Cooperative Time Synchronization Research Articles

Cooperative time synchronization via laser/radio inter-satellite links in navigation constellations

Time synchronization is vital in positioning, navigation, and time services in satellite navigation systems. Under the autonomous operation mode, time synchronization of the entire constellation is realized via inter-satellite links to support normal navigation and positioning services. Compared with radio inter-satellite links, continuous laser links are able to provide clock deviation measurements with the same time tag and higher accuracy. In this paper, cooperative time synchronization via laser/radio inter-satellite links is proposed. First, a time comparison network based on the continuous laser inter-satellite link is established, and an inter-satellite time reference is generated using the weighted average algorithm. Then, through radio inter-satellite links, clocks of satellites outside the laser inter-satellite link network are traced to the time reference by using the distributed Kalman filter algorithm, thereby realizing time synchronization of the entire constellation. Finally, a simulation based on the new generation of BeiDou constellation is performed. Results show that the stability in the short and medium terms of the time reference generated via the cooperative time synchronization method is significantly improved compared with that generated via radio inter-satellite links. The standard deviation of the time synchronization error in the constellation is better than 0.05 ns.

A Cooperative Time Synchronization Protocol for Wireless Sensor Networks

The synchronous precision of synchronization protocol is low and the scalability is limited strictly in large scale wireless sensor networks (WSNs).Considering the issue, a novel cooperative time synchronization protocol based on pulse-coupled oscillators and distributed diffusion (CTSP) is proposed in this paper. The protocol works in two phases：clock tick synchronization phase and time synchronization phase．In the clock tick synchronization phase, the phases of the pulse-coupled oscillators is changed by the pulse coupled signal of the SINK node. The tick synchronization of all nodes is achieved by distributed diffusion. In time synchronization phase, the average time of reference nodes is spread to a limited number of hops based on two-way message exchange mechanism. Moreover, in order to achieve the synchronization of entire network, it adopts the method of mutual diffusion to finish the approximately synchronization between the node time and the average time of all nodes. By comparing CTSP with TPSN, we show that, CTSP can synchronize the network quickly with good precision convergence speed and scalability, which appropriates for large-scale WSNs.

Cooperative Time Synchronization Based on Mining Wireless Sensor Network

With the energy market demand increasing, coal mine safety production monitoring system based on wireless sensor network has been widely used. The traditional wireless sensor network synchronization method based on packet switching is very difficult to achieve synchronization accuracy and energy consumption at the same time. Paper presents a cooperative time synchronization method based on packet message exchange (CTS), Analysis of synchronous packet information interaction process, the introduction of cooperative relay will not change the synchronization precision. Synchronous grouping information for sending and receiving ends for receiving and forwarding to reduce the transmission power, reduce energy consumption through cooperative relay. Theoretical analysis and computer simulation show that in the condition of not reducing the synchronization precision, it can achieve the purpose of reducing energy consumption by introducing the cooperative relay in the horizon channel model can reach 4 times the energy efficiency.

On the scalability of cooperative time synchronization in pulse-connected networks

The problem of time synchronization in dense wireless networks is considered. Well-established synchronization techniques suffer from an inherent scalability problem in that synchronization errors grow with an increasing number of hops across the network. In this work, a model for communication in wireless networks is first developed, and then the model is used to define a new time synchronization mechanism. A salient feature of the proposed method is that, in the regime of asymptotically dense networks, it can average out all random errors and maintain global synchronization in the sense that all nodes in the multihop network can see identical timing signals. This is irrespective of the distance separating any two nodes.