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Article
Optimization of PAPR Reduction Technique for OFDM Signal Based Discrete Multiwavelet Critical-Sampling Transformin MC-CDMA using Selected Mapping with Phase Modification Method
تحسين تقنية تقليل نسبة القدرة العظمى الى القدرة المعدلة لاشارة مقسم التردد العامودي المبني على التحويل المنفصل لمتعدد المويجات العينة الحرجة في تقسيم الرموز لعدة حوامل بتعدد الدخولباستخدام طرق اختيارتقنيات التضمين و تحسين الطور

Author: Dr. Mohammed Aboud Kadhim مدرس دكتور محمد عبود كاظم
Journal: JOURNAL OF MADENAT ALELEM COLLEGE مجلة كلية مدينة العلم الجامعة ISSN: 2073,2295 Year: 2017 Volume: 9 Issue: 1 Pages: 229-239
Publisher: City College of Science University كلية مدينة العلم الجامعة

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Abstract

Multi-carrier code-division multiple access (MC-CDMA) is anextensively known transmission technique for high speed data communication. In MC-CDMA, transmission is performed in parallel on various frequencies. This technique is widely sought after for the transmission of digital data via the media offadding channels. This paper showcases original contribution to the field of “peak-to-average power ratio (PAPR)” reductioneffect by using “Multiwavelet Critical-Sampling Transform (DMWCST)” in the developmental “MC-CDMA systems”. In this study, primarily oriented towards the selected mapping techniques and phase modification was used. As well showcase how selected mapping with phase modification can be applied to mitigate PAPR since they are signal distortionless and their complexity is lesser compared to other techniques.

تقسيم الرموز لعدة حوامل بتعدد الدخول (MC-CDMA) هواسلوب معروف على نطاق واسع لنقل البيانات بسرعةعالية.فى MC-CDMA يتم الارسال على التوازى فى مختلف الترددات. هذاالاسلوب على نطاق واسع لنقل البيانات الرقمية عنطريق وسائط نقل وقنوات تلاشي ضعيفة. هذا العمل يعرض اسهامه الاصلى فى مجال تقليل نسبة القدرة العظمى الى القدرةالمعدلة لاشارة مقسم التردد العاموديباستخدام نظام التحويل المنفصل لمتعددالمويجات العينة الحرجة في تطوير نظام MC-CDMA .فىهذا العمل, فى المقام الاول الاتجاه نحومرحلة اختيار تقنيات التضمين و تحسين الطور وكيفية تطبيقه لتخفيفPAPR لانتشويه الاشارة اقل و درجة التعقيداقل مقارنة بتقنيات اخرى .

Keywords

MC-CDMA --- OFDM --- PAPR --- CCDF --- DMWCST.


Article
NON-LINEARITY DISTORTION MITIGATION OF DOWNLINK-LTE SYSTEM USING MODIFIED AMPLITUDE CLIPPING AND FREQUENCY DOMAIN RANDOMIZATION

Authors: Montadar Abas Taher --- Abidaoun Hamdan Shallal --- Ilham Hameed Qaddoori
Journal: DIYALA JOURNAL OF ENGINEERING SCIENCES مجلة ديالى للعلوم الهندسية ISSN: 19998716/26166909 Year: 2015 Volume: 8 Issue: 4 Pages: 613-617
Publisher: Diyala University جامعة ديالى

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Abstract

Wireless telecommunication systems are almost the most dominant field of the communication systems context nowadays especially the long-term evolution (LTE) system. Orthogonal frequency division multiplexing (OFDM), has become the base for current and future communication systems, because of its capability to combat multipath and fading channels and its competency for high data rate transmissions. However, coherent combination of subcarriers leads to large power peaks with respect to the average power level; this is the so-called peak power ratio (PPR). Various methodologies are available in the literature, the simple approach is the amplitude clipping. However, amplitude clipping causes in-band distortion and out-of-band-radiation, thus, the bit error rate (BER) performance will degrades dramatically. Taher et al (2014) suggested a new amplitude-clipping algorithm, where the core-clipping function was replaced with a non-distorting function, but the proficiency of reducing the PPR was not in the good extent. In this paper, the new clipping function will be supported by frequency-domain randomization operation, such that the coherent combination of the OFDM subcarriers will not stay in the same order, leading to lower PPR at the output of the power amplifier. Results show that the hybrid combination of the randomization process with the new clipping function produces lower values of PPRs. Thus, the proposed approach has gotten 1.5 dB more reduction magnitude in the PPR with respect to Taher et al scheme. The complementary cumulative distribution function (CCDF) was the tool to monitor the PPR performance behavior.


Article
PAPR Reduction in Coherent Optical OFDM System using Modified Sliding Norm Transformer

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Abstract

Orthogonal Frequency Division Multiplexing is one of the mostimportant multiple carrier modulation format, which has many applications inwireless communication and optical communication. It is considered as anexcellent method for fast optical communication inferable from its high spectralefficiency and its strength to path losses. Peak to average power ratio isregarded as one of the main problems that are experienced by the opticalorthogonal frequency division multiplexing system, which directly affects thecharacteristics of the system. The current paper proposes an efficient techniqueto reduce Peak to Average Power Ratio by the modified Dursun’s method or theso called modified discrete sliding norm transformer in coherent opticalorthogonal frequency division multiplexing system for the first time to the baseof our knowledge consequently. The proposed technique does not need to sendside information to the receiver; also, it does not degrade bandwidth. Thisalgorithm lessens Peak to Average Power Ratio in the optical coherentOrthogonal Frequency Division Multiplexing system to about 4.15 dB atcomplementary cumulative distribution function (CCDF) probability of 10-3 andimproves the system performance.


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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