Orthogonal Frequency Division

The image transmission over wireless channel is already explored by many researchers. Due to eye perception for only low frequency component the de-noising technique may be add at receiver end of the wireless device. In this paper WiMAX system are used for image transmission and fuzzy de-noising method is used for improving the performance. PSNR and RMSE are taken as two parameters for comparing the performance. The MIMO technique is also used here with the 2 x 1 antenna system for BER performance improvement. A clear improvement using denoising technique is found and described in this paper.

The image transmission over wireless channel is already explored by many researchers. Due to eye perception for only low frequency component the de-noising technique may be add at receiver end of the wireless device. In this paper WiMAX system are used for image transmission and fuzzy de-noising method is used for improving the performance. PSNR and RMSE are taken as two parameters for comparing the performance. The MIMO technique is also used here with the 2 x 1 antenna system for BER performance improvement. A clear improvement using denoising technique is found and described in this paper.

Wireless communication technology has been growing remarkably well day by day. Wi-Fi has led wireless communication to a long way due to its high data rate capacity. Wi-Fi has a high penetration in market but it is connected to Internet or other networks with wired connections making its deployment complex and expensive. WiMAX, on the other hand, is new emerging wireless technology which provides wider coverage area but its deployment is also expensive. To overcome the individual shortcomings and using the capabilities of Wi-Fi and WiMAX, we have proposed an Integrated Wi-Fi/WiMAX network with mesh capabilities to form wireless mesh network. In this paper we are using mesh topology at Wi-Fi/WiMAX Routers (WWRs) so that WiMAX SS, inbuilt in WWRs, can communicate directly with each other without the intervention of WiMAX Base Station. The transmission is carried under influence of AWGN channel and propagation path loss. Wi-Fi/WiMAX mesh network is simulated and its performance is evaluated by Bit Error Rate with respect to Signal to Noise ratio and distance between WiMAX SS for different modulation schemes and distances between Wi-Fi AP and stations.

Orthogonal frequency division multiplexing (OFDM) systems, is one of the future of high rate wireless communications, exhibit great sensitivity to the effects of phase noise and the time-varying propagation channel, which can introduce inter-channel interference (ICI) due to the loss of orthogonality among subcarriers and common phase error (CPE) which causes the rotation of constellation. The presence of phase noise can reduce the signal to noise ratio (SNR) at the receiver, and hence reduce the bit error rate (BER) and data rate. There are various methods of phase noise mitigation already proposed in the literature but are of high complexity. In this paper a computationally efficient technique has been proposed, both by theory and computer simulations of the proposed scheme are shown which can effectively mitigate the effect caused by phase noise and improve the BER of OFDM systems. KEYWORDS: Common phase error (CPE), inter-carrier interference (ICI), orthogonal frequency division...

In Orthogonal Frequency Division Multiplexing Communication systems, the local oscillator used for the upconversion and down-conversion at the transmitter and receiver respectively introduces phase noise which causes two effects, common phase error (CPE) and inter-carrier interference (ICI). OFDM is one of the futures of wireless communications system, but exhibit great sensitivity to the phase noise and the time-varying propagation channel, inter-channel interference (ICI) result to the loss of orthogonality among subcarriers and common phase error (CPE) causes the rotation of constellation of the OFDM signal. Due to the presence of phase noise, produced by the local oscillator at the transmitter and receiver result in reduction of signal to noise ratio (SNR), and hence reduce the bit error rate (BER) and data rate. There are various methods of high complexity of phase noise mitigation already proposed in the literature. In this paper simple technique has been proposed. The compute...

Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation scheme which has been adopted in many wireless communication standards. Conventional OFDM uses Inverse Fourier Transform (IFFT) in the transmitter side and Fast Fourier Transform (FFT) in the receiver side. One of the drawback of FFT OFDM is the performance degradation in the presence of Carrier Frequency Offset (CFO). Many research works proven that replacing the Fast Fourier Transform (FFT) by Discrete Wavelet Transform (DWT) shows better performance. IFFT is replaced by Inverse Discrete Wavelet Transform (IDWT) and FFT is replaced by DWT (Discrete Wavelet Transform) in the conventional OFDM.DPSK modulation scheme is used in this work. In this paper both FFT OFDM and DWT OFDM are compared in the presence of Carrier Frequency Offset (CFO) in Additive White Gaussian Noise (AWGN) channel. Bit Error Rate (BER)of both FFT OFDM and DWT OFDM is compared in the presence of CFO. The result shows that DWT OFDM ou...

This paper deals with the comparative performance analysis of transmission technique (SISO AND MIMO) and shows the effect on transmission of image. We used four techniques for this category; SISO with Canny edge detection, MIMO with Canny edge detection, SISO without Canny edge detection and MIMO without canny edge detection. The results for each technique are compared with one another so as to choose the best result. These techniques applied on one image for calculating the parameters such as PSNR, MAE, and RMSE. In this paper an attempt is made to study the performance of most commonly used transmission techniques for image transmission and also the comparison on basis of these techniques is carried out by using MATLAB software.

