Patent ID: 8737281

Claim:
An apparatus that receives a multicast digital message while operating on a channel in a wireless communication medium, the apparatus comprising: a receiver receiving the multicast digital message from a transmitter on the channel in the medium, the multicast digital message having a format comprising: a duration field specifying a time period for which the transmitter desires to reserve the medium; a multicast receiver address field specifying a multicast medium access control (“MAC”) address of the apparatus; a multicast transmitter address field specifying a MAC address of the transmitter of the multicast digital message; a multicast clear-to-send slot number field specifying transmission time slots in a contention period useful by the apparatus to send a positive reply signal; and a multicast not clear-to-send slot number field specifying transmission time slots in a contention period useful by the apparatus to send a negative reply signal; and a transmitter transmitting either a clear to send message or a not clear to send message by utilizing the transmission time slots in a contention period to send the positive reply signal or the transmission time slots in a contention period to send the negative reply signal respectively in response to the received multicast digital message; and a processor that resets a network allocation vector of the apparatus when no transmission on the channel is received in a time interval T between times T 1 and T 2 , wherein the time T 1 occurs at a time comprising a sum of: a time interval for receiving the multicast digital message; a time interval for transmission of the clear to send message multiplied by a number of clear to send message slots; a time interval for transmission of the not clear to send message multiplied by a number of not clear to send message slots; and a time interval for interframe guard intervals; and wherein the time T 2 occurs at the time T 1 added to a wait time.