Reliable multicast over the mobile packet radio channel

Point-to-multipoint (multicast) packet radio data transmission protocols over the erroneous vehicular communication environment are studied. In order to improve the reliability of the transmission, the ARQ (automatic repeat request) scheme is introduced onto the multicast packet data transmission, and several retransmission methods are compared. In the usual point-to-point ARQ schemes, response from the listener is either ACK or NAK. Thus, the listener responds with a reply frame regardless of whether the I-frame from the talker was received successfully. but in some cases, one of the ACK and the NAK responses is not necessary because the other has the opposite meaning. The approach is based on this point of view. The NAK is chosen for the response to the I-frame, so that if the I-frame is received successfully, then the listener issues no response to it. The method is called NAK only ARQ. The NAK only ARQ scheme has superior throughput characteristics in spite of its simplicity. Simulated performance comparisons are presented