1. doc.: IEEE 802.22-06/0121r1 Submission July 2006 Baowei Ji, SamsungSlide 1 Channel Sensing Based on Self-Signal Suppression (SSS) IEEE P802.22 Wireless RANs Date: 2006-07-19 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 802.22-06/0121r1 Submission July 2006 Baowei Ji, SamsungSlide 2 Abstract A novel channel sensing scheme is proposed based on self- signal suppression/cancellation, which allows in-band channel sensing without the requirements for quiet periods. The optimized tradeoff could be achieved between spectral utilization and the reliability of in-band channel sensing by combining SSS-based channel sensing with on-demand scheduling of quiet periods or dynamic channel hopping.

3. doc.: IEEE 802.22-06/0121r1 Submission July 2006 Baowei Ji, SamsungSlide 3 Motivation Traditional thinking on inband channel sensing: Requirement for quiet period. –Periodically/opportunistically scheduling quiet periods –Dynamic frequency hopping. The proposal is based on self-signal suppression (SSS): –Detect the self signal –Cancel the self signal –Sense over the remaining signal No requirement for quiet period during regular operation (ideally). Almost any sensing algorithm can be applied after self signal suppression.

4. doc.: IEEE 802.22-06/0121r1 Submission July 2006 Baowei Ji, SamsungSlide 4 Illustration of SSS Wireless Channel Channel Estimation Self-Signal Detection Self-Signal Reconstruction Channel Sensing over the Remaining Signal Received Signals

5. doc.: IEEE 802.22-06/0121r1 Submission July 2006 Baowei Ji, SamsungSlide 5 IU Protection P1P1 P2P2 Self Signal P1P1 Remaining Signal Self Signal No Interference SignalInterference Signal Emergence P3P3 IU Signal P2P2 Before SSSAfter SSSBefore SSSAfter SSS P3P3 Suppression Residual Signal Noise Floor Zero Noise

6. doc.: IEEE 802.22-06/0121r1 Submission July 2006 Baowei Ji, SamsungSlide 6 Operation Signal Received Self-Signal Detected Data Integrity Check Passed? Self-Signal Reconstruction Self-Signal Suppression Channel Sensing over the Remaining Signal Maximum Trials Reached? No Channel Possibly Occupied Yes Channel management Yes Normal retransmission protocols

7. doc.: IEEE 802.22-06/0121r1 Submission July 2006 Baowei Ji, SamsungSlide 7 Feasibility/Complexity for Implementation Only two blocks are unique to SSS. –Self-signal reconstruction –Self-signal cancellation The residual self signal level should be below the Incumbent User signal level (possibly below the noise floor). Self-signal could be removed completely in the baseband if the channel estimation is ideal.

8. doc.: IEEE 802.22-06/0121r1 Submission July 2006 Baowei Ji, SamsungSlide 8 Enhancements: Reliable Channel Estimation Received Data Channel Estimation Based on a Single Frame Accumulation/Averaging Over Multiple Frames To Improve Channel Estimation PreambleDownlink Burst The channel is assumed to be stable over multiple frames FCH, DL-MAP, UL-MAP Uplink Burst Frame

9. doc.: IEEE 802.22-06/0121r1 Submission July 2006 Baowei Ji, SamsungSlide 9 Other Enhancements The BS can do channel sensing over all the UL bursts. A CPE can do channel sensing over other CPE’s DL bursts, besides its owns, because any CPE has the capacity to use the whole channel. However, the CPE won’t require for retransmission of other CPEs’ data if signal detection fails. Both the BS and CPEs can do long-time channel sensing over the remaining signals of multiple frames in order to increase the reliability and accuracy of channel sensing.

10. doc.: IEEE 802.22-06/0121r1 Submission July 2006 Baowei Ji, SamsungSlide 10 Optimal Channel Sensing Scheme SSS-based Channel Sensing (regular operation without any IU or other LE signals) Quiet Time-based Channel Sensing (quiet time scheduling or DFH) (on-demand feature) Channel moving Channel is probably occupied. Channel is clear. Channel is occupied. Having moved to a new channel.

11. doc.: IEEE 802.22-06/0121r1 Submission July 2006 Baowei Ji, SamsungSlide 11 Conclusions This method is in parallel with other in-band channel sensing methods that are based on quiet period or DFH. Advantages of uninterrupted channel estimation. Advantages of uninterrupted self-signal transmission. The potential optimal method: SSS-based, plus on-demand quiet-time scheduling and / or DFH.