1 / 44

Two-Stage Dynamic Uplink Channel and Slot Assignment for GPRS

Two-Stage Dynamic Uplink Channel and Slot Assignment for GPRS. Author: Ying-Dar Lin, Yu-Ching Hsu, Mei-Yan Chiang Reporter: Chen-Nien Tsai. Outline. GPRS Background Introduction Two-Stage Dynamic Channel and Slot Assignment Results Summary. GPRS Background.

lucia
Download Presentation

Two-Stage Dynamic Uplink Channel and Slot Assignment for GPRS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Two-Stage Dynamic Uplink Channel and Slot Assignment for GPRS Author: Ying-Dar Lin, Yu-Ching Hsu, Mei-Yan Chiang Reporter: Chen-Nien Tsai

  2. Outline • GPRS Background • Introduction • Two-Stage Dynamic Channel and Slot Assignment • Results • Summary

  3. GPRS Background • GPRS Introduction • GPRS Network Architecture • GPRS Air Interface • GPRS Logical Channels • Mapping Logical Channels to Physical Channels • Packet Data Transfer Operations

  4. GPRS Introduction • GPRS: • Stands for General (or generic) Packet Radio Services • developed by European Telecommunication Standard Institute (ETSI) • is one of the standards of Global System for Mobile communications (GSM) Phase 2+ • is designed as a packet switching system

  5. GPRS Network Architecture • It fits in with the existing GSM PLMN • Two new network elements • Serving GPRS Support Node (SGSN) • Gateway GPRS Support Node (GGSN) • Many new interfaces • Gb, Gi, Gn, etc.

  6. GPRS Network Architecture

  7. GPRS Air Interface (1/3) • GPRS uses the existing GSM resources. • GPRS uses a two-dimensional access scheme (FDMA and TDMA). • Total 25 MHz bandwidth • 125 carrier frequencies of 200 kHz bandwidth • GPRS users will share the same TDMA frame with GSM voice users. • GPRS air interface will dynamically allocate resources (timeslots).

  8. GPRS Air Interface (2/3) • TDMA Frame • 8 timeslots • Period = 4.615 ms

  9. GPRS Air Interface (3/3)52 Multiframes

  10. GPRS Logical Channels PDCH is the generic name for the physical channel allocated to carry packet logical channels

  11. Mapping Logical Channels to Physical Channels (1/3) • Logical channels are carried on physical channels. • Multiple logical channels can be mapped onto the same physical channels. • Three possible combinations: • PBCCH+PCCCH+PDTCH+PACCH+PTCCH • PCCCH+PDTCH+PACCH+PTCCH • PDTCH+PACCH+PTCCH

  12. Mapping Logical Channels to Physical Channels (2/3)

  13. Mapping Logical Channels to Physical Channels (3/3)

  14. Packet Data Transfer Operations • Before data can transfer • GPRS Attachment • PDP (Packet Data Protocol) context activation. • After these two steps, the mobile can access the network, request resources, and send data.

  15. Uplink Packet Data Transfer • Request resources

  16. Uplink Packet Data Transfer • Fixed radio block allocation • According to bit map

  17. Uplink Packet Data Transfer • Dynamic radio block allocation • USF (Uplink State Flag) is attributed to each MS.

  18. Outline • GPRS Background • Introduction • Two-Stage Dynamic Channel and Slot Assignment • Results • Summary

  19. Introduction • Two-stage assignment • Stage-1: BS assigns several PDCHs to an MS. • Stage-2: BS selects one of the multiplexed MSs in a PDCH to use the radio resource. • Objective of this paper • Load balance in stage-1 • Good prediction in stage-2

  20. Outline • GPRS Background • Introduction • Two-Stage Dynamic Channel and Slot Assignment • Results • Summary

  21. Two-Stage Dynamic Channel and Slot Assignment • Stage 1 • Multiple PDCHs with the corresponding USFs are assigned to an MS. • Stage 2 • To utilize the radio resource, the BS has to predict who has data to send and the assign the following time slot to that MS.

