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Article
PERFORMANCE STUDY OF OFDM BASED ON IP-WT
دراسة أداء مازج تقسيمات التردد المتعامدة بالاعتماد على في-مكان لتحويل الويفليت

Author: Salih M. Salih صالح محمد صالح
Journal: Journal of university of Anbar for Pure science مجلة جامعة الانبار للعلوم الصرفة ISSN: ISSN: 19918941 Year: 2008 Volume: 2 Issue: 1 Pages: 131-138
Publisher: University of Anbar جامعة الانبار

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Abstract

In this paper, a proposed model based on In-Place Wavelet Transform (IP-WT) was suggested to improve the performance of the Orthogonal Frequency Division Multiplexing (OFDM) under the Additive White Gaussian Noise (AWGN), and flat fading channel. The proposed model does not require additional arrays at each sweep such as in the ordered Haar wavelet transform; this ensures fast processing time with minimum memory size. The results extracted by a computer simulation and compared with the performance of the conventional model based on Fast Fourier Transform (FFT). As a result, it can be seen that the proposed technique has high performance improvement over the conventional OFDM system based FFT, where the Bit Error Rate (BER) is widely reduced under these models of channels.

تحت تأثير قناة الضوضاء (OFDM) في هذا البحث تم اقتراح نموذج لتحسين أداء مازج تقسيمات التردد المتعامدةبالاعتماد على في- مكان لتحويل الويفليت وقناة الخبو المنبسط . ان النموذج (IP-WT) الابيض التراكمية لكاوزمرحلة معالجة للإشارة مثلما يحتاجه تحويل (AWGN) المقترح لايحتاج الى مصفوفة إضافية عند كل مستوى منحجم للذاكر ة .تم مقارنة النتائج مع اداء .(FFT) الويفليت المرتب؛ وبالتالي فان سرعة المعالجة ستزداد وبأقلالنموذج الاعتيادي المعتمد على تحويل الفوري السريع النتائج بينت ان النموذج المقترح قد اعطى تحسن عاليبالاداء نسبة الى النموذج الاعتيادي ، حيث انقل بشكل كبير تحت تأثير تلك النماذج من القنوات.

Keywords

In-Place --- QAM --- OFDM --- AWGN --- Flat Fading


Article
Enhancement the Performance of HiperLAN/2 Physical Layer Based DWT-OFDM
تحسين أداء الطبقة الفيزيائية (HiperLAN/2 ) المبنية على مضاعفة تقسيم التردد المتعامد لتحويل المويجات

Authors: Hazim Salah Abdulsatar حازم صلاح عبدالستار --- Tahseen Flaih Hassan تحسين فليح حسن
Journal: Journal of Al-Ma'moon College مجلة كلية المأمون ISSN: 19924453 Year: 2015 Issue: 26 Pages: 303-318
Publisher: AlMamon University College كلية المامون الجامعة

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Abstract

The proposed model based on Discrete Wavelet Transform (DWT) for OFDM , was suggested to improve the performance of HiperLAN/2 transceiver that lies under the Additive White Gaussian Noise (AWGN), multipath fading,and selective fading channels. This model is used to reduce the effect of multipath fading. The results extracted by a computer simulation for a model proposed, and then it is compared with the original technique for HiperLAN/2 transceiver based on DWT for both systems. As a result, it can be seen from the proposed technique that a high performance improvement was obtained over the conventional HiperLAN/2 transceiver, where the Bit Error Rate (BER) is widely reduced under the AWGN, flat fading, and selective fading channels.

هذا البحث مقترن بموديل مقترح مستند على مضاعفة التقسم للتردد المتعامد للتحويل المحدد لمويجات OFDM لتحسين أداء HIPERLAN / 2 بجهاز الإرسال والاستقبال تحت تاثير الضوضاء المضافة البيضاء (AWGN)، قناة التلاشي المتعددة، وقنوات التلاشي الانتقائية. النتائج المستخرجة من برنامج المحاكاة للنموذج المقترح، وبعد ذلك مقارنتها مع التقنية الأصلية لHIPERLAN / 2 لجهاز الإرسال والاستقبال DWT لكلا النظامين. ونتيجة لذلك ، نستنتج ان التقنية المقترحة تم الحصول بواسطتها على تحسن الأداء العالي 2/ الإرسال والاستقبال ، حيث يتم تخفيض نسبة الخطأ بت ( BER) تاثير قنوات الضوضاء المضافة البيضاء ، قنوات التلاشي متعددة المسارات وقنوات التلاشي الانتقائية .

