Filter Bank Based Multicarrier Research Articles

A Comprehensive Survey of Candidate Waveforms for 5G, beyond 5G and 6G Wireless Communication Systems

The evolution of global mobile data over the past decades in broadcasting, Internet of Things (IoT), education, healthcare, commerce, and energy has put strong pressure on 3G/4G mobile networks to improve their service offerings. These generations of mobile networks were initially invented to meet the requirements of the above-mentioned applications. However, as the requirements in these applications continue to increase, new mobile technologies such as 5G (fifth generation), 5G and beyond (B5G, beyond fifth generation), and 6G (sixth generation) are still progressing and being experimented. These networks are very heterogeneous generations of mobile networks that will have to offer very high throughput per user, good energy efficiency, better traffic capacity per area, improved spectral efficiency, very low latency, and high mobility. To meet these requirements, the radio interface of future mobile networks will have to be flexible and rationalized the available frequency resources. Therefore, new modulation methods, access techniques and waveforms capable of supporting these technological changes are proposed. This review presents brief descriptions of the types of 5G, B5G, and 6G waveforms. The 5G consists of OFDM including its transmission techniques: generalized frequency division multiplexing (GFDM), filter bank based multi-carrier (FBMC), universal filtered multi-carrier (UFMC), and index modulation (IM). Meanwhile, the 6G covers orthogonal time frequency space (OTFS), orthogonal chirp division multiplexing (OCDM) and orthogonal time sequence multiplexing (OTSM). The networks’ potentialities, advantages, disadvantages, and future directions are outlined.

Joint CFO and highly frequency selective channel estimation in FBMC/OQAM systems

Filter Bank-based Multicarrier with Offset Quadrature Amplitude Modulation (FBMC/OQAM) has been considered as an alternative waveform to the conventional Cyclic Prefix (CP)-based Orthogonal Frequency Division Multiplexing (OFDM). Despite the adoption of variants of the latter in 5G NR, FBMC/OQAM is still at the top of the promising multicarrier modulation waveforms for future generation communication systems. Although it enjoys a number of unique advantages over CP-OFDM, most importantly maximum spectral efficiency and good time-frequency localization, it is also sensitive to Carrier Frequency Offset (CFO), which can cause inter-carrier interference that degrades system performance if left uncompensated. Besides, the presence of CFO prevents accurate channel estimation. In this paper, our goal is to propose joint estimators for the channel impulse response (CIR) and CFO via an approximate Maximum Likelihood (ML) approach. No simplifying assumption is made about the channel delay spread so our results also apply to highly frequency selective channels. One of the novelties is that the estimation procedure is aided by so choosing the pilots as to result in zero intrinsic interference in the absence of impairments. Moreover, to reduce the complexity of CFO estimation, a lighter implementation, based on the truncation of the Taylor series expansion of the exponential term containing the CFO, is proposed. Simulation results demonstrate the superiority of the proposed estimators over existing methods, in terms of both mean squared estimation errors and bit error rate.

Novel filter bank-based cooperative spectrum sensing under practical challenges for beyond 5G cognitive radios

Cognitive radio (CR) technology with dynamic spectrum management capabilities is widely advocated for utilizing effectively the unused spectrum resources. The main idea behind CR technology is to trigger secondary communications to utilize the unused spectral resources. However, CR technology heavily relies on spectrum sensing techniques which are applied to estimate the presence of primary user (PU) signals. This paper firstly focuses on novel analysis filter bank (AFB) and FFT-based cooperative spectrum sensing (CSS) techniques as conceptually and computationally simplified CSS methods based on subband energies to detect the spectral holes in the interesting part of the radio spectrum. To counteract the practical wireless channel effects, collaborative subband-based approaches of PU signal sensing are studied. CSS has the capability to relax the problems of both hidden nodes and fading multipath channels. FFT- and AFB-based receiver side sensing methods are applied for OFDM waveform and filter bank-based multicarrier (FBMC) waveform, respectively, the latter one as a candidate beyond-OFDM/beyond-5G scheme. Subband energies are then applied for enhanced energy detection (ED)-based CSS methods that are proposed in the context of wideband, multimode sensing. Our first case study focuses on sensing potential spectral gaps close to relatively strong primary users, considering also the effects of spectral regrowth due to power amplifier nonlinearities. The study shows that AFB-based CSS with FBMC waveform is able to improve the performance significantly. Our second case study considers a novel maximum–minimum energy detector (Max–Min ED)-based CSS. The proposed method is expected to effectively overcome the issue of noise uncertainty (NU) with remarkably lower implementation complexity compared to the existing methods. The developed algorithm with reduced complexity, enhanced detection performance, and improved reliability is presented as an attractive solution to counteract the practical wireless channel effects under low SNR. Closed-form analytic expressions are derived for the threshold and false alarm and detection probabilities considering frequency selective scenarios under NU. The validity of the novel expressions is justified through comparisons with respective results from computer simulations.