  22. Stage-1 Channel Assignment • After receiving the Packet Channel Request, BS must decide the number of as well as which specific PDCHs to be assigned to the MS. • Deciding which PDCHs to assign is more critical. (load balance) • Two load measurement methods • Number of Assigned Flow • Effective transmission over last cycle

  23. Number of Assigned Flow (NoAF) • The number of multiplexed MSs within a PDCH is chosen as the load measurement metric. • This scheme can be considered a frequency-wise and PDCH-wise balance.

  24. Effective Transmission over Last Cycle (EToLC) • The load metric employed by EToLC is defined as the number of transmissions occurred during the previous PRR (Pure Round-Robin) cycle.

  25. Stage-2 Slot Assignment • The BS has to predict who has data to send. • If the selected MS has no data impending, the slot is wasted. • Three schemes are considered: • Pure Round-Robin • Round-Robin with Linearly-Accumulated Adjustment • Optimal

  26. Pure Round-Robin (PRR) • Each multiplexed MS in a PDCH is round-robined to use the uplink channel. • All MSs are assumed having impending data to send. • A PRR cycle equals the number of MSs multiplexed in this PDCH. • The highest mis-selection rate.

  27. Round-Robin with Linearly-Accumulated Adjustment (RRLAA) • Basis principle • to reduce the transmission chance for the MSs that failed to utilize the last assigned slot, and increase the chance for those who had. • For RRLAA, a Penalty cycle and a Reward cycle are defined and appear alternately.

  28. Penalty Cycle (1/2) • A Penalty cycle is derived from PRR cycle by skipping MSs who waste their last assigned timeslots in Penalty cycles. • An MS will be skipped in n successive penalty cycles when it wastes n successive assigned timeslots in Penalty cycles. • When the MS begins to send packets, the penalty accumulation is reset.

  29. Penalty Cycle (2/2) M: number of multiplexed MS in a PDCH

  30. Reward Cycle (1/2) • An MS is authorized to transmit during the following Reward cycle if it transmits data in the previous Penalty cycle. • An MS will be rewarded n timeslots in a Reward cycle when it successively employs the assigned timeslots in n penalty cycles. • An MS will be selected to send data at most once in a Penalty cycle but possibly multiple times in a Reward cycle.

  31. Reward Cycle (2/2) Infinite loop?

  32. Optimal (OPT) • Assume that whether an MS has data to send or not is known in advance. • For compare performance.

  33. Outline • GPRS Background • Introduction • Two-Stage Dynamic Channel and Slot Assignment • Results • Summary

  34. Results • Comparison between Load Balancing Schemes for Stage-1 Channel Assignment • Comparison between Selection Schemes for Stage-2 Slot Assignment

  35. Comparison for Stage-1 Channel Assignment (1/3) • FNoP-NoAF is designed to be compared with other three models and is considered as the most load-balanced case. RND: Random FNoP: Fixed Number of PDCH (?) NoAF: Number of Assigned Flow EToLC: Effective Transmission over Last Cycle

  36. Comparison for Stage-1 Channel Assignment (2/3) • Standard deviation of PDCH utilization

  37. Comparison for Stage-1 Channel Assignment (3/3) • System throughput

  38. Comparison for Stage-2 Slot Assignment (1/3) • Mis-selection rate

  39. Comparison for Stage-2 Slot Assignment (2/3) • System throughput throughput ≈ offered load * ( 1 – mis-selection rate)

  40. Comparison for Stage-2 Slot Assignment (3/3) • Average Packet Queuing Delay

  41. Outline • GPRS Background • Introduction • Two-Stage Dynamic Channel and Slot Assignment • Results • Summary

  42. Summary (1/2) • Two load-balancing schemes for stage-1 channel assignment. • Number of Assigned Flow (NoAF) • Effective Transmission over Last Cycle (EToLC) • EToLC outperforms NoAF.

  43. Summary (2/2) • One selection scheme for stage-2 slot assignment. • Round Robin with Linearly-Accumulated Adjustment (RRLAA). • Reward and penalty cycles. • RRLAA has the lower mis-selection rate, better system throughput, and lower packet queuing delay.

More Related