Impact of IEEE 802.11n Operation On IEEE 802.15.4 Performance November 2008 doc.: IEEE 802.11-yy/xxxxr0 November 2008 Impact of IEEE 802.11n Operation On IEEE 802.15.4 Performance Date: 2008-11-02 Authors: 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 Mukul Goyal, U Wisconsin Milwaukee

November 2008 doc.: IEEE 802.11-yy/xxxxr0 November 2008 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 Mukul Goyal, U Wisconsin Milwaukee

November 2008 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

The CSMA/CA algorithm in (unslotted) 802.15.4 November 2008 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

The CSMA/CA algorithm in (unslotted) 802.15.4 November 2008 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

Collisions and Retransmissions November 2008 Collisions and Retransmissions If the packet or the ack suffers a collision, the source node waits for a certain time duration and then repeat 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

Packet Loss in IEEE 802.15.4 Channel access failure Collision failure November 2008 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

Impact of IEEE 802.11n operation on IEEE 802.15.4 Performance November 2008 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. In the following graphs, 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

Traffic in IEEE 802.15.4 Network November 2008 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

Traffic in IEEE 802.11n Network November 2008 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 bytes Client generates traffic at rates 1, 2, 5, 10, 15, 20 Mbps. Mukul Goyal, U Wisconsin Milwaukee

November 2008 IEEE 802.11n Channels Used Scenario 1: Channel 1, 20 MHz wide, no overlap with IEEE 802.15.4 channel Scenario 2: Channel 6, 40 MHz wide (extends towards channel 11), no overlap with IEEE 802.15.4 channel Scenario 3: Channel 1, 40 MHz wide, extends into the channel used by IEEE 802.15.4 network Scenario 4: Channel 4, 20 MHz wide, overlaps the channel used by IEEE 802.15.4 network Mukul Goyal, U Wisconsin Milwaukee

Scenario 1: IEEE 802.11n on Channel 1, 20 MHz wide November 2008 Scenario 1: IEEE 802.11n on Channel 1, 20 MHz wide IEEE 802.11n IEEE 802.15.4 2412 MHz 2425 MHz 22MHz 3MHz Mukul Goyal, U Wisconsin Milwaukee

November 2008 Scenario 1: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Loss Rate Mukul Goyal, U Wisconsin Milwaukee

Scenario 1: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency November 2008 Scenario 1: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency Mukul Goyal, U Wisconsin Milwaukee

Scenario 2: IEEE 802.11n on Channel 6, 40 MHz wide November 2008 Scenario 2: IEEE 802.11n on Channel 6, 40 MHz wide IEEE 802.11n IEEE 802.15.4 2425 MHz 2437 MHz 3MHz 44MHz Mukul Goyal, U Wisconsin Milwaukee

November 2008 Scenario 2: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Loss Rate Mukul Goyal, U Wisconsin Milwaukee

Scenario 2: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency November 2008 Scenario 2: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency Mukul Goyal, U Wisconsin Milwaukee

Scenario 3: IEEE 802.11n on Channel 1, 40 MHz wide November 2008 Scenario 3: IEEE 802.11n on Channel 1, 40 MHz wide IEEE 802.11n IEEE 802.15.4 2412 MHz 2425 MHz 3MHz 44MHz Mukul Goyal, U Wisconsin Milwaukee

November 2008 Scenario 3: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Loss Rate Mukul Goyal, U Wisconsin Milwaukee

Scenario 3: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency November 2008 Scenario 3: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency Mukul Goyal, U Wisconsin Milwaukee

Scenario 4: IEEE 802.11n on Channel 4, 20 MHz wide November 2008 Scenario 4: IEEE 802.11n on Channel 4, 20 MHz wide IEEE 802.11n IEEE 802.15.4 2425 MHz 2427 MHz 3MHz 22MHz Mukul Goyal, U Wisconsin Milwaukee

November 2008 Scenario 4: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Loss Rate Mukul Goyal, U Wisconsin Milwaukee

Scenario 4: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency November 2008 Scenario 4: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency Mukul Goyal, U Wisconsin Milwaukee