Body sensor network
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The term BSN is first coined by Prof Guang-Zhong Yang of Imperial College London in order to bring together scientists from different disciplines such as computing, electronics, bioengineering and medicine. Traditionally existing Wireless Sensor Network (WSN) hardware platforms were modified for BSN applications. However due to limited bandwidth and computational requirement these modified platforms seems to be infeasible for BSN application. In order to facilitate research and development in body sensor network, a BSN hardware platform called BSN node is developed at Imperial College. The BSN node provides a suitable development platform for pervasive health care applications. Various physiological sensors can be integrated into BSN Node.
The rapid technological growth in physiological sensors, low power integrated circuits and wireless communication has enabled a new generation of wireless sensor networks. These wireless sensor networks are suitable for different applications, e.g. traffic monitoring, plant monitoring in agriculture, infrastructure monitoring and health monitoring. However, our work is related to Wireless sensor technology for health monitoring applications called Body Sensor Network. BSN is a rich interdisciplinary area which revolutionizes the health care system by allowing inexpensive, continuous and ambulatory health monitoring with real-time updates of medical records via Internet. A number of intelligent physiological sensors can be integrated into a wearable wireless body area network, which can be used for computer assisted rehabilitation and even early detection of medical conditions.
BSN Development Kit
BSN development Kit consists of two BSN nodes, a USB programmer, one prototype board and one battery board.
Specification of BSN node
The BSN node is based on Texas instrument (TI) MSP430F149 micro controller. The MSP430 processor is a 16 bit ultra low power RISC processor which can operate at minimum of 1.8 V. It consumes 3 mW at active mode and 15 µW at sleep mode. For wireless communication the Chipcon CC2420 is used in BSN node, which has a maximum throughput of 250 kbit/s with a range of 50 m. IEEE 802.15.4 Zigbee wireless link is used as a low power communication protocol. The detailed specification is given below:
• TI MSP430 ultra low power processor
• 16 bits RISC processor
• 64 kB +256 B Flash memory
• 12-bit ADC
• Active Mode: 280 μA at 1 MHz 2.2 V
• Standby Mode: 1.6 μA
• Off Mode: 0.1 μA
• Chipcon CC2420 RF module
• IEEE 802.15.4 (Zigbee) wireless link
• 2.4 GHz
• 250 kbit/s
• Low current consumption (RX:19.7 mA TX:17.4 mA)
• Hardware MAC encryption
• Range 50 m
• 6 analog channels (connect up to 6 sensors)
• 512 kB serial memory
BSN Architectural Design
To provide the necessary function, the following four components are required:
The BSN is designed to have three modules:
BSN Physiological Sensors
Based on the proposed BSN architecture, various physiological sensors such as 3-lead ECG, 2 lead ECG strip and SpO2 sensors have been developed. For example an ECG sensor has been integrated into BSN node which contains a 2 axis accelerometer, a temperature sensor and battery power sensor as well as rechargeable battery. The size of ECG integrated sensor is 3.1 cm x 4.6 cm. This sensor is much smaller than commercially available ECG sensor.. Moreover based on the newly introduced BSN platform, SpO2 sensor has also been developed. Other sensors such as blood pressure sensor, EEG sensor and a PDA for BSN interface are under development..