Patent ID: 8743784

Claim:
A method for wireless communications, comprising: transmitting a non-null data packet having a preamble with a Very High Throughput Signal B (VHT-SIG-B) field; generating a null data packet (NDP), wherein the VHT-SIG-B field of the preamble of the NDP comprises a particular bit pattern; and transmitting the NDP, wherein transmitting the NDP comprises using a 20 MHz channel and the particular bit pattern comprises 20 bits comprising 0 0 0 0 0 1 1 1 0 1 0 0 0 1 0 0 0 0 1 0, using a 40 MHz channel and the particular bit pattern comprises 21 bits comprising 1 0 1 0 0 1 0 1 1 0 1 0 0 0 1 0 0 0 0 1 1, or using an 80 MHz channel and the particular pattern comprises 23 bits comprising 0 1 0 1 0 0 1 1 0 0 1 0 1 1 1 1 1 1 1 0 0 1 0.