1 NBA: A Novel Broadcasting Algorithm for Wireless sensor Networks Nedal Ababneh, S. Selvakennedy and Khaled Almi’ani Advanced Networks Research Group, School of Information Technologies, J12 University of Sydney, Austarlia {Nedal,skennedy, kalmiani}@cs.usyd.edu.au Abstract Broadcast in radio based wireless networks has been a difficult problem. When a node broadcasts, all nodes within its radio coverage will attempt to relay the message by rebroadcasting, causing excessive radio communication in the region that leads to what so- called broadcast storm problem. In this paper, we present a novel broadcasting algorithm, termed NBA, for wireless sensor networks. It uses two-hop neighborhood information to select a subset of nodes to rebroadcast messages among all nodes in the neighborhood. Each node in the network selects its own set of forwarder neighbors from among its one-hop neighbors. NBA is evaluated against Span, a well- known algorithm from the literature through realistic simulations using TOSSIM. Simulation results demonstrate that under dense deployment, the proposed algorithm performs better. Keywords: Broadcasting, TinyOS and TOSSIM, simulations. 1. Introduction The vision of wireless sensor networks is to deploy hundred to thousands of smart, low cost and low power sensors close to the objects and environment for in-situ sensing and actuation [2]. Although dense deployment is desirable in many wireless sensor networks applications scenarios, it also causes problem with the radio communication, particularly on broadcasting. When a sensor node broadcasts a message all the nodes within its communication range will attempt to relay the message further by rebroadcasting, causing excessive radio communication within the region. This not wastes system resources but also causes network congestion, leading to what so-called broadcast storm problem [14]. There have been a considerable number of papers addressing the broadcast storm problem [3,7,13,14,15,16,17,19] in the literature, mostly using theoretical analysis or simulation and involving MAC and power control mechanisms. The general strategy is to determine a minimum set of forwarders from one-hop or two-hop neighbors to rebroadcast the packets and at the same time guarantee that all nodes in the network can receive the packets by preserving adequate connectivity. The goal of this study is to investigate strategies to alleviate broadcast storm in stationary, dense wireless sensor networks. The algorithm presented in this paper, termed NBA, is a novel broadcast algorithm that increases network lifetime while maintaining connectivity, guaranteeing multi-hop reachability from any source to any destination with a reasonable throughput. NBA is built on the notion that when a region of a shared channel wireless sensor network has a sufficient density of nodes, significant network capacity is obtained by selecting minimum number of forwarder nodes in the region. Using the two-hop neighborhood information, selected nodes sequentially select a subset of nodes to be forwarder among all nodes in the neighborhood. Moreover, to ensure fairness, the role of forwarder nodes is rotated periodically to ensure energy-balanced operations. The selection of forwarder nodes is akin to multi-point relays diction in OLSR, a proactive routing protocol for mobile ad-hoc networks. We have chosen Span [4] to be used for benchmarking purposes against our proposed algorithm. In Span each node makes periodic, local decisions on whether to sleep, or join a forwarding backbone as a coordinator (forwarder) based on an estimate of how many of its neighbors will benefit from it being coordinator and the amount of energy remaining on it. The following coordinator eligibility rule in Span ensures enough coordinators are elected so that every node is in the radio range of at least one coordinator. A non-coordinator node should become a coordinator if it discovers that two of its neighbors cannot communicate with each other either directly or via one or two coordinators. Span employs a load balancing strategy, where each coordinator periodically checks if it should withdraw as a coordinator. A node should withdraw if every pair of its neighbors can communicate with each other either directly or via one or two other coordinators. In order to also rotate the coordinators among all nodes fairly, after a node has been a coordinator for some period of time, it marks itself as a tentative coordinator if every pair of neighbor nodes can communicate with each other via one or two other neighbors, even if those neighbors are not currently