Method of determining the location of the FFT window and the delay spread for the platinum broadcast channel estimator

• US 7,609,773 B2
• Filed: 06/29/2005
• Issued: 10/27/2009
• Est. Priority Date: 04/18/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Black, Peter J., Bhushan, Naga, Namgoong, June
• Primary Examiner(s): Tran; Khanh C
• Application Number:
  US11/174,108
• Publication Number:
  US 20060233269A1
• Time in Patent Office: 1,581 Days
• Field of Search: 375/148, 375/150, 375/260, 375/285, 375/324, 375/326, 375/340, 375342-343, 375/355
• US Class Current: 375/260
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2665 Fine synchronisation, e.g. by positioning the FFT window

Abstract

In one embodiment, the invention comprises a channel estimation method, comprising determining a FFT window position, and calculating a delay spread. In another embodiment, the step of determining a FFT window position comprises setting an initial position of the FFT window, computing an energy for each tap, time averaging said energy for each tap, comparing an average energy of each tap with a first threshold multiplied by the average energy of all taps, comparing the average energy of each tap with a second threshold multiplied by a maximum average energy in alias components, updating the set of paths if the average energy of the tap is greater than said second threshold multiplied by the maximum average energy in alias components; and refining the FFT window position.

Claims

1. A channel estimation method, comprising:

receiving an RF signal in an RF receiver;

downconverting the received RF signal to obtain a received IF signal in an IF receiver;

converting the received IF signal into a digital signal in an analog to digital converter;

determining a FFT window position of the converted digital signal in a digital signal processor; and

calculating a delay spread, wherein said step of determining a FFT window position comprises;

setting an initial position of said FFT window;

computing an energy for each tap;

time averaging said energy for each said tap;

comparing an average energy of each said tap with a first threshold;

comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components;

updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and

defining said FFT window position.

2. The method according to claim 1 ,wherein said step of comparing an average energy of each said tap with a first threshold comprises:

comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps.

3. The method according to claim 1, wherein said step of comparing an average energy of each said tap with a first threshold comprises:

comparing said average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps.

4. The method according to claim 1, wherein said-step of comparing an average energy of each said tap with a first threshold comprises:

comparing said average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps.

5. The method according to claim 1, wherein said step of setting an initial position of an FFT window comprises:

backing off from an earliest arriving path;

defining an index of a first component of an estimated channel response;

defining an index of a last component of an estimated channel response; and

calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response.

6. The method according to claim 1, wherein said step of defining said FFT window position comprises:

defining an earliest path location;

defining a latest path location;

setting a starting point of said FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and

setting a starting point of said FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix.

7. The method according to claim 1, wherein said step of computing an energy for each tap comprises squaring absolute values of a channel response for each tap.

8. A channel estimation method, comprising:

receiving an RF signal in an RF receiver;

downconverting the received RF signal to obtain a received IF signal in an IF receiver;

converting the received IF signal into a digital signal in an analog to digital converter;

determining a FFT window position of the converted digital signal in a digital signal processor; and

calculating a delay spread, wherein said step of determining a FFT window position comprises;

setting an initial position of said FFT window;

computing an energy for each tap;

time averaging said energy for each said tap;

comparing an earliest path hypothesis for each said tap with a first threshold multiplied by a mean average energy over all said taps;

comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components;

updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and

defining said FFT window position.

9. A receiver to estimate a channel, comprising:

an RF receiver having an input and an output;

an IF receiver having an input and an output, wherein said input is operably connected to an output of said RF receiver;

an analog-to-digital converter having an input and an output, wherein said input is operably connected to said output of said IF receiver;

a decoder having an input and an output; and

a processor having an input and an output, wherein said input is operably connected to said output of said analog-to-digital converter and said output is operably connected to said input of said decoder and said processor comprises

memory, and

software comprising instructions stored in said memory,

wherein said receiver is adapted to execute said instructions stored in said memory comprising

determining a FFT window position; and

calculating a delay spread, wherein said determining a FFT window position instruction comprises;

setting an initial position of said FFT window;

computing an energy for each tap;

time averaging said energy for each said tap;

comparing an average energy of each said tap with a first threshold;

comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components;

updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and

defining said FFT window position.

10. The receiver according to claim 9, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps.

11. The receiver according to claim 9, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing said average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps.

12. The receiver according to claim 9, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing said average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps.

