Filter Bank Multicarrier With Offset Quadrature Amplitude Modulation System Research Articles

Cyclic Shift Based Tone Reservation PAPR Reduction Scheme with Embedding Side Information for FBMC-OQAM Systems

The tone reservation (TR) scheme is an attractive method to reduce peak-to-average power ratio (PAPR) in the filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) systems. However, the high PAPR of FBMC signal will severely degrades system performance. To address this issue, a cyclic shift based TR (CS-TR) scheme with embedding side information (SI) is proposed to reduce the PAPR of FBMC signals. At the transmitter, four candidate signals are first generated based on cyclic shift of the output of inverse discrete Fourier transform (IDFT), and the SI of the selected signal with minimum peak power among the four candidate signals is embedded in sparse symbols with quadrature phase-shift keying constellation. Then, the TR weighted by optimal scaling factor is employed to further reduce PAPR of the selected signal. At the receiver, a reliable SI detector is presented by determining the phase rotation of SI embedding symbols, and the transmitted data blocks can be correctly demodulated according to the detected SI. Simulation results show that the proposed scheme significantly outperforms the existing TR schemes in both PAPR reduction and bit error rate (BER) performances. In addition, the proposed scheme with detected SI can achieve the same BER performance compared to the one with perfect SI.

New scheme for PAPR reduction in FBMC-OQAM systems based on combining TR and deep clipping techniques

Filter bank multi-carrier with offset quadrature amplitude modulation (FBMC-OQAM) system is a very efficient multicarrier modulation technique for 5G, but it suffers as all multicarriers designs from large peak-to-average power ratio (PAPR). Tone reservation (TR) is a method designed to solve this problem by reserving several subcarriers called tones in the frequency domain to generate a cancellation signal in the time domain to eliminate high peaks. In this paper, we suggest a serial combination of tone reservation (TR) method with an enhanced version of clipping called deep clipping (DC) method (TR&DC) to enhance the peaks (PAPR) mitigation in FBMC-OQAM signal model without significantly impacting the quality of transmission. Numerical results and analysis show that the new TR&DC approach allows better overall performance and offers remarkable gain in term of PAPR mitigation than the TR method, with similar BER performance to TR over additive white gaussian noise channel and Rapp HPA model.

A Hybrid Scheme for Low PAPR in Filter Bank Multi Carrier Modulation

The demand for more bandwidth is increasing day by day due to explosive growth in data generated on account of services enabled on mobile phone, laptops and IOT devices. In the near future Internet for everything (IoE) technology where social media, processes, big data etc. will require internet connectivity all the times. Filter bank multicarrier with offset quadrature amplitude modulation system (FBMC/OQAM) is one of the promising techniques for next generation wireless communication system (5G). In FBMC-OQAM orthogonality condition is relaxed to obtain, better bandwidth utilization. This FBMC-OQAM is a multi-carrier transmission scheme where sub-carriers are independent to each other in time domain. The composite signal has large variation in amplitude, thus lead to peak to average power variation problem. This paper presents a FBMC scheme based on DFT spread and identically time shifted multicarriers (ITSM) conditions. In the chosen scheme DFT and IDFT is performed once and system behave as a nearly single carrier. This paper also deals with, PAPR reduction scheme. The chosen scheme is based on clipping and non-liner companding scheme, and obtained results are compared with recently proposed method.

Novel RAPF scheme and its performance of PAPR reduction and BER in FBMC‐OQAM system

Filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) has gained significant importance as a contender for the fifth generation mobile communication system and also meets the application requirements of the Internet of things. The peak-to-average power ratio (PAPR) of the FBMC-OQAM is very high due to using a same prototype filter for each subcarrier and the addition of different subcarriers at the transmitter. Therefore, a novel randomly assigning prototype filter (RAPF) method is proposed to reduce PAPR in FBMC-OQAM system. Based on the proposed RAPF method, the authors analyse the performances of both PAPR and bit error rate (BER) in the FBMC-OQAM system. Simulation results show that the proposed RAPF method helps to significantly reduce PAPR of FBMC-OQAM system. Meanwhile, compared with conventional FBMC-OQAM system, the proposed RAPF-FBMC-OQAM scheme has almost the same BER performance in the additive white Gaussian noise channel but is descended slightly only in the high signal-to-noise ratio region of the frequency selective fading channel.

