doc.: IEEE /30r2 SubmissionMukul Goyal, U Wisconsin MilwaukeeSlide 1 Impact of IEEE n Operation On IEEE Performance Notice: This document has been prepared to assist IEEE 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. Date: Authors: November 2008

doc.: IEEE /30r2 SubmissionMukul Goyal, U Wisconsin MilwaukeeSlide 2 Abstract In this presentation, we evaluate the impact of IEEE n operation on IEEE performance via test bed experiments. The IEEE performance is measured in terms of packet loss rate and the latency for successfully delivered packets. November 2008

doc.: IEEE /30r2 Submission IEEE : Overview A MAC/PHY layer protocol for low power, low data rate (< 250 kbps) wireless sensor applications Based on CSMA/CA November 2008 Slide 3Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission The CSMA/CA algorithm in (unslotted) 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 November 2008 Slide 4Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission The CSMA/CA algorithm in (unslotted) If the CCA fails even after 4 th 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 November 2008 Slide 5Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission 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 3 rd retry, the source node declares a collision failure and abandons the packet. November 2008 Slide 6Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission Packet Loss in IEEE 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. November 2008 Slide 7Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission Impact of IEEE n operation on IEEE Performance IEEE 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 nodes due to the presence of an IEEE n network. November 2008 Slide 8Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission The Test Bed: Top View November 2008 Mukul Goyal, U Wisconsin MilwaukeeSlide 9 40” 70” 9” 12” node AP node Coord 6” 2” 10” 6”

doc.: IEEE /30r2 Submission The Test Bed: Front View November 2008 Mukul Goyal, U Wisconsin MilwaukeeSlide 10 9” node AP node Coord 6” 3”

doc.: IEEE /30r2 Submission Traffic in IEEE 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 network uses a 3 MHz wide channel centered at 2425 MHz (Channel 15) Power level: 10dBm November 2008 Slide 11Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission Traffic in IEEE n Network An iperf client sends a UDP stream to an iperf server over an IEEE n network Power level 17dBm Packet size: 1470 B, 63 KB Client generates traffic at different rates The n AP and cards follow draft 2.0 The cards use OFDM, 64-QAM with coding rate of 5/6 The PHY rate was 270Mbps November 2008 Slide 12Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission IEEE n Channels Used Scenario 1: Channel 6, 40 MHz wide (extends towards channel 11), no overlap with IEEE channel Scenario 2: Channel 1, 40 MHz wide, extends into the channel used by IEEE network Scenario 3: Channel 4, 20 MHz wide, overlaps the channel used by IEEE network November 2008 Slide 13Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission Scenario 1: IEEE n on Channel 6, 40 MHz wide November 2008 Mukul Goyal, U Wisconsin MilwaukeeSlide 14 Control Channel

doc.: IEEE /30r2 Submission November 2008 Mukul Goyal, U Wisconsin MilwaukeeSlide 15

doc.: IEEE /30r2 Submission Scenario 1: Changes in IEEE n Traffic Load During an Experiment November 2008 Mukul Goyal, U Wisconsin MilwaukeeSlide 16

doc.: IEEE /30r2 Submission Scenario 1: Impact of IEEE n Operation on IEEE Loss Rate November 2008 Slide 17Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission Scenario 1: Impact of IEEE n Operation on IEEE Latency November 2008 Slide 18Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission Scenario 2: IEEE n on Channel 1, 40 MHz wide November 2008 Mukul Goyal, U Wisconsin MilwaukeeSlide 19

doc.: IEEE /30r2 Submission November 2008 Mukul Goyal, U Wisconsin MilwaukeeSlide 20

doc.: IEEE /30r2 Submission Scenario 2: Changes in IEEE n Traffic Load During an Experiment November 2008 Mukul Goyal, U Wisconsin MilwaukeeSlide 21

doc.: IEEE /30r2 Submission Scenario 2: Impact of IEEE n Operation on IEEE Loss Rate November 2008 Slide 22Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission Scenario 2: Impact of IEEE n Operation on IEEE Latency November 2008 Slide 23Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission Scenario 3: IEEE n on Channel 4, 20 MHz wide November 2008 Mukul Goyal, U Wisconsin MilwaukeeSlide 24

doc.: IEEE /30r2 Submission Scenario 3: Changes in IEEE n Traffic Load During an Experiment November 2008 Mukul Goyal, U Wisconsin MilwaukeeSlide 25 Packet Payload: 1470B

doc.: IEEE /30r2 Submission Scenario 3: Impact of IEEE n Operation on IEEE Loss Rate November 2008 Slide 26Mukul Goyal, U Wisconsin Milwaukee

doc.: IEEE /30r2 Submission Scenario 3: Impact of IEEE n Operation on IEEE Latency November 2008 Slide 27Mukul Goyal, U Wisconsin Milwaukee