TERRESTRIAL INTERFACE UNIT

• US 3,683,116 A
• Filed: 07/16/1969
• Issued: 08/08/1972
• Est. Priority Date: 07/16/1969
• Status: Expired due to Term

• Current Assignee: International Telecommunications Satellite Organization
• Original Assignee: George D. Dill
• Inventors: George, D. Dill
• Primary Examiner(s): Ralph D. Blakeslee
• Application Number:
  US04/842,838
• Time in Patent Office: 1,119 Days
• Field of Search: 325/4 179/15BY,15AS,15A,15AT,15BF,15BS 343/100ST
• US Class Current: 370/321
• CPC Class Codes: H04B 7/18528 Satellite systems for providing two-way communications service to a network of fixed stations, i.e. fixed satellite service or very small aperture terminal [VSAT] system
• CPC Class Codes: H04J 3/12 Arrangements providing for calling or supervisory signals
• CPC Class Codes: H04Q 11/00 Selecting arrangements for multiplex systems multiplex systems H04J
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

In a demand assigned multiple access system, a chosen satellite RF frequency band is divided on the basis of assigning a single voice channel per RF carrier. The RF band, thus divided, forms a '"'"''"'"''"'"''"'"'pool'"'"''"'"''"'"''"'"' of frequencies. The demand assigned multiple access system is fully variable, allowing all circuits to be selected by any station on demand. Thus, neither end of a channel is permanently associated with any terminal point, and the channels are paired to form a connection as required within the demand assignment pool. The system does not require a central station for system control, but instead uses a demand assignment signaling and switching unit for self-assignment of channels based on continually updated channel allocation status data provided via a common signaling channel. The common signaling channel is used to continuously apprise each earth station demand assignment signaling and switching unit of the availability of pool channels and to establish links directly with other stations. The demand assigned multiple access terminal is designed to be operated with all types of international telephone exchanges. Because of the variations in workings of the several different types of telephone exchanges, two basic types of telephone central to demand assignment multiple access terminal interfaces are provided. The first type of interface provides for individual channel signaling. This entails the communication of all signaling with the individual access circuits. The second type of interface provides for common channel signaling. This entails the communication of all signaling between the telephone central and the demand assignment multiple access terminal via a separate signaling channel. In all cases, the combined operation of the terrestrial interface unit and the demand assignment signaling and switching unit is such that the signaling between the telephone central and the demand assigned multiple access terminal is the same as if it were between two telephone centrals.

Claims

1. A method of operating a demand assigned multiple access terminal with an international telephone exchange said terminal being used for communicating to remote terminals via a satellite relay and being adapted to acquire an available satellite circuit to carry information between said terminal and said remote terminal, said method being such that the signaling between the international exchange and the demand assigned multiple access terminal is the same as if it were between two exchanges, said method comprising the steps of a. receiving at said terminal all signaling information normally provided by the exchange, b. connecting the four-wire full duplex voice circuits from the exchange to the terminal as required to properly initiate, supervise and terminate a call, c. transmitting all required signaling information from said terminal to the exchange, and d. conducting a circuit continuity test upon the acquisition by said terminal of any of said satellite circuits.

2. The method as recited in claim 1 wherein the step of receiving includes receiving a seizure signal from the exchange and wherein the step of transmitting includes transmitting a proceed-to-send signal to the exchange after a register has been selected at the terminal in response to the seizure signal.

3. The method as recited in claim 1 wherein the step of conducting a circuit continuity test includes the steps of a. transmitting a check tone of fixed time duration through the satellite relay link, and b. registering the return receipt of at least a predetermined time portion of that check tone when operating as the called terminal.

4. The method as recited in claim 3 wherein the step of registering must be performed within a predetermined time period and failure to do so results in the transmission of a check-not-ok signal from the called terminal to the calling terminal.

5. The method as recited in claim 3 wherein a check-OK signal is transmitted from the called terminal to the calling terminal if the step of registering is performed within a predetermined time period.

6. A terrestrial interface unit for connecting a demand assigned multiple access terminal used for communications via a satellite relay with an international telephone exchange which permits signaling between the international exchange and the demand assigned multiple access terminal as if it were between two exchanges, said terminal including a plurality of channel units and equipment common to all channel units for controlling the access thereto including a switching and signaling processor, said interface comprising:

a. a trunk circuit relay group for connecting any four-wire voice circuit from the exchange to an associated channel unit, b. a continuity check transceiver connected to said trunk circuit relay group and controlled by said switching and signaling processor in said terminal for transmitting a check tone of fixed time duration through the satellite relay link via said trunk circuit relay group and for receiving the return of at least a predetermined time portion of that check tone when operating as the called terminal, and c. An interface buffer controller connected between said trunk circuit relay group and said common equipment in said terminal, said interface buffer controller including input and output registers and control logic means for transferrinG monitoring and control data between the terrestrial interface unit and the switching and signaling processor in the terminal.

7. A terrestrial interface unit as recited in claim 6 wherein said interface buffer controller comprises:

a. a common data transfer control unit for transferring data into and out of the switching and signaling processor in the terminal, b. a device decoder connected to receive data from said common data transfer control unit for selecting the terrestrial interface unit in response to coded signals from the switching and signaling processor, and c. a function decoder connected to receive data from said common data transfer control unit for controlling the input and output registers of said interface buffer controller.

8. A terrestrial interface unit as recited in claim 6 further comprising line signaling equipment for providing four-wire duplex circuit interface to both the access circuits and the trunk circuit relay group for each access circuit interfaced to the terminal.