System and method for signal synchronization in a communication system

Abstract

A system and method for information content-independent synchronization with a received signal. A variable of the signal (e.g., average energy or magnitude) which is related to the energy distribution, is measured over a period of time. The signal's information bearing point is found at the point within the information period of the signal with the highest averaged energy. The point may be found, for example, by detecting the sample point with highest average energy, or by correlating multiple sample points to a stored template. Interpolation may be performed to locate an information bearing point that is between sample points. Because the relative energy content of the signal is effectively independent of the specific information content, synchronization with the information bearing point is accomplished without requiring the insertion of any special information content or fixed content patterns into the signal.

1. A method for synchronizing with a transmitted signal, said method comprising:
 receiving said transmitted signal, wherein said transmitted signal comprises a periodic information bearing point at an information rate and wherein an information period is the inverse of said information rate; 
 sampling said received signal at sample points at a sampling rate greater than said information rate, wherein a sample period is the inverse of said sampling rate; 
 filtering said sampled signal with a pulse-shaping filter; 
 measuring a variable of said filtered signal at said sample points, wherein said variable is independent of information content in said received signal; 
 determining the location of said information bearing point in said filtered signal based on said information content-independent variable; and 
 synchronizing said filtered signal with said information bearing point, 
 wherein said determining said location of said information bearing point comprises using a highest average energy point in said filtered signal as said information bearing point, and wherein said highest average energy point occurs between two of said sample points, and said determining said location of said information bearing point further comprises interpolating between sample points, and 
 wherein said interpolating is performed using a quadratic equation fit on three of said sample points having three highest average energy values. 
 
     
     
       2. The method of  claim 1 , wherein said information content-independent variable is indicative of an average energy distribution of said received signal. 
     
     
       3. The method of  claim 2 , wherein said variable in an average energy. 
     
     
       4. The method of  claim 3 , wherein said filtered signal comprises an in-phase (I) component and a quadrature-phase (O) component, and wherein said average energy is calculated from a sum of the squares of said I and Q components. 
     
     
       5. The method of  claim 2 , wherein said variable is an average magnitude. 
     
     
       6. The method of  claim 1 , wherein said determining step further comprises using template matching over multiple sample points to locate said information bearing point. 
     
     
       7. The method of  claim 1 , wherein said information bearing point represents a symbol of information. 
     
     
       8. The method of  claim 1 , wherein said pulse-shaping filter meets Nyquist criteria. 
     
     
       9. The method of  claim 8 , wherein said pulse-shaping filter is part of a pair of matched filters. 
     
     
       10. The method of  claim 1 , wherein part of said filtering is performed before said receiving. 
     
     
       11. The method of  claim 1 , wherein said synchronizing is performed at signal acquisition. 
     
     
       12. The method of  claim 1 , wherein said synchronizing with said transmitted signal is performed continuously while said transmitted signal is being received. 
     
     
       13. The method of  claim 1 , wherein said transmitted signal is a wireless radio frequency signal. 
     
     
       14. A method for synchronizing with a transmitted signal, said method comprising:
 receiving said transmitted signal, wherein said transmitted signal comprises a periodic information bearing point at an information rate and wherein an information period is the inverse of said information rate; 
 sampling said received signal at sample points at a sampling rate greater than said information rate, wherein a sample period is the inverse of said sample rate; 
 filtering said sampled signal with a pulse-shaping filter; 
 measuring a variable of said filtered signal at said sample points, wherein said variable is independent of information content in said filtered signal; 
 determining the location of said information bearing point in said filtered signal based on said information content-independent variable; and 
 synchronizing said filtered signal with said information bearing point, wherein multiple values of said variable are collected over a period of time and accumulated in sample bins, 
 wherein each respective sample bin represents a respective sample point collected at the same relative sample location within each said information period, and 
 wherein said sampling rate is 52 kHz, said information rate is 4 kHz, having 13 of said sample periods per said information period, and having 13 of said sample bins. 
 
