Adjustment of period of real-time slow drift correction of alignment of handset's local oscillator for a cordless telephone

Abstract

A method and apparatus to perform a real-time drift correction of a remote handset's local oscillator in a digital cordless telephone. The remote handset begins in a standby (sniff) mode. The remote handset periodically wakes from a sleep mode and goes into a normal link verification mode. Once in the link verification mode, the remote handset enters a time division duplexing (TDD) mode and attempts to establish a link with a base unit based on the timing of the TDD data frame. After the remote handset establishes a link with the base unit, the remote handset requests a security word from the base unit. Upon receiving the requested security word, the remote handset determines if the requested security word matches a security word of the remote handset. The remote handset implements a software frequency adjustment of its local oscillator. Once per frame, the remote handset enters a timing recovery state where the current state of the frame is compared with a previous state. When the cumulative timing slip is greater than a designated threshold, a frequency adjustment is made. During this exchange of commands between the remote handset and base unit, the remote handset continuously adjusts its local oscillator to achieve frequency alignment within, e.g., 1 part per million (ppm). Alternatively, frequency alignment may be achieved to a specified value. The period of the frequency alignment can be lengthened (or even suspended) during certain power critical modes to reduce power consumption. For example, the period of the link verify operations (and thus the frequency alignment) can be lengthened or suspended when the remote handset is being quick charged. Moreover, the period of the link verify operations can be adjusted based on a voltage level of the battery in the remote handset.

What is claimed is: 
     
       1. A method of determining a period for an operation between a remote unit handset and a matching base unit, said method comprising:
 detecting a re-charging to a of said remote handset from a by said matching base unit; and 
 in response to detecting the re-charging of said remote handset, adjusting a period between a check of frequency alignment between said remote handset and said matching base unit based on a battery voltage level in said remote handset. 
 
     
     
       2. The method of determining a period for an operation between a remote unit and a matching base unit according to  claim 1 , further comprising:
 suspending said check of said frequency alignment when said remote handset is in a predetermined mode. 
 
     
     
       3. The method of determining a period for an operation between a remote unit and a matching base unit according to  claim 2 , wherein:
 said predetermined mode is a quick charge mode. 
 
     
     
       4. The method of determining a period for an operation between a remote unit and a matching base unit according to  claim 1 , wherein:
 said period is adjusted between a predetermined maximum period and a predetermined minimum period. 
 
     
     
       5. Apparatus for determining a period for an operation between a remote unit handset and a matching base unit, comprising:
 means for detecting a re-charging to a of said remote handset from a by said matching base unit; and 
 means, responsive to said means for detecting a re-charging of said handset detecting the re-charging of said handset, for adjusting a period between a check of frequency alignment between said remote handset and said matching base unit based on a battery voltage level in said remote handset. 
 
     
     
       6. The apparatus for determining a period for an operation between a remote unit and a matching base unit according to  claim 5 , further comprising:
 means for suspending said check of said frequency alignment when said remote handset is in a predetermined mode. 
 
     
     
       7. The apparatus for determining a period for an operation between a remote unit and a matching base unit according to  claim 6 , wherein:
 said predetermined mode is a quick charge mode. 
 
     
     
       8. The apparatus for determining a period for an operation between a remote unit and a matching base unit according to  claim 5 , wherein:
 said period is adjusted between a predetermined maximum period and a predetermined minimum period. 
 
     
     
       9. A method of adjusting a frequency of an alignment operation between two wireless components that communicate with one another, comprising:
 detecting a re-charging of one of said two wireless components; 
 monitoring a voltage output level of a battery in at least said one of said two wireless components; and 
 decreasing a frequency of said alignment operation between said two wireless components if in response to detecting the re-charging of said one of said two wireless components and determining by said monitoring that the monitored voltage output level of said battery falls is below a given threshold level. 
 
     
     
       10. The method of adjusting a frequency of an alignment operation between two wireless components that communicate with one another according to  claim 9 , wherein:
 said two wireless components comprise a cordless telephone. 
 
     
     
       11. The method of adjusting a frequency of an alignment operation between two wireless components that communicate with one another according to  claim 10 , wherein:
 said monitored battery powers a remote handset of said cordless telephone. 
 
     
     
       12. The A method of adjusting a frequency of an alignment operation between two wireless components that communicate with one another according to  claim 10 , the method comprising:
 monitoring a voltage output level of a battery in at least one of said two wireless components; and 
 decreasing a frequency of said alignment operations between said two wireless components if said monitored voltage output level of said battery falls below a given threshold level, 
 wherein: said frequency of said alignment operation maintains at least 15 minutes between frequency alignment operations. 
 
