Precoder and equalizer design for multi-user MIMO FBMC/OQAM with highly frequency selective channels

Abstract

In this contribution we propose two new designs of transmit and receive processing for multi-user multiple-input-multiple-output (MIMO) downlink systems that employ filter bank based multicarrier with offset quadrature amplitude modulation (FBMC/OQAM). Our goal is to overcome the limits on the channel frequency selectivity and/or the allowed number of receive antennas per user terminal that are imposed on the state-of-the-art solutions. In the first method the design of precoders and equalizers is iterative and minimum mean square error (MMSE) based. The second is a closed-form design based on the signal-to-leakage ratio (SLR). Via numerical simulations we evaluate the performance of both methods and demonstrate their superiority over two other approaches in the literature.Index Terms-FBMC/OQAM, multi-user MIMO downlink, precoding INTRODUCTIONFilter bank based multi-carrier modulation (FBMC) is widely known as a promising alternative to orthogonal frequency division multiplexing with the cyclic prefix insertion (CP-OFDM). Thanks to the use of spectrally well-contained synthesis and analysis filter banks at the transmitter and at the receiver [1, 2], FBMC features a concentrated spectrum and a much lower out-of-band radiation compared to CP-OFDM. Consequently, it is beneficial to choose FBMC over CP-OFDM for asynchronous scenarios [3,4], or to achieve an effective utilization of spectrum holes [5,6]. Moreover, in systems where filter bank based multi-carrier with offset quadrature amplitude modulation (FBMC/OQAM) is employed, the insertion of the CP is not needed as in CP-OFDM based systems, leading to a higher spectral efficiency.To exploit the benefits of both this advanced multi-carrier scheme and the multi-user downlink with space division multiple access (SDMA), there have been several proposals in the literature that shed light on appropriate designs of transmission strategies for FBMC/OQAM based multi-user downlink settings. Most of these state-of-the-art solutions rely on the assumption that the channel on each subcarrier can be treated as flat fading. Among them, the spatial Tomlinson Harashima precoder in [7] allows only one receive antenna at each user terminal and is more prone to a high computational complexity compared to linear precoders. On the other hand, a block diagonalization (BD) based linear precoder has been developed in [8] for the FBMC/OQAM based multi-userThe authors gratefully acknowledge the financial support by the European Union FP7-ICT project EMPhAtiC (http://www.ict-emphatic.eu) under grant agreement no. 318362. MIMO downlink. It adopts the central idea of BD [9] to mitigate the multi-user interference (MUI) and then uses the zero forcing based approach [10] to deal with the intrinsic interference cancellation for the resulting equivalent single-user transmissions. Furthermore, the coordinated beamforming based transmission strategies devised in [11,12] have the advantage of alleviating the dimensionality constraint such that the number of receive antennas is not restricted. Nevert...

Intrinsic interference suppressed FBMC QAM for MU-MIMO systems in computing and communications

“…Even though FBMC/OQAM provides perfect synchronization because of its excellent feature of localization, intrinsic intrusions occur every time in the complex domain because of a lack of orthogonality. For the FBMC OQAM system, the coordinated beamforming permits the transmission of the signal along with the multiuser MIMO (MU-MIMO) system that is proposed by Cheng et al (2015) to minimize the intrinsic intervention. A partially approximated interference cancellation strategy with a low-complexity Viterbi detector is introduced in the study by Zakaria and Le Ruyet (2016).When compared with the traditional auxiliary pilot channel estimation technique, the proposed channel estimation approach introduced in the work by Choi et al (2017) shows enhanced performance in terms of power efficiency as well as intrinsic intervention.…”

“…Even though FBMC/OQAM provides perfect synchronization because of its excellent feature of localization, intrinsic intrusions occur every time in the complex domain because of a lack of orthogonality. For the FBMC OQAM system, the coordinated beamforming permits the transmission of the signal along with the multiuser MIMO (MU-MIMO) system that is proposed by Cheng et al (2015) to minimize the intrinsic intervention.…”

Single-Tap Precoders and Decoders for Multiuser MIMO FBMC-OQAM Under Strong Channel Frequency Selectivity

“…Through an iterative algorithm, the work of [12] alleviates the dimensionality constraint of [11] by allowing designs where the total number of receive antennas of the users exceeds the number of transmit antennas at the base station. In [13], [14], multi-tap precoders and decoders are iteratively and jointly designed. Moreover, the work originally devised for the SISO case in [3] and later extended for the MIMO case in [15], [16] proposes instead a parallel multi-stage processing architecture DRAFT Fig.…”