Hitachi, Ltd.

Hitachi Denshi Kabushiki Kaisha

Masahiro Koya

Yasuhiro Kita

Narimichi Maeda

Nobuo Tsukamoto

Kohei Ishizuka

Yoshiro Kokuryo

Kazuhiko Takaoka

Yukio Nakano

Yasushi Takahashi

Akihiko Takase

Masahiro Takatori

Yoshitaka Takasaki

Hideya Suzuki

Arata Nakagoshi

Makoto Ohnishi

Yoshiaki Asakawa

Naoya Kobayashi

Yasushi Sawada

Yoshihiro Iwata

Yukiji Yamauchi

Yoshiaki Takemura

Noriyuki Sugiura

Yasuko Shinata

A radio communication system and a traffic channel assignment method for realizing the assignment of traffic channels capable of improving the efficiency of use of frequency in the case where the traffic density is high and improving a radio link quality in the case where the traffic density is low. A base station judges the traffic density from a carrier to interference power ratio (CIR) on each channel capable of being selected as a traffic channel. In the case where the traffic density is low, a traffic channel assignment mode selecting an available channel having a greater CIR is assigned as a traffic channel to a mobile station. In the case where the traffic density is high, a traffic channel assignment mode selecting an available channel having a smaller CIR is assigned as a traffic channel to the mobile station. Thereby, it is possible to structure a radio communication system which can cope with the condition of the traffic density of the neighborhood.

Traffic channel assignment based on traffic density and signal quality

There is provided a maximum likelihood decoding method, and an apparatus, capable of correcting burst errors caused by abrupt lowering of the signal amplitude. The soft decision maximum likelihood decoding method is a maximum likelihood decoding method for conducting maximum likelihood decoding on a received train resulting from addition of an error train to a transmission code train, which has been obtained by coding an information train by using convolutional codes on a transmission side. The soft decision maximum likelihood decoding method includes the step of making corrections by multiplying the soft decision likelihood metric having a multi-valued level, which has been obtained by soft decision likelihood metric from the received train, by weighting coefficients depending upon an instantaneous amplitude of the received signal, and the step of conducting maximum likelihood decoding by using corrected soft decision likelihood metric values. Thereby, it becomes possible to enhance the error correcting capability of error correcting apparatuses used in mobile radio communication or the like with severe fading. As a result, communication reliability is increased.

Soft decision maximum likelihood decoding method with adaptive metric

A communication network system includes a communication line, a plurality of communication stations each having a node coupled to the communication line and a network controller coupled to the stations for controlling routing for communication messages between nodes. In one embodiment, the messages are sent from plural terminals connected with each node along with communication performance prerequisites. The communication performance prerequisites for a communication message are discriminated in the node which receives the message. Traffic in various routes between the nodes is continually measured in the communication stations and the measuring results are stored in a database storage unit. Future traffic in the various routes is predicted on the basis of the information on the continually measured traffic by the use of a predetermined algorithm and stored in the storage unit for use in determination of routes for communication messages on the basis of the result of the communication performance prerequisites discrimination and predetermined criteria with respect to the updated information on the predicted traffic in the storage unit.

Communication network system and method of controlling a communication

In portable wireless communication systems wherein subscriber stations communicate with a plurality of base stations each covering a predetermined area, communication lines are provided for dedicating to the exchange of the use status and observation result of radio channels with the plurality of base stations in order that each base station can autonomically manage the determination of a base station with which a subscriber station communicates, the selection of a radio channel to be used, and the like.

Portable wireless communication systems

An adaptive digital filter is connected in parallel with a transmission system and includes a plurality of delay circuits, a nonrecursive digital filter having coefficient parameters of the delay circuits so as to approximate the characteristics of the transmission system, and a correction circuit for correcting the coefficient parameters of the nonrecursive digital filter. The adaptive digital filter further includes a first variable attenuator, a second variable attenuator and a comparator. The first variable attenuator receives an input signal for the adaptive digital filter, variably attenuates the input signal in response to a first control signal, and supplies an attenuated input signal to the transmission system and the nonrecursive digital filter. The second variable attenuator receives a difference between the output signals from the nonrecursive digital filter and the transmission system and variably attenuates the difference signal in response to a second control signal. The attenuated difference signal serves as an output of the adaptive digital filter. The comparator compares the level of the input signal with the level of the output signal from the transmission system and drives the first or second attenuator, which receives a lower level signal when the level difference exceeds a predetermined value.

Adaptive digital filter for eliminating howling

In a gain control circuit, an electric power calculating circuit is connected to a variable gain amplifier and a gain setting circuit for generating a gain control signal applied to the variable gain amplifier to control the gain thereof.

Electric power detecting circuit and gain control circuit using the same

An equalizer apparatus suitable for use in a MODEM for receiving a signal having passed through a number of carrier-band lines is disclosed in which the number of carrier-band lines is detected from a training signal, and electrical connection of a fixed equalizer to a variable equalizer is controlled on the basis of the number of carrier-band lines, in order to form a precise, simple automatic equalizer apparatus.

Automatic equalizer apparatus

A signal processing system detects the transmission characteristics of a channel thereby to compensate the output waveform of the channel into the most-optimum state. The impulse response of the channel is detected by transmitting a code having a keen autocorrelation from the transmission end and by determining the correlation between the received signal of the code transmitted and the same code of the aforementioned code at a reception end.

Signal processing system having impulse response detecting circuit

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Kodaira, Japan

Masahiro Koya