Design Of MAC Protocol For Wireless Sensor Network Based On CSMA

Wireless sensor networks(WSNs)are an important way for people to perceive the world and acquire effective data information.They have been widely used in various scenarios and have become a hot topic in the field of information science.However,due to the limited energy of nodes,the lifetime of networks is limited by the battery life of nodes.Therefore,compared with other wireless networks,energy saving is of vital importance.The medium access control(MAC)protocol in the data link layer can solve the problem of how multiple nodes using shared channels for data transmission.Its design plays an important role in determining the lifetime of the entire network and also affects the overall performance.As a typical representative of random MAC,carrier sense multiple access(CSMA)does not need complex time synchronization and control scheduling algorithm,it can better adapt to the changes in the number of nodes and network topology,and the characteristic of the "listen before transmit" further reduces the conflict.Therefore,designing MAC protocol based on CSMA has more advantages than fixed access MAC protocol such as time division multiple access.Based on this background,the specific research contents of this paper are as follows:(1)We summarize the CSMA mechanism and its application in two aspects.The first is the application of CSMA in different networks,we enumerate the typical MAC protocol based on CSMA in wired networks and wireless networks,and introduce cross-layer,hybrid and multi-channel MAC protocols based on CSMA.The second is the improvement of CSMA mechanism,which can be used to solve specific problems existing in the networks,such as hidden terminals,exposed terminals,energy hole problems and so on.(2)We design a CSMA-based MAC protocol that automatically adjusts the duty cycle according to the network load-QL-MAC.This protocol uses asynchronous wake-up,which combines physical carrier sense with virtual carrier sense to reduce overhearing.The sender can adaptively adjust the duty cycle of the node according to the length of buffer queue.When the network load is low,the duty cycle is halved to reduce energy consumption.When the network load is high,the duty cycle is doubled to shorten the end-to-end delay.We implement the QL-MAC protocol on OMNeT++ and compare it with the typical MAC protocols in WSNs,showing low delay and high energy efficiency.(3)The sensor nodes near the sink will have faster power depletion than the outer-ring nodes in the WSNs,causing energy hole problem.To some extent,the lifetime of the network depends on the energy consumption of the communication between the sink and the nodes near sink.Therefore,we design a special transmission protocol for the nodes around the sink in themulti-sink WSNs-MSDC-MAC,the protocol adopts a dual-channel communication model,CSMA is used to control node access in control channel,and the next slot node transmission is scheduled reasonably in data channel according to the result of control channel.We use simulation experiments to compare with typical networks using CSMA/CA protocol,indicating that MSDC-MAC can alleviate energy hole problems and extend network lifetime.