Implementation and characterization of in-to-out body radio transmissions for a ruminal bolus

• Autores: Lu Wang
• Directores de la Tesis: Carles Ferrer (dir. tes.) , Marta Prim Sabrià (codir. tes.)
• Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2019
• Idioma: español
• Tribunal Calificador de la Tesis: Jordi Aguiló Llobet (presid.) , Maristela Rovai (secret.) , José Carlos Esteves Duarte Pedro (voc.)
• Enlaces
  • Tesis en acceso abierto en: TESEO
• Resumen

  • In recent years, using indwelling wireless sensor nodes to collect and transmit essential bioclimatic data from the reticulo-ruminal chamber is gaining a global recognition in cattle management. Benefits of these devices, usually referred to as ruminal (sensing) boluses, include real-time supervisions of rumen stability, loss prevention, and improved animal welfare. As the major export party of global dairy products, Europe has been pioneering in the research and development of ruminal boluses, mostly working at the license-free industrial, scientific, and medical radio band of 433.05 MHz—434.79 MHz. Meanwhile, the increasing need to apply adequate ruminal boluses to monitor the health status of small ruminants, such as sheep and goats, is bringing new challenges to researchers. In consideration of the much smaller body size compared to cows, a notable downsizing of device form-factor is indispensable. However, this would affect not only the radiation efficiency but also the shelf life of the small ruminal boluses, since both the radio component and the power unit would benefit from abundant space. For devices used in wireless body area networks, power consumption is closely related to system configurations in view of the wireless channel: not only the radiation elements, but also the characteristics of the radio transmission channel. Unfortunately, very few research efforts have been dedicated to the wireless channel of ruminal boluses for small ruminants.

    This doctoral thesis focused on the search of a radio solution for ruminal boluses targeted on small ruminants, which could balance the restrictions in device dimension and performance. This radio solution consists of the implementation of a small antenna that could fit for a compact ruminal bolus working at 433 MHz, and the characterization of the in-to-out body radio transmission channel between a small ruminal bolus and an on-body receiver. A small spiral antenna was devised for integration into a ruminal bolus for small ruminants, taking into consideration of the other encapsulated components and mediums, as well as the in-body environment where the ruminal bolus resides. To investigate the radio link between the spiral antenna and a reference receiver, theoretical path loss models were developed, by means of both laboratory measurement in a tissue-simulating liquid and numerical analysis with 3-dimensional computational electromagnetic tools. Link viability was verified on a system level through link budget analysis, utilizing the theoretical path loss models. Beyond the theoretical channel studies, the actual radio transmission channel also exhibits time-varying features, some of which are aligned with biological behaviors of the ruminant animals. On-site studies were therefore carried out with a rumen-cannulated animal in a barn. Series of in vivo measurement campaigns were arranged to investigate the radio channel’s characteristics in the authentic scenarios. A diurnal path loss pattern was developed through continuous observations based on a prototype of the small bolus and an on-body receiver. Variances of path loss in the radio channel across the day were demonstrated and associated with ruminal digestive statuses. A power-reduction plan was then proposed combining the diurnal path loss pattern to the existing power profile of the small ruminal bolus.