Crystal oscillator calibration

Abstract

Systems and methods for temperature-calibration of an uncompensated XO in a mobile device during mobile device operation. The XO is temperature-calibrated based on assistance from wireless signals, such as from satellite source, and optionally from terrestrial sources such as WWAN, CDMA, etc. Based on one or more received wireless signals received at a receiver, corresponding frequency estimates of the XO are obtained and correlated with corresponding operating temperatures in a processor. Based on one or more samples of frequency estimates and associated temperatures, the XO is temperature-calibrated in the processor wherein a frequency-temperature (FT) model is formulated for the XO. The frequency of the temperature-calibrated XO can be determined from the FT model at any given temperature.

What is claimed is: 
     
         1 . A method of temperature-calibrating an uncompensated crystal oscillator (XO), in a mobile device during mobile device operation, the method comprising:
 receiving a first set of wireless signals comprising at least a first wireless signal of known frequency, at a first temperature;   estimating a first frequency of the XO at the first temperature, based on at least the first wireless signal; and   temperature-calibrating the XO based on the first frequency and the first temperature.   
     
     
         2 . The method of  claim 1 , wherein the uncompensated XO comprises a lack of built-in compensation for frequency variation of the XO with variation in temperature or voltage. 
     
     
         3 . The method of  claim 1 , wherein the first wireless signal is transmitted by a first satellite. 
     
     
         4 . The method of  claim 3 , wherein the first satellite comprises a global navigation satellite systems (GNSS) satellite. 
     
     
         5 . The method of  claim 4 , further comprising receiving GNSS assistance information. 
     
     
         6 . The method of  claim 5 , wherein the GNSS assistance information further comprises a location of the mobile device. 
     
     
         7 . The method of  claim 5 , wherein the GNSS assistance information comprises GNSS Ephemeris information. 
     
     
         8 . The method of  claim 5 , wherein the GNSS assistance information comprises Almanac information. 
     
     
         9 . The method of  claim 5 , further comprising determining a location of the mobile device. 
     
     
         10 . The method of  claim 9 , wherein determining the location is based on at least one terrestrial signal. 
     
     
         11 . The method of  claim 9 , wherein determining the location is based on GNSS signals. 
     
     
         12 . The method of  claim 9 , wherein the first set of wireless signals further comprises at least a second wireless signal transmitted by a second satellite and a third wireless signal transmitted by a third satellite. 
     
     
         13 . The method of  claim 12 , wherein estimating the first frequency of the XO at the first temperature is further based on at least the second and third wireless signals. 
     
     
         14 . The method of  claim 13 , wherein estimating the first frequency of the XO at the first temperature comprises obtaining the location based on at least the first, second, and the third wireless signals. 
     
     
         15 . The method of  claim 13 , wherein estimating the first frequency of the XO at the first temperature comprises: obtaining an effective frequency of the first, second, and third wireless signals, wherein the frequencies of the first, second, and third wireless signals are offset by a first, second, and third Doppler relative to the effective frequency; and deriving a first frequency error of the XO based on the effective frequency. 
     
     
         16 . The method of  claim 12 , wherein, estimating the first frequency of the XO at the first temperature comprises:
 deriving a first effective frequency from the first wireless signal, a second effective frequency from the second wireless signal, and a third effective frequency from the third wireless signal;   determining a derived effective frequency based on one or more of the first, second, and third effective frequencies;   determining a frequency variation of a local oscillator on the mobile device, as a difference in frequency between the derived effective frequency and a frequency of the local oscillator, wherein the local oscillator is sourced from the XO;   normalizing the frequency variation of the local oscillator based on an expected nominal frequency of the local oscillator;   determining a normalized frequency variation of the XO as equal to the normalized frequency variation of the local oscillator; and   determining the first frequency based on the normalized frequency variation of the XO and an expected nominal frequency of the XO.   
     
     
         17 . The method of  claim 16 , wherein the derived effective frequency is based on the strongest of the first, second, and third effective frequencies. 
     
     
         18 . The method of  claim 16 , wherein the derived effective frequency is based on a combination of the first, second, and third effective frequencies. 
     
