نتایج جستجو برای: FFT-OFDM
تعداد نتایج: 15949 فیلتر نتایج به سال:
Orthogonal frequency division multiplexing (OFDM) is used in order to provide immunity against very hostile multipath channels in many modern communication systems.. The OFDM technique divides the total available frequency bandwidth into several narrow bands. In conventional OFDM, FFT algorithm is used to provide orthogonal subcarriers. Intersymbol interference (ISI) and intercarrier interferen...
Last years, Wavelet Packet Modulation (WPM) or Wavelet Packet Transform based Orthogonal Frequency Division Multiplexing (WPT-OFDM) have been introduced to wired and wireless communication fields as efficient Multicarrier Modulation (MCM) techniques. The wavelets have interesting features such as flexibility, compatibility and localization in both time and frequency domains with no need to use ...
چکیده : ofdm یک تکنیک مدلاسیون برای ارسال داده با سرعت بالا در کانال محو شدگی چند مسیره است. مهم ترین عاملی که سیستم های siso-ofdm (single-input single output ofdm) را با مشکل مواجه می سازند منابع تداخل می باشد. به منظور حذف تداخل استفاده از آنتن های آرایه ای در گیرنده سیستم های ofdm پیشنهاد شده که simo-ofdm (single-input multiple-output - ofdm) نامیده می شود. یکی از راههای افزایش ظرفیت کانال ...
Beamforming methods using antenna arrays have been used to suppress co-channel interferences in OFDM systems. These methods are grouped into two general classes of pre-FFT and post-FFT schemes. Post-FFT schemes normally exhibit better performance than their pre-FFT counterparts. However, in pilot-assisted OFDM systems the performance of post-FFT schemes drastically degrades due to subcarrier cl...
OFDM is an efficient modulation technique for wideband digital communication. A major drawback of OFDM modulation is the high Peak-to-Average Power Ratio (PAPR) of the transmitted signal which limits its transmission range of communication. As PAPR increases it reduces the average power which affect on total power consumption of Transmitter. Normally, OFDM is implemented using FFT. In recent ye...
Orthogonal frequency division multiplexing (OFDM) is a popular method for wireless transmission of data at high rate. To increase the speed of transmission, the input high rate data stream is divided into many small data streams which are then transmitted parallel in OFDM system. The key component of OFDM system is the FFT processor. FFT converts the input time domain signal into frequency doma...
OFDM technology promises to be a key technique for achieving the high data capacity and spectral efficiency requirements for wireless communication systems in future. Fast Fourier transform (FFT) processing is one of the key procedures in popular orthogonal frequency division multiplexing (OFDM) communication systems. A parallel and pipelined Fast Fourier Transform (FFT) processor for use in th...
یکی از مهم ترین مشکلات سیستم های ofdm عدم توانایی این سیستم ها در حذف سیگنال تداخل در باند فرکانسی سیگنال مطلوب می باشد. برای حذف این تداخلات از روش های شکل دهی پرتو استفاده می شود. دو روش مرسوم شکل دهی پرتو، روش pre-fft (شکل دهی پرتو در حوزه زمان) و روش post-fft (شکل دهی پرتو در حوزه فرکانس) می باشند. برای به روزرسانی وزن ها در هر دو روش راه حل های مختلفی پیشنهاد شده است که می توان همه آن ها ر...
1. Mrs.Veena M.B. Dr.M.N.ShanmukhaSwamy,“Performance analysis of DWT based OFDM over FFT based OFDM and implementing on FPGA” International Journal of VLSI design & Communication Systems (VLSICS) Vol.2, No.3, September 2011. 2. Deepak Gupta, Vipin B Vats, Kamal K. Garg, “Performance Analysis of DFT-OFDM, DCT-OFDM, and DWT-OFDM Systems in AWGN Channel” International Conference on Wireless and Mo...
Multiple Input Multiple output (MIMO) antennas can be combined with orthogonal frequency division multiplexing (OFDM) to ensure spatial diversity gain and/or to increase spectral efficiency. MIMO communication system with Alamouti methods can improve the bit error rate (BER) and signal to noise ratio (SNR) thus distortions are reduced for higher data rate. Conventionally OFDM is Fast Fourier Tr...
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