Capacity Analysis of RIS-Aided Backscatter Communication Systems

This paper analyzes the performance of a reconfigurable intelligent surface (RIS)-assisted monostatic backscatter communication system. The system under consideration consists of a reader, a distant tag, and an RIS. The reader sends radio frequency (RF) signal in forward phase to read the information from the distant tag via RIS and the tag reflects the signal with information in backscatter phase back to the reader via same RIS. It is assumed that the channel gains of forward and backscatter links follow Rayleigh distribution. Average achievable rate is computed for the system by deriving the closed-form expressions of its upper and lower bounds. To gain deeper insights, asymptotic expressions of these bounds are also derived in closed-form. With the help of numerical results, the effect of various parameters on rate performance is presented. Simulation results confirm the bounds tightness of the average achievable rate. The impact of the RIS position on the rate performance is also analyzed.