     
         19 . The method of  claim 18 , wherein the combination is one of a weighted average, a mean, a median, a least squares, or a pre-specified mathematical fit of the first, second, and third effective frequencies. 
     
     
         20 . The method of  claim 3 , wherein a Doppler of the first wireless signal transmitted by the first satellite is constant. 
     
     
         21 . The method of  claim 20 , wherein the first satellite is geostationary and the Doppler of the first wireless signal is zero. 
     
     
         22 . The method of  claim 20 , wherein the first satellite comprises a satellite-based augmentation system (SBAS) satellite. 
     
     
         23 . The method of  claim 20 , further comprising determining whether the first wireless signal satisfies a pre-specified signal to noise ratio (SNR). 
     
     
         24 . The method of  claim 20 , further comprising determining whether the first wireless signal passes a pre-specified error or parity check. 
     
     
         25 . The method of  claim 3 , wherein the mobile device is in motion, and wherein estimating the first frequency of the XO at the first temperature, based on at least the first wireless signal further comprises estimating a difference between a measured Doppler of the first wireless signal and a predicted Doppler of the first wireless signal based on a speed of motion of the mobile device. 
     
     
         26 . The method of  claim 1 , wherein temperature-calibrating the XO comprises determining a relationship between frequency of the XO and temperature, based on at least the first frequency and the first temperature. 
     
     
         27 . The method of  claim 26 , wherein the relationship is a polynomial equation of the frequency of the XO and temperature with a number of unknown coefficients based on an order of the polynomial equation. 
     
     
         28 . The method of  claim 27  comprising reducing the number of unknown coefficients based on specifications of the XO. 
     
     
         29 . The method of  claim 27  comprising reducing the number of unknown coefficients based on precalibration of the XO during manufacturing of the XO. 
     
     
         30 . The method of  claim 27  comprising reducing the number of unknown coefficients based on constraining a variation in temperature. 
     
     
         31 . The method of  claim 1 , further comprising:
 receiving a second set of wireless signals comprising at least one wireless signal of known frequency at a second temperature;   estimating a second frequency of the XO at the second temperature, based on the second set of wireless signals, wherein the second temperature is different from the first temperature; and   further temperature-calibrating the XO based on the second frequency and the second temperature.   
     
     
         32 . The method of  claim 31 , wherein further temperature-calibrating the XO comprises determining a relationship between frequency of the XO and temperature, based on at least the first frequency and the first temperature and on the second frequency and the second temperature. 
     
     
         33 . The method of  claim 31 , further comprising
 receiving a third set of wireless signals comprising at least one wireless signal of known frequency at a third temperature;   estimating a third frequency of the XO at the third temperature, based on the third set of wireless signals, wherein the third temperature is different from the first temperature and the second temperature; and   further temperature-calibrating the XO based on the third frequency and the third temperature.   
     
     
         34 . The method of  claim 33 , wherein further temperature-calibrating the XO comprises determining a relationship between frequency of the XO and temperature, based on at least the first frequency and the first temperature, the second frequency and the second temperature, and the third frequency and the third temperature. 
     
     
         35 . A method of temperature-calibrating an uncompensated crystal oscillator (XO) in a mobile device during mobile device operation, the method comprising:
 receiving a first set of wireless signals comprising at least a first wireless signal, from a signal source of known frequency and known Doppler, at a first temperature, wherein a plurality of satellite signals is unavailable;   estimating a first frequency of the XO at the first temperature, based on at least the first wireless signal; and   temperature-calibrating the XO based on the first frequency and the first temperature.   
     
     
         36 . The method of  claim 35 , wherein the signal source is a satellite. 
     
     
         37 . The method of  claim 36 , wherein the satellite is geo-stationary with zero Doppler. 
     
     
         38 . The method of  claim 37 , wherein the satellite is a satellite based augmentation system (SBAS) satellite. 
     
     
         39 . The method of  claim 36 , further comprising obtaining a location of the mobile device from an approximate location using cell sector center of a serving cell, from a trilateration of terrestrial signals, from a positioning server, or from a base station Almanac on the mobile device. 
     
