Wcdma radio functionality


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Wcdma radio functionality

  1. 1. UMTS Radio Features Presentation Praveen Gupta, MobileStack, pgupta@mobilestack.com UMTS Presentation - 1
  2. 2. Admission control overview Guarantees the overall Quality of Service by controlling the number of users Interference Coverage Planned coverageAdmission New users blocked threshold above this point User added Capacity / Load Planned load UMTS Presentation - 2
  3. 3. Admission control purpose & algorithmdescriptionPurpose:– This algorithm selectively denies access requests in order to limit the load.Algorithm description:– When new resources are required for a radio connection (Radio Link set-up or modification), the Radio Connection Coordination algorithm requests admission. This requests includes parameters specifying the requested amount of resources. Admission Control checks if the requested amount of resources is available. UMTS Presentation - 3
  4. 4. Characteristics of admission control The RBS regularly reports measurements values of transmitted power By knowing the connections, the RNC keeps track of ASE, RBS HW and DL code usage Handover legs have higher priority than new calls Different thresholds for different services At high load, interactive users may be offered lower datarates than under normal load conditions UMTS Presentation - 4
  5. 5. Congestion control overview Bitrate Over load is resolved by: Delaying packets Call removal UMTS Presentation - 5
  6. 6. Congestion control purpose & algorithmdescriptionPurpose: This algorithm solves overload situations. Anoverload situation occurs due to fluctuations in the ULinterference and the used DL power.Algorithm description : The algorithm is only triggered incase of (near) overload in a cell. The algorithm acts in casethe transmitted Carrier Power measurement (DL Power)indicates overload. It is possible to set different thresholdsfor different services. UMTS Presentation - 6
  7. 7. Example 1: Congestion control work flow DL power or UL interference exceeded Restrict access Order admission to block No At overload, alter Yes Interactive users in connection with system? highest DL power Move user to common ch Remove user Set timer Message: over- Allow admission Timer expired load resolved Wait for command and access UMTS Presentation - 7
  8. 8. Enhanced Capacity control Admission control checks HW resources in both UL & DL Directed retry at call set-up to GSM in case of admission denial in WCDMA Load balancing between different frequencies UMTS Presentation - 8
  9. 9. Power control overview P(SIR-Target,UL) Closed loop DL-TPC UL-TPC UL-Outer loop RNC SIR-Target,UL P(SIR-Target, DL) SIR-Error,ULDL-Outer loop BLER-Measured,DL Open loop SIR-Target,DL P(Startvalue) BLER = Block Error Rate SIR = Signal to Interference Ratio TPC = Transmit Power Control UMTS Presentation - 9
  10. 10. Power control purpose & reason Purpose: The purpose is to minimize the transmit power while maintaining the quality of radio links. There are three different types power control: – Inner loop power control – Outer loop power control – Open loop power control. Reason: Power control – Maintains the quality of the connections – Reduces power consumption – Minimizes interference – Improves the coverage and capacity of the system UMTS Presentation - 10
  11. 11. Power control over time RBS Inner-loop power Control Inner-loop power Control Receive Power (Initial Receive Power (Updated Receive Power Target Target) by Outer-loop power Control) Open-loop Power Control Access Preambles time Access Preambles RACH DPCH 1500 updates/sec RBS Receive Power Target The PRACH is “power controlled” by means of preamble ramping UMTS Presentation - 11
  12. 12. Channel type switching overview User 1 User 2 Random-Access Random-Access Request Request Random-Access ChannelSwitch to Switch todedicated TTime-out common Packet Packet Packet Dedicated Channel Release dedicated channel UMTS Presentation - 12
  13. 13. Channel type switching purpose & reasonPurpose:To optimize the channel usage for best effort packet switchedusers (Interactive users). To determine if it is necessary toswitch UE connected substates e.g. from a common to adedicated channel.Reason:For best effort traffic for a particular user there is largevariations in time in the offered traffic (bursty nature of traffic).It is not efficient for the air-interface to keep up resources for adedicated channel continuously. This function saves alsobattery for connected UEs, which are not transferring data. UMTS Presentation - 13
