This paper investigates uplink rate performance of filter bank multicarrier (FBMC)-offset quadrature amplitude modulation (OQAM) based multi-user (MU) multicell massive multiple-input multiple-output (MIMO) systems. Contrary to existing works in the FBMC literature, channel between users and the base station (BS) within a cell is modelled to be Ricean fading with a deterministic fast fading component and a random Rayleigh distributed component. Closed-form expressions for the ergodic achievable uplink sum rate and corresponding approximation are derived for the maximum ratio combining (MRC) at the BS in the presence of imperfect channel state information (CSI). This is achieved by considering the effect of pilot contamination, and the statistical characteristics of the intrinsic interference in FBMC systems. Uplink power scaling laws with imperfect CSI at the BS are investigated. Analytical results are also developed for analysing the effect of the Ricean-K factor on the achievable uplink sum rate. Numerical examples are presented to demonstrate the tightness between the analysis and simulations, and to compare the performance of FBMC-OQAM and traditional OFDM-based MU multi-cell massive MIMO systems.

In this paper, a printed low‐profile antenna with frequency and pattern reconfigurable functionality is designed in three modes. Each mode operates at different frequency bands and has several options available for pattern reconfiguration in these bands. The proposed antenna consists of eight pin‐diode switches (S1 to S8). The switches S1 and S2, installed in the radiating patch, are used for frequency reconfigurability to control the operating bands of the antenna. The rest of the six switches (S3, S4, S5, S6, S7, and S8), loaded in the stubs on the rear side of the antenna, are used for pattern reconfiguration to control the main lobe beam steering. When all switches are off, the proposed antenna operates in a wideband mode, covering the 3.82‐9.32 GHz frequency range. When S1 is on, the antenna resonates in the 3.5 GHz (3.09‐4.17 GHz) band. When both S1 and S2 are on, the resonant band of the antenna is shifted to 2.5 GHz band (2.40‐2.81 GHz). A very good impedance matching with a return loss of less than ‐10 dB is attained in these bands. The beam steering is done at each operating frequency by controlling the on and off states of the six pin‐diode switches (S3, S4, S5, S6, S7, and S8). Depending on the state of the switches, the antenna can direct the beam in seven distinct directions at 4.2 GHz, 4.5 GHz, and 5 GHz. The main beam of the radiation pattern is steered in five different directions at 5.5 GHz, 3.5 GHz, and 2.6 GHz operating bands for the given state of the mentioned switches. The proposed antenna supports several sub‐6 GHz 5G bands (2.6 GHz, 3.5 GHz, 4.2 GHz, 4.5 GHz, and 5 GHz) and can be used in handheld 5G devices.

This study investigates the uplink performance of offset quadrature amplitude modulation (OQAM)‐based orthogonal frequency division multiplexing (OFDM) waveform in single‐cell multi‐user massive multiple‐input multiple‐output (MIMO) systems over Ricean fading. An uplink training‐based minimum mean square error (MMSE) channel estimation by exploiting the inherent characteristics of OFDM/OQAM waveform is briefly presented. By leveraging the second‐order statistical characteristics of the intrinsic interference, the achievable uplink sum rates and corresponding closed‐form approximations are derived in the presence of MMSE channel estimate at the base station with zero‐forcing (ZF) and maximum‐ratio combining (MRC) receivers. Based on the above analytical results for the uplink rates, power scaling laws are also investigated. The effect of Ricean‐ K factor on the achievable uplink sum rate is also examined analytically for both the MRC and ZF receivers. Numerical results compare the performance of OFDM/OQAM and classic cyclic‐prefix OFDM‐based massive MIMO systems and also validate the various analytical expressions derived in this work.

This paper analyses the performance of filter bank multicarrier (FBMC) signaling in conjunction with offset quadrature amplitude modulation (OQAM) in multi-user (MU) massive multiple-input multiple-output (MIMO) systems. Initially, closed form expressions are derived for tight lower bounds corresponding to the achievable uplink sum-rates for FBMC-based single-cell MU massive MIMO systems relying on maximum ratio combining (MRC), zero forcing (ZF) and minimum mean square error (MMSE) receiver processing with/without perfect channel state information (CSI) at the base station (BS). This is achieved by exploiting the statistical properties of the intrinsic interference that is characteristic of FBMC systems. Analytical results are also developed for power scaling in the uplink of MU massive MIMO-FBMC systems. The above analysis of the achievable sum-rates and corresponding power scaling laws is subsequently extended to multi-cell scenarios considering both perfect as well as imperfect CSI, and the effect of pilot contamination. The delay-spread-induced performance erosion imposed on the linear processing aided BS receiver is numerically quantified by simulations. Numerical results are presented to demonstrate the close match between our analysis and simulations, and to illustrate and compare the performance of FBMC and traditional orthogonal frequency division multiplexing (OFDM)-based MU massive MIMO systems.

