Optimum Linear Decoding of Vector Quantisation Transmitted Over a CDMA Channel

The problem of joint source-channel and multi-user decoding for code division multiple access channels is considered. The block source-channel encoder is defined by a Vector Quantiser (VQ). The jointly optimum solution to such a problem has been considered before, but its extremely high complexity makes it impractical for systems with medium to large number of users and/or medium to large size of VQ code-book. Instead, the optimum linear decoder with a much lower complexity that minimises the mean-squared error is introduced. The optimum linear decoder is soft in the sense that it utilises all the soft information available at the receiver.