Filtered Multitone Modulation Research Articles

Analytical Expression for the Bit Error Rate of a Filtered Multitone Modulation Scheme (FMT) through a Multipath Fading Channel

This article proposes a mathematical expression for the calculation of the bit error rate (BER) in a filtered multitone modulation scheme (FMT) when the transmission is carried out through a stationary multipath fading channel, assuming a perfect knowledge of that channel. The numerical results using Monte Carlo simulation are very similar to the results obtained from the proposed mathematical expression, especially when the number of tones is large enough to guarantee a flat behavior of the channel on each tone. The expression applies to any order M of the M-QAM modulation used on each tone.

Filtered Multitone Modulation Underwater Acoustic Communications Using Low-Complexity Channel-Estimation-Based MMSE Turbo Equalization

Filtered multitone (FMT) modulation divides the communication band into several subbands to shorten the span of symbols affected by multipath in underwater acoustic (UWA) communications. However, there is still intersymbol interference (ISI) in each subband of FMT modulation degrading communication performance. Therefore, ISI suppression techniques must be applied to FMT modulation UWA communications. The suppression performance of traditional adaptive equalization methods often exploited in FMT modulation UWA communications is limited when the effect of ISI spans tens of symbols or large constellation sizes are used. Turbo equalization consisting of adaptive equalization and channel decoding can improve equalization performance through information exchanging and iterative processes. To overcome the shortcoming of traditional minimum mean square error (MMSE) equalization and effectively suppress the ISI with relatively low computation complexity, an FMT modulation UWA communication using low-complexity channel-estimation-based (CE-based) MMSE turbo equalization is proposed in this paper. In the proposed method, turbo equalization is first exploited to suppress the ISI in FMT modulation UWA communications, and the equalizer coefficients of turbo equalization are adjusted using the low-complexity CE-based MMSE algorithm. The proposed method is analyzed in theory and verified by simulation analysis and real data collected in the experiment carried out in a pool with multipath propagation. The results demonstrate that the proposed method can achieve better communication performance with a higher bit rate than the FMT modulation UWA communication using traditional MMSE adaptive equalization.

Performance Specifications for the Roll-Off Factor and Filter Order for Filtered Multitone Modulation in the Maritime VHF Data Exchange System

The Maritime VHF Data Exchange System (VDES) will be a basic method of data exchange in the e-Navigation strategy, which has been developed by the International Maritime Organization (IMO) and is an application of the Internet of Things (IoT) in the maritime field. Based on the filtered multitone (FMT) modulation principle of the VDES, we systematically analyzed the effects of the filter parameters on communication performance in FMT modulation. Then, we simulated the influence curve of the roll-off factor and filter order with regard to the communication quality in VDES FMT modulation. Moreover, we performed an experiment using a software-defined radio platform in a real-world scenario. Finally, based on the simulated and real-world results, we recommend performance specifications for the roll-off factor and filter order for FMT modulation in the VDES.

EMC Regulations and Spectral Constraints for Multicarrier Modulation in PLC

This paper considers electromagnetic compatibility (EMC) aspects in the context of power line communication (PLC) systems. It offers a complete overview of both narrow band PLC and broad band PLC EMC norms. How to interpret and translate such norms and measurement procedures into typical constraints used by designers of communication systems is discussed. In particular, the constraints to the modulated signal spectrum are considered and the ability of pulse shaped OFDM (PS-OFDM), used in most of the PLC standards as IEEE P1901 and P1901.2, to fulfill them is analyzed. In addition, aiming to improve the spectrum management ability, a novel scheme named pulse shaped cyclic block filtered multitone modulation (PS-CB-FMT) is introduced and compared to PS-OFDM. It is shown that PS-CB-FMT offers better ability to fulfill the norms which translates in higher system capacity.

