Low complexity linear detection for asynchronous CDMA signals CDMA uplink over a frequency selective channel”,European Signal Porcessing Confernce

In this paper, a suboptimal low complexity structure for joint linear detection of CDMA signals is proposed. The optimal joint linear zero-forcing or minimum mean squared error detectors use a vector model of the transmission where the channel is represented by a matrix. Due to the finite memory of the channel, most of the blocks of the channel autocorrela-tion matrix are equal to zero. It is then possible to put this structure into profit to derive low complexity implementa-tions for these detectors. In this paper, the optimal linear sys-tem resolution is approximated by overlapped smaller sub-systems. The performance and the complexity of the result-ing detector are analyzed for both downlink and uplink communications over frequency selective channels for peri-odic spreading codes with a period equal to the symbol pe-riod as well as for random-like codes. The trade-off between complexity and performance is flexible, which offers a great advantage to the proposed solution. 1