Research On MAC Protocol For Wireless Sensor Networks Based On Capture Effect

The wireless sensor network is a multi-hop wireless ad hoc network which consists of a large number of sensor nodes deployed in the monitoring area.It is mainly used for the real-time monitoring of the target,information collecting and data transmitting.As the sub layer of data link layer,medium access control layer receives and sends MPDU on the basic services provided by the physical layer.MAC layer is responsible for the allocation of radio channel resources,channel access management and error control,etc.Due to the limitation of computation,storage capacity and energy resource,the MAC protocol of WSN should simplify data flow and be energy-efficient.Most MAC protocols use the duty cycle to save energy,in which nodes periodically sleep/work.However,in the large scale and high load network,especially in the unstable environment,the low channel access rate and great energy consumptio n,which result in the performance decline of MAC protocol,are two of the most important problems to be solved.For the performance degradation of MAC protocol in the large scale and high load network,we propose a power allocation algorithm based on capture effect,and use it as the channel arbitration method of MAC protocol.It not only improves the channel access rate and decreases data transmission de lay,but also reduces energy consumption by setting reasonable transmit power.The main contributions of this paper are summarized as follows:Firstly,we propose a power allocation algorithm for sensor nodes based on the capture effect,which improves the success rate of capture effect by setting transmit power.We investigate the potential gains of the algorithm by implementing it on a real testbed of TELOSB nodes and the TOSSIM simulator,and experimental results show that the algorithm can effectively improve the success rate of capture.Secondly,we design the CBPW-MAC protocol based on capture effect,which uses the power allocation algorithm mentioned above as the channel arbitration method.CBPW-MAC protocol can efficiently avoid the transmission collision and energy consumption caused by the idle listening and network delay.The experimental results show that the reliability of CBPW-MAC is much higher than PW-MAC protocol,as well as the time and power efficiency.CBPW-MAC protocol can reduce the convergence time and energy consumption of nodes in the premise of reliability,especially in large scale,high density and high load networks.Finally,in order to make the sensor nodes build an accurate channel model in the harsh environment and changeable wireless network,we design a channel estimation method based on statistics by using the beacon in CBPW-MAC,and propose the CEPW-MAC protocol for unstable channel environment.C EPW-MAC adjusts the transmission strategy of the CBPW-MAC protocol based on the dynamic channel estimation to improve the robustness of the channel arbitration and the performance of the communication protocol.The simulation results show that,the time and energy efficiency and reliability of CEPW-MAC protocol are higher than the CBPW-MAC and PW-MAC protocol,in the unstable environment.