Agenda

PhD Thesis Defence

• Thursday, 19 March 2015
• 15:00-16:30
• Aula Senaatszaal

Compressive Power Spectral Analysis

The main focus of this thesis is on the reconstruction of the second-order statistics (including correlations and power spectrum) from digital samples produced by compressive sampling a.k.a. sub-Nyquist-rate sampling. Note that it has been known that compressive sampling offers substantial assistance in sampling rate reduction, which is important when we deal with signals having a very large bandwidth.

What interests us is that there are applications where the sampling still needs to be done at sub-Nyquist rate (due to the high bandwidth of the signal of interest) but where the second-order statistics (instead of the original signal) are of interest. One application is, for instance, spectrum sensing for a cognitive radio network, which is a network where unlicensed radio systems opportunistically search for a currently unoccupied frequency band in the licensed spectrum and then borrow these discovered ?white spaces? to establish a communication link. This spectrum sensing is continuously performed by these unlicensed systems since they have to monitor when the actual owners of the borrowed bands (called licensed users) become suddenly active, in which case the unlicensed radios have to vacate the spectrum. In this application, sampling the signal at sub-Nyquist rate is of interest since the spectral range that has to be sensed is generally very wide. However, note that the unlicensed radio systems are never interested in the original signal of the licensed users occupying the bands to be monitored. This implies that a power spectrum plot describing which frequency bands are occupied together with the amount of power in the occupied bands is more than enough and any efforts to reconstruct the original signal in this application will be overkill. We show that power spectrum reconstruction of WSS signals below the Nyquist rate is possible without any additional constraints on the original signal or the power spectrum.

Other applications are the estimation of directions-of-arrival from more sources than antennas.

Overview of PhD Thesis Defence