     
         40 . The method of  claim 39 , further comprising determining an effective frequency of the first wireless signal based on Ephemeris and time at the mobile device. 
     
     
         41 . The method of  claim 40 , wherein, estimating the first frequency of the XO at the first temperature comprises:
 determining a frequency variation of a local oscillator on the mobile device, as a difference in frequency between the effective frequency and a frequency of the local oscillator, wherein the local oscillator is sourced from the XO;   normalizing the frequency variation of the local oscillator based on an expected nominal frequency of the local oscillator;   determining a normalized frequency variation of the XO as equal to the normalized frequency variation of the local oscillator; and   determining the first frequency based on the normalized frequency variation of the XO and an expected nominal frequency of the XO.   
     
     
         42 . The method of  claim 36 , further comprising determining whether the first wireless signal satisfies a pre-specified signal to noise ratio (SNR). 
     
     
         43 . The method of  claim 36 , further comprising determining whether the first wireless signal passes a pre-specified error or parity check. 
     
     
         44 . The method of  claim 35 , comprising receiving the first set of wireless signals from a calibrated terrestrial source. 
     
     
         45 . The method of  claim 44 , wherein the calibrated terrestrial source is one of a wireless wide area network (WWAN), code division multiple access (CDMA) network, or long term evolution (LTE) network. 
     
     
         46 . A system comprising:
 a mobile device comprising an uncompensated crystal oscillator (XO);   means for receiving a first set of wireless signals comprising at least a first wireless signal of known frequency, at a first temperature;   means for estimating a first frequency of the XO at the first temperature, based on at least the first wireless signal; and   means for temperature-calibrating the XO based on the first frequency and the first temperature during operation of the mobile device.   
     
     
         47 . The system of  claim 46 , wherein the uncompensated XO comprises a lack of built-in compensation for frequency variation of the XO with variation in temperature or voltage. 
     
     
         48 . The system of  claim 46 , wherein the first wireless signal is transmitted by a first satellite. 
     
     
         49 . The system of  claim 48 , wherein the first satellite comprises a GNSS satellite. 
     
     
         50 . The system of  claim 49 , further comprising means for receiving GNSS assistance information. 
     
     
         51 . The system of  claim 50 , wherein the GNSS assistance information further comprises a location of the mobile device. 
     
     
         52 . The system of  claim 50 , wherein the GNSS assistance information comprises GNSS Ephemeris information. 
     
     
         53 . The system of  claim 50 , wherein the GNSS assistance information comprises Almanac information. 
     
     
         54 . The system of  claim 50 , further comprising means for determining a location of the mobile device. 
     
     
         55 . The system of  claim 54 , wherein the means determining the location utilizes at least one terrestrial signal. 
     
     
         56 . The system of  claim 54 , wherein the means for determining the location utilizes GNSS signals. 
     
     
         57 . The system of  claim 54 , wherein the first set of wireless signals further comprises at least a second wireless signal transmitted by a second satellite and a third wireless signal transmitted by a third satellite. 
     
     
         58 . The system of  claim 57 , wherein the means for estimating the first frequency of the XO at the first temperature is further based on at least the second and third wireless signals. 
     
     
         59 . The system of  claim 58 , wherein the means for estimating the first frequency of the XO at the first temperature comprises means for obtaining the location based on at least the first, second, and the third wireless signals. 
     
     
         60 . The system of  claim 58 , wherein the means for estimating the first frequency of the XO at the first temperature comprises: means for obtaining an effective frequency of the first, second, and third wireless signals, wherein the frequencies of the first, second, and third wireless signals are offset by a first, second, and third Doppler relative to the effective frequency; and means for deriving a first frequency error of the XO based on the effective frequency. 
     
     
         61 . The system of  claim 57 , wherein, the means for estimating the first frequency of the XO at the first temperature comprises:
 means for deriving a first effective frequency from the first wireless signal, a second effective frequency from the second wireless signal, and a third effective frequency from the third wireless signal;   determining a derived effective frequency based on one or more of the first, second, and third effective frequencies;   means for determining a frequency variation of a local oscillator on the mobile device, as a difference in frequency between the derived effective frequency and a frequency of the local oscillator, wherein the local oscillator is sourced from the XO;   means for normalizing the frequency variation of the local oscillator based on an expected nominal frequency of the local oscillator;   means for determining a normalized frequency variation of the XO as equal to the normalized frequency variation of the local oscillator; and   means for determining the first frequency based on the normalized frequency variation of the XO and an expected nominal frequency of the XO.   
     
