Optimal Throughput Fairness Tradeoffs for Downlink Non-Orthogonal Multiple Access Over Fading Channels
Optimal Throughput Fairness Tradeoffs for Downlink Non-Orthogonal Multiple Access Over Fading Channels
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DOI：
10.1109/twc.2018.2803177
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发表时间：
2017-08
影响因子：
10.4
通讯作者：
Hong Xing;Yuanawei Liu;A. Nallanathan;Z. Ding;H. V. Poor
中科院分区：
文献类型：
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作者：
Hong Xing;Yuanawei Liu;A. Nallanathan;Z. Ding;H. V. Poor
最近，非正交多址（NOMA）作为5g使能技术之一引起了相当大的兴趣。然而，由于下行通信中信道条件较好的用户从NOMA中获得的收益本质上大于信道条件较差的用户，因此需要明智的设计来保证用户的公平性。本文研究了衰落信道上的双用户下行NOMA系统。对于容忍延迟的传输，在平均和峰值功率约束以及最小平均用户速率约束下，平均和速率最大化。利用拉格朗日对偶分解得到了发射机全信道状态信息下的最优资源分配，并根据分析结果制定了部分信道状态信息下的有效功率分配策略。同时，对于延迟限制传输，在完全CSIT下，在最大允许用户中断约束下，延迟限制吞吐量（DLT）的总和最大化，并且在部分CSIT下，对DLT的总和进行了分析。此外，还研究了最优正交多址（OMA）方案作为基准，证明了在全CSIT条件下NOMA方案优于OMA方案。最后，通过对平均求和速率（sum- dlt）与最小（最大）平均用户速率（中断）需求的不同权衡，模拟验证了理论分析。
Recently, non-orthogonal multiple access (NOMA) has attracted considerable interest as one of the 5G-enabling techniques. However, the users with better channel conditions in downlink communications intrinsically benefit more from NOMA than the users with worse channel conditions thanks to successive decoding, judicious designs are required to guarantee user fairness. In this paper, a two-user downlink NOMA system over fading channels is considered. For delay-tolerant transmission, the average sum rate is maximized subject to both average and peak-power constraints as well as a minimum average user rate constraint. The optimal resource allocation is obtained using the Lagrangian dual decomposition under full channel state information at the transmitter (CSIT), while an effective power allocation policy under partial CSIT is also developed based on analytical results. In parallel, for delay-limited transmission, the sum of delay-limited throughput (DLT) is maximized subject to a maximum allowable user outage constraint under full CSIT, and the analysis for the sum of DLT is also performed under partial CSIT. Furthermore, an optimal orthogonal multiple access (OMA) scheme is also studied as a benchmark to prove the superiority of NOMA over OMA under full CSIT. Finally, the theoretical analysis is verified by simulations via different tradeoffs for the average sum rate (sum-DLT) versus the minimum (maximum) average user rate (outage) requirement.