     
     
       13. Apparatus for adjusting a frequency of an alignment operation between two wireless components that communicate with one another, comprising:
 means for detecting a re-charging of one of said two wireless components; 
 means for monitoring a voltage output level of a battery in at least said one of said two wireless components; and 
 means for decreasing a frequency of said alignment operation between said two wireless components if in response to said means for detecting the re-charging of said one of said two wireless components, and said means for monitoring determining that the monitored voltage output level of said battery falls is below a given threshold level. 
 
     
     
       14. The apparatus for adjusting a frequency of an alignment operation between two wireless components that communicate with one another according to  claim 13 , wherein:
 said two wireless components comprise a cordless telephone. 
 
     
     
       15. The apparatus for adjusting a frequency of an alignment operation between two wireless components that communicate with one another according to  claim 14 , wherein:
 said monitored battery powers a remote handset of said cordless telephone. 
 
     
     
       16. The apparatus Apparatus for adjusting a frequency of an alignment operation between two wireless components that communicate with one another according to  claim 13 , comprising:
 means for monitoring a voltage output level of a battery in at least one of said two wireless components; and 
 means for decreasing a frequency of said alignment operation between said two wireless components if said monitored voltage output level of said battery falls below a given threshold level, 
 wherein: said means for decreasing a frequency of said alignment operation adjusts said frequency of said alignment operations to maintain at least 15 minutes between frequency alignment operations. 
 
     
     
       17. A method for adjusting a frequency of alignment operations of a wireless device, comprising:
 detecting a re-charging of the wireless device; and   in response to detecting the re-charging of the wireless device, adjusting the frequency of alignment operations of the wireless device.   
     
     
       18. The method of claim 17, wherein said detecting a re-charging of the wireless device includes:
 detecting a change from a condition in which an external unit is not charging the wireless device to a condition in which the external unit is charging the wireless device.   
     
     
       19. The method of claim 17, wherein said adjusting a frequency of alignment operations includes:
 increasing an interval between frequency alignment operations of a local oscillator of the wireless device.   
     
     
       20. The method of claim 19, further comprising:
 setting the interval between frequency alignment operations.   
     
     
       21. The method of claim 20, wherein said setting the interval comprises:
 measuring a voltage level of a battery of the wireless device; and   setting the interval based on the measured voltage level.   
     
     
       22. The method of claim 20, further comprising:
 setting the interval to a predetermined fixed interval.   
     
     
       23. The method of claim 19, further comprising:
 performing a frequency alignment operation of the local oscillator after the interval has expired.   
     
     
       24. The method of claim 23, wherein said performing the frequency alignment operation includes:
 performing the frequency alignment operation during an authentication process for the wireless device.   
     
     
       25. The method of claim 24, wherein the authentication process includes an exchange of commands by the wireless device. 
     
     
       26. The method of claim 17, wherein the wireless device is a cordless telephone. 
     
     
       27. A wireless device, comprising:
 a local oscillator configured to generate clock signals for use in the wireless device; and   a processor configured to detect a re-charging of the wireless device by an external matching base unit and, in response to detecting the re-charging of the wireless device, to adjust a frequency of alignment operations of the local oscillator in the wireless device.   
     
     
       28. The wireless device of claim 27, further comprising:
 a link verify period setting module configured to set an interval between frequency alignment operations of the local oscillator based on the detected re-charging of the wireless device.   
     
     
       29. The wireless device of claim 27, wherein the processor is further configured to adjust the frequency of the local oscillator. 
     
     
       30. The wireless device of claim 29, wherein the processor is configured to adjust the frequency of the local oscillator to within a predetermined value of a frequency of an oscillator of the external matching base unit. 
     
     
       31. A method for adjusting a frequency of a local oscillator in a wireless device, comprising:
 detecting a re-charging of the wireless device by an external unit;   periodically transitioning the re-charging wireless device from a standby mode to an authentication mode;   exchanging commands between the wireless device and the external unit during the authentication mode;   adjusting the frequency of the local oscillator to within a predetermined value of a frequency of an oscillator of the external unit based on timing information derived from the exchanged commands; and   transitioning the wireless device back from the authentication mode to the standby mode.   
     
     
       32. The method of claim 31, wherein said adjusting the frequency of the local oscillator comprises:
 determining a difference between timing states of a plurality of commands received from the external unit.   
     
     
       33. The method of claim of 32, wherein said adjusting the frequency of the local oscillator comprises:
 adjusting the frequency of the local oscillator based on a determination that the difference between the timing states of the plurality of commands is greater than a predetermined threshold value.   
     
     
       34. The method of claim 31, wherein the wireless device is a cordless telephone. 
     
     
       35. The method of claim 34, wherein the external unit is a matching base unit.