Improving the capacity of CDMA systems using convolutional coding and interference cancellation

The authors compare methods of reducing the co-channel interference on a DS-CDMA downlink signal by employing convolutional coding at the base station and a Viterbi decoder as the initial estimator for a parallel cancellation scheme. The combination of a matched filter and the Viterbi algorithm is shown to afford increased performance compared to equivalent bandwidth systems which do not use forward error correction. The use of a Wiener filter to collapse the spectrum of the spread signal leads to even greater capacity improvements. The systems discussed may be implemented with an affordable increase in receiver complexity and processing delay