Abstract
Broadcast is a fundamental operation in wireless networks. To this end, many past studies have studied the NP-hard, broadcast problem for always-on multi-hop networks. However, in wireless sensor networks, nodes are powered by batteries, meaning, they have finite energy. Consequently, nodes are required to have a low duty cycle, whereby they switch between active and sleep state periodically. This means that a transmission from a node may not reach all of its neighbors simultaneously. Consequently, any developed broadcast protocols must consider collisions and the wake-up times of neighboring nodes. Henceforth, this paper studies the minimum latency broadcast scheduling problem in duty cycled multi-hop wireless networks (MLBSDC), which remains NP hard. The MLBSDC problem aims to find a collision-free schedule that minimizes the time in which the last node receives a broadcast message. We propose a novel algorithm called CFBS that allows nodes in different layers of the broadcast tree to transmit simultaneously. We prove that CFBS produces a latency of at most . Here, T denotes the number of time slots in a scheduling period, and H is the optimal broadcast latency obtained from the shortest path tree algorithm assuming no collision. We also show that the total number of transmissions is at most 4(T+2) times larger than the optimal value. The results from extensive simulation show that CFBS has a better performance than OTAB, the best broadcast scheduling algorithm to date. In particular, the broadcast latency achieved by CFBS is up to that of OTAB.
Highlights
Wireless sensor networks (WSNs) consist of numerous sensor nodes deployed in a field
As shown in [24], the maximum size of a typical TinyOS packet is 47 bytes, a time slot is usually set to 20 ms, and a MicaZ node can attempt at least 13 transmissions in one time slot
In our simulations, we only consider the packet loss caused by collisions, and assume that unreliable links can be solved within a time slot through multiple transmissions
Summary
Wireless sensor networks (WSNs) consist of numerous sensor nodes deployed in a field. The two methods proposed in [19] have an approximation ratio of 3(ln + 1) and 20 in terms of the number of transmissions, respectively, where is the maximum degree These works, have not addressed the MLBSDC problem in duty cycled networks. Hong et al [20] proved that the MLBSDC problem is NP hard and proposed two approximation algorithms: SLAC and ELAC Their algorithms achieve an approximation ratio of O(( 2+1)T) and 24T +1, respectively, where is the maximum degree, and T denotes the number of time slots in a scheduling period. The broadcast latency of CFBS is mainly influenced by H, which does not rely on the number of nodes or maximum degree All these features constitute key advantages over [22] and result in an algorithm that is suitable for dense networks
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