Method and apparatus for estimating clock slew and carrier translation
AssigneeRacal-Datacom, Inc.
InventorsRaj M. Misra, Vedavalli G. Krishnan
Life of this patent
Estimating the term…
Abstract
The present invention helps derive accurate clock and carrier translation presets in the presence of noise and various line shapes. The invention provides an adaptive algorithm that optimizes the calculations of clock slew (.DELTA.T.sub.s) and frequency offset (.DELTA.f) over the specific line conditions encountered at each connection by choosing an optimal subset of the communication device's probing frequencies that minimizes the effect of line losses and noise.
Claims12
A method for estimating the clock slew between first and second data communication devices, the method comprising the steps of:
- at the second data communication device:
- (a) receiving a signal from the first data communication device;
- (b) dividing the signal into temporal windows;
- (c) organizing the temporal windows into a predetermined number of sets with each set including at least two of the temporal windows;
- (d) calculating a phase vector for each of the at least two temporal windows in each set;
- (e) determining the difference between the at least two phase vectors in each set in order to yield at least one vector (.phi.) for each set;
- (f) averaging the at least one vector (.phi.) determined in step (e) for each set in order to yield one averaged vector <.phi.>;
- (g) selecting two components (.phi..sub.1 (Q), .phi..sub.2 (Q) ) of the averaged vector <.phi.>
- which yield the maximum effective signal-to-noise ratio;
- and
- (h) using the two components determined in step (g) to determine the clock slew between the first and second data communication devices.
A method for estimating clock slew and frequency offset at a first modem from the line probing signal transmitted by a second modem, the method comprising the steps of:
- (a) receiving the line probing signal at the first modem;
- (b) dividing the line probing signal into at least two time periods;
- (c) calculating a phase vector for each of the at least two time periods;
- (d) determining the difference between the phase vectors in order to yield one vector (.phi.);
- (e) selecting two components (.phi..sub.1 (Q), .phi..sub.2 (Q) ) of the vector (.phi.) which yield the maximum effective signal-to-noise ratio;
- and
- (f) using the two components determined in step (e) to estimate the clock slew, .DELTA.T.sub.s, between the first and second modems.
A communication device which receives a signal from a remote device, the communication device comprising:
- an input port for receiving the signal;
- and
- a signal processor coupled to the input port and in response to the received signal estimates the clock slew between the communication device and the remote device by dividing the signal into at least two time periods, then calculates phase vectors for the at least two time periods, determines the difference between the phase vectors in order to yield one vector (.phi.), then selects two components (.phi..sub.1 (Q), .phi..sub.2 (Q)) of the vector (.phi.) which yield the maximum effective signal-to-noise ratio, and uses the two selected components to estimate the clock slew between the communication device and the remote device.
Dependencies are inferred from the claim text.