IP Telephony over Mobile Ad Hoc Networks: Joint Routing and Playout Buffering

The last few years have been characterized by a rapidly growing market share of Voice over IP (VoIP) providers against traditional voice service operators, thanks to the low-cost of the packet-based technologies and the reliability of the current (wired) IP networks. We believe that a similar success is expected to happen in mobile ad hoc networks (MANETs), which may offer a good platform for the fast deployment of VoIP mobile networks. However, efforts must be made to improve performance before MANETs can be used for this purpose. One of the main limitations is related to the highly variability of the network topology and channel behavior, which heavily influences the service quality due to route losses and significant delay variations. In this paper, we propose a strategy where these impairments are jointly addressed. The source is responsible for jointly selecting the transmission paths and adjusting the playout delay, with an adaptive inter-talkspurt approach. These tasks are accomplished on the basis of historical data on network connectivity and transmission delays, and are driven by a quality-based approach. The collection of statistics of the network status relies on the QOISR routing algorithm, whereas the voice quality is measured by means of the ITU-T E-Model.