1 / 22

Efficient Opportunistic Retransmission Protocol Design

This paper outlines the design, implementation, and evaluation of an efficient opportunistic retransmission protocol for wireless networks. It covers link quality estimation, protocol design, collision handling, fairness, and evaluation methods in detail. The protocol involves relay qualification, selection, prioritization, and retransmission strategies for improved performance. Evaluation includes emulation in various environments and real-world scenarios.

mickey
Télécharger la présentation

Efficient Opportunistic Retransmission Protocol Design

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. Design, Implementation and Evaluation of an Efficient Opportunistic Retransmission Protocol Mei-Hsuan Lu Peter SteenkisteTsuhan Chen MobiCom 09

  2. Outline • Introduction • Estimating link quality • Protocol design • Collision and fairness • Multi-rate PRO • Evaluation

  3. Introduction • PRO - Protocol for Retransmitting Opportunistically • IEEE 802.11 WLAN • S<->D distance R S D

  4. Estimating link quality • Monitor success or failure of probe messages • Respond slowly to channel dynamics • Require extra bandwidth • Monitor SNR of packets at receiver • RSSI (received signal strength indicator) • Noisy • Thh

  5. Estimating link quality

  6. Protocol design • Relay qualification • Relay selection • Relay prioritization • Retransmission

  7. Protocol design • Relay qualification • Relay->destination ≠ destination->relay • Thh, on-line calibration • Relay selection (eligible relay) • Broadcast “I am qualified relay!” • Select the node has highest RSSI w.r.t destination • Add node nest highest … • Until the prob. of having a node hearing source > threshold Thr

  8. Protocol design • Relay prioritization • Higher RSSI w.r.t destination -> higher priority -> smaller CWmin(contention window size) • Retransmission • Lack of ACK -> retransmit • Retransmission fail -> double CW, contend for channel again • Terminate: an ACK heard or retry limit reached or a new packet arrived • Re-ACK : to avoid collision, send “null” data packet

  9. Collision and fairness • Collision • Limiting number of eligible relays • Fairness • More relays, more likely to gain access to channel • Mitigate unfairness: large initial CW, non uniform selection of time slot in CW

  10. Multi-rate PRO • Rate adaption – reduce packet error rate by lowering bitrates (no relay) • SampleRate : probe-based • CHARM : SNR-based • Combine PRO with CHARM • Transmission failed : eligible relay retransmit when its rate ≥ source rate (having better link quality) • Aggressive rate selection

  11. Evaluation • Emulation • Static • Overall • Per-relay • Mobile • fairness • Real world • Office building • Student lounge • 802.11g with multi-rate PRO

  12. Emulation - static • 3 environment scenarios • Freespace (outdoor) • Fading_k5 (small fading) • Fading_k0 (severe fading) • 5 mechanisms • 802.11 • 802.11 with CHARM • 802.11 with SampleRate • Mesh • Optimal PRO

  13. Overall

  14. Thr works well!

  15. Per-relay

  16. Emulation - mobile D S

  17. Emulation - fairness D1 D1 S1 S2 D2 S1 S2 D2 100m 100m 100m 50m

  18. Real world • Office building • Night • Student lounge • Day • Severe fading • Experiment • 10 laptops as nodes • Take turns as the source and send packet to other 9 nodes one by one • Nodes other than source and destination serve as relay

  19. High contention High fading

  20. Real world – 802.11g with multi-rate PRO High contention High fading

More Related