Yueyan Qi

The topology architecture of the communication network plays a critical role in ensuring the reliability and security of the Internet of Things. Connectivity reliability is regarded as a key metric for evaluating network topology performance. In this paper, a reliability analysis framework is established to quantitatively evaluate the effects of different deployment schemes and varying numbers of switches and terminal nodes on the connectivity reliability of the novel network, and a deployment scheme for improving network connectivity reliability is proposed. Experimental results demonstrate that, when the network is connected to ten terminal nodes, the maximum reliability achieved under different switch deployment schemes, switch quantities, and terminal node deployment schemes is 0.12%, 0.12%, and 0.14% higher than the corresponding minimum reliability, respectively. Moreover, under the 2-2 switch deployment structure, the network achieves a reliability improvement of up to 8.34% compared with the corresponding minimum reliability. The results further indicate that reducing the number of nodes can effectively improve network connectivity reliability. In multilayer cascading switch deployment architectures, fewer switches in the bottom layer lead to higher reliability, while terminal nodes deployed closer to the bottom layer also contribute to higher network reliability. The proposed deployment scheme provides theoretical support and practical guidance for the deployment optimization of the novel network topology architecture.

The performance of time-critical systems depends heavily on time synchronization accuracy. Therefore, it is crucial to have a synchronization method that can achieve high time synchronization accuracy. In this paper, we propose a new underlying transmission architecture and new synchronization messages. On the basis of these, aiming at the time error problem of the slave clock, we propose an enhanced time synchronization method based on new synchronization messages. Furthermore, we evaluate the performance of the enhanced time synchronization method on the OMNeT++ simulator. In addition, we compare the impact of different crystal oscillator accuracies and different crystal oscillator frequencies on time synchronization accuracy, respectively. Simulation results show that the time offset is at most ±1 clock period using the enhanced time synchronization method. We realize the purpose of timing the master clock and the slave clock by counting the period of the clock signal. Therefore, we needed to round down the time count to an integer. This is the reason why −1 and 1 appear at the same time. When the crystal oscillator frequency used is 80 MHz, the system can achieve a time synchronization accuracy of ±12.5 ns; that is, a nanosecond-level time synchronization accuracy can be achieved. With the reduction of the crystal oscillator accuracy of the slave clock, the synchronization accuracy of ±1 clock period can still be achieved. With the increase in the crystal oscillator frequency, the time synchronization accuracy that can be achieved also improves. The method proposed in this paper provides a new way of thinking and has certain guiding significance for improving the time synchronization accuracy of time-critical systems.