A wireless sensor network is a network composed of a large number of sensor nodes using wireless self-organization, and its application has a broad prospect [ ][ ] Zigbee technology is a short-range wireless communication technology with a unified technical standard, and its PHY and MAC layer protocols are based on the IEEE ． The PHY and MAC layer protocols are based on the IEEE. Due to the shortage of medical resources in China, the study of public network-based home medical monitoring and the establishment of a community medical network can improve the level of medical services and reduce the burden on patients The previous solution was to use wired or simple wireless data transmission and reception The sensing devices installed on the monitored person are difficult to move freely and flexibly and access to the system There is no scalability The cost is high The emergence of Zigbee technology provides a new solution for the wireless transmission of sensor signals. Zigbee technology provides a new solution for the wireless transmission of sensor signals Zigbee nodes have a coverage range of tens of meters and can be added to the routing node to extend the coverage area, so it is suitable for residential homes At the same time, due to the physiological monitoring of the signal data transmission traffic is not large transmission rate of kbps Zigbee can meet the requirements of the physiological data transmission Zigbee sensing nodes can be free and flexible to join and leave the network has a low-power and low-cost characteristics. Low power consumption and low cost
The above characteristics of Zigbee wireless sensor network make it have a very good prospect of application in personal physiological signal monitoring and remote home monitoring In this paper, based on the analysis of Zigbee wireless sensor network technology, we have conducted a research on its application in mobile monitoring
Architecture of Zigbee-based wireless network home monitoring system
The architecture of the wireless network home monitoring system is based on Zigbee. The requirements of remote home monitoring system on the network
Home monitoring network needs to consider the energy consumption, coverage, transmission rate and the Internet for communication, etc. This study adopts the wireless network based on Zigbee technology to realize the collection of physiological signals indoors and transmit physiological data through the Internet to the remote monitoring server The human body carries a mobile physiological signal sensor terminal within the coverage area of the network. The human body carries a movable physiological signal sensor terminal within the coverage area of the network, and accesses the Internet through the routing nodes in the network. Zigbee network has the characteristics of self-organization, dynamic routing, fewer nodes, etc. At the same time, the Zigbee network takes into account the energy saving of the nodes, and reduces the computational burden of the node processors, etc. Doctors in hospitals or communities can check the physiological information of the patients at any time through the Internet, and they can control the physiological sensors' acquisition methods. The information of other monitoring devices in the wireless network can be obtained
． Network Topology
IEEE.
There are three network topologies for the IEEE． There are three types of network topologies for the IEEE.0 protocol: star, mesh, and family. The mesh and clustered structures are point-to-point structures, as shown in Figure
There are three types of network topologies for the IEEE． In the network, the mesh and the family are point-to-point structures. According to the communication capability of the devices, they can be categorized into full-function devices (FFDs) and reduced-function devices (fIFDs). FFDs can communicate directly with each other as well as between FFBs and RFDs, and RFDs cannot communicate directly with each other. + In IEEE 802.11.1, there is an FFD device called a PAN network coordinator that is the master controller in a sensor network. The central node consumes a lot of energy and is suitable for a small number of nodes, a simple network structure, and a small range of network applications, whereas in a point-to-point network, any two devices can communicate with each other as long as they are both within their radius of the network. Network structure
In the home monitoring system, the object of monitoring may be active in multiple rooms, in order to expand the coverage at any time, and to facilitate the future expansion of the function of the family network topology is selected In the connection with the Internet, the establishment of ziHalee wireless network and the Ethernet bridge will be transmitted to the monitoring server to realize the monitoring information **** enjoy
Home monitoring network architecture
Home Monitoring Network Architecture
Based on the above analysis, the remote home monitoring network architecture designed in this paper is shown in Fig. The Zigbee wireless system is mainly composed of Zigbee wireless sensor nodes (pulse sensor nodes), a number of wireless nodes with routing functions, and the zigbee central network coordinator (connected to the home wireless network bridge), which is connected to the zigbee wireless network and Ethernet. The wireless bridge connects the zigbee wireless network to the Ethernet network, and is the core of the home wireless network, responsible for the management of the wireless sensor network nodes and device nodes. Since the monitored person moves freely in the home, the routing of the sensor nodes he carries may change dynamically The designed Zigbee wireless nodes have an indoor communication distance of ～ m The A B C D nodes can be arranged according to the distribution of the rooms so as to maximize the coverage of the active area Pulse physiological data is transmitted to the remote monitoring server through the home gateway The remote monitoring server is responsible for real-time collection of pulse physiological data, displaying and storing other monitoring information such as monitoring images, security devices, status and security devices, and other information such as monitoring images. Other monitoring information such as monitoring images, safety equipment status, etc. can also be transmitted to the server. The hospital monitoring center and doctors can log in to the monitoring server to view the physiological information of the monitored person. The hospital monitoring center and doctors can log into the monitoring server to view the physiological information of the monitored person, and can also remotely control the sensors and devices in the home Zigbee wireless network, so that when the monitored patient has an abnormality, it can be detected in a timely manner and rescue measures can be taken, and the relatives of the monitored person can log into the monitoring server to keep abreast of the monitored person's state of health.