     
         62 . The system of  claim 61 , wherein the derived effective frequency is based on the strongest of the first, second, and third effective frequencies. 
     
     
         63 . The system of  claim 61 , wherein the derived effective frequency is based on a combination of the first, second, and third effective frequencies. 
     
     
         64 . The system of  claim 63 , wherein the combination is one of a weighted average, a mean, a median, a least squares, or a pre-specified mathematical fit of the first, second, and third effective frequencies. 
     
     
         65 . The system of  claim 48 , wherein a Doppler of the first wireless signal transmitted by the first satellite is constant. 
     
     
         66 . The system of  claim 65 , wherein the first satellite is geostationary and the Doppler of the first wireless signal is zero. 
     
     
         67 . The system of  claim 65 , wherein the first satellite comprises a satellite-based augmentation system (SBAS) satellite. 
     
     
         68 . The system of  claim 65 , further comprising means for determining whether the first wireless signal satisfies a pre-specified signal to noise ratio (SNR). 
     
     
         69 . The system of  claim 65 , further comprising means for determining whether the first wireless signal passes a pre-specified error or parity check. 
     
     
         70 . The system of  claim 48 , wherein the mobile device is in motion, and wherein the means for estimating the first frequency of the XO at the first temperature, based on at least the first wireless signal further comprises means for estimating a difference between a measured Doppler of the first wireless signal and a predicted Doppler of the first wireless signal based on a speed of motion of the mobile device. 
     
     
         71 . The system of  claim 46 , wherein the means for temperature-calibrating the XO comprises means for determining a relationship between frequency of the XO and temperature, based on at least the first frequency and the first temperature. 
     
     
         72 . The system of  claim 71 , wherein the relationship is a polynomial equation of the frequency of the XO and temperature with a number of unknown coefficients based on an order of the polynomial equation. 
     
     
         73 . The system of  claim 72  comprising means for reducing the number of unknown coefficients based on specifications of the XO. 
     
     
         74 . The system of  claim 72  comprising means for reducing the number of unknown coefficients based on precalibration of the XO during manufacturing of the XO. 
     
     
         75 . The system of  claim 72  comprising means for reducing the number of unknown coefficients based on constraining a variation in temperature. 
     
     
         76 . The system of  claim 46 , further comprising:
 means for receiving a second set of wireless signals comprising at least one wireless signal of known frequency at a second temperature;   means for estimating a second frequency of the XO at the second temperature, based on the second set of wireless signals, wherein the second temperature is different from the first temperature; and   means for further temperature-calibrating the XO based on the second frequency and the second temperature.   
     
     
         77 . The system of  claim 76 , wherein the means for further temperature-calibrating the XO comprises means for determining a relationship between frequency of the XO and temperature, based on at least the first frequency and the first temperature and on the second frequency and the second temperature. 
     
     
         78 . The system of  claim 76 , further comprising
 means for receiving a third set of wireless signals comprising at least one wireless signal of known frequency at a third temperature;   means for estimating a third frequency of the XO at the third temperature, based on the third set of wireless signals, wherein the third temperature is different from the first temperature and the second temperature; and   means for further temperature-calibrating the XO based on the third frequency and the third temperature.   
     
     
         79 . The system of  claim 78 , wherein the means for further temperature-calibrating the XO comprises means for determining a relationship between frequency of the XO and temperature, based on at least the first frequency and the first temperature, the second frequency and the second temperature, and the third frequency and the third temperature. 
     
     
         80 . A system comprising:
 a mobile device comprising an uncompensated crystal oscillator (XO);   means for receiving a first set of wireless signals comprising at least a first wireless signal, from a signal source of known frequency and known Doppler, at a first temperature, wherein a plurality of satellite signals is unavailable;   means for estimating a first frequency of the XO at the first temperature, based on at least the first wireless signal; and   means for temperature-calibrating the XO based on the first frequency and the first temperature during operation of the mobile device.   
     