  14. 14. Channel rate switching Change bit rate when moving awayfrom RBS:- UL supported by UE- DL supported in RNC Bit rateAdvantage: Higher coverage and highercapacity Change of bit rate at high load Distance- Reduce bitrate for Interactive users from RBS- Reduce bitrate for voice users by orchanging AMR mode Load in the cellAdvantage: Lower blocking probability UMTS Presentation - 14
  15. 15. Adaptive Multi Rate (AMR) Rate SelectionSelection of the AMR modeat call set up Bit rate for a user [kbps]About four combinations ofsimultaneous modes 12.2 X 7.95 Xdefined by the standard is 4.75 XsupportedThe modes range from Distancearound 4.75 kbps up to 12.2 from RBS orkbps Load in the cell UMTS Presentation - 15
  16. 16. Adaptive Multi Rate (AMR) Rate ControlPossible to change the AMRmode for coverage and Bit rate for a usercapacity reasons dynamically. [kbps]The AMR switching and rate 12.2 7.95control optimises the usage of 4.75the air-interface by adaptingthe AMR rates for coverage Distanceand capacity reasons. from RBS or Load in the cell UMTS Presentation - 16
  17. 17. Transmit Diversity - Open loop - Introduced to combat fading with up to 5dB gain in the downlink On 10 dBOn Off 15 dB UMTS Presentation - 17
  18. 18. Open Loop Transmit Diversity Coverage & capacity gain – additional diversity effect -> less transmitted power -> less interference in the system The same information is transmitted from the two antennas. For each antenna the information is coded in a different way. The total transmitted power is split between the two antennas. UMTS Presentation - 18
  19. 19. Open Loop Transmit Diversity- Space-Time Transmit Diversity (STTD) A b0 b1 b 2 b3 Antenna A B b0 b1 b2 b3 -b2 b3 b0 -b1 Antenna B Channel bits STTD encoded channel bits for antenna A and antenna B. The signals from the two antennas are spread and scrambled with the same code and simultaneously transmitted The two signals experience different fading patterns and the RAKE receiver observes the sum of the two faded orthogonal signals The resulting signal has a smoother fading pattern than the two original signals Used on all DL channels (except SCH and CPICH). UMTS Presentation - 19
  20. 20. Open Loop Transmit Diversity- Time Switched Transmit Diversity (TSTD) b0 b2 Antenna A b0 b1 b2 b3 b1 b3 Antenna B Channel bits In TSTD the transmission alternates between the antennas Used on Synchronization Channel (SCH) TSTD is implemented as a part of STTD UMTS Presentation - 20
  21. 21. Transmit diversity - Closed-loop Closed-loop Transmit Diversity (DPCH, PDSCH only) – UE sends Feedback Information (FBI) Bits to the RBS over the DPCCH – FBI bits tell the RBS how to adjust antenna gain (only mode 2) and phase (both mode 1 and mode 2) for optimal reception at the UE – Mode 1 supported in P4 CPICH1 Antenna 1 DCH (or PDSCH) Σ Antenna 2DPCCH • S/P Demux • Channelization MUX • ScramblingDPDCH • I/Q Modulation Σ CPICH2 Calculate Decode FBI Gains, Phases UMTS Presentation - 21
  22. 22. TX diversity modes mapped on physical channels Application of Tx diversity modes on downlink physical channel types "X" – can be applied, "–" – not applied Physical channel type Open loop mode Closed loop TSTD STTD Mode P-CCPCH – X – SCH X – – S-CCPCH – X – DPCH – X X PICH – X – PDSCH – X X AICH – X – CSICH – X – UMTS Presentation - 22
  23. 23. Blossoming and wiltingThe purpose of the blossoming (at cell addition) and wilting (at cell removal) isto allow cells to be added or removed from the radio network with minimumdisturbance to the network. RBS1 RBS2 Wilting Blossoming Output power gradually decreased (wilting) Output power gradually increased (blossoming) UMTS Presentation - 23
  24. 24. Micro cell support overview Support of micro cells to: – cover white spots or to – increase capacity in hot-spot areas Advanced load sharing to increase performance by distributing users between different cells Micro Macro The micro cell can be deployed in: – different frequency as the macro cell – the same frequency band as the macro cell UMTS Presentation - 24