A Tensor-Based Approach to Joint Channel Estimation/Data Detection in Flexible Multicarrier MIMO Systems

Filter bank-based multicarrier (FBMC) systems have attracted increasing attention recently in view of their many advantages over the classical cyclic prefix (CP)-based orthogonal frequency division multiplexing (CP-OFDM) modulation. However, their more advanced structure (resulting in, for example, self interference) complicates signal processing tasks at the receiver, including synchronization, channel estimation and equalization. In a multiple-input multiple-output (MIMO) configuration, the multi-antenna interference has also to be taken into account. (Semi-) blind receivers, of increasing interest in (massive) MIMO systems, have been little studied so far for FBMC and mainly for the single-antenna case only. The design of such receivers for flexible MIMO FBMC systems, unifying a number of existing FBMC schemes, is considered in this paper through a tensor-based approach, which is shown to encompass existing joint channel estimation and data detection approaches as special cases, adding to their understanding and paving the way to further developments. Simulation-based results are included, for realistic transmission models, demonstrating the estimation and detection performance gains from the adoption of these receivers over their training only-based counterparts.

Energy-efficient multi-cell resource allocation in cognitive radio-enabled 5G systems

In this paper, we propose an energy-efficient resource allocation (RA) algorithm in cognitive radio-enabled 5th generation (5G) systems, where the scenario including one primary system and multiple secondary cells is considered. Because of the high spectrum leakage of traditional orthogonal frequency division multiplexing (OFDM), alternative modulation schemes regarded as the potential air interfaces in 5G are analyzed, e.g., filter bank-based multi-carrier (FBMC), generalized frequency division multiplexing (GFDM), and universal filtered multi-carrier (UFMC). Our objective is to maximize the whole energy efficiency of secondary system defined by the ratio of the capacity to the total power consumption subject to some practical constraints. The general formulation leads to a non-convex mixed-integer nonlinear programming problem with fractional structure, which is challenging to solve due to its intractability and significant complexity. Therefore, we resort to an alternate optimization framework to optimize the variables of subcarrier assignment and power allocation, where successive convex approximation (SCA) is employed so that the general formulation is finally transformed into a solvable convex problem. Numerical results validate the effectiveness of the proposed RA algorithm, and the comparison with some existing RA algorithms is conducted. In addition, the performance of using different 5G candidate waveforms in the energy-efficient RA algorithm is also presented and discussed.

Automatic Multicarrier Waveform Classification via PCA and Convolutional Neural Networks

To make up the disadvantages of OFDM-QAM applied in 4G systems, some new non-orthogonal asynchronous PHY multicarrier techniques have been proposed for multiple 5G application scenarios, such as universal-filtered multicarrier (UFMC) and filterbank-based multicarrier (FBMC). Accurate classification of multiple multicarrier waveforms is indispensable in the future wireless communication systems. Here, we propose a new multicarrier waveforms classification system, which utilizes deep convolutional neural networks to classify OFDM-QAM, UFMC, and FBMC-OQAM. Since the classification accuracy is greatly reduced in AWGN environment, principal component analysis (PCA)-based processing method is proposed in this paper to suppress the AWGN and reduce the dimensions of inputs of convolutional neural networks. Amplitude data is used in this paper as input for CNN and shows promise when compared to which uses raw I/Q data as input. The dense channel environment effects including timing errors, carrier frequency offsets, and multi-fading channels are also considered in this paper and our proposed system can obtain the high classification accuracy in noisy channels.

Resource block filtered-OFDM as a multi-carrier transmission scheme for 5G

The fifth generation of mobile communications, which has higher requirements for data rate and spectral efficiency, will be a key technology for future wireless communication systems. Therefore, based on the current spectral division, the use of idle spectra of low-frequency bands is needed to address 5G mobile scenarios. The side lobe in frequency division multiplexing (OFDM), which is widely adopted in 4G, is so high that it produces adjacent channel interference. The addition a cyclic prefix is necessary to resolve such an interference problem; however, this leads to spectral efficiency degradation. Therefore, this study presents a new multi-carrier transmission technique for future wireless communication systems. Intuited by the filter bank based multi-carrier (FBMC) and the universal-filtered multi-carrier (UFMC), we proposed band resource block filtered orthogonal frequency division multiplexing (RB F-OFDM). RB F-OFDM retains the advantages of OFDM; moreover, its sideband has rapid attenuation, its energy is more concentrated, and it can avoid inter-carrier interference (ICI). When adjacent channel interference exists, the performance of RB F-OFDM is better than that of OFDM and UFMC.

