Wireless personal area networks have emerged as an important communication infrastructure in areas such as at-home healthcare and home automation, independent living and assistive technology. Initiatives towards interoperability and standardization are taken by several players. Zigbee Alliance has launched a profile for “Zigbee wireless sensor applications for health, wellness and fitness” [1]. The Continua Health Alliance promotes “an interoperable personal healthcare ecosystem”. They have published “design guidelines for the telehealth ecosystem” including the interface to personal area network health devices and electronic health record devices ([2], [3]). These examples show that wireless personal area networks, including body sensor networks, are becoming more mature and are considered to be a realistic alternative as communication infrastructure for demanding services. However, to transmit vital sign parameters from ECGs, pulse-oximeters, EEGs etc in wireless networks is also a challenge, especially if multiple sensors compete for access. Contention-based access networks offer simplicity and utilization advantages, but the drawback is unpredictable performance due to loss of transmitted packets.

We have used the SHIMMER wireless sensor platform developed at Intel [4] in the living lab at the Centre for Health and Building at KTH in a case study to identify and evaluate performance problems. The full-scale living lab consists of two apartments especially equipped with modern technique for healthcare at home and assisted living.

Our paper focuses on continuous monitoring of the heart activity using a wireless ECG based on the wireless personal area network (WPAN) standard IEEE 802.15.4. Results from performance tests in the living lab will be presented e.g. influence of equipment such as micro wave ovens. Since contention-based wireless access has no guarantees for the quality of the delivered service it is interesting to determine to what extent the received ECG signal is sensitive to loss of information. We have recorded ECG signals as well as emulated packet loss in existing ECG records from official databases. The result of two cardiologists´ assessment of ECGs with different loss ratio levels and patterns will be reported in the paper. One interesting conclusion is that a diagnosis is fully possible for ECGs with packet loss ratio up to at least 5%. This project is part of research at the School of Technology and Health at KTH.