The University of British Columbia

An adaptive retransmission diversity combining scheme is investigated for both the slotted and unslotted random access packet-switched code division multiple access networks over a frequency-selective Rayleigh fading channel. Multiple received noisy packets are combined on a bit by bit basis to form a single, more reliable packet. A novel mechanism to ensure a reliable packet combining operation is outlined. It is shown that packet combining is an effective mechanism for enhancing the network throughput and delay performance of the conventional DS/CDMA ALOHA, while sustaining a reasonable receiver complexity. This scheme is highly advantageous for systems which can tolerate a certain delay and operate over highly time-varying channels. We also examine the sensitivity of the system performance to the packet header failure rate and in the presence of feedback channel errors