Reserving STA Date: 2011-1-18 Authors: January 2011 January 2011 doc.: IEEE 802.11-11/XXXXr0 January 2011 Reserving STA Date: 2011-1-18 Authors: Jarkko Kneckt (Nokia) Jarkko Kneckt (Nokia)

January 2011 doc.: IEEE 802.11-11/XXXXr0 January 2011 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 Jarkko Kneckt (Nokia) Jarkko Kneckt (Nokia)

January 2011 Problem Statement The 802.11ac will increase number of cases in which the primary and the non-primary channels overlap Currently 802.11ac has inadequate rules and means to protect a primary channel over a non-primary channel Jarkko Kneckt (Nokia)

Targets of the Channels Protection January 2011 Targets of the Channels Protection The legacy 802.11a/n with 20 MHz have NAV protection present in all TXOPs Protection level of 802.11ac 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 Jarkko Kneckt (Nokia)

Background Information January 2011 Detecting OBSS Background Information Each device calculates backoff and receives transmissions in its primary channel The AP receives a 802.11ac PLCP header with unallocated Group ID or Nsts values The STA receives a 802.11ac 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 Jarkko Kneckt (Nokia)

Background Information January 2011 OBSSs Examples Background Information Single 802.11ac 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 802.11a/n BSS may transmit only in non-primary channels Non-congested 802.11ac BSS may transmit only in subset, i.e. primary and secondary , channels The other 802.11ac BSS transmitting at the same operating channels The other 802.11ac BSS operating in 160 MHz mode 160 MHz BSS may have its primary channel at separate 80 MHz channel Jarkko Kneckt (Nokia)

Primary Channel Selection Rules January 2011 Background Information 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 Jarkko Kneckt (Nokia)

January 2011 Problem Statement The 802.11ac will increase the number of cases in which the primary and the non-primary channels overlap Currently 802.11ac 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 Jarkko Kneckt (Nokia)

Challenge: Protecting Primary Channel over a Non-primary Channel January 2011 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 Jarkko Kneckt (Nokia)

Improved Co-existence: NAV to Protect Primary Channel January 2011 doc.: IEEE 802.11-11/XXXXr0 January 2011 Improved Co-existence: NAV to Protect Primary Channel TXOP holder commands a selected STA to send a CTSS 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 The CTSS reserves the primary channel for 5 – 20 ms The buffered payload may be transmitted Jarkko Kneckt (Nokia) Jarkko Kneckt (Nokia)

Key concepts of the primary channel protection January 2011 Key concepts of the primary channel protection Enables BSS to protect its primary channel over secondary channels Avoids hidden terminal problems Improves the efficiency of the non-primary channels sharing Enables BSS to transmit the buffered traffic Avoids buffer overflow The BSS recover from congestion Jarkko Kneckt (Nokia)

Example Protecting Primary Channel January 2011 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 Jarkko Kneckt (Nokia)

Example Sharing Non-Primary Channels January 2011 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 Jarkko Kneckt (Nokia)

Challenge: Increasing TXOP Bandwidth January 2011 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 802.11ac RTS CTS has CCA measurements on both the transmitter and the receiver This is improvement, but not the same as virtual carrier sensing Jarkko Kneckt (Nokia)

Improved Co-Existence: Virtual Carrier Sensing by Reserving STA January 2011 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 reservation method 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 Jarkko Kneckt (Nokia)

Improved Co-Existence: Virtual Carrier Sensing by Reserving STA January 2011 Improved Co-Existence: Virtual Carrier Sensing by Reserving STA The reserving STA may: transmits a frame to reserve the channel Respond to RTS CTS signaling Report to the reservation success at the predefined time The reserving STA enables the virtual carrier sensing to TXOP obtaining at the secondary channels Jarkko Kneckt (Nokia)

Example Increasing TXOP Bandwidth January 2011 Example Increasing TXOP Bandwidth The TXOP holder commands with a frame the reserving STA to reserve the secondary channel The reserving STA waits for the RTS CTS signaling to be performed at the response timeout The reserving STA may be commanded to reserve the channel Jarkko Kneckt (Nokia)

Example Increasing TXOP Bandwidth January 2011 Example Increasing TXOP Bandwidth The TXOP holder commands with a frame the reserving STA to reserve the tertiary and quaternary channels The reserving STA is capable to reserve the tertiary and quaternary channels and indicates the success at the time reporting time, specified by the TXOP holder Please note: The timing of the OK transmission may be freely decided by AP Any reservation mechanism may be used, i.e. not limited by proposal Jarkko Kneckt (Nokia)

Summary The problems are: January 2011 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 Jarkko Kneckt (Nokia)

January 2011 Pre-Motion Include the normative text as defined in 11-11-152-r0 to 11-09-992 Specification Framework for TGac. Y N A Jarkko Kneckt (Nokia)