Analog Beamforming for mmW Circular Arrays with Limited Number of RF Chains

Millimeter wave (mmW) communication has been viewed as a way of offloading users from lower frequencies, where currently deployed cellular networks operate. The short wavelength of mmW frequencies allows for electrically large arrays to be deployed in small mobile devices. Electrically large arrays (in terms of wavelength) are needed in order to compensate for the high signal attenuation in mmW frequencies by means of transmit-receive beamforming. Two beamforming architectures are typically considered in practice, namely a fully digital solution in which every antenna has a dedicated radio frequency (RF) chain, and a so-called hybrid solution that consists of an analog beamforming stage prior to digital beamforming. Hybrid beamforming trades-off the versatility of a fully digital architecture for lower power-consumption and cost. In this paper we focus on fully analog beamforming architectures for circular arrays comprised of patch antennas. In particular, we propose two architectures for analog beamforming with circular arrays, and provide a detailed study regarding the number of simultaneously active beams (i.e, number of RF chains), the amount of antennas per beam, as well as the number of required phase-shifters. The proposed analog beamforming scheme is compared to a fully digital beamforming approach on a realistic 5G system level platform simulating an urban environment. Results show that the performance of the proposed analog beamforming architecture is comparable to that of a fully digital beamforming scheme in terms of user throughput. © 2018 IEEE.