Interplay Between Reconfigurable Intelligent Surfaces and Spatial Modulation: New Application Paradigms

Abstract

In this paper, a novel amplitude phase shift keying (APSK) modulation scheme for cooperative backscatter communications aided by a reconfigurable intelligent surface (RIS-CBC) is presented, according to which the RIS is configured to modulate backscatter information onto unmodulated or PSKmodulated signals impinging on its surface via APSK. We consider both passive and active RISs, with the latter including an amplification unit at each reflecting element. In the passive (resp. active) RIS-CBC-APSK, backscatter information is conveyed through the number of RIS reflecting elements being on the ON state (resp. active mode) and their phase shift values. By using the optimal APSK constellation to ensure that reflected signals from the RIS undergo APSK modulation, a bit-mapping mechanism is presented. Assuming maximum-likelihood detection, we also present closed-form upper bounds for the symbol error rate (SER) performance for both passive and active RIS-CBC-APSK schemes over Rician fading channels. In addition, we devise a low-complexity detector that can achieve flexible trade-offs between performance and complexity. Finally, we extend RIS-CBC-APSK to multiple-input single-output scenarios and present an alternating optimization approach for the joint design of transmit beamforming and RIS reflection. Our extensive simulation results on the SER performance corroborate our conducted performance analysis and showcase the superiority of the proposed RIS-CBC-APSK schemes over the state-of-the-art RIS-CBC benchmarks.

Performance Analysis of RIS-Aided Double Spatial Scattering Modulation for mmWave MIMO Systems

“…From RIS-assisted transmit and receive SM perspectives, [27] investigated the formation of an optimization problem by minimizing the symbol error rate, which is addressed by adopting the penalty-alternative method. By taking advantage of the information carrying capacity of SM and the reconfigurability of RIS to the environment, [28] studied the potential applications of RIS-SM in relay networks, wireless sensing, and cognitive radio. Besides, the framework of RIS-assisted SM-based ambient backscattering communication was presented in [29], where the tag device can implement ambient backscattering to harness the energy of RF waves in the environment as well as SM techniques.…”

Capacity Enhancement for Multiple Reconfigurable Intelligent Surface based Index Modulation

“…A study that resembles MRIS using IM concept was proposed in [7], where the on-off status of an MRIS was applied using convex optimization in order to advance the energy efficiency of the system. Furthermore, the IM technique in MRIS in [8] also studied to apply the inphase and quadrature branches. However, those studies did not consider about using generated bits for the MRIS activations and how the capacity can be improved by calculating the combination of RIS.…”

Biased-Power Allocation and Shared-Antenna Selection Techniques for Spatial Modulation-Based Layer Division Multiplexing Systems

“…SM is a state-of-the-art multiple-input multiple-output (MIMO) antenna technology that was designed to address issues with traditional MIMO systems, including spatial multiplexing and space-time coding. It is worthwhile to point out that the SM concept has been extended to an index modulation and implemented into a wide range of technologies [18][19][20]. In SM [21,22], only one antenna is active at a time, which simplifies the hardware and reduces the amount of power generated by the radio frequency (RF) chains.…”