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Allocation of Radio Resources to packet-switched traffic in GPRS-like networks

Allocation of Radio Resources to packet-switched traffic in GPRS-like networks. By group 896 Supervisors: Hans Peter Schwefel Patrick Eggers . Students: Xin Zhou Jimena Llorente Martinez Devendra Prasad François Delawarde Gwénaël Coget Haibo Wang.

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Allocation of Radio Resources to packet-switched traffic in GPRS-like networks

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  1. Allocation of Radio Resources to packet-switched traffic in GPRS-like networks By group 896 Supervisors: Hans Peter Schwefel Patrick Eggers Students: Xin Zhou Jimena Llorente Martinez Devendra Prasad François Delawarde Gwénaël Coget Haibo Wang Group 896 GPRS Radio Resource Management

  2. Project Description: • Analyze existing GPRS radio resource management strategies. • Define scenarios and input parameters, for which an algorithm for the assignment of resources to packet-switch traffic will be developed. • Evaluate/validate the algorithm in simplified simulation models. Group 896 GPRS Radio Resource Management

  3. GPRS Introduction: • Reuse the existing GSM infrastructure • Introduce packet-switched routing functionality • Better data transfer rates (multislot capabilities) • Low cost and connectivity-oriented • Migration Path to 3G Networks Group 896 GPRS Radio Resource Management

  4. Comparison between GSM/GPRS Group 896 GPRS Radio Resource Management

  5. GPRS architecture Group 896 GPRS Radio Resource Management

  6. GPRS protocols stack Group 896 GPRS Radio Resource Management

  7. GPRS Protocols: • GSM-RF layer: • Reuse of GSM multiple access methods (TDMA/FDMA) • MAC layer: • Multiplexing • Scheduling • Contention resolution (UL) • RLC layer: • Segmentation/Re-assembly • ARQ Group 896 GPRS Radio Resource Management

  8. Radio Resource Management (RRM) • Introduction -Functions • GSM/GPRS establishment • GSM/GPRS call maintaining • GSM/GPRS release -Dedicated/Shared channels • Best Effort Strategy <-> Our Proposed RRM Strategy • Resource Allocation • Reassignment • Scheduling Group 896 GPRS Radio Resource Management

  9. Best Effort: Access Control Group 896 GPRS Radio Resource Management

  10. Best Effort: Resource Assignment Group 896 GPRS Radio Resource Management

  11. Best Effort: Round Robin Scheduling Group 896 GPRS Radio Resource Management

  12. Proposed Strategy: Access Control Group 896 GPRS Radio Resource Management

  13. Proposed Strategy: Resource Assignment Group 896 GPRS Radio Resource Management

  14. Proposed Strategy: Scheduling Example: TBF G=3  30% TBF G=6  60% TBF G=1  10% Group 896 GPRS Radio Resource Management

  15. Simulation Model Only downlink traffic in 1 micro-cell, Transmission time step was set to 20ms(1 RLC block) Group 896 GPRS Radio Resource Management

  16. Radio Channel Model (1) Path Loss --- global mean power (2) Slow Fading --- local mean power (3) Fast Fading --- instantaneous power (1) Path loss (3) Fast fading (2) Slow fading Group 896 GPRS Radio Resource Management

  17. Mapping Function BLER C/I C/I --- BLER Assumption C/I BLER • Network-level simulator based on link-level simulator • TU3 Model • Reuse pattern 1/3 • Ideal Frequency Hopping • Fast fading is considered Mean BLER CS_x Group 896 GPRS Radio Resource Management

  18. C/I Generation 1. Mean C/I --- Path Loss and Reuse Pattern Path Loss PDF(r) pdf(r)=k*r, 15m<r<500m Group 896 GPRS Radio Resource Management

  19. Reuse Pattern C/I Calculation 4 0: Investigated Cell 1~6: Co-channel Cell D: Reuse Distance R: Cell Radius r: MS-BTS Distance 5 R 0 3 6 r D 2 1 Group 896 GPRS Radio Resource Management

  20. PDF(r) Mean C/I Group 896 GPRS Radio Resource Management

  21. 2. C/I per MS --- Shadowing Effect Lognormal Distribution ( Mean C/I, σ ) C/I for Each Mobile Group 896 GPRS Radio Resource Management

  22. Coding Scheme Selection Throughput vs. C/I • CIR 0~5 CS1 • CIR 6~9 CS2 • CIR 10~16 CS3 • CIR 16~30+ CS4 Group 896 GPRS Radio Resource Management

  23. CS_x C/I BLER Generation Mapping Table BLER Generation Random( ) < BLER Random Seed Block Erroneous Block Correct Random( ) > BLER Group 896 GPRS Radio Resource Management

  24. Frequency Correlation Function Group 896 GPRS Radio Resource Management

  25. Distance Generation Path Loss Mean C/I Shadowing Effect C/I per MS CS_x Selection MS ID pdf(r) Random Seed Block Correct Or Erroneous BLER Mapping Group 896 GPRS Radio Resource Management

  26. Session3 Session1 Session2 Session3 Time[ h] Packet Call1 Packet Call 2 Packet Call 3 Time[ m] Packet 1 Packet 2 Packet 3 Time[ s] Traffic Model The definition of a GPRS session in our model: Group 896 GPRS Radio Resource Management

  27. Traffics: Mixture of GSM Voice calls and GPRS Data sessions Each session/call was randomly assigned to a Mobile Station(MS), where each MS only represent a propagation condition(C/I) corresponding to a certain distance from the BTS. Group 896 GPRS Radio Resource Management

