Estimating bulk delay in a telephone system

Details Estimating bulk delay in a telephone system Estimating bulk delay in a telephone system

2005-08-09

2005-08-09

Tran, Sinh (Department: 2644)

Telephonic communications

Echo cancellation or suppression

Using digital signal processing

C455S067160

Reexamination Certificate

active

06928160

ABSTRACT:
A bulk delay estimating circuit matches time intervals representing a signal with time intervals representing an echo of the signal to identify the echo and estimate bulk delay. Bulk delay is estimated by computing (1, 2, . . . n) intervals representing the signal, computing (1, 2, . . . n) intervals representing an echo of the signal, computing absolute differences between corresponding intervals to produce n absolute differences, summing the n absolute differences, and providing an output indicating whether or not the sum is less than a predetermined amount. The intervals are determined by defining a plurality of numbered frames, comparing the energy of a signal during each frame with at least one threshold, storing the numbers of the frames in which the threshold is exceeded, and defining an interval as the period from one frame in which the threshold is exceeded to the next frame in which the threshold is exceeded. Bulk delay is estimated from the frame numbers of the signal, its echo, and the duration of a frame.

REFERENCES:
patent: 4582963 (1986-04-01), Danstrom
patent: 4764955 (1988-08-01), Galand et al.
patent: 6078567 (2000-06-01), Traill et al.
IEEE publication 0-7803-6293-Apr. 2000Implementation and Evaluation of a Real-Time Line Echo Bulk-Delay Estimator, Ramkumar and Tanrikulu, Apr., 2000; pp. 3650-3653.
On the Estimation of Bulk-Delay and Length of Dispersive Region in Echo Cancellation, Hau, Chan , and Liu; pp. 57-60.

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