Filter Bank Multicarrier Signals Research Articles

Joint Sparse Graph for FBMC/OQAM Systems

As an advanced nonorthogonal multiple access (NOMA) technique, the low density signature (LDS) has never been used in filter bank multicarrier (FBMC) systems. In this paper, we model a low density weight matrix (LDWM) to utilize the intrinsic interference in FBMC systems when single-tap equalization is employed, and propose a LDS-FBMC scheme which applies LDS to FBMC signals. In addition, a joint sparse graph (JSG) for FBMC named JSG-FBMC is proposed to combine single graphs of LDS, LDWM, and low density parity-check (LDPC) codes which respectively represent techniques of NOMA, multicarrier modulation, and channel coding. By employing the message passing algorithm, a joint receiver performing detection and decoding simultaneously on the joint sparse graph is designed. Extrinsic information transfer charts and construction guidelines of the joint sparse graph are studied. Simulations show the superiority of JSG-FBMC to state-of-the-art techniques such as OFDM, FBMC, LDS-OFDM, LDS-FBMC, and turbostructured LDS-FBMC.

Waveform comparison and PA nonlinearity effects on CP‐OFDM and 5G FBMC wireless systems

AbstractIn this article, a waveform comparison and power amplifier nonlinearity effects on cyclic prefix orthogonal frequency‐division multiplexing (CP‐OFDM) and 5G filter bank multicarrier (FBMC) wireless systems are presented. The 5 MHz CP‐OFDM and 5G FBMC signals are used in Matlab simulations, while 1.4 and 3 MHz of both signals are used in experiment. It is noted that 1.4 and 3 MHz CP‐OFDM signals have larger side‐lobes in comparison with 5G FBMC signals. The 5G FBMC signals have stepper slope at the edges and very low out‐of‐band leakage.

Experimental demonstration of multi-Gbps multi sub-bands FBMC transmission in mm-wave radio over a fiber system.

The filter bank multicarrier (FBMC) modulation format is considered as a potential candidate for future wireless 5G due to its feature of high suppression for out-of-band emissions, which allows combining multiple sub-bands with very narrow band-gaps, and hence increases the overall wireless transmission capacity. In this paper, we experimentally demonstrate the generation of multi sub-bands FBMC signals at millimeter-wave (mm-wave) for radio-over-fiber (RoF) systems. The designed multi sub-bands FBMC system consists of 5 sub-bands of 800 MHz with inter sub-band gaps of 781.25 kHz. The composite 5 sub-bands FBMC signal is generated with no band-gap between dc to the first sub-band to preserve the bandwidth of the system. Each FBMC sub-band consists of 1024 sub-carriers and is modulated with uncorrelated data sequences. The aggregate FBMC signal is carried optically by externally modulating a free running laser and is converted to millimeter waves (mm-waves) by photomixing with another free running laser at a frequency offset of 53 GHz. At the receiver, the received electrical mm-wave signal is down-converted to an intermediate frequency (IF) and then post-processed using digital signal processing (DSP) techniques. With the use of the simple recursive least square (RLS) equalizer in the DSP receiver, the achieved aggregate data rate is 8 Gbps and 12 Gbps for 16 quadrature amplitude modulation (QAM), and 64 QAM, respectively with a total bandwidth of 4.2 GHz. The system performance is evaluated by measuring error vector magnitude (EVM) and bit error rate (BER) calculations.

