Wireless communication systems, particularly code-division multiple access (CDMA) systems, are vital building blocks of the rapidly evolving global information infrastructure. Digital signal processing (DSP) is playing a central role in wireless communications due to the increasingly sophisticated processing required in the physical network layer. The major DSP challenges in CDMA system design stem from three key factors that dominate the processing in the physical layer: (1) channel propagation dynamics; (2) multiaccess interference; and, (3) the inherent complexity of the DSP algorithms. The proposed research has two primary goals for meeting the physical layer CDMA challenges:
* Development of DSP tools and theory to launch an integrated attack on time-varying multipath dispersion, time-varying multipath fading, and multiaccess interference. * Development of design strategies for practical high-performance systems that optimize the complexity versus performance tradeoffs inherent in the DSP techniques.
A new unified framework based on DSP in canonical multipath-Doppler coordinates will be developed to meet these goals. The canonical coordinates are defined by a fixed basis that is derived from a fundamental characterization of channel propagation dynamics in terms of certain discrete multipath delays and Doppler shifts of the signaling waveform. The canonical coordinates naturally connect the key physical layer facets and thus facilitate a unified DSP development. First, all processing relating to propagation effects can be directly performed in the coordinates. Second, the same coordinates provide a canonical subspace-based representation of the desired signal and multiaccess interference. Finally, the simple computation and subspace structure of the coordinates affords a direct handle on complexity. At the heart of the research is a particularly promising innovation: whereas existing interference suppression techniques treat propagation effects as a nuisance, canonical coordinates exploit the subspace structure induced by channel effects for enhanced interference suppression.
The educational objectives of the program include integrated curriculum development in DSP and communications, a thematic approach to teaching to facilitate conceptual thinking, and leveraging of technology to extend the boundaries of traditional instruction and learning.
