US 9,912,511 B2 · Systems and methods for time synchronization between transmitters and receivers in a communication system

Abstract

Systems and methods which provide training sequence or preamble-based synchronization with respect to non-coherent modulated signals and/or differentially coherent modulated signals are described. Embodiments provide for time synchronization using a technique for mitigating the effect of carrier frequency offset (CFO) with respect to the received signal. Embodiments of the present invention provide for frequency synchronization using a technique for estimating CFO using a constant bias induced with respect to the received signal by CFO. Additionally or alternatively, embodiments of the present invention provide for frequency synchronization using a technique for estimating CFO using phase rotation caused by CFO. The time synchronization and frequency synchronization of embodiments may be performed independently, without requiring the results of one synchronization operation for performing the other synchronization operation.

Claims20

Dependent claims

A method for time synchronization of packet-based communications, the method comprising:

calculating a second-order differential of a received training sequence signal, wherein the training sequence is non-coherently modulated or differentially coherently modulated;
calculating a cross-correlation between a second-order differential vector provided by the second-order differential calculation and a vector derived from a known training sequence instance corresponding to the received training sequence, wherein the calculating the cross-correlation comprises calculating the cross-correlation along a moving window, wherein the peak provided by the cross-correlation comprises a peak identified within the moving window, wherein the second-order differential vector is represented by D(k)=[{circumflex over (d)}(k−NM−1), {circumflex over (d)}(k−NM−2), . . . {circumflex over (d)}(k)], the vector derived from the known training sequence is represented by C=[c(0), c(1), . . . c(NM−1)], c(i)ε{+1,−1}, and the moving window in which the cross-correlation is performed is represented by [−M−1, M−1], and wherein the cross-correlation is performed as
R
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C
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k
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1
k
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d
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r
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c
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,
wherein N is a number of training sequence symbols, M is a number of sampling points per bit, k and r are indices, and c is a training sequence value;
and
determining the time synchronization based upon a peak provided by the cross-correlation.

40 more elements

A method for time synchronization of packet-based communications, the method comprising:

calculating a second-order differential of a received training sequence signal, wherein the training sequence is non-coherently modulated or differentially coherently modulated;
calculating a cross-correlation between a second-order differential vector provided by the second-order differential calculation and a vector derived from a known training sequence instance corresponding to the received training sequence, wherein the calculating the cross-correlation comprises:
establishing an index for a moving window cross-correlation;
calculating the cross-correlation of the second-order differential vector and the vector derived from the known training sequence instance for a current index point of the moving window;
comparing the cross-correlation for the current moving window index point with a stored moving window peak correlation value;
determining whether the stored moving window peak is smaller than the cross-correlation for the current index point in the moving window and, if the stored moving window peak is smaller, replacing the stored moving window peak with the cross-correlation for the current index point;
incrementing the moving window index;
and
repeating the calculating the cross-correlation, the comparing the cross-correlation, and the determining whether the stored moving window peak is smaller until an end of the moving widow is reached;
and
determining the time synchronization based upon a peak provided by the cross-correlation.

8 more elements

A system for time synchronization of packet-based communications, the system comprising:

a differentiator circuit operable to calculate a second-order differential of a received training sequence signal, wherein the training sequence is non-coherently modulated or differentially coherently modulated;
a cross-correlator circuit coupled to an output of the differentiator circuit and operable to calculate a cross-correlation between a second-order differential vector provided by the second-order differential calculation circuit and a vector derived from a known training sequence instance corresponding to the received training sequence and to identify a peak provided by the cross-correlation for use in determining the time synchronization, wherein the cross-correlator circuit is operable to calculate the cross-correlation along a moving window, wherein the peak provided by the cross-correlation comprises a peak identified within the moving window, wherein the second-order differential vector is represented by D(k)=[{circumflex over (d)}(k−NM−1), {circumflex over (d)}(k−NM−2), . . . {circumflex over (d)}(k)], the vector derived from the known training sequence is represented by C=[c(0), c(1), . . . c(NM−1)], c(i)ε{+1,−1}, and the moving window in which the cross-correlation is performed is represented by [−M−1, M−1], and wherein the cross-correlation performed by the cross-correlator circuit is performed in accordance with
R
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(
k
)
=
D
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k
)
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C
=
∑
r
=
k
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NM
-
1
k
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d
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(
r
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c
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r
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,
wherein N is a number of training sequence symbols, M is a number of sampling points per bit, k and r are indices, and c is a training sequence value.

38 more elements

A system for time synchronization of packet-based communications, the system comprising:

a differentiator circuit operable to calculate a second-order differential of a received training sequence signal, wherein the training sequence is non-coherently modulated or differentially coherently modulated;
a cross-correlator circuit coupled to an output of the differentiator circuit and operable to calculate a cross-correlation between a second-order differential vector provided by the second-order differential calculation circuit and a vector derived from a known training sequence instance corresponding to the received training sequence and to identify a peak provided by the cross-correlation for use in determining the time synchronization, wherein the cross-correlator circuit is operable to establish an index for a moving window cross-correlation, calculate the cross-correlation of the second-order differential vector and the vector derived from the known training sequence instance for a current index point of the moving window, compare the cross-correlation for the current moving window index point with a stored moving window peak correlation value, determine whether the stored moving window peak is smaller than the cross-correlation for the current index point in the moving window and, if the stored moving window peak is smaller, replace the stored moving window peak with the cross-correlation for the current index point, increment the moving window index, and repeat calculating the cross-correlation, comparing the cross-correlation, and determining whether the stored moving window peak is smaller until an end of the moving window is reached.

A method for time synchronization of packet-based communications, the method comprising:

calculating a second-order differential of a received training sequence signal, wherein the training sequence is either frequency shift key (FSK) modulated or differential phase shift key (DPSK) modulated;
calculating a cross-correlation, along a moving window, between a second-order differential vector provided by the second-order differential calculation and a vector derived from a known training sequence instance corresponding to the received training sequence, wherein the calculating the cross-correlation comprises:
establishing an index for a moving window cross-correlation;
calculating the cross-correlation of the second-order differential vector and the vector derived from the known training sequence instance for a current index point of the moving window;
comparing the cross-correlation for the current moving window index point with a stored moving window peak correlation value;
determining whether the stored moving window peak is smaller than the cross-correlation for the current index point in the moving window and, if the stored moving window peak is smaller, replacing the stored moving window peak with the cross-correlation for the current index point;
incrementing the moving window index;
and
repeating the calculating the cross-correlation, the comparing the cross-correlation, and the determining whether the stored moving window peak is smaller until an end of the moving window is reached;
and
determining the time synchronization based upon a peak provided by the cross-correlation, wherein the peak provided by the cross-correlation comprises a peak identified within the moving window.

8 more elements

Dependencies are inferred from the claim text.

Systems and methods for time synchronization between transmitters and receivers in a communication system

Life of this patent

Systems and methods for time synchronization between transmitters and receivers in a communication system

Life of this patent

Abstract

Claims20