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.

中文翻译：

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两路连续中继系统的迭代调制分类算法

最近提出了双路径连续中继 (TPSR) 系统作为提高协作通信频谱效率的有力候选者。先前报告的对此类系统的研究仅限于信息理论分析、参数估计、干扰消除和数据检测。在这篇文章中，我们在文献中首次讨论了 TPSR 系统的调制分类 (MC) 问题。我们利用接收信号的特定性质来推导出接收信号调制格式的最大似然 (ML) 估计。由于精确的 ML 解决方案被证明对实际应用来说太具有挑战性，因此我们采用期望最大化 (EM) 方法作为低复杂度的迭代过程。信道估计也被引入作为所提出算法的辅助任务。计算复杂度分析和仿真结果证实了所提出的迭代算法在没有现有替代方案可用的情况下的有效性。