Enhanced Soft-Handover for DS-CDMA Systems using Complementary Error Correction Codes

In order to enhance soft-handover performance in the downlink of DS-CDMA systems, we propose to use different codes at the base stations in the active set to encode the information sequence targeted to a mobile station. For reliable information recovery, in case all links except one happen to be simultaneously in deep fade, self-decodable complementary punctured convolution codes, inspired from Hybrid ARQ III, are used. When turbo-decoding is feasible at the mobile station, new complementary codes, using different interleavers followed by a common systematic recursive convolutional encoder, are proposed for an additional enhancement in performance. Experimental evaluation of the enhancement in performance provided by com- plementary coding is carried for both Gaussian and multipath Rayleigh fading channels. The proposed coding schemes can provide very significant gains. In some cases, gains around 4 dB can be achieved. Index Terms—Soft-handover, DS-CDMA, Complementary punctured convolutional codes, Turbo-coding.

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