In this paper, we consider a dual-hop mixed THz-RF system model for backhaul-fronthaul applications where the link between source and destination is established only through the relay node in which decode-and-forward relaying protocol is used. The THz link suffers from the joint impact of antenna misalignment and stochastic characteristics of wireless channels, including the effect of environmental conditions such as pressure, humidity, and temperature. The envelope of THz link in the first hop follows a generalized $\alpha-\mu$ distribution, and for the RF end, the Nakagami-$m$ distribution is considered. In this context, we obtain new closed-form expressions of the cumulative density function and the moment-generating function of the end-to-end signal-to-noise ratio. Further, we derive the average symbol error rate expressions for coherent rectangular quadrature amplitude modulation (RQAM) and coherent hexagonal QAM (HQAM), as well as the non-coherent modulation scheme. The asymptotic behavior is also discussed to examine the system's diversity. Furthermore, the impact of several parameters, such as fading coefficients of individual links and antenna misalignment, as well as the distance between nodes, are also highlighted in the system's performance. Moreover, Monte Carlo simulations are used to validate the presented analytical framework. Finally, the presented numerical insights aid in the extraction of practical design principles.

翻译：本文针对回传-前传应用场景，构建了双跳混合太赫兹-射频系统模型，其中信源与信宿仅通过采用解码转发协议的中继节点建立链路。太赫兹链路同时受天线对准误差与无线信道随机特性（包括气压、湿度、温度等环境条件影响）的共同作用。第一跳太赫兹链路的包络服从广义$\alpha-\mu$分布，而射频端采用Nakagami-$m$分布。在此框架下，我们获得了端到端信噪比的累积分布函数与矩母函数的新型闭式表达式。进一步推导了相干矩形正交幅度调制与相干六边形QAM以及非相干调制方案的平均符号错误率表达式，并讨论系统分集增益的渐近特性。此外，重点分析了各链路衰落系数、天线对准误差及节点间距等参数对系统性能的影响。蒙特卡洛仿真验证了所提分析框架的有效性。最终，所呈现的数值分析结果有助于提取实际设计准则。