.csma / Ca Protocol In Sensor Networks And Improvement

Recently, along with wireless communication technology,sensor technology,information acquisition and processing technology rapid development, appeared the wireless sensor node which has the low cost and low power consumption. Lots of wireless sensor nodes construct a self-organizing and distributed Wireless Sensor Network(WSN), which is a late-model of infrastructureless wireless network. WSN can monitor,perceive and acquire various environmental or object information by a real-time way , process it and transmit it to the monitor. WSN is a new research field in communication network and will have a wide application in military,architecture,agriculture,environment monitor and medicine field.The typical working way of WSN is throwing sensor nodes to a certain area by air vehicle and they construct a self-organizing mobile network rapidly. As made by a large number of sensor nodes that are placed randomly, it is difficult to change the power. For it is MAC protocol that control RF module directly, it is a key point to design a MAC-layer protocol which can not only reduce power loss but also avoid collision to ensure a high transmit rate.During this thesis, the conception of WSN and function of MAC are described firstly to show the research background. Secondly, the characteristics,network architecture and application field of WSN are introduced. Last, the characteristics of MAC-layer are analyzed in detail and various MAC access protocols are compared. On the basis of this, the CSMA/CA protocol is improved to present a new MAC protocol which fits the characteristics of WSN.Main improvement are : 1. introduce sleeping schedule from S-MAC to save power . 2. improve backoff algorithm– carry out a random delay before monitor the channel and use fix-length backoff window to increase successful rate. At last, the results simulated on the VC6.0 platform show that designed protocol achieves its design goal.