| The wireless sensor network (Wireless Sensor Network, WSN) the technology is a high technology and new technology which about 2000 appeared, is possibly called possibly to change the world one of ten key technologies, widely applied in the military, the environmental monitoring, the intelligence lives at home, the industrial production and so on each domain.ZigBee wireless sensor networks based on the IEEE 802.15.4 standard technology. The system for low-rate wireless sensor networks, low-cost radio-frequency transmission, each node only a small energy, small-power batteries for long-term power supply, can be a point-to-multipoint, peer-to-peer communication between two points, fast network Automatic configuration, automatic restoration of power and senior management, any sensors can be coordinated between the data communications. Mainly used in short-range wireless systems, sensors or secondary instruments to provide wireless network access duplex, to meet a variety of sensor data input and output control and command information needs of the existing network and wireless technology.In the wireless sensor network each node is a transmission device is also a receiver, may at any time to join the network. Each node can transmit data to other devices, resulting in a chain network. As the data transfer just a short distance, which can save a lot of energy. Moreover, these nodes are self-organizing and self-repair capabilities, when a node problem, the system will be able to find alternative transmission path. Linked to that of the equipment more, the whole network more efficient, more ability to repair. Thus wireless sensor network technology in the relatively poor performance of the industrial environment more reliable.Wireless sensor network technology is the latest wireless technology, the most popular applications. It is a new, so there is no uniform standard in the world there are many research institutions and organizations in the development of technology and specifications, put forward a variety of technical standards. They are ZigBee, Z-wave, Bluetooth, Wibree, 6loWPAN and so on, Wibree by Nokia in October 2006 issued a new standard, the company received the support of many, including Broadcom, CSR and Epson, and so on. These technical standards to Z-Wave and ZigBee the most mature.ZigBee international standard IEEE 802.15.4 technology for the foundation and a broader target market, the potential demand for a larger amount. In contrast, Denmark's Zensys raised by the Z-Wave technology is not only not have to rely on international standards for its application are also limited to home automation, ZigBee may not be able to apply in the industrial, medical, security and many in the field.ZigBee word from the bee pollen found in the location of the group, through the Z-shaped hop dance to this companion to the exchange of information. It can be said is a small animal through the simple means of "wireless" communication, it is a call to focus on low-power,low-cost,low complexity, low rate of short-range wireless communications technology, but also include moral .ZigBee technology is not entirely unique to the new standards. Its physical layer, MAC layer and link layer using IEEE802.15.4 standard, but based on the improvement and expansion. The network layer, application layer and the convergence of high-level norms applied by the ZigBee Alliance for the development of the. The prominent features of ZigBee, especially in the low-power, low-cost, mainly in the following areas.①low power consumption. In the low power standby mode, 2.5, dry batteries can be a node to support the work of 6 to 24 months, or even longer. This is the highlight of the ZigBee advantage. By comparison, Bluetooth can only work a few weeks, WiFi can only work a few hours.②low-cost. Through a substantial simplification of the agreement (see Bluetooth 1/10), reducing the requirements for the communications controller, according to the forecast, 8051 to the 8-bit microcontroller is estimated that full-featured master node need to 32KB code, sub-node function 4 KB code to a small, ZigBee and royalty-free agreement.③low rate. ZigBee work in the 20-250kbps rate lower, respectively, to provide 250kbps (2.4GHz), 40kbps (915MHz) and 20kbps (868MHz) of raw data throughput to meet the low-rate data transmission applications.④close range. The general scope of the transmission between 10-100m, an increase in the RF transmission power, can also be increased to 1 - 3km. This refers to the distance between adjacent nodes. If the routing and inter-node communications relay, will be able to further transmission distance.⑤short delay. ZigBee faster response, from the general state of sleep into the work of only 15ms, connecting node into the network only 30ms, further energy saving. By comparison, Bluetooth needs 3-10s, WiFi needs of 3s.⑥high capacity. ZigBee may be star, mesh networks and sheet structure, a master node by the management of a number of sub-node, a master node can be up to the management of sub-node 254; at the same time also by the master node on a network node management, composed of up to 65000-node network.⑦agreement simple, safe. The average length of the ZigBee protocol stack of Bluetooth is only 1/4, which simplify the low-cost, interactive and maintainability is very important. ZigBee technology provides data integrity checks and authentication features to provide a three-tier security model, the flexibility to determine the safety of property, network security can be effectively protected.⑧license-free band. Direct sequence spread spectrum in the industrial scientific medical (ISM) band -2.4GHz (global), 915MHz (United States) and 868MHz (Europe).This article first introduced the concept of ZigBee technology, architecture, features, as well as its applications; and ZigBee-based peer-to-peer network topology to form clusters, the types of networks with high flexibility and scalability of energy; on ZigBee Wireless sensor networks for the performance of the simulation, network security, energy conservation, as well as in areas such as robustness analysis.Finally, such a ZigBee network will be applied to the power meter reading. The system has the following characteristics:(1) the use MESH network to ensure the reliability of data transmission.(2) of each floor unit to set up a ZigBee remote node.(3) of a cell set up a central node ZigBee.(4) ZigBee network node centers to upload copy-center database. |
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