Communication system for varying timing offset to accommodate variation in propagation delay

• US 5,640,672 A
• Filed: 05/31/1995
• Issued: 06/17/1997
• Est. Priority Date: 06/01/1994
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Nawata, Hizuru
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): ARMSTRONG, DARNELL R
• Application Number:
  US08/455,208
• Time in Patent Office: 748 Days
• Field of Search: 455/13.1, 455/13.2, 455/12.1, 455/69, 455/67.5, 455/51.1
• US Class Current: 455/12.1
• CPC Class Codes: H04B 7/2125 Synchronisation

Abstract

In a communication system for transmitting and receiving burst signal between a round-trip satellite and a ground station, upon transmission of a transmitting burst signal from the round-trip satellite, a standard time upon transmission is added to the transmitting burst signal. In the ground station, the time data added to the transmitting burst data is extracted and compared with the standard time upon reception to derive a transmission delay period. A transmission timing of a burst signal to be transmitted from the own station is controlled depending upon the transmission delay period. By this, even when a distance between the ground station and the round-trip satellite is varied, overlapping of the burst signals in the time slots on the same time axis can be successfully avoided. Also, a guard time can be shortened to contribute for improvement of the transmission efficiency.

Claims

1. A communication system for performing communication with at least one burst signal between ground stations via a communication satellite, said system comprising:

said communication satellite including;

a first clock generating means for generating a first time data corresponding to a standard time of said ground station; and

transmission means for adding said first time data to transmission signals to form the burst signal and for transmitting the burst signal;

each of said ground stations including;

a second clock generating means for generating a second time data corresponding to said standard time;

receiving means for receiving the burst signal transmitted from said communication satellite;

comparing means for comparing said first time data added to the burst signal and received by said receiving means with said second time data of said second clock generating means; and

transmitting means for transmitting the burst signal to be transmitted from a respective ground station to said communication satellite and for controlling a transmission delay period depending upon the result of comparison by said comparing means.

2. A communication system as set forth in claim 1, wherein said transmitting means of said ground station doubles the result of comparison by said comparing means, derives an offset value by subtracting the doubled value from a predetermined fixed value, and sets said offset value as said transmission delay period for the burst signal to be transmitted.

3. A communication system as set forth in claim 2, wherein said fixed value is an integer multiple of the length of a time slot to be superimposed on the burst signal and a guard time length added thereto.

4. A communication system as set forth in claim 1, wherein said communication satellite is a lower orbit satellite.

5. A communication system for performing communication between ground stations with at least one burst signal through a communication satellite, said system comprising:

said communication satellite including;

a first clock generating means for generating a first time data corresponding to a standard time of said ground station; and

transmission means for adding a transmitting frame timing signal and said first time data of said first clock generating means to transmission signals to form the burst signal and for transmitting the burst signal;

each of said ground station including;

a second clock generating means for generating a second time data corresponding to said standard time;

receiving means for receiving the burst signal transmitted from said communication satellite;

reference timing signal generating means for extracting said frame timing signal added by said satellite transmission means and received by said receiving means and for generating a reference timing signal for determining a transmission timing of a transmitting burst data of a respective ground station;

time data extracting means for extracting said first time data added by said satellite transmission means on the basis of said reference timing;

comparing means for comparing the extracted time data and said second time data of said second clock generating means; and

transmitting means for transmitting the burst signal to be transmitted from a respective ground station to said communication satellite and for providing a delay for a delay period depending upon the result of comparison by said comparing means.

6. A communication system as set forth in claim 5, wherein said transmitting means of said ground station doubles the result of comparison by said comparing means, derives an offset value by subtracting the doubled value from a predetermined fixed value, and sets said offset value as said transmission delay period for the burst signal to be transmitted.

7. A communication system as set forth in claim 6, wherein said fixed value is an integer multiple of the length of a time slot to be superimposed on the burst signal and a guard time length added thereto.

8. A communication system as set forth in claim 5, wherein said communication satellite is a lower orbit satellite.

9. A communication system as set forth in claim 5, wherein said transmitting frame timing signal is a unique word.