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UBC Theses and Dissertations

Scsh/ni : a MAC protocol for implanted telemetry Virtue, Robert William


Small wireless devices face resource constraints that demand compromises between operational range, longevity and data traffic. Reduced device dimensions significantly impact antenna efficiency and the power capacity of primary cells. When such a device is implanted under the skin of a young animal, additional difficulties arise as a result of the losses and detuning effects of the growing tissues. The species targeted by this research project inhabit an environment characterized by rocky formations and salt water, further hampering radio frequency communications. Physical layer design and Medium Access Control (MAC) protocols must work together to provide adequate performance of the system as a whole. Herein the Single Channel Sharing Hybrid (SCSH) MAC protocol is developed. SCSH provides both range and longevity by exploiting the low data transfer requirements of the application and an environment that allows the use of a Master/Slave star network topology. After a critical review of several possible designs, the SCSH MAC was selected as providing the best system performance while achieving the tag longevity goal of three years, maximizing communications range and minimizing interrogator costs. The SCSH MAC features scalability to handle an arbitrary number of tags, exploits low data rates and reporting frequencies to minimize collisions and provides a mechanism for eliminating redundant transmissions following a collision or otherwise corrupted transmission. The protocol provides the practical illusion of always-on tag operation, allowing for on-demand surveys and mitigation of fading effects while simultaneously ensuring tag longevity goals are met. The Single Channel Sharing Hybrid with Networked Interrogators (SCSH/NI) architecture consists of a self-organizing network of small, inexpensive interrogators that communicate with tags using the SCSH protocol. SCSH/NI interrogators enable coverage of complex geographies and ensure functionality for short-range communications.

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