Intelligent Surface Optimization in Terahertz under Two Manifestations of Molecular Re-radiation
Intelligent Surface Optimization in Terahertz under Two Manifestations of Molecular Re-radiation
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DOI：
10.1109/globecom46510.2021.9685349
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
Anish Pradhan;J. K. Devineni;Harpreet S. Dhillon;A. Molisch
中科院分区：
文献类型：
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作者：
Anish Pradhan;J. K. Devineni;Harpreet S. Dhillon;A. Molisch
太赫兹(THz)通信的运行会受到传输的波与大气中分子之间的相互作用的显著影响。特别是，实验观察到，该信号不仅经历分子吸收，而且还经历分子再辐射。文献中普遍存在两种极端的建模假设，在第一种假设中，重新辐射的能量被建模为加性高斯噪声，在第二种假设中，被建模为与实际信号强烈相关的散射分量。由于精确的表征仍然是一个悬而未决的问题，本文首次对可重构智能表面(RIS)辅助的太赫兹系统在这两种极端再辐射模型下的性能进行了比较研究。特别是，我们使用RIS来通过创建虚拟视线(LOS)路径来克服大的路径损耗。然后，我们为该设置开发了优化框架，并利用块坐标下降(BCD)方法迭代地优化RIS配置向量和接收波束形成权重，从而与随机RIS配置相比，为感兴趣的用户带来显著的吞吐量收益。我们的结果表明，在分子再辐射的散射假设下，吞吐量比在噪声假设下略有提高。
The operation of Terahertz (THz) communication can be significantly impacted by the interaction between the transmitted wave and the molecules in the atmosphere. In particular, it has been observed experimentally that the signal undergoes not only molecular absorption, but also molecular re-radiation. Two extreme modeling assumptions are prevalent in the literature, where the re-radiated energy is modeled in the first as additive Gaussian noise and in the second as a scattered component strongly correlated to the actual signal. Since the exact characterization is still an open problem, we provide in this paper the first comparative study of the performance of a reconfigurable intelligent surface (RIS) assisted THz system under these two extreme models of re-radiation. In particular, we employ an RIS to overcome the large pathloss by creating a virtual line-of-sight (LOS) path. We then develop an optimization framework for this setup and utilize the block-coordinate descent (BCD) method to iteratively optimize both RIS configuration vector and receive beamforming weight resulting in significant throughput gains for the user of interest compared to random RIS configurations. Our results reveal that a slightly better throughput is achieved under the scattering assumption for the molecular re-radiation than the noise assumption.