     
         81 . The system of  claim 80 , wherein the signal source is a satellite. 
     
     
         82 . The system of  claim 81 , wherein the satellite is geo-stationary with zero Doppler. 
     
     
         83 . The system of  claim 82 , wherein the satellite is a satellite based augmentation system (SBAS) satellite. 
     
     
         84 . The system of  claim 81 , further comprising means for obtaining a location of the mobile device from an approximate location using cell sector center of a serving cell, from a trilateration of terrestrial signals, from a positioning server, or from a base station Almanac on the device. 
     
     
         85 . The system of  claim 84 , further comprising means for determining an effective frequency of the first wireless signal based on Ephemeris and time at the mobile device. 
     
     
         86 . The system of  claim 85 , wherein, the means for estimating the first frequency of the XO at the first temperature comprises:
 means for determining a frequency variation of a local oscillator on the mobile device, as a difference in frequency between the effective frequency and a frequency of the local oscillator, wherein the local oscillator is sourced from the XO;   means for normalizing the frequency variation of the local oscillator based on an expected nominal frequency of the local oscillator;   means for determining a normalized frequency variation of the XO as equal to the normalized frequency variation of the local oscillator; and   means for determining the first frequency based on the normalized frequency variation of the XO and an expected nominal frequency of the XO.   
     
     
         87 . The system of  claim 81 , further comprising means for determining whether the first wireless signal satisfies a pre-specified signal to noise ratio (SNR). 
     
     
         88 . The system of  claim 81 , further comprising means for determining whether the first wireless signal passes a pre-specified error or parity check. 
     
     
         89 . The system of  claim 80 , comprising means for receiving the first set of wireless signals from a calibrated terrestrial source. 
     
     
         90 . The system of  claim 89 , wherein the calibrated terrestrial source is one of a wireless wide area network (WWAN), code division multiple access (CDMA) network, or long term evolution (LTE) network. 
     
     
         91 . A mobile device comprising:
 an uncompensated crystal oscillator (XO);   a temperature sensor configured to provide a first temperature;   one or more receivers configured to receive a first set of wireless signals comprising at least a first wireless signal of known frequency, at the first temperature; and   a processor configured to estimate a first frequency of the XO at the first temperature, based on at least the first wireless signal, and temperature-calibrate the XO based on the first frequency and the first temperature during operation of the mobile device.   
     
     
         92 . The mobile device of  claim 91 , wherein the uncompensated XO comprises a lack of built-in compensation for frequency variation of the XO with variation in temperature or voltage. 
     
     
         93 . The mobile device of  claim 91 , wherein the first wireless signal is transmitted by a first satellite. 
     
     
         94 . The mobile device of  claim 93 , wherein the first satellite comprises a GNSS satellite. 
     
     
         95 . The mobile device of  claim 94 , wherein at least one of the receivers is further configured to receive GNSS assistance information. 
     
     
         96 . The mobile device of  claim 95 , wherein the GNSS assistance information further comprises a location of the mobile device. 
     
     
         97 . The mobile device of  claim 95 , wherein the GNSS assistance information comprises GNSS Ephemeris information. 
     
     
         98 . The mobile device of  claim 95 , wherein the GNSS assistance information comprises Almanac information. 
     
     
         99 . The mobile device of  claim 5 , wherein the processor is further configured to determine a location of the mobile device. 
     
     
         100 . The mobile device of  claim 99 , wherein the processor is configured to determine the location based on at least one terrestrial signal. 
     
     
         101 . The mobile device of  claim 99 , wherein the processor is configured to determine the location based on GNSS signals. 
     
     
         102 . The mobile device of  claim 99 , wherein the first set of wireless signals further comprises at least a second wireless signal transmitted by a second satellite and a third wireless signal transmitted by a third satellite. 
     
     
         103 . The mobile device of  claim 102 , wherein the processor is further configured to estimate the first frequency of the XO at the first temperature based on at least the second and third wireless signals. 
     
