Satellite communication system with variable number of satellite communication channels

• US 5,805,573 A
• Filed: 08/15/1995
• Issued: 09/08/1998
• Est. Priority Date: 08/15/1994
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Umeda, Kenji
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): VU, HUY DUY
• Application Number:
  US08/518,295
• Time in Patent Office: 1,120 Days
• Field of Search: 370/229, 370/232, 370/233, 370/234, 370/230, 370/280, 370/315, 370/316, 370/310, 370/321, 370/326, 370/345, 370/347, 370/431, 370/432, 370/433, 370/437, 370/442, 370/458, 370/465, 370/468, 370/480, 370/496, 370/521, 370/330, 370/436, 370/478, 370/319, 370/252, 370/445, 370/447, 445/12.1, 445/13.1, 445/69, 445/70, 445/71, 445/73, 445/113, 445/150.1, 445/151.1, 445/179.1, 445/52.2, 379/57, 379/58, 379/59, 379/60
• US Class Current: 370/321
• CPC Class Codes: H04B 7/2123 Variable assignment, e.g. demand assignment

Abstract

A central station is connected to a plurality of remote stations through in-bound channels and out-bound channels. Data is transmitted from the respective remote stations to the central station through the in-bound channels and data is transmitted from the central station to all of the remote stations through the out-bound channels. Possibility of data transmission delay is reduced by changing the number of either or both of the in-bound channels and the out-bound channels according to a variation of amount of data transmitted/received between the remote statios and the central station.

Claims

1. A satellite communication system comprising a central station and a plurality of remote stations connected to said central station through channels, each of said remote stations adapted to transmit data to only said central station in time-division multiple access through at least one first channel and said central station being adapted to transmit same data to the plurality of said remote stations through at least one second channel;

said central station comprising;

receiving means for obtaining a first data by demodulating a signal from said remote stations;

first monitor means for monitoring an amount of the first data received by said receiving means;

first channel setting means for determining the number of said at least one first channel and frequencies of each of said at least one first channel on the basis of the monitored data amount and outputting a first control data indicative of an information of the determined number and the determined frequencies of said at least one first channel;

transmitting means for transmitting the first control data to the plurality of said remote stations;

second monitor means for monitoring an amount of the second data transmitted from at least one second terminal connected to said central station;

second channel setting means for determining the number and frequencies of said at least one second channel on the basis of the data amount monitored by said second monitor means and outputting a second control data indicative of an information of the determined number and the determined frequencies of said at least one second channel; and

multiplexing means for multiplexing the first control data, the second control data and the second data transmitted from said at least one second terminal and supplying a resultant multiplexed signal to said transmitting means;

each of said remote stations comprising;

receiving means for obtaining a second data by demodulating a signal transmitted from said central station;

separator means for separating the first control data from the second data;

transmitting means for transmitting data from a respective one of at least one first terminal, each remote station being connected to said respective first terminal, to said central station;

first channel control means for controlling said at least one first channel used by said transmitting means on the basis of the first control data separated by said separator means; and

second channel control means for controlling which of said at least one second channel is used by said receiving means on the basis of the second control data.

2. The satellite communication system as claimed in claim 1, wherein said separator means separates the multiplexed signal transmitted from said central station to the first control data, the second control data and the second data transmitted from said at least one second terminal.

3. A satellite communication system comprising a central station and a plurality of remote stations connected to said central station through channels, each of said remote stations adapted to transmit data to only said central station in time-division multiple access through at least one first channel and said central station being adapted to transmit same data to the plurality of said remote stations through at least one second channel;

said central station comprising;

receiving means for obtaining a first data by demodulating a signal from said remote stations;

first monitor means for monitoring an amount of the first data received by said receiving means;

first channel setting means for determining the number of said at least one first channel and frequencies of each of said at least one first channel on the basis of the monitored data amount and outputting a first control data indicative of an information of the determined number and the determined frequencies of said at least one first channel; and

transmitting means for transmitting the first control data to the plurality of said remote stations;

each of said remote stations comprising;

receiving means for obtaining a second data by demodulating a signal transmitted from said central station;

separator means for separating the first control data from the second data;

transmitting means for transmitting data from a respective one of at least one first terminal, each remote station being connected to said respective first terminal, to said central station; and

first channel control means for controlling said at least one first channel used by said transmitting means on the basis of the first control data separated by said separator means;

wherein said first monitor means comprises counting means for counting the number of collisions of the first data transmitted from each of said remote stations to said central station with other data in the same time slot.

4. The satellite communication system as claimed in claim 3, wherein said first monitor means comprises:

a timer circuit for outputting a reset signal every predetermined time; and

counting means for counting the number of NAK signals transmitted from said central station to said remote stations when said central station does not normally receive the first data transmitted from said remote stations to said central station between each output of the reset signal from said timer circuit.