     
     
       15. A method for synchronizing with a transmitted signal, said method comprising:
 receiving said transmitted signal, wherein said transmitted signal comprises a periodic symbol point having a symbol rate; 
 sampling said received signal at sample points having a sample rate greater than said symbol rate; 
 filtering said sampled signal with a pulse-shaping filter; 
 determining an energy level of each of said sample points; 
 averaging said energy level of said sample points over time based on a symbol period; 
 determining the location of said symbol point in said received signal based on said average energy level, wherein said average energy level is an information content-independent variable; and 
 synchronizing said received signal with said symbol point, 
 wherein said determining said location of said symbol point comprises interpolating using a quadratic equation fit based on three sample points having a highest average power. 
 
     
     
       16. The method of  claim 15 , wherein magnitude of said sample points is used to determine said energy level. 
     
     
       17. The method of  claim 15 , wherein power of said sample points is used to determine said energy level. 
     
     
       18. The method of  claim 15 , wherein said determining said location of said symbol point comprises selecting the sample point having a highest average energy level. 
     
     
       19. A synchronization method comprising:
 filtering a sampled signal with a pulse-shaping filter to obtain a filtered signal, the signal containing a periodic information bearing point at an information rate, the sampled signal being sampled at sample points at a sample rate greater than the information rate;   measuring a quantity associated with said filtered signal at said sample points, wherein said quantity is independent of information content in said signal; and   determining the location of said information bearing point in said filtered signal based on said information content-independent quantity;   wherein said determining said location of said information bearing point comprises using a highest average energy point in said filtered signal as said information bearing point, and wherein said highest average energy point occurs between two of said sample points, and said determining said location of said information bearing point further comprises interpolating between sample points, and wherein said interpolating is performed using a quadratic equation fit on three of said sample points having three highest average energy values.    
     
     
       20. The method of claim 19, wherein said information content-independent quantity is indicative of an average energy distribution of said received signal.  
     
     
       21. The method of claim 20, wherein said quantity is an average magnitude.  
     
     
       22. The method of claim 19, wherein said determining further comprises using template matching over multiple sample points to locate said information bearing point.  
     
     
       23. The method of claim 19, wherein said information bearing point represents a symbol of information.  
     
     
       24. The method of claim 19, wherein said pulse-shaping filter is a Nyquist filter. 
     
     
       25. The method of claim 24, wherein said pulse-shaping filter is part of a pair of matched filters.  
     
     
       26. The method of claim 19, further comprising acquiring said signal, and wherein synchronization is performed at signal acquisition.  
     
     
       27. The method of claim 19, wherein said signal is a wireless radio frequency signal.  
     
     
       28. A synchronization method comprising:
 filtering a sampled signal with a pulse-shaping filter to obtain a filtered signal, the signal containing a periodic symbol point at a symbol rate, the sampled received signal being sampled at sample points at a sample rate greater than the symbol rate;   determining an energy level of each of said sample points;   averaging said energy level of said sample points over time based on a symbol period; and   determining the location of said symbol point in said signal based on said average energy level, wherein said average energy level is an information content-independent quantity, and wherein said determining said location of said symbol point comprises interpolating using a quadratic equation fit based on three sample points having highest average energy levels.    
     
     
       29. The method of claim 28, further comprising using magnitudes of said sample points to determine said energy level.  
     
     
       30. The method of claim 28, further comprising using power of said sample points to determine said energy level.  
     
     
       31. The method of claim 28, wherein said determining said location of said symbol point comprises selecting the sample point having a highest average energy level.  
     
     
       32. A non-transitory processor-readable medium embodying processor-executable instructions that, upon execution by a processor, cause the processor to implement synchronization operations comprising:
 filtering a sampled signal with a pulse-shaping filter to obtain a filtered signal, the signal containing a periodic information bearing point at an information rate, the sampled signal being sampled at sample points at a sample rate greater than the information rate;   measuring a quantity associated with said filtered signal at said sample points, wherein said quantity is independent of information content in said signal; and   determining the location of said information bearing point in said filtered signal based on said information content-independent quantity;   wherein said determining said location of said information bearing point comprises using a highest average energy point in said filtered signal as said information bearing point, and wherein said highest average energy point occurs between two of said sample points, and said determining said location of said information bearing point further comprises interpolating between sample points, and wherein said interpolating is performed using a quadratic equation fit on three of said sample points having three highest average energy values.    
     
