Wireless Sensor Network (WSN), which integrates the technologies of sensor, embedded computating, modern network and wireless communicating.is a novel mode of computing and a hotspot of information technology following Internet. It will make a profound influence on many areas in 21 st century.The WSN (Wireless Sensor Networks) can be real-time monitoring, sensing, acquiring and processing the information, which has very broad prospects. It is an emerging hot technology, and has been concerned on all over the world.Sensor node is the basic unit of wireless sensor network.Generally speaking, it consists of the sensor module, processor module, wireless communication module, power management module. Firstly, data is collected by the sensor module, and then the processor module carries out the necessary data processing, finally the data is transmited through the wireless communication module to the destination. In the process of Sensor node operating, power management module plays the role of supplying power to sensor node and extending the life of sensor node. Sensor node has very limited hardware resources, mainly limited energy, the limited communicating capability, limited computing and processing power. When we design and operate the sensor node, it is necessary for us to take into account the above-mentioned problems.Based on the analysis of classic architecture of the existing sensor node, we designed a kind of wireless sensor network node in accordance with the requirements of our project.
wireless network
Wireless Network
Data broadcast
Data broadcast has been accepted as an efficient way of data dissemination in the wireless mobile environment.With broadcast system,data is broadcast on the public downlink channel,Clients “listen” to that channel and download data that they are interested in.In this way,broadcasting one data item can satisfy all the pending queries which require that item.The system workload is independent of the clients number in the service range.As a result,one server can support numerous data access queries simultaneously. The access time,which means the time elapsed between the moment when a query is issued and the moment when this query is satisfied,is a critical metric to evaluate the broadcasting performance.Broadcast scheduling,which determines what to be broadcast and when,can greatly affect the access time,thus has received great attention form the research community for a long time.In this paper,we discuss about the scheduling method for data broadcast system with specially focus on schedu. ling for multi-item queries.