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Article
A New Technique for PAPR Reduction in OFDM System

Author: Ahmed K. Abed احمد كريم عبد
Journal: University of Thi-Qar Journal for Engineering Sciences مجلة جامعة ذي قار للعلوم الهندسية ISSN: 26645564/26645572 Year: 2011 Volume: 2 Issue: 2 Pages: 41-51
Publisher: Thi-Qar University جامعة ذي قار

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Abstract

Orthogonal frequency division multiplexing (OFDM) is an attractive technique for modern wireless communication. One major drawback of orthogonal frequency division multiplexing schemes is the high peak to average power ratio (PAPR) of the output signal. Selecting mapping (SLM) and partial transmit sequences (PTS) are two important techniques for reducing PAPR, but they need to transmit side information to indicate how the transmitter generates the signals. In this paper, we proposed an efficient technique to reduce PAPR in OFDM system. For this technique, circular shifter used to produce K cyclic sequences from the same information sequence. These sequences XOR with K randomly generated keys, the same keys used in receiver side to detect data. The sequence with the lowest PAPR among K sequences is chosen for transmission. Side Information (SI) is coded using Hamming code and embedded into the information sequence. Computer simulation tests have been applied on BPSK and N= 64 subcarriers OFDM system with the proposed method. Moreover, this system will be evaluated under the effect of AWGN channel. The results exhibit the ability of such technique to reduce the PAPR without major effect on the system performance as compared with the conventional OFDM technique. The PAPR of OFDM signal is further reduced by 4–5 dB by this technique.


Article
High Rate Data Processing System of 6x6 MIMO_OFDM Using FPGA Technique with Spatial Algorithm

Author: Muthna J. Fadhil
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2018 Volume: 36 Issue: 7 Part (A) Engineering Pages: 723-732
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

OFDM has high spectral Performance and pliability in multipath channel effects while MIMO use another strategy for saving power of transmitter by using multi in multi out antennas to make throughput processing in high efficiency. The transceiver MIMO OFDM implemented on an FPGA typeSpartan3 XC3S200 with proper algorithm, Invoke method and QPSK modulation. The project prospective to improve the transceiver operations in terms of data transmission in high speed and saving power for wireless communication system take in consideration the cost of implementation hardware. In the result registered throughput data rate 425 Mbps using spatial algorithm (ICA with SD algorithm) with another advantage reduction in PAR by 6db and BER less than 10-7).The total architecture using 61% slice registers, LUT's of 55% and memory about 67% on board of Spartan-3 XC3S200.


Article
Reduction of Peak to Average Power Ratio in OFDM System Using Discrete Cosine Transform Technique

Author: Ahmed K. Abed احمد كاظم عبد
Journal: University of Thi-Qar Journal for Engineering Sciences مجلة جامعة ذي قار للعلوم الهندسية ISSN: 26645564/26645572 Year: 2010 Volume: 1 Issue: 2 Pages: 41-54
Publisher: Thi-Qar University جامعة ذي قار

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Abstract

Orthogonal frequency division multiplexing (OFDM) is a form of multi-carriermodulation technique with high spectral efficiency, robustness to channel fading andimmunity to impulse interference. Recently, it is being used for both wireless and wired highdata rate communications. Despite of its many advantages, OFDM has a main drawback,namely high Peak to Average Power Ratio (PAPR).High PAPR causes saturation in poweramplifiers, and leads to inter-modulation products among the sub carriers and disturbing outof band energy. Therefore, it is desirable to reduce the PAPR. In this paper we used InverseDiscrete Cosine Transform (IDCT) technique in the transmitter side to reduce PAPR problem.The use of this technique in the output of Inverse Fast Fourier Transform (IFFT) stage gavegood results toward reduction PAPR. The receiver side includes Discrete Cosine Transform toachieve correct detection. Computer simulation tests have been applied on IEEE 802.11astandard as OFDM practical system with the proposed method .The results exhibit the abilityof such techniques to reduce the PAPR with no major effect on the system performance ascompared with the conventional OFDM technique.

یُعد الإرسال المتعدد بتقسیم التردد المتعامدللإرسال اللاسلكي OFDM متعدد الحامل و مقاوم إلى خفوت القناة والحصانة من التداخل. حدیثا, استخدم نظامیمتلك عیب OFDM , وللاتصالات السلكیة الرقمیة ذات معدل الإرسال العالي. على الرغم من المحاسن الكثیرة للنظامیجعل المكبرات تعمل بمنطقة التشبع , مما یؤدي PAPR ارتفاع .PAPR رئیسي ھو ارتفاع نسبة أعلى إلى معدل القدرةإلى التداخل بین النواقل الفرعیة في النطاق الترددي و الإرسال الغیر المرغوب بھ خارج النطاق المحدد. لذلك أصبح من المرغوب بھ تقلیل ارتفاع نسبة أعلى إلى معدل القدرةان استخدام ھذه التقنیة من بعد إخراج معكوس .OFDM في نظام PAPR في جھة الإرسال لتقلیل مشكلة IDCT المجزئةجھة الاستقبال تضمنت استخدام تحویلة الجیب تمام .PAPR تحویلة فوریر السریعة أعطت نتائج جیدة باتجاه تقلیل802.11 كنظام معتمد عملیا a IEEE للكشف الصحیح للبیانات. تمت محاكاة النظام المقترح ضمن نظام DCT المجزئةبدون حدوث أي تأثیر رئیسي على أداء PAPR باستخدام الحاسوب . النتائج أظھرت قدرة النظام المقترح لتقلیل ارتفاعالتقلیدي


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.