13. The receiver according to claim 9, wherein said setting an initial position of an FFT window instruction comprises:

backing off from an earliest arriving path;

defining an index of a first component of an estimated channel response;

defining an index of a last component of an estimated channel response; and

calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response.

14. The receiver according to claim 9, wherein said defining said FFT window position instruction comprises:

defining an earliest path location;

defining a latest path location;

setting a staffing point of the FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and

setting a staffing point of the FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix.

15. The receiver according to claim 9, wherein said computing an energy for each tap instruction comprises squaring absolute values of a channel response for each tap.

16. A receiver to estimate a channel, comprising:

an RF receiver having an input and an output;

an IF receiver having an input and an output, wherein said input is operably connected to an output of said RF receiver;

an analog-to-digital converter having an input and an output, wherein said input is operably connected to said output of said IF receiver;

a decoder having an input and an output; and

a processor having an input and an output, wherein said input is operably connected to said output of said analog-to-digital converter and said output is operably connected to said input of said decoder and said processor comprises

memory, and

software comprising instructions stored in said memory,

wherein said receiver is adapted to execute said instructions stored in said memory comprising;

determining a FFT window position; and

calculating a delay spread, wherein said determining a FFT window position instruction comprises;

setting an initial position of an FFT window;

computing an energy for each tap;

time averaging said energy for each said tap;

comparing an earliest path hypothesis for each said tap with a first threshold multiplied by a mean average energy of all said taps;

comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components;

updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and

defining said FFT window position.

17. A processor to estimate a channel, comprising:

memory; and

software comprising instructions stored in said memory, wherein said processor is adapted to execute said instructions stored in said memory comprising

determining a FFT window position; and

calculating a delay spread, wherein said determining a FFT window position instruction comprises;

setting an initial position of said FFT window;

computing an energy for each tap;

time averaging said energy for each said tap;

comparing an average energy of each said tap with a first threshold;

comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components;

updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and

defining said FFT window position.

18. The processor according to claim 17, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps.

19. The processor according to claim 17, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing said average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps.

20. The processor according to claim 17, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing said average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps.

21. The processor according to claim 17, wherein said setting an initial position of an FFT window instruction comprises:

backing off from an earliest arriving path;

defining an index of a first component of an estimated channel response;

defining an index of a last component of an estimated channel response; and

calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response.

22. The processor according to claim 17, wherein said defining said FFT window position instruction comprises:

defining an earliest path location;

defining a latest path location;

setting a staffing point of the FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and

setting a staffing point of the FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix.

23. The processor according to claim 17, wherein said computing an energy for each tap instruction comprises squaring absolute values of a channel response for each tap.

24. A processor to estimate a channel, comprising:

memory; and

software comprising instructions stored in said memory, wherein said processor is adapted to execute said instructions stored in said memory comprising

determining a FFT window position; and

calculating a delay spread, wherein said determining a FFT window position instruction comprises;

setting an initial position of said FFT window;

computing an energy for each tap;

time averaging said energy for each said tap;

comparing an earliest path hypothesis for each said tap with a first threshold multiplied by a mean average energy over all said taps;

comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components;

updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and

defining said FFT window position.

25. A receiver means to estimate a channel, comprising:

an RF receiver means having an input and an output;

an IF receiver means having an input and an output, wherein said input is operably connected to an output of said RF receiver means;

an analog-to-digital converter means having an input and an output, wherein said input is operably connected to said output of said IF receiver means;

a decoder means having an input and an output; and

a processor means having an input and an output, wherein said input is operably connected to said output of said analog-to-digital converter means and said output is operably connected to said input of said decoder means and said processor means comprises

memory means, and

software comprising instructions stored in said memory means, wherein said receiver means is adapted to execute said instructions stored in said memory means comprising

determining a FFT window position; and

calculating a delay spread, wherein said determining a FFT window position instruction comprises;

setting an initial position of said FFT window;

computing an energy for each tap;

time averaging said energy for each said tap;

comparing an average energy of each said tap with a first threshold

comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components;

updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and

defining said FFT window position.

26. The receiver means according to claim 25, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps.

27. The receiver means according to claim 25, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing said average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps.

28. The receiver means according to claim 25, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing said average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps.

29. The receiver means according to claim 25, wherein said setting an initial position of an FFT window instruction comprises:

backing off from an earliest arriving path;

defining an index of a first component of an estimated channel response;

defining an index of a last component of an estimated channel response; and

calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response.