     
         104 . The mobile device of  claim 103 , wherein the processor is configured to estimate the first frequency of the XO at the first temperature based on a location of the mobile device determined from at least the first, second, and the third wireless signals. 
     
     
         105 . The mobile device of  claim 103 , wherein the processor is configured to: estimate the first frequency of the XO at the first temperature based on an effective frequency of the first, second, and third wireless signals, wherein the frequencies of the first, second, and third wireless signals are offset by a first, second, and third Doppler relative to the effective frequency; and derive a first frequency error of the XO based on the effective frequency. 
     
     
         106 . The mobile device of  claim 102 , further comprising at least one local oscillator sourced from the XO, wherein the processor is configured to derive a first effective frequency from the first wireless signal, a second effective frequency from the second wireless signal, and a third effective frequency from the third wireless signal, and a derived effective frequency based on one or more of the first, second, and third effective frequencies;
 a band pass filter configured to determine a frequency variation of the at least one local oscillator as a difference in frequency between the derived effective frequency and a frequency of the local oscillator; and   the processor is further configured to normalize the frequency variation of the local oscillator based on an expected nominal frequency of the local oscillator, determine a normalized frequency variation of the XO as equal to the normalized frequency variation of the local oscillator, and determine the first frequency based on the normalized frequency variation of the XO and an expected nominal frequency of the XO.   
     
     
         107 . The mobile device of  claim 106 , wherein the derived effective frequency is based on the strongest of the first, second, and third effective frequencies. 
     
     
         108 . The mobile device of  claim 106 , wherein the derived effective frequency is based on a combination of the first, second, and third effective frequencies. 
     
     
         109 . The mobile device of  claim 108 , wherein the combination is one of a weighted average, a mean, a median, a least squares, or a pre-specified mathematical fit of the first, second, and third effective frequencies. 
     
     
         110 . The mobile device of  claim 93 , wherein a Doppler of the first wireless signal transmitted by the first satellite is constant. 
     
     
         111 . The mobile device of  claim 110 , wherein the first satellite is geostationary and the Doppler of the first wireless signal is zero. 
     
     
         112 . The mobile device of  claim 110 , wherein the first satellite comprises a satellite-based augmentation system (SBAS) satellite. 
     
     
         113 . The mobile device of  claim 10 , wherein the processor is further configured to determine whether the first wireless signal satisfies a pre-specified signal to noise ratio (SNR). 
     
     
         114 . The mobile device of  claim 110 , wherein the processor is further configured to determine whether the first wireless signal passes a pre-specified error or parity check. 
     
     
         115 . The mobile device of  claim 93 , wherein the mobile device is in motion, and wherein the processor is configured to estimate the first frequency of the XO at the first temperature, based on a difference between a measured Doppler of the first wireless signal and a predicted Doppler of the first wireless signal based on a speed of motion of the mobile device. 
     
     
         116 . The mobile device of  claim 91 , wherein the temperature-calibration of the XO comprises a relationship between frequency of the XO and temperature, based on at least the first frequency and the first temperature. 
     
     
         117 . The mobile device of  claim 116 , wherein the relationship is a polynomial equation of the frequency of the XO and temperature with a number of unknown coefficients based on an order of the polynomial equation. 
     
     
         118 . The mobile device of  claim 117 , wherein the processor is further configured to temperature-calibrate the XO using a reduced number of unknown coefficients, wherein the reduced number of unknown coefficients is based on specifications of the XO. 
     
     
         119 . The mobile device of  claim 118 , wherein the reduced number of unknown coefficients is based on precalibration of the XO during manufacture of the XO. 
     
     
         120 . The mobile device of  claim 118 , wherein the reduced number of unknown coefficients is based on constraints in variation of temperature. 
     
     
         121 . The mobile device of  claim 91 , wherein,
 the one or more receivers are further configured to receive a second set of wireless signals comprising at least one wireless signal of known frequency at a second temperature;   the temperature sensor is configured to provide a second temperature, wherein the second temperature is different from the first temperature; and   the processor is further configured to estimate a second frequency of the XO at the second temperature, based on the second set of wireless signals and further temperature-calibrate the XO based on the second frequency and the second temperature.   
     