Orthogonal Design of Cyclic Block Filtered Multitone Modulation

The orthogonal design of a cyclic block filtered multititone modulation (CB-FMT) system is addressed. CB-FMT is a filter bank modulation scheme that uses frequency confined prototype pulses, similarly to FMT. Differently from FMT, where the linear convolution is used, the cyclic convolution is exploited in CB-FMT. This allows to efficiently implement the system via a concatenation of discrete Fourier transforms. The necessary and sufficient orthogonality conditions are derived in time domain and frequency domain. Then, these conditions are expressed in matrix form, and the prototype pulse coefficients are parameterized with hyper-spherical coordinates. The effect of a linear time-variant transmission medium is discussed. In such a scenario, the optimal filter bank orthogonal design is considered with the objective of maximizing either the in-band-to-out-band sub-channel energy ratio or the achievable rate. Numerical results and comparisons show the performance improvements attainable with several designed optimal pulses also with respect to the use of the baseline root-raised-cosine pulse.

Time Reversal Acoustic Communication Using Filtered Multitone Modulation.

The multipath spread in underwater acoustic channels is severe and, therefore, when the symbol rate of the time reversal (TR) acoustic communication using single-carrier (SC) modulation is high, the large intersymbol interference (ISI) span caused by multipath reduces the performance of the TR process and needs to be removed using the long adaptive equalizer as the post-processor. In this paper, a TR acoustic communication method using filtered multitone (FMT) modulation is proposed in order to reduce the residual ISI in the processed signal using TR. In the proposed method, FMT modulation is exploited to modulate information symbols onto separate subcarriers with high spectral containment and TR technique, as well as adaptive equalization is adopted at the receiver to suppress ISI and noise. The performance of the proposed method is assessed through simulation and real data from a trial in an experimental pool. The proposed method was compared with the TR acoustic communication using SC modulation with the same spectral efficiency. Results demonstrate that the proposed method can improve the performance of the TR process and reduce the computational complexity of adaptive equalization for post-process.

Cyclic block filtered multitone modulation

A filter bank modulation transceiver is presented. The idea is to obtain good sub-channel frequency confinement as it is done by the family of exponentially modulated filter banks that is typically referred to as filtered multitone (FMT) modulation. However, differently from conventional FMT, the linear convolutions are replaced with circular convolutions. Since transmission occurs in blocks, the scheme is referred to as cyclic block FMT (CB-FMT). This paper focuses on the principles, design, and implementation of CB-FMT. In particular, it is shown that an efficient realization of both the transmitter and the receiver is possible in the frequency domain (FD), and it is based on the concatenation of an inner discrete Fourier transform (DFT) and a bank of outer DFTs. Such an implementation suggests a simple sub-channel FD equalizer. The overall required implementation complexity is lower than in FMT. Furthermore, the orthogonal filter bank design is simplified. The sub-channel frequency confinement in CB-FMT yields compact power spectrum and lower peak-to-average power ratio than in OFDM. Furthermore, the FD equalization allows the exploitation of the transmission medium time and frequency diversity; thus, it potentially yields lower symbol error rate and higher achievable rate in time-variant frequency-selective fading.

FMT 변조 기반의 해상 초단파 데이터 시스템의 구현 알고리즘 및 성능분석

본 논문은 해상 초단파 대역에서 데이터 통신이 가능한 FMT(Filtered Multi-Tone) 변조 기반의 디지털 무선전송기술을 소개하고 선박국의 송신기 특성을 기준으로 시뮬레이션 성능과 시스템 시험 결과를 비교 분석하였다. 본 연구에서 CSTDMA(Carrier Sensing Time Division Multiple Access) 방식을 적용하기 위한 프레임 구조와 프로토콜을 도출하였고, ITU-R M.1842-1에 제안된 변조 기술, 스펙트럼 마스크와 지연시간 등의 시스템 특성을 만족하도록 기저대역 모뎀과 RF 송수신단을 구현하였다. 이와 같이 본 시스템은 해상이동서비스용 초단파 대역에서 50kHz-100kHz의 광대역 채널과 디지털 무선전송기술을 도입함으로써 데이터 전송속도를 최대 307.2kbps까지 증가시킬 수 있으며 e-Navigation을 위한 데이터 통신뿐만 아니라 선상에서 로컬 WLAN(Wireless Local Area Network)과 연결하여 다른 데이터 서비스도 쉽게 제공할 수 있다. This paper proposes FMT(Filtered Multi-Tone)-based digital radio implementation algorithms and the results obtained by various field tests especially in terms of transmitter characteristics. In this study, we predefined frame structure and protocols used for the CSTDMA(Carrier Sensing Time Division Multiple Access) scheme, designed digital filters and RF front end to fulfill the system characteristics such as the spectral mask and processing delays given by the Recommendation ITU-R M.1842-1. The proposed system supports exchange of data for e-Navigation with the usage of wider channel of 50-100kHz bandwidth, Turbo coding and FMT modulation. Furthermore, the common Ethernet protocol makes connection to local WLAN(Wireless Local Area Network) on board the ship for other data services.

