Patient Temperature Acquisition System Based On Wireless Sensor Network

Wireless sensor networks (Wireless Sensor Networks) is the 21st century most influential and promising technologies. It combines sensor technology, computer information technology, wireless communication technology and distributed information processing technology. Wireless sensor network can sense the physical world, and through the Internet to integrated the physical world with the information world. This paper reviewed a large number relevant literature and introduced the wireless sensor network architecture and features. It analyzed the wireless sensor network localization algorithm and designed a patient body temperature acquisition system based on wireless sensor network.The main research works are as follows:1. Wireless sensor network architecture analysisWireless sensor network that composed of a large number sensor nodes, sink nodes and service platform is a data applications core large network. Sensor nodes mainly use a variety of sensor technology into digital quantities, and with point of miniaturization and low power consumption. It has less data processing and storage capacity, using multi-hop routing protocol to communicate with other nodes, and also process data that come from other nodes. Sink node is first layer data fusion center of wireless sensor network, it has strong data processing capability, storage and communications capabilities and it is the key nodes in the network topology. Service platform is a data center, but also the application center, according to different business needs will have different service platforms. Users can use the platform development and utilization of secondary data, and to be able to configure and manage the entire network.2. Wireless sensor network application analysisWireless sensor network is a new platform for information access; most applications are associated with data applications. In the course of the study need to be distinguished from ordinary network applications, application-driven design methods need to adopt to ensure the system closely integrated with the application. Because of the need to meet the requirements of low cost and low power consumption, the hardware resources of sensor nodes are limited. A huge number of sensor nodes lead to the whole network is a large-scale self-organizing network and ask the network is a dynamic structure and high reliability requirements.Currently, many industries have emerged in the wireless sensor network applications. Medical industry can take advantage of sensor nodes in the physiological parameters of patients, sample collection temperature; positioning technology to the patient, medicine, blood, medical equipment and other location information to measure, reduce medical adverse events. Typical wireless; sensor network applications appear in military battlefield intelligence gathering, environmental change monitoring, wildlife tracking, intelligent transportation, intelligent home and other industries.3. Wireless sensor network architecture and application analysisNetwork topology control, network protocols and security, time synchronization, positioning technology, data integration and management, wireless communications technology, embedded operating system and application layer are the wireless sensor network eight researches. This paper focuses on two main localization technologies in wireless sensor network.AOA algorithm by measuring the signal reaches the point of view, through the triangulation method to calculate the location information of nodes. TOA, TDOA technique requires a precise network time synchronization system. It use RF signal, acoustic or ultrasonic signal propagation time to calculate distance between sending and receiving node, and then use trilateration method or maximum likelihood method to calculate location information. RSSI technique uses radio RF signal strength measurements, and the signal attenuation models to calculate the distance between the nodes, and then use trilateration method or maximum likelihood method to calculate the unknown node location information. Signal measurement, time synchronization mechanism, the signal strength test will require additional hardware, thus leading to the high cost of the node. Signal will be subject to interference noise in the dissemination process.Centroid algorithm and APIT algorithms are used the centroid of polygon as the unknown node position. Centroid algorithm is the use of all the neighbors of anchor nodes of the polygon centroid, APIT algorithm is exhaustive of all the triangle include the unknown node, and then the overlapping area of these triangles centroid as the location of unknown nodes. DV-HOP algorithm is use the average jump distance, and the jump number of unknown nodes to each anchor node to calculate distance, and then use trilateration method or maximum likelihood method to calculate location information. Range-free technology does not require measure the distance between the nodes and additional hardware. In this simulation experiment, anchor node density and node communication radius are the important factor of the algorithm accuracy.4. Patient temperature acquisition system designThis paper has designed a patient body temperature acquisition system based on wireless sensor network, use DS-18B20 temperature sensors measure body temperature, CC2500 RF transceiver and the MSP430 low-power single chip as the control.1) Data Acquisition PlatformDS-18B20 digital temperature sensor is a single bus device, the external circuit is simple, to the temperature within the larger high-resolution temperature measurement. In the process of transferring data can be transmitted CRC, error correction has a very strong anti-interference ability.RF module uses CC2500 RF transceiver chip which is designed for low-power wireless applications design. It is the work of the band for the 2.4GHz, and includes a packet processing, data buffering, burst data transmission, channel assessment, link quality indication and other features and functions of electromagnetic wave excitation. The chip uses a FIFO data transfer mode transmission of data. The parameters of CC2500 can be customized by the user status word.Control module with MSP430F2002 ultra-low power MCU. Receiving node needs to communicate with multiple sensor nodes, and the initial integration of the collected data. Use ARM platform MCU to meet a large number of computing and storage requirements.2) Business Service PlatformCOM can be used in the communication between any two components without regard to whether it's operating environment and the computer. Use this technology to development, reusable modules and developing parallel can be achieved.In the business service platform using layered architecture, including the presentation layer, business layer, data layer and support layer.Presentation layer is deal with the user interface and logic. It main responsibility is to separate the data and performance, communication between the user and the system. It provides users with interactive tools, on the one hand, and submits data for display to achieve certain logic. Basic patient information, node information, body temperature curve are required provide for users.Business layer and business logic of the system is closely related, this layer is the core of platform. In the design of this layer, using object model or domain model design methods to complete the data layer and presentation layer interaction. Patient management, node management, temperature data review, configuration management and logging services are an important component in the business layer module.Data layer has database access, CRUD service, inquiry service, transaction management and concurrent processing. This layer complete data and business object conversion, and isolation between the business layer and database relations. The data store for business service platform includes the temperature data, configuration data and log data.Support layer in the bottom of platform, it is the separation of platform and operating system. Print and record service interface, network communication protocol encoding/decoding, device drivers module are provide by this layer.Conclusions are drawn after tight arguments and prospect for future work is proposed.