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.

Fault recovery system and transmission path autonomic switching system

Abstract: Setting of a bypass path upon occurrence of transmission failure, is applicable for large scale network. A system includes signaling means which makes judgment whether bypassing process is performed by an own node by a bypassing process judgement means when a release message issued upon occurrence of failure, is received. Upon judgment to perform bypassing process, computation of bypass path is requested by the path computing means. On the basis of result of computation, bypass path is established and switched. In the bypassing process judgment means, judgment is made whether bypassing process is performed by the signaling means or not depending upon the relationship of positions of the faulty portion and the own node.

Transmission power control system capable of keeping signal quality constant in mobile communication network

Abstract: In order to provide for a mobile communication network of a cellular type a transmission power control system capable of keeping a signal quality constant, an average bit error rate y is measured on a receiving side in connection with a communication channel being in use (step 100). If the average bit error rate y is not greater than a first rate threshold value LV1, transmission power is decreased by a predetermined amount on a transmitting side (step 102). If the average bit error rate y is not less than a second rate threshold value LV2 which is greater than the first rate threshold value LV1 (step 103), the transmission power is increased by the predetermined amount on the transmitting side (step 104). Preferably, an average reception level is additionally measured to adjust the transmission power when the bit error rate is less or greater than the first or the second rate threshold value. The first and/or the second rate threshold value is adaptively adjusted by counting the number of times by which the bit error rate exceeds a predetermined maximum allowable rate. It is possible to use an average carrier to interference ratio with threshold ratio values substituted for the threshold rate values and with a predetermined minimum allowable ratio used.

Semiconductor memory device

Abstract: PURPOSE:To prevent a memory cell in a normal part from the generation of characteristic deterioration due to the disorder of the regularity of a pattern by adding a spare cell array around a memory cell array in the normal part which is equal to the total memory capacity. CONSTITUTION:One of an X decoders 2 is selected through an input buffer in a peripheral circuit 5, one of Y decoders 4 is simultaneously selected and transistors (TRs) corresponding to the number of bits in one word in the Y selector 3 are conducted. At that time, memory cells corresponding to the number of bits in one word are selected in the memory cell array of the normal part. A deteriorated part is concentrated into the spare memory cell array 6 to reduce the influence upon the cell array 1. Thereby, the array 1 can be provided with uniform characteristics.

A robust adaptive beamformer for microphone arrays with a blocking matrix using constrained adaptive filters

Abstract: This paper proposes a new robust adaptive beamformer applicable to microphone arrays. The proposed beamformer is a generalized sidelobe canceller (GSC) with a variable blocking matrix using coefficient-constrained adaptive digital filters (CCADFs). The CCADFs minimize leakage of target signal into the interference path of the GSC. Each coefficient of the CCADFs is constrained to avoid mistracking. The input signal to all the CCADFs is the output of a fixed beamformer. In a multiple-input canceller, leaky ADFs are used to decrease undesirable target-signal cancellation. The proposed beamformer can allow large look-direction error with almost no degradation in interference-reduction performance and can be implemented with a small number of microphones. The maximum allowable look-direction error can be specified by the user. Simulation results show that the proposed beamformer designed to allow about 20 degrees of look-direction error can suppress interference by more than 17 dB.

Optimal design and evaluation of survivable WDM transport networks

Abstract: This paper proposes an optimal design scheme for survivable wavelength-division multiplexing (WDM) transport networks in which fast restoration can be achieved by using predetermined restoration paths that are independent of failure locations and which have one to one correspondence with working paths Integer programming-based design problems are formulated to optimally determine working and their corresponding restoration paths, the number of fibers in each span, and the number of optical cross connects (OXCs) in each node In these optimization problems, total facility cost, which includes not only transmission cost but also cross connection, is minimized This design scheme can handle the dedicated/shared allocation of spare resources and several parameters, such as the maximum available number of wavelengths per fiber /spl Omega/, the matrix size of each OXC, and cross-connection to transmission cost-coefficient ratio /spl gamma/ Total fiber length, the total number of OXCs, etc, are evaluated from obtained design results for these options and parameters Numerical examples show that the dependency of total fiber length and the total number of OXCs on /spl gamma/ is relatively small, and cross-connection to transmission cost ratios (/spl gamma/ times the total number of OXCs divided by total fiber length) in the dedicated and shared cases are almost the same for each combination of /spl gamma/ and /spl Omega/