A smart multi-hop hierarchical routing protocol for efficient video communication over wireless multimedia sensor networks Denis do Ros´ ario ∗ , Rodrigo Costa ∗ , Helder Paraense ∗ , K´ assio Machado ∗ , Eduardo Cerqueira ∗ and Torsten Braun † ∗ Federal University of Para (UFPA), Belem – PA – Brazil † Institute of Computer Science and Applied Mathematics, University of Bern, Bern – Switzerland Email denis@ufpa.br, rodrigo.costa@itec.ufpa.br, {helderp, kassiolsm, cerqueira}@ufpa.br and braun@iam.unibe.ch Abstract—For smart applications, nodes in wireless multimedia sensor networks (MWSNs) have to take decisions based on sensed scalar physical measurements. A routing protocol must provide the multimedia delivery with quality level support and be energy- efficient for large-scale networks. With this goal in mind, this paper proposes a smart Multi-hop hierarchical routing protocol for Efficient VIdeo communication (MEVI). MEVI combines an opportunistic scheme to create clusters, a cross-layer solution to select routes based on network conditions, and a smart solution to trigger multimedia transmission according to sensed data. Simulations were conducted to show the benefits of MEVI compared with the well-known Low-Energy Adaptive Clustering Hierarchy (LEACH) protocol. This paper includes an analysis of the signaling overhead, energy-efficiency, and video quality. I. I NTRODUCTION In a smart Wireless Sensor Network (WSN) [1], the nodes are able to sense environmental conditions in order to plan actions and have a situational awareness of what is happening in the environment and take appropriate decisions. The proliferation of video applications in smart systems and the demand for new multimedia services in sensor network systems, have fostered the development of Wireless Multime- dia Sensor Networks (WMSNs) [2]. The multimedia content has the potential to enhance the level of the collected infor- mation, enable multi-resolution views, and avoid false positive alarms, which are expected in environmental monitoring, smart parking, traffic control, smart city and others [2]. In this context, smart communication protocols and algo- rithms offer a suitable solution to the sensor nodes transferring multimedia data between themselves. Thus, a smart routing protocol is able to improve the energy efficiency, scalability and reliability, and at the same time, enhance the Quality of Service (QoS) and Quality of Experience (QoE) in WMSN applications. The use of a hierarchical multi-hop architecture with hetero- geneous nodes improves the scalability, resilience and energy- efficiency of WMSNs [2]. Where, nodes periodically form clusters, elect a Cluster-Head (CH) and send the sensed data. However, the process of cluster formation should includes a minimal signaling overhead. A cross-layer approach, based on information of physical, MAC and routing layer, must be used to allow the nodes to perceive the network conditions, and thus be able to dynamically plan, adapt, and take appropriate actions to select the routes. However, the current hierarchical protocols for WMSNs, lack a reliable scheme for selecting routes based on network conditions and energy. Energy constraints in WMSNs are even stricter than in WSNs, due to the fact that multimedia content (video stream- ing, image or audio data) creates a huge amount of data to be processed and transmitted. Thus, videos should be sent in a case of an event occurrence. To address these questions, this paper proposes a smart Multi-hop hierarchical routing protocol for Efficient VIdeo communication over WMSN (MEVI) to overcome the draw- backs mentioned above and allow the transmission of multi- media content with QoS/QoE support. MEVI adopt the use of a event-based video transmission and relies on two operational modes to enable the nodes to take appropriate decisions with regard to video retrieval and transmission. The transmitted video will be useful to enhance the level of collected information. In fire detection applications videos can be used to avoid false-positive alarms and show the real impact of the fire in the environment. The main contributions of MEVI are: (i) an opportunistic scheme for cluster formation, by only sending beacon mes- sages; (ii) multi-hop communication between the CHs and Base Station (BS) to assure an energy-efficient communication in large-scale networks; and (iii) a cross-layer scheme to perceive the network conditions and select the routes based on link quality and energy issues. Simulations were carried out to show the impact and ben- efits of MEVI in disseminating video content in WMSNs, for large-scale scenarios in comparison to LEACH protocol. The energy-efficiency and video quality level were analyzed by means of well-known QoE metrics, which are Structural Similarity (SSIM) and Video Quality Metric (VQM). The remainder of this paper is structured as follows. Section II outlines the related hierarchical routing protocols and their drawbacks. Section III describes the proposed routing proto- 2nd IEEE International Workshop on Smart Communication Protocols and Algorithms 978-1-4577-2053-6/12/$31.00 ©2012 IEEE 6530