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Article
Performance Evaluation of DHT Based Optical OFDM for IM/DD Transmission Over Diffused Multipath Optical Wireless Channel

Author: Hussein A. Leftah
Journal: Iraqi Journal for Electrical And Electronic Engineering المجلة العراقية للهندسة الكهربائية والالكترونية ISSN: 18145892 Year: 2019 Volume: 15 Issue: 1 Pages: 72-75
Publisher: Basrah University جامعة البصرة

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Abstract

Optical OFDM based on discrete Hartley transform(DHT-O-OFDM) has been proposed for large-size data mappingintensity modulation direct detection (IM/DD) scheme as an alternativeto the conventional optical OFDM. This paper presents aperformance analysis and evaluation of IM/DD optical DC-biasedDHT-O-OFDM over diffused multipath optical wireless channels.Zero-padding guard interval along with minimum mean-squareerror (MMSE) equalizer are used in electrical domain after thedirect detection to remove the inter-symbol interference (ISI)and eliminate the deleterious effects of the multi-path channels.Simulation results show that the ZP-MMSE can effectively reducethe effects of multi-path channels. The results also show that theeffects of optical wireless multi-path channel become more seriousas the data signaling order increases.


Article
Mitigate PAPR Effect in Optical Orthogonal Frequency Division Multiplexing Using Companding Technique

Authors: Mohammed A. Husein --- Sinan M. Abdul Satar --- Ali n. Kareem
Journal: IRAQI JOURNAL OF COMPUTERS,COMMUNICATION AND CONTROL & SYSTEMS ENGINEERING المجلة العراقية لهندسة الحاسبات والاتصالات والسيطرة والنظم ISSN: 18119212 Year: 2018 Volume: 18 Issue: 3 Pages: 60-69
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

orthogonal frequency division multiplexing (OFDM) is emerging asthe leading technology for high data rates. The OFDM based on multicarriertransmission that transforms a wideband channel into a group of thin-bandchannels. The high peak to average power ratio (PAPR) considers the maindrawback factor in this system, so the companding technique modifies theamplitude of OFDM signal to reduce this factor. The proposed A-lawcompanding technique has been implemented in intensity modulation/directdetection optical orthogonal frequency division multiplexing (IM/DDOOFDM).The proposed companding scheme guarantees the improvedperformance in terms of bit error rate (BER) and quality factor (QF) whilereducing PAPR effectively and efficiently by modifying the amplitude of thetransmitted signals. Our results confirm that the suggested scheme exhibits agood ability to reduce PAPR and a good BER performance based on the use theA factor. At the complementary cumulative distribution function (CCDF) of 10-3, the PAPR value of our proposed scheme is about 4.4 dB lower than those ofun-companded signal at best control factor used of A at 87.6, accordingly theQF is 2.5 dB and the BER is 6.2×10-3 at a distance 900km without anyequalization technique or training sequence or any channel estimation.

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