The Signal Processing Division (also fondly referred to as the DSP Division, because of a penchant for solving problems digitally) works in a variety of areas that involve the manipulation of information-bearing signals. The division comprises both those people who specialise in the transmission of such signals over large distances (Telecommunications) and through complex networks (Network Theory), and those people who are interested in extracting and embedding the information in the signal – whether it be digital data (Digital Communications) or natural-world signals such as speech (Speech Processing) and images (Image Processing).

A visitor looking to find the Signal Processing Division's DSP Laboratory is encouraged to simply follow the rich aroma of freshly-brewed filter coffee, the substance that fuels approximately 30 post-graduate researchers in our well-equipped laboratories. Since so much of our research involves the manipulation of information, the main work area is a large computer network running Ubuntu Linux. The division also maintains three smaller laboratories for specialised equipment and hardware development. Seven full-time faculty members oversee the research effort.

The activities in the Signals Division can be divided into five primary research areas, each with its own projects and staff members.

Contact person: Prof JA du Preez: dupreez@sun.ac.za OR Tel: +27-21-808 4342

Speech is the type of signal humans prefer to use when directly interacting with each other. Consequently, our interaction with computers and other machines can be significantly enhanced if they, too, are able to interpret and generate natural speech. The division's research is focused on developing signal processing and pattern recognition techniques to apply in speech (and also image) processing. Applications include speech recognition, biometrics and telecommunications. The research team makes use of general statistical and syntactic pattern recognition techniques, but has a particular focus on Hidden Markov Modelling (also higher-order and hierarchical techniques) and neural networks. Software development is done mainly in C++ and is deeply rooted in object-oriented design principles.
The division frequently consults for industry. Current and recently completed projects include:

The African Speech Technology DACTS innovation fund project
The Naval Interactive Reference Dictionary
Afrilator: An English-Afrikaans Speech Translator
English-isiXhosa Speech Translation

If you were to walk into the DSP Laboratory now, you would be likely to see people working on related topics, such as speech synthesis, text-to-speech technology, speech recognition, automatic speech translation, speaker identification and verification, speech search tools, and even ways of transforming a speaker's natural voice into a new one.

We have distinguished ourselves internationally in Speech Processing: the American National Institute for Standards and Technology (NIST) hosts various international evaluations/competitions each year to measure the state-of-the-art in various fields. These evaluations draw entries from strong research groups from some of the best known universities and industries worldwide. Since 2002 the Signal Processing Division has taken part in several of these evaluations, primarily in the field of speaker recognition, but also in language identification and spoken topic recognition. We have consistently done well in these evaluations. In 2006 the Stellenbosch team formed part of a consortium with the other partners being Brno University of Technology (Czech Republic) and TNO (Netherlands). This consortium achieved 1st place in the main competition, an honour that had previously always gone to the major American institutions.

Prof JA du Preez, Prof BM Herbst (Department of Mathematical Sciences), Dr TR Niesler, Dr LC Schwardt and Mr HA Engelbrecht are actively involved in the research.

Research partners include the Department of African Languages and Armscor.

Signals need not be only voltages or sounds that change over time – they can also be colours and intensities that change across two- or three-dimensional space. Therefore, the Signals Division also has an interest in processing real-world images, such as handwritten signatures and characters, or photographs and videos of faces and movement. This work is done in collaboration with the Applied Mathematics Research Group, and more details can be found on their website

Prof JA du Preez and Prof BM Herbst (Department of Mathematical Sciences) are actively involved in the research.

Space-based communication systems are particularly interesting and challenging, since they need to be exceptionally robust, operate reliably on low power and on a high-latency link, and cope with Doppler shift and radiation. The Signal Processing Division was involved in two payloads on the Sumbandila Satellite, and is already actively working on subsystems for future South African satellites. Research in this environment gives postgraduate students the opportunity to immerse themselves in the development of a complete communication system – from conceptualisation and budgeting, through design and implementation, up to testing and commissioning a functional space-based communication system. The projects also tend to be collaborative in nature, with researchers working shoulder-to-shoulder with experienced engineers in academia and industry.

Dr R Wolhuter and Dr G-J van Rooyen are actively involved in the research.

Research partners include SunSpace and the Katholieke Universiteit Leuven.

Software-Defined Radio (SDR) is a communications architecture where the bulk of a radio's signal manipulation happens in the digital domain. This is in contrast to the more traditional hardware radios, where modulation, demodulation and filtering are performed exclusively by specialised analogue hardware. An SDR can be an extremely flexible communication system, and a single well-designed hardware platform can be re-used for many different applications. An SDR's functionality can also be upgraded with a simple software update. When such an SDR hardware platform is available, radio system design becomes software development, which allows very rapid development of new radio applications.

For more information, visit the SDR Project's home page. The SDR Project forms part of the Telkom Centre of Excellence at Stellenbosch University.

Dr G-J van Rooyen is actively involved in the research.

Research partners include Telkom, RDI Communications and Armscor.

Getting information from point A to point B is one thing; reliably routing that information from A through B, C, D to Z is a completely different kettle of fish. In this area, the Signal Processing Division studies protocols for data networking, teletraffic modelling, and network topology design. Here the emphasis lies very much on the telecommunications system as a whole, and on how to integrate different technologies into a coherent, reliable network.

Many of the Signal Processing Division's research activities in this field involve improving the performance and reliability of ad-hoc networks and wireless mesh networks. These research projects also tend to be strongly application-driven, such as the deployment of wireless sensor networks for environmental monitoring, managing urban traffic on roads, or developing improved techniques for image streaming over mobile networks.

Work on Network Applications also forms part of the Telkom Centre of Excellence at Stellenbosch University.

Dr R Wolhuter is actively involved in the research.

Research partners include Telkom and Armscor.