EARS: Collaborative Research: Blind Source Separation with Integrated Photonics

Louisiana State University, Baton Rouge LA

Investigators

Abstract

The radio world, when viewed through a single antenna, appears as a movie with just one pixel. Multi-antenna systems could reveal the complete radio world in hi-def; however, the astounding quantity of data they generate is simply impossible for electronic computers to handle fast enough. At the same time, the signals received by different antennas are largely redundant, so the first step is generally to combine them in an intelligent way that destroys the undesired and redundant information. Optical (i.e. photonic) physics are extremely broadband and have special properties making them well-suited to multi-antenna problems. Signals carried by light can be very efficiently combined, enabling a photonic processor to funnel the signals from many antennas down to just one information-rich signal that is more manageable for the following electronics. One well-known approach for "intelligently" combining signals is called blind source separation (BSS). BSS is the most powerful technique for pulling apart radio signals that have been mixed over the air. In other words, BSS can use statistics to separate an interesting signal from an interfering signal without assuming anything about them. This project will develop a photonic approach to BSS. Combined, photonics and blind source separation could allow radio systems to better understand and share the wireless spectrum. The objective of the proposed research is to develop a blind source separation technique by using an integrated photonics approach, thereby realizing radio-frequency interference cancellation while preserving user privacy. The project's intellectual merit stems from its orthogonal approach to the challenges of radio access, crossing disciplines of optical physics, statistical analysis, and emerging technology. Spectrum monitoring - an important tool for maintaining harmonious spectrum usage - poses a threat to users' privacy. The project will investigate "blind" spectrum monitoring techniques that can discard the signals of law-abiding users without looking at the content of their data. Science services, such as Earth exploration and radio astronomy, could benefit from format-independent techniques for resolving natural signals through the increasingly loud and complex din of man-made wireless communications. Determining how to intelligently discard undesired information presents a novel theoretical challenge. One pillar of the project will be developing algorithms to bridge the gap between optical hardware and statistical analytics by synthesizing multiple measurements of statistical invariants. A strong experimental thrust to design, build, and demonstrate will validate theoretical insights. A project goal will be the development of hardware that is compatible with recent trends in photonic integration and manufacturing. Foundry compatibility is a key step towards eventual products affordable to the general public.