Keywords

HiperLAN/2 --- AWGN --- BER --- OFDM --- DWT.


Article
Bit error probability curve for BPSK in ISI channel with MMSE equalizer
منحني احتمالية الخطأ BPSK لحساب التداخل باْستخدام معادل MMSE

Author: Mowafak Khadom Mohsen
Journal: journal of kerbala university مجلة جامعة كربلاء ISSN: 18130410 Year: 2016 Volume: 14 Issue: 2 Pages: 64-71
Publisher: Kerbala University جامعة كربلاء

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Abstract

Theory coding is methods to study for effective and exact transfer the information from point to another point. This theory had been advanced for example many applications as to decreasing the noise from received signal, when the transmission of most information in telephone line, information transfer from terminal (computer) to another terminal or from any memory to the main processor and data transmission from transmitter such as satellite communication which led images of Saturn earth. A channel is mien physical medium which the data or (information) transmission. Disturbances undesirable called noise. This noise caused the differ the information signal from the transmitted data. Noise may be caused folds in a tap magnetic, telephone competing messages, sunspots, meteor showers, lightning, radio random disturbance or other many things.In my paper I used the MATLAB program to simulations over AWGN channel by using BPSK modulation scheme I notice when used more tap point I get the decreases for bit error rate and this method one of theory coding deals with problem of correcting and detecting error transmission caused by noise in channel. In practice, we has over this noise that mast choice of good a channel to use the transmission data (information) and to used variable noise filters to combatable certain type of interference may be cannot be controlled.

نظرية الترميز هي احدى طرق البحث عن فعالية ونقل المعلومات والبيانات من نقطة إلى نقطة أخرى وبدقة عالية جدا. وقد طرحت هذه النظرية على سبيل المثال في العديد من التطبيقات لخفض الضجيج من الأشارة المستلمة او المرسلة، كما في نقل البيانات و المعلومات في خط الهاتف، وكذلك نقل المعلومات من محطة (الكمبيوتر) إلى محطة أخرى أو من أي الذاكرة إلى المعالج ونقل البيانات الأساسية في الارسال مثل الاتصالات عبر الأقمار الصناعية والصور الفضائية. وعند عملية النقل تتأثر هذه الاشارات بأشارات اخرى غير مرغوب بها تسمى الضوضاء والتي تسبب ضعف او تشويه للأشارة المستلمة او المرسلة. قد يكون سبب الضوضاء اشارات من اجهزة مغناطيسية او رسائل هاتفية اخرى أو أشياء أخرى عديدة.في هذا البحث أنا استخدم برنامج MATLAB لمحاكاة على قناة AWGN باستخدام BPSK واستخدام أكثر من نقطة لغرض الحصول على انخفاض لمعدل الخطأ وهذا أسلوب واحد من نظرية الترميز يتناول مشكلة تصحيح وكشف الخطأ في البيانات الناتج عن الضوضاء في القناة وبطريقة عملية، ويوجد لدينا أكثر من نوع للضوضاء

Keywords

coding theory --- AWGN --- BER --- BPSK and ISI


Article
A Proposed Improvement Model for MC-CDMA in Selective Fading Channel
نموذج مقترح لتحسين اداء الحاملات المتعددة-الوصول المتعدد المقسم بالترميز بقناة الخبو الانتقائي

