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[Preliminary Simulation Results on Power Saving]

[Preliminary Simulation Results on Power Saving]. Date: 2009-11-19. Authors:. Slide 1. Abstract. This presentation reports the preliminary results of our simulations of existing power saving mechanisms.

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[Preliminary Simulation Results on Power Saving]

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  1. [Preliminary Simulation Results on Power Saving] Date: 2009-11-19 Authors: Slide 1

  2. Abstract • This presentation reports the preliminary results of our simulations of existing power saving mechanisms. • The scenario simulated is taken from IEEE 802 Doc 09/0161r02, Usage Model 2d: Wireless Networking for Office. • The performance and effect of APSD have been examined. Slide 2

  3. Simulation Scenario* Pre-Conditions: Office with people engaged in high quality/high revenue services that involve video and voice interaction with client and transferring large volumes of multimedia data. A single AP serves 5 people. The office comprises 5 – 500 people. Application: Multiple applications run at the same time. High definition compressed video uses something like an Blu-ray codec. Voice is standard definition quality using a codec like G729. Aggregate bandwidth requirement is 5 simultaneous video streams per AP. Voice requirements are: ~50Kbps, Jitter <30msec. Delay <30msec. 1.0E-1 PER. Environment: Mostly not Line of sight within a single office. People walking around the office. There is potentially unmanageable interference from neighboring offices within 100 feet (horizontally) or adjacent floors (vertically) when in 2.4 / 5 GHz. AP density is more than 1 AP per 40m X 40m Traffic Conditions (per AP): 2 WLAN video streams 2 WVoIP streams Up to 5 best effort data streams The best effort data traffic can take up to 20% of the available bandwidth with saturated offered load. Use Case: Users run different applications during the day and may start each application at different time. A typical sequence is starting up a voice call, adding video sending/receiving multi-media data and discussing this over the voice/video link The duration of such a use case is typically one hour. Up to three of these “sessions” per AP may be going on in parallel. * This was taken from Doc 09/0161r02, Usage Model 2d: Wireless Networking for Office Slide 3

  4. Network Topology Slide 4

  5. Traffic Pattern Slide 5

  6. Simulation Parameters The simulation runs on ns2 platform. Slide 6

  7. Performance without Aggregation Note the data here are average numbers over 4 VoIP sessions, 2 Video sessions and 2 TCP sessions. Slide 7

  8. 802.11n Capacity with Video traffic Contention Window PLCP Header Video Frame SIFS DIFS Ack 34 µs 67 µs (min average) 28 µs 16 µs 32 µs Time 1. Video Frame = (Data + IP header + MAC header)/DataRate ( 1500 + 20 + 28 ) * 8 / 500 = 24.768 µs 2. Require Bandwidth = Application Load * Frame Start Interval / Video Frame 50 * (34+67+28+24.768+16+32) / 24 = 420.315 Mbps 3. Number of Video uplink sessions = Bandwidth * Utilization / Require Bandwidth 500 * 0.8 / 420.315 = 1.05 Reference: IEEE 802.11-07/2704r00, Efficiency of VoIP on 802.11n Slide 8

  9. Data Aggregation • In order to support the given traffic load, Aggregated MSDU is used. • In the results after this slide, four video MSDUs are aggregated into one A-MSDU. • VoIP and TCP packets are not aggregated. Slide 9

  10. STA 1 (VoIP only) STA 2 (VoIP only) STA 3 (VoIP, TCP) STA 4 (VoIP, Video) STA 5 (VoIP, Video) APSD Power Saving Effect Slide 10

  11. STA 1 (VoIP only) STA 2 (VoIP only) STA 3 (VoIP, TCP) STA 4 (VoIP, Video) VoIP Traffic Delay with and w/o APSD Note: Jitter for VoIP traffic with APSD is < 2 µs, and <0.1 µs without APSD Slide 11

  12. Uplink w/o APSD Downlink w/o APSD Uplink w/ APSD Downlink w/ APSD Video Traffic Performance Slide 12

  13. APSD’s effect on TCP throughput STA3 (VoIP, TCP) STA5 (Video, TCP) Note: all TCP traffic is uplink traffic Slide 13

  14. VoIP Video TCP Delay Comparison for all Traffic Types Note: 1) the data here are average numbers over 4 VoIP sessions, 2 Video sessions and 2 TCP sessions. 2) there is no data collected for downlink TCP traffic so the data is not available. Slide 14

  15. Summary and Future Works • Summary • A single stream of 500Mbps cannot support the given traffic load. Aggregation gets the job done. • APSD allows STAs sleep >95% of the time for VoIP traffic in this specific scenario; • APSD increases the delay for downlink VoIP traffic (from <1ms to ~10ms), but still within the requirement (<30ms). • APSD slightly increases the delay for video traffic when it is running in the AP. • TCP delay is >20% larger, and throughput is about 10% lower when APSD is running. • Future work • Run the simulation for PSMP (simulator is ready) • Develop module to support direct links so that STA to STA traffic can be simulated. • Support multiple streams (receivers) • Enhanced MAC functions needed. Slide 15

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