scholarly journals WRELM based CO-OFDM system with improved performance, spectral efficiency and computational complexity

2021 ◽  
Author(s):  
Gurpreet Kaur ◽  
Gurmeet Kaur
Keyword(s):  
Phase Noise ◽  
Spectral Efficiency ◽  
Orthogonal Frequency Division Multiplexing ◽  
Fourier Transforms ◽  
Wavelet Packet ◽  
Discrete Wavelet ◽  
Ofdm System ◽  
High Spectral Efficiency ◽  
Improved Performance ◽  
Learning Machine

Abstract Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) system with Pilot-free phase noise compensator was introduced in order to accomplish the need of high spectral efficiency in the optical communication. In CO-OFDM system Discrete wavelet packet transforms (DWPTs) in place of Fast Fourier Transforms (FFTs) had attracted more attention since it has removed the need of cyclic prefix used to compensate fiber dispersion. In this paper, a DWPT based CO-OFDM system with Wilcoxon Robust Extreme Learning Machine based pilot-free phase noise compensator using multi-level QPSK partitioning of 16-QAM has been proposed. From the results of this work it has been seen that the percentage improvement in performance (in terms of Q-Factor) and spectral efficiency over traditional pilot-aided techniques is approximately 6 and 21 respectively. Moreover, this proposed work will comparatively reduce the overall system complexity.

A Data Aided Estimation Algorithm of Decimal Frequency Offset for OFDM System

2014 ◽  
Vol 902 ◽  
pp. 385-391
Author(s):  
Yun Tang ◽  
Feng Zheng ◽  
Hang Liu ◽  
Tian Qi Miao
Keyword(s):  
Spectral Efficiency ◽  
Orthogonal Frequency Division Multiplexing ◽  
Estimation Algorithm ◽  
Frequency Offset ◽  
Frequency Division ◽  
Ofdm System ◽  
Mechanism Of Formation ◽  
High Spectral Efficiency ◽  
Simulation Results ◽  
Better Than

In recent years, orthogonal frequency division multiplexing (OFDM) technology has drawn widespread attention for its high spectral efficiency, and has doing better on combating multipath interference than traditional technology.The reason why OFDM system has high spectral efficiency is that it takes advantage of the orthogonality between sub-carriers,characteristic of which can eliminate interference of each subcarrier even when the spectrum of them overlapped.It is the demanding of orthogonality between subcarriers to demodulate signals that makes OFDM system extremely sensitive to frequency offset. Even a little frequency offset can bring inter-carrier interference.This paper studied the mechanism of formation of interference among sub-carriers, and proposed a frequency offset estimation algorithm by changing the structure of data symbols so that the data symbols can act as training sequence.The simulation results show that the proposed algorithm performs better than S.C algorithm in many aspects, such as MSE, BER, Constellation and so on.

scholarly journals An Efficient DWT-DAPM Technique for PAPR Reduction in OFDM System

2020 ◽  
Vol 9 (3) ◽  
pp. 1691-1696 ◽  
Keyword(s):  
Amplitude Modulation ◽  
Fading Channel ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Gaussian Model ◽  
Channel Noise ◽  
Discrete Wavelet ◽  
Ofdm System ◽  
Flat Fading ◽  
Frequency Selective

In this paper, Discrete Wavelet Transform (DWT) Orthogonal Frequency Division Multiplexing (OFDM) system is compared with Discrete Cosine Transform (DCT) and Discrete Fourier Transform (DFT) OFDM systems. The channel noise is modelled with A white Gaussian Model (AWGN), the fading is the impairment in the channel and modelled by Rayleigh fading which is frequency selective fading channel and flat fading channel. The comparisons of Peak to Average Power Ratio (PAPR) and Bit Error Rate (BER) are made using modulation techniques such as Differential Amplitude and Phase Modulation (DAPM), Quadrature Amplitude Modulation (QAM) and Pulse Amplitude Modulation (PAM). Simulation results shows that PAPR is 4.497 dB for DWT-DAPM combination, 4.684 dB for DWT-QAM combination and 6.211 dB for DWT- PAM combination at 10-3 Complementary Cumulative Distributive Function (CCDF).The performance Analysis with the combination of DFT, DCT with DAPM, QAM and PAM are also compared. The BER is 0.01816, 0.01806 at 20 dB SNR in frequency selective channel, flat fading channel for DWT-DAPM and for DWT- QAM, AWGN channel BER is 0.01765 at 20dB SNR.

scholarly journals Performance Enhancement of Coherent Optical OFDM System Using LMS Algorithm

2020 ◽  
Vol 1 ◽  
pp. 1-5
Author(s):  
Manisha Bharti
Keyword(s):  
Phase Noise ◽  
Bit Error Rate ◽  
Error Rate ◽  
Orthogonal Frequency Division Multiplexing ◽  
Performance Enhancement ◽  
Lms Algorithm ◽  
Frame Structure ◽  
Least Mean Square ◽  
Ofdm Systems ◽  
Ofdm System

