE multiplexed links (n E1 over Ethernet) on the TP and the GP board. Equipped with two Mux boards and n LIU boards, depending on capacity. w The LIU shelf hosts Two MUX boards which collect the E1 links from the 16 LIU boards on 16 serial links at 36.864 Mbit/s and build packets sent towards up to 32 directions (125ms each) on a Gigabit Ethernet link. w SSW: it’s an Ethernet switch which allows exchanges between all platform elements and externalIP/Ethernet equipment. w OMCP: these control stations are used to process defense functions and platform Operation, Administration and Maintenance (OAM) generic services.. w GP: Manages the user plane packet data flow processing. w Ethernet links on the IP ports of the SSW switch: these links connect the platform to external IP equipment (i.e. OMC-R, external alarm box). © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 79
  80. 80. 4 Alcatel Solution 4.3 Packet Switched Core Network towards Prepaid Servers > SGSN > iGGSN Pilot Blades O&M, Charging GPRS signaling & user Plane Blades O&M & service provisioning Intra-PLMN DNS SS7 Blades Vigilon Gr, Gs, Senteon session control logic Gd, Ge PDN1 GPRS IP Backbone WN Gb WN GPU PDN2 Ethernet LAN (internal com.) Switching & Routing OMC-CN Charging Gateway GTP control & user planes 80 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w The SGSN is ATCA based component (Advanced Telecom Computing Architecture). The main functions are distributed over different hardware modules : SS7 network interfaces (Gs, Gr, Gd) by a number of ATCA SS7 blades, Gb interface by a number of Alcatel proprietary GPU boards, SGSN O&M and GPRS charging agent (initialisation, defense, O&M, and CDR) by a cluster of ATCA Pilot blades, GPRS signaling and user traffic handling by a number of ATCA control & user plane blades SGSN internal communication, switching and routing of user traffic by a dedicated Ethernet switch w The iGGSN is an Alcatel proprietary equipment, where the main functions are distributed over 3 hardware modules : Vigilon server for iGGSN O&M, subscriber configuration and service provisioning, Senteon server as a control logic for subscription and credit check during session establishment phase, WN1200 node for full 3GPP GTP services © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 80
  81. 81. 4 Alcatel Solution 4.3 Packet Switched Core Network SGSN rack backbone rack iGGSN rack NTS150 NTS150 GPU boards NTP Servers Gn switches NS500 Ethernet switch/routers WN1200 NS500 Firewalls border router ATCA platform pilot blades access router Senteon 1&2 GPRS control & user plane blades external DNS Ethernet switch/routers SS7 blades Internal control LAN Introduction to GPRS/EGPRS Intra-PLMN DNS/DHCP 81 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 81
  82. 82. 4 Alcatel Solution 4.4 GPRS Network Management > Dedicated OMCs BSC1 B T S B T S Radio part BSC2 B T S OMCR MFS NMC Q3 SGSN Core Network part OMCCN DNS/DHCP NTP BG iGGSN Charging Gateway 82 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w OMC-R: Called Alcatel 1353 RA = management of the radio subsystem : Alcatel 9135 MFS. BSCs and associated BTSs w OMC-CN : called ALMA 1364 GPRS = management of the Core Network : the SGSN server the SGSN router the GGSN. The Charging Gateway (alarm supervision) the DNS/DHCP server (supervision) the GPRS network level (APN and Routing Areas) © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 82
