Contact-based adaptive granularity for scalable video transmission in opportunistic networks

Video transmission in opportunistic networks is very challenging due to the network coarse characteristics of frequent disruptions and uncertain data delivery. This is on the one hand, and the large size and continuous nature of videos on the other hand. In a previous work of Klaghstan et. al (2013), they presented a solution based on Scalable Video Coding (SVC), which aims at improving the user viewing experience assessed by means of playout delay and perceived quality. While this scheme obtained promising experimental results, it suffered from a non-negligible loss rate, which they explained by the still large size of the used SVC layers as the transmission unit. To address this issue, in this paper we investigate reducing the granularity of transmission units down to Network Abstraction Layer (NAL) units that compose SVC layers. The proposed solution packetizes NAL units into larger chunks in an adaptive way, dynamically taking into account environmental information gathered by each node (contact times with other nodes). Simulation-driven experimental results report a 100% playout availability and a significant improvement in the received quality level with no setback in delivery times.