Coexistence Capacity Allocation Methods March 2008 doc.: IEEE 802.22-08/0xxxr0 March 2008 IEEE P802.22 Wireless RANs Date: 2008-03-05 Coexistence Capacity Allocation Methods 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. > Gerald Chouinard, CRC Gerald Chouinard

Coexistence Capacity Allocation Methods March 2008 doc.: IEEE 802.22-08/0xxxr0 March 2008 Coexistence Capacity Allocation Methods 802.22 WRAN standard needs to allow for coexistence of overlapping co-channel cells with proper capacity sharing (avoid system failure caused by interference) Coexistence algorithms have been proposed at the MAC layer but the PHY layer has not been fully developed to operate in such burst collision environment Two methods are investigated to share the channel capacity among overlapping co-channel cells: inter-frame capacity allocation: frame-by-frame basis intra-frame capacity allocation: using different parts of the same frame Gerald Chouinard, CRC Gerald Chouinard

RF environment resulting from overlapping co-channel WRAN cells March 2008 doc.: IEEE 802.22-08/0xxxr0 March 2008 RF environment resulting from overlapping co-channel WRAN cells Adjacent non-interfering cell 52 km 31 km Gerald Chouinard, CRC Gerald Chouinard

RF environment resulting from overlapping co-channel WRAN cells March 2008 doc.: IEEE 802.22-08/0xxxr0 March 2008 RF environment resulting from overlapping co-channel WRAN cells Grey area is where normal demodulation (QPSK, rate: 1/2) is not possible Overlapping cell with worst case of negative signal differential 31 km 31 km Gerald Chouinard, CRC Gerald Chouinard

Inter-frame capacity allocation March 2008 doc.: IEEE 802.22-08/0xxxr0 March 2008 Inter-frame capacity allocation TDM of transmission frames Collision during superframe preamble and SCH Preamble: do orthogonal PN-sequences need to be used? SCH: needs more robust modulation than QPSK, rate: 1/2 Need to minimize the size of the SCH payload because of the large overhead in the ruggedized version This SCH payload needs to be the same for all BSs in the same area: CPE will decode the strongest SCH to carry information on allocation of the 16 frames to the various BSs, and to the inter-frame quiet periods SCH MAC section will need to be reviewed Gerald Chouinard, CRC Gerald Chouinard

Inter-frame capacity allocation (Cont’d) March 2008 doc.: IEEE 802.22-08/0xxxr0 March 2008 Inter-frame capacity allocation (Cont’d) Frequency synchronization could be acquired from the superframe but not the timing synchronization due to propagation delays Timing information will be acquired by CPE from the header of the frame allocated to the associated BS Minimum pace for frame tranmission: To keep time sync at the CPE: minimum one per superframe To provide QoS: every two frames but not practical => compromise on QoS when coexistence If yes, the MAC coexistence algorithms will end up assigning the 16 frames in a superframe to the local BSs according to their capacity loading Gerald Chouinard, CRC Gerald Chouinard

Inter-frame capacity allocation (Cont’d) March 2008 doc.: IEEE 802.22-08/0xxxr0 March 2008 Inter-frame capacity allocation (Cont’d) Special AGC requirements at BS receiver to deal with widely varying frame amplitude AGC to keep track of wanted upstream subframe amplitude AGC to block interfering frames Special AGC requirements at CPE receiver to deal with widely varying frame amplitude AGC to keep track of superframe header amplitude AGC to keep track of wanted downstream subframe amplitude Should the 802.22 standard allow for two modes of operation? Normal mode to keep overhead to minimum Rugged mode in case of co-channel overlapping cells How and when would the switch take place? Gerald Chouinard, CRC Gerald Chouinard

Intra-frame capacity allocation March 2008 doc.: IEEE 802.22-08/0xxxr0 March 2008 Intra-frame capacity allocation Share the capacity among co-channel overlapping WRAN cells by allocating parts of a frame This would more easily preserve the QoS requirement Both superframe and frame headers will need to be decoded under collision environment More rugged headers will result in much more overhead (the frame header carries much more information: FCH, DS/US-MAPs, DCD, UCD, etc.) TDM of portions of frames Can be accommodated in downstream because of vertical mapping More difficult to accommodate in upstream because of horizontal mapping: use of 7-symbols columns will require symbol buffers to absorb the propagation time differences among the BSs and CPEs Gerald Chouinard, CRC Gerald Chouinard

Intra-frame capacity allocation (Cont’d) March 2008 Intra-frame capacity allocation (Cont’d) Time buffers Gerald Chouinard, CRC

Intra-frame capacity allocation (Cont’d) March 2008 doc.: IEEE 802.22-08/0xxxr0 March 2008 Intra-frame capacity allocation (Cont’d) Downstream/upstream apportionnement will need to be common to all overlapping cells If TTG is not common, downstream and upstream bursts will collide, the advantage of TDD is no longer available Special AGC requirements at CPE receiver to deal with widely varying parts of the downstream bursts AGC to keep track of superframe and frame header amplitude AGC to keep track of wanted portion of the downstream bursts AGC to block interfering portions of the downstream bursts Special AGC requirements at BS receiver to deal with widely varying parts of the upstream bursts AGC to keep track of wanted portion of the upstream bursts AGC to block interfering portions of the uptream bursts Gerald Chouinard, CRC Gerald Chouinard

March 2008 Conclusion Inter-frame capacity allocation seems to be the only reasonable alternative for accommodating coexistence at the PHY layer Need to review the SCH MAC section to re-define and minimize the payload requirement Need to re-define the modulation and coding of the superframe header (preamble and FCH) Need to determine minimum CPE time re-sync refresh rate for minimum frame allocation to BSs (one per superframe?) Need to define MAC coexistence algorithms according to what can be done by the PHY Need to define two modes of operation? (normal and coexistence operation) Gerald Chouinard, CRC