  25. 25. Micro cell evolution scenarioAt some cell radius macrocell (i.e. roof-top antennas) f2capacity growth is limited due to poor RF isolation.Microcells can be added in same or differentfrequency depending on: f2 – rate of traffic increase – distance macro-hot spot – UE velocityUltimately there will be a complete micro-layer f2 UMTS Presentation - 25
  26. 26. Connection set-up/release description Connection Setup and Release includes establishment and release of control plane connections between the UE and UTRAN, and between the UE and the Core Networks. It also covers Radio Access Bearer establishment according to the requested Quality of Service between a Core Network and a UE with established signalling connection, as well as release of existing Radio Access Bearers. The functions consists of two subfunctions – Signaling Connection Setup and Release – Radio Access Bearer Setup and Release UMTS Presentation - 26
  27. 27. Radio connection supervisionBenefit: – Allows an efficient resource utilization – Guarantees that users are not charged for time when they did not have network contact.Description:This feature continuously monitors the status of the radio connection for all connected UEsand disconnects those for which a reasonable quality cannot be maintained and/or the contacthas been lost.The meter for the "unacceptable quality" depends on measurements performed on up-linkphysical channels as well as duration of disturbance or loss of contact. Typically the metersare set such that the quality is considered unacceptable only when there has been no workingcontact with the UE for a few seconds for DCH connected and several minutes for cellconnected.If the quality is considered unacceptable or the UE is considered lost, the radio network willrequest the deletion of all connections towards this UE. Thereby all Radio bearers and RABsallocated for this UE are disconnected. Logical, HW and SW resources related to thesechannels/bearers are also released. UMTS Presentation - 27
  28. 28. Soft/softer Handover overview Algorithm –Relative thresholds minimizes the number of mobiles in soft handoverB A C/I Add margin Drop margin Add B Delete A Time UMTS Presentation - 28
  29. 29. Soft Handover Soft handover essential for power control Soft handover reception – combines signals from RBS in the RNC RNC RBS 1 RBS 2 UMTS Presentation - 29
  30. 30. Softer Handover Softer handover reception – combines signals from two or more sectors in one RBS RBS UMTS Presentation - 30
  31. 31. Characteristics of soft/softer handover RNC controls the UE measurements (i.e. what to measure, report type, what to report and the monitoring set) UE measures on CPICH (Ec/No, RSCP or path loss) UE evaluates measurements (event driven or periodic) RNC evaluates which cells to add/replace/remove from active set (max size is 4) RNC executes the handover decision and provides UE with new neighbor list UMTS Presentation - 31
  32. 32. PagingPurpose:Paging enables the CN to page UEs for terminating servicerequest or for the UTRAN to reach the UE to trigger a UEstate transition. The function will also broadcast modifiedsystem information to all UEs.The following cases are handled by the paging function: – CN originated when UE in idle mode – CN originated when UE in connected mode. – UTRAN originated to trigger a UE state transition. – UTRAN originated to trigger a UE to read updated system in- formation. UMTS Presentation - 32
  33. 33. Cell Update Purpose: Using common or paging channels are important to allow an efficient management of resources for always connected low intensity packet traffic. The feature "Cell Update" is used to allow mobility, cell reselection ("hard handover") and efficient paging of UEs in such states. Benefit: – Support the mobility for UEs on common or paging channels. – Provide a high success rate and efficient management of resources for paging to CELL_PCH connected UEs (PCH is Paging Channel). UMTS Presentation - 33
  34. 34. URA_PCH StateNew state called RRC Connected ModeWCDMA RANRegistration Area URA_PCH Cell_PCH(URA_PCH State)Benefit: – Reduce signaling in Cell_FACH Cell_DCH WCDMA RAN due to updates of location of moving mobiles – Simplified paging Idle – Lower UE battery Idle Mode consumption UMTS Presentation - 34
  35. 35. Intersystem Handover GSM - WCDMA WCDMA WCDMA GSM Dual mode UMTS Presentation - 35
