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Register a new userOrthogonal Frequency Division Multiplexing [OFDM]
دراسة تقنية OFDM
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Created by
Ashraf Kasem
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مع التطور المتسارع لتقنيات الاتصال , والطلب المتزايد على ارسال واستقبال المعلومات مهما كان نوعها بالسرعة والدقة العالية ادعت الحاجة الى تطوير اساليب ضغط ونقل واستقبال ومعالجة المعلومات من اجل تغطية كافة الاحتياجات المتزايدة من حين الى اخر . في هذا العمل يتم عرض نظام (تقنية) OFDM المتبعة او التي تشكل العمود الفقري في انظمة LTE ((الجيل الرابع)) التي هي بشكل مختصر انظمة اتصالت لاسلكية . الهدف هو عرض ما تقدمه هذه التقنية من ايجابيات وسلبيات وعرض ايضا بعض التطبيقات التي تستخدم هذه التقنية . اعتمدت في هذا العمل على بعض الكتب العلمية المرفقة في قائمة المراجع بالاضافة الى استخدام رسوم توضيحية بعضها من تلك المراجع ولقسم الاكبر تم تحريره عن طريق برامج الرسوم الشهيرة على الحاسب والغاية من ذلك هي تبسيط الرسوم الى درجة توضيح الفكرة المطلوبة منها فقط او التي اردت ايصالها من دون غيرها .
No English abstract
References used
[1] WIRELESS COMMUNICATIONS AND NETWORKS Second EDITION Williant Stallings.
[2] DIGITAL COMMUNICATIONS Fundamentals and Applications Second Edition BERNARD SKLAR.
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This thesis mainly discusses how to embed and transmit information in audio by making use of acoustic OFDM. Based on the theoretical systematic structure, it also modeled and simulated the system under different communication channels such as AWGN and Rayleigh fading, using the MATLAB software.
A common challenge in designing a wireless system is to overcome
the effects of the wireless channel, such as multi-path propagation,
and Inter-symbol Interference. and the ability of OFDM to combat
the effects of multi-path propagation made it th
e modulation of
choice for third and fourth generation networks.
In OFDM system we transmit data symbols on a large number of
subcarriers, and these data symbols exposed to changes in
amplitude and phase, caused of noise and frequency selective
fading and Doppler shift .
To get the transmitted data at the receiver we must cope with these
changes, so we need to know the channel response at every
subcarrier and every symbol, and for that reason we use PILOTS
and we use many methods to estimate the channel response depend
on pilots, and the most important channel is LMMSE Method.
We will discuss in these issue the wiener filtering method
(LMMSE) which give best performance but it is very complicated,
so we will use Discrete Fourier Transform (DFT) to reduce the
complexity of these method and we will study the BER and MSE in
both case when we use QPSK or 16QAM Modulation .
This research proposes the development of Optical Network Units by introducing an
all optical Filter. This optical filter can treat WDM and PDM technology at the same time
enabling us to send a channel on the horizontal and vertical of the same wav
elength .The
hybrid WDM-PDM technology allows to delivery double channels for users without any
changing in infrastructure between optical central office and user . Firstly , this article
prove the idea of hybrid WDM-PDM technology by OptiSystem7.0 simulator, secondly we
study proposed all optical Filter for three cases of optical access: WDMPDM(
Downstream), WDM(Downstream)/( TDM(Upstream) , WDM(Downstream)/
WDM(Downstream) recommended by the international communication federation, ICF.
This research offers an analyzing study for BER in OFDM system through Module
designed by matlab, the performance was tested with different modulation techniques as
PBSK, 8PBSK….
The measurement was taken at multi AWGN levels for different modulat
ion
techniques besides BER testing in Rayleigh fading channel and without Rayleigh fading
All results illustrated in suitable tables and curve.
This work aims to analyze the performance of Orthogonal Frequency Division
Multiplexing (OFDM) applied in the fourth generation mobile networks and WiFi. Fuzzy
logic technique is used in this study to analyze the problem of OFDM, taking into
consi
deration the modulation techniques applied in OFDM. Three input parameters in the
fuzzy logic system are mainly considered: signal-to-noise ratio, the modulation degree and
the number of sub-carriers. The output parameters are selected to be the bandwidth and bit
error rate. This requires an analytical study to determine the optimal values of the input
parameters used in this study. This means studying the membership of functions of each
input and output parameter using fuzzy logic.
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