1. A radio transceiver comprising:
at least one antenna;
a receiver section having a quadrature demodulator for receiving various signals and converting the various signals into in-phase and quadrature phase signals;
a transmitter section for transmitting at least one known signal to an input of the quadrature demodulator for conversion by the quadrature demodulator;
a switching unit configurable for providing an amount of isolation between an output port of the transmitter section and an input port of the receiver section such that when the at least one known signal is present at the output port at a first power level, the at least one known signal is also present at the input port at a second power level lower than the first power level and is converted by the quadrature demodulator;
at least one receiver compensation factor estimation unit coupled to an output of the quadrature demodulator for estimating, after conversion of the at least one known signal into in-phase and quadrature phase signals, at least one receiver compensation factor for compensating the receiver section for an imbalance in subsequently received in-phase and quadrature phase signals; and
one or more compensation components that perform a compensation protocol wherein the protocol includes: communicate information regarding calibration imbalance with another transceiver to perform compensation; estimating an I-Q imbalance compensation at the receiver, communicating the estimated receiver I-Q imbalance to the transmitter, computing at the transmitter compensation factors for the transmitter as a function of the estimated receiver I-Q imbalance.
2. The radio transceiver recited in claim 1, wherein the receiver section further comprises a receiver I-Q compensation unit coupled to the at least one receiver compensation factor estimation unit for applying the at least one receiver compensation factor to subsequent in-phase and quadrature phase signals.
3. The radio transceiver recited in claim 1, wherein the receiver section further comprises a receiver memory coupled to the at least one receiver compensation factor estimation unit and a receiver I-Q compensation unit for storing the at least one receiver compensation factor and for providing the at least one receiver compensation factor to the receiver I-Q compensation unit.
4. The radio transceiver recited in claim 2, wherein the receiver I-Q compensation unit determines the receiver compensation factors using tan \u03c6r and (yrcos\u03c6r)\u22121, where yr is a value of amplitude imbalance and \u03c6r is a value of phase imbalance.
5. The radio transceiver recited in claim 2, wherein the receiver I-Q compensation unit determines the receiver compensation factors using yrsin\u03c6r and (yrcos\u03c6r)\u22121, where yr is a value of amplitude imbalance and \u03c6r is a value of phase imbalance.
6. The radio transceiver recited in claim 1, wherein the at least one receiver compensation factor estimation unit estimates an amplitude imbalance (yr) according to the equation
y
r
\u2248
1
–
E
R
\u2062
\u2062
1
1
+
E
R
\u2062
\u2062
1
,
and derivatives thereof, where
E
R
\u2062
\u2062
1
=
1
–
y
r
2
1
+
2
\u2062
y
r
\u2062
cos
\u2062
\u2062
\u03d5
r
+
y
r
2
.
7. The radio transceiver recited in claim 6, wherein the at least one receiver compensation factor estimation unit estimates a phase imbalance (\u03c6r) according to the equation
\u03d5
r
\u2248
–
E
I
\u2062
\u2062
1
\u2062
\u2062
(
1
+
y
r
)
2
2
\u2062
y
r
,
and derivatives thereof, where
E
I
\u2062
\u2062
1
=
–
2
\u2062
y
r
\u2062
sin
\u2062
\u2062
\u03d5
r
1
+
2
\u2062
y
r
\u2062
cos
\u2062
\u2062
\u03d5
r
+
y
r
2
.
8. The radio transceiver recited in claim 1, wherein the at least one receiver compensation factor estimation unit estimates an amplitude imbalance (yr) according to the equation
y
r
\u2248
1
–
E
R
\u2062
\u2062
2
1
+
E
R
\u2062
\u2062
2
,
and derivatives thereof, where
E
R
\u2062
\u2062
2
=
1
–
y
r
2
1
+
y
r
2
.
9. The radio transceiver recited in claim 8, wherein the at least one receiver compensation factor estimation unit estimates a phase imbalance (\u03c6r) according to the equation
\u03d5
r
\u2248
–
E
I
\u2062
\u2062
2
\u2062
1
+
y
r
2
2
\u2062
y
r
,
and derivatives thereof, where
E
I
\u2062
\u2062
2
=
–
2
\u2062
y
r
\u2062
sin
\u2062
\u2062
\u03d5
r
1
+
y
r
2
.
10. The transceiver of claim 1, further comprising a transmitter compensating component that receives, as an input, an estimated I-Q imbalance transmitted from a receiver compensation component.
11. The transceiver of claim 1, wherein the compensation protocol includes:
estimating a compensation factor for a receiver or a transmitter;
applying the compensation factor to a received or transmitted signal.
