Cross–Layer Design And Optimization For Multimedia Applications In Critical Environments.

Abstract

Ad Hoc mobile networks are wireless networks which do not rely on any centralized infrastructure to achieve networking tasks. Nodes are free to move in an arbitrary way and this makes the network topology dynamic and unpredictable. These features offer big hopes but at the same time add new challenges. When looking to the flexibility offered by ad hoc networks, we will definitely think that allowing multimedia applications on such networks is a very motivating trend. However, such applications are more demanding while those networks are very constrained and poor comparing to conventional networks. In this research, we investigate a way to offer QoS support for VoIP traffic in ad hoc networks. The traditional design way which is respectful to the layered architecture is not sufficient because this architecture was tailored for a different environment and the limitations of ad hoc networks require new and more flexible architecture. Therefore, the new tendency to break layering principles by allowing stronger interactions and joined protocol design is more appropriate in our case. We resorted to Cross Layer Design for VoIP traffic support improvement in ad hoc wireless networks as a way to escape the big limitations imposed by these networks. We chose VoIP as a multimedia application which is having a big growth these last years. Multimedia applications commonly employ the UDP transport protocol which is insensitive to the network conditions. As a result, such applications can severely degrade the network performance and starve other traffics without getting the expected service themselves. To cop with this fact we proposed a stronger association between the MAC layer, the network layer and the application. We also believe that the proposed solution must not add big loads on the network’s or the node’s capacities to not get inversed effect. Therefore we propose a lightweight solution we called EFORTS (every node feedback for optimizing real time applications support in ad hoc mobile networks). EFORTS is a cross layer design which aims to optimize real time applications support in MANETs without adding important loads on those networks. It consists of better interactions between MAC, routing and application layers. We studied the performance of our proposal through simulations under ns2.