Simultaneous Transmission and Reflection in Wireless Communication Networks

Simultaneous transmission and reflection in wireless communication networks refers to a class of reconfigurable intelligent surfaces (RIS) capable of manipulating incident electromagnetic waves so that a proportion of energy is transmitted through the surface while the remainder is reflected. This dual-functionality extends the coverage of conventional reflecting-only surfaces, enabling full-space signal propagation and enhanced degrees of freedom for beam steering and interference management. The underlying hardware integrates tunable meta-elements whose amplitude and phase responses can be controlled independently to fulfil diverse communication objectives. Channel models for these surfaces account for both refracted and reflected paths, often under composite fading and line-of-sight conditions, and signal models incorporate protocols for time, energy or mode splitting to regulate the allocation of incident power. By offering simultaneous connectivity to users on both sides of the surface, the technology promises improvements in spectral efficiency, energy efficiency and coverage uniformity. Applications span vehicular networks, device-to-device systems, non-orthogonal multiple access schemes and ultra-reliable low-latency communications, underpinned by optimisation of beamforming patterns, energy-splitting ratios and resource allocation algorithms. The global significance of this paradigm lies in its potential to support high-density deployments, to alleviate blockage issues in millimetre-wave bands and to enable greener 6G infrastructures with reduced power amplification requirements.

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Simultaneous Transmission and Reflection in Wireless Communication Networks publication trend

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Technical terms

Reconfigurable intelligent surface (RIS): A planar array of meta-elements whose response to impinging waves can be electronically tuned to control reflection, refraction or absorption.

Simultaneously transmitting and reflecting RIS (STAR-RIS): A dual-function RIS that splits incident energy into transmitted and reflected components, enabling full-space coverage.

Non-orthogonal multiple access (NOMA): A multiple-access technique where users share the same time-frequency resources, differentiated by power allocation and successive interference cancellation.

Outage probability: The probability that the instantaneous signal-to-noise ratio falls below a predefined threshold, leading to a communication failure.

Ergodic capacity: The long-term average achievable data rate of a channel under time-varying conditions.

Beamforming: The process of optimally weighting the amplitude and phase of signals across an array of elements to steer energy towards intended receivers.

Energy-splitting protocol: A mechanism to allocate a portion of incident signal energy for transmission while reflecting the remainder, controlled by a splitting coefficient.

References

1. Performance Analysis of RIS/STAR-IOS-Aided V2V NOMA/OMA Communications Over Composite Fading Channels. IEEE Transactions on Intelligent Vehicles (2023).
2. STAR-RIS Aided NOMA in Multicell Networks: A General Analytical Framework With Gamma Distributed Channel Modeling. IEEE Transactions on Communications (2022).
3. Simultaneously transmitting and reflecting (STAR) RISs for 6G: fundamentals, recent advances, and future directions. Frontiers of Information Technology & Electronic Engineering (2023).