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Abstract

In this paper, a proposed model based on phase matrix rotation was suggested to improve the performance of Multicarrier-Code Division Multiple Access (MC-CDMA) lies in Fast Fourier Transform (FFT) algorithm under the Additive White Gaussian Noise (AWGN) and frequency selective fading channel. This model is used to reduce the effect of multipath fading. The results extracted by a computer simulation for a single user, then it compared with the original technique for MC-CDMA based on FFT for both systems. As a result, it can be seen from the proposed technique that a high performance improvement was obtained over the conventional MC-CDMA, where the Bit Error Rate (BER) is widely reduced under different channel characteristics for frequency selective fading and the AWGN channel

في هذا البحث, تم اقتراح نموذج جديد لتحسين اداء الحاملات المتعددة-الوصول المتعدد المقسم بالترميز (MC-CDMA) بالاعتماد على مصفوفة الفيز الدوار للنموذج المعتمد على تحويل الفورير بقناة الضوضاء الابيض المضافة لكاوز (AWGN) وقناة الخبو الانتقائي للترددات. ويستخدم هذا النموذج لتقليل تاثير الخبو الناتج من الانعكاسات المختلفة للاشارة اللاسلكية. النتائج تم استخراجها رياضيا باستخدام الحاسبة الالكترونية لمستخدم واحد فقط, وتمت مقارنتها مع اداء النموذج الاصلي المعتمد على تحويل الفورير السريع. النتائج بينت وجود كسب كبير بالاشارة تم الحصول عليه من النموذج المقترح مقارنة بالنموذج الاصلي, حيث ان نسبة الخطا بالبتات (BER) قلت بشكل كبير تحت تاثير مختلف البارامترات للقنوات اللاسلكية عند قنوات الخبو الانتقائي وقناة الضوضاء الابيض المضافة لكاوز

Keywords

MC-CDMA --- AWGN --- BER --- Phase Matrix --- Selective Fading


Article
Joint Hybrid Compression Techniques and Convolutional Coding for Wireless Lossy Image Transmissions

Authors: Salah Al-iesawi1 --- Maha Abd Rajab2 --- Ahmed I. A.3
Journal: IRAQI JOURNAL OF COMPUTERS,COMMUNICATION AND CONTROL & SYSTEMS ENGINEERING المجلة العراقية لهندسة الحاسبات والاتصالات والسيطرة والنظم ISSN: 18119212 Year: 2015 Volume: 15 Issue: 1 Pages: 80-99
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

Abstract – This paper demonstrates the effect of color image transmission through AWGN channel using binary phase shift key modulation (BPSK) system and transmission of compressed color image through AWGN. On the other hand, the transmission consumes a large amount of channel and needs the processing, therefore utilizes compression techniques to reduce the size of the original color image to facilitate the transmission compressed color image through AWGN and to obtain the channel optimization. In this paper, a simple hybrid lossy color image compression transmission through AWGN using convolutional coding with Viterbi decoding system is proposed. It is based on combining effective techniques, started by wavelet transform that decompose the image signal followed by polynomial approximation model of linear based to compress approximation image band. The error caused by applying polynomial approximation is coded using bit plane slice coding, whereas the absolute moment block truncation coding exploited to coded the detail sub bands. Then, the compressed information encoded using LZW, run length coding and Huffman coding techniques, the compressed information is entered to the channel coding to coded the information using convolutional coding and modulation using BPSK to transmit through channel and added AWGN, the received signal is demodulated and decoded using Viterbi decoding, the result compressed data passed to source decoding to reconstruct the compressed image. The test results indicated that the proposed system can produce a balance between the compression performance and preserving the image quality, and also simulations results observed that with increase in signal to noise ratio (SNR) values the bit error rate (BER) values decrease.


Article
Implement Wireless Transceiver System Based On Convolutional Coding; Aided by Soft-Bit Decoding

Author: Israa Hazem Ali
Journal: IRAQI JOURNAL OF COMPUTERS,COMMUNICATION AND CONTROL & SYSTEMS ENGINEERING المجلة العراقية لهندسة الحاسبات والاتصالات والسيطرة والنظم ISSN: 18119212 Year: 2018 Volume: 18 Issue: 1 Pages: 49-55
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

The main aim with any modern digital communication systems is to provide error free data transmission. To achieve this aim, error control coding techniques are applied with these systems. In this paper, digital communication system was implemented based on convolutional code, aided by soft-bit decoding for error free transmission. Fixed length source encoder was represented with this work, and statistically described the output of the source encoder and save this description at the receiver as a priori knowledge about the source encode. These a priori knowledge were exploited at the receiver to improve the performance of the proposed system in term of BER by conceal the errors occurred through the transmission of information over AWGN channel, aided the convolutional encoder. Significant improvements were obtained with this proposed system.


