CAREER: Agile Speech and Audio Coding and Transmission over Heterogeneous Networks

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During emergencies, communication networks are characterized by their high degree of variability in terms of link failure and packet loss. However, current Voice over Internet Protocol (VoIP) methods deliver dissatisfactory performance during emergencies, lacking both the agility to adapt to demanding network conditions, and a systematic framework for measuring voice Quality-of-Service (QoS). The goal of this research is to provide a VoIP framework and methods suitable for demanding network situations. By furnishing methods for achieving voice communication during emergencies or other demanding situations such as distance-learning, this research will provide an immeasurable benefit to society. The highly dynamic nature of channels and networks necessitates cross-layer design approaches in which parameters across all layers of a protocol stack are optimized to efficiently maximize application QoS. To integrate VoIP into a cross-layer design framework, this research offers a new paradigm for speech and audio coding together with several novel error control and transmission methods. In particular, this research provides a functional layering approach to speech and audio coding, breaking up the operation of the coder into three ascending, hierarchical layers: the Waveform Layer, the Statistical Layer, and the Expected Distortion Layer. At the Waveform Layer, a signal is decomposed into perceptually relevant objects whose evolution through time is tracked at the Statistical Layer. Quantization is performed at the Statistical Layer with direction from the Expected Distortion Layer. The Expected Distortion Layer calculates voice QoS for various coder, error-control, and transmission parameter settings, allowing cross-layer optimization based adaptive resource allocation. This paradigm engenders a unique unified model for coding and packet loss concealment, enabling perceptually-adaptive packet protection, transmission, and traffic engineering over time-varying heterogeneous wired and wireless networks.