1. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 1 Impact of Directional Antenna at CPEs on Coexistence Beaconing Protocol IEEE P802.22 Wireless RANs Date: 2007-08-16 Author: 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 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 2 Abstract This presentation identifies the impacts of direction antenna employed at the CPEs on the CBP based inter- cell communications, by describing a number of coexistence scenarios where CBP is used. Issues such as Communication failure, “Hidden node” problem, SCW backoff slot size requirement (collision detection range) are discussed. Remedies are suggested as the conclusion.

3. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 3 Directional Antenna at the CPE

4. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 4 Neighbor-cell CPE Neighbor-cell CPE: a CPE that is associated with a neighboring cell and located in the self-coexistence region (the overlapping region of multiple neighboring cells) For example, CPE1 and CPE2 are neighbor-cell of each other

5. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 5 Self-coexistence Scenarios (1) Face-to-face neighbor-cell CPEs

6. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 6 Self-coexistence Scenarios (2) Non face-to-face neighbor-cell CPEs

7. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 7 Self-coexistence Scenarios (3) No neighbor-cell CPE

8. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 8 Self-coexistence Scenarios (4) Hybrid - A mixture of the face-to-face CPE and the non-face-to-face CPE cases

9. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 9 When neighbor-cell CPEs are face-to-face Beacons can be transmitted and received by the face- to-face neighbor-cell CPEs This is ONLY case where CBP packets transmitted by CPEs can be received by a neighboring cell.

10. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 10 When neighbor-cell CPEs are non face-to- face CBP packets transmitted by a CPE can not be received by any neighbor-cell CPE However, CBP packets transmitted by the Base-stations can be received by neighbor-cell CPEs and then conveyed to the target BSs This requires that the receiver equips with an omni-direction antenna (e.g. the sensing receiver) and shall be capable of decoding the CBP packets – still an open question.

11. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 11 CBP Communications Fail without a Neighbor-cell CPE (1) Beacons from WRAN2 will never be received (therefore never be discovered) by WRAN1. Without knowing the existence of WRAN2, WRAN1 will interfere WRAN2’s operation (if channel is not symmetrical) and sensing, when, for example, operating co- channel with WRAN2. WRAN2 may decide to switch channel, which however may not be always possible.

12. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 12 CBP Communications Fail without a Neighbor-cell CPE (2) WRAN1, WRAN2, and WRAN3 will not be able to synchronized for their quiet periods. Such situation becomes serious when the WRANs are on co- channel and/or on the 1 st adjacent channels.

13. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 13 CSMA-based CBP doesn’t work well with the directional antenna CSMA needs omni-directional antenna for both transmission and reception, otherwise the neighbor nodes can not detect one another (the hidden node problem). CSMA/CA couldn’t help as the size of the CBP packet is too large compared to the contention window (SCW) – RTSs could likely collide as well.

14. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 14 BS-transmitted CBP requires large slot time for carrier sensing and collision detection For a BS-to-BS distance of 50km, one symbol duration is required for carrier sensing and collision detection.

15. doc.: IEEE 802.22-07/0403r0 Submission August 2007 Wendong Hu, STMicroelectronicsSlide 15 Proposed Remedies The CPE in the cell-overlapping area should employ an Omni- directional antenna or multiple directional antennas for CBP transmission. Use one symbol duration as the backoff slot size for CSMA/CD.