This paper considers a two-user downlink transmission in intelligent reflecting surface (IRS) aided network over fading channels. Particularly, non-orthogonal multiple access (NOMA) and two orthogonal multiple access (OMA) schemes, namely, time division multiple access (TDMA) and frequency division multiple access (FDMA), are studied. The objective is to maximize the system average sum rate for the delay-tolerant transmission. We propose two adjustment schemes, namely, dynamic phase adjustment and one-time phase adjustment. The power budget, minimum average data rate, and discrete unit modulus reflection coefficient are considered as constrains. To solve the problem, two phase shifters adjustment algorithms with low complexity are proposed to obtain near optimal solutions. With given phase shifters and satisfaction of time-sharing condition, the optimal resource allocations are obtained using the Lagrangian dual decomposition. The numerical results reveal that: i) the average sum rate of proposed NOMA network aided by IRS outperforms the conventional NOMA network over fading channels; ii) with continuous IRS adjustment in the fading block, the proposed TDMA scheme performs better than the FDMA scheme; iii) increasing the minimum average user rate requirement has less impact on the proposed IRS-NOMA system than on the IRS-OMA system.

中文翻译：

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衰落信道上的智能反射面辅助多址接入

本文考虑了智能反射面 (IRS) 辅助网络中衰落信道上的双用户下行链路传输。特别地，研究了非正交多址(NOMA)和两种正交多址(OMA)方案，即时分多址(TDMA)和频分多址(FDMA)。目标是最大化延迟容忍传输的系统平均总速率。我们提出了两种调整方案，即动态相位调整和一次性相位调整。功率预算、最小平均数据速率和离散单位模数反射系数被视为约束。针对该问题，提出了两种低复杂度的移相器调整算法，以获得接近最优的解。给定移相器并满足分时条件，使用拉格朗日对偶分解获得最佳资源分配。数值结果表明：i) 在 IRS 辅助下，提议的 NOMA 网络的平均总和率优于传统的 NOMA 网络在衰落信道上；ii) 随着衰落块中的连续 IRS 调整，所提出的 TDMA 方案比 FDMA 方案表现更好；iii) 增加最低平均用户速率要求对提议的 IRS-NOMA 系统的影响小于对 IRS-OMA 系统的影响。建议的 TDMA 方案比 FDMA 方案表现更好；iii) 增加最低平均用户速率要求对提议的 IRS-NOMA 系统的影响小于对 IRS-OMA 系统的影响。建议的 TDMA 方案比 FDMA 方案表现更好；iii) 增加最低平均用户速率要求对提议的 IRS-NOMA 系统的影响小于对 IRS-OMA 系统的影响。