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Impact of IEEE 802.11n Operation On IEEE 802.15.4 Performance

Impact of IEEE 802.11n Operation On IEEE 802.15.4 Performance. Authors:. Date: 2008-11-11.

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Impact of IEEE 802.11n Operation On IEEE 802.15.4 Performance

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  1. Impact of IEEE 802.11n Operation On IEEE 802.15.4 Performance Authors: Date: 2008-11-11 Notice:This document has been prepared to assist IEEE 802.19. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Mukul Goyal, U Wisconsin Milwaukee

  2. Abstract In this presentation, we evaluate the impact of IEEE 802.11n operation on IEEE 802.15.4 performance via test bed experiments. The IEEE 802.15.4 performance is measured in terms of packet loss rate and the latency for successfully delivered packets. Mukul Goyal, U Wisconsin Milwaukee

  3. IEEE 802.15.4: Overview • A MAC/PHY layer protocol for low power, low data rate (< 250 kbps) wireless sensor applications • Based on CSMA/CA Mukul Goyal, U Wisconsin Milwaukee

  4. The CSMA/CA algorithm in (unslotted) 802.15.4 • The source node backoffs for a random number of slots between 0 and (2^BE) – 1 • BE is Backoff Exponent • After the backoff, the source node does the clear channel assessment (CCA) • If the channel is not idle (CCA Failure), the source node increments BE and repeat the process up to 4 times • The initial BE value is 3 and max BE value is 5 Mukul Goyal, U Wisconsin Milwaukee

  5. The CSMA/CA algorithm in (unslotted) 802.15.4 • If the CCA fails even after 4th retry, the source node declares channel access failure (CAF) and abandons the packet transmission • If the CCA succeeds, the source node transmits the packet. • On receiving the packet, the destination optionally sends an acknowledgement back Mukul Goyal, U Wisconsin Milwaukee

  6. Collisions and Retransmissions • If the packet or the ack suffers a collision, the source node waits for a certain time duration and then repeats the (backoff + transmission) process up to 3 more times. • If the ack is not received even after the 3rd retry, the source node declares a collision failure and abandons the packet. Mukul Goyal, U Wisconsin Milwaukee

  7. Packet Loss in IEEE 802.15.4 • Channel access failure • channel access failure occurs after 5 back-to-back CCA failures during a try. • Collision failure • occurs after failure to receive the ack even after 4 tries. • Note that a channel access failure causes abandonment of packet transmission attempt even if 4 tries have not been made. Mukul Goyal, U Wisconsin Milwaukee

  8. Impact of IEEE 802.11n operation on IEEE 802.15.4 Performance • IEEE 802.15.4 performance is measured in terms of the packet loss rate and latency for successfully delivered packets. • We plot the increase in average loss rate/latency values for IEEE 802.15.4 nodes due to the presence of an IEEE 802.11n network. Mukul Goyal, U Wisconsin Milwaukee

  9. The 802.15.4-802.11 Test Bed: Top View 10” 12” 12” 12” 12” 6” 2” 802.15.4 node 6” 9” 9” 802.11 node 802.15.4 Coord 802.11 AP 9” 9” 40” 9” 9” 9” 9” 70” Mukul Goyal, U Wisconsin Milwaukee

  10. The 802.15.4-802.11 Test Bed: Front View 802.15.4 node 802.11 AP 9” 6” 802.11 node 802.15.4 Coord 3” Mukul Goyal, U Wisconsin Milwaukee

  11. Traffic in IEEE 802.15.4 Network • 15 nodes sending packets to the coordinator. • The packet size is 112 bytes. • Each node sends on average one packet per second (poisson distributed) for 15 minutes • IEEE 802.15.4 network uses a 3 MHz wide channel centered at 2425 MHz (Channel 15) • Power level: 10dBm Mukul Goyal, U Wisconsin Milwaukee

  12. Traffic in IEEE 802.11n Network • An iperf client sends a UDP stream to an iperf server over an IEEE 802.11n network • Power level 17dBm • Packet size: 1470 B, 63 KB • Client generates traffic at different rates • The 802.11n AP and cards follow draft 2.0 • The cards use OFDM, 64-QAM with coding rate of 5/6 • The PHY rate was 270Mbps Mukul Goyal, U Wisconsin Milwaukee

  13. IEEE 802.11n Channels Used • Scenario 1: Channel 6, 40 MHz wide (extends towards channel 11), no overlap with IEEE 802.15.4 channel • Scenario 2: Channel 1, 40 MHz wide, extends into the channel used by IEEE 802.15.4 network • Scenario 3: Channel 4, 20 MHz wide, overlaps the channel used by IEEE 802.15.4 network Mukul Goyal, U Wisconsin Milwaukee

  14. Scenario 1: IEEE 802.11n on Channel 6, 40 MHz wide Control Channel Mukul Goyal, U Wisconsin Milwaukee

  15. Mukul Goyal, U Wisconsin Milwaukee

  16. Scenario 1: Changes in IEEE 802.11n Traffic Load During an Experiment Mukul Goyal, U Wisconsin Milwaukee

  17. Scenario 1: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Loss Rate Mukul Goyal, U Wisconsin Milwaukee

  18. Scenario 1: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency Mukul Goyal, U Wisconsin Milwaukee

  19. Scenario 2: IEEE 802.11n on Channel 1, 40 MHz wide Mukul Goyal, U Wisconsin Milwaukee

  20. Mukul Goyal, U Wisconsin Milwaukee

  21. Scenario 2: Changes in IEEE 802.11n Traffic Load During an Experiment Mukul Goyal, U Wisconsin Milwaukee

  22. Scenario 2: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Loss Rate Mukul Goyal, U Wisconsin Milwaukee

  23. Scenario 2: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency Mukul Goyal, U Wisconsin Milwaukee

  24. Scenario 3: IEEE 802.11n on Channel 4, 20 MHz wide Mukul Goyal, U Wisconsin Milwaukee

  25. Scenario 3: Changes in IEEE 802.11n Traffic Load During an Experiment Packet Payload: 1470B Mukul Goyal, U Wisconsin Milwaukee

  26. Scenario 3: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Loss Rate Mukul Goyal, U Wisconsin Milwaukee

  27. Scenario 3: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency Mukul Goyal, U Wisconsin Milwaukee

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