During an OFDM transmission, a loss of sub-carrier orthogonality due to Doppler-spread of the channel leads to inter-carrier interference (ICI). This problem is especially bad in mobile reception environments. especially, under mobile reception environments. ICI causes significant degradation of the bit error rate characteristics and its influence becomes larger as the carrier frequency or velocity of the receiver increases. This paper proposes a method to reduce the ICI caused by the Doppler spread of the channel. The transmission channel is modeled by a combination of multiple Doppler shifted propagation paths, and their parameters such as attenuation, relative delay and Doppler-shift are estimated using scattered pilot symbols. The ICI is canceled by multiplying the inverse matrix of the estimated channel matrix with the received OFDM symbol vector. Computer simulation confirmed that the proposed method can reduce the bit error rate of a Doppler spread channel.
In the OFDM SFN system that re-broadcasts signals received from the main station to a the relay station, the area where the delay of the received signal is longer than the guard interval length increases. This is in contrast to the SFN system that broadcasts signals simultaneously at both the main station and the relay station. This generates inter-symbol and inter-carrier interference, degrading the bit error rate. We developed a technique that allows the SFN system to re-broadcast signals received from the main station after adding an appropriate delay. In this paper, a receiver using an array antenna and a maximum ratio combining technique for this SFN system is proposed. Theoretical analyses and computer simulation show that this technique improves the bit error rate more than do conventional methods.
In an OFDM transmission system, it is difficult to improve performance against frequency selective fading by using only an adaptive equalization because of the severe degradation of the SN ratio of specific carriers. In order to improve this, we propose an optimal data reconstruction from OFDM signal whose data symbols are spread in the frequency domain. In addition, we studied simplification of data spread OFDM with optimal data reconstruction. The bit error rate characteristics were examined by using computer simulations. Our results confirmed that the proposed method simplified data spread OFDM and equaled the performance of the conventional method. Moreover, we confirmed that combining it with large interleaver, rather than increasing carriers, improves the characteristics of the data spread OFDM under the Rayleigh frequency selective fading channel.
A circumstantial video image should convey sufficient information about the situation, while protecting the privacy of the specific person' s in the scene. This paper describes a concealment system which automatically identifies a person by using face recognition, tracks him or her, and displays his or her image in a modified form such as in silhouette with or without name, or displays only a name instead of the original video image. A method for comparing situational information obtained from the modified or raw circumstantial video image with one required in several applications is also described. A subjective evaluation was carried out in order to ascertain how people evaluate modified video images from the observer or subject viewpoint. As a result of an experiment in which the several applications were considered, the silhouette with name list type of concealment seems to be the most appropriate observer-subject compromise.
A special-purpose high-resolution printer has been constructed for fabricating computer-generated holograms. This printer is capable of drawing fringe patterns exceeding 104 dpi in resolution. The patterns are numerically synthesized and have a continuous gray level. The print time is less than an hour for holograms measuring 1 cm2. The mechanism and structure of the constructed printer and optically reconstructed images of holograms fabricated by using the printer are described.
There has been much research on production of realistic deformation animations based on physically based 3D model. If we apply a physically based model to a polygon geometry, a large number of calculations are needed if the complexity of the 3D model is high. We propose a method of calculating the deformation in which a physically based model and axes are applied to lattice meshes to generate a free form surface. This method reduces the calculation cost, and a deformation simulation considering the interior properties of the solid model can be easily realized with it.
The noise power spectra of radiographic film have been used to analyze the graininess of radiography. Furthermore, it has recently become clear that graininess analysis, especially at low space frequencies, is needed for quantitative evaluation of a radiographic screen/film system. This paper describes a method for analysis of film at low space frequencies that is based on the maximum entropy method (MEM). This method can determine the basic order of MEM to maximize the ratio of the order to the power spectrum at low space frequencies. Experimental results confirmed that the noise power to express the radiographic influence on films can be precisely measured at ultralow space frequencies.
A liquid crystal tunable filter was attached to a cooled CCD camera in order to create a hyper-spectral camera. Spectral images of slices of green- and red-flesh melons were captured at 5 nm intervals over a range of 800nm and 1, 000nm. Twenty-five mm-diameter cylindrical calibration samples were extracted from the above samples. Regression analyses over the spectral images and sugar content data of the calibration samples confirmed that there is a sugar absorption band around 910 nm. In addition, calibration curves between the 2nd derivative absorbance around the sugar absorption band and Brix sugar content were plotted. By applying these calibration curves to each pixel of the spectral images of sample slices, sugar distribution maps for the melons could be developed.
This paper discusses multi-view technology for a projection-type stereoscopic display. The multi-focal screen of this display employs the diffractive function of a Holographic Optical Element (HOE). For three dimensional (3D) displays to be viewable without special glasses, multi-view is very important, and this requirement is difficult to meet because the wide viewing area conflicts with the separation of viewing area between the right and left eyes. Holography is suitable for developing such an optical device. The display is a recursive multi-view stereoscopic display that uses multiple mirrored focal point HOEs. The advantage of this display is that it doesn't require mixing of stereoscopic images. The configuration is very simple because of the type of projection. The stereoscopic images from two cameras can be directly observed without editing them. The display lets more than one observer view the same 3D image at the same time.