Digitally assisted analog beamforming for millimeter-wave communication

This paper addresses the research question on how digital beamsteering algorithms can be combined with analog beamforming in the context of millimeter-wave communication for next generation (5G) cellular systems. Key is the use of coarse quantisation of the individual antenna signals next to the analog beamforming. The extreme case of single bit quantization is analyzed. Direction-of-Arrival (DoA) estimation, being the crucial element in beamsteering, is only slightly deteriorated compared to DoA estimation based on full precision (analog) signals. For Signal-to-Noise Ratios (SNRs) below 0 dB, single bit quantization introduces ~2 dB noise level increase. For SNRs beyond 0 dB, the standard deviation of the DoA estimate, levels out to below 10⁻⁴ radian in our specific case study. An additional correction called the Van Vleck correction, mitigates the effects of single bit quantization. This effect can clearly be seen in case multiple signals impinge on the array. When using this correction, the probability of correct detection of multiple sources (in this paper we use 2 sources) is comparable to the performance of an analog system. We therefore conclude that digital beamsteering can effectively and efficiently be combined with analog beamforming.