     
       33. The medium of claim 32, wherein said information content-independent quantity is indicative of an average energy distribution of said received signal.  
     
     
       34. The medium of claim 32, wherein said quantity is an average magnitude.  
     
     
       35. The medium of claim 32, wherein said determining further comprises using template matching over multiple sample points to locate said information bearing point.  
     
     
       36. The medium of claim 32, wherein said information bearing point represents a symbol of information.  
     
     
       37. The medium of claim 32, wherein the further comprise acquiring said signal, and wherein synchronization is performed at signal acquisition.  
     
     
       38. The medium of claim 32, wherein said signal is a wireless radio frequency signal.  
     
     
       39. A non-transitory processor-readable medium embodying processor-executable instructions that, upon execution by a processor, cause the processor to implement synchronization operations comprising:
 filtering a sampled signal with a pulse-shaping filter to obtain a filtered signal, the signal containing a periodic symbol point at a symbol rate, the sampled signal being sampled at sample points at a sample rate greater than the symbol rate;   determining an energy level of each of said sample points;   averaging said energy level of said sample points over time based on a symbol period; and   determining the location of said symbol point in said signal based on said average energy level, wherein said average energy level is an information content-independent quantity, and wherein said determining said location of said symbol point comprises interpolating using a quadratic equation fit based on three sample points having highest average energy levels.    
     
     
       40. The medium of claim 39, wherein the operations further comprise using magnitudes of said sample points to determine said energy level.  
     
     
       41. The medium of claim 39, wherein the operations further comprise using power of said sample points to determine said energy level.  
     
     
       42. The medium of claim 39, wherein said determining said location of said symbol point comprises selecting the sample point having a highest averge energy level.  
     
     
       43. A synchronization apparatus comprising:
 a synchronization unit to measure a quantity for each of a number of sample points of a pulse-shaping filtered sampled signal, wherein the sampled signal contains a periodic information bearing point at an information rate, and wherein the sampled signal is sampled at a sample rate greater than the information rate, the quantity being independent of information content in the signal, and the synchronization unit further to determine the location of the information bearing point in the filtered sampled signal based on the quantity, wherein determining the location of the information bearing point uses a highest average energy point of the filtered signal as the information bearing point, wherein the highest average energy point occurs between sample points, and wherein the synchronization unit is to use interpolation based on a quadratic equation fit on three of the sample points having three highest average energy values.    
     
     
       44. The apparatus claim 43, wherein said information content-independent quantity is indicative of an average energy distribution of said received signal.  
     
     
       45. The apparatus of claim 44, wherein said quantity is an average magnitude.  
     
     
       46. The apparatus of claim 43, wherein said information bearing point represents a symbol of information.  
     
     
       47. The apparatus of claim 43, wherein said signal is a wireless radio frequency signal.  
     
     
       48. A synchronization apparatus comprising:
 a synchronization unit to determine an average energy level over time for each of a number of sample points of a pulse-shaping filtered sampled signal, wherein the sampled signal contains a periodic symbol point at a symbol rate, and wherein the sampled signal is sampled at a sample rate greater than the symbol rate, and the synchronization unit further to determine the location of the symbol point in the filtered sampled signal based on the average energy levels of the sample points by using interpolation based on a quadratic equation fit based on three of said sample points having highest average energy levels.    
     
     
       49. The apparatus of claim 48, wherein said synchronization unit is further to use magnitudes of said sample points to determine said energy level.  
     
     
       50. The apparatus of claim 48, wherein said synchronization unit is further to use power of said sample points to determine said energy level.  
     
     
       51. The apparatus of claim 48, wherein said apparatus is to determine the location of the symbol point in the filtered sampled signal by selecting the sample point having a highest average energy level.