doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 1 Overlapping BSS Co-Existence Date: Authors:

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 2 Abstract The presentation describes enhancements for overlapping BSS co-existence –The presentation provides guidance how to detect the OBSS and the overlapping channels –The presentation describes rules and related methods for transmissions in overlapping channels

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 3 Problem Statement The ac will increase number of cases in which the primary and the non-primary channels overlap Currently ac has inadequate rules and means to protect a primary channel over a non-primary channel

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 4 Targets of the Channels Protection The legacy a/n with 20 MHz have NAV protection present in all TXOPs –Protection level of ac should be at similar level or better even with capacity enhancements The protection mechanism should be scalable –The protection overhead should be minimized –The maximum protection level is not needed in every scenario –Scalability is w.r.t, the number of the operating channels and the number of OBSSs

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 5 Detecting OBSS Each device calculates backoff and receives transmissions in its primary channel The AP receives a ac PLCP header with unallocated Group ID or Nsts values The STA receives a ac PLCP header but cannot decode a frame The STA receives a frame with a foreign BSSID Through scanning: –Scanning enables STA to detect BSSs that overlap only at non- primary channel(s) –AP may scan or command associated STA(s) to scan OBSS Background Information

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 6 OBSSs Examples Single ac BSS in 80 MHz mode has the following possibilities to overlap: –The primary channels of the BSSs are at the same channel The NAV information is shared between BSSs –The other BSS transmits at the non-primary channels Legacy a/n BSS may transmit only in non-primary channels Non-congested ac BSS may transmit only in subset, i.e. primary and secondary, channels –The other ac BSS transmitting at the same operating channels –The other ac BSS operating in 160 MHz mode 160 MHz BSS may have its primary channel at separate 80 MHz channel Background Information

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 7 Primary Channel Selection Rules The local BSS or OBSS may change its primary channel –The operating channels of the BSS are derived from the primary channel AP may change the BSS primary channel to the same primary channel as OBSS and thus NAVs are visible to each other AP should select the BSS primary channel to avoid overlapping operating channels Background Information

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 8 Problem Statement The ac will increase the number of cases in which the primary and the non-primary channels overlap Currently ac has inadequate rules and means to protect a primary channel over a non-primary channel –The enhanced RTS CTS scheme only considers CCA of the transmitter and recipient: NAV protection of other BSS transmissions at non-primary channels cannot be received

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 9 Challenge: Protecting Primary Channel over a Non-primary Channel The operating channels of the BSSs may partially overlap –The primary channel of the 160 MHz mode BSS may be outside the 80 MHz operating channel of other BSS –The NAV information is received if transmitted in primary channel The BSS should have means to protect its transmissions at primary channel –The 160 MHz mode BSSs should have means to share non- primary 80 MHz channels

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 10 Improved Co-existence: NAV to Protect Primary Channel TXOP holder commands a selected STA to send a frame(TBD) to other BSS’s primary channel –The primary channel of other BSS doesn’t overlap with channels reserved by TXOP holder –The frame sets NAV for the channels reserved by TXOP holder Justification: –Enables BSS to protect its primary channel over secondary channels –Avoids hidden terminal problems –Improves the efficiency of the non- primary channels sharing

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 11 Example Protecting Primary Channel The BSS2 operates in 80MHz mode and BSS1 operates in 160 MHz mode A TXOP holder in BSS2 commands a STA to send a frame to primary channel of BSS1 to protect the ongoing transmission and indicate presence of its primary channel –The recipients shall not use the channels for the duration as indicated in the frame

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 12 Example Sharing Non-Primary Channels Two BSSs are operating in a non- contiguous 160 MHz transmission mode The TXOP holder commands with a frame the reserving STA to send a frame to primary channel of BSS2 –The recipients shall not use the channels for the duration as indicated in the frame

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 13 Challenge: Increasing TXOP Bandwidth The TXOP holder may test availability of the non- primary channels for a PIFS duration –If energy level of the channels is below the CCA threshold, the TXOP holder may transmit at the channels –In theory this is similar to allowing a STA to issue active scanning after a PIFS The operation is prone to hidden terminal problems –the TXOP holder has no knowledge of the virtual carrier sensing at the non-primary channels

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 14 Improved Co-Existence: Virtual Carrier Sensing by Reserving STA Reserving STA reserves more non-primary channels –The TXOP holder specifies the reserving STA, the channels to be reserved and the time of reporting –The reserving STA follows the orders of the TXOP holder The reserving STA temporarily contends at the channels it is reserving –The reserving STA synchronizes to the channel to be reserved The reserving STA transmits a frame to reserve the channel At the reporting time, the reserving STA signals success to TXOP holder

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 15 Example Increasing TXOP Bandwidth The TXOP holder commands with a frame the reserving STA to reserve the secondary channel –The reserving STA is capable to reserve the secondary channel and indicates the success at the time reporting time, specified by the TXOP holder Similar operation is repeated for tertiary and quaternary channels

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 16 Summary The problems are: –Blind entry to the channel –Primary channel transmissions colliding with blind secondary channel transmissions This presentation provides the solutions to the problems: –Synchronization with the channel to be reserved –Protecting and prioritizing primary channel transmissions over secondary channel transmissions

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 17 Strawpoll Do you agree with the targets of channels protection as listed below? –The legacy a/b/g/n with 20 MHz have NAV protection present in all TXOPs Protection level of ac should be at similar level or better even with capacity enhancements –The protection mechanism should be scalable The protection overhead should be minimized The maximum protection level is not needed in every scenario Scalability is w.r.t, the number of the operating channels and the number of OBSSs? Yes No

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 18 Strawpoll Are you in favor of having NAV protection available for channels reserved by TXOP holder, when the primary channel of other BSS doesn’t overlap? Yes No

doc.: IEEE /1303r5 Submission November 2010 Jarkko Kneckt (Nokia)Slide 19 Strawpoll Are you in favor of using reserving STA to enable better co-existence? Yes No