MULTIPATH ROUTING WITH LAYERED CODED VIDEO TO PROVIDE QoS FOR VIDEO-STREAMING OVER MANETS V. Carrascal Frías 1 , G. Díaz Delgado 1,2 , M. Aguilar Igartua 1 1 Telematics Engineering Department, Technical University of Catalonia (UPC), Spain 2 Faculty of Informatics, Queretaro State University (UAQ), Mexico {victorcf, gdiaz, maguilar@entel.upc.edu} Abstract: Feasible video-streaming applications require end-to-end Quality of Service (QoS) from the underlying transmission networks. However, providing end-to-end QoS over Mobile Ad hoc Networks (MANETs) poses a specially challenging problem because of the inherent dynamic characteristics of these networks. In this paper we propose a cross-layer QoS-provisioning algorithm that uses information collected at different layers of the network’s protocol stack. Besides, we develop a multipath routing scheme based on the Dynamic Source Routing (DSR) protocol to provide multiple source-to-destination loop-free paths. We have analysed the multipath design focusing on the load-balancing benefits and the video frame losses. The proposed algorithm shows to improve the performance of video-streaming applications over ad hoc networks. Keywords: Mobile Adhoc networks, Multipath QoS-aware Routing Protocol, End-to-end QoS provision, Video- streaming. I. INTRODUCTION Mobile Ad hoc NETwork (MANET) is a communications network formed spontaneously by a set of wireless mobile devices that are capable of communicating with each other in a peer-to-peer basis, without the need of any fixed network infrastructure or centralized administrative support. Besides, because the transmission range of wireless network devices is limited, several intermediate hosts may be needed by one host to transfer data to another one across the network. Thus, in an ad hoc network, each node could operate as a host or as a router. Mobile nodes are free to move arbitrarily, producing frequent changes in the network topology. Also, the radio channel vagaries and node’s power limitations may produce frequent changes in topology and connectivity. Consequently, MANETs should adapt dynamically to be able to maintain on-going communications in spite of these changes [1]. MANETs are mainly useful in military and other tactical applications such as emergency rescue or exploration missions. On the other hand, commercial applications (i.e. conferences, course training, lectures, museum visits, city tours, peer-to-peer applications, e-gaming, etc.) are likely where there is a need for ubiquitous communication services. Quality of Service (QoS) provision on MANETs remains an open issue and poses a very interesting challenge. Specifically, the real time services need special attention because the dynamic nature of these networks makes difficult to apply traditionally QoS management, even if some IntServ and DiffServ techniques could still be used [2]. Since QoS does not depend on any single network layer but on the coordinated efforts from all layers, it is necessary to develop dynamic solutions, based on a cross-layer approach, that take into account different ad hoc networks specificities [3], [4]. A proper QoS-aware architecture for ad hoc networks should make sure the cooperation among all the components related to QoS provision to support QoS, e.g. signalling, routing and Medium Access Control (MAC) mechanisms. We will focus our work on video-streaming applications over MANETs trying to improve the performance in multi-user situations. The rest of the paper is organized as follows. Section II offers a discussion about multipath routing. Section III presents our QoS-aware algorithm. The multipath routing scheme is explained in Section IV. Simulation results are shown in Section V. Finally, Section VI summarizes the paper and presents future work. II. MULTIPATH ROUTING There are several proposals of routing protocols exploiting path diversity in ad hoc networks. Many of them are modifications or extensions of unipath routing protocols such as AODV (Ad hoc On-Demand Distance Vector) or DSR (Dynamic Source Routing). In general, ad hoc routing algorithms have the ability to discover more than just one path, if they exist. This is mainly due to the broadcast characteristic of the wireless interfaces and to the flooding mechanisms used for path discovery. Unipath ad hoc routing protocols enable and maintain just one path for data transmission between sender and receiver (usually the shortest path with respect to a specific metric or set of metrics). On the other hand, multipath routing protocols try to find several (or all the possible) paths existing during the discovery phase between sender and receiver (again, based on certain metric or set of metrics). Multipath routing protocols are of greater interest in finding every path between both source and destination hosts. This is important to avoid possible critical points of failure. Multiple paths between sender and receiver can robust the network by permitting a rapid path recovery in case of failures. Path diversity makes also possible to manage applications which require some minimum resources that can not be provided by just one path (e.g. bandwidth), by transmitting data through several paths simultaneously from source to destination. In addition, multipath routing can enable load balancing mechanisms, which is an important feature for multimedia applications over MANETs. This way, applications can obtain better A