scholarly journals Number of subcarrier filter coefficients in GFDM system: effect on performance

Ingenius ◽  
2019 ◽  
pp. 53-61
Author(s):  
Randy Verdecia Peña ◽  
Humberto Millán Vega
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Modulation Scheme ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Transmission Scheme ◽  
System Effect ◽  
Simple Method ◽  
Multicarrier Transmission ◽  
Prototype Filter

Generalized Frequency Division Multiplexing (GFDM) is a non-orthogonal multicarrier transmission scheme proposed for fifth (5G) and future generation wireless networks. Due to its attractive properties, it has been recently discussed as a candidate waveform for the future wireless communication systems. GFDM is introduced as a generalized form of the widely used Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme and it uses only one cyclic prefix (CP) for a group of symbols. The main focus of this work is to present like impact on the system performance the coefficient quantity of the subcarrier filter. A simple method for the computation of the coefficients of the prototype filter is employed. Besides, it is presented a structure for the GFDM by taking advantage of the arrangement in the modulation matrix. We evaluated the Bit Error Rate (BER) using the receiver models presented in this work. The results showed that the BER is affected according to the coefficients quantity of the prototype filter. Based on the obtained results, the coefficients quantity has a relation with the number of time slots of the GFDM system.

Peak-to-Average Power Ratio Reduction for Acoustic Orthogonal Frequency Division Multiplexing Systems

2010 ◽  
Vol 44 (4) ◽  
pp. 30-41 ◽  
Author(s):  
Guillem Rojo ◽  
Milica Stojanovic
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multipath Propagation ◽  
Average Power ◽  
Gradient Algorithm ◽  
High Rate ◽  
Modulation Scheme ◽  
Frequency Division Multiplexing ◽  
Power Ratio ◽  
Frequency Division

AbstractOrthogonal frequency division multiplexing (OFDM) is an appealing modulation scheme for high-rate underwater acoustic communications that are challenged by multipath propagation. However, it has a drawback in the large peak-to-average power ratio (PAR). Techniques for PAR reduction have been extensively studied for radio communication systems. Although these techniques are applicable to acoustic systems, we take a different approach that aims to capitalize on the fundamental differences between the acoustic and the radio systems; namely, the fact that acoustic transmissions are inherently band limited. We extend the tone reservation technique to the out-of-band carriers and design efficient methods for constructing OFDM signals with lower PAR. Two approaches are investigated, one based on a gradient algorithm and another that uses random sequences. Simulation results show that our techniques can provide PAR reduction without the loss in data rate.

scholarly journals EVM Loss: A Loss Function for Training Neural Networks in Communication Systems

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1094
Author(s):  
Scott Stainton ◽  
Martin Johnston ◽  
Satnam Dlay ◽  
Paul Anthony Haigh
Keyword(s):  
Neural Networks ◽  
Loss Function ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Frequency Division Multiplexing ◽  
Efficiency Gain ◽  
Frequency Division ◽  
Error Vector Magnitude ◽  
Modulation Formats ◽  
Complex Approach

Neural networks and their application in communication systems are receiving growing attention from both academia and industry. The authors note that there is a disconnect between the typical objective functions of these neural networks with regards to the context in which the neural network will eventually be deployed and evaluated. To this end, a new loss function is proposed and shown to increase the performance of neural networks when implemented in a communication system compared to previous methods. It is further shown that a ‘split complex’ approach used by many implementations can be improved via formalisation of the ‘concatenated complex’ approach described herein. Experimental results using the orthogonal frequency division multiplexing (OFDM) and spectrally efficient frequency division multiplexing (SEFDM) modulation formats with varying bandwidth compression factors over a wireless visible light communication (VLC) link validate the efficacy of the proposed method in a real system, achieving the lowest error vector magnitude (EVM), and thus bit error rate (BER), across all experiments, with a 5 dB to 10 dB improvement in the received symbols EVM overall compared to the baseline implementation, with bandwidth compressions down to 40% compared to OFDM, resulting in a spectral efficiency gain of 67%.

scholarly journals Channel estimation of OFDM in C-band communication systems under different distribution conditions

2021 ◽  
Vol 23 (3) ◽  
pp. 1778
Author(s):  
Heba Abdul-Jaleel Al-Asady ◽  
Hassan Falah Fakhruldeen ◽  
Mustafa Qahtan Alsudani
Keyword(s):  
Fourier Transform ◽  
Channel Estimation ◽  
Fast Fourier Transform ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm System ◽  
High Data ◽  
High Efficient

<p>Orthogonal frequency division multiplexing (OFDM) is a transmission system that uses multiple orthogonal carriers that are sent out at the same time. OFDM is a technique for mobile and wireless communication that has high-efficient frequency utilization, high data-rate transmission, simple and efficient implementation using the fast Fourier transform (FFT) and the inverse fast Fourier transform (IFFT), and reduces inter symbol interference (ISI) by inserting cyclic prefix (CP). One of the most important approaches in an OFDM system is channel estimation. In this paper, the orthogonal frequency division multiplexing system with the Rayleigh channel module is analyzed for different areas. The proposed approach used large numbers of subcarriers to transmit the signals over 64-QAM modulation with pilot add channel estimation. The accuracy of the OFDM system is shown in the measuring of the relationships of peak power to the noise ratio and bit error rate.</p>

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