Implementing secure BLE signal transmission through antenna design techniques in wearable IoT devices

Bluetooth low energy (BLE) is a cornerstone of modern wearable Internet of Things systems, particularly in healthcare and fitness domains. However, its omnidirectional signal propagation introduces substantial physical-layer vulnerabilities, allowing signal leakage and metadata interception even in encrypted environments. This paper proposes a novel cross-layer security framework that integrates antenna design techniques—including directional radiation, impedance tuning, and Specific Absorption Rate-aware placement—with existing BLE software-level protocols. Our design leverages a modified meandered inverted-F antenna structure optimized for wearable scenarios, enabling spatial confinement of BLE signals to reduce eavesdropping risks. Through literature-supported analysis and inferred performance benchmarks, we show that this hybrid approach can reduce effective interception range by up to 40% without compromising BLE throughput or latency. The study lays foundational groundwork for secure-by-design wearable systems that merge physical-layer resilience with protocol-level protection.