Integral-Type Edge-Event- and Edge-Self-Triggered Synchronization to Multi-Agent Systems with Lur’e Nonlinear Dynamics

This paper proposes event- and self-triggered control strategies to achieve distributed synchronization for multiple Lur’e systems with unknown static nonlinearities. Firstly, the integral-type edge-event-triggered function is designed here without Zeno behaviors. Compared to the traditional event-triggered schemes, the considered algorithm has the advantages of reducing controller update frequency and sensor energy consumption. Then, the integral-type self-triggered is further investigated, which implements discontinuous monitoring and discontinuous agent listening. Finally, numerical simulations verified the effectiveness and superiority of our policies.

Consensus Tracking-based Clock Synchronization for the Internet of Things

Clock synchronization provides fundamental timing reference for various services in the Internet of Things (IoT). Unlike centralized synchronization algorithm, which relies heavily on the synchronization routing and brings about error accumulation consequently, the distributed synchronization algorithm achieves clock synchronization through time message exchange and calculation among adjacent nodes, hence the error accumulation can be greatly eliminated. However, the convergence speed of existing distributed synchronization algorithms is generally slow, and network topology information is seldom utilized to improve the convergence speed, which may cause additional energy consumption especially in resource constrained scenarios. To improve the convergence speed of distributed clock synchronization, a consensus tracking-based clock synchronization (CTCS) algorithm is proposed in this paper. By analyzing the synchronization process in the state space framework, the convergence acceleration term is designed to optimize the eigenvalue distribution of synchronization error matrix, hence the convergence speed can be greatly improved. To be suitable for clock synchronization in the dynamic network, a reference clock input term is designed in the clock update formula, which eliminates the oscillation of synchronized clocks triggered by synchronization of newly joined nodes. To prove the convergence of CTCS, an in-depth analysis of the algorithm is conducted. Both simulation and experimental results validate the effectiveness of CTCS in comparison with other solutions.

Descriptive model for distributed element synchronization digital radio networks of the IEEE 802.11s and IEEE 802.11p standards

Today, the basic radio communication standards for building self-organizing networks such as MANET, VANET and FANET are IEEE 802.11s and IEEE 802.11p. The link layer is responsible for establishing and conducting a communication session in these networks. It includes a variety of procedures, the main of which are synchronization procedures, random multiple media access, reserved media access and transmitter power control of network elements. Moreover, in digital radio communication networks of the IEEE 802.11 standards family, both centralized synchronization and distributed synchronization of such network elements are used. However, in digital radio networks of the IEEE 802.11s and IEEE 802.11p standards, the key procedure for establishing and conducting a communication session is the distributed synchronization of the network data elements. It should be noted that there is no descriptive model of distributed synchronization of the IEEE 802.11s and IEEE 802.11p standards digital radio communication network elements, taking into account these standards features. All elements of the IEEE 802.11s and IEEE 802.11p digital radio network send Beacons on a competitive basis. This occurs cyclically at the start of the repeating sync interval. In this regard, the occurrence of three events is possible: successful transmission of the synchronizing Beacon packet, its collision with a similar packet and a service or user data packet. To prevent (reduce) the number of collisions in a digital radio communication network, it is necessary to maintain a constant time difference between the internal time of all network elements. It is worth noting that maintaining a constant time difference for all digital radio communication network elements through guaranteed and timely sending of synchronizing Beacon packets is the main mechanism for distributed synchronization of such network elements. In the event that the calculated value of the time difference Toffsetni for one of the neighboring elements of the digital radio communication network does not coincide with the analogous value obtained in the past synchronization interval Toffsetni-1, then the correction of the own internal TTSF time of the IEEE 802.11s and IEEE 802.11p standards digital radio communication network element begins. The procedure for adjusting the network element internal time continues until the maximum value of this element internal time offset TMaxClockDrift is equal to zero. Also, to reduce or prevent collisions of synchronizing Beacon packets in the data transmission channel, each network element both initially, when entering the network, and immediately when collisions of synchronizing packets occur, Beacon selects and sets the timing parameters of synchronization so that they do not coincide with similar parameters of neighboring network elements. The developed descriptive model of the IEEE 802.11s and IEEE 802.11p standards digital radio communication network elements distributed synchronization includes algorithms for the such network elements functioning, adjusting the such elements intrinsic internal time, searching for an alternative value for the start time of a repeating synchronization interval and adjusting it. The presented model is applicable in the development of analytical and simulation models for assessing the IEEE 802.11s and IEEE 802.11p standards digital radio communication network performance, taking into account the distributed synchronization of such network elements.