Insoo Hwang

A holistic view on hyper-dense heterogeneous and small cell networks

The wireless industry has been experiencing an explosion of data traffic usage in recent years and is now facing an even bigger challenge, an astounding 1000-fold data traffic increase in a decade. The required traffic increase is in bits per second per square kilometer, which is equivalent to bits per second per Hertz per cell × Hertz × cell per square kilometer. The innovations through higher utilization of the spectrum (bits per second per Hertz per cell) and utilization of more bandwidth (Hertz) are quite limited: spectral efficiency of a point-to-point link is very close to the theoretical limits, and utilization of more bandwidth is a very costly solution in general. Hyper-dense deployment of heterogeneous and small cell networks (HetSNets) that increase cells per square kilometer by deploying more cells in a given area is a very promising technique as it would provide a huge capacity gain by bringing small base stations closer to mobile devices. This article presents a holistic view on hyperdense HetSNets, which include fundamental preference in future wireless systems, and technical challenges and recent technological breakthroughs made in such networks. Advancements in modeling and analysis tools for hyper-dense HetSNets are also introduced with some additional interference mitigation and higher spectrum utilization techniques. This article ends with a promising view on the hyper-dense HetSNets to meet the upcoming 1000× data challenge.

Digitally Controlled Analog Wideband Interference Cancellation for In-Device Spectrum Sharing and Aggregation

In this paper, we present a feasibility of wideband analog self-interference cancellation with a newly proposed digitally controlled analog adaptive filter. We analyze the key existing issues and concerns in analog interference cancellation and propose novel solutions to cancel the self-interference with a simple 1-tap cancellation circuit. The proposed solution conducts a blind estimation of optimal analog filter coefficients in the digital domain without requiring a pilot signal. We present an end-to-end system analysis and 1-tap adaptive filter circuit analysis to show the feasibility of wideband cancellation. We then propose a few novel blind coefficient estimation algorithms and show their cancellation performance by both simulations and measurements from an actual prototype. The results suggest that our self-interference approach enables the simultaneous operation of the licensed and unlicensed technologies in the adjacent spectrum within a single device, which, in turn, facilitates graceful spectrum sharing and bandwidth aggregation between the licensed and unlicensed technologies.