A predictive ant colony optimization routing protocol for correlated link stability in wireless body area networks

Wireless Body Area Networks (WBANs) are essential for continuous health monitoring but face critical challenges due to dynamic link instability caused by body movements and strict bio-safety requirements. The fluctuating wireless channel leads to high packet loss, while radio frequency (RF) energy absorption, measured as Specific Absorption Rate (SAR), must remain below 1.6 W/kg to prevent tissue damage. Existing routing protocols often react to failures rather than predict them and rarely co-optimize reliability with thermal safety. This paper proposes PACO-CLS (Predictive Ant Colony Optimization with Correlated Link Stability), a novel routing protocol that proactively addresses both network dynamics and bio-safety. It leverages tri-axial accelerometer data from sensor nodes to classify body posture using a Gaussian Mixture Model (GMM). This posture state conditions a Vector Autoregressive (VAR) model, which predicts future link quality metrics (SNR, distance, SAR) over a 0.5-second horizon. These predictions drive an enhanced Ant Colony Optimization (ACO) algorithm, where path selection is guided by a multi-objective cost function. Crucially, the pheromone evaporation rate is dynamically modulated by the cumulative SAR, calculated via the Pennes bio-heat equation, to enforce thermal safety. Extensive simulations in NS-3.40, calibrated with empirical data from the MySignals HW V3 platform, demonstrate that PACO-CLS significantly outperforms QC-TriL, LEACH-WBAN, and Q-Learning-based routing. It achieves a network lifetime of \(32.4 \pm 1.2\) hours (a 40.3% improvement), an energy efficiency of \(17.8 \pm 0.2\) Mb/J, a packet delivery ratio of \(98.5\% \pm 0.3\%\) , and end-to-end latency of \(36.2 \pm 2.1\) ms. Critically, it maintains an average SAR of \(0.82 \pm 0.11\) W/kg, well below the safety threshold across all tested scenarios, including high interference ( \(I_d=0.3\) sources/m 2 ) and mobility ( \(v=1.5\) m/s). By integrating predictive analytics with thermal-aware mechanisms, PACO-CLS establishes a new benchmark for intelligent WBAN routing. Its ability to proactively avoid unstable links based on correlated motion analytics and simultaneously enforce bio-safety constraints makes it a robust and clinically viable solution. PACO-CLS consistently meets stringent clinical requirements for real-time monitoring (PDR \( > \) 95%, \(D_{e2e}\) \( < 50\) ms, SAR \( < 1\) W/kg, \(T_{\text{life}} > 24\) h), demonstrating its potential for next-generation, safe, and reliable healthcare applications.