Multicarrier modulation and cooperative communication in multihop cognitive radio networks

For high-data-rate wireless communication systems, two major issues are the underutilization of limited available radio spectrum and the effect of channel fading. Using dynamic spectrum access, cognitive radio can improve spectrum utilization. Almost all proposed CR systems are based on multicarrier modulation since multiple users can access the MCM systems by allocating subcarriers. Generally, MCM mainly includes two different schemes, orthogonal frequency-division multiplexing and filtered multitone modulation. Considering mutual interference elimination, synchronization, and transmission efficiency, we conclude that FMT is better than OFDM in MCM-based CR systems. Additionally, cooperative diversity can reduce the fading effect since the space diversity gain can be obtained through the distributed antennas of each user. Hence, in this article, we combine CR with the cooperative diversity technique, and then construct three cooperative diversity cognitive models: the collaborative spectrum sensing model, the cooperative communication cognitive model, and the hybrid model. Additionally, radio resources can be extended from time-frequency dimensions to space-time-frequency dimensions in the proposed models, which effectively improves both spectrum utilization and MCM-CR system performance. Finally, extensive simulations are conducted to show the validity and effectiveness of the proposed models.

Design of Orthogonal Filtered Multitone Modulation Systems and Comparison among Efficient Realizations

We address the efficient realization of a filtered multitone (FMT) modulation system and its orthogonal design. FMT modulation can be viewed as a Discrete Fourier Transform (DFT) modulated filter bank (FB). It generalizes the popular orthogonal frequency division multiplexing (OFDM) scheme by deploying frequency confined subchannel pulses. We compare three realizations that have been described by Cvetkovic and Vetterli (1998), and Weiss and Stewart (2000), and Tonello (2006). A detailed derivation of them is performed in the time-domain via the exploitation of different FB polyphase decompositions. We then consider the design of an orthogonal FMT system and we exploit the third realization which allows simplifying the orthogonal FB design and obtaining a block diagonal system matrix with independent subblocks. A numerical method is then presented to obtain an orthogonal FB with well frequency confined subchannel pulses for arbitrarily large number of subchannels. Several examples of pulses with minimal length are reported and their performance is evaluated in typical multipath fading channels. Finally, we compare the orthogonal FMT system with a cyclically prefixed OFDM system in the IEEE 802.11 wireless LAN channel. In this scenario, FMT with minimal length pulses and single tap subchannel equalization outperforms the OFDM system in achievable rate.

Efficient Architectures for Multiuser FMT Systems and Application to Power Line Communications

In this letter we study filtered multitone modulation (FMT) for broadband multiuser power line communications. We address the implementation problem, and we derive a novel efficient digital implementation of both the synthesis and the analysis filter bank. A simple fractionally spaced multiuser receiver is also proposed.

Analytical results about the robustness of FMT modulation with several prototype pulses in time-frequency selective fading channels

In this paper we study the performance of Filtered Multitone (FMT) modulation systems in time-frequency selective fading channels. FMT generalizes the OFDM scheme through the deployment of a sub-channel shaping pulse. A general analysis framework is reported, and it is specialized to the case of using a sine pulse, a root-raised cosine pulse, and Gaussian pulse. Quasi-closed form expressions for the signal-to-interference (SIR) power ratio are derived. The results allow to benchmark the multitone system and understand how robust it is to frequency selective time-variant fading. We make a comparison with OFDM both in terms of SIR and bit-error-rate when single-tap subchannel equalization is used. It shows that FMT can have better performance than OFDM due to the better sub-channel spectral containment. We also discuss the usefulness of the SIR results on the design of the prototype pulse in a time-frequency selective fading channel.

