KEYWORDS: Video, Multimedia, Communication engineering, Electrical engineering, Local area networks, Internet, Standards development, Astatine, Modulation, Digital image processing
Performance anomaly is a serious problem that would affect the throughput in multirate IEEE 802.11 wireless networks. Existing performance anomaly solutions improve the throughput by adjusting one or more MAC parameters. However, they do not consider the frame delay. Thus the frame delay of some stations would be increased due to the MAC parameter adjustments. The increase of frame delay would seriously affect the quality of service (QoS) of multimedia applications such as video communications. In this paper we classify the existing solutions based on the MAC parameters to adjust, and analyze the effect of each type of solution on the frame delay. Numerical results show that the effects on frame delay significantly differ between the various types of solutions. This provides a novel perspective to evaluate the existing performance anomaly solutions.
KEYWORDS: Received signal strength, Signal to noise ratio, Multimedia, Neural networks, Computer simulations, Modulation, Phase shift keying, Mobile devices, Neodymium, Video
Providing multimedia services in wireless networks is concerned about the performance of handoff algorithms because
of the irretrievable property of real-time data delivery. To lessen unnecessary handoffs and handoff latencies which can
cause media disruption perceived by users, we present in this paper a cross-layer handoff algorithm base on link quality.
Neural networks are used to learn the cross-layer correlation between the link quality estimator such as packet success
rate and the corresponding context metric indictors, e.g. the transmitting packet length, received signal strength, and
signal to noise ratio. Based on a pre-processed learning of link quality profile, our approach makes handoff decisions
intelligently and efficiently with the evaluations of link quality instead of the comparisons between relative signal
strength. The experiment and simulation results show that the proposed method outperforms RSS-based handoff
algorithms in a transmission scenario of VoIP applications.
This paper presents an optical auto-focusing system that is implemented by integrating a real-time auto-focusing algorithm, an image capturing and processing module and a stepper motor. Several image filters are tested and compared through the system for their effects on suppressing noise to accelerate the auto-focusing procedure. Besides, a nonlinear regression method is applied in the data analysis for the system to quickly move the stepper motor to the focus. The concise and effective algorithm can be applied on digital cameras for auto-focusing with noise reduction.
This paper describes a novel adaptive-hierarchical-filtering technique to achieve high-quality magazine image reproduction on computer peripherals such as color copier, or scanner plus printer. Commercial magazine images are halftoned images. Unacceptable noises and moire distortion may result when halftone images are copied (i.e., scanned and printed). In this paper, we analyze moire patterns formation characterized by the following factors: Moire patterns formation depends on the following factors: (1) halftone screen frequency, how many lines per inch (i.e., lpi) (2) scan frequency, how many dot per inch, (dpi) (3) screen angle which is the screen orientation against the scan direction, (4) scanner aperture (i.e., scanner characteristics), (5) halftoning and printing mechanisms, (6) viewing conditions. Error diffusion tends to randomize the moire patterns, and cluster-dot or line screen show more moire distortion. We developed a set of variable- length low-pass filters that have a nice inheritance of canceling aliased low frequency components (moire distortion). High pass filtering is also applied to sharpen image edges. A hierarchical filter classifier was developed to determine that an edge is either a global true edge (for sharpening enhancement) or a local halftone's micro-structural edge (for LPF for moire reduction). Depending on the classifier, adaptive LPF is applied to achieve the smooth transition between sharp edges and smooth halftone regions. Thus, we achieve overall high-quality output images. Experimental results have been shown the effectiveness of the presented technique that works well on wide combinations of above- mentioned 6 factors for high-quality magazine image reproduction.
The feasibility of using merocyanine 540 (MC 540) and Photofrin II (PII) as effective photodynamic therapeutic (PDT) agents for killing hepatoma cells and duck hepatitis B virus (DHBV) in vitro was investigated. Cultured duck hepatocytes infected with DHBV and hepatoma cells, Hep 3B and HCC 36, were used as models. MC 540 and PII effectively inhibits the DHBV growth by 90 - 99% in a dose- and light-dependent manner. Photodynamic killing of MC 540 in the two hepatoma cell lines results in 94 - 99% growth inhibition. However, both photosensitizers exhibit dark cytotoxicity (37 - 56%). The present results suggest that MC 540 and PII could be promising and effective photodynamic agents for killing HBV and hepatoma cells.
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