Efficient design of prototype filter for large scale filter bank‐based multicarrier systems

This study presents a new property of the filter bank-based multicarrier (FBMC) system. Also, an efficient iterative algorithm for designing the system with a large number of subcarriers and a prototype filter with a very long length are proposed. For the system, the compact from conditions are derived for both the intersymbol interference free and the interchannel interference (ICI) free. Based on these new conditions, the design of the prototype filter is formulated as an unconstrained optimisation problem where the objective function is the weighted sum of the total distortion of the system and the stopband energy. By deriving the gradient vector of the objective function, an efficient iterative algorithm is proposed for finding the solution of the optimisation problem. In addition, an efficient matrix inversion approach is presented to greatly reduce the computational complexity of the iterative algorithm. As a result, it is feasible to design the FBMC system with thousands of subcarriers. The convergence of the iterative algorithm is proved. Computer numerical simulation results with the comparisons to the existing methods are presented. It is shown that the proposed design algorithm is more effective and efficient than the existing methods.

Energy-Efficiency-Based Resource Allocation Framework for Cognitive Radio Networks With FBMC/OFDM

In this paper, we study resource allocation for a multicarrier-based cognitive radio (CR) network. More specifically, we investigate the problem of secondary users' energy-efficiency (EE) maximization problem under secondary total power and primary interference constraints. First, assuming cooperation among the secondary base stations (BSs), a centralized approach is considered to solve the EE optimization problem for the CR network where the primary and secondary users are using either orthogonal frequency-division multiplexing (OFDM) or filter bank based multicarrier (FBMC) modulations. We propose an alternating-based approach to solve the joint power-subcarrier allocation problem. More importantly, in the first place, subcarriers are allocated using a heuristic method for a given feasible power allocation. Then, we conservatively approximate the nonconvex power control problem and propose a joint successive convex approximation-Dinkelbach algorithm (SCADA) to efficiently obtain a solution to the nonconvex power control problem. The proposed algorithm is shown to converge to a solution that coincides with the stationary point of the original nonconvex power control subproblem. Moreover, we propose a dual decomposition-based decentralized version of the SCADA. Second, under the assumption of no cooperation among the secondary BSs, we propose a fully distributed power control algorithm from the perspective of game theory. The proposed algorithm is shown to converge to a Nash-equilibrium (NE) point. Moreover, we propose a sufficient condition that guarantees the uniqueness of the achieved NE. Extensive simulation analyses are further provided to highlight the advantages and demonstrate the efficiency of our proposed schemes.

On Spectral Coexistence of CP-OFDM and FB-MC Waveforms in 5G Networks

Future 5G networks will serve a variety of applications that will coexist on the same spectral band and geographical area in an uncoordinated and asynchronous manner. It is widely accepted that using cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM), the waveform used by most current communication systems, will make it difficult to achieve this paradigm. Especially, CP-OFDM is not adapted for spectral coexistence because of its poor spectral localization. Therefore, it has been widely suggested to use filter bank-based multicarrier (FB-MC) waveforms with enhanced spectral localization to replace CP-OFDM. Especially, FB-MC waveforms are expected to facilitate coexistence with legacy CP-OFDM-based systems. However, this idea is based on the observation of the power spectral density of FB-MC waveforms only. In this paper, we demonstrate that this approach is flawed and show that interference between FB-MC and CP-OFDM systems should be rated on precise estimation of the error vector magnitude. Our analysis, which is confirmed through simulations on both flat and frequency selective channels and software radio implementation, shows that the interference caused by FB-MC waveforms on CP-OFDM receivers is multiple orders of magnitude higher than expected in the literature. Finally, our results show that using FB-MC waveforms does not facilitate coexistence with CP-OFDM-based systems to a high extent.

Adaptive filterbank-based multi-carrier waveform design for flexible data rates

Filterbank-based multicarrier (FBMC) scheme is one of the candidate waveforms to handle possible problems in next-generation communication systems, such as high out-of-band (OOB) emission and large peak-to-average power ratio (PAPR). In LTE (Long Term Evaluation), the frequency spectrum is shared by users with pre-defined bandwidths (i.e., 1,4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz), which is not a flexible solution for users having different data rate demands. Similarly, in conventional FBMC systems, bandwidth is divided into equal subbands. Recent studies on FBMC modulation have not provided an effective remedy for such users. Motivated by this requirement, we propose a novel FBMC waveform design that allows an adaptive bandwidth allocation scheme. Accordingly, users will not be restricted to the specified bandwidth schedules. In the paper, subband-based and subcarrier based filtering models are constructed with polyphase filter structures. The proposed structures are realized analytically and tested through computer simulations for different scenarios.

