1. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 1 Spectrum Sensing for WRAN Discovery and Detection IEEE P802.22 Wireless RANs Date: 2007-07-10 Authors: Notice: This document has been prepared to assist IEEE 802.22. 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 802.22. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.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 Chairhttp://standards.ieee.org/guides/bylaws/sb-bylaws.pdf Carl R. StevensonCarl R. Stevenson 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 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at patcom@iee.org.patcom@iee.org

2. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 2 Abstract This presentation gives a outline of the WRAN discovery and detection problem, identifies the issues of the current discovery/detection mechanism, and provides remedies that enable efficient spectrum sensing for WRAN discovery and detection.

3. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 3 Preliminary The operating channel of a WRAN cell can dynamically change over time, due to –Incumbent detected –Unacceptable channel condition, etc. Spectrum sensing for WRAN discovery and detection is important for –Incumbent protection Quiet period coordination across WRAN cells –WRAN self-coexistence Interference mitigation and spectrum sharing

4. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 4 WRAN Dynamic Channel Use

5. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 5 Analogy of the WRAN Discovery/Detection Problem University professors (WRAN cells) occupy offices (TV channels) on a temporary basis. A professor (WRAN cell) needs to check if an office (TV channel) is occupied by someone else (other WRAN cells) before conducting certain activities (transmission, sensing, etc.) in this office (TV channel) or in a nearby office (adjacent TV channel).

6. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 6 Current Mechanism for WRAN Discovery WRAN discovery/detection is performed during the initialization phase and the normal operation phase CBP packet is employed to enable WRAN discovery –However, CBP packets are transmitted in random instances. –An detecting WRAN cell monitors the spectrum and strives to capture the randomly transmitted CBP packets. An operating WRAN cell transmits at least one CBP packet every 4 frames. –However, successful CBP packet transmission is not guaranteed –Re-transmissions are needed in case of packet collisions between uncoordinated cells.

7. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 7 CBP Recap The Coexistence Beaconing Protocol – CBP. The CBP is a best-effort (contention based) protocol based on coexistence beacon transmissions. Coexistence beacons are transmitted during a contention window, the Self Coexistence Window, at the end of an upstream sub-frame. CBP packets can be transmitted by CPEs and BSs.

8. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 8 Issues of the Current Discovery Mechanism Detection Latency –In the draft - WRAN discovery takes no more than 4 super-frames for one channel. –Latency of 16 super-frames is required for discovering channels N+/-2 –However, there is neither a specification nor a demonstration (simulation and analyses) on how such latency is achieved. Packet loss due to collision –Neighboring cells may share the same SCW and transmit on the same channel. –Need coordination among neighboring cells Continuous monitoring disallows regular operation –In the case SCWs across WRAN cells are asynchronous, the detecting WRAN cell will have to monitor the spectrum continuously.

9. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 9 Analogy of the current mechanism A professor (WRAN cell) makes a occupancy announcement (CBP packet) at least once every 4 days (4 frames). A monitoring professor would have to check the office for up to 4 days or more (if the announcement is lost). If the time of announcement is unknown (asynchronous SCWs), the monitoring professor will have to continuously monitor the office, and duration of monitoring could be much longer. Another professor (nearby cell) in the same office (TV channel) could make the announcement at the same time (synchronized SCW in a TV channel), therefore announcements collide and no one can hear the announcement.

10. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 10 Proposed Remedies Channel Hosting - A CBP packet for announcing the existence of a WRAN on a certain channel is transmitted in every super-frame in a fixed time instance, which are well-known (standardized) in IEEE 802.22. Such an announcement CBP packet is transmitted on a non-contention- based (collision-free) basis through coordination among cells on the same channel. IEEE 802.22 systems are able to complete the WRAN discovery/detection process for a sufficiently large set of channels in a reasonably small time scale (one super-frame), and to discover/detect each channel it only takes 1 symbol. Super-frame, thus the Self-coexistence windows, are synchronized across different channels.

11. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 11 Proposed Remedy – Channel Hosting

12. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 12 Analogy of the proposed remedy An occupied office is hosted by one of the occupying professor an office hour which is well-known to everyone. Professors in the same office coordinate so that the occupancy announcement is made without collision during the office hour. Since the office hour of every office is well-known, the occupancy of an office can be check with no more than the duration of the office hour, and a monitoring professor can check for a large set of offices within a reasonably short period of time efficiently.

13. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 13 More on Channel Hosting The well-known position of the Hosting Slot can be determined by Modulo Scheduling, that is, Hosting Slot Number (in every super- frame) == the SCW slot of Frame {Channel-Number mod 16}. Therefore the hosting CBP packets for different channels are transmitted in a collision-free manner. There are a few channels use the same slot instance for channel hosting due to the modulo affect, referred to as concurrent hosting. However, as frequency separation is very large (16x6MHz), concurrent hosting should be feasible between neighbor cells.

14. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 14 More on Channel Hosting / Modulo Scheduling

15. doc.: IEEE 802.22-07/0352r0 Submission July 2007 Wendong Hu, STMicroelectronicsSlide 15 Conclusion Comments?