A Coherent Optical OFDM Communication System with Nonlinear Distortion Compensation in the Channel and Receiver

2017 ◽  
Vol 38 (3) ◽  
Author(s):  
R. S. Asha ◽  
V. K. Jayasree
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Low Cost ◽  
Additive White Gaussian Noise ◽  
Wireless Channel ◽  
Noise Model ◽  
Channel Noise ◽  
Distortion Compensation ◽  
Sequence Estimation ◽  
Maximum Likelihood Sequence Estimation ◽  
Optical Ofdm

AbstractA simple and low-cost scheme is proposed for reducing the distortions in the coherent optical orthogonal frequency-division multiplexing (CO-OFDM) system. The total wireless channel noise and the distortions in the receiver can be considered as an additive white Gaussian noise model and all distortions can be reduced using maximum likelihood sequence estimation (MLSE) equalizers. The performance of the CO-OFDM is analyzed for different fiber lengths and laser powers. Results show that the MLSE-equalized system can outperform with a higher

scholarly journals Intelligent Non-Contact Sensing for Connected Health Using Software Defined Radio Technology

Electronics ◽  
2021 ◽  
Vol 10 (13) ◽  
pp. 1558
Author(s):  
Muhammad Bilal Khan ◽  
Mubashir Rehman ◽  
Ali Mustafa ◽  
Raza Ali Shah ◽  
Xiaodong Yang
Keyword(s):  
Psychological Health ◽  
Software Defined Radio ◽  
Orthogonal Frequency Division Multiplexing ◽  
Additive White Gaussian Noise ◽  
Vital Signs ◽  
Wireless Channel ◽  
Machine Learning Algorithms ◽  
Breathing Patterns ◽  
Connected Health ◽  
Innovative Solution

The unpredictable situation from the Coronavirus (COVID-19) globally and the severity of the third wave has resulted in the entire world being quarantined from one another again. Self-quarantine is the only existing solution to stop the spread of the virus when vaccination is under trials. Due to COVID-19, individuals may have difficulties in breathing and may experience cognitive impairment, which results in physical and psychological health issues. Healthcare professionals are doing their best to treat the patients at risk to their health. It is important to develop innovative solutions to provide non-contact and remote assistance to reduce the spread of the virus and to provide better care to patients. In addition, such assistance is important for elderly and those that are already sick in order to provide timely medical assistance and to reduce false alarm/visits to the hospitals. This research aims to provide an innovative solution by remotely monitoring vital signs such as breathing and other connected health during the quarantine. We develop an innovative solution for connected health using software-defined radio (SDR) technology and artificial intelligence (AI). The channel frequency response (CFR) is used to extract the fine-grained wireless channel state information (WCSI) by using the multi-carrier orthogonal frequency division multiplexing (OFDM) technique. The design was validated by simulated channels by analyzing CFR for ideal, additive white gaussian noise (AWGN), fading, and dispersive channels. Finally, various breathing experiments are conducted and the results are illustrated as having classification accuracy of 99.3% for four different breathing patterns using machine learning algorithms. This platform allows medical professionals and caretakers to remotely monitor individuals in a non-contact manner. The developed platform is suitable for both COVID-19 and non-COVID-19 scenarios.

PAPR reduction scheme for optical OFDM techniques

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Ompal Singh ◽  
Rajeev Paulus ◽  
Rajiv Srivastava
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Optical Fiber Communication ◽  
Papr Reduction ◽  
Channel Noise ◽  
Optical Wireless ◽  
Fiber Communication ◽  
Optical Ofdm ◽  
The Mathematical Model ◽  
Ber Performance

AbstractIn both optical wireless and optical fiber communication, orthogonal frequency division multiplexing (OFDM) plays an important role in data transmission. In the similar context, DC-coupled optical (DCO) OFDM and asymmetrically clipped optical (ACO) OFDM are discussed. DCO-OFDM has better peak to average power ratio (PAPR) but bit error rate (BER) performance is poor; however, in case of ACO-OFDM, PAPR is poor but BER performance is good. Moreover, DCO-OFDM is more power hungry; therefore, ACO-OFDM is considered as a preferred choice. Recently, asymmetrically clipped DC-biased optical (ADO)-OFDM is proposed, which shows good PAPR and BER performance. Clipping and µ-law companding techniques are discussed for PAPR reduction. The mathematical model is developed for all the three methods for received signal while considering clipping and companding noises along with channel noise. It is found that ADO-OFDM is better choice in comparison to DCO and ACO-OFDM. However, in case of ADO-OFDM, receiver structure is more complex.

scholarly journals OFDM comparison with FFT and DWT processing for DVB-T2 wireless channels

