Relaying increases the coverage area and reliability of wireless communications systems by mitigating the fading effect on the received signal. Most technical contributions in the context of these systems assume ideal hardware (ID) by neglecting the non-idealities of the transceivers, which include phase noise, in-phase/quadrature mismatch and high power amplifier nonlinearities. These non-idealities create distortion on the received signal by causing variations in the phase and attenuating the amplitude. The resulting deterioration of the performance of wireless communication systems is further magnified as the frequency of transmission increases. In this paper, we investigate the aggregate impact of hardware impairments (HI) on the general multi-hop relay system using amplify-and-forward (AF) and decode-and-forward (DF) relaying techniques over a general H-fading model. H-fading model includes free space optics, radio frequency, millimeter wave, Terahertz, and underwater fading models. Closed-form expressions of outage probability, bit error probability and ergodic capacity are derived in terms of H-functions. Following an asymptotic analysis at high signal-to-noise ratio (SNR), practical optimization problems have been formulated with the objective of finding the optimal level of HI subject to the limitation on the total HI level. The analytical solution has been derived for the Nakagami-m fading channel which is a special case of H-fading for AF and DF relaying techniques. The overall instantaneous signal-to-noise-plus-distortion ratio has been demonstrated to reach a ceiling at high SNRs which has a reciprocal proportion to the HI level of all hops transceivers on the contrary to the ID.

翻译：中继通过减轻接收信号的衰落效应，可增大无线通信系统的覆盖范围并提升可靠性。现有大多数相关技术贡献均假设理想硬件（ID），忽略了收发器非理想特性，包括相位噪声、同相/正交不平衡及高功率放大器非线性。这些非理想特性通过引起相位变化和幅度衰减，在接收信号中产生失真。随着传输频率增加，无线通信系统性能的恶化进一步加剧。本文研究了硬件损伤（HI）对通用多跳中继系统的综合影响，采用放大转发（AF）和解码转发（DF）中继技术，并基于通用H衰落模型进行分析。H衰落模型涵盖自由空间光通信、射频、毫米波、太赫兹及水下衰落模型。推导了中断概率、误码概率和遍历容量的闭式表达式，以H函数形式呈现。通过高信噪比（SNR）下的渐近分析，建立了以总HI水平约束下寻求最优HI水平为目标的实用优化问题。针对Nakagami-m衰落信道（H衰落的特例），推导了AF和DF中继技术的解析解。结果表明，与理想硬件情况相反，整体瞬时信噪比失真比在高信噪比时存在上限，该上限与所有跳数收发器的HI水平成反比。