Method and apparatus for polling subscriber terminals

• US 4,689,619 A
• Filed: 12/26/1985
• Issued: 08/25/1987
• Est. Priority Date: 12/26/1985
• Status: Expired due to Term

• Current Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: O'Brien, Thomas E. Jr.
• Primary Examiner(s): Weldon, Ulysses
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/813,502
• Time in Patent Office: 607 Days
• Field of Search: 340/825.08, 340/825.52, 340/825.5, 370/85, 370/94, 358/84, 358/86, 358/139
• US Class Current: 340/10.2
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 12/403 with centralised control, e.g. polling
• CPC Class Codes: H04N 2007/17372 the upstream transmission being initiated or timed by a signal from upstream of the user terminal
• CPC Class Codes: H04N 7/17354 in an intermediate station common to a plurality of user terminals

Abstract

Subscriber terminals serviced by a plurality of remotely located two-way addressable cable television systems are polled using polling command signals addressed to the different terminals from a polling center. The polling command signals are sent to the subscriber terminals via their associated headends. Responses from the polled subscriber terminals are successively received at the polling center. The round trip signal propagation times required to communicate the polling command and response signals to and from each of the headends is equalized so that the response from the polled subscriber terminals are received in the same order in which the terminals are addressed by the polling command signals. A uniform delay is inserted after each successive polling command signal to allow for variations in the signal propagation times between the headends and individual subscriber terminals coupled thereto.

Claims

1. A method for polling subscriber terminals or the like in a two-way addressable communication network having a polling center and a plurality of remotely located communication centers coupled to terminals to be polled by the polling center comprising the steps of:

identifying the communication center in the network that has a round trip signal propgation time to the polling center which is greater than the round trip signal propagation time between the polling center and any other communication center in the network;

determining the magnitude of said greatest round trip signal propagation time;

delaying the round trip signal propagation times for signals travelling between each of the other communication centers and the polling center to match the magnitude of said greatest round trip signal propagation time, thereby providing a uniform round trip signal propagation time between the polling center and all of the communication centers;

successively sending a polling command signal from said polling center to each terminal to be polled via the communication center to which the terminal is coupled;

waiting for a time period equal to the magnitude of said greatest round trip signal propagation time after sending the first polling command signal of said succession;

successively receiving responses from each polled terminal, via the communication center to which the terminal is coupled, after completing said wait; and

identifying the responding terminals by the order in which their responses are received, said order being the same as that in which the successive polling command signals were sent.

2. The method of claim 1 comprising the further step of:

inserting a uniform delay after each successive polling command signal to allow for the maximum round trip signal propagation time between a communication center and a terminal coupled thereto.

3. Apparatus for polling subscriber terminals or the like in a two-way addressable communication network having a plurality of remotely located communication centers coupled to terminals to be polled comprising:

means for generating a succession of polling command signals each addressed to a different one of a plurality of terminals to be polled;

means for sending said polling command signals to the terminals to be polled via communication centers to which the terminals are coupled;

means for successively receiving a response signal from each polled terminal via the communication center to which the terminal is coupled, the amount of time it takes the polling command and response signals to be communicated to and from each communication center, respectively, establishing a round trip signal propagation time for each communication center; and

means for equalizing the round trip signal propagation times required to communicate the polling command and response signals to and from each of the communication centers;

whereby the responses from the polled terminals are received in the same order in which the terminals are addressed by the polling command signals.

4. The apparatus of claim 3 further comprising:

means for inserting a uniform delay after each successive polling command signal to allow for variations in the time it takes a signal to propagate between the communication centers and individual terminals coupled thereto.

5. Apparatus, for polling subscriber terminals serviced by a plurality of remotely located two-way addressable cable television systems, comprising:

means for generating a succession of polling command signals each addressed to a different one of a plurality of subscriber terminals to be polled;

means for sending said polling command signals to a plurality of cable television headends, each headend coupled to relay polling command signals to different ones of said subscriber terminals;

means for successively receiving a response signal from each polled subscriber terminal via its associated headend, the amount of time it takes the polling command and response signals to travel to and from each of the headends, respectively, establishing a round trip signal propagation time for each headend; and

means for equalizing the round trip signal propagation times required to communicate the polling command and response signals to and from each of the headends;

whereby the responses from the polled subscriber terminals are received in the same order in which the terminals are addressed by the polling command signals.

6. The apparatus of claim 5 further comprising:

means for inserting a uniform delay after each successive polling command signal to allow for variations in the time it takes a signal to propagate between the headends and individual subscriber terminals coupled thereto.

7. The apparatus of claim 6 wherein said sending and receiving means comprise a separate communication path to each of the headends and said equalizing means comprises programmable delay means provided in the communication paths for delaying signal propagation times in the paths by an amount necessary to render the round trip propagation time for each path equal.