Inge CUC ◽  
2018 ◽  
Vol 14 (2) ◽  
pp. 97-105
Author(s):  
Hernan Paz Penagos
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Additive White Gaussian Noise ◽  
Average Power ◽  
Wireless Channel ◽  
Rician Fading ◽  
Discrete Wavelet ◽  
Research Experience ◽  
Radio Communications ◽  
Ofdm Signal ◽  
Future Work

Introduction: Recent studies on the FFT processing (Fast Fourier Transform) or DWT (Discrete Wavelet Transform) of the OFDM signal (Orthogonal Frequency Division Multiplexing) have shown pros and cons for DVB-T2 (Digital Video Broadcasting-Second Generation Terrestrial) radio communications; however, the benefits of both types of processing have yet to be compared for the same scenario. Objective: The objective of this research is to compare the response of the wireless channel with AWGN noise (Additive White Gaussian Noise Channel) and Rayleigh and Rician fading in the UHF (Ultra High Frequency) band. Methodology: The transmission of DVB-T2 information with OFDM modulation and FFT and DWT processing was simulated in Matlab®, specifically in Simulink. Results: The results of the study proved to be more efficient for DWT system than FFT system, due to the low rate of erroneous bits, spectral efficiency and reduction of the Peak-to-Average Power Ratio (PAPR), for Eb / No relations greater than 10dB. Conclusions: In this article, we present the designs of both systems and the results of the research experience; likewise, the practical applicability of these systems is discussed, and improvements are suggested for future work.

Realization of the Viterbi Algorithm in MLSE with Intersymbol Interference

2012 ◽  
Vol 214 ◽  
pp. 208-212
Author(s):  
Ying Lu ◽  
Quan Yuan Xu ◽  
Zhi Gang Liu
Keyword(s):  
Computational Complexity ◽  
Gaussian Noise ◽  
Viterbi Algorithm ◽  
Intersymbol Interference ◽  
Additive White Gaussian Noise ◽  
Probability Of Error ◽  
Sequence Estimation ◽  
Time Dispersion ◽  
Maximum Likelihood Sequence Estimation ◽  
Receiver Model

Optimum receiver model for channels with Intersymbol Interference (ISI) and Additive White Gaussian Noise (AWGN) are introduced to deduce the Viterbi algorithm in the Maximum-Likelihood Sequence Estimation (MLSE). Finally, we use Matlab to simulate the algorithm in three different channels and analyze the experiment results. Analyses show that the Viterbi algorithm is applicable for any channel which is optimum from a probability of error viewpoint; the MLSE for channels with ISI has a computational complexity that grows exponentially with the length of channels time dispersion L; the loss of performance is negligible when the decoding delay achieves 5L.

scholarly journals Efficient Estimation of CFO-Affected OFDM BER Floor in Small Cells with Resource-Limited IoT End-Points

Sensors ◽  
2020 ◽  
Vol 20 (13) ◽  
pp. 3747
Author(s):  
Adriana Lipovac ◽  
Vlatko Lipovac ◽  
Borivoj Modlic
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Carrier Frequency Offset ◽  
Signal To Noise Ratio ◽  
Low Cost ◽  
Error Recovery ◽  
Efficient Estimation ◽  
Analytical Models ◽  
Small Cells ◽  
End Points ◽  
Power Delay Profile

Contemporary wireless networks dramatically enhance data rates and latency to become a key enabler of massive communication among various low-cost devices of limited computational power, standardized by the Long-Term Evolution (LTE) downscaled derivations LTE-M or narrowband Internet of Things (NB IoT), in particular. Specifically, assessment of the physical-layer transmission performance is important for higher-layer protocols determining the extent of the potential error recovery escalation upwards the protocol stack. Thereby, it is needed that the end-points of low processing capacity most efficiently estimate the residual bit error rate (BER) solely determined by the main orthogonal frequency-division multiplexing (OFDM) impairment–carrier frequency offset (CFO), specifically in small cells, where the signal-to-noise ratio is large enough, as well as the OFDM symbol cyclic prefix, preventing inter-symbol interference. However, in contrast to earlier analytical models with computationally demanding estimation of BER from the phase deviation caused by CFO, in this paper, after identifying the optimal sample instant in a power delay profile, we abstract the CFO by equivalent time dispersion (i.e., by additional spreading of the power delay profile that would produce the same BER degradation as the CFO). The proposed BER estimation is verified by means of the industry-standard LTE software simulator.

scholarly journals Reconstruction of Relative Phase of Self-Transmitting Devices by Using Multiprobe Solutions and Non-Convex Optimization

