A Novel In Vivo 433 Mhz Radio Channel Indoor Study Targeting On Power Saving For Ruminal Health Monitoring Boluses

Ruminal indwelling wireless sensor node is a promising device that combines telemetry and biosensing techniques. However, lack of adequate numerical tools and mathematical models to analyze the in-to-out body radio propagation is hindering further development of such devices. In this study, a new approach to investigate the 433 MHz radio propagation channel between a ruminal sensor node and a wearable receiver is proposed. Unlike theoretical channel modeling methods, time-variant features and influences from digestive activities were modeled and examined in this study. A circadian path loss pattern was generated through continuous observation, which illustrated how radio signals from the ruminal sensor node were attenuated with the rumencannulated pilot cow in its normal status in the barn. Link viability across the day was confirmed while the period with excessive link margin was identified. Consequently, a power-reduction plan was proposed which would bring in over a 15% increase in battery life of the ruminal sensing device, which is crucial for long-term indwelling devices. Meanwhile, the methodology and cross-disciplinary approach proposed in this study to investigate the in-to-out body radio propagation loss for ruminal indwelling sensing nodes demonstrated its merit in the discovery of little-known radio channels.