     
         122 . The mobile device of  claim 121 , wherein the further temperature-calibration of the XO comprises a relationship between frequency of the XO and temperature, based on at least the first frequency and the first temperature and on the second frequency and the second temperature. 
     
     
         123 . The mobile device of  claim 121 , wherein
 the one or more receivers are further configured to receive a third set of wireless signals comprising at least one wireless signal of known frequency at a third temperature;   the temperature sensor is configured to provide a third temperature, wherein the third temperature is different from the first temperature and the second temperature; and   the processor is further configured to estimate a third frequency of the XO at the third temperature, based on the third set of wireless signals and further temperature-calibrate the XO based on the third frequency and the third temperature.   
     
     
         124 . The mobile device of  claim 123 , wherein the further temperature-calibration of the XO comprises a relationship between frequency of the XO and temperature, based on at least the first frequency and the first temperature, the second frequency and the second temperature, and the third frequency and the third temperature. 
     
     
         125 . A mobile device comprising:
 an uncompensated crystal oscillator (XO);   a temperature configured to provide a first temperature;   one or more receivers configured to receive a first set of wireless signals comprising at least a first wireless signal, from a signal source of known frequency and known Doppler, at the first temperature, wherein a plurality of satellite signals is unavailable; and   a processor configured to estimate a first frequency of the XO at the first temperature, based on at least the first wireless signal and temperature-calibrate the XO based on the first frequency and the first temperature.   
     
     
         126 . The mobile device of  claim 125 , wherein the signal source is a satellite. 
     
     
         127 . The mobile device of  claim 126 , wherein the satellite is geo-stationary with zero Doppler. 
     
     
         128 . The mobile device of  claim 127 , wherein the satellite is a satellite based augmentation system (SBAS) satellite. 
     
     
         129 . The mobile device of  claim 126 , wherein the processor is further configured to obtain a location of the mobile device from an approximate location using cell sector center of a serving cell, from a trilateration of terrestrial signals, from a positioning server, or from a base station Almanac on the mobile device. 
     
     
         130 . The mobile device of  claim 129 , wherein the processor is further configured to determine an effective frequency of the first wireless signal based on Ephemeris and time at the mobile device. 
     
     
         131 . The mobile device of  claim 130 , further comprising a local oscillator sourced from the XO and a band pass filter configured to determine a frequency variation of the local oscillator as a difference in frequency between the effective frequency and a frequency of the local oscillator, and wherein the processor is further configured to normalize the frequency variation of the local oscillator based on an expected nominal frequency of the local oscillator, determine a normalized frequency variation of the XO as equal to the normalized frequency variation of the local oscillator, and determine the first frequency based on the normalized frequency variation of the XO and an expected nominal frequency of the XO. 
     
     
         132 . The mobile device of  claim 126 , wherein the processor is further configured to determine whether the first wireless signal satisfies a pre-specified signal to noise ratio (SNR). 
     
     
         133 . The mobile device of  claim 126 , wherein the processor is further configured to determine whether the first wireless signal passes a pre-specified error or parity check. 
     
     
         134 . The mobile device of  claim 125 , wherein the one or more receivers are configured to receive the first set of wireless signals from a calibrated terrestrial source. 
     
     
         135 . The mobile device of  claim 134 , wherein the calibrated terrestrial source is one of a wireless wide area network (WWAN), code division multiple access (CDMA) network, or long term evolution (LTE) network. 
     
     
         136 . A mobile device comprising:
 an uncompensated crystal oscillator (XO);   a temperature sensor configured to provide a first temperature;   one or more receivers configured to receive a first set of wireless signals comprising at least a first wireless signal of known frequency, at a first temperature;   a processor; and   a non-transitory computer-readable storage medium comprising code, which, when executed by the processor, causes the processor to perform operations for temperature-calibrating a crystal oscillator (XO), the non-transitory computer-readable storage medium comprising:   code for estimating a first frequency of the XO at the first temperature, based on at least the first wireless signal;   code for determining unknown coefficients of a polynomial equation comprising a relationship between frequency of the XO and temperature based on at least the first frequency and the first temperature.