联合RIS子块与接收天线的索引调制方案性能分析

Performance Analysis of Index Modulation Scheme Combining RIS Sub-Blocks and Receiving Antennas

利用大量无源反射器件设计的可重构智能表面(RIS),具有拓展无线通信覆盖范围、降低系统成本/功耗和提升未来通信系统性能的优势;而索引调制(IM),通过激活通信资源的子集可实现信息的隐性传输,有望为无线通信带来更高的频谱效率和能量效率,因此,为进一步提升未来无线通信系统的性能,该论文融合RIS与IM技术,提出一种联合RIS子块与接收天线的IM方案。在该方案中,按照相邻原则,将RIS反射元件分割为若干子块,进而利用RIS子块索引与接收天线索引同时实现附加信息传递,即对待传输比特序列,将其分割为三部分,其中第一部比特被调制为星座符号,第二部分用于指示RIS子块划分,第三部分用于指示接收天线索引;在此基础上,根据最大似然(ML)检测的成对错误概率(PEP)解析形式,分四种情况,从理论上推导出对应的矩母函数(MGF),得到无条件PEP的解析表达式,最后得到该方案ML检测的平均误码率(ABER)性能上界。仿真结果表明,与现有RIS辅助的IM方案相比,无须增加额外频谱资源,所提方案的系统可达速率和系统差错性能方面均具有一定优势;同时,验证了ML检测的ABER上界具备严格一致性。

The reconfigurable intelligent surface(RIS),designed by numerous passive reflective devices,presents the advantages of expanding wireless communication coverage,reducing system costs/power consumption,and improving future communication system performance.Moreover,index modulation(IM)realizes the implicit transmission of information by activating a subset of communication resources,which was expected to provide higher spectral efficiency and energy efficiency for wireless communication.To further improve the performance of future wireless communication systems,this paper thus proposes an IM scheme by combining the RIS and IM technologies.In this scheme,RIS reflec-tion elements are divided into sub-blocks based on the adjacent principle.Additional information is transmitted concur-rently through both the RIS sub-block index and the receiving antenna index.Specifically,transmitted bit sequences are divided into three parts:the first bit is modulated into constellation symbols,the second indicates RIS sub-block divi-sions,and the third denotes the receiving antenna index.Based on the analytical form of paired error probability(PEP)of maximum likelihood(ML)detection,the corresponding moment-generating function was theoretically derived in four cases,and the analytical expression of unconditional PEP was obtained.Finally,the upper bound of the mean bit er-ror rate(ABER)performance of ML detection for this scheme was obtained.Simulation results show that the proposed scheme has advantages in terms of system reachable rate and system error performance compared with the existing RIS assisted IM schemes and verify that the ABER upper bound of ML detection has strict consistency as well.