NEC

About: NEC is a company organization based out in Tokyo, Japan. It is known for research contribution in the topics: Signal & Layer (electronics). The organization has 33269 authors who have published 57670 publications receiving 835952 citations. The organization is also known as: NEC Corporation & NEC Electronics Corporation.

Location sensing system and method using packets asynchronously transmitted between wireless stations

Abstract: In a communication system, a location server is provided for receiving a location request. A plurality of base stations whose locations are predetermined are connected to the location server. In response to the location request, the system determines a round-trip propagation delay time of packets asynchronously transmitted over a wireless channel between each of the base stations and a target mobile station, calculates the distances from the round-trip propagation delay times, and estimates the location of the mobile station from an intersection of a plurality of circles whose radii are equal to the distances and whose centers respectively coincide with the locations of the base stations. The location server returns a location report to the requesting source for indicating the location of the mobile station.

One-dimensional logic gate assignment and interval graphs

Abstract: This paper gives a graph-theoretic approach to the design of one-dimensional logic gate arrays using MOS or I^{2}L units. The incidence relation between gates and nets is represented by a graph H=(V,E) , and a possible layout of gates and nets is characterized by an interval graph \hat{H} = (V, E \cup F) , where F is called an augmentation. It is shown that the number of tracks required for between-gate wiring is equal to the clique number (chromatic number) of H , and hence the optimum placement problem is converted to that of minimum clique number augmentation. This turns out to be an NP -complete problem. Instead a polynomial-time algorithm for finding a minimal augmentation is presented, where an augmentation is minimal if no proper subset of it is an augmentation. An algorithm for gate sequencing with respect to a given augmentation is also presented.

Transmission restricting device radio communication terminal equipment and transmission restricting system using these

Abstract: Disclosed is a transmission restricting system which has a transmission interruption controlling means for generating and radiating a magnetic field pattern including a command code to command the transmission interruption to a radio communication terminal equipment in a radio-wave transmission-prohibited area, the transmission interruption controlling means being disposed at the entrance or exit of the radio-wave transmission-prohibited area; a transmission interruption releasing means for generating and radiating a magnetic field pattern including a command code to command the releasing of transmission interruption to the radio communication terminal equipment in the radio-wave transmission-prohibited area, the transmission interruption releasing means being disposed at the entrance or exit of the radio-wave transmission-prohibited area; and a radio communication terminal equipment comprising means for detecting a magnetic field pattern including a command code to command the transmission interruption or the releasing of transmission interruption, and means for controlling the process of the transmission interruption or the releasing of transmission interruption according to the result of the detection of the detecting means.

Multi-channel echo canceler

Abstract: A multi-channel echo canceler for canceling echo generated as a result of propagation of 2-channel received signals, along a spatial acoustical path via a first and a second loudspeaker, from a transmitted signal containing a speech source signal received through a first and a second microphone and the echo. The echo canceler is capable of highly accurate delay time difference estimation and also of quick detection of the movement or change of the talker. Right after the movement or change of the talker, the filter coefficient set updating is stopped, or step size is updated. Deterioration of the echo cancellation performance does not occur that might otherwise result from delay of the detection of the movement or change of the talker or reduction of estimated delay time difference.