A coding/decoding setup for a spectral phase encoding optical code-division multiple access (SPE-OCDMA) system has been developed. The proposal is based on the temporal self-imaging effect and the use of an easily tunable electrooptic phase modulator to achieve line-by-line coding of the transmitted signal, thus assuring compatibility with WDM techniques. Modulation of the code is performed at the same rate as the data, avoiding the use of high-bandwidth electro-optic modulators. As proof of concept of the technique, experimental results are presented for a back-to-back coder/decoder setup transmitting a 10 GHz unmodulated optical pulse train within an 80 GHz optical window and using 8-chip Hadamard codes.

Spectrum decision is an important and crucial task for the secondary user to avail the unlicensed spectrum for transmission. Managing the spectrum is an efficient one for spectrum sensing. Determining the primary user presence in the spectrum is an essential work for using the licensed spectrum of primary user. The information which lacks in managing the spectrum are the information about the primary user presence, accuracy in determining the existence of user in the spectrum, the cost for computation and difficult in finding the user in low signal-to noise ratio (SNR) values. The proposed system overcomes the above limitations. In the proposed system, the various techniques of machine learning like decision tree, support vector machines, naive bayes, ensemble based trees, nearest neighbour’s and logistic regression are used for testing the algorithm. As a first step, the spectrum sensing is done in two stages with Orthogonal Frequency Division Multiplexing and Energy Detection algo...

Orthogonal frequency division multiplexing (OFDM) systems, is one of the future of high rate wireless communications, exhibit great sensitivity to the effects of phase noise and the time-varying propagation channel, which can introduce inter-channel interference (ICI) due to the loss of orthogonality among subcarriers and common phase error (CPE) which causes the rotation of constellation. The presence of phase noise can reduce the signal to noise ratio (SNR) at the receiver, and hence reduce the bit error rate (BER) and data rate. There are various methods of phase noise mitigation already proposed in the literature but are of high complexity. In this paper a computationally efficient technique has been proposed, both by theory and computer simulations of the proposed scheme are shown which can effectively mitigate the effect caused by phase noise and improve the BER of OFDM systems. KEYWORDS: Common phase error (CPE), inter-carrier interference (ICI), orthogonal frequency division...

In Orthogonal Frequency Division Multiplexing Communication systems, the local oscillator used for the upconversion and down-conversion at the transmitter and receiver respectively introduces phase noise which causes two effects, common phase error (CPE) and inter-carrier interference (ICI). OFDM is one of the futures of wireless communications system, but exhibit great sensitivity to the phase noise and the time-varying propagation channel, inter-channel interference (ICI) result to the loss of orthogonality among subcarriers and common phase error (CPE) causes the rotation of constellation of the OFDM signal. Due to the presence of phase noise, produced by the local oscillator at the transmitter and receiver result in reduction of signal to noise ratio (SNR), and hence reduce the bit error rate (BER) and data rate. There are various methods of high complexity of phase noise mitigation already proposed in the literature. In this paper simple technique has been proposed. The compute...

Orthogonal frequency division multiplexing (OFDM) has been considered as a promising technique to achieve high data rate transmission in mobile environment. However, they are very sensitive to nonlinear effects due to high peak to average power ratio (PAPR). This paper proposes an efficient technique for reducing the PAPR of OFDM signals. The reduction in PAPR of the OFDM signal is obtained through Zadoff-Chu matrix transform (ZCMT) precoding based partial transmit sequence (PTS).The obtained results show that this precoding scheme is an attractive solution of the PAPR problem of OFDM signals.

Spectrum decision is an important and crucial task for the secondary user to avail the unlicensed spectrum for transmission. Managing the spectrum is an efficient one for spectrum sensing. Determining the primary user presence in the spectrum is an essential work for using the licensed spectrum of primary user. The information which lacks in managing the spectrum are the information about the primary user presence, accuracy in determining the existence of user in the spectrum, the cost for computation and difficult in finding the user in low signal-to noise ratio (SNR) values. The proposed system overcomes the above limitations. In the proposed system, the various techniques of machine learning like decision tree, support vector machines, naive bayes, ensemble based trees, nearest neighbour's and logistic regression are used for testing the algorithm. As a first step, the spectrum sensing is done in two stages with orthogonal frequency division multiplexing and energy detection algorithm at the various values of SNR. The results generated from the above algorithm is used for database generation. Next, the different machine learning techniques are trained and compared for the results produced by different algorithms with the characteristics like speed, time taken for training and accuracy in prediction. The accuracy and finding the presence of the user in the spectrum at low SNR values are achieved by all the algorithms. The computation cost of the algorithm differs from each other. Among the tested techniques, k-nearest neighbour (KNN) algorithm produces the better performance in a minimized time.

High peak-to-average power ratio (PAPR) is one of the major drawbacks in the orthogonal frequency division multiple access (OFDMA) systems. In this paper, we present a zadoff-chu matrix transform (ZCMT) precoding based localized OFDMA uplink system with improved PAPR. The proposed system is based on precoding the constellation symbols with ZCMT precoder. Extensive computer simulations have been performed to analyze the PAPR of the proposed system with the root-raised-cosine (RRC) pulse shaping. Simulation results show that, the proposed system has better PAPR gain than the hadamard-transform (WHT) precoded Localized-OFDMA uplink systems and the conventional Localized-OFDMA uplink systems.