Abstract
In this work, we propose intrinsic interference mitigating coordinated beamforming (IIM-CBF)-based transmission strategies for the downlink of multi-user multiple-input-multiple-out (MIMO) systems and coordinated multi-point (CoMP) systems where filter bank based multi-carrier with offset quadrature amplitude modulation (FBMC/OQAM) is employed. Our goal is to alleviate the dimensionality constraint imposed on the state-of-the-art solutions for FBMC/OQAM-based space division multiple access that the total number of receive antennas of the users must not exceed the number of transmit antennas at the base station. First, two IIM-CBF algorithms are developed for a single-cell multi-user MIMO downlink system. The central idea is to jointly and iteratively calculate the precoding matrix and decoding matrix for each subcarrier to mitigate the multi-user interference as well as the intrinsic interference inherent in FBMC/OQAM-based systems. Second, for a CoMP downlink scenario where partial coordination among the base stations is considered, the application of coordinated beamforming-based transmission schemes is further investigated. An appropriate IIM-CBF technique is proposed. Simulation results show that when the number of transmit antennas at the base station is equal to the total number of receive antennas of the users, the proposed IIM-CBF algorithm outperforms the existing transmission strategies for FBMC/OQAM-based multi-user MIMO downlink systems. Moreover, we evaluate the performances of the IIM-CBF schemes in the downlink of multi-user MIMO systems and CoMP systems where the total number of receive antennas of users exceeds the number of transmit antennas at the base station. It is observed that by employing the IIM-CBF techniques, FBMC/OQAM systems achieve a similar bit error rate (BER) performance as its orthogonal frequency division multiplexing with the cyclic prefix insertion (CP-OFDM)-based counterpart while exhibiting superiority in terms of a higher spectral efficiency, a greater robustness against synchronization errors, and a lower out-of-band radiation. In the presence of residual carrier frequency offsets, FBMC/OQAM systems provide a much better performance compared to the CP-OFDM-based system, which corroborates the theoretical analysis that FBMC/OQAM systems are more immune to the lack of perfect synchronization. In addition, numerical results with respect to the convergence behavior of the IIM-CBF techniques are presented, and the computational complexity issue is also addressed.
Highlights
As a promising alternative to orthogonal frequency division multiplexing with the cyclic prefix insertion (CPOFDM), filter bank based multi-carrier modulation (FBMC) has received great research attention in recent years
A block diagonalization (BD)based linear precoder has been developed in [13] for the FBMC/OQAM-based multi-user MIMO downlink with space division multiple access (SDMA). It adopts the central idea of BD [14] to mitigate the multi-user interference and uses the zero forcing (ZF)-based approach [10] to deal with the intrinsic interference cancelation for the resulting equivalent single-user transmissions. This algorithm inherits the drawback of the ZF-based scheme such that it fails to achieve a good performance in a symmetric multi-user MIMO downlink setting, where the number of transmit antennas at the base station is equal to the total number of receive antennas of the users
Considering the symmetric single-cell multi-user MIMO downlink setting where the number of transmit antennas at the base station is equal to the total number of receive antennas of the users, we propose to compute the precoding matrix and the decoding matrix jointly in an iterative procedure for each subcarrier
Summary
As a promising alternative to orthogonal frequency division multiplexing with the cyclic prefix insertion (CPOFDM), filter bank based multi-carrier modulation (FBMC) has received great research attention in recent years. We design intrinsic interference mitigating coordinated beamforming (IIM-CBF) schemesa for the FBMC/OQAM-based multi-user MIMO downlink systems and CoMP downlink systems without restricting the configuration with respect to the number of transmit antennas and the number of receive antennas. For CP-OFDM-based multi-user MIMO downlink systems, there have been some publications on coordinated beamforming techniques [19,24] proposed to cope with the dimensionality constraint imposed on BD-based precoding algorithms [14] Inspired by these works, an IIM-CBF scheme for FBMC/OQAM-based systems is developed to alleviate the same dimensionality constraint that all state-of-the-art transmission strategies for FBMC/OQAM-based multi-user downlink settings suffer from. For a matrix A, A(m, n) denotes its (m, n)th entry
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