Intelligent Reflecting Surfaces Based Offset Index Modulation for MIMO Systems

In this paper, we introduce the concept of offset to the field of intelligent reflecting surfaces-based index modulation (IRS-IM) and propose an IRS-based offset IM (IRS-OIM) scheme. The IRS-OIM scheme not only divides the IRS elements into several blocks but also introduces an offset at the transmitter while reducing the number of IRS controller operations. Furthermore, we develop three offset IRS block selection (OIBS) approaches to adapt to different numbers of activated IRS blocks for IRS-OIM. Compared with IRS-IM, the IRS-OIM increases the reliability of information transmission and ensures a high effective gain for the IRS while increasing the data transmission rate. In addition, the mathematical expression for the average bit error probability (ABEP) of the IRS-OIM scheme is deduced. Comparison between IRS-OIM and their counterparts in terms of complexity is also provided. Monte Carlo simulation results demonstrate the superiority of the proposed IRS-OIM scheme, and show that IRS-OIM achieves more balanced trade-off among complexity and performance than their counterparts.