Practical comparison of ranging in IEEE 802.15.4 and IEEE 802.15.4a medical body sensor networks

In this paper, a practical comparison of the wireless standards IEEE 802.15.4 and IEEE 802.15.4a is described. Particularly the ranging capabilities of both systems are studied, with the aim of enabling a senior health monitoring application to automatically detect with which user sensors are associated. The relevant characteristics of both systems are presented, as well as the difference between received signal strength and time of arrival based ranging methods. Next, a measurement campaign based on a TI 802.15.4/Zigbee chipset and IMEC's 802.15.4a demonstrator is presented. Results show that the received signal strength is too heavily influenced by other parameters to use it as a metric for accurate distance estimation. IEEE 802.15.4a based time of arrival methods are far more accurate. Particularly leading edge detection performs well, with an average error in line-of-sight conditions below 6 cm.

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