Speech support in wireless, mobile and multihop networks

In this paper, we address the evaluation of speech quality through a wireless network as perceived by the user. User perceived evaluation (in addition to the usual network metrics, including delay, throughput, packet loss statistics etc.) is critical in the design of wireless multimedia networks where speech and video play a key role and are affected by several factors, such as network performance and the encoding scheme. We use two approaches in our evaluation: small scale testbed implementation and hybrid simulation. The testbeds are implemented either by a UDP (User Datagram Protocol) connection or UCLA talk connection. The hybrid simulation is event driven and is based on the Maisie parallel simulation language. It uses speech traces for inputs and plays back the speech outputs off line. There are several advantages in using the simulation tool, mainly from the point of view of scalability and new protocol feature testing. At the same time, the real life testbed provides verification of the simulator assumptions, albeit on a small scale.