Joint Active And Passive IRS Aided Wireless Communication: Elements Allocation and Achievable Rate

Equipping reflecting elements at the active intelligent reflecting surface (AIRS) enhances signal amplification capability but meanwhile incurs non-negligible amplification noise, which thus challenges the determination of elements allocation for maximizing achievable rate in multi-cooperative AIRS and passive IRS (PIRS) jointly aided wireless communication system. To tackle this issue, we consider the downlink communication from a single-antenna transmitter (Tx) to a single-antenna receiver (Rx), which aided by a pair of AIRS and PIRS with two different deployment orders. Specifically, we target to determine the number of AIRS/PIRS elements over both transmission orders under given deployment budget for the achievable rate maximization. Our analysis illustrates that the PIRS should be allocated more elements than the AIRS for achieving optimized rate and linear signal-to-noise ratio (SNR) scaling orders are attained in both schemes. Simulation results are provided to evaluate the proposed algorithm and compare the rate performance of the AIRS and PIRS jointly aided wireless system with various benchmark systems.

Robust Analysis of Full-Duplex Two-Way Space Shift Keying With RIS Systems

Reconfigurable intelligent surface (RIS)-assisted index modulation system schemes are considered a promising technology for sixth-generation (6G) wireless communication systems, which can enhance various system capabilities such as coverage and reliability. However, obtaining perfect channel state information (CSI) is challenging due to the lack of a radio frequency chain in RIS. In this paper, we investigate the RIS-assisted full-duplex (FD) two-way space shift keying (SSK) system under imperfect CSI, where the signal emissions are augmented by deploying RISs in the vicinity of two FD users. The maximum likelihood detector is utilized to recover the transmit antenna index. With this in mind, we derive closed-form average bit error probability (ABEP) expression based on the Gaussian-Chebyshev quadrature (GCQ) method and provide the upper bound and asymptotic ABEP expressions in the presence of channel estimation errors. To gain more insights, we also derive the outage probability and provide the throughput of the proposed scheme with imperfect CSI. The correctness of the analytical derivation results is confirmed via Monte Carlo simulations. It is demonstrated that increasing the number of elements of RIS can significantly improve the ABEP performance of the FD system over the half-duplex (HD) system. Furthermore, in the high SNR region, the ABEP performance of the FD system is better than that of the HD system.