This paper investigates the information-theoretic energy efficiency of intelligent reflecting surface (IRS)-aided wireless communication systems, taking into account the statistical quality-of-service (QoS) constraints on delay violation probabilities. Specifically, effective capacity is adopted to capture the maximum constant arrival rate that can be supported by a time-varying service process while fulfilling these statistical QoS requirements. We derive the minimum bit energy required for the IRS-aided wireless communication system under QoS constraints and analyze the spectral efficiency and energy efficiency tradeoff at low but nonzero signal-to-noise ratio (SNR) levels by also characterizing the wideband slope values. Our analysis demonstrates that the energy efficiency for the considered system under statistical QoS constraints can approach that for a system without QoS limitations in the low-SNR regime. Additionally, deploying a sufficiently large number of practical IRS reflecting elements can substantially reduce energy consumption required to achieve desired spectral efficiency performance in the low-power regime, even with limited bit-resolution phase shifters. Besides, we reveal that compared with the results applied to the low-power regime, higher effective capacity performance can be achieved in scenarios with sparse multipath fading while achieving the same minimum bit energy in the wideband regime.

翻译：本文从信息论角度研究了智能反射面辅助无线通信系统的能效特性，同时考虑时延违反概率的统计服务质量约束。具体而言，采用有效容量表征时变服务过程在满足统计QoS要求下可支持的最大恒定到达速率。我们推导了QoS约束下IRS辅助无线通信系统所需的最小比特能量，并通过表征宽带斜率值，分析了低信噪比条件下的频谱效率与能效权衡关系。分析表明，在低信噪比区域，所研究系统在统计QoS约束下的能效可逼近无QoS限制系统的能效水平。此外，在低功率区域，部署足够数量的实用IRS反射单元可显著降低实现目标频谱效率性能所需的能耗，即使采用有限比特分辨率的移相器亦能达成。同时我们发现，与低功率区域的应用结果相比，在达到相同最小比特能量的宽带区域，稀疏多径衰落场景下能够获得更高的有效容量性能。