Robust Multiuser Beamforming for IRS-Enhanced Near-Space Downlink Communications Coexisting With Satellite System
Robust Multiuser Beamforming for IRS-Enhanced Near-Space Downlink Communications Coexisting With Satellite System
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DOI：
10.1109/jiot.2021.3112595
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发表时间：
2022-08
影响因子：
10.6
通讯作者：
Sai Xu;Jiajia Liu;Tiago Koketsu Rodrigues;N. Kato
中科院分区：
文献类型：
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作者：
Sai Xu;Jiajia Liu;Tiago Koketsu Rodrigues;N. Kato
据我们所知，这篇文章代表了第一次尝试走向强大的波束成形设计的多用户下行链路通信的智能反射面（IRS）增强卫星（SAT）和高空平台（HAP）集成网络。这种网络配置主要由单天线SAT、多天线HAP、多个单天线SAT和HAP终端以及IRS组成。虽然HAP与SAT共享相同的频谱资源，但悬挂在近空间的HAP旨在提供比SAT更高速度和更低延迟的临时多用户通信连接。因此，功率预算应在HAP处仔细调整。为此，我们首先正式制定的信号干扰加噪声比中断概率（SINR-OP）的约束下，在每个SAT和HAP终端的HAP的发射功率最小化问题，考虑到不完美的信道状态信息和高斯信道估计误差。注意，直接SAT/HAP链路和级联IRS链路的复杂叠加使得优化问题相当具有挑战性。具体来说，我们转换成近似确定性的概率约束，通过执行秩松弛。在此基础上，我们能够通过交替优化两个确保子问题来解决优化问题。通过大量的仿真结果验证，所提出的IRS增强的波束成形方案可以大大减少在HAP的发射功率相比，没有IRS的波束成形同行。
To the best of our knowledge, this article represents the first attempt toward robust beamforming design for multiuser downlink communications in intelligent reflecting surface (IRS)-enhanced satellite (SAT) and high altitude platform (HAP) integrated network. Such network configuration is mainly composed of a single-antenna SAT, a multiple-antenna HAP, multiple single-antenna SAT and HAP terminals and an IRS. Although sharing the same spectrum resource with the SAT, the HAP suspended in the near-space intends to offer temporary higher-speed and lower-delay multiuser communication connections than the SAT. Therefore, the power budget should be carefully tuned at the HAP. Toward this end, we first formally formulate the transmit power minimization problem at the HAP under the constraints of signal-to-interference-plus-noise-ratio-outage-probability (SINR-OP) at each SAT and HAP terminal by taking into account the imperfect channel state informations and their Gaussian channel estimation errors. Note that the complicated superposition of direct SAT/HAP links and cascaded IRS links, makes the optimization problem rather challenging. Specifically, we transform the probabilistic constraints into approximate deterministic ones, by performing rank relaxation. Based on this, we are able to solve the optimization problem by alternately optimizing the two ensuring subproblems. As verified by extensive simulation results, the proposed IRS-enhanced beamforming schemes can substantially diminish the transmit power at the HAP compared to the beamforming counterparts without IRS.