Intelligent Reflecting Surfaces (IRS) have revolutionized wireless communication systems through their adaptive reconfiguration of the radio propagation environment. This paper compares an IRS-assisted non-orthogonal multiple access (NOMA) system and a relay-assisted NOMA system. The investigation delves into the impact of the number of IRS elements on the performance of a two-user NOMA system. A dynamic power allocation scheme is proposed based on the number of IRS elements. Specifically, analytical investigations reveal the range, upper, and lower bounds of power allocation coefficients. The asymptotic values of these bounds are also determined. Furthermore, an optimization problem is formulated to maximize the sum-rate while considering individual minimum rate constraints. The minimum number of passive reflecting elements required by the IRS is determined to meet the minimum target data rates for both users. Analytical calculations determine the optimal number of IRS elements, minimizing total power consumption. Simulation results confirm the superiority of the IRS over the decode-and-forward relay approach.

中文翻译：

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NOMA通信系统辅助IRS和中继传输

智能反射表面 (IRS) 通过对无线电传播环境的自适应重新配置，彻底改变了无线通信系统。本文比较了 IRS 辅助的非正交多址 (NOMA) 系统和中继辅助的 NOMA 系统。该调查深入研究了 IRS 元件数量对双用户 NOMA 系统性能的影响。提出了一种基于IRS元素数量的动态功率分配方案。具体来说，分析研究揭示了功率分配系数的范围、上限和下限。这些界限的渐近值也被确定。此外，制定优化问题以最大化总速率，同时考虑各个最小速率约束。 IRS 所需的无源反射元件的最小数量被确定为满足两个用户的最小目标数据速率。分析计算确定 IRS 元件的最佳数量，从而最大限度地降低总功耗。仿真结果证实了 IRS 相对于解码转发中继方法的优越性。