Nec Corporation

Nippon Telegraph and Telephone Corporation

Hitachi, Ltd.

Fujitsu Corporation

Youichi Sato

Naoaki Yamanaka

Motoo Nishihara

Takatoshi Kurano

Akihiko Takase

Akira Ito

Mitsuhiro Takano

Michio Kusayanagi

Kazuo Iguchi

Hiroshi Takeo

Joji Tajima

Toshiya Oouchi

Shigeo Shinada

Mitsuo Kaji

Miki Ito

In an input cell policing method in a network of an asynchronous transfer mode, according to information contained in a header field of each input cell, a group to which the cell belongs is identified. For each group, there are set a plurality of time frames having a predetermined length and mutually different phases to count the number of input cells in each time frame period. For each time frame, the count value of input cells is compared with a predetermined threshold value. An input cell for which the count value exceeds the threshold value in either one of the time frames is assumed to be an excess cell. The excess cell is discarded or a violation mark is added thereto.

ATM cell policing method and apparatus

An image data generating circuit of a color image processing apparatus generates multivalued image data for each color in accordance with density of each color of magenta (M), cyan (C) and yellow (Y). An M-screen threshold value generating circuit outputs a plurality of first threshold values, a C-screen threshold value generating circuit outputs a plurality of second threshold values, and a Y-screen threshold value generating circuit for outputting a plurality of third threshold values. A comparing circuit compares the multivalued image data outputted from the image data generating circuit with the first to third threshold values outputted from the M-, C- and Y- screen generating circuits for each color to output a comparison result in the form of a binary signal. The first and second threshold values is assigned to each pixel of an M multi-cell and a C multi-cell constituted by square matrixes having screen angles of .+-.tan.sup.-1 (q/p) and each side of .beta..multidot.p.multidot.q, respectively. For preventing coarse moire, p and q are any value of (11,3), (15,4) and (19,5), and the M multi-cell and the C multi-cell consist of N (=p.sup.2 +q.sup.2) sub-cells arrayed continuously in the directions of the screen angles of .+-.tan.sup.-1 (q/p) and having threshold values in accordance with the predetermined number of gradations. The third threshold value is assigned to a Y multi-cell constituted by a square matrix having a screen angle of 45 degrees and each side of .beta..multidot.p.multidot.q. The Y multi-cell consists of 2(p-q).sup.2 sub-cells arrayed continuously in the direction of the screen angle of 45 degrees. The first to fourth threshold values are repeatedly outputted in a cycle of .beta..multidot.p.multidot.q in synchronism with the multivalued image data of each color.

Color image processing apparatus capable of suppressing moire

In a policing arrangement for an ATM network, every incoming cell is stored in a cell buffer and a virtual path identifier (VPI) contained in the cell is extracted and translated to a corresponding one of a set of threshold values. Policing circuits of a matrix array are connected column by column for transferring a VPI in accordance with a read/write control circuit. Each policing circuit of the first column is uniquely responsive to a VPI of a particular value for storing the extracted VPI into a bridge memory, and this column has a greater number of policing circuits than any of the other columns of the array. In each column of the array, at least one of the policing circuits includes a cell counter for incrementing a cell count value in response to the VPI of every incoming cell and decrementing the cell count in response to a VPI read out of the bridge memory of the policing circuit. The cell count value is compared with the threshold value and a cell is discarded from the cell buffer when the cell count value exceeds the threshold value.

Policing circuits arranged in matrix array for selectively transferring

A usage parameter control circuit for effecting a policing control in an ATM transmission network, comprising a time interval measuring unit for measuring a time interval between a current arrival time of a cell to be judged, and an arrival time of a cell which arrived a reference threshold number of cells before the currently arriving cell arrives; and a judging unit for judging whether or not the measured time interval is shorter than a reference threshold time interval, whereby a longer accessing time is allowed and the circuit construction has a flexible expandability.

Usage parameter control circuit for effecting policing control in an ATM

A policing control apparatus having a cell input terminal receiving asynchronous transmission communication network cells; a policing circuit coupled to the input terminal for policing transmission of cells according to policing information; a cell output terminal from the policing circuit for outputting policed cells; a count memory in the policing circuit for storing a count value of the cells supplied to the policing circuit and for supplying the count value as the policing information; and a self-diagnosing circuit for monitoring problems and abnormalities of stored contents in the count memory and outputting an alarm upon detection of a problem or abnormality.

Policing control apparatus

Growing community of inventors

Kanagawa, Japan

Youichi Sato