Tham khảo tài liệu 'data acquisition part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Clock Synchronization of Distributed Real-Time Industrial Data Acquisition Systems 51 Clock synchronization over wireless networks In the last years wireless networks are becoming very popular. The high flexibility of wireless solutions allows the creation of innovative data acquisition systems to monitor a great number of quantities. Moreover the data logging over a wide area can be done by means of wireless distributed data acquisition systems. Generally speaking a wireless distributed data acquisition system is composed by a large number often variable of autonomous nodes distributed in the environment. Usually the devices used to develop a wireless network should be low-cost ruggedized low power smart and with high computational power. For instance devices can satisfy large part of these requests and they are widely used to implement wireless distributed acquisition applications. Besides helping in data fusion of measures the synchronization of wireless network is useful both for reducing the power consumption of each node and for improving the medium access control. For instance the synchronized node can transmit receive during its time slot while it remains in low power idle the rest of the time. The traditional protocols cannot be used because of the low energy available in the nodes limited storage capabilities and limited communication capabilities. Synchronization algorithms for wired networks require the exchange of a large amount of messages and the continuous listening of synchronization messages. Moreover the number of active nodes and the network topology of a wireless network may vary frequently and unpredictably. For instance such situations can lead to unstable estimation of the end to end delay of a message. For all these reasons in the last years special synchronization protocols have been developed. With respect to wired networks the number of wireless synchronization protocols is quite high. In the following a very short .