MIMO Signal Processing in Offset-QAM Based Filter Bank Multicarrier Systems

Next-generation communication systems have to comply with very strict requirements for increased flexibility in heterogeneous environments, high spectral efficiency, and agility of carrier aggregation. This fact motivates research in advanced multicarrier modulation (MCM) schemes, such as filter bank-based multicarrier (FBMC) modulation. This paper focuses on the offset quadrature amplitude modulation (OQAM)-based FBMC variant, known as FBMC/OQAM, which presents outstanding spectral efficiency and confinement in a number of channels and applications. Its special nature, however, generates a number of new signal processing challenges that are not present in other MCM schemes, notably, in orthogonal-frequency-division multiplexing (OFDM). In multiple-input multiple-output (MIMO) architectures, which are expected to play a primary role in future communication systems, these challenges are intensified, creating new interesting research problems and calling for new ideas and methods that are adapted to the particularities of the MIMO-FBMC/OQAM system. The goal of this paper is to focus on these signal processing problems and provide a concise yet comprehensive overview of the recent advances in this area. Open problems and associated directions for future research are also discussed.

An Enhanced QAM-FBMC Scheme With Interference Mitigation

Cyclic prefixed orthogonal frequency division multiplexing (CP-OFDM) has been used as a waveform for mobile communications, but CP-OFDM has weaknesses in an asynchronous heterogeneous network scenario. To overcome the disadvantage of CP-OFDM, a quadrature amplitude modulation (QAM)-filter-bank-based multi-carrier (FBMC) system is proposed to achieve superior spectrum confinement and better spectral efficiency. However, QAM-FBMC has inevitable performance degradation because of interferences from non-orthogonal filters. In this letter, we propose a decision feedback equalization (DFE)-based interference mitigation scheme for the QAM-FBMC system to cancel a residual interference. The interference from the filters of QAM-FBMC influences to other subcarriers and symbols, and it is modeled as an end-to-end system transfer function with para-Hermitian poly-nomial matrix form, equivalently. By spectral factorization of the system transfer function, the system response is transformed into causal, and the receiver detects the symbols successively. This letter describes the spectral factorization method and formulates the feed-forward and feedback filter of the DFE structure with the spectral factor of transfer function. Simulation results show the superiority of the proposed scheme to the conventional QAM-FBMC receiver scheme.

A Layered Detection Algorithm Based on Interference Cancellation for FBMC-QAM

We consider the residual interference problem for a filter bank-based multicarrier with quadrature amplitude modulation under multipath fading channels. In order to handle this problem, we propose a layered detection algorithm based on interference cancellation (IC). In proposed algorithm, we define two thresholds, a selection threshold and a region threshold for efficient IC. According to the selection threshold, we decide whether to apply IC or not, and configure a successive detection region based on the region threshold. Simulation results show that the proposed algorithm provides almost the same bit error rate performance as the orthogonal frequency division multiplexing and the criteria for the proposed thresholds are reasonable.

Inter-cell interference mitigation in multi-cellular visible light communications.

Inter-cell interference hinders multi-cellular optical wireless communication to support various applications. We proposed and experimentally demonstrated a multicarrier-based cell partitioning scheme, combined with frequency reuse, which could be effective in optical communications although it is inefficient in RF wireless communications. For multicarrier-based cell partitioning, Orthogonal frequency division multiplexing-based multiple access (OFDMA) was employed to accommodate multi-cellular optical wireless communications without a large guard band between adjacent cells and without additional RF components. Moreover, we employed filter bank-based multicarrier (FBMC) to mitigate inter-cell interference generated in OFDMA-based cell partitioning due to asynchronous signals originated from RF path difference. By using FBMC-based cell partitioning, inter-cell interference could be effectively mitigated as well as capacity and spectral efficiency were improved about 1.5 times compared to those of OFDMA. Because no cyclic prefix (CP) is required in FBMC, the improvement factor could be increased if there is a large RF path difference between lighting cells. Moreover, it could be a stronger solution when many neighboring cells exist causing large interference. The proposed multicarrier-based cell partitioning combined with FBMC will effectively support visible light communication (VLC)-based localization-based services (LBS) and indoor positioning system by transparently providing trilateration-based positioning method.

