Operation rules for > 40MHz Bandwidth

1. Operation rules for > 40MHz Bandwidth Authors: Date: 2010-09-14 Jarkko Kneckt, Nokia Corporation

2. Abstract The presentation discusses how to operate in a scenario where a tertiary or quaternary channel of a BSS overlaps with the primary channel of another BSS? Jarkko Kneckt, Nokia Corporation

3. Targets of Operation Rules • Targets of the channel operation rules in 802.11ac: • Simplify and speed-up the discovery and scanning operations • Simplify the frequency use • Enable efficient resource use • Avoid introducing new type of “hidden terminal” problems Jarkko Kneckt, Nokia Corporation

4. Channelization of 802.11ac • Channelization is taken from 11-09-992r13: • The 20/40/80MHz transmissions may be performed in IEEE channels as shown below Jarkko Kneckt, Nokia Corporation

5. Question for Channels Operation Rules • May a BSS use its tertiary or quaternary channel (20MHz) when it discovers an overlap with the primary channel (20MHz) of another BSS? • Lets compare two alternatives: • “NO”: Tertiary and quaternary channel shall not be used at IEEE channel that contains primary channel of another BSS • Justification: 802.11n rule 11.14.3.1 restricts BSS to use its secondary channel at a channel that has primary channel • Following the same logic, the tertiary and quaternary channels use is restricted in IEEE channel containing primary channel • “YES”: Tertiary and quaternary channel may operate at IEEE channel that contains primary channel of the other BSS • Justification: 802.11n 11.14.3.1 does not define primary channel operation in channel containing tertiary or quaternary channels Jarkko Kneckt, Nokia Corporation

6. “NO” The NAV and CCA protection of the primary channel are available for all (prim,sec,ter,quar) channels Primary channel of another BSS can possibly overlap the secondary channel and this can limit the transmission bandwidth to 20 MHz Primary channel of another BSS in tertiary or quaternary channel limits the transmission bandwidth to 40 MHz “YES” Only the CCA protection is available when primary co-exists at the same channel as (sec,ter,quar) channel of another BSS The STA may aggressively use the IEEE channels in which other BSSs primary channels operate, no transmission bandwidth limitations Possible to use the full 80 MHz Features of the Channel Operation Rules Alternatives Jarkko Kneckt, Nokia Corporation

7. Throughput of “NO”: Light traffic All traffic is transmitted Depending on the traffic model, TX time may be little longer than in “YES” Moderate traffic In uneven traffic load, the high load BSSs may use at maximum 40 MHz bandwidth High traffic At maximum one BSS may use 40 MHz bandwidth Some small degradation due to CSMA/CA collisions of traditional hidden terminals may occur Throughput of “YES”: Light traffic All traffic is transmitted Depending on the traffic model, the TX time may be little shorter than in “NO” Moderate traffic The lack of NAV causes collisions and lowers throughput In unevenly loaded BSSs, the BSS may benefit from higher bandwidth High Traffic All BSS try to use the whole 80 MHz bandwidth, high variation in throughput may occur High amount of retransmissions due lack of NAV protection lowers throughput Severe hidden terminal problems Performance of Channel Operation Rules Alternatives Jarkko Kneckt, Nokia Corporation

8. Strawpoll 1 • Are you in favour of: • “NO”. Tertiary and quaternary channel shall not operate at IEEE channel that contains primary channel of the other BSS: • “YES”. Tertiary and quaternary channel may operate at IEEE channel that contains primary channel of the other BSS: Jarkko Kneckt, Nokia Corporation

9. Strawpoll 2 • Should all transmissions be protected with CCA and NAV: • Yes • No Jarkko Kneckt, Nokia Corporation

10. References • 11-09-992r13 Jarkko Kneckt, Nokia Corporation