Wired-Wireless Converged Passive Optical Network with 4-PAM and Multi-sub-bands FBMC

Future 5G based passive optical networks (PON) are expected as capable of the simultaneous provision of wired and wireless services for multi-users. In this paper, for the first time, we propose and demonstrate the simultaneous delivery of wired 4-pulse amplitude modulation (4-PAM) and wireless multi-sub-bands filter bank multicarrier (FBMC) signals in one wavelength using one laser source for the future 5G PON. The 4-PAM can be used in cost-efficient intensity modulation direct detection (IM/DD) systems and it provides the double bandwidth efficiency compared to conventional on-off keying (OOK). FBMC is considered as a potential candidate for future wireless 5G due to its high suppression for out of band emissions, which allows combining multiple sub-bands with very narrow band-gaps. Using multi-sub-bands with a narrow band gap, the overall transmission capacity can be increased. In the designed system, the composite wired 4-PAM and wireless multi-sub-bands FBMC signal is generated and transmitted with intensity modulation in optical line terminal (OLT). In the optical network unit (ONU) the wired and wireless signals from the received composite signal are extracted using an electrical square band-pass filter and separately demodulated using digital signal processing techniques. The designed 4-PAM has baseband bandwidth of 4.8 GHz and multi-subbands FBMC consists of 4 sub-bands of 500 MHz each, having very narrow inter-sub-bands gap of 488.28 kHz and the aggregate bandwidth of 2.0015 GHz. The bit error rate (BER) has been evaluated for the performance analysis of the 4-PAM and multi-sub-bands FBMC for two cases (a) separate transmission and (b) composite transmission.

Digital Mobile Fronthaul Based on Delta–Sigma Modulation for 32 LTE Carrier Aggregation and FBMC Signals

We first experimentally demonstrated a digital mobile fronthaul (MFH) architecture using delta-sigma modulation as the new digitization interface to replace the conventional common public radio interface (CPRI). Both one-bit and two-bit delta-sigma modulations were demonstrated, and the digitized signals were transmitted over on-off keying (OOK) or 4-level pulse-amplitude-modulation (PAM4) optical intensity modulation-direct detection (IM-DD) links. 32 LTE component carriers (CCs) were digitized and transmitted over a 25-km single-λ 10-Gbaud OOK/PAM4 link, so that 32 LTE carrier aggregation (CA) specified by 3GPP release 13 can be supported. Compared with the conventional digitization interface based on CPRI, the fronthaul capacity is increased by four times. Error vector magnitude (EVM) less than 5% or 2.1% for all LTE CCs was obtained using one-bit and two-bit delta-sigma modulators, so that high-order modulations (256QAM/1024QAM) can be supported. As a waveform-agnostic digitization interface, delta-sigma modulation can digitize not only 4G-LTE but also 5G waveforms, and its 5G compatibility was verified by filter-bank-multicarrier (FBMC) signals. The tolerance to bit error ratio (BER) of the proposed delta-sigma modulation-based digital MFH was evaluated, and no significant EVM degradation was observed for BER up to 3 χ 10−5. A comparison with analog MFH reveals that the proposed digital MFH based on delta-sigma modulation can offer improved resilience against noise and nonlinear impairments, and it increases the fronthaul capacity by four times compared with the conventional CPRI-based digital MFH without significant EVM penalty.

Full-Duplex Quasi-Gapless Carrier Aggregation Using FBMC in Centralized Radio-Over-Fiber Heterogeneous Networks

Filter-bank multicarrier (FBMC) is proposed to demonstrate a full-duplex asynchronous quasi-gapless (only one subcarrier spacing) carrier aggregation for millimeter-wave (MMW) radio-over-fiber radio access technology (RAT) in next-generation 5G heterogeneous mobile-data-network (Het-Net). Fourteen broadband FBMC signals are aggregated with only one subcarrier guard band in the 60-GHz MMW downlink. In the uplink quasi-gapless asynchronous inter-RAT carrier aggregation between 60-GHz MMW and 4G long-term evolution (LTE) signals are also demonstrated. System performances assessment of FBMC and orthogonal frequency-division multiplexing (OFDM) under different operation condition are studied. Our results also show that the FBMC-based new RAT is also backward compatible with existing LTE systems in the Het-Net. Compared with OFDM-based signals with large guard bands, FBMC achieves higher spectral efficiency with better error vector magnitude performance at less received power and smaller guard bands.