12. The transceiver of claim 1, wherein the compensation protocol includes:
calibrating a receiver including determination of a receiver compensation factor;
transmitting a test signal through a transmitter, back to the receiver;
removing receiver imbalance as a function of the test signal and the receiver compensation factor;
estimating a transmitter compensation factor; and
removing transmitter imbalance from transmitter signals as a function of the transmitter compensation factor.
13. The transceiver of claim 12, wherein the receiver compensation factor is estimated at the receiver.
14. The transceiver of claim 12, wherein the transmitter compensation factor is estimated at the transmitter.
15. The transceiver of claim 1, wherein the compensation protocol comprises receiver imbalance calibration followed by transmitter imbalance calibration.
16. The transceiver of claim 1, wherein the compensation protocol comprises transmitter imbalance calibration followed by receiver imbalance calibration.
17. In a communication system comprising at least a first transmitter and a first receiver having a quadrature demodulator for receiving various signals and converting the various signals into in-phase and quadrature phase signals, a method for compensating for I-Q the in-phase and quadrature phase signals, the method comprising:
transmitting from the first transmitter to the first receiver a data packet having at least one known signal for conversion by the quadrature demodulator;
estimating, after conversion by the quadrature demodulator of the at least one known signal into in-phase and quadrature phase signals, at least one compensation factor for compensating for an imbalance in the in-phase and quadrature phase signals;
using the at least one compensation factor to compensate for an imbalance in in-phase and quadrature phase signals in a second transmitter located locally with the first receiver; and
executing a communication protocol including exchange of messages between the first transmitter and the first receiver, wherein the messages include information used to calibrate one or both of the transmitter and receiver.
18. The method recited in claim 17, wherein the data packet further includes at least one of a preamble portion, a midamble portion and a postamble portion for including the at least one known signal.
19. The method recited in claim 17, wherein the at least one known signal is included in a preamble portion of the data packet such that after estimation of the at least one compensation factor, the at least one compensation factor is immediately applied to the data portion.
20. The method recited in claim 17, wherein the at least one known signal is included in at least one of the midamble portion and the postamble portion such that the data portion is first stored in a buffer before estimation of the at least one compensation factor.
21. The method recited in claim 20, wherein after estimation of the at least one compensation factor, the at least one compensation factor is applied to the data portion.
22. The method recited in claim 17, wherein the at least one compensation factor is used to compensate for an imbalance in in-phase and quadrature phase signals in at least one of the first receiver and the first transmitter.
23. The method recited in claim 17, wherein the communication system further comprises a second receiver located locally with the first transmitter and wherein the method further comprises transmitting from the second transmitter to the second receiver a return message including the at least one compensation factor.
24. The method recited in claim 23, wherein the at least one compensation factor is used to compensate for an imbalance in in-phase and quadrature phase signals in the first transmitter.
25. The method recited in claim 23, wherein the at least one compensation factor is used to compensate for an imbalance in in-phase and quadrature phase signals in the second receiver.
26. The method recited in claim 17, wherein the at least one known signal is further used to perform automatic gain control, automatic frequency control and phase recovery.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of computing a measure of quality for a distorted image Y, the measure characterizing a similarity between the image Y and an undistorted reference image X having the same number of rows and columns of pixels as the image Y, the method comprising:
employing at least one processor for:
(a) transforming the distorted image Y and the undistorted reference image X by a transformation process to generate a transform of the distorted image Y and a transform of the undistorted reference image X respectively, the transformation process having a blindness property of not containing all information regarding an image to be transformed in a transform of the image, thus resulting in certain patterns of the image not to be recognized during the transformation process;
(b) spatially shifting pixels in the reference image X and the distorted image Y by a spatial shift, having the same predefined amount of pixels, to generate a spatially shifted version X2 of the reference image X and a spatially shifted version Y2 of the image Y respectively, the spatial shift being chosen so that the certain patterns become detectable during the transformation process applied to the spatially shifted versions X2 and Y2;
(c) transforming the spatially shifted version Y2 and the spatially shifted version X2 by the transformation process to generate a transform of the spatially shifted version Y2 and a transform of the spatially shifted version X2 respectively; and
(d) determining the measure of quality for the distorted image Y as a function of the transform of the distorted image Y, the transform of the undistorted reference image X, the transform of the spatially shifted version Y2, and the transform of the spatially shifted version X2.
2. The method of claim 1, wherein the step (b) further comprises:
dividing the pixels of the reference image X into blocks of W by W pixels; and
dividing the pixels of the distorted image Y into corresponding blocks of W by W pixels;
W being a smaller number than the number of rows and columns of pixels.
