CONTROL SYSTEM FOR DIVERSITY TRANSMISSION IN A TERRESTRIAL STATION OF SATELLITE COMMUNICATION

• US 3,829,777 A
• Filed: 02/02/1973
• Issued: 08/13/1974
• Est. Priority Date: 02/10/1972
• Status: Expired due to Term

• Current Assignee: Hideki Saito, Takuro Muratani, Tatsuo Watanabe
• Original Assignee: Hideki Saito, Takuro Muratani, Tatsuo Watanabe
• Inventors: Muratani, Takuro, Saito, Hideki, Watanabe, Tatsuo
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US05/329,206
• Time in Patent Office: 557 Days
• Field of Search: 325/4,15,56,41,42 179/15A,15BA,15BS 343/5LC 178/50
• US Class Current: 455/8
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity

Abstract

A control system for diversity transmission from a terrestrial station which performs time-division multiple access to a satellite communication repeater through a selected one of a plurality of transmission paths established between the satellite and the terrestrial station, in which the transmission paths are alternately selected in synchronism with a signal received over a selected one of the transmission paths when the error rate of all the transmission paths is lower than a reference threshold value, and in which a selected one of the transmission paths having the lowest error rate is continuously used when the error rates of the transmission paths are not all lower than the reference threshold value.

Claims

1. In a control system for controlling diversity transmission between a satellite communications repeater and a terrestrial station having a plurality of antennas establishing separate signal paths between the terrestrial station and the satellite for providing time-division multiple access to the satellite repeater, wherein the improvement comprises:

a. error rate monitor means at said terrestrial station for developing a plurality of error rate signals each representative of an error rate of a corresponding one of said signal paths;

b. comparison means at said terrestrial station developing in response to said error rate signals a first output signal when the error rate of all of said signal paths are lower than a predetermined reference rate and developing a second output signal iNdicating which of said signal paths has the lowest error rate;

c. means applying said error rate signals to said comparison means;

d. timing means receptive of said comparison means second output signal for developing timing signals synchronized with signals received at said terrestrial station over said signal path having the lowest error rate;

e. means applying said comparison means second output signal to said timing means;

f. switch means in said terrestrial station receptive of said timing signals and said comparison means first and second output signals for alternately selecting each of said signal paths for transmission in synchronism with said timing signals thereover to said satellite repeater in response to said comparison means first output signal, and for selecting said signal path having the lowest error rate for transmission in synchronism with said timing signals thereover to said satellite repeater in response to said comparison means second output signal in the absence of said comparison means first output signal; and

g. means applying said timing signals and said comparison means first and second output signals to said switch means.

2. A control system for diversity transmission according to claim 1, in which said error rate monitor means comprises a bit-error detector for each of said signal paths for developing error pulses equal in number to the number of bit errors occurring over a corresponding one of said signal paths.

3. A control system for diversity transmission according to claim 2, in which the comparison means comprises a plurality of counters respectively counting in a predetermined time said error pulses from said bit-error detectors, a plurality of discriminators each connected to a corresponding one of the counters for each providing an output when the counting state of the corresponding counter exceeds a threshold value, an AND circuit connected to all of said discriminators for providing said first output, and a comparator connected to said counters for providing said second output.