Communication Protocol For Wireless Sensor Network Based Bridge Monitoring System

During dozens years even hundreds years usage, bridge accidents may take place suddenly, due to the natural disaster or the human damage. A large amount of nonessential loss may be reduced or avoided by means of real-time structure healthy monitoring system. However, the traditional structure monitoring system is expensive, and difficulty to install, as a result, it can not meet the requirements of the modern bridge structure monitoring. Recent advances in micro-electro-mechanical systems (MEMS) technology, wireless communication, and microprocessor have enabled the development of wireless sensor networks. The wireless sensor networks have many advantages, such as low cost, easy installation, besides, the maintenance and update cost for a wireless sensor network is small. Therefore it's suitable for the remote environment, equipment, large-scale civil structure monitoring. Thus, under the project of Research and development of bridge wireless monitoring technology founded by the Ministry of Communications, this paper designs a wireless communication protocol for bridge healthy monitoring.Firstly, this paper introduces the wireless sensor network's application and the prospects for development, as well as what must be considered in designing a wireless communication protocol. Secondly, our design and implementation process for communication protocol are presented. The designed communication protocol has taken power consumption, slef-organization, reliability, synchronization and real-time data collection into account. These sensor nodes deployed in different points form a multihop chain network through slef-organization protocol. After the initialization process, the wireless sensor nodes access the wireless medium with TDMA protocol in order to avoid interference between different nodes. The working process of the designed communication protocol can be divided into two modes, namely, stable operation mode and quasi-real-time operation mode. In the stable operation mode completes the network initialization, the topology maintenance, non-real-time data collection; In the quasi-real-time operation mode, the sampling data of some important sensor nodes can be transmitted to the fusion center in time. All nodes synchronize with the center through a definite clock offset achieved by test in the stable operation mode, whereas, all sensor nodes synchronize with the last level cluster head in the chain topology. This paper also analyzes the synchronous delay in detail. Finally, the experimental results of the sensor network are presented, and it proves that the communication protocol can work normally. The shortcomings of the current system and the future work are also given.