关键词: 智能反射表面, 非正交多址, 无线携能通信, 块坐标下降, 连续凸逼近

Abstract:

To address the challenges caused by the rapid development of the Fifth-Generation （5G） mobile Internet of Things （IoT）， including spectrum shortages， coverage blind zones， and power supply deficiencies， by integrating Intelligent Reflecting Surfaces （IRS）， Simultaneous Wireless Information and Power Transfer （SWIPT）， and Non-Orthogonal Multiple Access （NOMA） technologies， a multi-IRS-assisted NOMA-SWIPT cooperative transmission model was proposed. Based on this model， a non-convex optimization problem was formulated with the goal of maximizing system sum rate， and a two-stage joint beamforming （including active beamforming of base stations and passive beamforming of IRS） and power allocation optimization algorithm was then proposed to solve this problem. During the solution process， to decouple the variables to be optimized， a popular optimization method was first used to solve for the passive beamforming in the cooperative transmission phase. Then， the Block Coordinate Descent （BCD） algorithm was applied to decompose the non-convex problem into four sub-problems through alternating iteration， which were later solved using methods such as quadratic transformation and Successive Convex Approximation （SCA）. Simulation results show that compared with schemes of no SWIPT and Orthogonal Multiple Access （OMA）， the proposed cooperative transmission model and its corresponding optimization algorithm improves the system sum rate by approximately 0.5 bit·s^-1·Hz^-1 and 1.5 bit·s^-1·Hz^-1， respectively， and has more robust convergence characteristics.

Key words: Intelligent Reflecting Surfaces (IRS), Non-Orthogonal Multiple Access (NOMA), Simultaneous Wireless Information and Power Transfer (SWIPT), Block Coordinate Descent (BCD), Successive Convex Approximation (SCA)