31. The receiver means according to claim 25, wherein said computing an energy for each tap instruction comprises squaring absolute values of a channel response for each tap.

30. The receiver means according to claim, wherein said defining said FFT window position instruction comprises:

defining an earliest path location;

defining a latest path location;

setting a starting point of said FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and

setting a starting point of said FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix.

32. A receiver means to estimate a channel, comprising:

an RF receiver means having an input and an output;

an IF receiver means having an input and an output, wherein said input is operably connected to an output of said RF receiver means;

an analog-to-digital converter means having an input and an output, wherein said input is operably connected to said output of said IF receiver means;

a decoder means having an input and an output; and

a processor means having an input and an output, wherein said input is operably connected to said output of said analog-to-digital converter means and said output is operably connected to said input of said decoder means and said processor means comprises

memory means, and

software comprising instructions stored in said memory means, wherein said receiver means is adapted to execute said instructions stored in said memory means comprising

determining a FFT window position; and

calculating a delay spread, wherein said determining a FFT window position instruction comprises;

setting an initial position of said FFT window;

computing an energy for each tap;

time averaging said energy for each said tap;

comparing an earliest path hypothesis for each said tap with a first threshold multiplied by a mean average energy over all said taps;

comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components;

updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and

defining said FFT window position.

33. A processor means to estimate a channel, comprising:

memory means; and

software comprising instructions stored in said memory means, wherein said processor means is adapted to execute said instructions stored in said memory means comprising

determining a FFT window position; and

calculating a delay spread, wherein said determining a FFT window position instruction comprises;

setting an initial position of said FFT window;

computing an energy for each tap;

time averaging said energy for each said tap;

comparing an average energy of each said tap with a first threshold;

comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components;

updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and

defining said FFT window position.

34. The processor means according to claim 33, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps.

35. The processor means according to claim 33, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing said average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps.

36. The processor means according to claim 33, wherein said comparing an average energy of each said tap with a first threshold comprises:

comparing said average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps.

38. The processor means according to claim 33, wherein said setting an initial position of an FFT window instruction comprises:

backing off from an earliest arriving path;

defining an index of a first component of an estimated channel response;

defining an index of a last component of an estimated channel response; and

calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response.

39. The processor means according to claim 33, wherein said defining said FFT window position instruction comprises:

defining an earliest path location;

defining a latest path location;

setting a starting point of the FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and

setting a starting point of the FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix.

40. The processor means according to claim 33, wherein said computing an energy for each tap instruction comprises squaring absolute values of a channel response for each tap.

37. A processor means to estimate a channel, comprising:

memory means; and

software comprising instructions stored in said memory means, wherein said processor means is adapted to execute said instructions stored in said memory means comprising

determining a FFT window position; and

calculating a delay spread, wherein said determining a FFT window position instruction comprises;

setting an initial position of said FFT window;

computing an energy for each tap;

time averaging said energy for each said tap;

comparing an earliest path hypothesis for each said tap with a first threshold multiplied by a mean average energy over all said taps;

comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components;

updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and

defining said FFT window position.

41. A storage medium having stored thereon processor-executable software instructions configured to cause a processor to perform steps comprising:

determining a FFT window position; and

calculating a delay spread, wherein said step of determining a FFT window position comprises;

setting an initial position of said FFT window;

computing an energy for each tap;

time averaging said energy for each said tap;

comparing an average energy of each said tap with a first threshold;

comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components;

updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and

defining said FFT window position.

42. The storage medium of claim 41, wherein comparing an average energy of each said tap with a first threshold comprises comparing an average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps.

43. The storage medium of claim 41, wherein comparing an average energy of each said tap with a first threshold comprises comparing an average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps.

44. The storage medium of claim 41, wherein comparing an average energy of each said tap with a first threshold comprises comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps.

45. The storage medium of claim 41, wherein the stored processor-executable software instructions are configured to cause a processor to perform further steps comprising:

backing off from an earliest arriving path;

defining an index of a first component of an estimated channel response;

defining an index of a last component of an estimated channel response; and

calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response.

46. The storage medium of claim 41, wherein the stored processor-executable software instructions are configured to cause a processor to perform further steps comprising:

defining an earliest path location;

defining a latest path location;

setting a starting point of said FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and

setting a starting point of said FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix.

47. The storage medium of claim 41, wherein the stored processor-executable software instructions are configured to cause a processor to perform further steps comprising:

squaring absolute values of a channel response for each tap.