Real time monitoring of electrocardiogram through IEEE802.15.4 network

Real time monitoring of ECG from mobile patients is clinically significant. Physicians can catch the irregular events in the ECG for risk assessment while the patients perform daily tasks without being tethered to an ECG device. The objective of the study was to propose a wireless healthcare network platform based on IEEE 802.15.4 standard which is capable of streaming multichannel ECG signals wirelessly in real time. The study evaluated the performance of the platform for the real time monitoring of ECG signals. The wireless network adopts a star topology with each patient as the end device and the access point as the network center. The access point bridges the wireless network with Ethernet so that the data can be forwarded to the data center. The testing system includes two desktop PCs with XBEE Pro ZB modules, one for ECG acquisition and transmission as the end device and the other for ECG reception and display as the access point. The XBEE module implements the IEEE 802.15.4 standard and ZigBee stack. Only its ZigBee routing protocol was used in this study. The data transmission between the PC and the XBEE module was through serial port. One channel of ECG signal was digitized after being amplified by the ECG amplifier. The ECG was then sent wirelessly through XBEE module to the second PC for real time display. The test software was written in LabVIEW. The LabVIEW driver for XBEE module was developed to provide the interface between the test software and the XBEE module. It provides functions in the control of the XBEE module and serial communication, the management of data frames, and transmission and reception of data frames. The effective transmission time was defined as the time difference between the start of the transmission of a data frame and the reception of the acknowledge frame. The effective data rate was calculated by dividing the number of bits in the data stream by the effective transmission time. The test showed that the effective data rate of the wireless network was above 3.2 kb/s if the data payload was above 60 bytes. The rate enables the reliable streaming of one channel of ECG signal. This data rate was further confirmed by transmitting the high quality ECG signal with no buffer overflow.