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2459
Author(s):  
Rubén Tena Sánchez ◽  
Fernando Rodríguez Varela ◽  
Lars J. Foged ◽  
Manuel Sierra Castañer
Keyword(s):  
Iterative Algorithm ◽  
Degrees Of Freedom ◽  
Relative Phase ◽  
Low Cost ◽  
Initial Guess ◽  
Noise Model ◽  
Medium Size ◽  
Phase Reconstruction ◽  
Linear Combinations ◽  
Iterative Optimization Algorithm

Phase reconstruction is in general a non-trivial problem when it comes to devices where the reference is not accessible. A non-convex iterative optimization algorithm is proposed in this paper in order to reconstruct the phase in reference-less spherical multiprobe measurement systems based on a rotating arch of probes. The algorithm is based on the reconstruction of the phases of self-transmitting devices in multiprobe systems by taking advantage of the on-axis top probe of the arch. One of the limitations of the top probe solution is that when rotating the measurement system arch, the relative phase between probes is lost. This paper proposes a solution to this problem by developing an optimization iterative algorithm that uses partial knowledge of relative phase between probes. The iterative algorithm is based on linear combinations of signals when the relative phase is known. Phase substitution and modal filtering are implemented in order to avoid local minima and make the algorithm converge. Several noise-free examples are presented and the results of the iterative algorithm analyzed. The number of linear combinations used is far below the square of the degrees of freedom of the non-linear problem, which is compensated by a proper initial guess. With respect to noisy measurements, the top probe method will introduce uncertainties for different azimuth and elevation positions of the arch. This is modelled by considering the real noise model of a low-cost receiver and the results demonstrate the good accuracy of the method. Numerical results on antenna measurements are also presented. Due to the numerical complexity of the algorithm, it is limited to electrically small- or medium-size problems.

Simulation modeling of free space optical communication system

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ajay Sharma ◽  
Rajinder Singh Kaler
Keyword(s):  
Optical Communication ◽  
Free Space ◽  
Simulation Modeling ◽  
Additive White Gaussian Noise ◽  
Wireless Channel ◽  
Free Space Optical Communication ◽  
Optical Wireless ◽  
Free Space Optical ◽  
Wireless Signal ◽  
Space Optical Communication

Abstract The optical wireless communication has been designed by developing a model with the support of MATLAB simulator using Simulink where channel considered to be a free space. In this model, Additive White Gaussian Noise (AWGN) channel has used to analyze bit error rate (BER) and power loss of optical wireless signal at receiver. The consequence due to turbulence in atmosphere of free space on transmitted signal has examined. The BER and signal power have extremely ruined on rigorous atmospheric unstable condition even for a short distance in an optical wireless channel. The BER of less than 10−3 has been achieved for free space optical communication considered to be an excellent BER for FSO.

scholarly journals Robust Silent Localization of Underwater Acoustic Sensor Network Using Mobile Anchor(s)

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 727
Author(s):  
Rahul Mourya ◽  
Mauro Dragone ◽  
Yvan Petillot
Keyword(s):  
Channel Model ◽  
Low Cost ◽  
Sensor Nodes ◽  
Noise Model ◽  
Robust Estimator ◽  
Acoustic Sensor ◽  
Underwater Acoustic ◽  
Acoustic Channel ◽  
Localization Scheme ◽  
Mobile Anchor

Underwater acoustic sensor networks (UWASNs) can revolutionize the subsea domain by enabling low-cost monitoring of subsea assets and the marine environment. Accurate localization of the UWASNs is essential for these applications. In general, range-based localization techniques are preferred for their high accuracy in estimated locations. However, they can be severely affected by variable sound speed, multipath spreading, and other effects of the acoustic channel. In addition, an inefficient localization scheme can consume a significant amount of energy, reducing the effective life of the battery-powered sensor nodes. In this paper, we propose robust, efficient, and practically implementable localization schemes for static UWASNs. The proposed schemes are based on the Time-Difference-of-Arrival (TDoA) measurements and the nodes are localized passively, i.e., by just listening to beacon signals from multiple anchors, thus saving both the channel bandwidth and energy. The robustness in location estimates is achieved by considering an appropriate statistical noise model based on a plausible acoustic channel model and certain practical assumptions. To overcome the practical challenges of deploying and maintaining multiple permanent anchors for TDoA measurements, we propose practical schemes of using a single or multiple surface vehicles as virtual anchors. The robustness of localization is evaluated by simulations under realistic settings. By combining a mobile anchor(s) scheme with a robust estimator, this paper presents a complete package of efficient, robust, and practically usable localization schemes for low-cost UWASNs.

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