  83. 83. 4 Alcatel Solution 4.5 Alcatel QoS offer > R97/98 QoS compliance ETSI R’97/98 QoS attributes Delay class Mean throughput class Precedence class Alcatel Offer Resulting QoS class (4) Best Effort any any Best-Effort 1, 2 or 3 (3) Low priority any Best-Effort 1, 2 or 3 Normal, High priority Best Effort Best-Effort 1, 2 or 3 (2) Normal priority specified, except BE Normal 1, 2 or 3 (1) High priority specified, except BE Premium as required by the MS Reliability class: 83 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w These QoS attributes are associated with a PDP context performed by a R97/98 MS w The five QoS parameters of the standard define more than 60 combinations ! Which is too much and leeds to simplification : Too complex to implement, Many of the combinations have no meaning! The standard "allows" more simple QoS implementations. “-” = any value. In bold, the main criterion for definition of the resulting QoS. w Best effort = inexpensive, comparable to the Internet (no commitment). Ideal for foraging on the internet. w Normal: Comparable to an intranet. w Premium: Expensive, high performance. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 83
  84. 84. 4 Alcatel Solution 4.5 Alcatel QoS offer > R97/98 QoS mapping into R99 QoS R99 Traffic class Traffic handling priority conversational R97/98 Bearer QoS class - Premium streaming - Premium interactive 1 Premium interactive 2 Normal interactive 3 Normal background - Best Effort Introduction to GPRS/EGPRS 84 All rights reserved © 2004, Alcatel w The mapping of R97/98 QoS attributes to R99 QoS is applicable in the following cases : hand-over of PDP context from GPRS R97/R98 SGSN to GPRS R99 or UMTS SGSN when a R99 MS performs a PDP context activation in a R99 SGSN with a R97/98 GGSN when the SGSN has received R97/98 QoS subscribed profile, but the MS is R99 w The mapping of R99 QoS attributes to R97/98 QoS is applicable in the following cases : PDP context is handed-over from GPRS R99 to R97/R98 when a R99 MS performs a PDP context activation in a R99 SGSN while the GGSN is R97/98 when the SGSN sends user data to the BSS for a R99 MS when the SGSN has received R99 QoS subscribed profile but the MS is R97/98 in the new SGSN, during an inter-SGSN RA_update procedure, or inter-system change, on receipt of the R99 QoS attributes from the old SGSN © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 84
  85. 85. 4 Alcatel Solution Exercise (1/2) – True or False? – – The iGGSN is an Alcatel proprietary equipment – The SGSN server is an Alcatel proprietary equipment based on IT devices – Time allowed : Implementing GPRS in the BSS simply entails adding A9135 or A9130 MFS servers The DNS/DHCP servers used in the GPRS Core Network are IT standard servers 5 minutes Introduction to GPRS/EGPRS 85 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 85
  86. 86. 4 Alcatel Solution Exercise (2/2) – True or False? – GPRS Core Network equipments are managed from an OMC- CN – GPRS radio subsystem (BSS) equipments are managed from an OMC-R – Alcatel GPRS network handles simultaneously the UMTS QoS classes (R99 QoS parameters) and the GPRS QoS profiles (R97/98 QoS attributes) Time allowed : 5 minutes Introduction to GPRS/EGPRS 86 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 86
  87. 87. 4 Alcatel Solution Evaluation > Objective : to be able to characterize the solution offered by Alcatel Thank you for answering the self-assessment of the objectives sheet Introduction to GPRS/EGPRS 87 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 87
  88. 88. 5 Annex and Glossary All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 88
  89. 89. 5 Annex 1 Coding Schemes : CS1 -> CS4 Channel rate (kbps) 20 CS4 CS3 15 CS2 10 CS1 5 0 0 10 20 30 C/I (dBm) BACK 89 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w The data rate on a PDCH depends on the coding scheme : for CS-1: PDCH data rate = 9.05 kbit/s (poor radio conditions or BSS signaling) for CS-2: PDCH data rate = 13.4 kbit/s (better radio conditions) for CS-3: PDCH data rate = 15.6 kbit/s for CS-4: PDCH data rate = 21.4 kbit/s. w The system selects automatically the best coding scheme : the data rate is set according to the current C/l. maximum data rate (160 kbit/s) only possible with CS4 on 8 parallel channels © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 89