5. A satellite communication system comprising a central station and a plurality of remote stations connected to said central station through channels, each of said remote stations adapted to transmit data to only said central station in time-division multiple access through at least one first channel and said central station being adapted to transmit same data to the plurality of said remote stations through at least one second channel;

said central station comprising;

receiving means for obtaining a first data by demodulating a signal from said remote stations;

first monitor means for monitoring an amount of the first data received by said receiving means;

first channel setting means for determining the number of said at least one first channel and frequencies of each of said at least one first channel on the basis of the monitored data amount and outputting a first control data indicative of an information of the determined number and the determined frequencies of said at least one first channel;

transmitting means for transmitting the first control data to the plurality of said remote stations; and

identification means for identifying one of said remote stations which transmits the first data, and wherein said first monitor means monitors an amount of the first data transmitted through every said first channel on the basis of a result of identification from said identification means;

each of said remote stations comprising;

receiving means for obtaining a second data by demodulating a signal transmitted from said central station;

separator means for separating the first control data from the second data;

transmitting means for transmitting data from a respective one of at least one first terminal, each remote station being connected to said respective first terminal, to said central station; and

first channel control means for controlling said at least one first channel used by said transmitting means on the basis of the first control data separated by said separator means.

6. A satellite communication system comprising a central station and a plurality of remote stations connected to said central station through channels, each of said remote stations adapted to transmit data to only said central station in time-division multiple access through at least one first channel and said central station being adapted to transmit same data to the plurality of said remote stations through at least one second channel;

said central station comprising;

receiving means for obtaining a first data by demodulating a signal from said remote stations;

first monitor means for monitoring an amount of the first data received by said receiving means;

first channel setting means for determining the number of said at least one first channel and frequencies of each of said at least one first channel on the basis of the monitored data amount and outputting a first control data indicative of an information of the determined number and the determined frequencies of said at least one first channel; and

transmitting means for transmitting the first control data to the plurality of said remote stations;

each of said remote stations comprising;

receiving means for obtaining a second data by demodulating a signal transmitted from said central station;

separator means for separating the first control data from the second data;

transmitting means for transmitting data from a respective one of at least one first terminal, each remote station being connected to said respective first terminal, to said central station; and

first channel control means for controlling said at least one first channel used by said transmitting means on the basis of the first control data separated by said separator means;

wherein said first channel setting means comprises;

storing means for preliminarily storing the optimum number of said at least one first channel corresponding to the amount of the first data;

read means for reading out the optimum number of said at least one first channel from said storing means on the basis of the amount of the first data; and

means for setting the number of said first channels thus read out from said storing means and determining frequencies of said at least one first channel.

7. In a satellite communication system including a central station and a Plurality of remote stations connected to said central station through channels, the plurality of said remote stations adapted to transmit in time-division multiple access data to said central station through at least one first channel, and said central station being adapted to transmit identical data to the plurality of said remote stations through at least one second channel;

said central station comprising;

receiving means for obtaining a first data by demodulating a signal from said remote stations;

first monitor means for monitoring an amount of the first data received by said receiving means;

first channel setting means for determining the number of said at least one first channel and frequencies of each of said at least one first channel on the basis of the monitored data amount and outputting a first control data indicative of an information of the determined number and the determined frequencies of said at least one first channel;

transmitting means for transmitting the first control data to the plurality of said remote stations;

second monitor means for monitoring an amount of second data transmitted from at least one terminal connected to said central station;

second channel setting means for determining the number and frequencies of said at least one second channel on the basis of the data amount monitored by said second monitor means and outputting a second control data indicative of an information of the determined number and the determined frequencies of said at least one second channel; and

multiplexing means for multiplexing the first control data, the second control data and the second data transmitted from said terminal and supplying a resultant multiplexed signal to said transmitting means.

8. In a satellite communication system including a central station and a plurality of remote stations connected to said central station through channels, the plurality of said remote stations adapted to transmit in time-division multiple access data to said central station through at least one first channel, and said central station being adapted to transmit identical data to the plurality of said remote stations through at least one second channel;

said central station comprising;

receiving means for obtaining a first data by demodulating a signal from said remote stations;

first monitor means for monitoring an amount of the first data received by said receiving means;

first channel setting means for determining the number of said at least one first channel and frequencies of each of said at least one first channel on the basis of the monitored data amount and outputting a first control data indicative of an information of the determined number and the determined frequencies of said at least one first channel; and

transmitting means for transmitting the first control data to the plurality of said remote stations;

wherein said first monitor means comprises counting means for counting the number of data collisions of the first data transmitted from said remote stations to said central station with other data in the same time slot in a predetermined time.

