Research On Efficient Data Transmission Mechanism For Receiver-based MAC Protocol In Wireless Sensor Networks

In duty cycle wireless sensor networks,nodes are in a dormant state for most of the time,which deduces the chance of receiving data and intensifies the competition among senders,especially in dense networks.Therefore,concurrent data transmission is a very common phenomenon in WSN,under which there are many senders compete to send data almost simultaneously after receiving the receiver's beacon when using receiver-based MAC protocol,resulting in conflict more easily.Besides,due to the sharing characteristics of the wireless channel,the packet and Beacon and ACK may collide among each other when using receiver-based MAC to transmit data,which increases the probability of collision and reduce the channel utilization.Therefore,an efficient data transmission mechanism is needed to improve the performance of the receiver-based MAC protocol in concurrent transmission scenarios.This thesis proposes two data transmission mechanisms to solve the problem of low channel utilization in concurrent transmission scenarios when using receiver-based MAC protocol,and tests the performance of the proposed mechanisms on Telos B nodes.This thesis mainly has the following three contributions:Firstly,based on the UPMA architecture,Rb Mac is implemented on the Telos B node in order to test the performance of the proposed data transmission mechanisms on a real testbed of Telos B nodes conveniently.Secondly,this thesis proposes a data transmission mechanism based on a quick-reply ACK method.This thesis analyzes the probability of collisions when two nodes transmit concurrently,finding that shortening the reply time of ACK can reduce the collision in networks,and thus proposing a quick-reply ACK method.Experimental results show that the quick-reply ACK method not only shortens the ACK response time,but also carries extra information in the ACK.Then this thesis proposes a data transmission mechanism based on the quick-reply ACK method.Experiments on Telos B nodes show that when the number of competing nodes in the network does not exceed four,the proposed mechanism has high reliability and low energy consumption,and is suitable for low duty cycle networks.Finally,this thesis proposes a data transmission mechanism based on capture effect.In order to meet the requirement of the capture effect on SINR,a balanced greedy method is proposed in this thesis to allocate transmit power for its neighbor nodes.Experimental results show that the time complexity of this method is low and the total solution rate is not less than 90% when the number of neighbors in the network does not exceed eight.Then this thesis proposes a data transmission mechanism based on the capture effect,which meets the requirement of the capture effect on packet arrival time difference.The experimental results show that the proposed mechanism effectively improves the channel utilization when the number of neighbors in the network does not exceed eight.Taking into account the transmission probability of the node during concurrent transmission,this thesis optimizes the proposed balanced greedy method.Experimental results show that the optimized balanced greedy method can maximize the number of neighbors in the result set with guaranteed competition success rate when the number of neighbors in the network does not exceed 10.In addition,when the transmission probability of the senders in the network is low,the competition success rate of the optimized balanced greedy method is higher because it can allow more nodes to seize the opportunity to send data.