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Multicast Voice Transmission over Vehicular Ad Hoc Networks: Issues and Challenges

In this paper we analyze the challenges and issues of transmitting multicast voice streams in a vehicular ad hoc network (VANET). The considered scenario focuses on the multicast transmission of multimedia signals (MP3 streams) between a static and a mobile node. We examine various technical solutions to guarantee vehicle-to-infrastructure connectivity, such as software enhancements and directional antennas. To overcome transmission problems, directions on how to build an optimized client-server streaming software suite are given. The proposed suite is tested with various safety messages in a real-world network testbed. Results of the experiments are presented in terms of both network layer (such as packet loss rate) and application layer (Mean Opinion Score) metrics. Results show how the specific context determines the distribution of error patterns. To improve the performance of the transmission by reducing the average burst error length, block interleaving techniques are taken into consideration. The presented results show that a reasoned choice of the hardware and software parameters enables the transmission of multicast vocal messages by means of the standard 802.11b protocol.