Implementation And Improvement Of IEEE 802.15.4 Protocol Based On Contiki/cooja Platform

As rapid development of wireless sensor network technology and application requirements, the research of wireless sensor networks has become increasingly active, especially after the release of the IEEE 802.15.4 standard, duing to the characteristics of IEEE 802.15.4 standard, such as low power and low data rate, are suitable for application demands in WSN, the standard is rapidly becoming a research hotspot.Relied on cooperation project with company, which requires the implementation of IEEE 802.15.4-2006 protocol beacon enable mode on the Contiki/Cooja platform as the underlying protocol and agreement to provide supports for the follow-up study. The paper also makes a detailed analysis of IEEE 802.15.4-2006 protocol, to acquire a deep understanding of the characteristic, architecture and protocol flow. What’s more, this paper study the open-source platform including the platform system structure, process model, event scheduling mechanism and system protocol stack. Then this paper has implemented specified modules required by the project, including the PAN network creation and maintenance, network scanning and device discovery, CSMA / CA channel access algorithms, association, synchronization, packet buffed mechanism and packet send and receive unit.Then, the mainstream standard NS2 simulation platform is selected as contrast version. What’s more, three network parameters such as end delay, packet loss rate and throughput are choosed as verified judge the correctness of implemented version in this article. The performance simulation results show that the current version has obvious consistency with the reference one in terms of three parameters metioned above under the approximated simulation scenarios. Taking into account the inevitable differences exist between different platforms, we can make conclusion that this article correctly implements the standard.Since energy-saving mechanism based on active duty control of superframe structure in the IEEE 802.15.4 beacon mode can not dynamically adapt to changing network environment. Aiming at the scenario where there is a higher demand for network reliability and throughput with adequate supply of energy, the paper proposed NDAP algorithm based on the standard superframe structure. The algorithm can dynamically adjust the actual active period according to the network environment sensored by node. Synchronization adjustment is achieved by beacons. Finally, the performance of the algorithm is simulated on Contiki/Cooja and the simulaltion result shows that under the scenario with sufficient power supply and without considering energy issues, NDAP algorithm in a single-hop topology of the network environment has significantly improved the reliability and throughput, and the environment in a multi-hop topology also received some improvement.