Desing and Simulation of Ofdm Research Papers (original) (raw)

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- Design, Desing and Simulation of Ofdm

The WiMAX technology, based on the IEEE 802.16-2004 Air Interface Standard is rapidly proving itself as a technology that will play a key role in fixed broadband wireless metropolitan area networks. The first certification lab, established at Cetecom Labs in Malaga, Spain is fully operational and more than 150 WiMAX trials are underway in Europe, Asia, Africa and North and South America. Unquestionably, Fixed WiMAX, based on the IEEE 802.16-2004 [1] Air Interface Standard, has proven to be a cost-effective fixed wireless alternative to cable and DSL services. In December, 2005 the IEEE ratified the 802.16e amendment [2] to the 802.16 standard. This amendment adds the features and attributes to the standard necessary to support mobility. The WiMAX Forum is now defining system performance and certification profiles based on the IEEE802.16e Mobile Amendment and, going beyond the air interface, the WiMAX Forum is defining the network architecture necessary for implementing an end-to-end...

- by mukesh patidar
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- Electrical Engineering, Wireless Communications, IEEE 802.16 (WiMAX), OFDM

It is fascinating to know that the multiplexing can be employed and defined
from different points of views and different disciplines. For example, Dr. E. Julius
Dasch, former manager of the NASA National Space Grant Program, defines multiplexing on his dictionary book [1] as:
…the simultaneous transmission of different data from a spacecraft using a single
channel. The data stream is separated into frames that carry codes for different
information, such as temperatures, pressures, and the state of on-board computers.
In a media and communication dictionary book [2], multiplexing is mentioned as:
Digital television transmission allows for multiplexing, whereby multiple channels
are bundled together and sent simultaneously in a single stream of data.
In a computer science dictionary book [3], multiplexing is described as:
…the process of combining multiple messages simultaneously on the same physical or
logical transmission medium. There are two main types: time division multiplexing
(TDM) and frequency division multiplexing (FDM).
The list continues for the Internet, optic engineering, graphics, phytography,
laser and photonics geology, earth sciences, and many more.

- by Johan Lopez
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- Desing and Simulation of Ofdm

This paper details on the employment of modern, computer-based development tools for the achievement of full real-life experimental frameworks for educational or research purposes. This is achieved through the study, design, implementation and presentation of some initial results, of an OFDM (Orthogonal Frequency Division Multiplexing) transceiver. The design and implementation is done using the TMS320C6713 DSK development kit from "Texas Instruments Inc", in conjunction with Matlab-Simulink from "Mathworks Inc.". This procedure can easily be adopted for the development of several other systems at the domain of communications and signal processing.

The high data transmission rates in the communication channel is a recent growing demand which is achieved by using the multiple input multiple output systems because of their unique properties.. The OFDM systems that adopt the cyclic require only one inverse discrete Fourier transform (IDFT) operation at the low-complexity by means of increasing the transmission diversity in MIMO pilot sequences which minimize the mean square error (MSE) of the channel estimate in traditional MIMO systems are inapplicable to CDD minimum MSE of both the least square (LS) channel estimate and the MMSE channel estimate in CDD systems. The derived criteria are then used to develop a general methodology for determining the sequence. Significantly, the proposed design methodology enables the status of the channel to be estimated using single OFDM symbol. We have compared the performances of channel estimation algorithm by measuring bit error rate vs. SNR with BPSK, QPSK 16

