Most of my research interests have to do with high-frequency communication, which is potentially one of the most disruptive communication technologies. The followings represent my personal view on high-frequency communications:


Near-Field MIMO

As frequency goes up, the time-honored far-field assumption ceases to hold and the wavefront curvature becomes visible. The most interesting property of the near-field propagation is that the degrees of freedom (DOF) is not unity for line-of-sight connection. Our research objective is to identify the relevant problems and resolve them.


Wideband Communications

The whole point of going up in frequency is to utilize more bandwidth. At high frequencies, as the isotropic pathloss becomes unprecedently large, a lot of number of antennas are required to countervail it. Traditional analog array can do the job for narrowband systems, but it cannot for wideband systems; as the bandwidth broadens, antenna gains at frequencies away from the central one where the array is optimized is reduced. This phenomenon, termed beam squint, could make the wideband operation obsolete. To resolve this problem, more sophiscated array architectures should be used. Our research objective is to devise such architectures which can mitigate beam squint.


Smart Surfaces

Poor propagation characteristic of the high frequencies necessitates network densification. Recently, smart surfaces are emerging as a cost-effective solution. Our research objective is to solve fundamental problems on smart surface assisted communication systems.


Revisiting Phased Array Theory

Phased array theory developed in the last century is an oldie but a goodie for analysis of LOS communications. To avoid reinventing the wheel, I think it is a good time to look back.