NTT DoCoMo

About: NTT DoCoMo is a based out in . It is known for research contribution in the topics: Base station & Mobile station. The organization has 4032 authors who have published 8655 publications receiving 160533 citations.

Suppression of sidelobes in OFDM systems by multiple‐choice sequences

Abstract: In this paper, we consider the problem of out-of-band radiation in orthogonal frequency-division multiplexing (OFDM) systems caused by high sidelobes of the OFDM transmission signal. Suppression of high sidelobes in OFDM systems enables higher spectral efficiency and/or co-existence with legacy systems in the case of OFDM spectrum sharing systems. To reduce sidelobes, we propose a method termed multiple-choice sequences (MCS). It is based on the idea that transforming the original transmit sequence into a set of sequences and choosing that sequence out of the set with the lowest power in the sidelobes allows to reduce the out-of-band radiation. We describe the general principle of MCS and out of it we derive and compare several practical MCS algorithms. In addition, we shortly consider the combination of MCS sidelobe suppression method with existing sidelobe suppression methods. Numerical results show that with MCS approach OFDM sidelobes can be reduced significantly while requiring only a small amount of signalling information to be sent from transmitter to receiver. For example, in an OFDM overlay scenario sidelobes power is reduced by around 10 dB with a signalling overhead of only 14%. Copyright © 2006 AEIT.

Inter Frame Coding with Template Matching Averaging

Abstract: A template matching prediction based on a group of reconstructed pixels surrounding a target block enables prediction of pixels in the target block without motion information. The predictor of a target block is produced by minimizing the matching error of the template. Due to the freedom possessed by the template, the residuals of a target block may become large in flat regions. Our previous paper proposed to predictively encode the decimated version of a target block in flat regions to suppress the prediction errors. In this paper, the performance of template matching prediction is further improved. Multiple candidates are created by template matching at decoder. An average of the multiple candidates then forms the final predictor, which can reduce coding noise residing in the reference frames. Simulation results show that the proposed scheme improves coding efficiency of H.264 up to 7.9%.

Device authentication in a service control system

Abstract: A device authentication apparatus (30), including: a device identification information acquisition unit (31) configured to acquire identification information specific to a device; a connection protection unit (34) configured to protect a connection with the device; and an identifier generation unit (33) configured to combine all or some of the device-specific identification information, a device identification information type representing a type of the device-specific identification information, and a protection method type representing a type of a protection method used by the connection protection unit (34) to generate an identifier for a pair of the connected device and a connection environment.

Domain-specific Web search with keyword spices

Abstract: Domain-specific Web search engines are effective tools for reducing the difficulty experienced when acquiring information from the Web. Existing methods for building domain-specific Web search engines require human expertise or specific facilities. However, we can build a domain-specific search engine simply by adding domain-specific keywords, called "keyword spices," to the user's input query and forwarding it to a general-purpose Web search engine. Keyword spices can be effectively discovered from Web documents using machine learning technologies. The paper describes domain-specific Web search engines that use keyword spices for locating recipes, restaurants, and used cars.

Adaptive interpolation filter system for motion compensated predictive video coding

Abstract: An adaptive interpolation filter system for searching to obtain an optimized interpolation filter that minimizes prediction error in a video codec includes an interpolation module and a discrete search space. A plurality of discrete interpolation filters are positioned in a three dimensional grid within the search space. The interpolation module may select a current minimum filter. Based on the current minimum filter, a search region within the search space that includes a plurality of candidate filters located adjacent to the current minimum filter may be identified. The interpolation module may interpolate a reference image signal with each of the candidate filters. The candidate filter resulting in the smallest prediction error may be identified as the current minimum filter and the search repeated until the prediction error is minimized.