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One of the candidates for short burst communication is universal filtering multicarrier (UFMC), which applies filters in each sub-band to reduce intercarrier interference. Compared with the linear phase FIR filter (LPFF), prototyping a nonlinear phase FIR filter (NLPFF) as the UFMC filter can benefit system performance by improving the filter magnitude response. However, the benefit, namely the tradeoff between phase response and better magnitude, is limited in previous NLPFF designs. Aiming at this problem, this paper has done the following works. First, we propose a new measure called sum of symmetric coefficient differences (SSCD) to represent the phase deviation. Furthermore, we propose a constrained least squares design for NLPFF, where constraints are imposed on the SSCD and squared magnitude. The design can be effectively realized under the second-order cone programming (SOCP) framework. Due to the significantly reduced constraint size and enhanced performance tradeoff area, the proposed SOCP-SSCD approach is the most competitive in effectiveness and efficiency. We have demonstrated this advantage by comparing with previous NLPFF methods. Consequently, by applying this method to design NLPFF as a prototype filter in the UFMC system, we have achieved better power spectral density, symbol error rate (SER), and demodulated constellation than previous prototype filters. For the SER indicator, Fig. 6(a) indicates an SNR gain of 1.2dB@{SER=0.001} between the designed NLPFFs and the previous prototype filters. [ABSTRACT FROM AUTHOR]

Filter bank multicarrier (FBMC) systems based on offset QAM modulation (FBMC/OQAM) represent an interesting alternative to the widely used OFDM scheme for machine type communications or cognitive radio. In this paper the performance of FBMC/OQAM systems exploiting a single-tap receiver in frequency-selective Rayleigh fading channels, is analyzed. In particular, the SER and the asymptotic SER (i.e., for a large number of subcarriers) for any prototype filter, is derived. Moreover, a simple closed-form approximate expression of the asymptotic SER is obtained by taking into account, for each active subcarrier, only intersymbol interference terms due to the considered subcarrier and the adjacent subacarriers, and intercarrier interference terms due to the adjacent subcarriers. The numerical results show that the obtained SER expression can predict the actual performance of the system while the asymptotic SER expression provides a useful upper-bound. Moreover, the curves obtained by exploiting the derived simple closed-form approximate expression can be used to predict the asymptotic upper-bound when the considered prototype filter is adopted. [ABSTRACT FROM AUTHOR]

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. • Unlike the CP-OFDM system, FBMC/OQAM offer good time-frequency localization, the key point in 5G systems. • FBMC/OQAM is also sensitive to CFO, which degrades system performance if left uncompensated. • The joint estimation of CFO and CIR in FBMC/OQAM systems is a very important step. • A pilot set that improves the estimation performance over the existing methods. • A low-complexity alternative for estimating the CFO. [ABSTRACT FROM AUTHOR]

Abstract: This study presents an efficient carrier-frequency-offset (CFO) and symbol-timing-offset (STO) estimation algorithm for time-dispersive orthogonal frequency division multiplexing (OFDM) system using a general inter-carrier interference (ICI) self-cancellation scheme. This study takes advantage of the time shift invariant property in the precoded signal to estimate the CFO. The proposed algorithm first stacks the receive time samples spaced by a pre-determined time interval into sample vectors, which can be expressed in a form having a CFO-directed response vector. This CFO-directed structure enables the proposed approach to estimate the CFO by using the multiple signal classification (MUSIC) algorithm in the time domain. Equalization is required before the MUSIC algorithm to remove the scaling factor generated in the signal stacking. Using the CFO estimate, the proposed approach compensates for the frequency error in the receive signal and then estimates the STO by invoking the MUSIC algorithm in the frequency domain. Unlike conventional algorithms, in addition to having a larger CFO estimation range linearly proportional to the precoding order, the proposed approach can easily handle the case of fractional STO. This study presents some statistical analysis of the undesired equalization residues and the mean square error of the perturbed MUSIC algorithm to provide further insights into the proposed approach. [Copyright &y& Elsevier]

The nonlinear echo path resulting from the unwarranted acoustic echo and nonlinear distortion will degrade the echo cancellation performance of a stereophonic acoustic echo cancellation system. Techniques proposed in the literature rely on the assumption of a linear echo path. In this paper, a nonlinear stereophonic acoustic echo cancellation framework is proposed to address the problem of nonlinear distortion in stereophonic acoustic cancellation systems with a better trade-off between convergence and steady-state performance. The proposed approach uses the functional link-based adaptive filtering to deal with the nonlinear distortion in combination with the sub-filter approach to enhance the convergence performance. In addition to that, the convergence analysis of the proposed algorithm is presented in this paper. Simulations carried out using echo return loss enhancement and magnitude squared coherence as performance metrics using speech and colored noise input demonstrate the proposed framework's ability to improve the echo cancellation performance in the presence of distortion. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the Modified Bartlett–Hanning (MBH) window family is used in an OFDM system to reduce the effect of frequency offset on both the parameters i.e., the inter-carrier interference (ICI) and bit error rate (BER). The performance metric of suggested OFDM model with several Nyquist pulse shapes, including rectangular, Bartlett, raised cosine (RC) and better than raised cosine (BTRC) pulse shapes are also evaluated. These pulse shapes are found as members of the MBH pulse shape family, exactly or equivalently. It is observed that the ICI, BER and signal to interference ratio (SIR) of the OFDM system with different MBH pulse shapes are better than BTRC, RC, Bartlett and rectangular pulse shapes. The MBH pulse shape family, where different pulses can be generated by taking numerous values of the pulse shape parameter ‘β’, is providing a consistent advantage over the BTRC pulse shape in terms of ICI and BER in the acceptable range of carrier frequency offset along with better spectral efficiency due to their improved side-lobe levels. The other pulse shapes e.g. second order continuous window (SOCW), phase modified sinc pulse (PMSP) and Frankʼs window are also compared with proposed pulse shapes and found that the MBH family pulse shapes are equally comparable in terms of performance metric used. [Copyright &y& Elsevier]