Modeling subjectively perceived annoyance of H.264/AVC video as a function of perceived artifact strength

This paper is concerned with the subjective perception of video coding artifacts in H.264/AVC encoded and decoded video. Our objective is to model the perceived annoyance of such low bit rate video sequences as a function of perceived artifact strength. We introduce a new method for determining this function and apply it to the data from two psychophysical experiments. Both experiments produced numerical judgments of the subjectively perceived annoyance of artifact combinations and the perceived strength of the respective coding artifacts. Our method produces a discrete multi-dimensional representation of the relationships in the data from which the function relating annoyance to artifact strength is derived. The method is applied to the data of the first experiment and the resulting function is shown to describe the data from the second experiment as well.     

Reduced-rank multistage receivers for DS-CDMA in frequency-selective fading channels

Multistage (MS) implementation of the minimum mean-square error (MMSE), minimum output energy (MOE), best linear unbiased estimation (BLUE), and maximum-likelihood (ML) filter banks (FBs) is developed based on the concept of the MS Wiener filtering (MSWF) introduced by Goldstein et al. These FBs are shown to share a common MS structure for interference suppression, modulo a distinctive scaling matrix at each filter's output. Based on this finding, a framework is proposed for joint channel estimation and multiuser detection (MUD) in frequency-selective fading channels. Adaptive reduced-rank equal gain combining (EGC) schemes for this family of FBs (MMSE, MOE, BLUE, and ML) are proposed for noncoherent blind MUD of direct-sequence code-division multiple-access systems, and contrasted with the maximal ratio combining counterparts that are also formed with the proposed common structure under the assumption of known channel-state information. The bit-error rate, steady-state output signal-to-interference plus noise ratio (SINR), and convergence of the output SINRs are investigated via computer simulation. Simulation results indicate that the output SINRs attain full-rank performance with much lower rank for a highly loaded system, and that the adaptive reduced-rank EGC BLUE/ML FBs outperform the EGC MMSE/MOE FBs, due to the unbiased nature of the implicit BLUE channel estimators employed in the EGC BLUE/ML schemes.     

Gesture Recognition: A Survey

Gesture recognition pertains to recognizing meaningful expressions of motion by a human, involving the hands, arms, face, head, and/or body. It is of utmost importance in designing an intelligent and efficient human-computer interface. The applications of gesture recognition are manifold, ranging from sign language through medical rehabilitation to virtual reality. In this paper, we provide a survey on gesture recognition with particular emphasis on hand gestures and facial expressions. Applications involving hidden Markov models, particle filtering and condensation, finite-state machines, optical flow, skin color, and connectionist models are discussed in detail. Existing challenges and future research possibilities are also highlighted     

MOVPE growth of HgCdTe for high performance 3–5 µm photodiodes operating at 100–180K

New results are reported on the growth of high performance medium wavelength infrared (3–5 μm) (MWIR) HgCdTe photodiodes in the three-layer P-n-N configuration. The detector structures were grown in situ by metalorganic vapor phase epitaxy (MOVPE) on (211)B oriented CdZnTe substrates. The mobilities of the single n-type layers with x-values of ∼0.30 are in the range of (3–4.5)×10⁴ cm²/V-s at 80K. The lifetimes on unpassivated films range from 1–5 and 4–10 μs at 80 and 180K, respectively, which are within a factor of two or less of the lifetimes calculated for Auger-1 and radiative recombination. The P-n-N films were processed into variable-area backside-illuminated diagnostic arrays and tested for quantum efficiency, spectral response, R_DA, I–V curves and 1/f noise in the 120–180K range. The internal one-dimensional quantum efficiencies are in the range of 85–100%. The optical collection lengths are typically ∼25 μm. I–V curves showed that diffusion current is the dominant junction current mechanism for temperatures ≥100K. R₀A values are at the one-dimensional limit for n-side diffusion currents over the 100–180K range. 1/f noise was measured to be very low at 120K and is the same as that measured in similarly processed arrays from recent LPE grown P-on-N heterojunctions. The results demonstrate that MOVPE growth can be used for large area, high performance MWIR HgCdTe detector arrays operating in the 120–180K temperature range.     

Characterization of CdS Nanowires Self-Assembled in a Nanoporous Alumina Template

CdS nanowires were self-assembled in a thin film (～200 nm) anodic aluminum oxide template on an indium tin oxide-coated glass substrate via dc electrodeposition. Raman spectral studies were done to probe the vibrational properties of scattering CdS phonons. Strong 1 longitudinal optical (LO), 2 LO, and 3 LO peaks were observed at 302 cm^?1, 603 cm^?1, and 906 cm^?1 having an energy separation of 37 meV, which is in accordance with the CdS bulk values. The photoluminescence spectra showed improved intensity of emission on annealing of the CdS nanowires. Field-emission scanning microscopy confirms the growth of nanowires of diameters ranging from 10 nm to 25 nm for these templates. These diameters agreed with those extracted from the luminescence emission energies.     

