An ALOHA-based wireless transmission of physiological signals

The physiological signals such as electrocardiogram, respiration, blood pressure, etc. can reveal the spontaneous status of human physiology, but this benefit is usually degraded by wire connection between the recording sites and the processing unit. Several multi-user communication protocols such as Bluetooth, IEEE 802.11 etc. have been widely used in personal wireless communication. However, the power consumption reduces the time duration of long-term monitoring and the complex protocol requires a complicated microprocessor to handle the communication packets. In this paper, we developed a slotted-ALOHA communication protocol to allow several physiological signals to be transmitted simultaneously in a single communication channel. The protocol is so simple that it can be implemented in a small-size and low-power microcontroller. Furthermore, a 2.4-GHz RF transceiver (nRF2401, NORDIC) was incorporated into a 16-bit microcontroller (MSP430, Texas Instruments). The slotted-ALOHA communication protocol was implemented in the developed system. The result demonstrated the feasibility of the proposed communication protocol.