# US 2017/0288932 A1 · Carrier frequency offset estimation in a receiver

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- Number: US 2017/0288932 A1
- Document ID: US20170288932A1
- Status: Published application
- Kind: A1
- Application number: 15/266,906
- Filed: 2016-09-15
- Published: 2017-10-05
- Earliest claimed: 2016-03-29
- Assignees: QUALCOMM Incorporated
- Applicants: QUALCOMM Incorporated
- Inventors: Eunmo Kang; Koorosh Akhavan; Le Nguyen Luong
- Web page: https://patentgrep.com/patent/US20170288932A1

## CPC

- H04L 1/0018: {based on latency requirement}
- H04L 27/0014: {Carrier regulation (of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657)}
- H04L 27/2082: {for offset or staggered quadrature phase shift keying}
- H04L 27/2657: {Carrier synchronisation}
- H04L 27/2698: {double density OFDM/OQAM system, e.g. OFDM/OQAM-IOTA system}
- H04L 27/2671: {Time domain}
- H04L 27/2675: {Pilot or known symbols}
- H04L 2027/003: {at baseband only}
- H04L 2027/0057: {quadrature phase}
- H04L 2027/0067: {Phase error detectors}
- H04W 4/70: Services for machine-to-machine communication [M2M] or machine type communication [MTC]
- Y02D 30/70: in wireless communication networks
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE

## Abstract

Systems and methods are directed to low cost and low power carrier frequency offset (CFO) estimation in a receiver. In-phase (I) and quadrature (Q) samples of a wireless signal are received by the receiver and a first phase and a second phase are extracted from the outputs of a first autocorrelator with a first time-lag and a second autocorrelator with a second time-lag. The extracted first and second phases are combined to generate an estimated CFO of high accuracy and wide estimation range.

## Claims

### Claim 1

A method for estimating carrier frequency offset (CFO) in a receiver, the method comprising:
performing a first autocorrelation of received wireless signals in a first autocorrelator with a first time-lag to generate a first autocorrelation signal, wherein the received wireless signals comprise in-phase (I) and quadrature (Q) samples;
extracting a first phase of the first autocorrelation signal in a first arctangent block;
performing a second autocorrelation of the received wireless signals in a second autocorrelator with a second time-lag to generate a second autocorrelation signal;
extracting a second phase of the second autocorrelation signal in a second arctangent block; and
combining the first phase and the second phase to generate an estimated CFO.

### Claim 2 (depends on 1)

The method of claim 1, wherein combining the first phase and the second comprises:
scaling the first phase;
computing a difference between the scaled first phase and the second phase;
scaling the difference;
adding the scaled difference to the first phase to generate a refined first phase; and
scaling the refined first phase to generate the estimated CFO.

### Claim 3 (depends on 2)

The method of claim 2, wherein scaling the first phase comprises magnifying the first phase wherein scaling the difference comprises shrinking the difference.

### Claim 4 (depends on 3)

The method of claim 3, wherein the second time-lag is four times the first time-lag, the magnifying is by a factor of four, and the shrinking is by a factor of four.

### Claim 5 (depends on 2)

The method of claim 2, further comprising combining the refined first phase with a third phase generated by a third autocorrelator with a third time-lag, to generate a combined CFO estimate.

### Claim 6 (depends on 5)

The method of claim 5, wherein the third time-lag is sixteen times the first time-lag and the second time-lag is four times the first time-lag.

### Claim 7

An apparatus comprising:
a receiver configured to receive a wireless signal comprising in-phase (I) and quadrature (Q) samples, the receiver further comprising:
a first autocorrelator with a first time-lag, configured to perform a first autocorrelation of the received wireless signals to generate a first autocorrelation signal;
a first arctangent block configured to extract a first phase of the first autocorrelation signal;
a second autocorrelator with a second time-lag configured to perform a second autocorrelation of the received wireless signals to generate a second autocorrelation signal;
a second arctangent block configured to extract a second phase of the second autocorrelation signal; and
a combination block configured to combine the first phase and the second phase to generate an estimated CFO.

### Claim 8 (depends on 7)

The apparatus of claim 7, wherein the combination block comprises:
a first multiplier configured to scale the first phase;
a first adder configured to compute a difference between the scaled first phase and the second phase;
a second multiplier configured to scale the difference;
a second adder configured to add the scaled difference to the first phase to generate a refined first phase; and
a multiplier configured to scale the refined first phase to generate the estimated CFO.

