Amplify–Quantize–Forward Relay Channel With Quadrature Amplitude Modulation

Abstract

This paper considers an amplify–quantize–forward (AQF) relay channel withM-ary quadrature amplitude modulation, where the relay implements amplification for the received signal and a uniform quantization for each of real and imaginary parts of the amplified version. Two step-size determinant methods for the uniform quantization affected by the power constraint at the relay are proposed by deriving the power and the mean square error for the quantized signal. Given the step size for the quantization, the maximum-likelihood detection is presented, and a linear combining detection called equivalent maximum ratio combining is proposed to reduce the detection complexity in the AQF relay channel. The simulation results confirm the superiority of the proposed quantization methods and detection algorithms.