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Compression of data on status of remote equipment
| Details |
Inventors: Brown, Harry H.;
Assignee: General Electric Company (Schenectady, NY)
Primary Examiner: Pitts; Harold I.
Assistant Examiner:
Attorney, Agent or Firm: Amgott; Allen E., Quist; Raymond H.
In communication system comprising plurality of earth stations tied together by relay (e.g. satellite-borne) in which status of individual subscriber line interface units must be continually reported to central control unit, only status changed since previous interrogation cycle is reported, with unchanged units being skipped over. When control is via satellite-borne relay, control unit sends interrogation commands to different stations at such time intervals that the report from one station arrives just as that from another station ends. For long transit times, this may result in all interrogation signals being transmitted before the first report in the sequence is received. |
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DETAILED DESCRIPTION The environment of this invention is a communication system in which each of a number of ground stations connected by a remote relay, in general satellite-borne, has a number of incoming subscriber channels, each of which is connected into the system through an interface unit, described herein as a channel unit, acronym CU.
Each interface unit or CU is capable of being tuned to any one of a number of transmitting frequencies and any one of a number of receiving frequencies; these are assigned as required by a central control located at one ground station.
For optimum utilization of the available frequency channels, it is essential that the central control be kept informed continually of the status of each CU,-- that is, if it is awaiting a frequency assignment, or has terminated its message and no longer requires its assigned frequencies, and the like.
In the present invention, the central unit is assumed to address each CU with the earth station identification, followed by a control word indicating that status information is requested, which is herein designated for obvious reasons as a "poll" word.
Means are provided to identify the earth station and the CU address, and thereupon to enter the control word into a function table which activates an output lead indicating that a poll word has been received.
A signal indicating the current status is stored in a register, and connected to means for determining if there has been a change in status since the last poll.
If there has been no change, the CU does not respond.
If there has been a change, the CU generates a signal giving its earth station and CU address and the status signal.
While it is transmitting this message, it produces a signal on a busy bus which inhibits transmission by any other CU.
If the busy bus has a signal on it when the CU first attempts to send its message, it is delayed in doing so until the busy bus signal has terminated.
Thus every CU which has a status change to report will report its status, and no other CU will do so
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