Applications like the one illustrated in Fig. 1 require wireless communication with a relatively short range (20-30m). Currently available methods for such short-range communication include wireless LAN, Bluetooth®, Bluetooth® low energy, and ZigBee. In developing a network-linked healthcare device, the ideal method is selected in consideration of a number of factors, including frequency band used, data rate, communication range, power consumption (peak/mean), communication partner, cost and size. In the case of the ring pulse meter, the selection focused on data rate and mean power consumption.
Figure 3 shows a rough comparison between data rate and mean power consumption. Once every 200ms, the prototype ring pulse meter transmits a few bytes of measured data on heart rate and blood oxygen levels. The effective data rate is, therefore, in hundreds of bps. For such data rate levels, Bluetooth® low energy technology has the lowest power requirement. This and other important advantages, such as the possibility of accommodating uses linked with mobile phones, made this technology an ideal choice.