Patent ID: 8599986
Filing Date: 2013-12-03
Classification: H03L,H04J

Abstract:
1. A method of recovering timing information over a packet network at a local receiver, comprising: receiving at intervals timing information about a remote source clock signal; generating a local clock signal with a controlled oscillator; comparing the local timing signal with the received timing information to generate noisy input signal y(k) representative of the phase difference between the source clock signal and the local receiver clock signal; applying said input signal y(k) to a state feedback controller to generate a control signal with reduced noise; and controlling said controlled oscillator with said control signal to reduce said phase difference and generate a slave clock signal from said remote clock signal; wherein an adaptive state estimator computes estimated internal states of said feedback controller, said internal states respectively representing phase and frequency offset, and wherein said control signal is derived from a combination of said computed internal states, said adaptive state estimator being a Kalman filter wherein the state space description of said Kalman filter is given by where y(n) is the measured transit time given of timing signals through the network, F n-1 is the state transition matrix, x n is the timing recovery system state vector, H n is the measurement matrix, G n is the input matrix, u n is an input, v n represents the amount of network jitter, w n is the variance vector of the process noise.