9. In a satellite communication system including a central station and a plurality of remote stations connected to said central station through channels, the plurality of said remote stations adapted to transmit in time-division multiple access data to said central station through at least one first channel, and said central station being adapted to transmit identical data to the plurality of said remote stations through at least one second channel;

said central station comprising;

receiving means for obtaining a first data by demodulating a signal from said remote stations;

first monitor means for monitoring an amount of the first data received by said receiving means;

first channel setting means for determining the number of said at least one first channel and frequencies of each of said at least one first channel on the basis of the monitored data amount and outputting a first control data indicative of an information of the determined number and the determined frequencies of said at least one first channel; and

transmitting means for transmitting the first control data to the Plurality of said remote stations;

wherein said first monitor means comprises;

a timer circuit for outputting a reset signal every predetermined time; and

counting means for counting the number of NAK signals transmitted from said central station to said remote stations when said central station does not normally receive the first data transmitted from said remote stations to said central station, between each output of the reset signal from said timer circuit.

10. In a satellite communication system including a central station and a plurality of remote stations connected to said central station through channels, the plurality of said remote stations adapted to transmit in time-division multiple access data to said central station through at least one first channel, and said central station being adapted to transmit identical data to the plurality of said remote stations through at least one second channel;

said central station comprising;

receiving means for obtaining a first data by demodulating a signal from said remote stations;

first monitor means for monitoring an amount of the first data received by said receiving means;

first channel setting means for determining the number of said at least one first channel and frequencies of each of said at least one first channel on the basis of the monitored data amount and outputting a first control data indicative of an information of the determined number and the determined frequencies of said at least one first channel;

transmitting means for transmitting the first control data to the plurality of said remote stations; and

identification means for identifying one of said remote stations which transmits the first data and wherein said first monitor means monitors an amount of the first data transmitted through every said first channel on the basis of a result of identification from said identification means.

11. In a satellite communication system including a central station and a plurality of remote stations connected to said central station through channels, the plurality of said remote stations adapted to transmit in time-division multiple access data to said central station through at least one first channel, and said central station being adapted to transmit identical data to the plurality of said remote stations through at least one second channel;

each of said remote stations comprising;

receiving means for obtaining a second data by demodulating a signal transmitted from said central station;

separator means for separating the first control data from the second data;

transmitting means for transmitting data from a respective one of at least one first terminal, each remote station being connected to said respective first terminal, to said central station;

first channel control means for controlling said at least one first channel used by said transmitting means on the basis of the first control data separated by said separator means; and

second channel control means for controlling which one of said at least one second channel is used by said receiving means on the basis of a second control data indicative of an information of the number of said at least one second channel and frequencies of said at least one second channel transmitted from said central station.

12. The remote station as claimed in claim 11, wherein said separator means separates the signal transmitted from said central station to the first control data, the second control data and the second data transmitted from a second terminal connected to the said central station.

13. A satellite communication system comprising a central earth station and a plurality of very small aperture terminal stations connected to said central earth station through satellite circuits, each of said very small aperture terminal stations being adapted to transmit data to only said central earth station in time-division multiple access through at least one in-bound channel, and said central station being adapted to transmit same data to the plurality of said very small aperture terminal stations through at least one out-bound channel, a plurality of first terminals being connected to respective ones of the plurality of said very small aperture terminal stations, for generating data to be transmitted in time slots of said in-bound channels by a time slot reservation system or a random access system according to length of the transmitted data;

said central earth station comprising;

receiving means for obtaining a first data by demodulating a signal from the plurality of said very small aperture terminal stations;

first monitor means for monitoring an amount of the first data received by said receiving means;

first channel setting means for determining the number of said at least one in-bound channel and frequencies of each of said at least one in-bound channel on the basis of the monitored data amount and outputting a first control data indicative of an information of the determined number and the determined frequencies of said at least one in-bound channel;

transmitting means for transmitting the first control data to the plurality of said very small aperture terminal stations;

second monitor means for monitoring an amount of the second data transmitted from at least one second terminal connected to said central earth station;

second channel setting means for determining the number and frequencies of said at least one out-bound channel on the basis of the data amount monitored by said second monitor means and outputting a second control data indicative of an information of the determined number and the determined frequencies of said at least one out-bound channel; and

multiplexing means for multiplexing the first control data, the second control data and the second data transmitted from said second terminal and supplying a resultant multiplexed signal to said transmitting means, and wherein each said very small aperture terminal station further comprises second circuit control means for controlling the number of said at least one out-bound channel and frequencies of said at lest one out-bound channel used by said receiving means on the basis of the second control data;

each of said very small aperture terminal stations comprising;

receiving means for obtaining a second data by demodulating a signal transmitted from said central earth station;

separator means for separating the first control data from the second data;

transmitting means for transmitting data, from one of the plurality of first terminals respectively connected to said each of said very small aperture terminal stations, to said central earth station; and

first channel control means for controlling said at least one in-bound channel used by said transmitting means and frequencies of said in-bound channels on the basis of the first control data separated by said separator means.

