Research And Implementation On DSME Protocol In 802.15.4e

Application demands impel the researches on wireless sensor networks more thoroughly. As a standard of WSNs, the protocol of IEEE 802.15.4 has been studied in detail. The diversity of the network makes the proposed standard which provides the same functionality of the network can not meet demands of the specific needs in various scenarios. Therefore, five different modes have been proposed in the released amendments——IEEE802.15.4eTM-2012 by the international Institute of Electrical and Electronic Engineering(IEEE) for different industrial scenarios, DSME agreement belongs to one of them.This article is one of the outcomes carrying on studying on school&enterprise cooperation project. DSME agreement defines a variety of new mechanisms which are suit for the industrial scene with a fixed delay, flexible and scalable feathers. Firstly, the thesis makes specific introduction to DSME protocol and the platform involved protocol realization. Then, according to the regulations of DSME and platform mechanisms, the implementation of DSME is divided into two parts involved crucial modules and auxiliary modules, both of them will be discussed. The key modules take primary responsibilities included the creation of a new PAN, network scanning, nodes association, communication in the form of Multi-Superframe structure, coordination and consultation of the slot resources, packing and parsing frames. The secondary modules aim at protecting the reliability of functions defined by DSME protocol, which contained maintenance and management mechanisms of cache, the confirmation of message transmitting and receiving.To verify the correctness of implementation of DSME, a series of functional tests are set up in the platform of Contiki, with the help of simulation tool, Cooja. After that, a simulation with 200 nodes in the network scenario is performed, and the performance is compared with Beacon enabled 802.15.4 network. The result shows that the packet successful deliver ratio of the network has significantly improved involved in DSME protocol. While the average delay of DSME network is relatively fixed, the delay of DSME network is not sensitive to the burden of network traffic load.As the definition of standard protocol, the duration period of each stage(i.e. CAP and CFP) is permanently fixed during multi-superframe communication while the network is running, which makes the time resources can not be assigned properly based on the real traffic situation either in CAP or in CFP stage.In order to adapt to the actual variation of network scenarios and cope with the changing load on message stream, this paper proposes a dynamic algorithms to adjust time resources according to the communication pressure and the packets stored in the node during CAP and CFP stage. The main idea of the algorithm is that the number of slot will be reduced when the pressure in CAP stage is higher than CFP, leading to the extension of time resources and lowing down CAP communication pressure in CAP stage; on the other hand, when the communication pressure is increasing during CFP phase, reducing the length of the CAP appropriately, and expanding the number of time slots to reduce communication pressure in CFP stage.