Noncoherent multi-way relay based on fast frequency-hopping M-ary frequency-shift keying

Information exchange among a group of users is implemented with the aid of fast frequency-hopping M-ary frequency-shift keying multi-way relay (FFH/MFSK MWR). The FFH/MFSK MWR scheme uses two time-slots per symbol for achieving the information exchange, regardless of the number of users involved. During the first time-slot, all the users communicate with a relay based on the FFH/MFSK principles. Then, without recovery of the symbols received, the relay forms a time-frequency (TF) matrix, which is forwarded to all the users during the second time-slot. During the second time-slot, each user receives signals from the relay and, based on which, detects the other users´ information. In the FFH/MFSK MWR scheme, both the relay and the users use square-law assisted noncoherent techniques for detection. While the relay uses simple threshold detection, three types of detectors, namely the maximum likelihood multiuser detector (ML-MUD), sub-optimum ML-MUD (SML-MUD) and the majority vote based single-user detector (MV-SUD), are considered for detection at the users. Finally, in this paper, the error performance of the FFH/MFSK MWR systems is investigated by simulations, when assuming communications over Rayleigh fading channels.