3. The method of claim 1, wherein the step (b) further comprises:
spatially shifting horizontally by a first predefined amount; or
spatially shifting vertically by a second predefined amount; or
spatially shifting horizontally and vertically by first and second predefined amounts respectively.
4. The method of claim 3, wherein the first predefined amount and the second predefined amount are the same.
5. The method of claim 2, wherein the W is equal to 2\u0302N, wherein an exponent N is a decomposition level of the transformation process.
6. The method of claim 3, wherein each of the first and second predefined amounts are the larger of 1 and (W2\u22121).
7. The method of claim 3, wherein the first and second predefined amounts are odd numbers less than W.
8. The method of claim 1, wherein the transformation process is one of the following:
a cosine transform;
a sine transform;
a wavelet transform.
9. The method of claim 1, wherein the transformation process is a Haar transform or a Daubechies transform.
10. The method of claim 1, wherein the step (d) further comprises:
computing a first approximation image quality metric IQMA using the transform of the distorted image Y and the transform of the undistorted reference image X;
computing a second approximation image quality metric IQM\u2032A using the transform of the spatially shifted version Y2 and the transform of the spatially shifted version X2; and
processing the first and second approximation image quality metrics IQMA and IQM\u2032A to generate the measure of quality for the distorted image Y.
11. The method of claim 10, wherein the first and second approximation quality metrics IQMA and IQM\u2032A respectively are first and second approximation quality maps, and the step (d) further comprises:
creating first and second contrast maps of the reference image X and of the spatially shifted version X2 respectively;
performing weighted pooling of the first and second approximation quality maps using the first and second contrast maps respectively to produce an approximation quality score SA; and
determining the measure of quality using the approximation quality score SA.
12. The method of claim 10, wherein the step (d) further comprises:
(i) computing a first edge image quality metric IQME using the transform of the distorted image Y and the transform of the undistorted reference image X;
(ii) computing a second edge image quality metric IQM\u2032E using the transform of the spatially shifted version Y2 and the transform of the spatially shifted version X2; and
(iii) determining the measure of quality for the distorted image Y as the function of IQMA, IQM\u2032A, IQME and IQM\u2032E.
13. The method of claim 12, wherein the step (iii) further comprises:
processing the first and second approximation image quality metrics IQMA and IQM\u2032A to generate an approximation quality score SA;
processing the first and second edge quality metrics IQME and IQM\u2032E to generate an edge quality score SE; and
determining the measure of quality for the distorted image Y as a function of the approximation quality score SA and the edge quality score SE.
14. The method of claim 13, wherein the measure of quality is computed as a final score SF=a*SA+(1\u2212a)*SE, with SF value ranging from 0 to 1.
15. The method of claim 12, wherein the first and second approximation quality metrics IQMA and IQM\u2032A respectively are first and second approximation quality maps, wherein further the first and second edge quality metrics IQME and IQM\u2032E respectively are first and second edge quality maps, and the step (d) further comprises:
(d1) creating first and second contrast maps of the reference image X and of the spatially shifted version X2 respectively;
(d2) performing weighted pooling of the first and second approximation quality maps using the first and second contrast maps respectively to produce an approximation quality score SA;
(d3) performing weighted pooling of the first and second edge quality maps using the first and second contrast maps respectively to produce an edge quality score SE; and
(d4) processing the approximation quality score SA and the edge quality score SE to determine the measure of quality.
16. The method of claim 15, the step of creating first and second contrast maps further comprises assigning values to pixels of the first and second approximation quality maps, and the first and second edge maps of the reference image X and the spatially shifted version X2 according to their respective importance to a human visual system.
17. The method of claim 15, wherein the step (d2) further comprises one of averaging the first approximation quality map and the second approximation quality map, and of taking the minimum of the first approximation quality map and the second approximation quality map to produce the approximation quality score SA.
18. A system for computing a measure of quality for a distorted image Y, the measure characterizing a similarity between the image Y and an undistorted reference image X having the same number of rows and columns of pixels as the image Y, the system comprising:
a processor;
a non-transitory computer readable storage medium having computer readable instructions stored thereon for execution by the processor, causing the processor to:
(a) transform the distorted image Y and the undistorted reference image X by a transformation process to generate a transform of the distorted image Y and a transform of the undistorted reference image X respectively, the transformation process having a blindness property of not containing all information regarding an image to be transformed in a transform of the image, thus resulting in certain patterns of the image not to be recognized during the transformation process;
(b) spatially shift pixels in the reference image X and the distorted image Y by a spatial shift, having the same predefined amount of pixels, to generate a spatially shifted version X2 of the reference image X and a spatially shifted version Y2 of the image Y respectively, the spatial shift being chosen so that the certain patterns become detectable during the transformation process applied to the spatially shifted versions X2 and Y2;
(c) transform the spatially shifted version Y2 and the spatially shifted version X2 by the transformation process to generate a transform of the spatially shifted version Y2 and a transform of the spatially shifted version X2 respectively; and
(d) determine the measure of quality for the distorted image Y as a function of the transform of the distorted image Y, the transform of the undistorted reference image X, the transform of the spatially shifted version Y2, and the transform of the spatially shifted version X2.
