A new fuzzy based joint DF relay selection and link adaptation

In this paper a new scheme is proposed for optimum selection of decode and forward (DF) relay jointly with link adaptation using adaptive modulation, coding and transmit power. The transmission power of the transmitter is constant, but powers of the relays are adaptable. The purpose is to maximize the spectral efficiency between the transmitter and the receiver, provided that the bit error rates (BER) at the receiver and at the selected relay are less than an acceptable level, and an individual average transmission power constraint is considered for each relay. The proposed scheme performs based on fuzzy logic, thus the processing load is limited, and it is easily operational in different environments. Numerical evaluations demonstrate a significant outperformance by the proposed scheme in comparison with the previously presented schemes.