Multipoint connected communication system having function of retraining modems provided therein and method of retraining the modems

Claim 2

A communication system in which a plurality of multipoint connected satellite stations are connected via a down line and an up line to a master station, the master station comprising a first MODEM unit for modulating user data and various control information to transmit the modulated data by means of different channels of the down line, and demodulating user data and various control information from modulation signals received in different channels of the up line and each of the satellite stations comprising a second MODEM unit for demodulating user data and various control information from modulation signals received in the different channels of the down line, and modulating user data and various control information to transmit the modulated data by means of the different channels of the up line, wherein each satellite station comprises an abnormality detecting means, operatively connected to the second MODEM unit, for controlling the second MODEM unit to request the master station to re-send a training signal when the abnormality detecting means detecting an abnormality from the quality of a signal received at the second MODEM unit, and the master station comprises a retraining command means, operatively connected to the first MODEM unit, for commanding the first MODEM unit to send the training signal when the first MODEM unit receives a signal indicating the request for re-sending of the training signal from any one of the satellite stations.

Claim 3

A communication system as set forth in claim 1, wherein said master station further comprises a storing means for storing past record information concerning abnormality detection in the satellite stations and information on executive time of the retraining, obtained through the first MODEM unit, whereby said returning command means refers to the storing means upon receipt of a new request for retraining and, based on the past record information on retraining, determines whether it should command the new retraining or not.

Claim 4

A communication system as set forth in claim 2, wherein said retraining command means comprises means for disregarding the request for retraining where another retraining is requested before the time required for a previous retraining elapses, or where the master station receives a plurality of requests for the retraining from an identical satellite station.

Claim 5

A communication system as set forth in claim 3, wherein said abnormality detecting means comprises a monitor for monitoring presence or absence of abnormality in the down line and a control means, responsive to an output signal indicating the presence of abnormality, for controlling the second MODEM unit to request the master station to re-send the training signal.

Claim 6

A communication system as set forth in claim 1, wherein said first MODEM unit comprises a first main modulation unit for transmitting user data at a relatively high speed by means of a main channel of the down line, a first sub-modulation unit for transmitting various control information at a relatively low speed by means of a sub-­channel of the down line, a first main demodulation unit for demodulating user data from a modulation signal received in a main channel of the up line, and a first sub-­demodulation unit for demodulating various control information from a modulation signal received in a sub-­channel of the up line, and said second MODEM unit comprises a second main demodulation unit for demodulating user data from a modulation signal received in the main channel of the down line, a second sub-demodulation unit for demodulating various control information from a modulation signal received in the sub-channel of the down line, a second main modulation unit for transmitting user data at a relatively high speed by means of the main channel of the up line, and a second sub-modulation unit for transmitting various control information at a relatively low speed by means of the sub-channel of the up line.

Claim 7

A communication system in which a plurality of multipoint connected satellite stations are connected via a down line and an up line to a master station, the master station comprising a first main modulation unit for modulating user data to transmit the modulated data at a relatively high speed by means of a main channel of the down line, a first sub-modulation unit for modulating various control information to transmit the modulated data at a relatively low speed by means of a sub-­channel of the down line, a first main demodulation unit for demodulating user data from a modulation signal received in a main channel of the up line, and a first sub-­demodulation unit for demodulating various control information from a modulation signal received in a sub-­channel of the up line, and each of the satellite stations comprising a second main demodulation unit for demodulating user data from a modulation signal received in the main channel of the down line, a second sub-demodulation unit for demodulating various control information from a modulation signal received in the sub-channel of the down line, a second main modulation unit for modulating user data to transmit the modulated data at a relatively high speed by means of the main channel of the up line, and a second sub-modulation unit for modulating various control information to transmit the modulated data at a relatively low speed by means of the sub-channel of the up line, wherein each satellite station comprises an abnormality detecting means, operatively connected to the second main demodulation unit, for controlling the second sub-modulation unit to request the master station to re-send a training signal when the abnormality detecting means detects an abnormality from the quality of a signal received at the second main demodulation unit, and the master station comprises a storing means for storing past record information concerning abnormality detection in the satellite stations and information on execution time of the retraining, obtained through the first sub-demodulation unit, and a retraining command means, operatively connected to the first sub-demodulation unit, for referring to the storing means and commanding the first main modulation unit to send the training signal when the first sub-demodulation unit receives a signal indicating the request for re-sending of the training signal from any one of the satellite stations.

Claim 8

A communication system in which a plurality of multipoint connected satellite stations are connected via a down line and an up line to a master station, the master station comprising a first main modulation unit for modulating user data to transmit the modulated data at a relatively high speed by means of a main channel of the down line, a first sub-modulation unit for modulating various control information to transmit the modulated data at a relatively low speed by means of a sub-­channel of the down line, a first main demodulation unit for demodulating user data from a modulation signal received in a main channel of the up line, and a first sub-­demodulation unit for demodulating various control information from a modulation signal received in a sub-­channel of the up line, and each of the satellite stations comprising a second main demodulation unit for demodulating user data from a modulation signal received in the main channel of the down line, a second sub-demodulation unit for demodulating various control information from a modulation signal received in the sub-channel of the down line, a second main modulation unit for modulating user data to transmit the modulated data at a relatively high speed by means of the main channel of the up line, and a second sub-modulation unit for modulating various control information to transmit the modulated data at a relatively low speed by means of the sub-channel of the up line, wherein each satellite station comprises an abnormality detecting means, operatively connected to the second main demodulation unit, for controlling the second sub-modulation unit to request the master station to re-send a training signal when the abnormality detecting means detects an abnormality from the quality of a signal received at the second main demodulation unit, and the master station comprises a storing means for storing past record information concerning abnormality detection in the satellite stations and information on execution time of the retraining, obtained through the first sub-demodulation unit, and a retraining command means, operatively connected to the first sub-demodulation unit, for referring to the storing means and commanding the first main modulation unit to send the training signal when the first sub-demodulation unit receives a signal indicating the request for re-sending of the training signal from any one of the satellite stations.

Claim 11

A method as set forth in claim 7, further comprising the step of, where the down line is abnormal, analyzing the contents of abnormality to indicate the analyzed results.

Claim 12

A method as set forth in claim 7, further comprising the steps of judging whether the satellite station equipment concerned is normal or not and, where the equipment concerned is abnormal, indicating abnormality thereof.