This work addresses frequency synchronisation and channel estimation for highly frequency selective orthogonal frequency division multiplexed systems with offset quadrature amplitude modulation. A two‐step approach is proposed, wherein a coarse carrier frequency offset (CFO) estimator, which does not require channel knowledge, is designed in the first step by exploiting the correlation between the received and training signals. A time‐domain model is derived for the joint estimation of fine CFO (FCFO) and highly frequency selective channel in the second step. In contrast to the frequency domain model in the literature, the derived time‐domain model does not require the channel to be frequency flat. Based on the time‐domain model, the weighted least squares and minimum mean square error estimators are investigated to jointly estimate the FCFO and frequency selective channel. The Cramer‐Rao lower bounds (CRLBs) are derived for the proposed estimators, and are used to evaluate the performance of the joint FCFO and channel estimation in the presence of inter‐symbol‐interference due to the overlapping of adjacent time‐domain orthogonal frequency division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) symbols. Simulation results demonstrate achievability of the CRLB bounds and performance gain of the proposed estimators over the state‐of‐the‐art existing estimators.

This paper investigates the zero forcing (ZF) based vertical Bell laboratories layered space-time (V-BLAST) detection in multiple input multiple output (MIMO) filter bank multicarrier (FBMC) systems based on the offset quadrature amplitude modulation (OQAM). Initially, a QR decomposition based convectional ZF-successive interference cancellation (C-ZF-SIC) technique is examined for the detection in MIMO-FBMC-OQAM systems. In order to tackle intense error propagation in the C-ZF-SIC scheme due to the intrinsic interference in FBMC systems, a neighbourhood detection based ZF-SIC (ND-ZF-SIC) technique is proposed that exploits the fact that each symbol in the FBMC-OQAM system interferes only with the symbols within a small neighbourhood. Further, the ND-ZF-SIC scheme based on the sorted QR decomposition (ND-ZF-SQRD) is also investigated for the detection in MIMO-FBMC-OQAM systems. Simulation results demonstrate that the proposed schemes significantly outperform the conventional scheme, and attain a performance similar to that of MIMO-OFDM systems.

We consider two-way amplify-and-forward relaying, where multiple full-duplex user pairs exchange information via a shared full-duplex massive multiple-input multiple-output (MIMO) relay. Most of the previous massive MIMO relaying works maximize the spectral efficiency (SE). By contrast, we maximize the non-convex energy efficiency (EE) metric by approximating it as a pseudo-concave problem, which is then solved using the classic Dinkelbach approach. We also maximize EE of the least energy-efficient user relying on the max-min approach. We also compare SE and EE of the proposed design with existing full-duplex systems and quantify the significant improvement achieved by the proposed algorithm. We also compare EE of the proposed full-duplex system to that of its half-duplex counterparts, and characterize the self-loop and inter-user interference regimes, for which the proposed full-duplex system outperforms the half-duplex ones.

A training-based two-step approach which addresses carrier frequency offset (CFO) and channel frequency response (CFR) estimation in single-input multiple-output (SIMO)-filter bank multicarrier (FBMC) systems based on offset quadrature amplitude modulation (OQAM), is presented. A coarse CFO estimator which does not require the channel knowledge, is investigated in first step. For the combined estimation of fine CFO and CFR in second step, a least squares (LS) estimator based on the conventional interference approximation method (IAM), is proposed. The Cramer-Rao lower bound (CRLB) is derived for the proposed estimator. Simulation results show that the proposed estimator in second step achieves CRLB in the lower signal to noise ratio (SNR) regime. The bit error rate (BER) performance of the proposed approach is also numerically evaluated.

We consider two-way amplify and forward relaying, where multiple full-duplex user pairs exchange information via a shared full-duplex massive multiple-input multiple-output (MIMO) relay. We derive closed-form lower bound for the spectral efficiency with zero-forcing processing at the relay, by using minimum mean squared error channel estimation. The zero-forcing lower bound for the system model considered herein, which is valid for arbitrary number of antennas, is not yet derived in the massive MIMO relaying literature. We numerically demonstrate the accuracy of the derived lower bound and the performance improvement achieved using zero-forcing processing. We also numerically demonstrate the spectral gains achieved by a full-duplex system over a half-duplex one for various antenna regimes.

In this study, the design of a superimposed training (ST) for an interference‐limited spatially correlated multiple‐input–multiple‐output (MIMO) system is addressed and a closed‐form solution for designing the training signal is proposed in a sub‐optimal way. Earlier papers have considered noise limited MIMO systems. The authors also propose random/orthogonal variable spread factor (OVSF) codes as a choice for the ST signal. The mean‐squared error of the channel estimate and symbol error rate performances are obtained through simulation. Considering the power allocation issue between the data and training symbols, a sub‐optimal average training power that maximises the lower bound on the effective signal‐to‐interference ratio is also proposed. Simulation results show that the bit error rate performance of the ST is indistinguishable from the OVSF/random ST sequence.