  90. 90. 5 Annex 2 GPRS compared to other technologies 2 Mbps Bit rate 384 Kbps 160 Kbps 64 Kbps 9.6 Kbps Technology CS data - SMS, 9.6Kbps HSCSD GPRS EDGE UMTS Introduction to GPRS/EGPRS 90 All rights reserved © 2004, Alcatel w SMS : With GPRS, the 160-character barrier for short messages will be able to be broken (when SMS over GPRS is implemented). w High Speed Circuit-Switched Data : This still involves circuit switching, meaning that, with a continuous use of radio resources, so billed by time. HSCSD is based on the assignment of several traffic channels (TCH) to a single MS to offer a higher bit rate. HSCSD is suited for services requiring a minimum bandwidth guaranteed. w EDGE : (Enhanced data rates for GSM evolution) is a technology previously developed by Ericsson, based on TDMA and offering a maximum theoretical speed of 384 kbit/s (8 channels, each 48 kbit/s, using a new modulation scheme: 8-PSK, eight-phase shift keying, instead of GMSK for GSM and GPRS). w EDGE-specific MTs are required! The BSS remains the same, except for the implementation of EDGE TRX (Evolium product line). Alcatel will offer EDGE from release B8 onwards. This is an important step towards UMTS w UMTS : requires a new Radio Access Network based on W-CDMA technology. The UMTS standard is part of the Third Generation (3G). Together with CDMA 2000 and other systems, they form a set of ITU radio access technologies standardized by IMT 2000. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 90
  91. 91. 5 Annex 3 PCU concept PCU JBGPU FUNCTION TBF = Temporary Block Flow TFI 9 TBF 9 1 9 TFI = Temporary Flow Identifier BSN = Block Sequence Number TBF from SERVER 9 2 9 TBF 4 9 4 9 5 9 6 21 22 TBF 7 TBF from SERVER 4 2 4 23 4 24 4 25 4 26 4 27 4 TFI 2 2 90 89 2 91 90 28 4 29 4 30 4 31 TBF from SERVER 2 2 92 2 93 2 94 2 95 TS x dedicated to ONE PDCH 2 9 TFI 4 4 3 4 21 4 22 9 1 Introduction to GPRS/EGPRS 2 2 96 2 97 2 98 2 99 2 10 one PDCH shared by N users 91 2 92 9 2 4 23 2 93 2 94 91 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 91 4 2
  92. 92. 5 Annex 4 PCU concept LLC Checks the transmission between SGSN and MS RLC checks the trans between PCU and MS PDCH PCU TRE /BTS CCU Gb n RLC blocks RLC blocks - token - Data - radio security Introduction to GPRS/EGPRS LLC blocks 92 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 92
  93. 93. 5 Annex 5 TDMA and PDCH > TDMA frame and GPRS physical channels 8Psk 171 0 1 2 3 4 5 6 7 FRAME 0 4 4 0 57 171 1 2 3 4 5 6 7 FRAME 1 4 4 4 4 4 4 4 4 4 Gmsk 57 0 1 2 3 4 5 6 7 4 4 4 4 4 4 4 1 2 3 4 5 6 7 FRAME 3 FRAME 2 4 0 4 4 4 4 4 4 4 4 F00 F01 F02 F03 F04 F05 F06 F07 F08 F09 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24 F25 4 F50 F51 PTCCH B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 1 PDCH 12 BLOCS Frame 12 52 FRAMES then 52 TS x and 240 ms Frame 38 BLOC 3 Introduction to GPRS/EGPRS 93 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 93
  94. 94. 5 Annex 6 GPRS channels > Master and Slave PDCHs MASTER PDCH PDCH DOWN/UPLINK B1 B2 B3 All blocs can be used as - PDTCH - PACCH B1 B4 B5 B6 B7 B8 B2 B9 B10 B11 Blocs which can be used as - PAGCH - PDTCH - PACCH Blocs which can be used as - PPCH - PAGCH - PDTCH - PACCH /UPLINK B0 B0 B1 B1 B2 B3 B3 B4 B4 B5 B5 B6 B6 B7 B0 Blocs which can be used as - PBCCH DOWN B2 B0 B7 B8 B8 B9 B9 B10 B10 B11 B11 All blocs can be used as - PRACH - PDTCH - PACCH 94 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w For each cell, it is possible to define the MINIMUM and MAXIMUM number of channels reserved for GPRS + the maximum number of channels reserved for GPRS in case of high traffic load (when the BSC sends "Load indication" to the MFS through BSCGP protocol). w There are two types of PDCH : MPDCH and SPDCH MPDCH = Master PDCH = PBCCH + PCCCH (PPCH + PAGCH + PRACH) -> carries GPRS signaling and system information. SPDCH = Slave PDCH -> carries the user traffic. w Benefits of the Master Channel : Preserves CCCH capacity for speech services Higher GPRS signaling capacity, in line with GPRS traffic growth Differentiated cell re-selection strategy between GPRS and non GPRS MS. When GPRS attached, a MS listen to PSI broadcast on PBCCH. It allows a finer tuning of GPRS re-selection algorithms, for example in hierarchical networks (C31 and C32 criteria). Otherwise, MS applies the basic Cell-reselection as in GSM Idle-Mode using the C1 and C2 GSM criteria © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 94
