Veja esta página da web: Cisco ClientLink: desempenho otimizado do dispositivo com 802.11n
To understand how this works, consider a single transmitter 802.11a/g client sending an uplink packet to an 802.11n access point with multiple transceivers. The access point receives the signal on each of its three receive antennas. Each received signal has a different phase and amplitude based on the characteristics of the space between the antenna and the client. The access point processes the three received signals into one reinforced signal by adjusting their phases and amplitudes to form the best possible signal. The algorithm it uses, called maximal ratio combining (MRC), is typically used on all 802.11n access points (see Figure 2). MRC only helps in the uplink direction, enabling the access point to "hear" the client better.