An iterative receiver structure is proposed for turbo-coded FHMA systems. In frequency-hop multiple access (FHMA) systems, the adjacent channel interference (ACI) is the major contributor of MAI if orthogonal hopping patterns are used. The ACI is a function of the tone spacings of the adjacent subchannels and the rolloff factor of the pulse-shaping filter. A low complexity iterative multiuser detector is developed to mitigate the degrading effect of ACI in the FHMA systems. Iterations of the demodulator and decoder are used as the mechanism to estimate and mitigate the MAI in the FHMA system. In addition, an iterative decoder structure based on a modified turbo decoding algorithm is proposed. Compared to maximum-likelihood multiuser detection, the proposed system is more practical and its complexity is only a linear function of the number of users. Simulation results show that the proposed iterative receiver structure offers significant performance gains in bandwidth efficiency and the required signal-to-noise ratio (SNR) for a target BER over a noniterative receiver structure.
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