J. Parallel Distrib. Comput. 66 (2006) 542 –555 www.elsevier.com/locate/jpdc A rule-based adaptive routing protocol for continuous data dissemination in WSNs  Daniel F. Macedo a , ∗ , Luiz H.A. Correia a, b , Aldri L. dos Santos a, c , Antonio A.F. Loureiro a , José Marcos S. Nogueira a a Federal University of Minas Gerais, Belo Horizonte-MG, Brazil b Federal University of Lavras, Lavras-MG, Brazil c Federal University of Ceará, Fortaleza-CE, Brazil Received 20 December 2004; received in revised form 7 October 2005; accepted 15 October 2005 Available online 19 January 2006 Abstract Wireless sensor networks (WSNs) are a subclass of ad hoc networks with severe resource constraints. These constraints preclude the use of traditional ad hoc protocols, and demand optimizations that incur in solutions specific to a class of applications. This work presents PROC, a protocol designed for continuous data dissemination networks that interacts with the application to establish routes. This mechanism allows the application to reconfigure PROC on runtime. PROC also provides fault-tolerance mechanisms to ensure reliable routes. A performance evaluation in topologies varying from 50 to 200 nodes showed that PROC increases network lifetime around 7% to 12%, and has a higher throughput than both energy-aware data-centric routing (EAD) and a simplified version of TinyOS Beaconing. Furthermore, PROC presents a graceful performance degradation when the number of nodes in the network increases. © 2005 Elsevier Inc. All rights reserved. Keywords: Wireless sensor networks; Routing; Continuous data dissemination; Simulation; Fault tolerance 1. Introduction Wireless sensor networks (WSNs) are a subclass of ad hoc wireless networks, and consist of a large number of sensor nodes, each one equipped with processor, memory, battery, sen- sor devices and transceivers. These nodes send monitoring data to an access point (AP), responsible for forwarding data to the users [1]. Unlike traditional ad hoc networks, it is not possi- ble, in general, to replace or recharge node batteries. This is due to the large number of nodes deployed or inhospitable en- vironmental conditions. Hence, energy conservation is critical in WSNs.  This work was partially supported by CNPq, Brazilian Research Council, under process 55 2111/02-3. Some scholarships were funded by CAPES. Work developed while prof. Nogueira was in sabbatical year at Univ. Paris Pierre et Marie Curie (LIP6) and Univ. Evry, France, supported by CAPES. ∗ Corresponding author. E-mail addresses: damacedo@dcc.ufmg.br (D.F. Macedo), lcorreia@ufla.br (L.H.A. Correia), aldri@dcc.ufmg.br (A.L. dos Santos), loureiro@dcc.ufmg.br (A.A.F. Loureiro), jmarcos@dcc.ufmg.br (J.M.S. Nogueira). 0743-7315/$ - see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.jpdc.2005.10.006 Traditional ad hoc protocols are not applicable to WSNs due to a series of peculiarities of sensor networks [1,3]. First, the number of nodes in a sensor network is much higher than in ad hoc networks, though the bandwidth and the communication range are severely limited. Hence, protocols must interact only with nearby nodes to increase their scalability and efficiency; sensor nodes are more prone to failures and harsh communica- tion conditions, forcing protocols to incorporate fault tolerance mechanisms; nodes might not have unique identifiers, which is a fundamental premise in most protocols for ad hoc networks; finally, sensor nodes might perform in-network processing, operations not conceived in protocols for ad hoc networks. The severe energy restrictions found in sensor networks influence the design of every piece of software running in the network. To increase energy savings, protocols might take advantage of network specific characteristics to optimize their operation, such as event-driven operation [15], node positioning [18], and real-time algorithms [28]. Another tendency in such networks is the tight integration of all protocol layers [11,20]. In WSNs, the application might interact with medium access