Voice over wireless Internet: performance interaction of signal processing algorithms and network protocols

摘要

Internet telephony is anticipated to grow into a major system for voice communication, even more so when it is extended to support wireless and mobile users. This last step is however not straightforward since the insertion of a wireless link generates distinctly new impairments like fading, noise and corruption and loss of packets at the MAC (medium access control) layer. Different techniques to mitigate these voice stream disruptions exist, but they are not directly extendible towards the wireless Internet telephony scenario. We have investigated several of these techniques and focussed on the necessary changes. Our simulations show that a new buffering scheme is needed at the receiver and that several tradeoffs in other parts of the system arise therefrom. This apparent interaction between the different techniques requires a global optimization. Moreover, we show that the optimal settings depend heavily on the wireless load and channel conditions such that the system must be designed to exhibit on-the-fly adaptation capabilities.