Low-rate GPS Coordinate Communication Protocol Embedded into VHF Beacon for Animal Tracking

Traditional animal tracking radio collars employ a low-duty cycle VHF radio beacon for directional antenna-based tracking and collar retrieval. With the advent of compact GPS receivers, an efficient method to transmit GPS coordinates while minimizing weight, power consumption and cost is desired. A protocol is described based on the modulation of the existing VHF beacon to achieve the GPS coordinate communication while meeting the desired metrics. The implementation utilizes the LimeSDR mini interfaced to a Raspberry PI. Discussed within are the communication protocol, algorithm implementation and device field application.