Earth station capable of carrying out communication without a control station

• US 5,274,626 A
• Filed: 02/02/1990
• Issued: 12/28/1993
• Est. Priority Date: 02/03/1989
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Goto, Yuji, Hotta, Toshinori
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Marielo, Melvin
• Application Number:
  US07/474,500
• Time in Patent Office: 1,425 Days
• Field of Search: 370/106.1, 370/94.1, 370/95.3, 370/31, 370/97, 370/95.1, 370/85.2, 370/85.3, 370/85.7, 370/30, 370/50, 370/75, 370/92, 371/62, 455/12.1
• US Class Current: 370/296
• CPC Class Codes: H04B 7/2123 Variable assignment, e.g. demand assignment

Abstract

In an earth station having a particular address and comprising a terminal and a transmitting section for transmitting a transmission data signal including an address signal representative of the particular address towards a satellite through a single communication channel, a receiving section receives a reception data signal comprising the transmission data signal which is sent from the satellite through the single communication channel. By detecting the particular address, a decision circuit decides whether or not the receiving section correctly receives the reception data signal within a predetermined time interval after the transmitting section starts transmission of the transmission data signal. When the receiving section does not correctly receive the reception data signal, the transmitting section stops the transmission of the transmission data signal and an alarm signal is supplied to the terminal. Alternatively, the transmission data signal may include another address signal representative of another address of another earth station.

Claims

1. An earth station for use in an SCPC (single channel per carrier) satellite communication system, said earth station being communicable with at least one other earth station via a satellite by using a single communication channel on a half duplex basis and also communicable with said other earth station via said satellite by using two communication channels on a full duplex basis, each of said earth station and said other earth station having its own particular address and including a terminal for producing a transmission request signal and subsequently an output data signal, transmitting means comprising modulating means for modulating a modulator input signal into a modulated signal and transmitting said modulated signal as a transmission data signal towards said satellite through said single communication channel when said transmitting means is supplied with said transmission request signal, and receiving means for receiving a reception data signal from said satellite through said single communication channel, wherein an improvement comprises:

generating means for generating an address signal which is representative of said particular address;

a multiplexer connected to said terminal and said generating means for multiplexing said output data signal and said address signal into a multiplexed signal;

supply means connected to said multiplexer and said transmitting means for supplying said multiplexed signal to said transmitting means via said modulating means as said modulated signal, said reception data signal comprising the transmission data signal which is sent back to said receiving means as a returning data signal through said satellite;

deciding means connected to said transmitting and said receiving means for deciding whether or not said receiving means already receives signals from other earth stations when said transmitting means starts to transmit and whether or not said receiving means receives said returning data signal as said reception data signal within a predetermined time interval after said transmitting means starts transmission of said transmission data signal, said deciding means producing a fault signal when said receiving means already receives signals from other of said earth stations when said transmitting means starts to transmit and said receiving means does not detect said particular address within said predetermined time interval; and

control means connected to said transmitting means and said deciding means for controlling said transmitting means to keep said transmission when said deciding means does not produce said fault signal and to stop said transmission when said deciding means produces said fault signal.

2. An earth station as claimed in claim 1, wherein said receiving means is connected to said terminal, and wherein said receiving means delivers an alarm signal to said terminal when said deciding means produces said fault signal.

3. An earth station as claimed in claim 1, wherein said deciding means comprises:

a demultiplexer connected to said receiving means for demultiplexing said returning data signal into a demultiplexed data signal and a separated signal corresponding to said output data signal and said address signal; and

comparing means connected to said transmitting and said generating means and to said demultiplexer for comparing said separated signal with said address signal during said predetermined time interval to produce said fault signal when said separated signal does not coincide with said address signal.