Systematic design of transmitter and receiver architectures for flexible filter bank multi-carrier signals

Abstract Multi-carrier (MC) signaling is currently in the forefront of a myriad of systems, either wired or wireless, due to its high spectral efficiency, simple equalization, and robustness in front of multipath and narrowband interference sources. Despite its widespread deployment, the design of efficient architectures for MC systems becomes a challenging task when adopting filter bank multi-carrier (FBMC) modulation due to the inclusion of band-limited shaping pulses into the signal model. The reason to employ these pulses is the numerous improvements they offer in terms of performance, such as providing higher spectral confinement and no frequency overlap between adjacent subcarriers. These attributes lead to a reduced out-of-band power emission and a higher effective throughput. The latter is indeed possible by removing the need of cyclic prefix, which is in charge of preserving orthogonality among subcarriers in conventional MC systems. Nevertheless, the potential benefits of FBMC modulations are often obscured when it comes to an implementation point of view. In order to circumvent this limitation, the present paper provides a unified framework to describe all FBMC signals in which both signal design and implementation criteria are explicitly combined. In addition to this, we introduce the concept of flexible FBMC signals that, unlike their traditional MC counterparts, do not impose restrictions on the signal parameters (i.e., symbol rate, carrier spacing, or sampling frequency). Moreover, our framework also proposes a methodology that overcomes the implementation issues that characterize FBMC systems and allows us to derive simple, efficient, and time-invariant transmitter and receiver architectures.

Evaluation of Clipping Based Iterative PAPR Reduction Techniques for FBMC Systems

This paper investigates filter bankmulticarrier (FBMC), a multicarrier modulation technique exhibiting an extremely low adjacent channel leakage ratio (ACLR) compared to conventional orthogonal frequency division multiplexing (OFDM) technique. The low ACLR of the transmitted FBMC signal makes it especially favorable in cognitive radio applications, where strict requirements are posed on out-of-band radiation. Large dynamic range resulting in high peak-to-average power ratio (PAPR) is characteristic of all sorts of multicarrier signals. The advantageous spectral properties of the high-PAPR FBMC signal are significantly degraded if nonlinearities are present in the transceiver chain. Spectral regrowth may appear, causing harmful interference in the neighboring frequency bands. This paper presents novel clipping based PAPR reduction techniques, evaluated and compared by simulations and measurements, with an emphasis on spectral aspects. The paper gives an overall comparison of PAPR reduction techniques, focusing on the reduction of the dynamic range of FBMC signals without increasing out-of-band radiation. An overview is presented on transmitter oriented techniques employing baseband clipping, which can maintain the system performance with a desired bit error rate (BER).

Unified Framework for the Synchronization of Flexible Multicarrier Communication Signals

This paper presents a unified framework for the formulation of synchronization algorithms dealing with the general class of Filter-Bank Multi-Carrier (FBMC) communication signals. This is a wide family of signaling formats that includes Orthogonal Frequency Division Multiplexing (OFDM), for instance, as just one of many particular cases. One of the main contributions of this work is the proposal of a novel matrix signal model for so-called flexible FBMC signals, in which no restrictions are imposed on the signal design parameters (i.e., pulse shaping, symbol rate, carrier spacing, sampling frequency, etc.), unlike the type of multicarrier signals currently deployed. As an example of application of the proposed matrix signal model, blind joint time-delay and frequency estimators will be derived under both the Conditional Maximum Likelihood (CML) and the low-SNR Unconditional Maximum Likelihood (UML) principles, for any FBMC signal propagating through an arbitrary multipath channel. These estimators will be specialized first for the case of critically sampled cyclic-prefix OFDM (CP-OFDM) signals in frequency flat fading, leading to simple architectures amenable to a hardware implementation. Later on, and for the low-SNR UML principle, the special case of critically sampled CP-OFDM in multipath channels will be addressed, where a novel synchronizer will be proposed.