Multiuser hybrid analogue/digital beamforming for massive multiple-input–multiple-output

• Published in: IET communications Vol. 10; no. 12; pp. 1464 - 1472
• Main Authors: Wu, Keying, Wu, Lu, Zhang, Jianwen
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 11.08.2016
• Subjects: 64‐antenna system; adaptive signal processing; Algorithms; amplitude resolution; Analogue; analogue‐digital BF matrices; antenna arrays; array signal processing; Beamforming; Channels; Complexity; Design analysis; Digital; discrete phase shifters; effective channel; fully‐connected PSN; full‐digital BF; generalised multilayer architecture; hybrid analogue‐digital BF; ideal phase shifters; implementation complexity; interference suppression; iterative methods; massive multiple‐input‐multiple‐output system; MIMO communication; multiuser hybrid analogue‐digital beamforming; multiuser interference cancellation; performance complexity; phase shifter network; Phase shifters; radiofrequency chain; second‐order channel statistics; simple iterative algorithm; statistical analysis; theoretical analysis; two‐stage BF algorithm; iterative methods; hybrid analogue-digital BF; radiofrequency chain; ideal phase shifters; multiuser interference cancellation; analogue-digital BF matrices; multiuser hybrid analogue-digital beamforming; adaptive signal processing; simple iterative algorithm; phase shifter network; antenna arrays; effective channel; 64-antenna system; fully-connected PSN; discrete phase shifters; massive multiple-input-multiple-output system; generalised multilayer architecture; amplitude resolution; MIMO communication; array signal processing; interference suppression; two-stage BF algorithm; second-order channel statistics; theoretical analysis; phase shifters; implementation complexity; full-digital BF; performance complexity; statistical analysis
• ISSN: 1751-8628; 1751-8636
• DOI: 10.1049/iet-com.2015.0520

The authors propose a generalised multi-layer architecture for the phase shifter network (PSN) in hybrid analogue/digital beamforming (BF), which provides flexible trade-offs between the performance and implementation complexity. By changing the layer number, the authors can adjust the complexity of the PSN and the achievable performance. A two-stage BF algorithm is adopted, in which the analogue and digital BF matrices are designed separately. Analogue BF is adaptive to the second-order channel statistics. A simple iterative algorithm is proposed to maximise an upper bound of the average rate of the effective channel after analogue BF. Digital BF is adaptive to the effective channel for multiuser interference cancellation. Both ideal phase shifters and discrete phase shifters with limited phase and amplitude resolutions are considered in the algorithm design. Theoretical analysis and simulation are used to demonstrate the good performance and flexibility of the proposed technique. In a 64-antenna system, it can use 16 radio-frequency chains to perform very closely to full digital BF with a fully-connected PSN, or achieve 70–80% performance with a simple PSN. It is also robust against the limited phase shifter resolution. It enables us to select the proper performance and implementation complexity according to the requirement and capability of real systems.