1. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 1 Preferred Channel and DFS 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 Authors : NameCompanyAddressPhoneemail Joe KwakInterDigitalBolingbrook, IL630-739-4159joekwak@sbcglobal.net Jari JokelaNokiaVisiokatu 1, 33720 Tampere, Finland +358 50 486 0445 Jari.jokela@nokia.com Roger Durand RIM rdurand@rim.com

2. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 2 OUTLINE Introduction DFS Regulations ETSI’s Compliant DFS Specification Preferred Channel Specification Comparison of Compliant vs Preferred Channel specifications wrt regulations Uniform Spreading requirement details Conclusions

3. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 3 Introduction Use of Preferred Channel for STAs searching for APs for association saves 80% of battery power. NOV06 (06/956r2) meeting held straw poll for support of Preferred Channel with an AP control instead of distributed control showing 92% support. JAN06 (07/120r0) meeting presented Preferred Channel with AP control. Vote to incorporate normative text showed only 45% support due to concerns about DFS compliance. This presentation shows modified Preferred Channel normative text wording aligned with DFS-compliant wording from ETSI specification. This new wording satisfies DFS requirements and regulations.

4. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 4 European DFS Regulations ”Every WAS/RLAN, when operating in the frequency ranges 5 250–5 350 MHz and 5 470–5 725 MHz, shall employ a DFS mechanism with a Radar Interference Detection function to detect radar signals which have a level above the interference detection threshold as defined in Recommendation ITU-R M.1652. With regard to DFS, a WAS/RLAN device shall operate in either Master or Slave Mode. WAS/RLAN devices operating in Slave Mode (Slave Device) can only operate in a network controlled by a WAS/RLAN device operating in Master Mode (Master Device). Every Master Device will use the Radar Interference Detection function in order to check for any co-channel radar signal prior to use a channel but also during normal operation. In addition to this Radar Interference Detection function, every Master Device shall also implement a channel selection mechanism to ensure a near uniform spread of the loading of available spectrum. The Slave Devices shall not transmit before having received an appropriate enabling signal from a Master Device. Slave Devices with a power level of 200 mW e.i.r.p. or above shall have their own Radar Interference Detection function.” Verbatim from Decision ECC/DEC/(04)08, 12NOV04, Equiv to FCC ruling. DFS Regulation Uniform Spreading Requlation

5. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 5 DFS Master Requirements ( EN 301 893 ) “a) The master device shall use a Radar Interference Detection function in order to detect radar signals. b) Before initiating a network on a channel, which has not been identified as an Available Channel, the master device shall perform a Channel Availability Check to ensure that there is no radar operating on the channel. c) During normal operation, the master device shall monitor the Operating Channel (In-Service Monitoring) to ensure that there is no radar operating on the channel. d) If the master device has detected a radar signal during In-Service Monitoring, the Operating Channel is made unavailable. The master device shall instruct all its associated slave devices to stop transmitting on this (to become unavailable) channel. e) The master device shall not resume any transmissions on this Unavailable Channel during a period of time after a radar signal was detected. This period is referred as the Non-Occupancy Period.”

6. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 6 DFS Slave Requirements ( EN 301 893 ) “a) A slave device shall not transmit before receiving an appropriate enabling signal from a master device. b) A slave device shall stop all its transmissions whenever instructed by a master device to which it is associated. The device shall not resume any transmissions until it has again received an appropriate enabling signal from a master device. c) A slave device which is required to perform radar detection (see table D.3), shall stop its own transmissions if it has detected a radar”

7. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 7 Uniform Spreading Requirements (EN 301 893) “Definition: The Uniform Spreading is a mechanism to be used by the RLAN to provide, on aggregate, a uniform loading of the spectrum across all devices. This requires that a RLAN device shall select a channel out of the list of usable channels so that the probability of selecting a given channel shall be the same for all channels. The probability of selecting each of the usable channels shall be within 10 % of the theoretical probability. For n channels, the theoretical probability is 1/n.”

8. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 8 ETSI’s Compliant Requirements Summary 1.Master/Slave enabling of transmissions 2.Radar detection for channel availability check 3.Continuous radar detection to monitor operating channel 4.Uniform Spreading for channel selection 5.Shutdown if radar detected (=channel switch). Items in RED apply to Preferred Channel, last requirement already satisfied by TGh Channel Switch.

9. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 9 1. Master/Slave Enabling  Preferred Channel is designed for AP to control STA transmissions by set/reset of NetworkAdviceEnabled bit.  No STA shall transmit on Preferred Channel unless so enabled by AP which sets NetworkAdviceEnabled bit.  This is eqivalent to ETSI requirement sufficient for regulatory purposes.

10. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 10 2. Radar Detection for Channel Availability Explicit requirement in new normative text: “If dot11SpectrumManagementRequired is true,..the AP shall periodically monitor the Preferred Channel for frame transmissions. If no beacons and no network advice frames are detected on the Preferred Channel, the AP should perform a channel availability check on the Preferred Channel to ensure that there is no radar operating on the channel.” “Should” is used because the AP may not have the resources to detect radar on 2 channels. Preferred Channel uses same wording as ETSI.

11. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 11 3. Radar Detection for Monitoring Preferred Channel Explicit requirement in new normative text: “If an AP has set dot11NetworkAdvice- Enabled to true at any STA, the AP shall ensure that a STA shall use radar interference detection to monitor the Preferred Channel for radar per the regulatory requirements.” Preferred Channel uses same wording as ETSI.

12. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 12 4. Uniform Spreading for channel selection required  Regulation requires “channel selection mechanism to ensure a near uniform spread.”  In practice this is accomplished simply by randomly selecting an operating channel.  The Regulation does not specify when the random channel number is selected or how often the channel is to be reselected, nor does it address the source of the required random selection or the restrictions on who may use the selected channel.  The goal is to provide “near uniform spread”.  Random selection is ETSI’s chosen requirement mechanism to satisfy the regulation, others exist.  Preferred Channel is randomly selected and satisfies the spirit and letter of the regulation.

13. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 13 Uniform Spreading trials with Preferred Channel 1 2 3 4 5 678chan 1 2 3 4 5 678 1 2 3 4 5 678 1 2 3 4 5 678 1 2 3 4 5 678 1 2 3 4 5 678 1 2 3 4 5 678 1 2 3 4 5 678 1 2 3 4 5 678 1 2 3 4 5 678 1 BSS +1 BSS Without Preferred Channel With Preferred Channel All channels randomly selected before use. BSS = 40-70% utilization (typ) P.C. = 1- 5% utilization (typ) time

14. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 14 Results from Spreading Trials  Use of Preferred Channel produces spectrum spreads no less uniform (and possibly more uniform) than currently permitted applications.  Worst case for non-uniform spread occurs with a single BSS in the regulatory class.  In this case using the Preferred Channel produces a spread more uniform than conventional operation since usually occupies two channels instead of one.  All operating channels shall defer and shut down for radar. The Preferred Channel does this, but further defers and shuts down for beacons, thus making the Preferred Channel “available” for all users, according to the current terms and definitions.

15. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 15 Conclusions Preferred Channel is shown to save 75-80% power for STAs searching for WLAN services (07/0120r0). New Net Advice transmissions on Preferred Channel provide a pointer to active BSS channel, and so decrease the number of scanned channels. The AP manages all resources for Net Advice transmissions in a master/slave mode. The AP acts as enabling master to control channel transmissions to meet DFS regulations where applicable. Normative text for Preferred Channel is found in 07/0118r2. Use of Preferred Channel satisfies all current DFS regulations.

16. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 16 STRAW POLL Do you support use of Preferred Channel for Power Saving? YES _______ NO _______ ABSTAIN _______

17. doc: IEEE 802.11-07/0468r0March 2007 Submission Joe Kwak, Jokela, Durand 17 Motion Move to include 07/0118r3 into next version of TGv draft Moved:_Kwak_____ Second:__________ YES _______ NO _______ ABSTAIN _______