Iterative Detection and Estimation for Multiple Access Interference Mitigation in Asynchronous Frequency-Hop Spread Spectrum

In this paper, we propose multiple-access interference (MAI) mitigation techniques for asynchronous slow frequency-hop spread spectrum systems that employ binary frequency-shift keying (BFSK). In such systems, MAI occurs if the hopping patterns of the users are not orthogonal. Under asynchronous transmission, the interference will have structure that can be exploited for interference mitigation. We apply an EM-based approach that results in an iterative algorithm to estimate the desired packet in the presence of one or more interfering signals. We compare the performance of this algorithm with that of a conventional noncoherent BFSK transceiver and show that the algorithm is particularly effective in the presence of strong interfering signals