Hardware structure of Zigbee home wireless network monitoring system
The sensor nodes need to be small, low-power, and adaptable. According to the Zigbee protocol standard, the transmit output of Zigbee devices is ~ ? dbm. dbm communication distance is ~ m can detect the energy and link quality according to these detection results can automatically adjust the device's transmit power in order to ensure the quality of the communication link under the condition of minimizing the consumption of energy equipment Currently on the market of wireless transmitter-receiver chip typical Chipcon and Freeseale products In this paper, we choose Freescale's as the system of radio frequency chip This chip can be combined with Freescale's RF chip, which can be used in a variety of different ways, such as the use of a single chip, a single chip, and a single chip. This chip can be combined with Freescale's controller GT to form a low-power wireless module. The block diagram of the wireless sensor node is shown in Figure
? Because the wireless sensor has the requirement of portable, so the use of button batteries pulse sensor using PVDF piezoelectric film whose output impedance is very large by the conditioning circuit to achieve the signal amplification and filtering design to take into account the high-frequency circuit on the sensor signal interference sensor conditioning circuit and high-frequency transmitter-receiver part of the design of a separate antenna design is the key to the design of the wireless module, which directly affects the sensor nodes of the quality and communication distance can be referred to the commonly used. The antenna design is the key to the wireless module design, which directly affects the communication quality and distance of the sensor nodes. GHz antenna design method This design adopts dipole microstrip PCB antenna all copper foil alignment are used microstrip transmission line principle to reduce the reflection caused by the transmission loss to obtain a larger output power and higher receiving sensitivity
Home gateway is responsible for the control and management of the home wireless sensor network to achieve the fusion of the information processing and the transmission of the information to the Internet Home gateway data transmission and computing capacity is large and can be used to transmit and receive the information to the Internet, and can also be used in a variety of other ways. The home gateway has a large amount of data transmission and computing and can use external power as a power supply, so the use of strong information processing capabilities and network functions of the arm series as the controller In this paper, we use Samsung's S C as the controller, the wireless transmitter chip Freeseale's MCl wireless controller chip GT The two communicate with each other through the SPI port The hardware structure of the wireless gateway is shown in Figure
The Zigbee wireless network software system is used to control the home wireless sensor network and realize the fusion of information processing and transmission of information to the Internet. Zigbee wireless network software system
Zigbee protocol stack consists of a series of layered structure Each layer provides services for the upper layer Data entity provides data transmission services Management entity provides other functional services Each service entity provides interfaces for the upper layer through the service access point (CsAP) Based on the Zigtme network software layered structure as shown in Figure
The PHY and MAC layers are defined by the IEEE . The PHY and MAC layers are defined by the IEEE． Physical layer defines the interface between the physical radio channel and the MAC sublayer Provides physical layer data services and physical layer management services Physical layer data services send and receive data from the radio channel Physical management layer maintains a database of data related to the physical layer
The Zigbee Alliance is based on the IEEE ． The Zigbee Alliance provides network layer and application support based on the . The Zigbee Alliance provides a network layer and an application support layer and application layer framework based on the Zigbee standard. The Zigbee network layer provides mechanisms for joining and leaving the network, encrypting data, and routing frames. The routing protocol is responsible for forwarding packets of data from the source node to the destination node over the network. In order to efficiently utilize energy and reduce traffic, Zigbee networks allow tree routing, which is a tree structure for site selection. With tree routing, devices do not have to keep a large memory-intensive routing table or perform additional over-the-air downloads to discover paths, thus reducing network traffic. To avoid additional traffic generated by transitions that have more than a certain length of error messages, Zigbee routing allows a router to discover shortcuts.
The routing algorithm AODV is a method that uses the AODV to find the optimal route between the source and the destination nodes. p> The routing algorithm uses the AODV (Ad hoc On Demand Distance Vector) algorithm. Each router maintains a routing table and periodically exchanges routing information with its neighboring routers, updating its own routing table based on the minimum route vector. The application-layer framework defines the guardian network node protocol.
The wireless gateway connects the internal wireless network to the external wired Ethernet network. The design model is shown in Figure The gateway is implemented by arm series and runs Linux operating system Based on the Zigbee protocol frame, the communication protocol of wireless gateway is established, including the device number, data flow direction, data information, etc. After the system is turned on and powered on, the hardware is initialized and the remote network node protocol is defined. System self-test Hardware initialization After connecting with the remote monitoring server, the gateway enters the data flow relay service to realize the function of data protocol conversion After the remote server accepts the connection, it receives the transmitted data at any time and saves it into the database server according to the need.
Experimental results analysis
According to the design of the zigbee wireless monitoring network platform for the human body to carry a continuous collection of pulse pressure signals and real-time display on the monitoring server using a bit A/D converter data sampling frequency Hz wired network environment for the campus LAN waveforms of the collected data. As shown in Figure Figure for the cast without the use of network transmission directly through the computer to capture the pulse signal waveform curve sampling frequency of Hz
By comparing the figure and the figure can be seen through the home monitoring network to capture the pulse data signal waveform basically no deformation, but the delay of the network so that the signal produces a small jitter When the system is connected to the Internet, the delay will be increased, the jitter is more pronounced by increasing the buffer and other methods to reduce the impact of the network delay, and so on, can be used to reduce the impact of the network delay, and so on. By adding buffers and other methods to reduce the impact of network delay on real-time signal acquisition On the other hand, human activity can also bring great interference to the signal. Further measures such as filtering can be taken to minimize the interference
lishixinzhi/Article/program/qrs/201311/11071