Abstract
Two-path successive relaying (TPSR) systems have been recently proposed as powerful candidates for improving the spectral efficiency of cooperative communications. The previously reported investigations for such systems are limited to information-theoretic analysis, parameters estimation, interference cancellation, and data detection. In this contribution, we discuss the problem of modulation classification (MC) for TPSR systems for the first time in the literature. We exploit the specific nature of the received signal to derive a maximum-likelihood (ML) estimate of the modulation format of a received signal. Since the exact ML solution is shown to be too challenging for real applications, we resort to the expectation-maximization (EM) method as a low complexity iterative procedure. Channel estimation is also introduced as an auxiliary task for the proposed algorithm. The computational complexity analysis and simulation results confirm the effectiveness of the proposed iterative algorithm where no existing alternatives are available.