CATV communication system, method of communication by the same, and center and terminal devices thereof
First Claim
1. A communication method for a CATV communication system which comprises a center device and a plurality of terminal devices connected by CATV wired lines, said method comprising the steps of:
- (a) transmitting, from said center device to said terminal devices, cyclically a group of downstream timeslots each of which is distinctive from each other, each of said downstream timeslots including upstream timeslot occupancy information, collision information indicating whether or not a collision has occurred, and downstream data, said upstream timeslot occupancy information indicating the vacancy of an upstream timeslot corresponding to the downstream timeslot when the upstream timeslot is vacant and indicating the one of the plurality of terminals which is being assigned to the upstream timeslot when the upstream timeslot is occupied, said transmitting step (a) transmitting the upstream timeslot occupancy information regardless of whether the upstream timeslot is vacant or occupied;
(b) checking, at the terminal device, the upstream timeslot occupancy information in the downstream timeslots to detect a downstream timeslot including the upstream timeslot occupancy information of a vacant state;
(c) sending upstream data, from said terminal device to said center device, by an upstream timeslot specified by the upstream timeslot occupancy information of the vacant state at a timing corresponding to the downstream timeslot detected in the step (b);
(d) receiving, at said center device, the upstream timeslot sent in the step (c), detecting a collision of the upstream timeslots, and sending a downstream timeslot, in response to the upstream timeslot sent in the step (c), which includes the collision information set in accordance with the result of the collision detection;
(e) detecting, at said terminal device, the collision information of the downstream timeslot sent in the step (d), and sending to said center device upstream data by an upstream timeslot corresponding to the downstream timeslot sent in the step (d), if the collision is not detected; and
(f) detecting, at said center device, a carrier signal to be modulated by the upstream data in the upstream timeslots, and setting the upstream timeslot occupancy information of the downstream timeslot, corresponding to the upstream timeslot which includes no carrier signal, to the vacant state.
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Accused Products
Abstract
The CATV system includes a center device and a plurality of terminal devices. The center device sends downstream timeslots, to the terminal devices, including upstream timeslot occupancy information and collision information. Upstream timeslot occupancy information indicates whether or not an upstream timeslot corresponding to the downstream timeslot is vacant, and collision information indicates whether or not a collision has occurred. The terminal device receives the downstream timeslot, checks upstream timeslot occupancy information to detect upstream timeslot in the vacant state, and sends upstream data to the center device via the vacant upstream timeslot. If the upstream timeslot makes a collision, the center device detects it and sends a downstream timeslot which includes collision information indicative of the occurrence of the collision. The user of the terminal device recognizes the collision having occurred or not by referring to the collision information.
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Citations
25 Claims
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1. A communication method for a CATV communication system which comprises a center device and a plurality of terminal devices connected by CATV wired lines, said method comprising the steps of:
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(a) transmitting, from said center device to said terminal devices, cyclically a group of downstream timeslots each of which is distinctive from each other, each of said downstream timeslots including upstream timeslot occupancy information, collision information indicating whether or not a collision has occurred, and downstream data, said upstream timeslot occupancy information indicating the vacancy of an upstream timeslot corresponding to the downstream timeslot when the upstream timeslot is vacant and indicating the one of the plurality of terminals which is being assigned to the upstream timeslot when the upstream timeslot is occupied, said transmitting step (a) transmitting the upstream timeslot occupancy information regardless of whether the upstream timeslot is vacant or occupied; (b) checking, at the terminal device, the upstream timeslot occupancy information in the downstream timeslots to detect a downstream timeslot including the upstream timeslot occupancy information of a vacant state; (c) sending upstream data, from said terminal device to said center device, by an upstream timeslot specified by the upstream timeslot occupancy information of the vacant state at a timing corresponding to the downstream timeslot detected in the step (b); (d) receiving, at said center device, the upstream timeslot sent in the step (c), detecting a collision of the upstream timeslots, and sending a downstream timeslot, in response to the upstream timeslot sent in the step (c), which includes the collision information set in accordance with the result of the collision detection; (e) detecting, at said terminal device, the collision information of the downstream timeslot sent in the step (d), and sending to said center device upstream data by an upstream timeslot corresponding to the downstream timeslot sent in the step (d), if the collision is not detected; and (f) detecting, at said center device, a carrier signal to be modulated by the upstream data in the upstream timeslots, and setting the upstream timeslot occupancy information of the downstream timeslot, corresponding to the upstream timeslot which includes no carrier signal, to the vacant state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 19, 23)
