Kabushiki Kaisha Toshiba

Hidetaka Yoshikawa

Masami Akamine

Atsushi Nakagawa

Kimio Miseki

Kiyotaka Tsuji

Muneyuki Suzuki

Yutaka Seki

ATM transmission equipment provided between existing exchange or terminals of carrier equipment that, for example, can emulate existing transmission paths, and also implement T point interfaces for an in-home unit. The ATM transmission equipment detects communication anomalies or extracts maintenance/operation information from data strings on STM lines, such as high-speed digital lines or ISDN lines, and replaces only the necessary information resulting from those extractions or detections with alarm signals. The alarm signals are then transmitted together with information channels to the ATM network via a cell assembler/dissembler. The information channels and alarm information that arrive from the ATM network are rearranged into STM line data strings and output to LT units, DSUs, or terminals.

ATM transmission equipment

A variable rate coder/decoder system in which a quantizer, under control of a quantization controller, quantizes a signal obtained by subjecting discrete cosine transformation of a difference signal between an input signal and a signal from a frame memory storing therein a previous frame with a first quantization step width calculated based on a power value of the input signal calculated by a power calculator and a predetermined first signal-to-quantization noise ratio. In the system, further, a re-quantizer quantizes a difference signal between a signal being not quantized by the quantizer and a signal after the inverse quantization of an inverse quantizer with a second quantization step width calculated based on the power value controlled by a re-quantization controller and a predetermined second signal-to-quantization noise ratio. Variable length encoders subject the quantization output signals of the quantizer and re-quantizer to variable length encoding, decrease discard priority for the quantization output signal of the quantizer, increase discard priority for the quantization output signal of the re-quantizer, and then transmit them in the form of fixed-length cells or variable-length packets whereby, even when the amount of input data varies, its quality can be maintained constant and encoding and decoding can be realized with a high efficiency.

Variable rate coder/decoder system

As an encoded signal for transmission to a packet communication network or an ATM communication network, signals of a plurality of frequency subbands are independently encoded in units of frames, and an encoded bit rate is controlled in that frame unit. The deterioration of quality due to cell discarding is light, and an improvement in encoding efficiency can be expected through the joint use of entropy coding processing.

Transmitter and receiver employing variable rate encoding method for use

A packet communication system or ATM communication system in which a sequence of signals such as speech signals is divided into a plurality of band areas and the power of each band area is determined. Based on the power of each band area, coding signals are allocated for each band, frame by frame. At a receiving side, the signal to noise ratio SNR of the decoded signal is predicted by changing the total number of encoding bits for each band area based on the power of each band area signal. The bit rate is controlled so as to make the SNR constant. The bit rate is changed in accordance with a Fourier transform of the input signal.

Variable bit rate coding system

In a transmitter in the present invention, an input signal is input to a QMF bank 102 where the input signal is divided to a plurality of frequency bands to form corresponding band signals. A distributed bit calculating unit 109 calculates respective bit rates with which the corresponding band signals are encoded on the respective power values of the band signals. Quantizers 104-1, 104-2, . . . , 104-n encode the respective band signals at the corresponding bit rates and input the resulting corresponding band codes to a multiplexer unit 111 which incorporates the respective band codes into a cell as an information unit and sends the cell. In a receiver, a cell is decomposed to obtain the respective band codes, which are then dequantized to form the corresponding band signals. These band signals are synthesized to form a signal for the entire band, and the signal for the entire band is output as a decoded signal.

Growing community of inventors

Hino, Japan

Hidetaka Yoshikawa