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Performance Analysis of Traffic Differentiation in Wireless Networks through Simulation

This document presents the results of simulations conducted to analyze traffic differentiation in wireless networks using the Berkeley NS2 software. It details the use of high-priority traffic categories, CWmin assignment, and QIFS settings in various load scenarios. A series of simulations reveal the system's behavior under different conditions, illustrating bandwidth usage, latency, and latency distribution. Comparisons are made with legacy DCF mechanisms. Results include comprehensive graphs for bandwidth, per-frame latency, and packet latency distribution.

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Performance Analysis of Traffic Differentiation in Wireless Networks through Simulation

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  1. VDCF Simulations Greg Chesson, greg@atheros.com Aman Singla, aman@atheros.com G. Chesson, A. Singa - Atheros

  2. Overview • Notation • Load(a,b,c) means there area highest-priority stations, b at the next priority, c at the next priority, etc. May be shown as L(a,b,c,d). • CWmin(a,b,c) describes the assignment of CWmins to Traffic Categories where a is assigned to the highest priority, b at the next, etc. May be shown as W(a,b,c,d). • QIFS(a,b,c), or Q(a,b,c), captures the setting of the QIFS[i] values by TC. • Simulation Software • Public version of the Berkeley NS2 software suite • Contact authors for details • Results • Usually 3 graphs per simulation • BW - An instantaneous bandwidth slot for one or more flows • LAT – a per-frame latency plot over the lifetime of the run • Lat-dist – latency distribution (i.e P% of the packets had latency less than x) • Scenarios • Usually fixed topology, varying load • Stations are added or removed usually on 3-sec intervals G. Chesson, A. Singa - Atheros

  3. Scenarios • Basic differentiation demonstration and comparison with legacy DCF • Load(4,2,10) – phones, 2 videos, 10 background stations • Load(4,4,8) – constant demand from stations, uses same W/Q settings as scenario (2), demonstrates robust behavior of mechanism • Extreme differentiation: 8 active TCs G. Chesson, A. Singa - Atheros

  4. Scenario 1 • A simple scenario meant only to compare with DCF and to observe the effects of CWmin and QIFS controls. • Load(2,4): two high-priority stations and 4 low-priority stations, all stations with backlogged queues (always ready to transmit) using UDP datagrams. • Topology: an AP is sinking all traffic from the 6 stations. • Simulation Runs (3 plots for each run: bw, lat, lat-dist): • DCF only - for comparison • W(15,31) Q(0,0) - uses CWmin but not QIFS • W(15,15) Q(0,1) - uses QIFS but not CWmin G. Chesson, A. Singa - Atheros

  5. 1 a bw Per-flow Dropped packet counts for IFQ/MAC IFQ means dropped from software queue MAC means retry count exceeded G. Chesson, A. Singa - Atheros

  6. 1 a lat G. Chesson, A. Singa - Atheros

  7. 1 a lat-dist G. Chesson, A. Singa - Atheros

  8. 1 b bw G. Chesson, A. Singa - Atheros

  9. 1 b lat G. Chesson, A. Singa - Atheros

  10. 1 b lat-dist G. Chesson, A. Singa - Atheros

  11. 1 c bw G. Chesson, A. Singa - Atheros

  12. 1 c lat-dist G. Chesson, A. Singa - Atheros

  13. Scenario 2 • Load(4,2,10) • 4 phone-like CBR flows (100 Kbit/s with 120B frames) • Bidirectional flows: 2 Stations plus AP, 4 flows, each STA is source+sink • 2 video-like CBR flows: 1 at 3 Mbit/s, 1 at 8 Mbit/s • 10 background flows: 5 UDP and 5 TCP • All other flows sink to AP unless specified otherwise • New station added every 3 sec. • Stations removed in same order after peak load is reached • Runs • W(15,15,31) Q(0,2,7) • W(15,15,31) Q(0,0,7) • W(15,15,31) Q(0,2,7) - video flows sourced at AP G. Chesson, A. Singa - Atheros

  14. 2 a bw videos Remove loads background phones G. Chesson, A. Singa - Atheros

  15. 2 a lat statistics video phone G. Chesson, A. Singa - Atheros

  16. 2 a lat-dist G. Chesson, A. Singa - Atheros

  17. 2 a vdcf-background vs dcf-background G. Chesson, A. Singa - Atheros

  18. 2 b bw Background flows not shown G. Chesson, A. Singa - Atheros

  19. 2 b lat G. Chesson, A. Singa - Atheros

  20. 2 b lat-dist G. Chesson, A. Singa - Atheros

  21. 2 c bw video sourced at AP Background flows not shown G. Chesson, A. Singa - Atheros

  22. 2 c lat video sourced at AP Lower latency than 2 b lat. Fewer phone-video collisions than 2-b. G. Chesson, A. Singa - Atheros

  23. 2 c lat-dist video sourced at AP G. Chesson, A. Singa - Atheros

  24. Scenario 3 • Load(4,4,8) – differentiation test using same W/Q as scenario 2 • 4 high priority stations, 4 middle priority, 8 low priority • All stations sending with backlogged queues to AP • Stations are sequenced on at 3-sec intervals, high-priority stations first • Stations are sequenced off after peak load is attained • Demonstrates good differentiation without needing to adjust W/Q • Uses W(15,15,31) Q(0,2,7) - same as scenario 2 • Uses W(15,15,15) Q(0,1,2) - different recipe G. Chesson, A. Singa - Atheros

  25. 3 a bw G. Chesson, A. Singa - Atheros

  26. 3 b bw G. Chesson, A. Singa - Atheros

  27. 3 a lat G. Chesson, A. Singa - Atheros

  28. 3 b lat G. Chesson, A. Singa - Atheros

  29. 3 a lat-dist G. Chesson, A. Singa - Atheros

  30. 3 b lat-dist G. Chesson, A. Singa - Atheros

  31. Scenario 4 • 8 streams, 8 TCs • Backlogged queues G. Chesson, A. Singa - Atheros

  32. 4 bw G. Chesson, A. Singa - Atheros

  33. 4 lat G. Chesson, A. Singa - Atheros

  34. 4 lat-dist G. Chesson, A. Singa - Atheros

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