  95. 95. 5 Annex 7 PDCH ,TBF, MAC concepts TFI 1 TFI 5 TFI 3 TFI 6 TBF from server 1 TBF from server 2 TBF from server 3 TBF from server 4 B1 DOWN u3 B2 u3 UP TFI 2 USER 3 TFI 7 USER 6 TFI 6 USER 2 B3 u3 B2 B4 u3 B3 B5 u3 B4 B6 B7 u3 B5 u3 B6 B8 u3 B7 B9 u6 B8 B10 u6 B9 B11 u2 B10 B12 u2 B11 B1 un B12 B1 TBF server 5 TBF to server 6 TBF to server 7 Introduction to GPRS/EGPRS 95 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 95
  96. 96. 5 Annex 8 Different uses for E1 > PCM E1 and Bearer Channel uses and concepts BEARER CHANNEL=960K TS 1 2 TS 2 64K M B TS 3 64K TS 4 64K TS 5 TS 1 16K X 4 2 TS 2 32K X 2 2 M B TS 3 64K X 1 M B 64K 64K 64K TS 4 128K 64K X 2 TS 1 TS 2 TS 3 TS 4 TS 15 TS 5 E TS 28 64K E 1 TS 29 64K TS 3 1 TS 31 64K E TS 28 TS 29 192K TS 3 64K X 3 TS 17 TS 18 TS 19 TS 20 1 TS 31 TS 31 BEARER CHANNEL =960K Introduction to GPRS/EGPRS 96 All rights reserved © 2004, Alcatel w Minimum size for a bearer channel: 1 x 64k, Maximum size for a bearer channel: 31 x 64k. w One PVC per bearer channel. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 96
  97. 97. 5 Annex 9 FRAME RELAY and PVC concepts DLCI Number 9 PVC y FRAME RELAY SGSN Node 27 PCU 6 MFS 16 15 5 PVCn 12 Introduction to GPRS/EGPRS 97 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 97
  98. 98. 5 Annex 10 PVC and NSVC concepts NSVC Transmission check end to end FRAME PCU MFS SGSN RELAY PCM E1 BEARER CHANNEL Permanent Virtual Connection Introduction to GPRS/EGPRS 98 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 98
  99. 99. 5 Annex 11PCM 1 TDMA and PDCH BC 1 BC 2 P C PCM 1 U PVC / NSVC PVC / NSVC There is One PVC/NSVC per Bearer Channel BC 3 BC1 PVC / NSVC NSE NSEIx PCM 2 There is one NSE for all the PVC of one PCU Introduction to GPRS/EGPRS 99 All rights reserved © 2004, Alcatel © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 99
  100. 100. 5 Annex 12 Network Mode of Operation I with Master Channel CCCH MSC VLR A PCCCH Gs BSC (a) PACCH SGSN (b) Um Gb CS paging for GPRS-attached MS in idle state (a), or in data transfer state (b) CS paging for non GPRS-attached MS Introduction to GPRS/EGPRS GPRS paging 100 All rights reserved © 2004, Alcatel w In this mode, the Gs interface is present in the core network. As far as GPRS-attached MS are concerned, the BSS receives both GPRS and circuit-switched paging messages from the Gb interface. w There is paging co-ordination because all paging messages towards GPRS-attached mobile stations are sent either on the Master Channel, if present, or on the CCCH otherwise. w In addition, whilst involved in a packet data transfer the GPRS mobiles receive the circuit-switched paging messages via the GPRS traffic channel currently used. w NMO II : There is neither Gs interface nor Master Channel. There Paging coordination over the CCCH of GSM. Also, GPRS Mobile Stations operating in Class B may lose CS Paging message if they are not able to monitor CCCH at the same time. w NMO III: In this mode, there is no Paging coordination because Gs interface is not present while the Master Channel is. Therefore, CS Paging is transmitted over CCCH when PS Paging is transmitted over PCCCH. Class C Mobile are not able to manage both type of channels. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 100
