Joint Beamforming and Phase Shift Design in Downlink UAV Networks with IRS-Assisted NOMA
Joint Beamforming and Phase Shift Design in Downlink UAV Networks with IRS-Assisted NOMA
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DOI：
10.23919/jcin.2020.9130430
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发表时间：
2020-06
期刊：
影响因子：
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通讯作者：
Shiyu Jiao;Fang Fang-Fang;Xiaotian Zhou;Haixia Zhang
中科院分区：
文献类型：
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作者：
Shiyu Jiao;Fang Fang-Fang;Xiaotian Zhou;Haixia Zhang
研究了一种基于智能反射面(IRS)的无人机辅助多输入单输出非正交多址(NOMA)下行链路网络的简单设计。本文的目的是在保证优化的无人机水平位置所给出的弱用户的目标速率的同时，最大化强用户的速率。我们首先对IRS-无人机的位置进行了优化。然后，我们提出了一种迭代算法来交替优化IRS的发射波束形成和相移。对于波束赋形优化，推导了最优波束赋形矢量的闭合表达式。然后，根据所得到的波束形成结果，提出了两种获得IRS最优相移的方法。一种是基于半定松弛的迭代算法，具有较高的数据率；另一种是基于逐次凸逼近技术，具有较低的复杂度。仿真结果表明，这两种算法的性能明显优于随机相移场景和基于IRS的无人机辅助正交频分多址方案。
This paper investigates a simple design of intelligent reflecting surface (IRS) based unmanned aerial vehicles (UAV) assisted multiple-input single-output nonorthogonal multiple access (NOMA) downlink network. The aim of this paper is to maximize the rate of the strong user while guaranteeing the target rate of the weak user given by the optimized UAV horizontal position. We first optimize the location of IRS-UAV. Then we propose an iterative algorithm to optimize the transmit beamforming and phase shift of IRS alternatively. For the beamforming optimization, the closed-form expressions of the optimal beamforming vectors are derived. Then, given by the obtained beamforming, we propose two methods to obtain the optimal phase shifting of IRS. One is the semidefinite relaxation based iteration algorithm which provides high data rate and the other one is based on successive convex approximation technique which has low complexity. Finally, simulation results are provided to show that the performance of the two proposed algorithms are significantly better than using random phase shifting scenario and IRS based UAV-assisted orthogonal frequency-division multiple access scheme.