Redesigning MAC Superframes for Adaptive Priority Handling in IEEE 802.15.7-Based Optical Wireless Sensor Networks

The growing demand for high-priority and delay-sensitive data transmission in Optical Wireless Sensor Networks (OWSNs) exposes considerable deficiencies in the IEEE 802.15.7 MAC superframe, particularly its inadequacy in accommodating various traffic types. This study proposes an enhanced, priority-aware MAC superframe that integrates dual-phase contention and contention-free access with dynamic slot partitioning, a priority beacon system, and opportunistic sleep scheduling. Architectural enhancements comprise the incorporation of a Time-To-Report Contingency (TTRC) interval for urgent data reporting, adaptive GTS allocation prioritizing emergency traffic while maintaining periodic flows, and mini-slot partitioning that expands GTS availability from 7 to 28 allocations per superframe. The proposed strategy accommodates both CSMA/CA and GTS-based transmissions, optimizing channel utilization in mixed traffic scenarios. Comprehensive simulation investigations demonstrate that the IEEE 802.15.7 MAC baseline exhibits up to 68% reduction in end-to-end delay, 55% enhancement in link utilization, and a significant decrease in collision probability under conditions of high-priority traffic. The suggested design utilizes around 22% less power on average compared to the most efficient MAC protocols, demonstrating its energy efficiency and suitability for resource-constrained and time-sensitive OWSN deployments, such as healthcare monitoring and emergency alert systems.