Maximum likelihood multi-user detection for fast frequency hopping/multiple frequency shift keying systems

The maximum likelihood (ML) multi-user detector is developed for fast frequency hopping/multiple frequency shift keying (FFH/MFSK) multiple access (MA) systems. The channels are modeled with Rayleigh fading and additive, white Gaussian noise (AWGN). The FFH system has L chips per symbol, and each user has a unique L-chip hopping pattern over 2^K frequencies. The M users are assumed to be chip-synchronized at the receiver, and the receiver performs non-coherent detection. The ML multiuser detector simultaneously performs diversity combining and joint symbol detection, but the computational requirements are prohibitive if the 2^KM symbol combinations are searched exhaustively. We propose a reduced-complexity multiuser detection algorithm for FFH/MFSK MA systems, and we demonstrate through simulations that the new algorithm performs better than existing multiuser detection algorithms on channels with AWGN and Rayleigh fading