Method, apparatus and system of spatial division multiple access communication in a wireless local area network
Some demonstrative embodiments of the invention include a method, apparatus for concurrently transmitting data to two or more wireless stations.
1. A method of performing simultaneous downlink transmission over a wireless medium to a plurality of wireless stations, the method comprising:
selecting a set of the plurality of wireless stations according to one or more ranking criteria; and
reserving the wireless medium for a duration sufficient for completing the simultaneous downlink transmission to the wireless stations of said set,
wherein selecting said set comprises selecting a preliminary subset based on channel state estimation received during a first learning interval, and selecting a main subset based on channel state estimation received during a second learning interval including said first learning interval,
wherein said method further comprises performing simultaneous downlink transmission to stations of said main subset after performing simultaneous downlink transmission to stations of said preliminary subset,
wherein said main and preliminary subsets are defined by a set of beamforming vectors, associated with the corresponding subset, and
wherein a rate of each frame in the subset is changeable during a lifetime of the subset.
2. The method of claim 1 , wherein reserving the wireless medium comprises reserving the wireless medium for a predefined high-priority transmission interval.
3. The method of claim 1 comprising assigning data to be transmitted to the plurality of wireless stations into a plurality of respective queues according to one or more priorities.
4. The method of claim 1 , wherein said ranking criteria comprise one or more criteria related to data priority, signal strength, prior subset selection information, and one or more quality-of-service parameters.
5. The method of claim 1 , wherein reserving the wireless medium comprises transmitting a clear-to-send-to-self frame having a value corresponding to said duration.
6. The method of claim 1 comprising transmitting at least channel request frame to at least one station of said set, and receiving an estimate of a channel state corresponding to said station in response to said channel request frame.
7. The method of claim 1 comprising estimating at least one channel state corresponding to at least one station of said set.
8. The method of claim 7 comprising receiving from one or more of said set of wireless stations a response to an uplink query, wherein estimating said channel state comprises estimating said channel state based on said response.
9. The method of claim 8 comprising sending a null-data frame to the wireless stations of said set, wherein receiving said response comprises receiving acknowledgement frames from said wireless stations.
10. The method of 7 comprising computing beamforming vectors based on said channel state, and the selected subset.
11. The method of claim 1 , wherein selecting said set comprises partially equalized time spans of data to be transmitted to the wireless stations of said set.
12. The method of claim 11 , wherein said partially equalized time spans comprises selecting wireless stations having data sequences of comparable lengths in their respective queues and having comparable receive signal strengths.
13. The method of claim 11 , wherein partially equalizing said time spans comprises fragmenting a first frame into a plurality of fragments having a duration equal to a duration of a second frame.
14. The method of claim 1 , further comprising selecting a partial subset of said set of wireless stations according to a further ranking criterion.
15. The method of claim 14 , wherein said further ranking criterion comprises one or more criteria selected from a group of optimization metrics including a maximum sum-rate, a maximum weighted sum-rate based on queue status, and a maximum of the minimum rate of the wireless stations in the subset.
16. The method of claim 14 , wherein selecting said partial subset comprises partially equalized time spans of data to be transmitted to the wireless stations of said subset.
17. The method of claim 16 , wherein said partially equalized time spans comprises selecting wireless stations having data sequences of comparable lengths in their respective queues and having comparable receive signal strengths.
18. The method of claim 16 , wherein said partially equalized time spans comprises controlling a transmit rate for the wireless stations of said subset.
19. The method of claim 18 , wherein controlling said transmit rate comprises adjusting a power allocation for each of the wireless stations of said subset.