  36. 36. Why GSM Interoperability - why GSM Handover? For service and coverage – Initially to provide “seamless service” to UMTS users For load sharing between frequencies and Radio Access Technologies (RAT) – Increase capacity pool size – GSM network full used For fair behavior in shared network solutions To allow access to unique bearers UMTS Presentation - 36
  37. 37. GSM Intersystem Handover Inter frequency measurements are needed to support inter system handover Compressed mode supports these measurements – 3 different types of compressed mode Compressed mode Inter system SF=SF0/2 SF=SF0 SF=SF0 WCDMA GSM Tf = 10 ms time for measurements UMTS Presentation - 37
  38. 38. Compressed Mode - 3 different types Different alternatives with different impacts Lower spreading factor + Same user data rate - Power increase - Need to allocate a code with half spreading factor 1) Allocate code in the same code tree - remain code orthogonality 2) Allocate code in another code tree - easy to get codes Puncturing + Same user data rate can be used + Remain on the same spreading factor (code) - Power increase - Weakens Forward Error Correction (FEC) coding Higher layer scheduling + Power increase can be avoided - Lower user data rate UMTS Presentation - 38
  39. 39. Control of Inter Radio Access TechnologyCell ReselectionUMTS to GSM : Neighbour Cell List Quality measure • CPICH (RSCP or CPICH Eb/N0) For each neighbour Cell Reseletion criteria • Serving cell quality limit to start neighbor cell measurements • Minimum required signal level to allow selection • Minimum required quality of to allow selection (For FDD cells) • Offset between serving cell and neighbor cell • Hysteresis of the serving cell for ranking of cells • Time to trigger cell reselection UMTS Presentation - 39
  40. 40. Intersystem Traffic Control Always Best ConnectedReal time changes of Connection & Cell WCLink adaptation and control as well as inter-system, service DM Abased load sharing.Based on existing and currently standardized, Iur-g,interfaces. EFunctionality for: RNC /EDG M- Handover Control GS- Admission Control- Load Control Core Network- Service Differentiation BSCEnsure full utilization ofspectrum and system atmaximum performance. UMTS Presentation - 40
  41. 41. Load Balance GSM-UMTS System Features for Traffic Control and Efficiency as Function of Time100% Achieved Load-balancing Efficincy • Self Configuring Radio Network with Dynamic Cell Reselection Control • Real time load Balancing, Iur-g • O&M load Management • Combined Configuration Management, CCM • Service based Directed Retry • Load Control •Congestion triggered Handover WCDMA to GSM •System preference based Handover from WCDMA to GSM • Symmetric Handover Algorithms in GSM and WCDMA • Congestion triggered Handover from GSM to WCDMA Dual-mode Handset • System preference based Handover from GSM to WCDMA penetration • Coverage based Handover from WCDMA to GSM (GSM/EDGE-WCDMA) • Cell Reselection Idle& PS • Congestion hold-down Time UMTS Presentation - 41
  42. 42. Transparent message transfer Supports the transfer of signaling and other messages between a UE and the core network nodes, MSC and SGSN. Basic feature required for UE signaling, e.g. for call set-up Provides support for SMS Description In UMTS, the radio access network need to transfer signaling messages (Non Access Stratum) transparently between the UE and either of the core network domains for establishing and releasing calls. Such transparently transferred messages are also used for other purposes, e.g. LA/RA updating and support SMS services. UMTS Presentation - 42
  43. 43. System Information distribution Allows the UE to get access to updated System Information, which in turn is necessary for correct network behavior. Description The system information is regularly broadcast to the UEs on Broadcast Channel. The information is relates to: – Power control, both Common and dedicated channels, e.g. UL interference – RRC connection parameters e.g. timers and counters – Adjacent cell configuration parameters. – UE Measurements e.g. to support handover evaluation – Location Area and Routing Area – Common channel configuration – Cell selection and re-selection UMTS Presentation - 43
