A Distributed TDMA Scheduling Algorithm Using Topological Ordering for Wireless Sensor Networks

Abstract

In distributed wireless sensor networks (WSNs), TDMA protocols are a widely applied solution when a reliable data-transferring mechanism is in demand. However, to produce a TDMA schedule is not an easy task. During the scheduling, there can be a large number of conflicts due to the nature of radio access, which leads to a waste of operating time and energy. In this paper, we first present and discuss the concept of Topological Ordering, which is based mainly on the local neighborhood size. It is aimed to create an order of scheduling that helps reduce the competition and conflicts. Next, we propose a fast and effective distributed scheduling algorithm using Topological Ordering, called DSTO, to create a collision-free TDMA schedule. This algorithm is promising in terms of reducing running time and message collisions during the scheduling phase, which in turn reduces overall message overhead. At the same time, efficient time slot allocation, which translates to a shorter frame, is guaranteed. We implement DSTO together with two other distributed scheduling algorithms on OPNET Network Modeler and thoroughly analyze the comparative results to prove its validity and effectiveness.INDEX TERMS Distributed, DSTO, scheduling algorithm, TDMA, topological ordering, wireless sensor networks.

A Real-Time, Distributed, Directional TDMA MAC Protocol for QoS-Aware Communication in Multi-Hop Wireless Networks

“…proposed in [30]- [32] in Section V-B, followed by the analysis of their performance comparison for different static and mobile scenarios in Section V-C.…”

“…Here, pure directional means that no omnidirectional antenna is used at the nodes. Like many other TDMA schemes (such as [7], [10], [25], [30]- [32]), our proposed TDMA MAC scheme assumes the knowledge of 2-hop neighborhood which can be obtained using a gossipbased neighbor discovery scheme, such as [33], [34]. Note that, neighbor discovery is an essential part of directional MAC schemes since the node cannot transmit its packets omnidirectionally [33], [34].…”

“…Similar to the cross-layer schemes presented in [24], [30]- [32], our scheme also assumes that each node has the route information, such as previous and next hops of the route, remaining hop count and flow priority for the routes passing through it, which can be provided by both proactive and reactive routing schemes. If a node has packets for multiple receiver nodes in its buffer, it selects the receiver node based on a QoS-metric which is explained below.…”

“…The use of two additional (optional) control periods can slightly increase the control overhead and frame length of our scheme. In this section, we compare the control overhead of our scheme with the recently published distributed TDMA schemes 4 (i.e., DSTO (distributed scheduling using topological ordering) [30], EB-ET-DRAND (distributed TDMA scheduling algorithm based on the exponential backoff rule and energy-topology factor) [31], and E-T-DRAND (distributed TDMA slot scheduling algorithm based on the energy-topology factor) [32]). These schemes reduce the control overhead and running time required to obtain a conflictfree reservation slot for each node in a dynamic, multihop network.…”

“…The following two metrics are used for the comparison: 1) Number of transmissions is the total control messages transmitted by all nodes to obtain a conflict-free schedule for the reservation period. A lower transmission count reduces the control overhead [30]. 2) Average running time is the time taken for all nodes to acquire a conflict-free reservation slot.…”