Reconfigurable Filter Bank Multicarrier Modulation for Cognitive Radio Spectrum Sharing - A SDR Implementation

Background/Objectives: Cognitive radio is used as promising technologies for dynamic spectrum access and optimization of wireless resources. Under dynamic spectrum access to provide the ability of working any band of frequency based on need, the reconfigurable cognitive radio is designed. Methods/Statistical Analysis: Multicarrier modulation is the feasible method to share the spectrum without interference. OFDM is one of the efficient multicarrier techniques available for the system design. One of the problems in OFDM for spectral sharing is the side band leakage that will inject interference from secondary radio sub carrier to primary radio sub carrier. To avoid this, in this work a Filter Bank based Multi Carrier (FBMC) modulation is used. Findings: Few simulation works are reported for the interference free spectrum sharing by using FBMC. But this work analyzes the real time practical implementation of the interference free dynamic spectrum sharing. Reconfigurable is another important aspect of the implementation which is provided by the Kintex 7 FPGA implementation of the reconfigurable filter bank multicarrier modulation using NI USRP 2943R SDR platform. This FBMC based Transceiver is implemented by using fast Xilink IP cores of FFT and systolic array based FIR filter IP core. The transceiver is realized to produce output for every clock after a fixed latency 240 clocks or 6 microsecond for 40Mz clock rate. This performance is achieved using single clock loop architecture of LABVIEW FPGA tool and the parallel, pipelined architecture realization of IP cores and other building blocks. Applications/Improvements: Experimental study shows that the BER of primary user for the implemented system is better than the OFDM system by the factor of 10 -1 .

Mutual Interference Analysis of FBMC based Return Channel for Bidirectional T-DMB System

In this paper, we investigate an effective scheme for implementing the return channel by exploiting the guard band between orthogonal frequency-division multiplexing (OFDM) blocks for uplink transmission, which enables guaranteeing compatibility with legacy systems. In order to resolve the interference problem between the conventional broadcast channel and the return channel, we employ the filter bank-based multicarrier (FBMC) system. Toward this goal, the mutual interference between the return and OFDM channels is derived as a closed form through numerical analysis. Based on the mutual interference analysis and the channel condition, an adaptive modulation scheme is applied to increase data throughput. Through the simulation, it can be seen that more than 350 (500) kb/s/Channel can be achieved for the channel signal-to-noise ratio (SNR) of 20 dB (30 dB) when the quality of service constraint is lower than a bit error rate of ${\text 10}^-{\text 2}$ ( $10^-{\text 4}$ ). Consequently, the additional throughput above can be achieved in a given resource without the adverse effect to the legacy systems.

Non-orthogonal optical multicarrier access based on filter bank and SCMA.

This paper proposes a novel non-orthogonal optical multicarrier access system based on filter bank and sparse code multiple access (SCMA). It offers released frequency offset and better spectral efficiency for multicarrier access. An experiment of 73.68 Gb/s filter bank-based multicarrier (FBMC) SCMA system with 60 km single mode fiber link is performed to demonstrate the feasibility. The comparison between fast Fourier transform (FFT) based multicarrier and the proposed scheme is also investigated in the experiment.

A survey: Several technologies of non-orthogonal transmission for 5G

One key advantage of 4G OFDM system is the relatively simple receiver implementation due to the orthogonal resource allocation. However, from sum-capacity and spectral efficiency points of view, orthogonal systems are never the achieving schemes. With the rapid development of mobile communication systems, a novel concept of non-orthogonal transmission for 5G mobile communications has attracted researches all around the world. In this trend, many new multiple access schemes and waveform modulation technologies were proposed. In this paper, some promising ones of them were discussed which include Non-orthogonal Multiple Access (NOMA), Sparse Code Multiple Access (SCMA), Multi-user Shared Access (MUSA), Pattern Division Multiple Access (PDMA) and some main new waveforms including Filter-bank based Multicarrier (FBMC), Universal Filtered Multi-Carrier (UFMC), Generalized Frequency Division Multiplexing (GFDM). By analyzing and comparing features of these technologies, a research direction of guiding on future 5G multiple access and waveform are given.

Mitigation of timing offset effect in IM/DD based OFDMA-PON uplink multiple access.

In orthogonal frequency division multiple access based passive optical network (OFDMA-PON) uplink, synchronization between optical network units (ONUs) is very important to maintain orthogonality. The synchronization among uplink signals is considered as one of the main challenges in OFDMA-PON due to optical path difference. In this paper, the performance degradation according to timing offset between ONUs is experimentally analyzed. And we propose and demonstrate timing offset effect reduction in asynchronous multiple access by using CP extension and filter bank based multicarrier (FBMC) system in intensity modulation/direct detection (IM/DD) based OFDMA-PON uplink transmission.