Nonlinear Complex Support Vector Regression for Fading Channel Estimation in FBMC-OQAM System

Most channel estimation techniques for orthogonal frequency division multiplexing system are not directly applicable to filter bank multi-carrier with offset quadrature amplitude modulation (FBMC-OQAM) system because of the imaginary interference of FBMC-OQAM system. Thus, a novel support vector regression (SVR) algorithm for fading channel estimation in FBMC-OQAM system is proposed. We propose a nonlinear complex SVR algorithm (NCSVR) adapted to two auxiliary pilots (AP)-based FBMC-OQAM signal, namely as AP-NCSVR. The practicality of our method is proved by simulation results obtained for Jakes fading model and vehicular A model. Simulation results reveal the accuracy of the proposed AP-NCSVR algorithm to estimate channel frequency response coefficients and show that the bit error rate performance of the proposed AP-NCSVR algorithm is better than the conventional interpolation method for Jakes fading model and vehicular A model.

Compressive Sensing-Based Channel Estimation for FBMC-OQAM System Under Doubly Selective Channels

Filter-bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) has been considered as an alternative scheme to orthogonal frequency division multiplexing (OFDM). However, the traditional channel estimation techniques of the OFDM cannot be directly applied to the FBMC-OQAM system because of the real-field orthogonality of the FBMC-OQAM signals. Although traditional channel estimation techniques, such as least square (LS) and minimum mean square error (MMSE), are widely applied to the FBMC-OQAM system via canceling the intrinsic imaginary interference from adjacent data symbols, the LS algorithm is subject to noise enhancement and it results in large mean square error (MSE), while the mmse algorithm needs to know the statistical information of channel in advance. Due to sparsity of the wireless channel, channel estimation is investigated as a compressive sensing (CS) problem. In this paper, we first introduce the coding method to cancel intrinsic imaginary interference for the FBMC-OQAM system. Then, a novel sparse adaptive subspace pursuit (SASP) method is proposed to improve the accuracy of LS channel estimation. Finally, we develop two distinctive algorithms, namely, auxiliary pilot (AP) SASP and coding-SASP, to estimate channel frequency respond (CFR) in the FBMC-OQAM system. The simulation results show that the AP-SASP and coding-SASP algorithms can offer a low complexity and fewer measurements compared with conventional orthogonal matching pursuit (OMP) and regularized OMP (ROMP) methods. Moreover, the proposed AP-SASP and coding-SASP algorithms have a better bit error ratio (BER) performance than the conventional OMP and ROMP methods for FBMC system in the doubly selective channels.

Joint Symbol Timing and Channel Estimation for FBMC-OQAM Systems

Filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) can achieve very low out-of-band radiation and is considered to be an important candidate waveform for future communication networks. However, the synchronization sequence design and channel estimation issues are complicated in FBMC-OQAM systems owing to the pulses overlap and the intrinsic interference. In this paper, we propose a new training sequence pattern with a high bandwidth efficiency. A pilot symbol and two auxiliary data symbols are used to generate a conjugate symmetric sequence in the time domain while protecting the pilots from the intrinsic interference. Thus, channel estimation can be performed directly by the pilots, and an auto-correlation symbol timing algorithm is introduced by exploiting the conjugate symmetry property. In addition, a pulse tail truncation method is proposed to improve the bandwidth efficiency for burst-mode transmission. Finally, some numerical simulation results are presented to validate the proposed symbol timing, channel estimation, and truncation methods in various scenarios.

