They can relate to new system proposals or existing infrastructure. The study of tradeoffs involved in choosing between equalization or coding to correct certain channel impairments on communication channels, or on recording channels modeled as communication channels, is part of this work. The search for constrained block codes that provide coding gain is of particular relevance to magnetic recording. The latter modulates the solar wind, a flux of energetic charged particles capable of inducing damagingly high voltages on long ocean cables our in expensive communication satellites. Prediction of this phenomenon would enable advance action to prevent damage.
Wavelet research is another active area.
One of the pioneers of the theory of wavelets, Ingrid Daubechies , was a member of our department for a number of years. While she was here, she worked on orthonormal bases of compactly supported wavelets, the work that spurred a wide use of wavelets in signal compression. More recently, we have been involved in the work on local trigonometric bases and their use in signal processing as well as in the lifting scheme, a new technique for constructing second generation wavelets. Other work in this area includes transform methods for multiple-description source coding, and geometry processing, a general attack on description, compression and filtering of surfaces in three dimensions. More details on any of these topics can be found on the Bell Labs Wavelet Home Page .