A topology discovery algorithm for sensor network using smart antennas Ahmed M. Khedr * , Walid Osamy Mathematical Department, Faculty of Science, Zagazig University, Zagazig, Egypt Received 29 May 2005; received in revised form 20 February 2006; accepted 1 March 2006 Available online 29 March 2006 Abstract Wireless sensor networks have recently attracted lots of research effort due to its wide range of applications. In this paper, we focus on sensor network topology discovery problem, where accurate network topology information is important for both network management and application performance prediction. We present on demand algorithm to discover the sensor network topology. The node that receives our topology request collects all topology related information from each node in the network and constructs link information databases. Ó 2006 Elsevier B.V. All rights reserved. Keywords: Smart antenna; Sensor network; Topology discovery; Forwarding database 1. Introduction A sensor network consists of a collection of sensors dis- tributed over some area that form Ad Hoc network. Each sensor node is equipped with some limited memory and processing capabilities, multiple sensing modalities and communication capabilities. The topology information of the sensor network is an important aspect for the supervi- sor, for example, the network supervisor of a sensor net- work will need the topology information to know the areas that are not monitored by the sensor nodes, the nodes that run out batteries and the nodes that carried out away by wind or get eaten by wild boar. These changes are dis- covered by topology discovery algorithms. Topology dis- covery algorithms will help in maintaining connectivity and conserving the rare resources, such as power and band- width of the network. An omnidirectional antenna is an antenna that trans- mits and receives equally in all directions. The natural broadcasting characteristic of an omnidirectional antenna limits both the medium use efficiency and the bandwidth reutilization efficiency. For these reasons, directional antennas were designed to fix the radio propagation direc- tions. However, directional antennas do not eliminate the most significant disadvantage of omnidirectional antennas, i.e., interferences. The next step in designing antennas therefore has to be the deployment of antennas that can minimize these interferences. These antennas are called smart antennas. A smart antenna is an antenna composed of many antenna elements that are arranged in a linear, cir- cular or planar configuration. The number of these antenna elements is a characteristic of the smart antenna. Their role is to increase the radio signal quality by optimizing radio propagation and to increase medium capacity by increasing bandwidth reutilization. Their smartness resides in the combination of the signals received within the smart anten- na elements. This combination is ensured by the Digital Signal Processing (DSP). So we consider the use of smart antenna systems in order to achieve reliable and efficient data delivery in wireless sensor networks. In this paper a topology database called FDB is con- structed by collecting topology link information from all nodes where link information is defined and identified by 0140-3664/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.comcom.2006.03.002 * Corresponding author. Tel.: +20 102093552; fax: +20 055 2308213. E-mail address: amkhedr@yahoo.com (A.M. Khedr). www.elsevier.com/locate/comcom Computer Communications 29 (2006) 2261–2268