智能反射面增强的全双工环境反向散射通信系统波束成形算法

Beamforming Design for Reconfigurable Intelligent Surface Enhanced Full-duplex Ambient Backscatter Communication Networks

当前传统环境反向散射通信存在双重衰落、障碍物阻挡和网络容量有限的问题。智能反射面(RIS)作为6G的关键候选技术因能够主动改善信号传输质量、提升通信系统传输性能而备受关注。为此,该文将RIS与全双工技术引入到环境反向散射通信系统,研究了考虑硬件损伤与RIS离散相移的RIS增强全双工环境反向散射通信系统波束成形算法。首先,考虑反射节点最小能量收集与服务质量约束、功率站最大发射功率约束和RIS相移约束,建立了总发射功率最小的波束成形优化问题。然后,利用交替优化、半正定松弛、变量替换、半正定规划将原非凸问题转化成可求解的凸优化问题。最后,仿真结果表明,所提算法比传统波束成形方法平均功耗降低了7.8%。

Current conventional ambient backscatter communication suffers from double fading,obstacle blockage,and limited network capacity.Reconfigurable Intelligent Surface(RIS)as a key candidate technology of 6G has been concerned due to the improvement of signal transmission quality and the enhancement of the transmission performance of communication systems.Based on the above advantages,RIS and full-duplex techniques are introduced into the ambient backscatter communication system,and the beamforming algorithm is designed in an RIS-enhanced full-duplex ambient backscatter communication network with hardware impairments and discrete phase-shift constraints.Firstly,a beamforming optimization problem is formulated to minimize the total transmit power by considering the minimum harvested energy and the quality-of-service constraint of the backscatter nodes,the maximum transmit power constraint of the power station,and the phase shift constraint of the RIS.Then,the original non-convex problem is transformed into a tractable convex optimization problem by using alternating optimization methods,semi-definite relaxation methods,variable substitution,and semi-definite programming.Finally,simulation results show that the proposed algorithm decreases the average power consumption by 7.8%compared to the conventional beamforming method.