Correction of signal-to-interference ratio measurements
First Claim
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1. In a communications system, a method comprising the steps of:
- receiving a signal transmitted over a communications channel;
measuring an estimate of an energy value and an interference value of the received signal;
determining a measured signal-to-interference ratio (SIR) value using the measured energy value and the measured interference value;
determining that the measured SIR value exceeds an SIR saturation threshold; and
thereafter, correcting the measured SIR value for nonlinearity to obtain a corrected SIR value.
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Abstract
Using measured estimates of received signal energy and interference values, a measured signal-to-interference ratio (SIR) value is determined. The measured SIR value is corrected for non-linearity to obtain a corrected SIR value using a correction function. That corrected SIR value may then be used in any number of applications such as to control the transmit power of mobiles in a mobile radio communications system.
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Citations
27 Claims
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1. In a communications system, a method comprising the steps of:
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receiving a signal transmitted over a communications channel;
measuring an estimate of an energy value and an interference value of the received signal;
determining a measured signal-to-interference ratio (SIR) value using the measured energy value and the measured interference value;
determining that the measured SIR value exceeds an SIR saturation threshold; and
thereafter,correcting the measured SIR value for nonlinearity to obtain a corrected SIR value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
providing a correction function that includes a linear part and a nonlinear part such that the measured SIR value is corrected for nonlinearity using the correction function.
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3. The method in claim 2, wherein the nonlinear part of the correction function is an inverse of an approximate exponential function that approximates a non-linear portion of a curve corresponding to measured SIR values.
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4. The method in claim 2, wherein the nonlinear part of the correction function is based on a logarithmic function and includes parameters selected to minimize error between the corrected SIR value and a corresponding actual SIR value.
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5. The method in claim 2, wherein the linear part includes a first linear component and a second linear component.
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6. The method in claim 2, wherein the correction function is defined by the following:
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where y1(x) is the corrected SIR value, x is the measured SIR value in dB units, T is an SIR threshold, and K, D, C0-C2 are coefficients.
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7. The method in claim 6, wherein K, D, and C0-C2 are selected to minimize error between the corrected SIR value and a corresponding actual SIR value.
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8. The method in claim 6, wherein the communications system is a spread spectrum radio communications system and the coefficients C0-C2 are determined based on a spreading factor used to spread information to be transmitted over an available frequency spectrum.
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9. The method in claim 2, wherein the correction function is defined by the following:
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where y2(x) is the corrected SIR value, x is the measured SIR value in dB units, T0 and T1 are SIR thresholds, K0, K1, D0, D1, and C0, C1, and C2 are coefficients.
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10. The method in claim 9, wherein the constants and coefficients are selected to minimize error between the corrected SIR value and a corresponding actual SIR value.
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11. The method in claim 10, wherein the communications system is a spread spectrum radio communications system and the constants and coefficients are determined as a function a spreading factor used to spread information to be transmitted over an available frequency spectrum.
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12. A method of processing in a receiver a signal comprised of a group of spread spectrum call signals sharing a common frequency band, comprising:
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analyzing one of the call signals from among the group and determining an associated signal energy value and an interference value;
determining a measured signal to interference ratio (SIR) value using the measured signal energy and interference values;
setting a first SIR threshold;
if the measured SIR value is less than or equal to the first SIR threshold, correcting the measured SIR value in a first fashion; and
if the measured SIR value is greater than the first SIR threshold, correcting the measured SIR value in a second fashion. - View Dependent Claims (20)
controlling a power level of the one call signal using the corrected SIR value.
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13. A method of processing in a receiver a signal comprised of a group of spread spectrum call signals sharing a common frequency band, comprising:
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analyzing one of the call signals from among the group and determining an associated signal energy value and an interference value;
determining a measured signal to interference ratio (SIR) value using the measured signal energy and interference values;
setting a first SIR threshold;
if the measured SIR value is less than or equal to the first SIR threshold, processing the measured SIR value in a first fashion;
if the measured SIR value is greater than the first SIR threshold, processing the measured SIR value in a second fashion; and
providing a correction function defining a first relationship between actual SIR values and measured SIR values less than or equal to the first SIR threshold and a second relationship between actual SIR values and measured SIR values greater than the first SIR threshold. - View Dependent Claims (14, 15)
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16. A method of processing in a receiver a signal comprised of a group of spread spectrum call signals sharing a common frequency band, comprising:
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analyzing one of the call signals from among the group and determining an associated signal energy value and an interference value;
determining a measured signal to interference ratio (SIR) value using the measured signal energy and interference values;
setting a first SIR threshold;
if the measured SIR value is less than or equal to the first SIR threshold, processing the measured SIR value in a first fashion; and
if the measured SIR value is greater than the first SIR threshold, processing the measured SIR value in a second fashion, wherein processing the SIR value in the first fashion includes;
if the measured SIR value is less than or equal to a second SIR threshold, processing the measured SIR value in the first fashion using a first equation; and
if the measured SIR value is greater than the first SIR threshold, processing the measure SIR value in the first fashion using a second equation. - View Dependent Claims (17, 18, 19)
where y1(x) is a corrected SIR value, x is the measured SIR value in dB units, T is an SIR threshold, and K, D, C0-C2 are coefficients.
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18. The method in claim 17, wherein the second equation is as follows:
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where y2(x) is a corrected SIR value, x is the measured SIR value in dB units, T0 and T1 are SIR thresholds, K0, K1, D0, D1, and C0, C1, and C2 are coefficients.
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19. The method in claim 18, wherein the thresholds and coefficients are determined as a function of a spreading factor used to spread information to be transmitted over an available frequency spectrum.
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21. A spread spectrum communications system, comprising:
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plural mobile stations, and at least one base station, where the mobile stations and the base station communicating using a common frequency band and code division multiple access (CDMA) procedures, the base station including a controller estimating a signal to interference ratio (SIR) associated with a communication between one of the mobile stations and the base station, detecting that the SIR estimate exceeds an SIR saturation threshold, and in response to the detecting step compensating the SIR estimate to minimize a difference between the SIR estimate and an actual SIR corresponding to the SIR estimate. - View Dependent Claims (22, 23, 24, 25, 26, 27)
where y1(x) is the corrected SIR value, x is the measured SIR value in dB units, T is a SIR threshold, and K, D, and C0-C2 are coefficients.
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25. The spread spectrum communications system in claim 24, wherein the coefficients are determined as a function a spreading factor used to spread information to be transmitted over the common frequency band.
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26. The spread spectrum communications system in claim 21, wherein the controller compensates the SIR estimate in accordance with the following:
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where y2(x) is the corrected SIR value, x is the measured SIR value in dB units, T0 and T1 are SIR thresholds, K0, K1, D0, D1, and C0-C2 are coefficients.
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27. The spread spectrum communications system in claim 26, wherein the coefficients are determined as a function a spreading factor used to spread information to be transmitted over the common frequency band.
Specification