  101. 101. 5 Annex 13 MOBILE ONE PHASE ACCESS ON PCCH (Master PDCH) NETWORK Packet channel request PRACH Packet UL assignment + polling indication PAGCH TFI PDCH USF TA Packet Control ACK PACCH Usf Scheduling RLC data bloc PDTCH Packet UL ACK NACK PACCH 101 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w "Attach" the MS switches on (GMM protocol): MS sends his previous P_TMSI, otherwise a random one. The attach_request message is placed in an LLC frame with its old TLLI if its exists, or a randomly chosen TLLI if not. w TLLI: This is allocated to the subscriber on his attachment to the network. In reality, the SGSN allocates the MS a P-TMSI, from which the MS and the SGSN itself derive the TLLI. w The functions of the HLR: to supply the security triplets to check roaming restrictions (or ODB) to store the address of the current SGSN to initiate the deletion of data from the old SGSN to send subscriber data to the SGSN w "Detach" proceeds as follow: MS to SGSN: Detach request SGSN to GGSN: Delete PDP context then Acknowledge SGSN to MS: detach accept © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 101
  102. 102. 5 Annex 14 MOBILE ONE PHASE ACCESS ON CCCH (no master PDCH) NETWORK Channel request RACH Immediate assignment AGCH TFI PDCH USF TA Packet uplink assignment + polling indication PACCH Packet control ACK PACCH TFI PDCH USF Usf Scheduling RLC data bloc PDTCH Packet UL ACK NACK PACCH 102 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w "Attach" the MS switches on (GMM protocol): MS sends his previous P_TMSI, otherwise a random one. The attach_request message is placed in an LLC frame with its old TLLI if its exists, or a randomly chosen TLLI if not. w TLLI: This is allocated to the subscriber on his attachment to the network. In reality, the SGSN allocates the MS a P-TMSI, from which the MS and the SGSN itself derive the TLLI. w The functions of the HLR: to supply the security triplets to check roaming restrictions (or ODB) to store the address of the current SGSN to initiate the deletion of data from the old SGSN to send subscriber data to the SGSN w "Detach" proceeds as follow: MS to SGSN: Detach request SGSN to GGSN: Delete PDP context then Acknowledge SGSN to MS: detach accept © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 102
  103. 103. 5 Annex 15 MOBILE ORIGINATING DATA TRANSFERT SGSN BSS UL TBF Establishment Paquet channel request Paquet UL assignement STAND BY RLC PDU RLC PDU RLC PDU PACKET UPLINK ACK/NACK UL UNIDATA RLC PDU READY RLC PDU RLC PDU PACKET DOWNLINK ASSIGNEMENT UL UNIDATA UL TBF Release 103 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w "Attach" the MS switches on (GMM protocol): MS sends his previous P_TMSI, otherwise a random one. The attach_request message is placed in an LLC frame with its old TLLI if its exists, or a randomly chosen TLLI if not. w TLLI: This is allocated to the subscriber on his attachment to the network. In reality, the SGSN allocates the MS a P-TMSI, from which the MS and the SGSN itself derive the TLLI. w The functions of the HLR: to supply the security triplets to check roaming restrictions (or ODB) to store the address of the current SGSN to initiate the deletion of data from the old SGSN to send subscriber data to the SGSN w "Detach" proceeds as follow: MS to SGSN: Detach request SGSN to GGSN: Delete PDP context then Acknowledge SGSN to MS: detach accept © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 103
  104. 104. 5 Annex 16 MOBILE TERMINATING DATA TRANSFERT SGSN BSS STAND BY PAGING PS Packet Paging Request channel request UL TBF Paquet UL assignement LLC PDU UL UNIDATA READY DL UNIDATA DL TBF PACKET DOWNLINK ASSIGNEMENT 104 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w "Attach" the MS switches on (GMM protocol): MS sends his previous P_TMSI, otherwise a random one. The attach_request message is placed in an LLC frame with its old TLLI if its exists, or a randomly chosen TLLI if not. w TLLI: This is allocated to the subscriber on his attachment to the network. In reality, the SGSN allocates the MS a P-TMSI, from which the MS and the SGSN itself derive the TLLI. w The functions of the HLR: to supply the security triplets to check roaming restrictions (or ODB) to store the address of the current SGSN to initiate the deletion of data from the old SGSN to send subscriber data to the SGSN w "Detach" proceeds as follow: MS to SGSN: Detach request SGSN to GGSN: Delete PDP context then Acknowledge SGSN to MS: detach accept © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 104
