X. Liang and I. Balasingham (Norway)
Wireless sensor networks, IEEE 802.15.4, ECG, perfor mance analysis
The integration of biomedical sensors with wireless net work technology may have great potentials in medical ap plications. In this paper, we investigate the use of the IEEE 802.15.4 standard in an ECG monitoring sensor network and study the effects of CSMA/CA mechanism, number of network devices, sampling rates and transmitting cycles. The performance of the network is analyzed in terms of transmission delay, end to end latency, and packet delivery rate. Both biomedical signal sampling time and transmis sion delay contribute to the end to end latency, but the end to end latency is mainly introduced by signal sam pling time, especially for low data rate biomedical sensors. The packet delivery rate increases when the number of pay load data becomes large due to high channel efficiency and packet coding efficiency, but large size packet suffers high end to end latency. In our case study, for a full size MAC packet with maximum payload size (114 bytes), the aver age end to end latency introduced by sampling and trans mitting is about 90 ms. For time-critical applications, a payload size between 40 and 60 bytes can be a good choice, due to lower end to end latency and acceptable packet de livery rate. In the design and deployment of biomedical sensor networks in time-critical medical care applications, trade-off between end to end latency and packet delivery rate must be considered.
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