Digital Beamforming for Antenna Arrays

With an increasing number of subscribers to the terrestrial cellular and/or satellite based services, and a resultant rise in the demand for the data rate, there is an urgent need of advanced signal processing schemes that improve the power and the spectral efficiencies. Digital beamforming using an array of antenna elements is one such technique. When multiple co-channel signals arrive at an antenna array, the digital beamforming techniques, based on advanced signal processing algorithms, improve the array's Directivity in the direction of the Signal of Interest (SoI) while minimizing the array gain in the direction of the Signals Not of Interest (SNoI). The beamforming weights are estimated either using supervised (non-blind) learning methods or unsupervised (blind) methods. The main focus of this paper is on a survey of the digital techniques of beamforming and identifying/summarizing the merits and the drawbacks of each technique. The objective is to summarize the current state of the art for a judicious selection of a suitable technique for the application of interest.