Technique for measuring channel delay

• US 5,280,629 A
• Filed: 12/06/1991
• Issued: 01/18/1994
• Est. Priority Date: 12/06/1991
• Status: Expired due to Term

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Hiben, Bradley M., Cudak, Mark C., Lo Galbo, Robert D.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): FAILE, ANDREW I
• Application Number:
  US07/804,860
• Time in Patent Office: 774 Days
• Field of Search: 455/11.1, 455/12.1, 455/13.2, 455/51.2, 455/57.1, 455/59, 455/67.4, 455/67.6, 455/69-70, 375/10, 375/110, 379/63
• US Class Current: 455/503
• CPC Class Codes: H04B 17/364 Delay profiles
• CPC Class Codes: H04H 20/67 Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging

Abstract

A method for measuring channel delay measures the delay for a message to propagate from a prime site (100, 400) to a remote site (200, 500) via the channel (300, 600). The prime site includes a clock for providing a first value, T1, based on the current time at the prime site. The remote site includes a clock for providing a second value, T2, based on the current time at the remote site. Both clocks are synchronized with a common timing source, such as a GPS satellite timing signal. Therefore, T2 equals T1. In one embodiment, the prime site determines T1, and simultaneously sends a message to the remote site via the channel, the message including T1. Upon receiving the message, the remote site simultaneously determines T2. The remote site decodes the message to determine T1, and then determines the delay based on the difference between T2 and T1.

Claims

1. In a simulcast system having a prime transmitter site coupled to a remote transmitter site via a channel, the channel having a delay, the prime transmitter site having a prime clock for providing a first value ("T1") based on the current time at the prime transmitter site, the remote transmitter site having a remote clock for providing a second value ("T2") based on the current time at the remote transmitter site, the prime clock and the remote clock being synchronized with a common timing signal so that T2 equals T1, the simulcast system arranged for determining the worst-case delay in accordance with a predetermined method, the method comprising the steps of:

at the prime transmitter site;

(a) determining T1;

(b) simultaneous with step (a), sending a first message to the remote transmitter site;

(c) saving T1;

at the remote transmitter site;

(d) receiving the first message;

(e) simultaneous with step (d), determining T2;

(f) sending a second message to the prime transmitter site, the second message including T2;

at the prime transmitter site;

(g) receiving the second message;

(h) decoding the second message to determine T2;

(i) determining the delay based on the difference between T2 and T1;

(j) repeating steps (a) through (i) z times, thereby determining delay₁, . . . , delay_z ;

(k) determining the worst-case delay for the channel based on the maximum delay of the group of delays consisting of delay₁, . . . , delay_z ;

(l) waiting a predetermined time, and then repeating steps (a) through (k);

(m) after step (l), then repeating steps (a) through (l) for a predetermined number

(w) of times, thus determining the worst-case delay for the 1st trial, the worst-case delay for the 2nd trial, . . . , the worst-case delay for the (w-1)th trial, and the worst-case delay for the wth trial;

where z is a predetermined number greater than 1, the predetermined number z being selected to determine the worst-case delay.

2. In the simulcast system of claim 1, the method further including the following prime transmitter step:

(n) determining whether the worst-case delay for the wth trial is greater than any member of the group consisting of the worst-case delay for the 1st trial, the worst-case delay for the 2nd trial, . . . , and the worst-case delay for the (w-1)th trial.

3. In the simulcast system of claim 2, the method further including the following prime transmitter step:

(o) when the worst-case delay for the wth trial is greater than any member of the group consisting of the worst-case delay for the 1st trial, the worst-case delay for the 2nd trial, . . . , and the worst-case delay for the (w-1)th trial, then determining the maximum value of the group consisting of the worst-case delay for the 1st trial, the worst-case delay for the 2nd trial, . . . , and the worst-case delay for the (w-1)th trial.

4. In the simulcast system of claim 3, the method further including the following prime transmitter step:

(p) determining the difference between the worst-case delay for the wth trial and the maximum value of the group consisting of the worst-case delay for the 1st trial, the worst-case delay for the 2nd trial, . . . , and the worst-case delay for the (w-1)th trial.

5. In the simulcast system of claim 4, the method further including the following prime transmitter step:

(q) adjusting the simulcast broadcast time by the difference between the worst-case delay for the wth trial and the maximum value of the group consisting of the worst-case delay for the 1st trial, the worst-case delay for the 2nd trial, . . . , and the worst-case delay for the (w-1)th trial.