Generalized Least Squares Based Channel Estimation for FBMC-OQAM

The presence of intrinsic inter-carrier interference (ICI) and inter-symbol interference (ISI) at the output of the matched filter receiver in filter bank multi-carrier with offset quadrature amplitude modulation (FBMC-OQAM) systems complicates the task of channel estimation (CE). The conventional approach is to use a pilot symbol preamble structure, such as in the interference approximation/cancellation methods (IAM/ICM), together with a simple virtual symbol (VS) based CE scheme. However, this virtual symbol approach ignores the residual interference from the data portion of the FMBC burst as well as the correlation of the noise across the sub-carriers; both of these factors ultimately limit the performance. In this paper, we propose a generalized least squares (GLS) based CE scheme which, when applied to the IAM/ICM pilot structures, takes into account both the correlated noise and data interference effects. Closed-form expressions are derived for the channel estimation mean-squared error (CE-MSE) of the proposed GLS method and for the conventional VS method, and it is shown that the proposed method leads to a significant reduction of the CE-MSE by up to 6 dB when compared with the VS based method. This is demonstrated to result in improved bit error rate (BER) performance, especially when higher-order modulation is employed, making it an attractive channel estimation method for many modern deployment scenarios. The proposed GLS-based channel estimation scheme is parameterized allowing a flexible trade-off between channel frequency selectivity, estimation complexity and CE-MSE gain. Finally, symmetry properties of the intrinsic interference coefficients for a general FBMC-OQAM system are also proved, which facilitate the computation of the noise and interference autocorrelation matrices required by the proposed algorithm.

Low-Complexity PTS Scheme for PAPR Reduction in FBMC-OQAM Systems

Most of the peak-to-average power ration (PAPR) reduction techniques, such as partial transmit sequence (PTS) algorithm and selective mapping algorithm, for conventional OFDM systems are not directly applied to filter bank multi-carrier with offset quadrature amplitude modulation (FBMC-OQAM) systems because of the overlapping structure of FBMC-OQAM signals. Furthermore, the complexity of the existing algorithms based on PTS is very high for the FBMC-OQAM systems. In this letter, we propose a low-complexity PTS based on hybrid processing algorithm (H-PTS) to reduce the PAPR values of FBMC-OQAM systems. Firstly, the proposed algorithm processes phase factors of the PTS by double-layer search. As a result, the complexity of searching the optimal phase factors is simplified. Moreover, an efficient algorithm of estimating the PAPR values of the FBMC-OQAM signals is employed to further reduce computational complexity. Simulation results show that, compared with the conventional PTS algorithm and segmental PTS algorithm, the proposed H-PTS algorithm could achieve a better PAPR reduction as well as lower computational complexity.

Sparse PTS scheme based on TR schemes for PAPR reduction in FBMC‐OQAM systems

The filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) has aroused widespread concern in the 5G communication. However, FBMC-OQAM has an inherent drawback of high peak-to-average power ratio (PAPR) that should be mitigated. Here, the authors propose an efficient hybrid scheme based on sparse partial transmit sequence (sparse PTS) scheme and tone reservation (TR) scheme to reduce the PAPR in FBMC-OQAM systems. The first step is to detect and record the location of peak of FBMC-OQAM signals and adopt phase rotation factors (based on PTS) to directly optimise the phase of recorded peak signals, which is called sparse PTS. Then the result is further processed by TR scheme for PAPR reduction. Simulation results show that the proposed hybrid scheme provides better PAPR reduction performance than the two schemes, and can achieve less side information transmitted than the sparse PTS scheme.

PAPR Reduction in the FBMC-OQAM System via Segment-Based Optimization

Multicarrier modulation (MCM) schemes have been intensively studied and developed, because of their numerous advantages, which include high data rate and immunity to multipath fading. Among MCM schemes, filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) has attracted considerable interest in recent years. However, the FBMC-OQAM system exhibits a high peak-to-average power ratio (PAPR). In this paper, we investigate the FBMC-OQAM system and present a solution for the problem of high PAPR that involves two separate components: minimizing the PAPR of each data block and optimizing each segment based on the preceding result. Unlike conventional partial transmit sequence techniques, the new method uses fewer combinations of phase factors, thereby decreasing the complexity of the algorithm while still reducing PAPR. In addition, sparse clipping signals are recovered by compressed sensing, and the bit error rates were analyzed based on sparsity level. The reductions in PAPR were also numerically evaluated using simulations. The simulation results confirm that the proposed technique effectively reduces the high peaks in the FBMC-OQAM system.

