Interference-free scheduling Month Year doc.: IEEE 802.22-yy/xxxxr0 February 2008 Interference-free scheduling IEEE P802.22 Wireless RANs Date: 2008-02-13 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 Chair Carl 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. > Dave Cavalcanti, Philips John Doe, Some Company

Month Year doc.: IEEE 802.22-yy/xxxxr0 February 2008 Abstract This presentation gives an overview of the Interference-free scheduling mechanism for WRANs self-coexistence. Dave Cavalcanti, Philips John Doe, Some Company

Self-Coexistence The general problem: Month Year doc.: IEEE 802.22-yy/xxxxr0 February 2008 Self-Coexistence The general problem: Depending on the channel availability, WRANs may have to share the same TV channel How to avoid interference (collisions) in overlapping areas by adjusting the bandwidth allocation schedule? TDMA Schedule Dave Cavalcanti, Philips John Doe, Some Company

Interference-free Scheduling Month Year doc.: IEEE 802.22-yy/xxxxr0 February 2008 Interference-free Scheduling Goal: Use information from neighboring cells to detect potential interference situations and adapt the bandwidth allocation schedule to solve the problems in the coexistence areas. Interference-free scheduling is enabled by the CBP protocol executed by CPEs, under BS control CPEs transmit/receive CBP packets during SCW (Self-Coexistence Window) BS schedules CBP transmissions/receptions Dave Cavalcanti, Philips John Doe, Some Company

Month Year doc.: IEEE 802.22-yy/xxxxr0 February 2008 How it works? CPE collects information from potential interferers in the area, e.g., CBP packets from other WRANs CBP packets carry information About the cell (DS/US Boundary IE: information about contiguous blocks of DS or US allocations scheduled by the BS) About a CPE’s reservations with its BS (Beacon IE: information about a particular CPE) The CPE can use this information as follows: The CPE reports the information to its BS, if requested (allowed) by the BS (the BS controls all the measurement requests/reports) The CPE may also include constraint elements when requesting upstream bandwidth For example, a CPE can specify: “Give me 100Kb of airtime, but not between T1 and T2” The BS may explicitly ask the CPE for any constraints it might have regarding allocation (TRC-REQ message) BS adapts its bandwidth allocation schedule if needed to avoid interference Dave Cavalcanti, Philips John Doe, Some Company

Month Year doc.: IEEE 802.22-yy/xxxxr0 February 2008 Example BS A is operational and CPE A1 transmits CBP packets BS B and CPE B1 starts operating and B1 receives CBP packets from A1 CPEs A1 and B1 reports to their BSs, this enables: Network discovery Spectrum etiquette If no other channel is available, the BSs can use interference-free scheduling (BS B changes its schedule to CPE B1 to avoid interfering with CPE A1) If interference-free scheduling is not effective (e.g. not enough resources) BSs may go the next self-coexistence step: resource sharing (renting/offering, spectrum contention) CPE B1 CPE A1 BS A BS B CPEs in the overlapping area would suffer from interference if no co-existence mechanism is in place. Dave Cavalcanti, Philips John Doe, Some Company

Practical considerations for Interference-free scheduling Month Year doc.: IEEE 802.22-yy/xxxxr0 February 2008 Practical considerations for Interference-free scheduling Downstream/upstream bandwidth allocations made by a BS to CPEs in coexistence areas should not change for a certain period of time The BS should try to use the same allocation (time and frequency) for a CPE in the overlapping area This guarantees that the information carried in CBP packets is valid for at least a minimum duration, thus allowing enough time to the recipients of the CBP packets to implement self-interference mitigation mechanism The BS should try to maintain a stable bandwidth allocation schedule, at least for those CPEs in the overlapping area Trade-off: the more dynamic the allocations, the higher the overhead (more inter-cell communication) to implement interference mitigation mechanisms Dave Cavalcanti, Philips John Doe, Some Company

Month Year doc.: IEEE 802.22-yy/xxxxr0 February 2008 Conclusions Interference-free scheduling allows the BSs to avoid interference by adapting the bandwidth allocations Especially useful to mitigate localized interference for CPEs in overlapping areas No additional complexity, since required information can be included in CBP packets and other existing management messages (e.g. BW request, measurement reports) Actual scheduling algorithm used is implementation dependent, but for the WRANs shall support Discovery of neighboring WRANs through transmissions/receptions of CBP packets This enables the detection of potential interference situations in overlapping areas Dave Cavalcanti, Philips John Doe, Some Company

References 802.22 Working Document draft 0.4.7 Month Year doc.: IEEE 802.22-yy/xxxxr0 February 2008 References 802.22 Working Document draft 0.4.7 Overview of CBP (doc 136r0, March 2007) Dave Cavalcanti, Philips John Doe, Some Company