Fast 3D Beamforming Technique for Millimeter-Wave Cellular Systems with Uniform Planar Arrays

The beam search protocol in cellular systems requires a significant amount of search time and network resources in order to select a serving base station with the optimal beam pair. In 3D beamforming, the processing time increases significantly because the azimuth and elevation angles need to be considered during beam search. In this paper, we propose a fast 3D beamforming technique for millimeter wave (mmWave) cellular systems with a uniform planar array (UPA). In the proposed technique, the beam search time is reduced significantly by decomposing a UPA into a set of horizontal/vertical uniform linear arrays (ULAs), from which the optimal beam direction in azimuth/elevation angle is obtained. Two types of signals, Zadoff-Chu sequence and linear frequency modulated waveform are used for designing the beam search preamble (BSP), which allows a mobile user to distinguish beams in multi-cell multi-beam environments. The strengths and weaknesses of the two proposed BSPs are analyzed after performing simulation using a simple mmWave cellular system model with UPA. Furthermore, it is demonstrated that the proposed technique significantly reduces the beam search time, i.e., number of beam scans, as compared with the conventional technique.