| Since the 21 st century, the Wireless Sensor Network(Wireless Sensor Network, WSN) has been developing rapidly, and it has got a lot of attention as one of the underlying network perception of the Internet of Things in recent years. So the Wireless Sensor Network has a very big potential to develop and very urgent needs to research. The media access control protocol(Medium Access Control, MAC) is an important protocol of data link layer, because it can distribute the channel resources reasonably, create an effective communication link for Wireless Sensor Network, ensure the communication between adjacent nodes, at the same time provide service to network layer, and affect the performance of the routing protocol. So we should design a MAC protocol with high performance if we want to build a high-powered WSN.Now some MAC protocols are not suitable for WSN because there are some differences between WSN and traditional Wireless Network. The S-MAC protocol is designed for WSN in specialty, it can reduce the consumption of energy effectively. But the S-MAC protocol also introduce the sleep time delay, data queue for long time, the network throughput is limited. According to the different methods of data collection, this thesis studies the MAC protocol suitable for time-driven network and event-driven network respectively. The mechanism of the S-MAC protocol is very suitable for the time-driven network, but it also has some problems. This thesis proposes the RC-MAC protocol which is based on the cross layer design method to improve the S-MAC protocol.RC-MAC protocol changes the format of the RTS/CTS that is the control frame of the MAC protocol. RC-MAC protocol adds routing information of the network layer. And it makes the nodes know the advanced path, shake hands in advance, and book the channel. Multiple times adaptive listen is introduced, the data in a scheduling cycle can be transmitted multiple hops. The mechanism of handshake is changed to reduce the consumption of sending control information. It can let the nodes which are in the path of communication to receive the information on time, let the other nodes which are not in the path of communication sleep in accordance with the original cycle. According to the theoretical analysis and OMNET++ simulation, it turn out that the RC-MAC protocol can effectively reduce the sleep time delay while the consumption of energy does not increase so much, and can effectively improve the throughput in the high load situation. The RC-MAC protocol is just applied to the time-driven network which has good link because it uses the adaptive listen for many times and changes the mechanism of handshake.This thesis studies and analyses the large-scale event-driven Wireless Sensor Network. This kind of networks has large data transmission just when events occur, and only collect a little data periodically in normal times. According to this characteristics of network’s data transmission, the network is divided into the event activated state and non-event state. We propose the EDC-MAC protocol which is suitable for event-driven network.EDC-MAC protocols in the state of non-event is still using S-MAC protocol, according to the information reporting period set cycle length and duty cycle of the MAC protocol. Because nodes can sleep when not to transmit data, so it can save energy effectively. In the state of the event, the nodes that perceive events change routing and MAC policy at the same time. In route layer we use clustering routing protocol, and using the node energy information and the length of the distance to the sink node to select the cluster heads. Taking TDMA scheduling mechanism within a cluster, effectively reduce the collision, and the sleep time delay. Finally we use the OMNET++ to analyze, the results show that using the EDC-MAC protocol can save most of the energy and reduce more time delay of data submitted than the situation that just using S-MAC protocol and ED-TDMA protocol. |
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