Apparatus for multicast transmissions in wireless local area networks
View Patent ↗Message formats and apparatus are described that serve to reserve access to a communication medium in a multi-cast system. A first message, a multicast request-to-send message, includes a duration field having information representing the reserved time for a communication medium, a multicast receiver address field, a multicast transmitter address field, a field that identifies the number of slots for a clear-to-send response, and a field that identifies the number slots for a not-clear-to-send response. A second message includes a duration field, and a multicast receive address field. The second message has a format that can be used as one of a clear-to-send message in response to a multicast request-to-send message, a cancel-clear-to-send message that cancels a data transmission after the clear-to-send message is sent, and a not-clear-to-send message in response to the multicast request-to-send message.
1. 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.
2. The apparatus of claim 1 , wherein the multicast digital message comprises a multicast request-to-send message to reserve time in a communication medium to receive multicast data.
3. The apparatus of claim 1 , wherein the multicast clear-to-send slot number field defines a number of time intervals for responding to the multicast digital message.
4. The apparatus of claim 1 , wherein the multicast not-clear-to-send slot number field defines a number of time intervals for responding to the multicast digital message.
5. The apparatus of claim 1 , the multicast digital message further comprising a frame control field, herein the frame control field comprises a frame type identification.
6. A non-transitory computer program storage device containing computer instructions which, when executed in an apparatus that operates on a channel in a wireless communications medium, enable processing of a multicast digital message, the mutlicast digital message having a format comprising:
a duration field specifying a time period for which a 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 multicast medium access control (“MAC”) address of the transmitter of the multicast 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;
wherein the apparatus responds to the received multicast digital message by transmitting on the channel 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;
wherein a network allocation vector of the apparatus is reset 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.
7. The storage device of claim 6 , wherein the multicast digital message comprises a multicast request-to-send message to reserve time in a communication medium to receive multicast data.
8. The storage device of claim 6 , wherein the multicast clear-to-send slot number field defines a number of time intervals for responding to the multicast digital message.
9. The storage device of claim 6 , wherein the multicast not-clear-to-send slot number field defines a number of time intervals for responding to the multicast digital message.
10. The storage device of claim 6 , the multicast digital message further comprising a frame control field, wherein the frame control field comprises a frame type identification.
11. 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 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 processor that responds to the received multicast digital message by using a transmitter to transmit on the channel a clear to send message by utilizing the transmission time slots in a contention period to send the positive reply signal; and
wherein the processor further acts to transmit a cancel clear to send message on the channel 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.
12. A non-transitory computer program storage device containing computer instructions which, when executed in an apparatus that operates on a channel in a wireless communications medium, enable processing of a multicast digital message, the multicast digital message having a format comprising:
a duration field specifying a time period for which a 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 multicast medium access control (“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;
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
wherein the apparatus responds to the received multicast digital message by transmitting on the channel a clear to send message by utilizing the transmission time slots in a contention period to send the positive reply signal;
wherein a cancel clear to send message is transmitted on the channel 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.