Abstract
Large intelligent surface (LIS)-assisted wireless communications have drawn attention worldwide. With the use of low-cost LIS on building walls, signals can be reflected by the LIS and sent out along desired directions by controlling its phases, thereby providing supplementary links for wireless communication systems. In this paper, we evaluate the performance of an LIS-assisted large-scale antenna system by formulating a tight upper bound of the ergodic spectral efficiency and investigate the effect of the phase shifts on the ergodic spectral efficiency in different propagation scenarios. In particular, we propose an optimal phase shift design based on the upper bound of the ergodic spectral efficiency and statistical channel state information. Furthermore, we derive the requirement on the quantization bits of the LIS to promise an acceptable spectral efficiency degradation. Numerical results show that using the proposed phase shift design can achieve the maximum ergodic spectral efficiency, and a 2-bit quantizer is sufficient to ensure spectral efficiency degradation of no more than 1 bit/s/Hz.
Highlights
As a key feature of the fifth-generation (5G) and future mobile communications, large-scale antenna systems can produce high throughput by utilizing the spatial degrees of freedom and achieve wide cell coverage with a high-gain array
We first obtain an upper bound of the ergodic spectral efficiency of the Large intelligent surface (LIS)-assisted large-scale antenna system when the LIS assistant link is under Rician fading condition
We examine the tightness of the upper bound of the ergodic spectral efficiency and evaluate the optimal phase shift design for the LIS-assisted large-scale antenna system
Summary
As a key feature of the fifth-generation (5G) and future mobile communications, large-scale antenna systems can produce high throughput by utilizing the spatial degrees of freedom and achieve wide cell coverage with a high-gain array. Hindrances still occur in a largescale antenna system due to the existence of buildings, trees, cars, and even humans. To address this problem and produce fluent user experience, a typical solution is to add new supplementary links to maintain the communication link. Relay nodes can be introduced in areas with poor communication signal to receive the weak signals; the signals are amplified and retransmitted to the relay hop or terminal [1].
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