Packet Combining Considerations for Random-Access Networks
If the channel is particularly poor, a radio may be unable to decode any individual packet reception. Packet combining utilizes retransmission diversity to improve the probability that a message can be decoded. In cases where the transmitter is known to the receiver (e.g., communication using a dedicated time slot), the receiver can request that the transmitter resend the message. However, in random access networks, a receiver may hear packets from many transmitters. If a received message is not decodable, the receiver may not know the identity of the transmitter and thus be unable to request a retransmission directly.