  105. 105. 5 Annex 17 GMM - Combined GPRS and NSS attach with Gs (1) SGSN Attach_request (IMSI) HLR Triplet request ( rand kc sres ) Authentication Update_location IMSI ↔ current SGSN Insert_subscriber_data Update_location_ack IMSI ↔ TLLI + current RA + subscription data Attach_accept (TLLI) MS ↔ TLLI TLLI Established 105 Introduction to GPRS/EGPRS All rights reserved © 2004, Alcatel w "Attach" the MS switches on (GMM protocol): MS sends his previous P_TMSI, otherwise a random one. The attach_request message is placed in an LLC frame with its old TLLI if its exists, or a randomly chosen TLLI if not. w TLLI: This is allocated to the subscriber on his attachment to the network. In reality, the SGSN allocates the MS a P-TMSI, from which the MS and the SGSN itself derive the TLLI. w The functions of the HLR: to supply the security triplets to check roaming restrictions (or ODB) to store the address of the current SGSN to initiate the deletion of data from the old SGSN to send subscriber data to the SGSN w "Detach" proceeds as follow: MS to SGSN: Detach request SGSN to GGSN: Delete PDP context then Acknowledge SGSN to MS: detach accept © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 105
  106. 106. 5 Annex 18 GMM - Combined GPRS and NSS attach with Gs (2) MSC/VLR SGSN HLR Location_Update_req (IMSI, LAI) Update_ location (IMSI, @VLR) IMSI ↔ current VLR Insert_subscriber_data Update_location_ack Location_Update_accept Introduction to GPRS/EGPRS 106 All rights reserved © 2004, Alcatel w Location-Update-request: The SGSN determines the MSC/VLR based on the RA where the subscriber is located. w At the HLR: If the MS was declared in another MSC, the HLR sends it a Cancel_Location before doing ISD to the new MSC. w Attach-accept: In practice, the SGSN sends the MS the P-TMSI (and not the TLLI) and the V-TMSI (TMSI of the VLR), designated TMSI here. w Once this combined-attach is done, the MS can make combined LA/RA update procedures (see GSM 03.60).. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 106
  107. 107. 5 Annex 19 GMM - RA update Inter-SGSN (1) new SGSN old SGSN GGSN Routing_Area_update_req (RA1) SGSN_context_req (RA1, TLLI, @SGSN2) SGSN_context_resp (MM_ctxt, PDP_ctxt) SGSN_context_ack transfer of stored packets Update_PDP_context_req (TID, @SGSN2) Update_PDP _context_resp Introduction to GPRS/EGPRS 107 All rights reserved © 2004, Alcatel w RA1: This is the mobile's previous RA The New SGSN retrieves the IP address of the old SGSN from RA1, after request to the DNS which translate RA1 into IP @ of SGSN1. w SGSN_context_req:To obtain any PDP contexts and the MM contexts (IMSI, RA, cell, IMEI, etc) = all the data stored in the old SGSN concerning the MS, including the address of the GGSN related to each PDP context activated. w SGSN_ctxt _ack: This message is sent only if the subscriber has PDP contexts activated. Used to inform the old SGSN that receives and stores datagrams for the MS. w Update_PDP_context_req: Mainly to inform the GGSN of the address of the new current SGSN for this MS. Thus, any new packet arriving from the PDP network is routed to the new SGSN. This operation is carried out in parallel with the retrieval of the old SGSN packets, and not afterwards as the figure above seems to indicate. © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 107
  108. 108. 5 Annex 20 GMM - RA update Inter-SGSN (2) new SGSN old SGSN HLR Update_location (IMSI, @SGSN2) cancel_location (IMSI) cancel_location_ack insert_subscriber_data (+ack) Update_location_ack Routing_Area_update_accept (TLLI) Routing_Area_update_complete Introduction to GPRS/EGPRS 108 All rights reserved © 2004, Alcatel w ISD: = ISD (IMSI, GPRS subscription data). w The tunnel (SGSN-GGSN) moves with the subscriber: The GGSN is always the same and the SGSN is variable (same TID). w RA update accept: The SGSN allocates the subscriber a P-TMSI or TLLI, as mentioned (derived from the P-TMSI). © Alcatel University – 3FL10472ACAAWBZZA Ed.02 Page 108

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