  28. Traffic Generation Method Group 896 GPRS Radio Resource Management

  29. Model Assumptions • 1 session assigned to 1MS corresponding to a certain radio condition • 1MS can have multiple sessions based on radio condition • All the sessions are in the BSS to be transmitted • No Handover • Based on one Cell Configuration • No uplink simulation • Higher layers(TCP/IP, LLC) is not considered • ARQ for uplink is not considered Group 896 GPRS Radio Resource Management

  30. Parameters List Traffic Load = 5 ~ 29 Erlang GSM Voice: Traffic_Load*70%;GPRS Data: Traffic_Load*30% Group 896 GPRS Radio Resource Management

  31. arrival time GPRS SESSION Session size (bits) time CS-x Mapping to block RLC blocks time Mapping GPRS session to RLC blocks Because in simulation the transmission was working on RLC block level. Group 896 GPRS Radio Resource Management

  32. Simulator Implementation • General Structure – Object Oriented • Time-Driven and Event-Motivated Simulation Process – main() and traffic_Model • Propagation Concerned Object – MS and air_Interface • Proposed RRM features VS “Best Effort” • Proposed RRM Object – BSS, FIFO_Priority and resource_Pool Group 896 GPRS Radio Resource Management

  33. BSS Resource Pool Access (); TS assignment (); TBF assignment (); Scheduler (); Resource Update (); Add GSM (); Add GPRS (); Release GSM (); Release GPRS (); Scheduled (); Traffic Model Air Interface Mobile Station Trace FIFO Priority Traffic Generator ( ); Transmission ( ); Update Propagation ( ); Output ( ); Push ( ); Pop ( ); General Structure – Object Oriented Group 896 GPRS Radio Resource Management

  34. T, Length, MS T, Length, MS T, Length, MS T, Length, MS T, Length, MS T, Length, MS Traffic Model GSM events Chain Simulation Process GPRS events Chain T<T_End T_nex t_Frame<T_next_Event? Yes No Transmission Access Resource Update Timer Update Scheduling Output Trace Time-Driven and Event-Motivated Simulation Process Group 896 GPRS Radio Resource Management

  35. Propagation Concerned Object – MS and airInterface MS: Assign C/I, CS, BLER to each mobile station, the process was carried on during the initialization step. Air Interface: Frame[TRX][TS]; During each RLC block transmission, generate a Random “ 0” or “1” representing “correct” or “error” according to the BLER for the MS which occupy current TS/Block. Group 896 GPRS Radio Resource Management

  36. Proposed RRM vs “Best Effort” Group 896 GPRS Radio Resource Management

  37. Session ID, Grade Session ID, Grade Session ID, Grade Session ID, Grade TS data structure TS Type 1: GSM TS Type 2: GPRS TRX0 TRX1 TRX2 Pool[TRX][TS] TRX3 TS0 TS1 TS2 TS3 TS4 TS5 TS6 Proposed RRM Object - 1– BSS, FIFOPriority and resourcePool Resource Pool: store a table for all the TRX-TS. Group 896 GPRS Radio Resource Management

  38. Session ID, Priority Access Queue Priority: High  Low Priority = C/I of each session according to its assigned Mobile Station BSS will always select the first one(highest priority) in queue to assign resources. For two sessions with the same C/I, the new one will be put after the old one(FIFO). Session ID, Priority Session ID, Priority Proposed RRM Object –2 FIFO_Priority: The GPRS access queue based on grade. Queue length = 7 Group 896 GPRS Radio Resource Management

  39. Session ID, Grade Session ID, Grade GSM Sessions GPRS Sessions Session ID, Grade Session ID, Grade Session ID, Grade Session ID, Grade Proposed RRM Object –3 BSS: Manage all the convoyed sessions. • Access Control (Voice Pre-emption) • TS/TBF assignment • Scheduling • Correctly-received RLC blocks counting • Release finished GSM/GPRS or drop GPRS with max retransmissions. • TS re-assignment: after every transmission time step, try to raise the TS numbers for each GPRS session to 4. Group 896 GPRS Radio Resource Management

  40. Performance Evaluation • Simulator validation • Simulations parameters • Simulations results • Future work Group 896 GPRS Radio Resource Management

  41. Simulator Validation • RRM strategies: use of output functions and breakpoints to check the behaviour of access queue, choice of TRX/TS, scheduler, reassignment, pre-emption… • Propagation /Transmission: comparison between the curve used to map C/I, BLER and throughput and the one obtained • Traffic Model: comparison between input parameters and traffic generated (number of sessions per hour, call length, session size…) Group 896 GPRS Radio Resource Management

  42. Simulations Parameters Group 896 GPRS Radio Resource Management

  43. Simulations Results • Throughput per Cell Vs. Traffic Load • Throughput per Session Vs. Traffic Load • Access Delay Vs. Traffic Load • Blocking Rate GPRS Vs. Traffic Load • Throughput per Session Vs. C/I Group 896 GPRS Radio Resource Management

  44. Throughput per Cell Group 896 GPRS Radio Resource Management

  45. Throughput per Session Group 896 GPRS Radio Resource Management

  46. Throughput Per Session Vs. C/I Group 896 GPRS Radio Resource Management

  47. Mean access delay Group 896 GPRS Radio Resource Management

  48. Blocking Rate GPRS Group 896 GPRS Radio Resource Management

  49. Future Work • Consideration of QoS requirements (traffic model with different types of service) • Consideration of Uplink • Investigation of higher layers Group 896 GPRS Radio Resource Management

  50. Thank You ! Group 896 GPRS Radio Resource Management

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