Robust packet detection, symbol timing, channel length estimation and channel response estimation for wireless systems

• US 7,965,798 B2
• Filed: 08/13/2007
• Issued: 06/21/2011
• Est. Priority Date: 08/16/2006
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Roh, June Chul, Batra, Anuj, Singh, Manoneet, Balakrishnan, Jaiganesh
• Primary Examiner(s): Ahn; Sam K
• Application Number:
  US11/893,050
• Publication Number:
  US 20090028220A1
• Time in Patent Office: 1,408 Days
• Field of Search: 375/142, 375/143, 375/150, 375/152, 375/343, 704/216, 704/218, 704/237, 704/263, 708/5, 708/422, 708/813, 342/108, 342/145, 342/189, 342/378, 370/342, 370/218, 370/473, 370/497, 455/3.02, 455/3.05
• US Class Current: 375/343
• CPC Class Codes: H04B 17/327 Received signal code power [RSCP]
• CPC Class Codes: H04L 25/0216 with estimation of channel length
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• CPC Class Codes: H04L 27/2656 Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or known symbols

Abstract

A method. The method includes producing a first signal match indication based on at least one match indication indicative of a match between at least one signal received in at least one band and a reference signal. The method also includes producing a first signal multipath combined signal based upon the first signal match indication, and detecting a first peak in the first multipath combined signal.

Claims

1. An apparatus for robust packet detection in a packet-based wireless system, the apparatus comprising:

a matched filter that is to produce at least one match indication indicative of a match between at least one signal received in at least one band and a reference signal, the at least one signal includes a first signal and a second signal, and the at least one band includes a first band and a second band;

a multipath combiner that is to produce at least one multipath combined signal based upon the at least one match indication;

wherein the at least one match indication includes a first match indication based on the first signal received in the first band and a second signal indication based on the second signal received in the second band, the least one multipath combined signal includes a first multipath combined signal and a second multipath combined signal, the first multipath combined based upon the first match indication, the second multipath combined signal based upon the second match indication;

memory that is to store the first multipath combined signal;

a per sample averaging unit that is to produce an average multipath combined signal based upon a per sample average of the first multipath combined signal and the second multipath combined signal; and

a peak detector that is to identify a first peak in the average multipath combined signal to determine whether a packet reception is occurring.

2. The apparatus of claim 1, wherein the matched filter is a single-stage matched filter comprising an array of multipliers that stores values for a reference signal.

3. The apparatus of claim 1, wherein, the matched filter is a two-stage matched filter comprising a first array of multipliers that stores values for a base sequence and a second array of multipliers that stores values for a spreading sequence.

4. The apparatus of claim 1, wherein the multipath combiner comprises an M-tap delay line and a summer, and is to pass samples of the first signal match indication through the M-tap delay line to produce M-tap outputs for the summer to add to produce the first signal multipath combined signal, wherein M is an integer.

5. The apparatus of claim 1, wherein the multipath combiner comprises an M-tap delay line, a largest K of M selector, and a summer, and is to pass samples of the first signal match indication through the M-tap delay line to produce M-tap outputs, the largest K of M selector is to select the K largest values of the M-tap outputs for the summer to add to produce the first signal multipath combined signal, wherein K and M are integers and K is less than M.

6. The apparatus of claim 1, further comprising a control logic that is to set a rising threshold (rise_th), a falling threshold (fall_th) and a multipath combining threshold (mpc_th) based upon channel conditions for the peak detector to use to detect the first peak.

7. The apparatus of claim 1, wherein the first peak has an associated first peak power and the peak detector is to determine whether the first peak power exceeds a first threshold.

8. The apparatus of claim 7, wherein, as a consequence of determining that the first peak power exceeds a first threshold, a multiband combiner is to determine that the packet reception is occurring.

9. The apparatus of claim 8, wherein the first peak has a first peak sample index, further comprising control logic that is to determine a timing index based upon the first peak sample index;

and is to adjust timing based upon the timing index.

10. The apparatus of claim 8, wherein the first peak has an associated first peak sample index, further comprising control logic that is to determine a timestamp based upon the first peak sample index.

11. The apparatus of claim 10, wherein the control logic is to determine, based upon the determined timestamp, a starting sample index for samples of a symbol for which an FFT is to be performed.

12. The apparatus of claim 1, wherein the apparatus comprises an ultra-wide band frequency hopping receiver.

13. The apparatus of claim 1, wherein the apparatus comprises a multimedia device.

14. The apparatus of claim 1, further comprising, control logic that is to identify in the first multipath combined signal a sample indicative of a falling edge, the sample having an associated falling edge index;

is to determine a timestamp based upon the falling edge index and a length of the multipath combiner that produced the first multipath combined signal, is to determine a rising edge index based upon the timestamp, and is to determine a channel length estimate based upon the timestamp and the rising edge index.

15. The apparatus of claim 14, wherein the first peak has an associated first peak power, and the peak detector is to determine whether the first peak power exceeds a first threshold.

16. The apparatus of claim 15, wherein the control logic identifies the sample indicative of a falling edge when the first peak power exceeds a first threshold.

17. The apparatus of claim 14, wherein the control logic is to set for an overlap-and-add unit an overlap-and-add length based upon the channel length estimate.

18. The apparatus of claim 14, wherein the control logic is to select, based upon the channel length estimate, a filter representation for generating a filtered channel response estimate.

19. The apparatus of claim 18, further comprising a channel response estimate filter unit coupled to the control logic and that is to generate the filtered channel response estimate using the selected filter representation and samples of at least one channel estimation symbol.

20. The apparatus of claim 19, wherein the control logic is to also select the filter based upon a signal-to-noise ratio estimate.

21. The apparatus of claim 20, wherein the first multiplier is coupled to the first matched filter and the first multipath combiner and the first weight is applied to samples in the first signal first receive chain match indication to produce a weighted first signal first receive chain match indication for provision to the first multipath combiner.

22. The apparatus of claim 1, wherein the first band is the same as the second band.