A novel in vivo 433 MHz radio channel indoor study targeting on power saving for ruminal health monitoring boluses

Abstract

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 rumen-cannulated 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.