Hi All,
I present the contribution 24/719 this morning, a lot of members ask me to clarify why it's M*N times frame agreement exchange. I re-think about it, and make the following illustration.
First, let's see how the co-hosted BSSID and MBSSID work in a shared radio(we call "co-radio APs " below) in intrastucture network. Regardless any AP PS scheme, for TX, all the APs on the same radio access the channel in TDMA manner. For RX, all the APs are always "on" to receive the STAs UL traffic or other frames, and make the response with ACK or other frames. E.g. if a STA sends a broadcast probe request frame, all the APs in the same radio should respond with probe response frames. To reduce the overhead issue caused by probe response frames in co-located APs scheme, 802.11 involves MBSSID feature to "merge" a number of probe response frames to one many years ago.
If we agree on the above. Let's see how MAP TX co-ordination work.
Take C-TDMA as example, If an AP(assume AP21 on Rounter1) obtains the TXOP and becomes the TXOP owner, it can grant the portion of TXOP to any APs (AP11, AP12,etc.) on Router2 via a Trigger frame, and the corresponding AP will schedule the DL/UL traffic for in-BSS traffic delivery. If we intend to have a agreement between the pair of AP before MAP co-ordination TX, then, in this case, AP21 should set up the agreement with all the APs on Rounter2.
Back to the precondition, two APs shall have a overlapping time slot (and channel) in any MAP co-ordination scheme. For the co-radio APs case(regardless any AP PS scheme), as all the APs (on Rounter2) can hear the frame transmitted by any APs (on Rounter1) and make the response at any time, we could say the operation time always overlapping between any two APs on different Routers. That's, the number of AP pairs is equal to M*N in co-radio APs scenario(neither more nor less than).
Based on the explanation above, if we agree the direction to reduce the overhead issue in MAP scheme, the idea is to make some "external signaling" to become "internal signaling", E.g. Adding or deleting APs on Rounter1 won't cause any update signaling sending to the APs on Rounter2 if we have the MAP Set concept. Also, such concept also can reduce the overhead issues in Radio power/off and channel switch scenario.
Again, this contribution only provide some high level thought, if our group agree with this direction, we could have further study and discuss more in details.
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Thanks
Best Regards
Jay Yang (杨志杰)