Article
BIT ERROR OPTIMIZATION OF CODED OFDM SYSTEM OVER RAYLEIGH FADING CHANNEL

Authors: Awatif Ali Jafaar --- Zainab Majeed Abid
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2019 Volume: 23 Issue: 4 Pages: 76-85
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

Low Density Parity-Check (LDPC) codes are one of the hottest topics in coding theory today. This code invented in the early 1960's, and it having an amazing comeback in the last few years. In this paper, a scheme is proposed to analyze the performance of LDPC which is considered important rival to turbo codes, Convolutional Code (CC) and Read Solomon (RS) in terms of performance and complexity. This code is utilized in Orthogonal Frequency Division Multiplexing (OFDM) system to evaluate the improvement in the Bit Error Rate (BER) performance of the system. Comparison is done between turbo code and LDPC code through Additive White Gaussian Noise (AWGN) and fading channels. The effect of varying the code rate channel, number of iteration and the code length on the performance of the scheme are also explained.

Keywords

OFDM --- LDPC --- Turbo code --- BPSK --- AWGN --- Fading channel.


Article
A Review for the Adopted Techniques in Low SNR Communication Systems

Authors: Dhafer R. Zaghar --- Hadeel N. Abdullah --- Ikhlas M. Farhan
Journal: IRAQI JOURNAL OF COMPUTERS,COMMUNICATION AND CONTROL & SYSTEMS ENGINEERING المجلة العراقية لهندسة الحاسبات والاتصالات والسيطرة والنظم ISSN: 18119212 Year: 2020 Volume: 20 Issue: 1 Pages: 40-52
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

The study and evaluation of digital communication systems in low signal-to-noise power ratio (LSNR) environments is a hot and important topic due to its wide contemporary applications. This review is an attempt to focus on the most distinctive vital parameters required in the analysis and design of such systems. It includes a brief literature survey for many algorithms, techniques, methodologies, and mitigations that have been used to overcome the high noise problem encountered in these systems in order to guarantee reliable communication. Amongst these topics, the study reviews the most widely utilized modulation techniques in LSNR communication systems such as the On-Off Keying (OOK) and binary PSK schemes. The capacity for both AWGN and wireless fading channels is also discussed along with a clarification of the minimum limits in these types of channels.On the other hand, some important and recommended detection and estimation techniques for low power communication systems are briefly covered. This unified study has additionally discussed spectral efficiency and bit energy trade-off within the low-power, and broadband systems, and different limitations are stated clearly. Finally, the survey throughout this paper recommends some significant techniques that can be used in the analysis and design of successful communication systems in LSNR regimes.


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
MULTICARRIER CODE DIVISION MULITPLE ACCESS BASED ON WAVELET

Authors: Dr. Saad N. Abdul Majed --- Prof. Dr. Walid A. Mahmoud
Journal: Journal of Baghdad College of Economic sciences University مجلة كلية بغداد للعلوم الاقتصادية الجامعة ISSN: 2072778X Year: 2007 Issue: 15 Pages: 363-368
Publisher: Baghdad College of Economic Sciences كلية بغداد للعلوم الاقتصادية

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Abstract

In this paper an alternative strategies will be demonstrated that mitigate interference without relying on the fact that the effective channel is shorter than the CP. Wavelet-based MC-CDMA has gained popularity in the literature recently. Due to very high spectral containment properties of wavelet filters, wavelet-based MC-CDMA can be better combat narrowband interference and is inherently more robust with respect to ICI than traditional FFT filters. The classic notion of a guard band does not apply for (DWT-MC-CDMA), hence data rates can enhanced those of FFT implementations.

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