### Claim 9 (depends on 8)

The apparatus of claim 8, wherein the first multiplier is configured to magnify the first phase and the second multiplier is configured to shrink the difference.

### Claim 10 (depends on 9)

The apparatus of claim 9, wherein the second time-lag is four times the first time-lag, the first multiplier is configured to magnify by a factor of four, and the second multiplier is configured to shrink is by a factor of four.

### Claim 11 (depends on 8)

The apparatus of claim 8, further comprising a cascaded second stage comprising a third autocorrelator with a third time-lag to perform a third autocorrelation of the received wireless signals to generate a third autocorrelation signal and a third arctangent block to extract a third phase from the third autocorrelation signal, wherein the third phase is combined with the refined first phase to generate a combined CFO estimate.

### Claim 12 (depends on 11)

The apparatus of claim 11, wherein the third time-lag is sixteen times the first time-lag and the second time-lag is four times the first time-lag.

### Claim 13

An apparatus comprising:
means for performing a first autocorrelation of received wireless signals with a first time-lag, to generate a first autocorrelation signal, wherein the received wireless signals comprise in-phase (I) and quadrature (Q) samples;
means for extracting a first phase of the first autocorrelation signal;
means for performing a second autocorrelation of the received wireless signals with a second time-lag, to generate a second autocorrelation signal;
means for extracting a second phase of the second autocorrelation signal; and
means for combining the first phase and the second phase to generate an estimated CFO.

### Claim 14 (depends on 13)

The apparatus of claim 13, further comprising:
means for scaling the first phase;
means for computing a difference between the scaled first phase and the second phase;
means for scaling the difference;
means for adding the scaled difference to the first phase to generate a refined first phase; and
means for scaling the refined first phase to generate the estimated CFO.

### Claim 15 (depends on 14)

The apparatus of claim 14, wherein scaling the first phase comprises magnifying the first phase wherein scaling the difference comprises shrinking the difference.

### Claim 16 (depends on 15)

The apparatus of claim 15, wherein the second time-lag is four times the first time-lag, the magnifying is by a factor of four, and the shrinking is by a factor of four.

### Claim 17 (depends on 13)

The apparatus of claim 13, further comprising means for combining the refined first phase with a third phase generated with a third time-lag, to generate a combined CFO estimate.

### Claim 18 (depends on 17)

The apparatus of claim 17, wherein the third time-lag is sixteen times the first time-lag and the second time-lag is four times the first time-lag.

### Claim 19

A non-transitory computer readable storage medium comprising code, which, when executed by a processor, causes the processor to perform operations for estimating carrier frequency offset (CFO) of received wireless signals, the non-transitory computer readable storage medium comprising:
code for performing a first autocorrelation of the received wireless signals with a first time-lag, to generate a first autocorrelation signal, wherein the received wireless signals comprise in-phase (I) and quadrature (Q) samples;
code for extracting a first phase of the first autocorrelation signal;
code for performing a second autocorrelation of the received wireless signals with a second time-lag, to generate a second autocorrelation signal;
code for extracting a second phase of the second autocorrelation signal; and
code for combining the first phase and the second phase to generate an estimated CFO.

### Claim 20 (depends on 19)

The non-transitory computer readable storage medium of claim 19, wherein code for combining the first phase and the second comprises:
code for scaling the first phase;
code for computing a difference between the scaled first phase and the second phase;
code for scaling the difference;
code for adding the scaled difference to the first phase to generate a refined first phase; and
code for scaling the refined first phase to generate the estimated CFO.

### Claim 21 (depends on 20)

The non-transitory computer readable storage medium of claim 20, wherein code for scaling the first phase comprises code for magnifying the first phase wherein code for scaling the difference comprises code for shrinking the difference.

### Claim 22 (depends on 21)

The non-transitory computer readable storage medium of claim 21, wherein the second time-lag is four times the first time-lag, the magnifying is by a factor of four, and the shrinking is by a factor of four.

### Claim 23 (depends on 21)

The non-transitory computer readable storage medium of claim 21, further comprising code for combining the refined first phase with a third phase generated with a third time-lag, to generate a combined CFO estimate.

### Claim 24 (depends on 23)

The non-transitory computer readable storage medium of claim 23, wherein the third time-lag is sixteen times the first time-lag and the second time-lag is four times the first time-lag.