Patent ID: 8724546

Claim:
A method for generating a preamble of a data unit for transmission via a multiple input, multiple output (MIMO) communication channel, the method comprising: including, in a first sub-field of a first field of the preamble, a first indicator of a first set of a plurality of training sequences that corresponds to transmission of the data unit to a first receiver; including the plurality of training sequences in a second field of the preamble; including, in a third field of the preamble, a group identification indicator, wherein the group identification indicator indicates either (i) that the data unit corresponds to only one receiver, or (ii) an address of a group of multiple receivers including the first receiver and at least a second receiver; when the third field indicates that the data unit corresponds to only one receiver, including in a second sub-field of the first field of the preamble an indicator of the first receiver so that other receivers can determine that the data unit is not addressed to the other receivers; when the third field indicates the address of the group of multiple receivers, including in the second sub-field of the first field of the preamble a second indicator of a second set of the plurality of training sequences that corresponds to transmission of the data unit to the second receiver; and formatting the preamble such that the first field of the preamble will be transmitted prior to the second field of the preamble being transmitted.