Research On Deterministic Transmission Techniques Without Time Synchronization

The time-triggered transmission mechanism is the core foundation for deterministic transmission in Time-Sensitive Networks and Time-Triggered Ethernet.This mechanism largely depends on time synchronization to enable deterministic transmission.As a result,time synchronization faults will make deterministic transmission infeasible.When time synchronization fails,the typical approach is to use asynchronous methods,which involve traffic shaping policy and priority scheduling.These methods can only give an upper bound of end-to-end delay and cannot customize the end-to-end delay for each flow.Furthermore,the delay difference between the worst and best cases tremendously weakens the determinacy of transmission.In order to achieve the same determinacy(instant delay jitter)as in the time synchronous case,this paper addresses the problem of deterministic transmission without time synchronization,with the objective of maximizing the number of flows that can satisfy deterministic transmission.The main work of this paper is as follows:First,this paper designs a deterministic transmission mechanism without time synchronization.Unlike current time-triggered networks that rely on the global clock for deterministic transmission,the deterministic transmission mechanism without time synchronization uses the local clock instead of the global clock,time-triggered transmission is performed by configuring the residence time of the flow in switches.This paper gives conditions for the deterministic transmission of flows without time synchronization,and proves that the problem of maximizing the number of deterministically transmitted flows,defined as the ”maximum no-overlapped flow problem”,is an NP-complete problem.Secondly,based on the deterministic transmission mechanism without time synchronization,this paper constructs a scheduling model for deterministic flows.Then designs a scheduling algorithm for mixed criticality level flows,prioritizing the deterministic transmission of high criticality level flows,and incremental scheduling of other flows.This paper implements a constrained solution algorithm based on the integer linear programming solver(CPLEX-Solver)and a polynomial-level time complexity heuristic solution algorithm.Finally,in order to further increase the number of flows that can be transmitted deterministically without time synchronization,this paper divides the network communication domain for the application scenario,and increase network redundancy by increasing the number of switch ports or switches in the domain.This paper constructs a deterministic topology reconstruction model without time synchronization,and implements a linear constraint solution algorithm and a polynomial-level time complexity heuristic solution algorithm.The experimental results show that the deterministic topology reconfiguration of flows proposed in this paper can effectively improve the deterministic transmission capability of the network without time synchronization.