Article
PAPR Reduction of OFDM Signals Using Clipping and Coding
تخفيفض قيمة PAPR لاشارات OFDM باستعمال القطع والترميز

Author: Mohammed Kasim Al-Haddad محمد قاسم محمد
Journal: Journal of Engineering مجلة الهندسة ISSN: 17264073 25203339 Year: 2014 Volume: 20 Issue: 8 Pages: 18-34
Publisher: Baghdad University جامعة بغداد

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Abstract

The problem of the high peak to average ratio (PAPR) in OFDM signals is investigated with a brief presentation of the various methods used to reduce the PAPR with special attention to the clipping method. An alternative approach of clipping is presented, where the clipping is performed right after the IFFT stage unlike the conventional clipping that is performed in the power amplifier stage, which causes undesirable out of signal band spectral growth. In the proposed method, there is clipping of samples not clipping of wave, therefore, the spectral distortion is avoided. Coding is required to correct the errors introduced by the clipping and the overall system is tested for two types of modulations, the QPSK as a constant amplitude modulation and 16QAM as a varying amplitude modulation.

في هذا البحث دُرست مشكلة ارتفاع نسبة القمة الى المعدل القدرة PAPR في اشارات OFDM مع استعراض مختصر للطرق المختلفة المستعملة للتقليل الـ PAPR والتركيز على طريقة القطع. تم تقديم طريقة بديلة للقطع حيث يُجرى القطع بعد مرحلة الـ IFFT بعكس الطريقة التقليدية للقطع حيث يُجرى القطع في مرحلة مكبر القدرة والتي تولد نمو الطيف خارج الحزمة الخاصة بالاشارة. في الطريقة المقترحة تم قطع العينات وليس الموجة لذلك يتم تجنب تشويه الطيف. تكون الحاجة الى الترميز لاجل تصحيح الاخطاء المتولدة بسبب القطع وقد تم اختبار المنظومة ككل على تحميل QPSK الذي هو ذو سعة ثابتة وتحميل 16QAM الذي هو ذو سعة متغيرة.


Article
A LOW COMPLEXITY SLM SCHEME FOR PAPR REDUCTION OF OFDM SIGNALS

Authors: Abdulrahman Ikram Siddiq عبدالرحمن اكرام صديق --- Omar Mohammed Salih عمر محمد صالح
Journal: DIYALA JOURNAL OF ENGINEERING SCIENCES مجلة ديالى للعلوم الهندسية ISSN: 19998716/26166909 Year: 2017 Volume: 10 Issue: 3 Pages: 63-74
Publisher: Diyala University جامعة ديالى

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Abstract

The selected mapping (SLM) is an effective technique for peak-to-average power reduction (PAPR) of orthogonal frequency division multiplexing (OFDM) signals. SLM has high computational complexity due to the computation of multiple IFFTs. In this paper, low complexity SLM is proposed based on a novel simplified IDFT algorithm developed such that it does not involve any complex arithmetic. The proposed SLM, with U candidate signals, achieves a computational complexity reduction ratio of (1-□(1/U))% with respect to traditional SLM. This reduction is at the expense of using limited memory and negligible degradation in PAPR reduction performance. The computational core of the proposed SLM is implemented on the Spartan 3E XC3S500E FPGA platform to highlight its hardware implementation issues and to verify its effectiveness.

تعتبر تقنية التنظيم المختار (SLM) من الطرق الفعالة في تقليل نسبة الذروة الى المعدل (PAPR) لقدرة الاشارات المرسلة في انظمة التضمين ذات القنوات المتعددة المتعامدة (OFDM). و لكن درجة تعقيد الحسابات لتقنية (SLM) عالية نسبيا بسبب تظمنها لعملية حساب محول فورير العكسي لعدة مرات لتوليد عدد من الاشارات المرشحة للارسال. في هذا البحث، تم اقتراح طريقة لتخفيض تعقيد تقنية (SLM) بالاعتماد على اقتراح خوارزمية مبسطة لمحول فورير العكسي لا تتضمن اية حسابات مركبة. ان تقنية (SLM) المقترحة التي تولد U من الاشارات المرشحة للارسال، تحقق نسبة تخفيض في درجة تعقيد الحسابات تقدر بـ (1-□(1/U))% بالمقارنة مع التقنية التقليدية. هذه النسبة لا تعتمد على عدد النواقل و لكنها تكون على حساب الحاجة لاستخدام ذاكرة بمساحة خزن محدودة و انخفاض طفيف في اداء تخفيض (PAPR). تم نتفيذ التقنية المقترحة باستخدام مصفوفة البوابات القابلة للبرمجة Spartan 3E XC3S500E FPGA لتسليط الضوء على تفاصيل التنفيذ العملي لها و للتحقق من فعاليتها.الكلمات المفتاحية: تقنية التنظيم المختار (SLM)، نسبة الذروة الى المعدل للقدرة (PAPR)، انظمة التضمين ذات القنوات المتعددة المتعامدة (OFDM)، محول فورير العكسي المبسط، مصفوفة البوابات القابلة للبرمجة (FPGA)

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