Modified PTS-based PAPR Reduction for FBMC-OQAM Systems

The filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) has been raised great concern in the 5G communication research. However FBMC-OQAM has also the inherent drawback of high peak-to-average power ratio (PAPR) that should be addressed. Due to the overlapping structure of FBMC-OQAM signals, it is proven that directly employing conventional partial transmit sequence (PTS) scheme proposed for OFDM to FBMC-OQAM is ineffective. In this paper, we propose a modified PTS-based scheme by employing phase rotation factors to optimize only the phase of the sparse peak signals, called as sparse PTS (S-PTS) scheme. Theoretical analysis and simulation results show that the proposed S-PTS scheme provides a significant PAPR reduction performance with lower computational complexity.

Coded Auxiliary Pilots for Channel Estimation in FBMC-OQAM Systems

In this paper, we propose a novel scattered pilot method for channel estimation in filter-bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) systems. We refer to this as the coded auxiliary pilot (CAP) method. It builds on the idea of using a few auxiliary pilot (AP) symbols to eliminate the imaginary interference on each scattered pilot. At the same time, to keep the spectral efficiency of transmission high, the AP symbols are coded to also carry information symbols. Theoretical analysis and numerical results show that the CAP method can maintain high spectral efficiency and high power efficiency, while achieving complete imaginary interference cancelation. Taking the spectral and power efficiency, the imaginary interference cancelation performance, and the coding/decoding complexity into consideration, the CAP method with two to four AP symbols is identified as a good compromised choice for practice.

Multi-Block Joint Optimization for the Peak-to-Average Power Ratio Reduction of FBMC-OQAM Signals

Recently, the filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) has attracted increasing attention. However, most peak-to-average power ratio (PAPR) reduction schemes developed for orthogonal frequency division multiplexing (OFDM) signals are not effective for FBMC-OQAM signals, due to the overlapping structure of FBMC-OQAM signals. In this paper, we propose an improved partial transmit sequence (PTS) scheme by employing multi-block joint optimization (MBJO) for the PAPR reduction of FBMC-OQAM signals, called as MBJO-PTS scheme. In PTS scheme, one data block is divided into several subblocks and each subblock is multiplied by a phase rotation factor for the subblock. The PTS scheme searches over all combinations of allowed phase factors to lower the PAPR. Unlike existing PAPR reduction schemes of independently optimizing the data blocks, the MBJO-based scheme exploits the overlapping structure of the FBMC-OQAM signal and jointly optimizes multiple data blocks. Moreover, we develop two algorithms for the optimization problem in the MBJO-PTS scheme, including a dynamic programming (DP) algorithm to guarantee the optimal solution and avoid exhaustive search. Theoretical analysis and simulations show that the proposed MBJO-PTS scheme could provide a significant PAPR reduction in the FBMC-OQAM system, by exploiting the overlapping structure of the FBMC-OQAM signal. Employing the proposed DP algorithm, the FBMC-OQAM system with the proposed MBJO-PTS scheme even outperforms the OFDM system with the conventional PTS scheme by 0.9 dB at CCDF of 10-3 in PAPR reduction, under the same number of subcarriers, modulation type and PTS parameters given in Section V.

Sliding Window Tone Reservation Technique for the Peak-to-Average Power Ratio Reduction of FBMC-OQAM Signals

The filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) has attracted increasing attention recently. In this paper, we address the problem of PAPR reduction for FBMC-OQAM systems using Tone Reservation (TR) technique. Due to the overlapping structure of FBMC-OQAM signals, directly applying TR schemes of OFDM systems to FBMC-OQAM systems is not effective. We improve the tone reservation (TR) technique by employing sliding window for the PAPR reduction of FBMC-OQAM signals, called sliding window tone reservation (SW-TR) technique. The proposed SWTR technique uses the peak reduction tones (PRTs) of several consecutive data blocks to cancel the peaks of the FBMC-OQAM signal inside a window. Furthermore, we propose a method to overlap the sliding windows to control the out-of-window peak regrowth caused by the peak-canceling signal.