Method and system for frequency drift prediction
View Patent ↗A method ( 200 ) of frequency drift prediction for use by a positioning receiver ( 106 ) can include the steps of determining ( 202 ) a moving average of a frequency error, determining ( 206 ) a moving average of a frequency drift rate in a communication device, determining ( 212 ) a frequency drift rate uncertainty, and providing ( 214 ) the moving average of frequency error and frequency drift rate, and the frequency drift rate uncertainty to the positioning receiver. A point-to-point slope from the running average of the instantaneous frequency error and a running average of the point-to-point slope for a predetermined time period can be determined ( 208 & 210 ). The frequency drift uncertainty or window is determined using information determined from the moving average of the frequency drift rate. The positioning receiver can be a global positioning receiver.
1. A method of frequency drift prediction for use by a positioning receiver, comprising the steps of:
determining a moving average of a frequency error in a communication device;
determining a moving average of a frequency drift rate of the communication device;
determining a frequency drift rate uncertainty in a communication device; and
providing the moving average of the frequency error, the moving average of the frequency drift rate, and the frequency drift rate uncertainty to the positioning receiver.
2. The method of claim 1 , wherein the step of determining the moving average of the frequency error comprises determining a moving average of a cumulative frequency error by measuring a running average of real-time frequency error.
3. The method of claim 2 , wherein the method further comprises the step of determining a point-to-point slope from the moving average of the cumulative frequency error.
4. The method of claim 3 , wherein the method further comprises the step of determining a running average of the point-to-point slope for a predetermined time period.
5. The method of claim 4 , wherein the method further comprises the step of determining a drift rate uncertainty from the difference between a maximum and a minimum from the predetermined period as a +/−parameter.
6. The method of claim 1 , wherein the method further comprises the step of determining a moving average of cumulative frequency error of the communication device.
7. The method of claim 1 , wherein the positioning receiver is a global positioning receiver and the step of providing the moving average of the frequency error, the moving average of the frequency drift rate, and the frequency drift rate uncertainty occurs when the global positioning receiver is in a weak satellite signal condition.
8. The method of claim 1 , wherein the steps of determining the moving average of a frequency drift rate and the frequency drift rate uncertainty is done using the automatic frequency control of the communication device in real time.
9. The method of claim 1 , wherein the method further comprises the step of obtaining a faster time-to-first-fix for the positioning receiver at low satellite signal level.
10. A method for generating a frequency reference in a hybrid communications device, comprising the steps of:
generating a clock signal at a base frequency;
performing communications processing in a communications receiver based on an input of the clock signal at the base frequency;
generating frequency tracking data containing a moving average of a frequency error, frequency drift rate and a drift rate uncertainty of the communications receiver;
transmitting a control message to the positioning receiver to adapt positioning processing based on the frequency tracking data; and
performing positioning processing in a positioning receiver based on an input of the clock signal at the base frequency.
11. A method according to claim 10 , wherein the frequency tracking data comprises an automatic frequency control message.
12. A system for generating a frequency reference in a hybrid communications device, comprising:
a clock source generating a clock signal at a base frequency;
a communications receiver, the communications receiver performing communications processing based on an input of the clock signal at the base frequency, the communications receiver generating frequency tracking data containing a moving average of frequency error, a frequency drift rate and a drift rate uncertainty;
a positioning receiver, the positioning receiver performing positioning processing based on an input of the clock signal at the base frequency; and
a processor, the processor transmitting a control message to the positioning receiver to adapt positioning processing based on the frequency tracking data, the processor communicating with the communications receiver and the positioning receiver.
13. A system according to claim 12 , wherein the communications receiver comprises at least one of a cellular telephone, a personal digital assistant, a two-way pager, a radio receiving device, a modem, and a network-enabled wireless device.
14. A system according to claim 12 , wherein the communications receiver comprises at least one of a radio receiving device, transceiver, a wireless modem, a wired modem and an optical-receiver.
15. A system according to claim 12 , wherein the positioning receiver comprises a Global Positioning System receiver.
16. A system according to claim 12 , wherein the frequency tracking data comprises an automatic frequency control message.
17. A system according to claim 16 , wherein the automatic frequency control message comprises frequency deviation data generated by comparison to a base station signal.
18. The system according to claim 12 , wherein the processor is further programmed to determine a moving average of the cumulative frequency error, a moving average of a drift rate, and a drift rate uncertainty of the communication receiver, and provide the moving average of the cumulative frequency error, moving average of the drift rate, and the drift rate uncertainty to the positioning receiver.