1. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 1 Performance evaluation of 40MHz transmission - regarding CCA on extension channel - Notice: This document has been prepared to assist IEEE 802.11. 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. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at.http:// ieee802.org/guides/bylaws/sb-bylaws.pdfstuart.kerry@philips.compatcom@ieee.org Date: 2006-04-19 Authors:

2. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 2 Abstract Simulation results are provided to compare the performance between with and without CCA on the extension channel when transmitting 40 MHz frames.

3. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 3 Contents 40MHz transmission with CCA on the extension channel 40MHz transmission without CCA on the extension channel Simulation –Simulation parameters –Network topology –Throughput performances (1 STA in ch_b) –Throughput performances (2 STAs in ch_b) Summary

4. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 4 40 MHz transmission with CCA on extension channel ch_a (control) t ch_b (extension) t CS Carrier Sense (CS) 20MHz frame CS 20MHz frame 40MHz AP in BSS : Failure 20MHz AP in OBSS : Success Always 40MHz Analogue of AP in BSS AP in BSS fails to receive 20MHz frame in ch_a when ch_b is also BUSY. 20MHz frame 40MHz frame CS 40MHz STA in BSS : wait for both channels to be IDLE. 40MHz STA senses both ch_a & ch_b before transmitting 40MHz frame.

5. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 5 40 MHz transmission without CCA on extension channel ch_a (control) t ch_b (extension) t CS Carrier Sense (CS) 20MHz frame CS 20MHz frame 40MHz AP in BSS : Failure 20MHz AP in OBSS : Success Always 40MHz Analogue of AP in BSS AP in BSS fails to receive 20MHz frame in ch_a when ch_b is also BUSY. 20MHz frame 40MHz frame CS 40MHz STA in BSS : transmits 40MHz frame if ch_a is IDLE. 40MHz STA senses only ch_a before transmitting 40MHz frame. 40MHz AP in BSS : Failure 20MHz AP in OBSS : Failure

6. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 6 Simulation Parameters Beacon interval100 TU Number of aggregated frames16 MPDU size1500 bytes Tx rate in 40 MHz283 Mbps Tx rate in 20 MHz54 Mbps Delay bound of each frameinfinity CWmin15 AIFSSIFS + 3*slottime Maximum retry count4 Number of 40 MHz HT nodes2 (including 1 AP) Number of 20 MHz legacy nodes in the target BSS2 Number of 20 MHz legacy nodes in the ext. ch. 2 or 3 (including 1 AP) Offered load on 40 MHz HT STA for 40 MHz traffic100 Mbps Offered load on 20 MHz legacy STA in the cont. ch.20 Mbps Offered load on 20 MHz legacy STA in the ext. ch.varied Distance between target BSS and OBSS (in ext. ch.)5 m

7. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 7 Network Topology Target BSS in the control channel OBSS in the extension channel 40MHz AP (0, 0) 5 m Legacy STA (0, -0.5) 1 m 40MHz HT STA in target BSS 20MHz Legacy STA in target BSS 20MHz Legacy STA in OBSS Legacy AP Legacy STA (0, 0.5) 0.5 m 40MHz STA (-0.5, 0)

8. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 8 40 MHz throughput (1 STA in ch_b) Collision between frames in ext. ch. degrades the performance 10 Mbps

9. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 9 20 MHz in ch_a throughput (1 STA in ch_b) 0.5 Mbps Retransmission of 40 MHz frames due to collision between 20 MHz frames in ext. ch. takes the opportunity of 20 MHz Tx in ctrl. ch. Backoff due to collision between 40 MHz frames and 20 MHz frames in ext. ch. gives slight opportunity to 20 MHz Tx in ctrl. ch. WHEN THERE ARE ONLY 1 STA IN EXT. CH.

10. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 10 20 MHz in ch_b throughput (1 STA in ch_b) No CCA on ext. ch. gives large impact to ext. ch. 20 MHz OBSS 8 Mbps

11. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 11 40 MHz throughput (2 STAs in ch_b) Degradation in each case becomes larger but still some gain for the case doing CCA on ext. ch. 10 Mbps This gain is kept even when the number or STAs in ext. ch. increases

12. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 12 20 MHz in ch_a throughput (2 STAs in ch_b) No opportunity for 20 MHz Tx when there are 2 STAs in ext. ch. even for the case w/o CCA Retransmission of 40 MHz frames due to collision between 20 MHz frames in ext. ch. takes the opportunity of 20 MHz Tx in ctrl. ch.

13. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 13 20 MHz in ch_b throughput (2 STAs in ch_b) No CCA on ext. ch. gives large impact to ext. ch. 20 MHz OBSS 4 Mbps

14. doc.: IEEE 802.11-06/0569r0 Submission April 2006 Tomoko Adachi, Toshiba CorporationSlide 14 Summary No CCA on the extension channel causes degradation to all three kinds of throughput. –As 40 MHz frames in the target BSS collides with 20 MHz frames in OBSS  40 MHz throughput and 20 MHz throughput in extension channel degrade. –As 40 MHz frames are retransmitted more and opportunity to transmit 20 MHz frames in control channel becomes few  20 MHz throughput in control channel degrades. Under large traffic in extension channel, –Gain of avoiding collisions still remains in 40 MHz throughput –Impact of not doing CCA on the extension channel is large to ext. ch. 20 MHz OBSS