Software Architecture for High Data Rate Wireless Body Sensor Applications
by Seung-Mok Yoo
For wireless body area sensor networks, the wearable nodes are highly constrained by low power, low cost, and small size while deliverly high throughput and low latency in a multiple access environment. To accomplish these goals, the hardware must be kept simple, and as a result, the traditional abstractions with separate layers of the protocol stack and application must be merged and made as streamlined as possible. This dissertation identifies and removes two bottlenecks with data transfers: one is between the base station and its sensor nodes, and the other is within the sensor node.
First, we propose a thin-server, fat-client architecture. It supports a pulling protocol that achieves intra-network collision-free multiple access as in TDMA but without the time synchronization overhead. It also achieves high data throughput of air bandwidth and adaptivity of CSMA protocols but without collision or complexity on the node side.
Second, for intra-node transfers, another known bottleneck is the system bus. We identify the double-transaction problem, which is common to SPI, DMA, and other interfaces. We propose the Master-Handoff Protocol to eliminate the redundant transaction and improve latency significantly, and it is compatible with existing controllers. It not only halves the data transfer time but also achieves energy reduction. Together, these techniques enable highly constrained hardware to meet strict size and power constraints for high wearability without sacrificing performance.