Multi-Dimensional Conflict Graph-Based Scheduling for Varied Deadline Requirements in IWSNs

Satisfying the end-to-end delay requirements of various real-time data flows is a critical challenge in industrial wireless sensor networks (IWSNs). Since each data flow has different deadline constraints, effectively utilizing network resources while ensuring that data flows meet their deadlines becomes an important problem to be addressed. This paper proposes a joint time slot and channel allocation algorithm based on a multi-dimensional conflict graph, aiming to minimize the total end-to-end delay of multiple data flows with different deadline constraints. First, the concept of a minimum integer scheduling unit (MISU) is introduced to represent the minimum transmission period based on the deadlines, allowing for a unified scheduling structure. Next, a flow-link-slot-channel tuple is proposed to describe potential scheduling schemes, and a multi-dimensional conflict graph (MDCG) is constructed based on the conflicts among tuples. The joint scheduling problem is then transformed into finding the optimal maximum independent set (MIS) in the MDCG. To reduce computational complexity, the original problem is decomposed into a series of maximum weight independent set (MWIS) subproblems using a greedy-based hop-wise scheduling algorithm. Simulation results demonstrate the effectiveness of the proposed algorithm in minimizing end-to-end delay compared to existing algorithms.