Quantized UWB Transmitted Reference Systems

Digital implementation of ultra-wideband receivers requires analog-to-digital conversion (ADC) at an extremely high speed, thereby limiting the available bit resolution. Herein, the effect of low bit resolution quantization on the performance of UWB transmitted reference receivers is investigated. It is verified that the gain of the automatic-gain-control (AGC) has a significant effect on the achievable performance. Because of the considerable performance loss of conventional transmitted reference receivers in the presence of a low resolution ADC a new family of receiver structures optimized and tailored to quantized observations is presented. In particular, the generalized- likelihood ratio test (GLRT) based on the quantized samples is derived and shown to provide modest performance gains relative to the infinite resolution GLRT rule employed on the quantized received signal suggesting that conventional receiver structures can also be employed in the presence of a low resolution ADC. Results reveal that four bits of resolution in combination with an optimal choice for the AGC gain are sufficient to closely approach the performance of an infinite resolution receiver.     

Secrecy Capacity Analysis of MIMO System over Multiple Destinations and Multiple Eavesdroppers

Wireless Personal Communications - In this paper we address physical layer security of multiple input multiple output (MIMO) communication system in presence of multiple destinations and passive...     

Photoluminescence and Raman Spectroscopy of Polycrystalline ZnO Nanofibers Deposited by Electrospinning

The technique of electrospinning offers the advantage of growing nanowires in bulk quantities in comparison with traditional methods. We report optical studies of polycrystalline zinc oxide (ZnO) nanofibers (∼100 nm thick and 5 μm long) deposited by electrospinning. Photoluminescence from the nanofibers shows a near-ultraviolet (near-UV) peak corresponding to near-band-edge emission and a strong broad peak in the visible region from oxygen antisite and interstitial defects. Temperature-dependent photoluminescence spectroscopy reveals that different carrier recombination mechanisms are dominant at low temperature. Our Raman spectroscopy results demonstrate that characterization of the quasimodes of longitudinal optical (LO) and transverse optical (TO) phonons present in an ensemble of polycrystalline nanofibers tilted at various angles in addition to the dominant E ₂(high) mode provides a promising technique for assessing the quality of such randomly oriented nanowires.     

Complexity reduction in subspace-based blind channel identificationfor DS/CDMA systems

Direct-sequence code-division multiple access is emerging as a potential multiple-access communication scheme for future digital wireless communications systems. Such wide-band systems usually operate in a frequency-selective fading channel that introduces intersymbol interference and thus potential performance degradation. Previously proposed subspace-based blind channel identification algorithms, which provide estimates of channel parameters for effective equalization, suffer from high numerical complexity for systems with large spreading gains. In this paper, it is shown that, through the use of matched filter outputs, reduction in numerical complexity can be obtained. The complexity reduction is considerable when the channel length is small and the system is moderately loaded. The results show that the new algorithm suffers a slight performance loss. Although the employed matched filter outputs do not form a set of sufficient statistics for the unknown channels, the difference between the matched filter outputs and the sufficient statistics becomes negligible for large observation lengths and the asymptotic normalized Fisher information does not change. Performance is evaluated through simulations, the derivation of a tight approximation of the mean-squared channel estimation error, and through comparisons to the Cramer-Rao bound for the estimation error variance. It is shown that the approximation of the mean-squared error can be obtained in terms of the correlation of the spreading codes and the channels. This representation of the error supplies a tool for investigating the relationship between performance and spreading sequence correlations     

Fast motion estimation for H.264

Several specific features have been incorporated into Motion estimation (ME) in H.264 coding standard to improve its coding efficiency. However, they result in very high computational load. In this paper, a fast ME algorithm is proposed to reduce the computational complexity. First, a mode discriminant method is used to free the encoder from checking the small block size modes in homogeneous regions. Second, a condensed hierarchical block matching method and a spatial neighbor searching scheme are employed to find the best full-pixel motion vector. Finally, direction-based selection rule is utilized to reduce the searching range in sub-pixel ME process. Experimental results on commonly used QCIF and CIF format test sequences have shown that the proposed algorithm achieves a reduction of 88% ME process time on average, while incurring only 0.033 dB loss in PSNR and 0.50% increment on the total bit rate compared with that of exhaustive ME process, which is a default approach adopted in the JM reference software.