5G Beamforming.

Abstract

Spectrum is a scarce and expensive resource and thus operators are always looking to get the most bits out of every portion of spectrum they have. This is particularly important within a context of ever growing traffic demand. Maximizing the spectral efficiency, providing a good coverage and fair usage are the main drivers on mobile networks behind optimization procedures in general and adoption of advanced antenna technologies in particular. Beamforming enables directional transmission which is crucial to extend coverage on bands that can apply it, while also improving radiolink quality, reducing interference, and increasing cell capacity by exploiting resource sharing across spatially separated users. This thesis provides a comprehensive account of the principles behind beamforming and its application in 5G networks. It examines the necessity of channel information for beamforming and explores different beamforming techniques in 5G that are used towards beam definition for broadcast and traffic purposes, each with its own advantages and disadvantages. This work explains those beamforming techniques, how they are used and on which scenarios they are most suitable. Field tests were used to exemplify the benefits and drawbacks of each of the presented beamforming methods. SRS-based beamforming showed better results on near and mid cell scenarios, while codebook-based beamforming proved useful for better performance on the cell edge. Beam customization on real time showed also a great improvement on static and walking tests while no clear gain was shown at a driving pace.