A Wireless Sensor Network (WSN) consists of spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants and to cooperatively pass their data through the network to a main location. The more modern networks are bi-directional, enabling also to control the activity of the sensors. The development of wireless sensor networks was motivated by military applications such as battlefield surveillance; today such networks are used in many industrial and consumer application, such as industrial process monitoring and control, machine health monitoring, environment and habitat monitoring, healthcare applications, home automation, and traffic control. Sensor networks are special case of ad-hoc networks and use for different application. Sensor networks have been used in medical and household and military fields. The WSN is built of "nodes" - from a few to several hundreds or even thousands, where each node is connected to one (or sometimes several) sensors. Each such sensor network node has typically several parts: a radio transceiver with an internal antenna or connection to an external antenna, a microcontroller, an electronic circuit for interfacing with the sensors and an energy source, usually a battery or an embedded form of energy harvesting.Multiple purpose sensors has been produced with low cost, low energy consuming and small size by developing in produce of micro-electronic systems, wireless communication and digital electronic. Sensor nodes have combined from sensing, processing and communication part can collaborate as network in large number. Monitor environment and event detection is one of the usual using in wireless sensor networks. Area monitoring is a common application of W. In area monitoring, the WSN is deployed over a region where some phenomenon is to be monitored. A military example is the use of sensors to detect enemy intrusion; a civilian example is the geo-fencing of gas or oil pipelines. Due to participating nodes in event detection process are unreliable, collaboration among nodes are necessary in event detection. The aim o0f this thesis is presenting efficient and fault tolerance way for event detection with help of low traffic communication model. An event can be atomic or composite. Atomic events are combined of one sensor’s data and composite events are made two or more sensor’s data. Event detection usually has some restriction such as low energy, low transmitting band and periodical failure so utilize collaborating is necessary in wireless networks. In naive event detection each node should have all necessary sensors for event detection but in most ca Keywords: Atomic event, Composite event, Low traffic communication model, Inner cell traffic, between cell traffic.
