UWB-based wireless sensor network with medical application
Sammanfattning: This master thesis aims to develop a prototype of a wireless sensor network (WSN) using ultra wideband (UWB) radio and communication. The WSN consists of five sensor nodes and one sink which is connected to an Android smartphone. The smartphone acts as a sensor data management unit and has the ability to display sensor measurements. The sensor nodes include the sensors of an inertial measurement unit, an electrocardiogram (ECG) electrode set, a temperature sensor, a humidity sensor, and three ultrasonic sensors, and they are responsible for making measurements, sending the measurements to, and forwarding the measurements from other sensor nodes to the destination. The sink node receives the measurements from the sensor nodes, and the measurements are displayed on the smartphone. The sensor nodes and the sink are equipped with DecaWave's DWM1000 UWB transceiver which is compliant with the IEEE 802.15.4-2011 communication standard and enables the UWB communications, and a microcontroller, ATmega328, that handles sensor data reading and transmission. Due to UWB pulses having high time resolution, a location-based routing protocol based on time of flight distance estimates is implemented. A prototype of a UWB-based WSN has been developed, tested and evaluated. The resulting prototype can operate in a peer-to-peer topology with multi-hop capabilities. The results of the evaluation show that lower data rate, lower center frequency and wider bandwidth increases radio range and a longer preamble sequence increases ranging accuracy. This comes at the cost of increased time of channel occupation and power consumption. From this thesis project it is indicated that UWB radio is a good choice for short-distance radio communication applications such as WSNs. The measurement errors in range estimates can be within 10 cm in line-of-sight. Networks compliant with the IEEE 802.15.4-2011 communication standard should have low throughput requirements as channel access mechanisms and functions related to reliable data transfers introduce latency.
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