Low Complexity Time Domain Interleaved Partitioning Partial Transmit Sequence Scheme for Peak-to-Average Power Ratio Reduction of Orthogonal Frequency Division Multiplexing Systems

As an attractive technique for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems, time domain interleaved partitioning partial transmit sequence (TD-IP-PTS) scheme uses circular convolution property of discrete Fourier transforms (DFT) so as to need only one inverse fast Fourier transform (IFFT) operation. However, the search and combination of phase factors still need higher computational complexity. In order to improve the problem, this paper detailedly analyzes the independence of phase factor vectors and optimizes the phase factor vectors in TD-IP-PTS. Furthermore, we find the characteristic of combination of phase factors and propose three methods respectively based on storage-unit, pipeline and select-path to implement the combination of phase factors in TD-IP-PTS. The simulation results show that TD-IP-PTS using independent and effective phase factor vectors has better PAPR performance and lower complexity than traditional IP-PTS. Moreover, among three proposed methods for combination of phase factors, the method based on select-path requires the least registers and delay time. This method is the most promising in practical applications.     

FPGA Architecture for 2D Discrete Fourier Transform Based on 2D Decomposition for Large-sized Data

Applications based on Discrete Fourier Transforms (DFT) are extensively used in several areas of signal and digital image processing. Of particular interest is the two-dimensional (2D) DFT which is more computation- and bandwidth-intensive than the one-dimensional (1D) DFT. Traditionally, a 2D DFT is computed using Row-Column (RC) decomposition, where 1D DFTs are computed along the rows followed by 1D DFTs along the columns. Both application specific and reconfigurable hardware have utilized this scheme for high-performance implementations of 2D DFT. However, architectures based on RC decomposition are not efficient for large input size data due to memory bandwidth constraints. In this paper, we propose an efficient architecture to implement 2D DFT for large-sized input data based on a novel 2D decomposition algorithm. This architecture achieves very high throughput by exploiting the inherent parallelism due to the algorithm decomposition and by utilizing the row-wise burst access pattern of the external memory. A high throughput memory interface has been designed to enable maximum utilization of the memory bandwidth. In addition, an automatic system generator is provided for mapping this architecture onto a reconfigurable platform of Xilinx Virtex-5 devices. For a 2K ×2K input size, the proposed architecture is 1.96 times faster than RC decomposition based implementation under the same memory constraints, and also outperforms other existing implementations.     

Integrated Dual-Display-Based 3G Mobile Phone / Wireless Terminal

In this paper, we describe HW and SW features of the developed prototype of a hybrid 3G mobile phone and wireless terminal, which provides integral video projection onto two VGA/2 displays that, when put side-by-side, form the integrated display with the ratio of the overall width to its overall height, equal to 4:3, so providing the integral video VGA format and enabling visual presentation of standard full-size web pages, PC mainstream SW screens (such as e.g. the ones of e-mail clients), multi-media content etc. When not in use, the displays can be fold back one onto each other, so preserving the industry-standard dimensions of the device. The two displays that share the image provide it with overall resolution of 640 x 480 pixels per inch. The device is driven by Texas Instruments OMAP 2420 multimedia processor with ARM1136 core and Linux operating system. In addition, the device is equipped with specially developped prototypes of unique spring/microgenerator-based battery charger as well as with ultra-thin mountable foil-based QWERTY keyboard.     

Performance of Efficient Signal Detection for LED-ID Systems

In this paper, effects of reader-to-reader interference are investigated for LED identification (LED-ID) system in a multi-reader environment. The LED-ID readers typically use different channels to avoid collision between readers. However, in-channel collision usually happens in terms of interrogation range. A reader-to-reader interference scenario is proposed, and nominal interrogation range of a desired reader is derived from this model. In order to evaluate the LED-ID reader-to-reader interference quantitatively, an efficient detection scheme is proposed and simulated by employing spreading sequence. The spreading sequence is inserted between each user’s frame formats. In the receiver, the desired signal is detected by using correlation among inserted spreading sequences. From simulation results, it is confirmed that the proposed scheme is very effective to enhance reliability of LED-ID communication systems.     

