A Multi-Layer Transmission Paradigm of Augmented Pattern Index Modulation with RIS

To fulfil the requirements of efficient and reliable transmission of ubiquitous information in future networks, we conceive a multi-layer transmission paradigm of augmented pattern index modulation (APIM), which is enabled by reconfigurable intelligent surface (RIS). In the innovating multi-layer RIS-APIM (ML-RIS-APIM), the indices of the transmitting, receiving and RIS reflecting spatial patterns are exploited to convey information, such that multiple data-streams can be delivered highly-efficiently. To meet variant balances between system performance and implementation complexity, we devise two multi-path channel phase alignment based reflections, which are implemented in RIS unit-wise and subset-wise manners, respectively. In terms of receive detection, two algorithms of optimal joint detection and low-complexity decoupling detection, are introduced for acquiring different trade-offs between the achievable error performance and detection complexity. Further-more, upon exploiting the method of moment generating function, a unified analyzing framework is constructed for facilitating the error performance evaluation of the ML-RIS-APIM system. Simulation results verify the correctness of the performance analysis, while reveal the technical superiority of our proposal.

I. Introduction

In recent years, an emerging technology, namely the reconfigurable intelligent surface (RIS), has attracted extensive attentions from both industry and academia. RIS is a electromagnetic reflective plane, which consists of multiple passive reflective elements. In RIS-assisted transmissions, the amplitude and phase of the incident wave can be rectified by RIS via reconfiguring its reflection coefficient through a controller. As a result, the wireless propagation environment can be adjusted, such that the transmission coverage and reliability of communication systems can be remarkably enhanced [1]–[3]. Unlike the conventional relaying techniques, the signal processing involved in RIS reflection does not request the employment of a power amplifier, and does not amplify the effects of noises as well [4].