Date of Award

Summer 2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical and Computer Engineering

First Advisor

Dennis W Brylow

Second Advisor

Michael T Johnson

Third Advisor

Richard J Povinelli

Comments

This thesis presents a real-time framework for resource-constrained devices that improves the listening quality of Voice over Internet Protocol calls transported over congested networks. Many VoIP standards and implementations exist, but gaps in the design space encourage further exploration that previous work fails to address. We describe an experimental hardware platform that expands upon a previous design to accommodate technical research and educational needs. Our framework, based on the Real-Time Transport Protocol, integrates closely with existing software constructs available in the Embedded Xinu operating system. We oer features derived from RTP by means of a kernel device that alleviates an application from directly interacting with the underlying protocol. An example application based on Xinu's RTP implementation demonstrates measurable robustness to packet loss and delay variation (jitter)|adverse conditions affecting networks used for VoIP, such as the Internet. Results show that Xinu RTP improves PESQ MOS over the previous design limited to UDP transport. Typically, we observe a 17% to 25% increase in MOS for lost packets and near perfect scores for delay variations within the device's sliding window. Moreover, these improvements are possible with minimal computational overhead.