Iterative PIC detection and channel estimation for DS-CDMA communications in AWGN and satellite/HAPS channels

This paper presents a turbo multiuser detector for turbo-coded DS-code division multiple access (CDMA) systems, based on the utilisation of a parallel interference cancellator (PIC) and a bank of turbo decoders: in the proposed receiver the interference cancellation is performed after each constituent decoder of the turbo decoding scheme. Moreover, the soft outputs of the turbo decoders are used iteratively to improve the channel parameter estimation during the updating step, which is formally equivalent to one step of the expectation-maximisation algorithm. By means of computer simulations, we will show that the proposed receiver achieves performance comparable with the one obtained by systems, which suppose perfect knowledge of the channel parameters for medium to high system loads, in AWGN channel. Finally, the proposed receiver is also applied in HAPS (high altitude platform station) and satellite channel, for different values of the elevation angle, affording remarkable performance.

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