19. The system of claim 18, wherein the computer readable instructions further cause the processor to:
divide the pixels of the reference image X into blocks of W by W pixels, W being a smaller number than the number of rows and columns of pixels; and
divide the pixels of the distorted image Y into corresponding blocks of W by W pixels.
20. The system of claim 18, wherein the computer readable instructions further cause the processor to:
spatially shift horizontally by a first predefined amount; or
spatially shift vertically by a second predefined amount; or
spatially shift horizontally and vertically by first and second predefined amounts respectively.
21. The system of claim 20, wherein the first predefined amount and the second predefined amount are the same.
22. The system of claim 18, wherein the W is equal to 2\u0302N, wherein an exponent N is a decomposition level of the transformation process.
23. The system of claim 20, wherein each of the first and second predefined amounts are the larger of 1 and (W2\u22121).
24. The system of claim 20, wherein the first and second predefined amounts are odd numbers less than W.
25. The system of claim 18, wherein the transformation process is one of the following:
a cosine transform;
a sine transform;
a wavelet transform.
26. The system of claim 18, wherein the transformation process is a Haar transform or a Daubechies transform.
27. The system of claim 18, wherein the computer readable instructions further cause the processor to:
compute a first approximation image quality metric IQMA using the transform of the distorted image Y and the transform of the undistorted reference image X;
compute a second approximation image quality metric IQM\u2032A using the transform of the spatially shifted version Y2 and the transform of the spatially shifted version X2; and
process the first and second approximation image quality metrics IQMA and IQM\u2032A to generate the measure of quality for the distorted image Y.
28. The system of claim 27, wherein the first and second approximation quality metrics IQMA and IQM\u2032A respectively are first and second approximation quality maps, and wherein the computer readable instructions further cause the processor to:
create first and second contrast maps of the reference image X and of the spatially shifted version X2 respectively;
perform weighted pooling of the first and second approximation quality maps using the first and second contrast maps respectively to produce an approximation quality score SA; and
determine the measure of quality using the approximation quality score SA.
29. The system of claim 27, wherein the computer readable instructions further cause the processor to:
(i) compute a first edge image quality metric IQME using the transform of the distorted image Y and the transform of the undistorted reference image X;
(ii) compute a second edge image quality metric IQM\u2032E using the transform of the spatially shifted version Y2 and the transform of the spatially shifted version X2; and
(iii) determine the measure of quality for the distorted image Y as the function of IQMA, IQM\u2032A, IQME and IQM\u2032E.
30. The system of claim 29, wherein the computer readable instructions further cause the processor to:
process the first and second approximation image quality metrics IQMA and IQM\u2032A to generate an approximation quality score SA;
process the first and second edge quality metrics IQME and IQM\u2032E to generate an edge quality score SE; and
determine the measure of quality for the distorted image Y as a function of the approximation quality score SA and the edge quality score SE.
31. The system of claim 13, wherein the measure of quality is computed as a final score SF=a*SA+(1\u2212a)*SE, with SF value ranging from 0 to 1.
32. The system of claim 29, wherein the first and second approximation quality metrics IQMA and IQM\u2032A respectively are first and second approximation quality maps, wherein further the first and second edge quality metrics IQME and IQM\u2032E respectively are first and second edge quality maps, and wherein the computer readable instructions further cause the processor to:
create first and second contrast maps of the reference image X and of the spatially shifted version X2 respectively;
perform weighted pooling of the first and second approximation quality maps using the first and second contrast maps respectively to produce an approximation quality score SA;
perform weighted pooling of the first and second edge quality maps using the first and second contrast maps respectively to produce an edge quality score SE; and
process the approximation quality score SA and the edge quality score SE to determine the measure of quality.
33. The system of claim 32, wherein the computer readable instructions further cause the processor to assign values to pixels of the first and second approximation quality maps, and the first and second edge maps of the reference image X and the spatially shifted version X2 according to their respective importance to a human visual system.
34. The system of claim 32, wherein the computer readable instructions further cause the processor to perform one of averaging the first approximation quality map and the second approximation quality map, and of taking the minimum of the first approximation quality map and the second approximation quality map to produce the approximation quality score SA.