Cholesky factorization is the modified version of the Gaussian elimination. Cholesky factorization is a positive definite, symmetric matrix where matrix A is the product of a lower triangular matrix L and its transpose. Lower triangular portion of A is stored in the lower triangle of two dimensional array and computed elements of L overwrites the given elements of A. This matrix uses the half space of memory for storage as required by the general matrix. This paper proposed different techniques for the VLSI implementation of Cholesky decomposition and also analyzes the different options for its FPGA implementation. INTRODUCTION Systems of linear equations arise in large number of areas, both directly in modeling physical situation and indirectly in the numerical solution of other mathematical models. Excellent algorithms have been developed for the most common types of linear systems. The most common type of problem is to solve square linear system Ax = b of moderate order, with coefficients are mostly nonzero. Such linear system of any order is called dense. For such systems, the coefficient of A must generally stored in the main memory of the computer in order to efficiently solve the linear system and thus, memory storage limitations in most computers will limit the order of the system. With the rapid

- by NAVEEN RATHEE
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- Desing and Simulation of Ofdm, QPSK OFDM, OFDM in FPGA
- by Brian Villa
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- Desing and Simulation of Ofdm

Robot, Tasarım, Basit Örnekleme, Dizayn, Kodlama, Otomasyon Örneği, Programlama, Mekanik, Elektronik, Gövdeleme

- by Fatih DİKMEN
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- Robotics, Mechatronics & Robotics, Comics and Graphic Novels, SUMO

Radio-over-Free-Space-Optics (Ro-FSO) is a promising technology for future wireless networks. In this work, we have designed a hybrid orthogonal frequency division multiplexing (OFDM) Ro-FSO system for transmission of two independent channels by mode division multiplexing. Two independent 40 GHz radio signals are optically modulated at 20Gbps by mode division multiplexing of two laser modes LG00 and LG10 and transmitted over a free-space link of 20 km to 100 km. The performance of proposed Ro-FSO system is also evaluated under the effect of strong atmospheric turbulences

Orthogonality of Carriers in OFDM and its system design.

- by sandeep garg
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- Wireless Communications, Desing and Simulation of Ofdm

Growth in technology has led to unprecedented demand for high speed architectures for complex signal processing applications. In 4G wireless communication systems, bandwidth is a precious commodity, and service providers are continuously met with the challenge of accommodating more users with in a limited allocated bandwidth. To increase data rate of wireless medium with higher performance, OFDM (orthogonal frequency division multiplexing) is used. Recently DWT (Discrete wavelet transforms) is adopted in place of FFT (Fast Fourier transform) for frequency translation. Modulation schemes such as 16-QAM, 32-QAM, 64-QAM and 128-QAM (Quadrature amplitude modulation) have been used in the developed OFDM system for both DWT and FFT based model. In this paper we propose a DWT-IDWT based OFDM transmitter and receiver that achieve better performance in terms SNR and BER for AWGN channel. It proves all the wavelet families better over the IFFT-FFT implementation. The OFDM model is developed using Simulink, various test cases have been considered to verify its performance. The DWT-OFDM using Lifting Scheme architecture is implemented on FPGA optimizing hardware, speed & cost. The wavelet filter used for this is Daubechies (9, 7) with N=2. The RTL code is written in Verilog-HDL and simulated in Modelsim. The design is then synthesized in Xilinx and implemented on Virtex5 FPGA board and the results were validated using ChipScope.

- by shanmukha swamy
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- Henri Bergson, Bertrand Russell, OFDM, OFDMA

Filter bank multicarrier (FBMC) is considered a competitive waveform candidate for 5G that can replace orthogonal frequency division multiplexing (OFDM). However, channel estimation (CE) is a big challenge in FBMC because it suffers from intrinsic interference which is due to the orthogonality of the subcarrier functions in the real field only. In this paper, we investigate a proposed modified interference approximation scheme (M-IAM) by approximating the intrinsic interference from the neighbouring pilots to accommodate the complex channel frequency and thus improving CE performance besides simplifying its processing. The M-IAM scheme has a larger pseudo pilot magnitude than other conventional preamble schemes, namely the interference approximation method (IAM) with its versions (IAM-C) and (E-IAM-C); in addition to the novel preamble design (NPS). In addition, the proposed (M-IAM) scheme is characterized by the lower transmitted power needed. The CE performance of the M-IAM is investigated through 512 and 2048 subcarriers via different types of outdoor and indoor multipath fading channels that are time-invariant such as IEEE 802.22, IEEE 802.11, Rician, and additive white Gaussian noise (AWGN), as well as time-varying channels such as Rayleigh and Vehicular A (Veh-A). Simulation results demonstrate that the proposed M-IAM scheme achieves a lower bit error rate (BER), lower normalized mean square error (NMSE) and lower peak-to-average power ratio (PAPR) over the conventional preamble schemes under the aforementioned channel models. The proposed scheme has the advantage of saving the transmitted power, a requirement that could match 5G low power requirements. KEYWORDS Filter bank multicarrier (FBMC), intrinsic interference, preamble based channel estimation methods

