Li, A;
Masouros, C;
Sellathurai, M;
(2017)
Analog-Digital Beamforming in the MU-MISO Downlink by use of Tunable Antenna Loads.
IEEE Transactions on Vehicular Technology
10.1109/TVT.2017.2776563.
(In press).
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Abstract
We investigate the performance of multi-user multiple-input-single-output (MU-MISO) downlink in the presence of the mutual coupling effect at the transmitter. Contrary to traditional approaches that aim at eliminating this effect, in this paper we propose a joint analog-digital (AD) beamforming scheme that exploits this effect to further improve the system performance. A jointly optimal AD beamformer is firstly obtained by iteratively maximizing the minimum received signal-to-interference-plus-noise ratio (SINR) in the digital domain, followed by an optimization on the load impedance of each antenna element in the analog domain. We further introduce a decoupled low-complexity approach, with which existing closed-form beamforming schemes can also be efficiently applied. For the consideration of hardware imperfections in practice, we study the case where the analog load values are quantized, and propose a sequential search scheme based on greedy algorithm to efficiently obtain the desired quantized load values. Moreover, we also investigate the imperfect channel state information (CSI) scenarios, where we prove the optimality for closed-form beamformers, and further propose the robust schemes for two typical CSI error models. Simulation results show that with the proposed schemes the mutual coupling effect can be exploited to further improve the performance for both perfect CSI and imperfect CSI.
| Type: | Article |
|---|---|
| Title: | Analog-Digital Beamforming in the MU-MISO Downlink by use of Tunable Antenna Loads |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1109/TVT.2017.2776563 |
| Publisher version: | http://doi.org/10.1109/TVT.2017.2776563 |
| Language: | English |
| Additional information: | This work is licensed under a Creative Commons Attribution 3.0 License. For more information, see http://creativecommons.org/licenses/by/3.0/. |
| Keywords: | MIMO, beamforming, mutual coupling, optimization, imperfect CSI |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10041095 |
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