  44. 44. Node and network synchronizationNode synchronization: The Node Synchronization function contains four sub-functions: – Holding of and generation of node reference time in the RNC and the RBSs, – Measurement of phase difference between the frame reference time in the RNC and the frame reference time in each RBS. – A database of measured phase differences to each RBS is held, and an estimate of the accuracy of each of the measurement. – Supervision of drifting frame reference times in the nodes. Generation of node reference time and phase measurement are handled by a device, the Timing Unit (TU), present in both RNC and RBS. UMTS Presentation - 44
  45. 45. Node and network synchronizationNetwork synchronization: The RBS and RNC internal clocks can be synchronized either to: – the transport network or to – an external high stability clock reference. RBSs and RNCs both have stable clocks locked to the reference carried over the transmission network. The clocks, besides synchronizing internal functions in the node, also generate sync to the outgoing transmission links and to the radio transmission. It is possible to cascade up to 5 clocks (Nodes) One primary and up to seven secondary synchronization reference links can be configured for each node The network synchronization (clock) function can be configured to be redundant or non-redundant. UMTS Presentation - 45
  46. 46. Integrity protection and ciphering mode control Integrity protection handles: – the control of integrity protection of control plane data – co-ordination of integrity keys between different core networks (PS and CS). The integrity protection maintains access link data integrity between the SRNC and UE. Ciphering Mode Control handles: – the control of ciphering of user plane and control plane data – co-ordination ciphering keys between different core networks (PS and CS). The ciphering is performed for secure data confidentiality between the SRNC and UE UMTS Presentation - 46
  47. 47. IOT certification for Iu/Iur Iu is the most Vendor-A Vendor-B common 3G multi- 3G system 3G system vendor interface 3G CN 3G CN Enables an operator to choose Iu Iu (several) RAN Iu Iu suppliers RAN RAN UMTS Presentation - 47
  48. 48. High Speed Downlink Packet Access (HSDPA) Requirements – High peak data rates (8-10 Mbps) – Higher throughput – Lower delay Introduction of a new High Speed Downlink Shared Channel (part of 3GPP Rel.5) – Exists in downlink only – Always associated with a dedicated physical channel (DPCH) pair D PC H HS-DS C H UMTS Presentation - 48
  49. 49. Mulitcode to allow bit rates >384 kbit/s One user has more than one channelization code One user can than have several data streams to achieve bit rates above 384kbit/s Primary Data 1 TPC TFCI Data 2 PilotDPCCH/DPDCH Additional Data 3 Data 4DPCCH/DPDCH Additional Data N-1 Data NDPCCH/DPDCH UMTS Presentation - 49
  50. 50. The use of codes in WCDMA Single cell view: – all mobiles need to share the same frequency carrier in WCDMA – orthogonal codes separate between the users and between different communication channels to one user (multi-code operation) Channelization codes Network view: – nearly orthogonal codes to distinguish between the communication channels from different RBS’s – One scrambling code per sector and per carrier e.g a 3x2 RBS has 6 scrambling codes Scrambling codes UMTS Presentation - 50
  51. 51. Multiple scrambling codes overview Each sector/carrier (cell) broadcasts a unique cell ID code -> downlink scrambling code With multiple scrambling codes -> there is more than one downlink scrambling code per sector/carrier (cell) Cell #1, ID code 1 Cell #1, ID code 2 Cell #2, ID code 1 Cell #2, ID code 2 Cell #3, ID code 1 Cell #3, ID code 2 UMTS Presentation - 51
  52. 52. Multiple scrambling code benefit Multiple scrambling codes gives more than one channelization code tree per sector/carrier The problem with code shortage is removed. 1 1 11 11 10 10 1111 1111 1100 1100 1010 1010 1001 100111111111 11110000 11001100 11000011 10101010 10100101 10011001 1001011011111111 11110000 11001100 11000011 10101010 10100101 10011001 10010110 UMTS Presentation - 52
  53. 53. Power Scheduling load max planned loadExtra capacitycan be given topacket data users time Load sharing in time results in a high capacity – Continuous update of the transport format for the interactive RABs both in UL and DL – The aim is to maximize the bit rate for the interactive users Smooth interference levels in the system – Optimize the usage of the radio capacity in the system e.g DL power, without exceeding the maximum planned load UMTS Presentation - 53