Title | STAR-IOS Aided NOMA Networks: Channel Model Approximation and Performance Analysis |
Authors | Zhang, Chao Yi, Wenqiang Liu, Yuanwei Ding, Zhiguo Song, Lingyang |
Affiliation | Queen Mary Univ London, Sch Elect Engn & Comp Sci, London E1 4NS, England Univ Manchester, Sch Elect & Elect Engn, Manchester M13 9PL, Lancs, England Peking Univ, Dept Elect, Beijing 100871, Peoples R China |
Keywords | RECONFIGURABLE INTELLIGENT SURFACES |
Issue Date | Sep-2022 |
Publisher | IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS |
Abstract | Compared with the conventional reconfigurable intelligent surfaces (RIS), simultaneous transmitting and reflecting intelligent omini-surfaces (STAR-IOSs) are able to achieve 360 degrees coverage "smart radio environments". By splitting the energy or altering the active number of STAR-IOS elements, STAR-IOSs provide high flexibility of successive interference cancellation (SIC) orders for non-orthogonal multiple access (NOMA) systems. Based on the aforementioned advantages, this paper investigates a STAR-IOS-aided downlink NOMA network with randomly deployed users. We first propose three tractable channel models for different application scenarios, namely the central limit model, the curve fitting model, and the M-fold convolution model. More specifically, the central limit model fits the scenarios with large-size STAR-IOSs while the curve fitting model is extended to evaluate multi-cell networks. However, these two models cannot obtain accurate diversity orders. Hence, we figure out the M-fold convolution model to derive accurate diversity orders. We consider three protocols for STAR-IOSs, namely, the energy splitting (ES) protocol, the time switching (TS) protocol, and the mode switching (MS) protocol. Based on the ES protocol, we derive closed-form analytical expressions of outage probabilities for the paired NOMA users by the central limit model and the curve fitting model. Based on three STAR-IOS protocols, we derive the diversity gains of NOMA users by the M-fold convolution model. The analytical results reveal that the diversity gain of NOMA users is equal to the active number of STAR-IOS elements. Numerical results indicate that 1) in high signal-to-noise ratio regions, the central limit model performs as an upper bound of the simulation results, while a lower bound is obtained by the curve fitting model; 2) the TS protocol has the best performance but requesting more time blocks than other protocols; 3) the ES protocol outperforms the MS protocol as the ES protocol has higher diversity gains. |
URI | http://hdl.handle.net/20.500.11897/654392 |
ISSN | 1536-1276 |
DOI | 10.1109/TWC.2022.3152703 |
Indexed | SCI(E) |
Appears in Collections: | 电子学院 |