Link scheduling in sensor networks: distributed edge coloring revisited

Abstract

We consider the problem of link scheduling in a sensor network employing a TDMA MAC protocol. Our link scheduling algorithm involves two phases. In the first phase, we assign a color to each edge in the network such that no two edges incident on the same node are assigned the same color. We propose a distributed edge coloring algorithm that needs at most (δ+1) colors, where δ is the maximum degree of the graph. To the best of our knowledge, this is the first distributed algorithm that can edge color a graph with at most (δ + 1) colors. In the second phase, we map each color to a unique timeslot and attempt to identify a direction of transmission along each edge such that the hidden terminal and the exposed terminal problems are avoided. Next, considering topologies for which a feasible solution does not exist, we obtain a direction of transmission for each edge using additional timeslots, if necessary. Finally, we show that reversing the direction of transmission along every edge leads to another feasible direction of transmission. Using both the transmission assignments we obtain a TDMA MAC schedule which enables two-way communication between every pair of neighbors. For acyclic topologies, we show that at most 2(δ + 1) timeslots are required. Through simulations we show that for sparse graphs with cycles the number of timeslots assigned is close to 2(δ + 1).

Multiple task scheduling for low-duty-cycled wireless sensor networks

“…There are a number of works that focus on scheduling algorithms in WSNs, with the goals to minimize communication latency [14] [18], avoid collision [3] [2] [26], or achieve energy efficiency [23] or fairness [19].…”

“…[18] proposes a heuristic scheduling algorithm to reduce the time delay in data aggregation applications. Gandham et al propose a distributed edge coloring algorithm to derive a collision-free schedule [3]. For high data rate sensor network applications, a novel scheduling technique called Dynamic Conflict-free Query Scheduling (DCQS) is proposed in [2].…”

Locally scheduled packet bursting for data collection in wireless sensor networks

“…Congestion Mitigation at MAC Layer: In order to alleviate interference and contention, various TDMA based MAC protocols [19][20][21][22] and hybrid CSMA/TDMA techniques [1,2,23] have been proposed. TDMA based approaches [19][20][21][22] suffer from high global time-synchronization and slot assignment overheads, which make them unsuitable for scenarios with changing traffic patterns.…”

“…TDMA based approaches [19][20][21][22] suffer from high global time-synchronization and slot assignment overheads, which make them unsuitable for scenarios with changing traffic patterns. For example, in dynamic or moving event scenarios, not all the sensors need to report data to the sink.…”

TDMA scheduling algorithms for wireless sensor networks

“…In the context of TDMA, the problem is to determine the smallest length conflict-free assignment of slots where each link or node is activated at least once [7]. Previous work on scheduling algorithms focus on either decreasing the length of schedules [7,8,9,10,11,12] or distributed implementation [10,13,14,15,16].…”