In a wireless local area network (WLAN), an access point (AP) and a station (STA) may be equipped with smart antenna features; for example, a multiple beam/directional antenna system. Both the AP and the STA need to perform measurements to decide the best beam for transmitting to or receiving from another STA. STAs with multiple beams typically perform scanning on different beams in order to estimate which is the best beam to serve them. Scanning performed by the AP and/or STAs may use either a dummy packet, a data packet, an 802.11 acknowledgement (ACK), or broadcast packets. The measurements need to be updated frequently.
At an AP, the beam switching algorithm uses packets from a STA for the antenna measurements. The best beam (based on the received packet measurements, e.g., a received power or signal to interference plus noise ratio (SINR)) is then used to transmit packets to that STA. At the STA, the current beam switching algorithm may use the data packet or beacon to decide the correct receive and transmit antenna/beam for that AP. This method for antenna measurement is not very efficient, due to the amount of time needed to obtain enough measurements to decide the correct beam for each STA.
Another problem with this beam selection method is that the beam selection, for both receive and transmit, is based on measurements made on the received packets. However, in reality, the best beam for transmission might not be the same as the best beam for reception (especially for a frequency division duplex system).