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Abstract. Mobile ad hoc networks (MANETs) offer an excellent scenario for deploying communication applications because of the connectivity and versatility of this kind of networks. In contrast, the topology is usually extremely dynamic causing high rate of packet loss, so that ensuring a specific Quality of Service (QoS) for real-time video services becomes a hard challenge. In this paper, we evaluate the effect of using Multiple Description Coding (MDC) and Forward Error Correction (FEC) techniques for improving video quality in a multimedia content distribution system. A hybrid architecture using fixed and wireless ad hoc networks is proposed, which enables the use of multipoint-to-point transmission. MDC and FEC mechanisms can be combined with multipath transmission to increase the network efficiency and recover lost packets, improving the overall Quality of Experience (QoE) of the receiver. Simulations have been analyzed paying attention to objective parameters (Peak Signal to Noise Ratio, Packet Delivery Ratio, Decodable Frame Rate and interruptions) and subjective parameters. Results show that MDC increases the probability of packet delivery and FEC is able to recover lost frames and reduce video interruptions in moderate mobility scenarios, resulting in the improvement of video quality and the final user experience.

Video services are much demanded nowadays but bandwidth and delay requirements of this kind of services are very restrictive. Offering real-time video services in wireless ad-hoc networks is not an easy task because of the difficulty of guaranteeing certain quality in a shared medium. Practical solutions should try to improve communications at (and gathering information from) several layers of the protocol stack. Mobile Ad-hoc Networks are infrastructure-less wireless networks characterized by being very versatile, dynamic and self-organized but also by the difficulty to achieve a good Quality of Service in video transmissions due to packet losses and node mobility. On the other hand, the Wireless Mesh Network is presented as the next step in wireless networks. Wireless Mesh Networks have a hierarchical topology, clustered structure and static backbone, which all help to improve the network stability. In the way towards Wireless Mesh Networks, hierarchical routing protocols could transform an ad-hoc network in a more robust wireless network. Therefore, in this chapter, hierarchical routing protocols have been studied, particularly Hierarchical Optimized Link State Routing Protocol, and compared with a traditional flat routing protocol named Optimized Link State Routing. Furthermore, additional video coding techniques have been used in order to improve video quality in reception. At application layer, results show that Multi-description Coding achieves better quality on video transmissions when nodes have medium or high mobility, especially when using multipoint-to-point transmission or disjoint paths in a hierarchical structure. Video trace simulations have allowed us to perform subjective quality tests to assert the Quality of Experience improvements in video transmissions.

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