Beamforming Solutions for Efficient Link Setup and Link Maintenance in mmWave Communication Systems

Abstract: Millimeter wave (mmWave band) technology has gained a lot of attention in 5G communications, due to large amounts of spectrum being available in the mmWave frequency range. However, mmWave links suffer from severe free-space loss and atmospheric absorption. Beamforming, which generates directed beams with strong gain using multiple antennas, is one promising solution towards these challenges. In this thesis, we focus on designing beamforming weights (a codebook) to synthesize a new beam type, referred to as the "Slepian" beam. The width of the Slepian beam is tuneable, which enables the creation of a wider main-lobe with small side-lobes than the conventional Discrete Fourier Transform (DFT) beam. This makes it possible to optimize the beam for some optimization criteria. In particular, the interest is on the optimization of spectral efficiency and outage capacity over the coverage area (i.e., an angular sector). Using the Slepian beam, the angular space can then be quantized into sub-regions, where each sub-region is covered by a shifted version of the beam. Using wider beams to cover wider sub-regions instead of narrower sub-regions reduces the overhead on both the beam tracking and beam sweeping algorithms, with the latter achieving a reduced initial access time. The new codebook is then used for beam sweeping, and the beam sweeping algorithm implemented and evaluated in this work is hierarchical beam sweeping. Simulation results and capacity analysis verify that the proposed codebook design improves spectral efficiency and outage capacity.