Energy efficient UAV-assisted two layer hierarchical bit-mapping access based MAC protocol

Reliable and efficient medium access control (MAC) protocols are crucial for energy-efficient data communication and effective resource utilization in Wireless Sensor Networks (WSNs). In this work, we propose an Energy-Efficient UAV-assisted Two-Layer Hierarchical (EE-UAV-TLH) MAC protocol, designed for mission-critical applications with energy constraints and limited bandwidth. The protocol employs a two-level hierarchical clustering structure, where sensor nodes communicate with their Cluster Head (CH), and the CH coordinates with an Unmanned Aerial Vehicle (UAV) for data collection and transmission scheduling. By adopting a bit-mapping access scheme, EE-UAV-TLH significantly reduces idle listening and control overheads, while the UAV acts as a mobile sink and synchronization controller, enhancing scalability and minimizing energy usage. Simulation results across diverse scenarios demonstrate that the TLH-ETDMA variant consistently outperforms its counterparts (TLH-TDMA and TLH-BMA), yielding average energy savings of about 20% over TLH-TDMA and 34% over TLH-BMA. In peak cases, EE-UAV-TLH achieves up to 31% improvement against TLH-TDMA and up to 52% against TLH-BMA. Even under large-scale deployment with 110 nodes, it sustains 17% and 39% savings, respectively, highlighting its superior efficiency and scalability for UAV-assisted WSNs.