A blind audio steganalysis based on feature fusion

In this paper, we present a blind steganalysis based on feature fusion. Features based on Short Time Fourier Transform (STFT), which consists of second-order derivative spectrum features of audio and Mel-frequency cepstrum coefficients, audio quality metrics and features on linear prediction residue are extracted separately. Then feature fusion is conducted. The performance of the proposed steganalysis is evaluated against 4 steganographic schemes: Direct Sequence Spread Spectrum (DSSS), Quantization Index Modulation (QIM), ECHO embedding (ECHO), and Least Significant Bit embedding (LSB). Experiment results show that the classifying performance of the proposed detector is much superior to the previous work. Even more exciting is that the proposed methodology could detect the four steganography, with 85%+ classification accuracy achieved in all the detections, which makes the proposed steganalysis methodology capable of being regarded as a blind steganalysis, and especially useful when the steganalyzer are without the knowledge of the steganographic scheme employed in data embedding.     

Fast computation of wideband RCS using characteristic basis function method and asymptotic waveform evaluation technique

The Asymptotic Waveform Evaluation (AWE) technique is an extrapolation method that provides a reduced-order model of linear system and has already been successfully used to analyze wideband electromagnetic scattering problems. As the number of unknowns increases, the size of Method Of Moments (MOM) impedance matrix grows very rapidly, so it is a prohibitive task for the computation of wideband Radar Cross Section (RCS) from electrically large object or multi-objects using the traditional AWE technique that needs to solve directly matrix inversion. In this paper, an AWE technique based on the Characteristic Basis Function (CBF) method, which can reduce the matrix size to a manageable size for direct matrix inversion, is proposed to analyze electromagnetic scattering from multi-objects over a given frequency band. Numerical examples are presented to illustrate the computational accuracy and efficiency of the proposed method.     

Impairment-aware ordered scheduling in dual-header optical burst switched networks

Optical burst switching (OBS) is a promising technology for bridging the gap between optical wavelength switching and optical packet switching. Optical signal transmission quality is subject to various types of physical impairment introduced by optical fibers, switching elements, or other network components. The signal degradation due to physical impairment may be significant enough such that the bit-error rate of received signals is unacceptably high at the destination, rendering the signal to not usable. In this article, based on earlier study, we study the burst-scheduling problem in OBS networks using two control packets for each data burst, taking into account physical impairment effects. We propose a burst-scheduling algorithm that accommodates incoming bursts by primary path routing, deflection routing, and burst scheduling. We design an admission control mechanism to use network resources efficiently. At an OBS node, the proposed algorithm schedules bursts for transmission by searching for available resources as well as verifying signal quality. Our simulation results demonstrate that the proposed algorithm is effective in terms of reducing the burst-blocking probability.     

Systematic design of wideband ΔΣ modulators for WiFi/WiMAX receivers

Modern multi-standard receivers in deep-submicron technologies pose significant design challenges on the analog baseband. Moving this analog filtering to the digital domain simplifies the design, yielding a process-scalable implementation. However, analog-to-digital converter (ADC) specifications now become more stringent and must be obtained by comprehending the standard and the system. Assuming a receiver NF of 5.96 dB and SNR degradation of 0.36 dB by the ADC, the proposed dual-mode WiFi/WiMAX receiver attains an input sensitivity of −74 dBm (20 MHz channel bandwidth). To accommodate the high dynamic range and the anti-alias rejection needed for the system, a Delta-Sigma (ΔΣ) ADC is proposed. Single-loop and Multi-Stage Noise-Shaping (MASH) architectures that achieve a SNR of 69 dB at a low oversampling ratio (OSR) of 8 for a conversion bandwidth of 40 MHz (108 Mbps, OFDM) are investigated at system level. Based on thermal noise, harmonic distortion, and power tradeoffs, a ΔΣ ADC design that meets the design specifications is presented.     

Propagation delay influence in IEEE 802.11 outdoor networks

Originally, Wireless Local Area Networks served only small indoor areas. Nevertheless, the idea of employing IEEE 802.11 networks in large outdoor environments is a very attractive possibility. IEEE 802.11 technology offers several advantages: the low cost of equipment, its operation in the unlicensed spectrum and its higher data rates. Since the advent of the first IEEE 802.11 standard, a great deal of research has been carried out. So-called Wifi-based Long Distance networks are currently being deployed. In this paper, we study the suitability of employing IEEE 802.11 networks in large outdoor environments without modifying the standard working procedure. In such scenarios, IEEE 802.11 networks should offer coverage ranges of several kilometer, which leads to high propagation delay values. Thus, we analyze the influence of increasing propagation delay in the IEEE 802.11 MAC protocol. To carry out our analysis we present a mathematical model and simulation results. We provide an operating range in which IEEE 802.11 performance is feasible and establish a throughput threshold according to the propagation delay.