Reconfigurable intelligent surface (RIS)-empowered communication is a revolutionary technology that enables to manipulate wireless propagation environment via smartly controllable low-cost reflecting surfaces. However, in order to outperform conventional communication systems, an RIS-aided system with solely passive reflection requires an extremely large surface. To meet this challenge, the concept of active RIS, which performs simultaneous amplification and reflection on the incident signal at the expense of additional power consumption, has been recently introduced. In this paper, deploying an active RIS, we propose a novel beamforming concept, over-the-air beamforming, for RIS-aided multi-user multiple-input single-output (MISO) transmission schemes without requiring any pre/post signal processing hardware designs at the transmitter and receiver sides. In the proposed over-the-air beamforming-based transmission scheme, the reflection coefficients of the active RIS elements are customized to maximize the sum-rate gain. To tackle this issue, first, a non-convex quadratically constrained quadratic programming (QCQP) problem is formulated. Then, using semidefinite relaxation (SDR) approach, this optimization problem is converted to a convex feasibility problem, which is efficiently solved using the CVX optimization toolbox. Moreover, taking inspiration from this beamforming technique, a novel high-rate receive index modulation (IM) scheme with a low-complexity sub-optimal detector is developed. Through comprehensive simulation results, the sum-rate and bit error rate (BER) performance of the proposed designs are investigated.
翻译:重新配置智能表面(RIS)的动力通信是一种革命性技术,它能够通过智能控制的低成本反射表面来操纵无线传播环境。然而,为了优于常规通信系统,一个完全被动反射的RIS辅助系统需要一个非常大的表面。为了迎接这一挑战,最近引入了主动的RIS概念,它同时对事件信号进行扩增和反射,而牺牲了额外的电耗。在本文中,部署一个积极的RIS,我们提出了一个新颖的波形组合概念,即超空波形成型,用于RIS辅助的多用户多功能投影单输出(MISO)传输系统,而不需要任何预/后信号处理的反射反射系统。在拟议的超空波成型传输方案中,活动里程元素的反射系数已经定制,以最大增量增益增益。为了解决这个问题,首先,一个非易变形的缩缩缩缩版四面编程(QQP),对于RIS多用户的多投影传输计划来说,使用BIDS 快速的升级方法,然后将S-demodeal develil化为Slate ASyal 。