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Efficient channel code assignment scheme for multiple users in CDMA systems

Effective transmission of multiple video signals over a CDMA system simultaneously is investigated in this work. A channel code assignment scheme that efficiently protects compressed bitstreams while minimizing multiple access interference (MAI) is proposed. First, each video signal is coded with a two-layer structure that consists of the base and the enhanced bitstreams according to the bit importance. Then, these bitstreams are protected against transmission errors with channel codes such as RCPC. Better protection of higher bit-rate video requires more multicodes in spreading, which can lead to a severe multiple access interference problem. We set up a framework to a joint design of channel codes and spreading codes with the feedback of the channel status, and provide a solution to deal with the trade-off between channel coding rates and the assigned number of multicodes to achieve efficient transmission. Preliminary experimental results are presented to demonstrate the performance of the proposed channel code assignment scheme.