The 802.11ac also provides the support of VHT capabilities such as transmit beamforming (TxBF) control with sounding protocol and compressed beamforming feedback,downlink multi-user, multiple input, multiple output (DL MUMIMO),and VHT transmission opportunity (TXOP) power save through its VHT Capabilities Info field of the management frame. The sounding protocol is necessary for TxBF and DL MU-MIMO as the beamformer needs to acquire explicit channel state information in order to derive a steering matrix that could be used to optimize the reception at one or more beamformees.