FIG. 2B is a representative Prior Art WLAN timing diagram including soundings. A typical operation of a WLAN includes beacon frames 220A-E sent periodically, e.g. at 100 ms intervals t0-t5. In a representative beacon interval, t0-t1 the following sub-intervals are shown: a contention free interval 224A, a sounding interval 226A and a contention interval 228A. During the contention free interval the WAP sends downlink user data communications sequentially to one or more of the stations in the WLAN. During the sounding interval one or more downstream links are probed to determine the channel characteristics thereof and using the CSI in the feedback from the sounding the beamforming matrix for each link subject to the sounding is determined. The soundings are conducted on a per link basis. The sounding feedback is different for each link. During the contention based interval carrier sense multiple access (CSMA) is used as a medium access control (MAC) methodology to allow any station to seize control of the channel and send uplink user data communications thereon to the WAP. In the next beacon interval t1-t2 there is a contention free interval 224B and a contention interval 228B. In the next beacon interval t2-t3 there is a contention free interval 224C, including one or more soundings 226C, and a contention interval 228C.
