Three-way relaying systems using iterative spatial demapping

This paper proposes an iterative spatial demapping (ISM) scheme for simultaneous data exchange in three-way relaying systems where each user does not have direct links to the other users. Based on a priori knowledge provided by the decoders, ISM demapper makes the simultaneous data exchange only within two transmission phases by the help of a relay. The proposed structure is very simple since only two 2-state (memory 1) convolutional codes (CC) are used by each user: first CC is with rate-1 as doped accumulator (inner encoder) and the other is with rate-1/2 (outer encoder). The performances are evaluated by computer simulations in additive white Gaussian noise (AWGN) and two cascaded frequency-flat block Rayleigh fading channels. Bit-error-rate (BER) performance results show that clear turbo cliff can be achieved, with a transmit power close enough to the theoretical limit, for each user in AWGN channels. Extrinsic information transfer (EXIT) chart analysis is also presented to evaluate the convergence property of the iterative decoding algorithm. Since the proposed technique is spectrally efficient, it has a plenty of potential applications for future multi-way relaying systems where power and spectrum efficiency as well as energy consumption due to signal processing are of significant importance.