Parker Huggins - Research

Current Research: Information-theoretic Limits of Shape-constrained Signaling

I am interested in the theoretical foundations and fundamental limits of wireless signaling under "shape" constraints.

The standard results on channel capacity constrain the signaling scheme in very general ways (e.g., bandwidth and power); these results establish the absolute limits of reliable communication. In practice, however, signals are designed to satisfy application-specific requirements, such as envelope variation, peak-to-average power ratio, autocorrelation, and more. Broadly speaking, these constraints impose structure on the shape of admissible waveforms; more abstractly, they restrict the geometry of the underlying signal space.

Motivated by this viewpoint, my current work combines tools from communication/information theory, signal processing, and mathematics to study how various structural constraints affect the limits of reliable communication.

Here is a glance into my work on bounding the power envelope of OFDM signals.

Past Research: Non-coherent Communication using Roots of Polynomials

Most wireless communication links are coherent, meaning the receiver (and often the transmitter, too) uses knowledge of the channel to enable more reliable communication. But acquiring knowledge about the channel is not free: it requires overhead signaling (e.g., pilot signals), which reduces the throughput and wastes energy.

For short-packet transmission, reference overhead can comprise a non-negligible fraction of the total packet and even dominate the information exchange. In this regime, an attractive alternative is non-coherent communication, where the received signal is processed without knowledge of the instantaneous channel state information (no pilots are needed).

This research studied a novel non-coherent technique called binary modulation on conjugate-reciprocal zeros (BMOCZ). The principle of BMOCZ is quite unique: transmit the coefficients of a polynomial whose zeros (i.e., roots) encode the bits. With this approach, convolution corresponds to polynomial multiplication, which preserves the transmitted data zeros, regardless of the channel realization!

Together with my coauthors, I proposed signal processing techniques for BMOCZ to yield robust performance under hardware impairments at the physical layer (e.g., time and frequency offsets). I also analyzed BMOCZ in more conventional communication scenarios, such as uplink OFDMA, where I exploited its autocorrelation properties to design a pilot-free, fixed-PAPR, OFDM-BMOCZ framework.

The bulk of this work is presented in my paper available here; I also have a related GitHub repo here.

A software-defined radio demo of our proposed non-coherent OFDM-BMOCZ framework.

If you are interested in the basic principles of binary MOCZ, read this paper. For more details regarding its practical aspects, take a look at this paper.

See also my slides on MOCZ developed for a group research meeting (downloading and viewing in PPT is recommended):

MOCZ_Presentation_Huggins.pptx