Amplify-and-forward relaying with M-FSK modulation and coherent detection

Abstract—This paper develops a detection scheme based on the implicit pilot-symbol-assisted architecture of M-ary frequency-shift-keying (FSK) modulation in amplify-and-forward (AF) multiple-relay networks. It is shown that, at the expense of the low spectral efficiency inherent in FSK modulation, every transmitted symbol from the source to the destination can be used as a pilot symbol. In the proposed detection scheme, the destination combines the signals from the source and the relays to perform detection by using the estimated channels obtained from the implicit pilot symbols. Using the Gaussian approximation for the effective noise at the destination, an upper bound of the approximated bit-error-rate (BER) is provided. Simulation results reveal that the proposed scheme can significantly improve the BER performance when compared to previously proposed schemes in a temporally-correlated fading environment. The simulation results also verify the obtained upper bound on the approximated BER. Index Terms—Cooperative diversity, relay communications, frequency-shift-keying, fading channel, amplify-and-forward protocol. I