Interference Analysis of Filtered Multitone Modulation Over Time-Varying Frequency- Selective Fading Channels

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We consider in this paper filtered multitone (FMT) modulation over frequency-selective time-varying fading channels. Due to the phase and amplitude distortion introduced by the fading channel, not only is the orthogonality among different subcarriers destroyed, but also the perfect Nyquist sampling condition of the baseband matched filters is no longer valid. Consequently, interchannel, as well as intersymbol, interference will cause distortions to the transmitted signals. In this paper, the interference caused by the channel frequency selectivity and time variance is quantified by analyzing the demodulated signals at the receiver under several different fading-channel conditions. An analysis of the average carrier-to-interference (C/I) ratio of the FMT system is provided in order to demonstrate the underlying tradeoff between spectral efficiency and system performance. For comparison purposes with other multicarrier communication systems (or modulation techniques), the C/I ratio of the conventional orthogonal frequency-division multiplexing system is also provided and compared with that of the FMT system under the same channel conditions and spectral efficiency. Finally, numerical and simulation results are given that confirm the C/I ratio results obtained. </para>

Interference Analysis of Filtered Multitone Modulation Over Time-Varying Fading Channels

Interference Analysis of Filtered Multitone Modulation Over Time-Varying Fading Channels

Performance limits for filtered multitone modulation in fading channels

In this paper, we investigate the best attainable performance for filtered multitone modulation (FMT) in time-variant frequency-selective fading channels when optimal maximum-likelihood (ML) detection is deployed. FMT generalizes the popular orthogonal frequency division multiplexing (OFDM) scheme through the deployment of subchannel shaping filters. The performance limits are derived by extending to this multichannel context the matched filter bounding technique. We first conduct an exact calculation for the average and the distribution of the matched filter error rate bound. Then, we follow a numerical procedure that overcomes the problems of accuracy and ill conditioning in the implementation of the exact method. This study allows for an analytical treatment of the diversity effect on performance as a function of the time/frequency selectivity of the channel. It is found that FMT is a diversity transform that is capable of yielding coding gains and time/frequency diversity gains as a function of the subcarrier spacing and the subchannel filter shape.

Hybrid- tdma/cdma based on filtered multitone modulation for uplink transmission in hfc networks

We present a hybrid TDMA/CDMA system for uplink transmission in multiple access networks that is based on filtered multitone modulation. We consider an application to uplink transmission in hybrid fiber/coax networks. After discussing the characteristics of the proposed system, we address the problem of initial ranging and power adjustment of unregistered stations. Finally, we introduce a new collision resolution algorithm in conjunction with FMT modulation that uses iterative identification of the competing stations to achieve high throughput on the collision channel. System performance is investigated by simulations.

Filtered multitone modulation for very high-speed digital subscriber lines

A filter-bank modulation technique called filtered multitone (FMT) and its application to data transmission for very high-speed digital subscriber line technology are described. The proposed scheme leads to significantly lower spectral overlapping between adjacent subchannels than for known multicarrier techniques such as discrete multitone (DMT) or discrete wavelet multitone. FMT modulation mitigates interference due to echo and near-end crosstalk signals, and increases the system throughput and reach. Signal equalization in an FMT receiver is accomplished in the form of per-subchannel symbol-spaced or fractionally spaced linear or decision-feedback equalization. The problem of channel coding for this type of modulation is also addressed, and an approach that allows combined removal of intersymbol-interference via precoding and trellis coding is described. Furthermore, practical design aspects regarding filter-bank realization, initial transceiver training, adaptive equalization, and timing recovery are discussed. Finally, simulation results of the performance achieved by FMT modulation for very high-speed digital subscriber line systems, where upstream and downstream signals are separated by frequency-division duplexing, are presented and compared with DMT modulation.