RIS improves power efficiency in multiuser NOMA networks despite hardware limits
RIS-Assisted Multiuser NOMA Networks With Imperfect CSI Under Transceiver Hardware Impairments
Information Theory
Summary
Wireless networks can send data to many users at once, but hardware issues and imperfect knowledge about the connection can cause problems. The authors study how to reduce the power base stations use while still reaching target data rates by smartly adjusting signals using special surfaces called RIS. They create a method that handles errors from hardware flaws and imperfect information, and show that using multiple signal beams works better than just one. Their approach lowers power use and improves performance compared to methods that ignore these real-world issues.
What this means in practice
- •For wireless network engineers: Design RIS-assisted NOMA systems that minimize transmit power under practical hardware and channel uncertainties to improve energy efficiency.
- •For telecommunications equipment developers: Develop transceivers and control algorithms supporting multi-beam NOMA with hardware impairments and imperfect channel knowledge for better network performance.
Authors
Qian Zhang, Maoyuan Wang, Xuejun Cheng, Yufei Zhao, Guanghui Luo, Shiyao Guo
Abstract
The incorporation of non-orthogonal multiple access (NOMA) and reconfigurable intelligent surface (RIS) provides a new solution to improve spectral efficiency. Unfortunately, the channel estimation error of RIS is noteworthy due to the absent active radio frequency link. Meanwhile, the transceivers at base stations (BS) and users also exist hardware impairments (HWI). The imperfect channel state information (CSI) and HWI will degrade the communication performance such as outage probability or data rate. To alleviate such performance deterioration, we propose a robust design scheme to minimize the BS transmit power when the target rate of users is satisfied in RIS-assisted single-beam and multi-beam NOMA networks with transceiver HWI and imperfect CSI. Further, the perfect successive interference cancellation (SIC) condition in single-beam and multi-beam NOMA networks is investigated, and the optimization problem is proposed based on perfect SIC conditions. To tackle the non-convex problem, we provide an effective algorithm combining Bernstein-type inequality and semi-definite relaxation. Numerical results demonstrate that the proposed scheme outperforms non-robust RIS-assisted NOMA scheme that ignores HWI and imperfect CSI. Moreover, the multi-beam NOMA network obtains higher beam gain compared to the single-beam NOMA network, and thus there is a superior performance in multi-beam NOMA networks.