The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this paper, we implement Bose-Chaudhuri-Hocquenghen (BCH) coding to study the performance of Power Line Channel (PLC) impaired by impulsive noise and AWGN. Quadrature amplitude modulation (QAM) is employed and orthogonal frequency division multiplexing (OFDM) is used as a transmission scheme. Block truncation coding (BTC) is used for the compression of the image. A comparison is made between uncoded...
Impulsive noise is one of the major challenges in power line communications and can cause serious problems in OFDM-based PLC systems. In this paper, we propose a combined Time-Domain/Frequency-domain technique for impulsive noise reduction in OFDM-based PLC systems. The performance of the proposed technique is studied against well known time-domain nonlinearities by means of computer simulations....
The clipping and filtering method is analyzed in terms of power savings. The analysis takes account of the gain in the amplifier efficiency due to peak-to-average-power-ratio (PAPR) reduction. Assuming a linear amplifier and a typical digital signal processor, the power savings is shown to be in the order of Watts.
A new scheme for iterative clipping and filtering (ICF) method is proposed for PAPR (peak-to-average power ratio) reduction of OFDM (orthogonal frequency division multiplexed) signals. The proposed one-iteration-clipping-filtering (OICF) scheme achieves target PAPR in one iteration, instead of K (>1) iterations as in conventional ICF method. An empirical expression is derived to scale original...
Transmission of compressed image data over Gaussian wireless channel using OFDM scheme is addressed. A wavelet thresholding technique based on automatic image quality assessment of image, which was proved to be highly conformed with the human visual evaluation, is utilized to obtain an optimum trade-off between the compression ratio and image quality.
Sigma delta modulated systems have a number of very appealing properties, and are therefore heavily used in analog to digital converters, amplifiers and as modulators in communication systems. This paper presents new results which show that they may also be useful for general purpose arithmetic computing. The paper introduces ternary (i.e. +1, 0 or -1) sigma delta modulated adders and integrators...
Sigma-delta modulators are inherently non-linear structures and suffer from many intriguing and unresolved problems. Two approaches are utilized to analyze these structures: analytical and nonlinear approximation techniques. According to the nonlinear approximation analysis, a circle map is proposed to model the dynamics of a third-order sigma-delta modulator and can be extended to include higher-order...
The study investigated the dependance of absorbed mobile phone radiation in terms of specific absorption rate (SAR) values on head size. A dipole and a generic phone model were used to simulate mobile phone at 900/835 MHz, and standard SAM phantom as an adult head model. Three child head models were derived after uniformly scaling down standard head in all directions by 90%, 80% and 70%. A numerical...
In this work we present a comparative study for the transmission of a wavelet-compressed still image using FFT-OFDM over multipath channels with additive white Gaussian noise (AWGN). Rather than using a global threshold for the compression of the wavelet coefficients, we chose to compress the data by transmitting only the low-pass subbands from each decomposition level. 16-QAM is considered for the...
A digital Class-D amplifier based on single-bit processing to be implemented on a field programmable gate array (FPGA) is presented. The main focus of this design is the reduction of noise, a drawback of Class-D amplifiers, by exploring the noise-shaping characteristics of sigma-delta modulation (SDM). The audio signal is retained in the digital single-bit domain until the final stage of the amplifier,...
The distinctive advantage of short-word-length systems (single-bit, two-bit, or ternary), namely, the hardware implementation simplicity, has not been put into effect due to its unresolved LMS adaptivity problem. The conventional LMS family of adaptive algorithms fail to converge if translated to the short-word-length domain. In this paper we propose a 2-bit-domain LMS adaptive filtering structure...
The stability of a high-order sigma-delta modulator has been addressed under dc input. A new approach for stability analysis is proposed. A nonlinear circle map is suggested to model the dynamics of the modulator. The stability problem is handled using an analogy between the dynamics of the sigma-delta modulator and the sinusoidal digital phase-locked loop (DPLL). An approximate fixed point solution...
The limit cycle behavior of a ternary filtering structure is investigated. It is found that the limit cycles behavior is dependent on the initial conditions of quantization error and the gain parameter in addition to the level of the DC input. The system is simulated and a random search procedure is set up to explore and extract its cyclical patterns
In this paper, a single-bit DC-blocker is presented. It is comprised of a ternary filtering stage preceded by a sigma-delta modulator. Different techniques are used to generate the ternary taps for hardware and performance optimization. Both the input and the output of this DC-blocker are assumed in single-bit format. The proposed DC-blocker can easily be implemented with FPGA.
A design technique for a single-bit digital comb filter is presented. The proposed filter response and performance are assessed in terms of signal-to-quantization-noise ratio (SQNR) and stability. It is found that the comb filter possesses a distinct frequency response in broadband signal applications. The same technique is utilized to design and simulate a single-bit N-period digital resonator. Feedback...
The unresolved problem of finding an adaptive LMS structure for ternary filters has substantially limited their useability despite their major advantage of hardware simplicity. In this paper we tackle this challenging problem by introducing an algorithm that seems to be quite promising. Results were surprising as it appeared that the proposed ternary algorithm is comparable in performance to the multi-bit...
Two structures for single-bit digital comb filtering are proposed. The first structure is based on ternary filtering, however, the output of the filter is in single-bit format. The second structure is based on second-order sigma-delta modulation (SigmaDeltaM). Both filtering structures contain no multi-bit multiplication, making the comb filter efficient for implementation. This filter can be utilized...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.