Robust Video Streaming over MANET and VANET

Introduction

We consider video streaming over a wireless Mobile Ad Hoc Network (MANET) and over an extension of the MANET concept, an automotive Vehicular Ad Hoc Network (VANET). Both involve multi-hop routing across infrastructure-less wireless networks. That is wireless communication takes place from node-to-node in the case of a MANET and from vehicle-to-vehicle within a VANET, without routing via a network access point. Multi-hop routing is necessary due to the limited range of wireless communication. Therefore, ad hoc networks are networks in which wireless nodes communicate with each other without any established infrastructure or network core (Manoj & Siva Ram Murthy, 2004). Nodes act as both terminals (i.e. source and destination of the message) and relays for routed messages. In ad hoc networks, messages hop from node to node until they reach their destination, which requires each node to be more intelligent than the conventional terminals found in other wireless networks such as cellular networks. At the same time, their flexibility allows both MANET and VANET to extend cellular networks to where there are coverage gaps or to where there is temporary excessive demand. Therefore, whatever multimedia applications are planned for 3G cellular networks such as 3GPP’s Multimedia Broadcast and Multicast Service (MBMS) (Luby et al., 2007) will be enhanced by extensions to ad hoc networks. In particular, projected applications of MBMS within sport stadiums and airports (Luby et al., 2007), which include multimedia streaming as well as download, may be better delivered by an ad hoc extension to the cellular system to reduce congestion at base stations.

Node mobility causes an ad hoc network’s topology to be in a constant state of flux. Route changes and link failures are the most common problems in communication over ad hoc networks, causing an increase in delay, delay variation (jitter) and packet loss. In these networks, in the absence of a central scheduling node, the nodes must be always available to receive and forward packets even when they are not the origin or destination of transmission. Power management becomes an important issue in MANETs, when appropriate schemes for energy consumption can reduce the effect on and increase the lifetime of battery-powered devices. The energy consumption problem becomes even more severe in multimedia communication, as it has been reported) (Chen et al., 1998) that one third of total energy consumption in a mobile device is due to transmission and video play back together with transmission amounts to about 80% of total power consumption in a receiver. In MANETs, per-packet routing overhead is a metric of power efficiency that helps judge the efficiency of the streaming process.

A MANET will typically be formed by a group of people moving on foot or on vehicles at relatively slow speeds with random patterns of motion. A scenario explored is that of a team of emergency workers coping with a natural disaster, when the existing communication infrastructure has been removed. Real-time video communication will significantly help to describe an emergency scene to other members of the response group. Military applications of ad hoc networks share some similarities with this scenario and equally a video link between members of a platoon will be of value. In addition in a military setting, an ad hoc network is not as easily disrupted as other types of network. The mobility of the group members in a MANET is often described with a random waypoint model (Broch et al., 1998).