Instability of the local oscillator causes phase noise – a phenomenon that is a disadvantage and is considered to be a major obstacle in the functioning of coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. An attempt has been made in this paper to reduce the effects of common phase errors generated by phase noise. In this paper, a least mean square (LMS) based algorithm is proposed for estimation of phase noise. Using this proposed algorithm, the major problem of phase ambiguity caused by cycle slip is avoided and the bit error rate is greatly improved. Further, there is no requirement for modifying the frame structure of OFDM using this algorithm. A CO-OFDM system with the 8-PSK technique is used to implement the algorithm concerned. Furthermore, the algorithm, using the 8-PSK modulation technique, is analyzed and compared with the existing QPSK technique and with other algorithms. The investigations reveal that 8-PSK outperforms existing LMS algorithms using other techniques and significantly reduces the bit error rate.

scholarly journals A Radon Slantlet Transforms Based OFDM System Design and Performance Simulation under Different Channel Conditions

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Abbas Hasan Kattoush
Keyword(s):  
Radon Transform ◽  
Spectral Efficiency ◽  
Fading Channel ◽  
Orthogonal Frequency Division Multiplexing ◽  
Additive White Gaussian Noise ◽  
Mapping Technique ◽  
Intercarrier Interference ◽  
Ofdm Systems ◽  
Ofdm System ◽  
Channel Parameters

Due to its good orthogonality, slantlet transform (SLT) is used in orthogonal frequency division multiplexing (OFDM) systems to reduce intersymbol interference (ISI) and intercarrier interference (ICI). This eliminates the need for cyclic prefix (CP) and increases the spectral efficiency of the design. Finite Radon transform (FRAT) mapper has the ability to increase orthogonality of subcarriers, is nonsensitive to channel parameters variations, and has a small constellation energy compared with conventional fast-Fourier-transform- (FFT-) based OFDM. It is also able to work as a good interleaver, which significantly reduces the bit error rate (BER). In this paper both FRAT mapping technique and SLT modulator are implemented in a new design of an OFDM system. The new structure was tested and compared with conventional FFT-based OFDM, Radon transform-based OFDM, and SLT-based OFDM for additive white Gaussian noise (AWGN) channel, flat fading channel (FFC), and multipath selective fading channel (SFC). Simulation tests were generated for different channel parameters values. The obtained results showed that the proposed system has increased the spectral efficiency, reduced ISI and ICI, and improved BER performance compared with other systems.

scholarly journals Spectral Efficiency of FBMC Over OFDM System

2019 ◽  
Vol 9 (2S3) ◽  
pp. 235-237
Keyword(s):  
Spectral Efficiency ◽  
Orthogonal Frequency Division Multiplexing ◽  
Filter Bank ◽  
Average Power ◽  
Primary Objective ◽  
Mobile Environments ◽  
Frequency Division ◽  
Doppler Shifts ◽  
Wireless Broadband ◽  
High Spectral Efficiency

Significant wireless broadband technology used in various cellular standards is Orthogonal Frequency Division Multiplexing (OFDM) which will make use of Multi Carrier Modulated (MCM) systems. Even though OFDM has numerous advantages, it is hard to employ OFDM for complex networks. It is very hard to establish synchronization in mobile environments as it is difficult to predict the Doppler shifts of different users, which results in inter carrier interference (ICI). Further, filters associated with OFDM carrier have comparatively large sidebands which outcomes in Out of Band (OOB) radiations. Insufficient spectral usage is provided by CP-OFDM by using more guard band. So the problems caused by traditional OFDM/CP-OFDM can be answered by employing a new system termed as Filter Bank Multi Carrier (FBMC) System. It is a form of MCM and it can be considered as an advanced cyclic-prefix (CP-OFDM). In OFDM, whole band gets filtered while in FBMC, each sub carrier band is independently filtered. The primary objective of this work is to relate the performance of 5G modulation technique such as FBMC against OFDM and to suggest an ideal waveform for 5G communication in regard to high spectral efficiency, spectral density, BER and less Peak to Average Power Ratio (PAPR).

scholarly journals Analysis of Doppler frequency shift response mechanism based on OFDM system

2018 ◽  
Vol 232 ◽  
pp. 04049
Author(s):  
Ke Li ◽  
Zhiguo Sun ◽  
Xiaoyan Ning ◽  
Ming Diao
Keyword(s):  
Spectral Efficiency ◽  
Doppler Frequency ◽  
Doppler Frequency Shift ◽  
Response Mechanism ◽  
Ofdm System ◽  
System Parameters ◽  
Shift Response ◽  
High Spectral Efficiency ◽  
High Dynamic ◽  
Response Formula

OFDM system is widely used in mobile communication because of its high spectral efficiency and strong anti-multipath capability. However, in high dynamic scenarios, the Doppler shift between the transmitter and the receiver destroys the orthogonality between the sub-carriers, resulting the interference between the sub-carriers and distortion of the signal, which greatly degrades the system performance. In this paper, a mathematical model of Offset-OFDM system was established and the Doppler response formula of OFDM system in high white channel was derived. Furthermore, we investigated the factors that influence the performance of OFDM. This study laid the foundation for determining OFDM system parameters in high dynamic scenarios.

scholarly journals Laser Phase Noise Tolerance of Uniform and Probabilistically Shaped QAM Signals for High Spectral Efficiency Systems

2020 ◽  
Vol 38 (2) ◽  
pp. 439-446 ◽  
Author(s):  
Takeo Sasai ◽  
Asuka Matsushita ◽  
Masanori Nakamura ◽  
Seiji Okamoto ◽  
Fukutaro Hamaoka ◽  
...  
Keyword(s):  
Phase Noise ◽  
Spectral Efficiency ◽  
Noise Tolerance ◽  
High Spectral Efficiency
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