A diversity combining DS/CDMA system with convolutional encoding and Viterbi decoding

Averaged diversity combining is applied to an asynchronous DS/CDMA system using convolutional encoding and Viterbi decoding. A CRC code is included in the scheme to trigger retransmission requests. Multiple received packets are combined on a bit by bit basis to form a single, more reliable packet. The error correcting decoder operates on the combined packet, as opposed to the most recently received individual packet (e.g. as in a type-I hybrid ARQ protocol), substantially increasing the probability of acceptance with each additional transmission. We show through analysis and simulation results that the proposed technique allows a significant increase in the CDMA system capacity, throughput and reliability