14. A satellite communication system as comprising a central station and a plurality of remote stations connected to said central station through channels the plurality of said remote stations being adapted to transmit data to said central station through at least one first channel of said channels, said central station being adapted to transmit identical data to the plurality of said remote stations through at least one second channel of said channels, said central station comprising:

means for detecting an amount of data transmitted from said remote stations to said central station;

means for changing the number of said at least one first channel according to the detected data amount;

means for detecting an amount of data transmitted from said central station to said remote stations; and

means for changing the number of said at least one second channel according to the detected data amount.

15. A satellite communication method for use in a satellite communication system comprising a central station and a plurality of remote stations connected to said central station through satellite circuits the plurality of said remote stations being adapted to transmit data to said central station through at least one first channel, said central station being adapted to transmit identical data to the plurality of said remote stations through at least one second channel, said method comprising the steps of:

detecting an amount of data transmitted from said remote stations to said central station;

changing the number of said at least one first channel according to the detected data amount;

detecting an amount of data transmitted from said central station to said remote stations; and

changing the number of said at least one second channel according to the detected amount of data transmitted from said central station to said remote stations.

16. A satellite communication method for use in a satellite communication system comprising a central station and a plurality of remote stations connected to said central station through channels the plurality of said remote stations being adapted to transmit data to said central station through at least one first channel of said channels, said central station being adapted to transmit identical data to the plurality of said remote stations through at least one second channel of said channels, said method comprising the steps of:

detecting an amount of data transmitted from said remote stations to said central station within a predetermined time;

setting the optimum number of said at least one first channel on the basis of the detected data amount;

determining frequencies of each of the thus set optimum number of at least one first channel and assigning the frequencies to respective ones of said remote stations;

transmitting data indicative of the correspondence of the frequencies of said at least one first channel to said respective remote stations, from said central station to said remote stations;

changing the transmitting frequencies of said remote stations to the assigned frequencies of said at least one first channels

detecting an amount of data transmitted from said central stations to said remote stations within a predetermined time;

setting the optimum number of said at least one second channel on the basis of the detected data amount;

determining frequencies of each of said optimum number of second channels and assigning the frequencies to respective ones of said remote stations;

transmitting data indicative of the frequencies of said second channels assigned to said respective ones of said remote stations from said central station to said remote stations; and

changing the receiving frequencies of said remote stations to the respective assigned frequencies of said second channels.

17. A control method for controlling a central station of a satellite communication system comprising said central station and a plurality of remote stations connected to said central station through channels, the plurality of said remote stations being adapted to transmit data to said central station through at least one first channel of said channels, said central station being adapted to transmit identical data to the plurality of said remote stations through at least one second channel of said channels, said control method comprising the steps of:

detecting an amount of data transmitted from said remote stations to said central station within a predetermined time;

setting the optimum number of said at least one first channel on the basis of the detected data amount;

determining frequencies of each of the thus set optimum number of at least one first channel and assigning the frequencies to respective ones of said remote stations;

transmitting data, from said central station to said remote stations, indicative of the frequencies of the at least one first channel assigned to said respective remote stations;

detecting an amount of data transmitted from said central station to said remote stations within a predetermined time;

setting the optimum number of said at least one second channel on the basis of the detected data amount;

determining frequencies of each of said optimum number of second channels and assigning the frequencies to respective ones of said remote stations; and

transmitting data indicative of the frequencies of said second channels assigned to said respective ones of said remote stations from said central station to said remote stations.

18. A control method for controlling each of a plurality of remote stations of a satellite communication system comprising a central station and the plurality of remote stations connected to said central station through channels, the plurality of said remote stations being adapted to transmit data to said central station through at least one first channel of said channels, said central station being adapted to transmit identical data to the plurality of said remote stations through at least one second channel of said channels, said control method comprising the steps of:

separating a newly assigned first frequency data of said at least one first channel from a signal transmitted from said central station;

changing transmitting frequencies for transmitting data from said remote stations to said central station on the basis of the separated first frequency data;

separating a newly assigned second frequency data of said at least one second channel from the signal transmitted from said central station; and

changing receiving frequencies for receiving data from said central station to said remote stations on the basis of the separated second frequency data.