Synchronized Sensing and Network Scalability of Low-Cost Wireless Sensor Networks for Monitoring Civil Infrastructures

Applications of wireless sensor networks (WSN) in monitoring civil engineering structures have increased exponentially in the recent past, especially in monitoring high rise buildings. Capturing the global behavior of the structure (e.g. modal periods, mode shapes) using ambient response has become very common due to its applications in large number of damage detection methods. WSN is preferred over traditional tethered systems, mainly due to its dynamic nature and scalability. Capacity of handling large scale data and synchronized sensing are the two main aspects required for the efficiency of the WSN. The upper bound of the time synchronization error (jitter) in WSN should be kept in μs range in order to capture the modal behavior of the structures accurately. Currently, state of the art synchronization protocols that are used for this purpose, are not suitable for the low cost wireless sensor networks because those are radio driven, where the radio core and the CPU core are found separately. This paper discusses about the synchronized sensing method developed for low cost WSN. This protocol is proved to have less than 120 μs jitter and its implementation is discussed in the context of a target building with 48 floors (185 m high).