Critical‐Path Aware Scheduling for Latency Efficient Broadcast in Duty‐Cycled Wireless Sensor Networks

Abstract

Minimum latency scheduling has arisen as one of the most crucial problems for broadcasting in duty-cycled Wireless Sensor Networks (WSNs). Typical solutions for the broadcast scheduling iteratively search for nodes able to transmit a message simultaneously. Other nodes are prevented from transmissions to ensure that there is no collision in a network. Such collision-preventions result in extra delays for a broadcast and may increase overall latency if the delays occur along critical paths of the network. To facilitate the broadcast latency minimization, we propose a novel approach, critical-path aware scheduling (CAS), which schedules transmissions with a preference of nodes in critical paths of a duty-cycled WSN. This paper presents two schemes employing CAS which produce collision-free and collision-tolerant broadcast schedules, respectively. The collision-free CAS scheme guarantees an approximation ratio of (Δ-1)T in terms of latency, where Δ denotes the maximum node degree in a network. By allowing collision at noncritical nodes, the collision-tolerant CAS scheme reduces up to 10.2 percent broadcast latency compared with the collision-free ones while requiring additional transmissions for the noncritical nodes experiencing collisions. Simulation results show that broadcast latencies of the two proposed schemes are significantly shorter than those of the existing methods.

An Iterative Power Gradient Searching Algorithm towards the Slot and Power Joint Scheduling Problem in MANET Broadcast

“…[21] first proposed the MLBSDC problem and proved its NP-hardness. In a recent study, [9] performed collision-free scheduling and collision-tolerant scheduling with a preference for nodes in critical paths.…”

“…For the minimum-delay slot scheduling, we utilized the collision-free critical-path aware scheduling (CF-CAS) proposed in [9] to help generate an available scheduling plan, in which the scheduling is based on the critical path in the topology so that the delay is minimized. An example of CF-CAS is shown in Figure 3, where Figure 3a denotes a topology in which each link indicates a bidirectional link.…”

“…In this study, we compare IPGS algorithm with CF-CAS [9] in which each node transmits with the highest power defined as CF-CAS-high, and a modified discrete power shrink(DP-Shrink) algorithm originated from r-shrink [14] in which transmitting power levels are discrete. The two baseline algorithms are derived from MLBS and MEB respectively, which are both single-target optimizing problems in a static topology.…”

“…The traditional broadcast scheduling of ad hoc networks [3]- [9] mainly focuses on slot scheduling for a minimum broadcast latency, without more consideration of power controlling. However, if the transmitting and receiving nodes are close to each other, a high transmit power would incur a waste of energy.…”