OFDM (Orthogonal Frequency Division Multiplexing) has been raised a new modulation technique. Due to its advantages in multipath fading channel e.g. robust against ISI, ICI and some other advantages like best QoS for multiple users, efficient usage of bandwidth it is suggested to be the modulation technique for next generation 4G networks e.g. LTE. But along with all its advantages there are some disadvantages also e.g. High PAPR (Peak to Average Power Ratio) at the transmitter end and BER (Bit Error Rate) at the receiving end. Since OFDM is only used in the downlink of 4G networks. To reduce the problems of OFDM some techniques e.g. SLM, PTS, Clipping, Coding, & Pre-coding etc are suggested but none of them is reduce the PAPR and BER to an acceptable value. This Paper will discuss some techniques of PAPR & BER reduction, and their advantages and disadvantages in detail.

- by shanmukha swamy
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- Henri Bergson, Bertrand Russell, OFDM, OFDMA
- by M. Aboul-dahab
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- Distributed Computing, MIMO-OFDM systems, Intrinsic motivation, OFDMA
- by Hamza Kiani
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- Wireless Communications, ISI, OFDM, OFDMA

This paper proposes an enhanced pilot-aided channel estimation algorithm for the second generation of the digital video broadcast for terrestrial (DVB-T2) standard. Two channel estimation techniques are discussed; the first is based on the 3-points averaging technique, while the second is based on studying the frequency domain pattern of the channel response. The second technique leads to a 0.5 dB reduction in the SNR needed to guarantee a specific bit error rate (BER) requirement when compared to the conventional estimation technique recommended by the DVB-T2 implementation guide lines.

In this paper, we study the orthogonal frequency division multiplexing (OFDM) system under imperfect channel-acquisition. We consider an OFDM system with a half-symbol-spaced receiver, where we employ a pilot symbol padding scheme for channel acquisition. Also, we use the Kronecker tensor product either at the transmitter to insert pilot symbols among data symbols or at the receiver to extract signals associated with pilots or data symbols. Also, we obtain the symbol detection with the minimal probability of error under imperfect channel acquisition. Results, both simulation and analytical, reveal that channel acquisition error degrades the system performance. However, the OFDM system with a half-symbol-spaced receiver shows better error probability and less acquisition error compared to the OFDM system with a symbol-spaced receiver.

Several factors drive the use of visible light communication systems as an alternative communication method besides RF communication, one of which is energy saving because the VLC system uses the same device for room lighting, i.e., LED. This study aims to model the VLC systems based on multi-carrier modulation (DCO-OFDM) by using MATLAB software. In this study, VLC the system is modeled on two parts, namely Digital Signal Processing (DSP) and optical channels. The DSP block consists of FFT, convolutional encoder, modulator-demodulator, interleaver-deinterleaver, and synchronizer. For error control coding (ECC), the Viterbi decoder algorithm is used. The results showed that DCO-OFDM frames had been successfully designed. Based on mathematical calculations through the MATLAB approach, the VLC system can work well in 5m x 5m x 3m rooms size: BER equals to zero for the minimum SNR of 10 dB has been obtained while the highest SNR value that can be achieved is ~ 30 dB.