COMMUNICATION SYSTEM POLLING METHOD

• US 3,755,782 A
• Filed: 08/28/1972
• Issued: 08/28/1973
• Est. Priority Date: 08/28/1972
• Status: Expired due to Term

• Current Assignee: Larry D. Larsen, Lee C. Haas, Lynn P. West
• Original Assignee: Larry D. Larsen, Lee C. Haas, Lynn P. West
• Inventors: Haas, Lee C., Larsen, Larry D., West, Lynn P.
• Primary Examiner(s): Yusko, Donald J.
• Application Number:
  US05/284,310
• Time in Patent Office: 365 Days
• Field of Search: 340/147R,163
• US Class Current: 340/10.2
• CPC Class Codes: H04L 12/403 with centralised control, e.g. polling

Abstract

A polling scheme is disclosed in which a plurality of remote terminals or stations sharing a single communication channel are polled by a central station at a high speed to solicit responses therefrom. The central station can effectively handle responses from only one remote station at a time and, since a plurality of stations are polled, the possibility of contention between more than one remote station trying to respond during the same time period exists. If contention does occur, a second poll of possible contenders is conducted at a slow rate of speed to resolve the contention.

Claims

1. In a communication system having a central station and a plurality of remote, individually pollable stations which may communicate with said central station when polled thereby, the improved method of operating said system, comprising the steps of:

polling a plurality of said remote stations within a time period which is less than the time within which any of said plurality of stations can respond, thereby soliciting message inputs to said central station;

halting said polling upon the receipt by said central station of a response from any of said plurality of polled remote stations;

checking said response as received by said central station to determine whether conflicting responses from more than one said remote station exist during all or part of the time during which a receipt of a response from any of said stations is occurring; and

, when said conflicting responses occur, repolling said remote stations to eliminate conflicting responses after said responses have ceased by polling each said remote station and then pasuing after each polling for a length of time not less than the time in which any of said stations can respond to receive any response said polled station may have; and

resuming said polling step when said response has ceased.

2. The method of operating a communication system as described in claim 1, wherein:

said polling of a plurality of said remote stations is conducted at a first rate which exceeds the rate at which said remote stations can respond; and

said repolling of said stations is conducted at a second rate which is not greater than the rate at which said stations can respond.

3. The method of operating a communication system as described in claim 1, wherein:

said halting of said polling is performed immediately upon the start of receipt of any response at said central station, thereby reducing the number of stations which may have to be repolled by reducing the number of said stations polled initially.

4. The method of operating a communication system as described in claim 1, wherein:

said repolling step is performed only for said remote stations encompassed by a group beginning with the first said station polled which has had less than a defined minimum time period following polling in which to respond, and ending with the last said station polled at the time said halting step was begun.

5. The method of operating a communication system as described in claim 4, wherein said repolling group is further defined by steps comprising:

comparing the time between the polling of each said station and the receipt of any said response against a defined minimum time period; and

listing for possible repolling those said stations which have had not greater time than said defined minimum in which to respond.

6. The method of claim 5, wherein:

said minimum time period being that in which any said station can respond with a complete message.

7. The method of operating a communication system as defined in claim 5, wherein:

said comparing is accomplished by loading the polling signals sequentially as sent out by said central station into a storage device having N stages of storage, N being defined as equal to the time required for any station to respond divided by the polling rate, so that, when said storage is full, each ensuing poll signal entered will force out the earliest entered poll signal from said storage device so that its record of being polled will be destrOyed and it will not be repolled if repolling is done, the N stages of storage assurring that said record is not destroyed until a sufficient time has elapsed since polling to allow said station to respond.

8. In a communication system having a central station and a plurality of remote, individually pollable stations which may communicate with said central station when polled thereby, the improved apparatus for operating said system, comprising:

means for polling a plurality of said remote stations within a time period which is less than the time within which any of said plurality of stations can respond, thereby soliciting message inputs to said central station;

means for halting said polling upon the receipt by said central station of a response from any of said plurality of polled remote stations;

means for checking said response as received by said central station to determine whether conflicting responses from more than one said remote station exist during all or part of the time during which a receipt of a response from any of said stations is occurring;

means for repolling said remote stations when said conflicting responses occur to eliminate conflicting responses after said responses have ceased by polling each said remote station and then pausing after each polling for a length of time not less than the time in which any of said stations can respond to receive any response said polled station may have; and

means responsive to the end of reception of said response for resuming saidp polling.

9. A communications system apparatus as described in claim 8 wherein:

said polling means includes a control means for clocking said polling at a first rate which exceeds the rate at which said remote stations can respond; and

said repolling means includes a control means for clocking said repolling at a second rate which is not greater than the rate at which said stations can respond.

10. A communications system apparatus as described in claim 9, further comprising;

means responsive to and connected with said polling means, for listing for said repolling by said repolling means only said remote stations encompassed by a group beginning with the first said station polled which has had not greater than a defined minimum time period following polling in which to respond, and ending with the last said station polled at the time said halting step was begun.

11. A communications system apparatus as described in claim 10, wherein:

said listing means is connected to and responsive to said polling means to list said stations for repolling at said first controlled polling rate of said polling means; and

said listing means is adapted to remove said stations from said list in the order in which they were listed therein after a time delay at least equal to a defined minimum period within which any given said station which has been polled can respond.

12. A communications system apparatus as described in claim 11, further comprising:

detecting means connected to said halting means and to said remote stations for detecting the start of receipt of any response from said stations and, responsive to said receipt of a response, for signalling said halting means to halt immediately, thereby reducing the number of said stations which may have to be repolled by reducing the number of said stations polled initially.