System Performance of Coherent Optical Orthogonal Frequency Division Multiplexing

2006 ◽  
Author(s):  
W. Shieh ◽  
C. Athaudage
Keyword(s):  
System Performance ◽  
Orthogonal Frequency Division Multiplexing ◽  
Frequency Division Multiplexing ◽  
Frequency Division

Evaluating and Reducing the Envelope Fluctuations of OFDM Signals Based on Distortion Prediction

Frequenz ◽  
2017 ◽  
Vol 71 (1-2) ◽  
pp. 73-81
Author(s):  
Xiangyin Zhang ◽  
Xiaodong Zhu ◽  
Youxi Tang
Keyword(s):  
System Performance ◽  
Orthogonal Frequency Division Multiplexing ◽  
Nonlinear Distortion ◽  
Average Power ◽  
Frequency Division Multiplexing ◽  
Power Ratio ◽  
Frequency Division ◽  
Selective Mapping ◽  
Mapping Scheme ◽  
Ofdm Signals

Abstract Orthogonal frequency division multiplexing (OFDM) signals with large envelope fluctuations are prone to be affected by power amplifier (PA), resulting in degradation of system performance. Peak-to-average power ratio (PAPR) and cubic metric (CM) are commonly used as the reduction criteria of envelope fluctuations of OFDM signals. However, our analysis shows that minimizing the PAPR or CM does not necessarily mean the optimization of system performance, since both metrics are inadequate to quantify the distortion in nonlinear OFDM transmission. In this paper, we fully discuss the effects of PA nonlinearity on OFDM signals and propose a new metric called distortion component metric (DCM), which is closely related to the nonlinear distortion caused by the PA. We compare the system performance when several metrics are respectively used as the reduction criterion for the selective mapping scheme. It is shown that in the presence of memoryless or memory PA, the usage of DCM can provide better inband and out-of-band performance than PAPR and CM.

scholarly journals Relaxation of the Radio-Frequency Linewidth for Coherent-Optical Orthogonal Frequency-Division Multiplexing Schemes by Employing the Improved Extreme Learning Machine

Symmetry ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 632 ◽  
Author(s):  
David Zabala-Blanco ◽  
Marco Mora ◽  
Cesar A. Azurdia-Meza ◽  
Ali Dehghan Firoozabadi ◽  
Pablo Palacios Játiva ◽  
...  
Keyword(s):  
System Performance ◽  
Orthogonal Frequency Division Multiplexing ◽  
Regularization Parameter ◽  
Transmission Rate ◽  
Phase Error ◽  
Activation Function ◽  
The Other ◽  
Frequency Division Multiplexing ◽  
The Novel ◽  
Frequency Division

A coherent optical (CO) orthogonal frequency division multiplexing (OFDM) scheme gives a scalable and flexible solution for increasing the transmission rate, being extremely robust to chromatic dispersion as well as polarization mode dispersion. Nevertheless, as any coherent-detection OFDM system, the overall system performance is limited by laser phase noises. On the other hand, extreme learning machines (ELMs) have gained a lot of attention from the machine learning community owing to good generalization performance, negligible learning speed, and minimum human intervention. In this manuscript, a phase-error mitigation method based on the single-hidden layer feedforward network prone to the improved ELM algorithm for CO-OFDM systems is introduced for the first time. In the training step, two steps are distinguished. Firstly, pilots are used, which is very common in OFDM-based systems, to diminish laser phase noises as well as to correct frequency-selective impairments and, therefore, the bandwidth efficiency can be maximized. Secondly, the regularization parameter is included in the ELM to balance the empirical and structural risks, namely to minimize the root mean square error in the test stage and, consequently, the bit error rate (BER) metric. The operational principle of the real-complex (RC) ELM is analytically explained, and then, its sub-parameters (number of hidden neurons, regularization parameter, and activation function) are numerically found in order to enhance the system performance. For binary and quadrature phase-shift keying modulations, the RC-ELM outperforms the benchmark pilot-assisted equalizer as well as the fully-real ELM, and almost matches the common phase error (CPE) compensation and the ELM defined in the complex domain (C-ELM) in terms of the BER over an additive white Gaussian noise channel and different laser oscillators. However, both techniques are characterized by the following disadvantages: the CPE compensator reduces the transmission rate since an additional preamble is mandatory for channel estimation purposes, while the C-ELM requires a bounded and differentiable activation function in the complex domain and can not follow semi-supervised training. In the same context, the novel ELM algorithm can not compete with the CPE compensator and C-ELM for the 16-ary quadrature amplitude modulation. On the other hand, the novel ELM exposes a negligible computational cost with respect to the C-ELM and PAE methods.

scholarly journals Low Code Coding Approach for ofdm Systems Coded with the Progressive Transmission

2020 ◽  
Vol 9 (12) ◽  
pp. 185-188
Keyword(s):  
Channel Coding ◽  
System Performance ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multipath Channels ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Coding Schemes ◽  
Parallel Channels ◽  
Better Than

Orthogonal Frequency Division Multiplexing (OFDM) offers several benefits such as flexible wrapping, mail sign interference, reduced complexity and more. The only way to match parallel channels is to have genetic diversity in multipath channels. Various coded of OFDM systems reported using some form of channel coding or pre-coding to improve system performance. The execution of irrational orthogonal frequency division multiplexing (OFDM) on blurred channels is usually better than introducing some coding. Various coding schemes for off-OFDM have been reported in the literature.

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