This paper proposes the design and implementation of an intelligent health monitoring system, e-Guardian, which helps the elderly live independently and offers peace of mind to their family members. The heart of the system is a base station (BS) that acts as a gateway between GSM/GPRS and WSN. At seniors’ sides are a number of small and lightweight wearable devices (WDs) which are capable of automatically detecting accidental falls, inferring simple activities of daily livings (ADLs), monitoring body temperatures and heart rates, etc. WDs communicate with BS, possibly via range extenders (REs) in several hops. During an emergency, alert signals will be sent to family members or caregivers via SMS. To avoid network congestions, e-Guardian takes a decentralized approach by processing sensor data locally in WDs instead of streaming raw sensor data to the BS for processing. An interrupt-driven fall detection algorithm using a digital microelectromechanical-system (MEMS) accelerometer has been designed to allow host microcontroller units (MCUs) to process data only upon interrupts and sleep the rest of the time, thus achieving several months of standby time. The system consumes minimum bandwidth thus allows its network to scale easily to cover a large area. The scalability allows an e-Guardian system to be deployed in not only households but also care centers, hospitals and even entire village/community areas thus the cost per senior is further reduced.
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