Explicit multiuser beamforming training in a wireless local area network

A method for beamforming training in a wireless communication network, the method comprising:

• receiving, at a first communication device, a first data unit from a second communication device, the first data unit including respective resource allocation indications indicating respective resources allocated for transmission by multiple communication devices, the multiple communication devices including the first communication device and one or more third communication devices, the respective resource allocation indications indicating one or both of a) respective frequency portions for transmission of respective null data packets (NDPs) by respective ones of the multiple communication devices, and b) respective one or more spatial streams allocated for transmission of the respective NDPs by the respective ones of the multiple communication devices;
• in response to receiving the first data unit, transmitting, by the first communication device, an NDP to the second communication device simultaneously with transmission of one or more other NDPs by the one or more third communication devices, wherein the NDP i) includes a set of one or more training signals that allow the second communication device to estimate a communication channel from the first communication device to the second communication device, ii) was transmitted by the first communication device using the one or both of a) the frequency portion and b) the one or more spatial streams as indicated by the resource allocation indication corresponding to the first communication device in the first data unit that was transmitted to the multiple communication devices, and iii) omits a data portions;
• and
• receiving, at the first communication device, a second data unit that includes respective beamforming feedback data units for respective ones of the multiple communication devices, the beamforming feedback data units including an aggregate media access control protocol data unit (A-MPDU) that includes a plurality of fragments of beamforming training information for the first communication device, the beamforming training information in the A-MPDU having been generated by the second communication device based on the set of one or more training signals included in the NDP transmitted by the first communication device.