RIS-Assisted Proactive Handover for Reliable mmWave Wireless Networks

Millimeter-wave (mmWave) wireless networks offer high data rates but are highly susceptible to signal blockages caused by physical obstacles. While Vision-Aided Wireless Communications (VAWC) can predict these blockages to trigger proactive handovers (PHO), a secondary base station is not always available to take over the connection. Reconfigurable Intelligent Surfaces (RIS) serve as a critical alternative to restore connectivity by reflecting signals around obstacles. However, large RIS arrays introduce significant configuration delays and power consumption, which can hinder the real-time requirements of proactive handovers.

This paper introduces a novel RIS-assisted PHO framework that explicitly incorporates RIS configuration time into the handover preparation phase. The authors formulate an optimization problem solved via Particle Swarm Optimization (PSO) to determine the optimal number of RIS elements. By balancing signal processing complexity with link quality, the framework ensures that the RIS can be configured within the narrow time windows required for seamless handover. The optimization is performed offline to bypass latency constraints, allowing for efficient real-time execution.

The study demonstrates that it is possible to optimize the RIS architecture without compromising performance. By reducing the number of allocated RIS elements by 12%, the system achieves a 10% reduction in dissipated energy while maintaining the necessary signal-to-noise ratio (SNR). Furthermore, the RIS-assisted link provides a 15–30 dB improvement in signal strength within blocked regions, successfully meeting the timing constraints required for reliable proactive handover in 6G-envisioned scenarios.