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8. A CATV communication system comprising a center device and a plurality of terminal devices connected by CATV wired lines, said center device comprising:
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a downstream timeslot sending means for cyclically sending a group of downstream timeslots to the terminal devices, each of said downstream timeslots being distinctive from each other and indicating upstream timeslot occupancy information, collision information indicating whether or not a collision has occurred, and downstream data, said upstream timeslot occupancy information indicating the vacancy of an upstream timeslot corresponding to the downstream timeslot when the upstream timeslot is vacant and indicating the one of the plurality of terminals which is being assigned to the timeslot when the upstream timeslot is occupied, said downstream timeslot sending means sending the upstream timeslot occupancy information regardless of whether the upstream timeslot is vacant or occupied; a collision information setting means for detecting the collision of the upstream timeslots and for setting the collision information of the downstream timeslot in accordance with the result of the collision detection; and an occupancy information setting means for detecting a carrier signal to be modulated by upstream data in the upstream timeslots, and for setting the upstream timeslot occupancy information of the downstream timeslot to a vacant state when the upstream timeslot including no carrier signal is detected, and each of said terminal device comprising; a vacant timeslot detecting means for checking the upstream timeslot occupancy information in the downstream timeslots to detect a vacant upstream timeslot specified by the upstream timeslot occupancy information; a collision information checking means for checking the collision information in the downstream timeslots to detect the collision; and an upstream timeslot sending means for sending the upstream data to said center device by the vacant upstream timeslot at a timing corresponding to the downstream timeslot including the upstream timeslot occupancy information of the vacant state, unless said collision information checking means detects the collision. - View Dependent Claims (9, 10, 11, 12, 20, 24)
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13. A center device of CATV communication system connected with a plurality of terminal devices via CATV wired lines, said center device comprising:
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a downstream timeslot sending means for cyclically sending a group of downstream timeslots to the terminal devices, each of said downstream timeslots being distinctive from each other and including upstream timeslot occupancy information, collision information indicating whether or not a collision has occurred, and downstream data, said upstream timeslot occupancy information indicating the vacancy of an upstream timeslot corresponding to the downstream timeslot when the upstream timeslot is vacant and indicating the one of the plurality of terminal which is being assigned to the timeslot when the upstream timeslot is occupied, said downstream timeslot sending means sending the upstream timeslot occupancy information regardless of whether the timeslot is vacant or occupied; a collision information setting means for detecting the collision of the upstream timeslots and for setting the collision information of the downstream timeslot in accordance with the result of the collision detection; and an occupancy information setting means for detecting a carrier signal to be modulated by upstream data in the upstream timeslots, and for setting the upstream timeslot occupancy information of the downstream timeslot to a vacant state when the upstream timeslot including no carrier signal is detected. - View Dependent Claims (14, 15, 16, 17, 21)
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18. A terminal device of a CATV communication system connected, via CATV wired lines, with a center device which cyclically sends a group of downstream timeslots to the terminal device, each of said downstream timeslots being distinctive from each other and including upstream timeslot occupancy information, said upstream timeslot occupancy information indicating the vacancy of an upstream timeslot corresponding to the downstream timeslot when the upstream timeslot is vacant and indicating the one of the plurality of terminal which is being assigned to the timeslot when the upstream timeslot is occupied, collision information indicating whether or not a collision has occurred, and downstream data, said terminal device comprising:
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a vacant timeslot detecting means for checking the upstream timeslot occupancy information in the downstream timeslots to detect a vacant upstream timeslot specified by the upstream timeslot occupancy information; a collision information checking means for checking the collision information in the downstream timeslots to detect the collision; and an upstream timeslot sending means for sending the upstream data to said center device by the vacant upstream timeslot at a timing corresponding to the downstream timeslot including the upstream timeslot occupancy information of the vacant state, unless said collision information checking means detects the collision. - View Dependent Claims (22, 25)
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Specification