40MHz in 2.4 GHz band Date: 2006-27-06 Authors: Name Company Address Month Year doc.: IEEE 802.11-yy/0XXXr0 June 2006 40MHz in 2.4 GHz band Date: 2006-27-06 Authors: Name Company Address Phone email Assaf Kasher Intel assaf.kasher@intel.com Eldad Perahia eldad.perahiah@intel.com Adrian Stephens adrian.p.stephens@intel.com Gal Basson gal.basson@intel.com Solomon Trainin solomon.trainin@intel.com 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 <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, 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 <stuart.kerry@philips.com> 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 <patcom@ieee.org>. Assaf Kasher et al. (Intel) Assaf Kasher (Intel)

Addresses Comments with CIDs Month Year doc.: IEEE 802.11-yy/0XXXr0 June 2006 Addresses Comments with CIDs 104, 258, 286, 288, 430, 431, 689, 705, 706, , 1493, 1558, 1560, 1561, 1728, 2848, 3471, 3501, 3502, 3602, 4570, 4571, 7010, 7193, 7195, 7312, 7313, 7314, 7315, 7871, 7925, 8138, 8186, 8194, 8282, 10272 Assaf Kasher et al. (Intel) Assaf Kasher (Intel)

There are many problems with 40MHz channel spacing in 2.4GHz: Month Year doc.: IEEE 802.11-yy/0XXXr0 June 2006 40MHz operation in 2.4GHz There are many problems with 40MHz channel spacing in 2.4GHz: Channel availability Coexistence mechanisms between legacy 11g/b on the extension channel and the 40MHz BSS are problematic. 40MHz devices are bad neighbors to devices operating in adjacent channels. Assaf Kasher et al. (Intel) Assaf Kasher (Intel)

Channel Availability The 2.4GHz band is only 70MHz wide Month Year doc.: IEEE 802.11-yy/0XXXr0 June 2006 Channel Availability The 2.4GHz band is only 70MHz wide 2402MHz-2472MHz (Practical OFDM use in US) A single 40MHz channel leaves space for only one more 20MHz channel. Best case – only when channel planning is available. Out of the box configurations may not allow even for this There are no other frequencies a BSS can move to if it hits interference. 5MHz channel spacing – Any channel can be the center of a 20MHz or 40MHz channel - Default AP settings are 1,11,6,3,5 in most 11g AP vendors. 2.4GHz spectrum is congested with Over 100 Million WLAN plus countless Bluetooth devices, cordless phones, baby monitors, microwave ovens, etc. Assaf Kasher et al. (Intel) Assaf Kasher (Intel)

Coexistence with Overlapping BSS in the extension channel. Month Year doc.: IEEE 802.11-yy/0XXXr0 June 2006 Coexistence with Overlapping BSS in the extension channel. No practical way to respect the NAV on the extension channel. Ideally 40MHz devices would maintain two NAVs, one per 20MHz channel, based upon CCA and RTS/CTS etc packets on the control and extension channels It is not possible to receive packets on the extension channel when transmitting on the control channel, so this ideal can never be achieved. The overlapping BSS can be either 10Mnz, 15MHz, 20MHz or 25MHz apart but we can set the extension channel to be 20MHz/25MHz apart. 20/25 MHz does not cover all the deployed cases (channels 3, 5) What will be the algorithm for deciding 20 or 25 or 10 Need for supporting both OFDM and CCK protection mechanism CCK protection may make the 40MHz channel use very inefficient. RTS/CTS exchange in rate 1Mbps is 618usec long. Assaf Kasher et al. (Intel) Assaf Kasher (Intel)

40Mhz devices are very bad neighbors Month Year doc.: IEEE 802.11-yy/0XXXr0 June 2006 40Mhz devices are very bad neighbors News magazines articles on 40MHz devices show that a 40MHz devices (from various vendors) cause significant degradation in the throughput of Adjacent 11g devices The throughput of the legacy devices may fall in some cases to zero. Similar results with various vendors. Assaf Kasher et al. (Intel) Assaf Kasher (Intel)

Possible Solutions Disallow 40MHz operation in 2.4GHz Month Year doc.: IEEE 802.11-yy/0XXXr0 June 2006 Possible Solutions Disallow 40MHz operation in 2.4GHz There isn’t really enough bandwidth in 2.4GHz to allow this type of operations (Only 70 MHz). Crowded spectrum 5MHz channel spacing The wider spectral mask of 40MHz devices cause higher interference for BSS in an adjacent channel 5GHz has plenty of BW to incorporate 40 MHz (in some regulatory domains: ~0.5GHz). Assaf Kasher et al. (Intel) Assaf Kasher (Intel)

Possible Solutions (Cont.) Month Year doc.: IEEE 802.11-yy/0XXXr0 June 2006 Possible Solutions (Cont.) Allow 40MHz operations in 2.4GHz only when there is no substantial load in or near the extension channel. Otherwise: mandate BSS transition to 20 MHz “In” the extension channel means devices 20MHz off the control channel “Near” the extension channel means devices 20/25/30MHz off the control channel A 40MHz STA/AP shall switch to 20MHz operation When the signal in the extension channel passes the detection threshold for 20% duty cycle (time) for 10 seconds. CCA threshold for detection in the extension channel – 72dBm Switch to 20MHz in 10 seconds. Assaf Kasher et al. (Intel) Assaf Kasher (Intel)

Possible Solutions (cont.) Month Year doc.: IEEE 802.11-yy/0XXXr0 June 2006 Possible Solutions (cont.) Distributed Approach A non-AP STA looks for extension channel interference. If it passes the thresholds above, it shall stop transmitting in 40MHz and requests the AP to stop transmitting to it using 40MHz. If the AP senses transmission in the extension channel as above, it switches the whole BSS to 20MHz. Assaf Kasher et al. (Intel) Assaf Kasher (Intel)

Month Year doc.: IEEE 802.11-yy/0XXXr0 June 2006 Switching Back to 40MHz An AP/STA can switch back to 40MHz 300 seconds after it has switched to 20MHz. Assaf Kasher et al. (Intel) Assaf Kasher (Intel)