METHODS AND APPARATUS FOR DETERMINING TIMING IN A WIRELESS COMMUNICATION SYSTEM

• US 20100034242A1
• Filed: 10/14/2009
• Published: 02/11/2010
• Est. Priority Date: 10/31/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wang, Michael Mao, Ling, Fuyun, VRCELJ, BOJAN
• Granted Patent: US 8,422,614 B2
• Time in Patent Office: Days
• US Class Current: 375/219
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2676 Blind, i.e. without using known symbols

Abstract

Methods and apparatus for setting timing of sampling of one or more symbols. The disclosed methods account for at least three types of effective interference (EI) and are used to set the timing of a sampling window for sampling received symbols. The methods includes setting timing based on determining an energy density function accounting for both static and dynamic EI, determining the minimum of a total energy profile and sliding the sampling window to ensure that the minimum point is at a predetermined point, and determining and using a composite energy profile accounting for short term and long term fading effects. The disclosed apparatus include a transceiver employing one or more of the disclosed methods for setting timing when receiving the symbols.

Claims

1. A method for setting timing of sampling of one or more symbols comprising:

calculating the total effective interference occurring during a sampling period;

determining a minimum of the calculated total effective interference occurring during the sampling period; and

setting a start of timing of the symbol based on the determined minimum of the total effective interference, wherein the total effective interference includes inter-symbol interference, channel estimation loss and inter-carrier interference.

2. The method as defined in claim 1, wherein setting the start of the timing includes sliding a sampling window responsive to the determined minimum to ensure that a sample where the minimum occurs is set as the start of timing.

3. The method as defined in claim 2, further comprising:

determining whether the determined minimum is one of a positive number and a negative number;

setting the start of timing to a new sample occurring later than a current sample when the determined minimum is positive; and

setting the start of timing to a new sample occurring earlier than the current sample when the determined minimum is negative.

4. The method as defined in claim 1, wherein calculating the total effective interference includes determining an energy density function of static effective interference and dynamic effective interference.

5. The method as defined in claim 1, wherein calculating the total effective interference includes calculating an estimated energy profile of the symbol and determining a product of the energy density function and the estimated energy profile.

6. The method as defined in claim 1, wherein the symbol is configured according to orthogonal frequency division multiplexing (OFDM).

7. A method for setting timing of sampling of one or more symbols comprising:

determining an energy density profile of effective interference occurring in at least one symbol based on static effective interference and a probability of the occurrence of dynamic effective interference, wherein the effective interference includes inter-symbol interference, channel estimation loss and inter-carrier interference; and

setting a start of timing of the symbol based on the determined energy density profile.

8. The method as defined in claim 7, wherein determining the energy density profile further includes:

determining an energy density profile of the static effective interference;

determining a product of the probability and an energy density profile of the dynamic effective interference; and

summing the energy density profile of the static effective interference and the product.

9. The method as defined in claim 8, wherein determining the energy density profile of the static effective interference includes utilizing a known channel symbol profile.

10. The method as defined in claim 9, wherein the known channel symbol profile includes an orthogonal frequency division multiplex (OFDM) symbol.

11. The method as defined in claim 7, wherein the symbol is configured according to orthogonal frequency division multiplexing (OFDM).

12. A method for setting timing of sampling of one or more symbols comprising:

calculating a composite energy profile of the at least one symbol based on an estimated channel energy profile including a summation of a short term channel energy profile and a long term channel energy profile, wherein the composite energy profile includes energy inter-symbol interference, channel estimation loss and inter-carrier interference; and

setting a start of timing of the at least one symbol based on the composite energy profile.

13. The method as defined in claim 12, further comprising:

determining short and long term profiles by low-pass filtering an estimated channel energy profile of the symbol.

14. The method as defined in claim 13, wherein the low-pass filtering of the short and long term profiles is performed with respective first and second effective bandwidths, where the first effective bandwidth is less than the second effective bandwidth.

15. The method as defined in claim 13, further comprising:

multiplying the short and long term profiles by respective first and second weighting factors; and

calculating the composite energy profile by summing the short and long terms profiles after being multiplying by the first and second weighting factors.

16. The method as defined in claim 12, wherein the symbol is configured according to orthogonal frequency division multiplexing (OFDM).

17. A transceiver for use in a wireless communication system comprising:

a sampler configured to sample a received input signal at a set timing offset;

a channel estimator configured to receive the input signal from the sampler and compute an impulse response; and

a timing circuit configured to receive the computed impulse response for a symbol from the channel estimator and to determine timing information based on at least one of a computed effective interference (EI) density function accounting for static and dynamic EI, a sliding adjustment based on a calculated minimum total energy of the symbol, and a composite channel energy profile accounting for long and short term channel fading effects, wherein the calculated minimum total energy of the symbol includes energy from inter-symbol interference, channel estimation loss and inter-carrier interference.

18. The transceiver as defined in claim 17, wherein the timing circuit is configured to provide the timing information to the sampler and the sampler is configured to set the timing offset based on the timing information.

19. An apparatus for setting timing of sampling of one or more symbols in a wireless communication device comprising:

means for calculating the total effective interference occurring during a sampling period;

means for determining a minimum of the calculated total effective interference occurring during the sampling period; and

means for setting a start of timing of the symbol based on the determined minimum of the total effective interference, wherein the total effective interference includes inter-symbol interference, channel estimation loss and inter-carrier interference.

20. The apparatus as defined in claim 19, wherein the means for setting the start of the timing is configured to slide a sampling window responsive to the determined minimum to ensure that a sample where the minimum occurs is set as the start of timing.

21. The apparatus as defined in claim 20, further comprising:

means for determining whether the determined minimum is one of a positive number and a negative number;

means for setting the start of timing to a new sample occurring later than a current sample when the determined minimum is positive; and

means for setting the start of timing to a new sample occurring earlier than the current sample when the determined minimum is negative.

22. The apparatus as defined in claim 19, wherein the means for calculating the total effective interference is configured to determine an energy density function of static effective interference and dynamic effective interference.

23. The apparatus as defined in claim 19, wherein the means for calculating the total effective interference is configured to calculate an estimated energy profile of the symbol and determine a product of the energy density function and the estimated energy profile.

24. The apparatus as defined in claim 19, wherein the symbol is configured according to orthogonal frequency division multiplexing (OFDM).

25. An apparatus for setting timing of sampling of one or more symbols in a wireless device comprising:

means for determining an energy density profile of effective interference occurring in at least one symbol based on static effective interference and a probability of the occurrence of dynamic effective interference; and

means for setting a start of timing of the symbol based on the determined energy density profile.

26. The apparatus as defined in claim 25, wherein the means for determining the energy density profile further includes:

means for determining an energy density profile of the static effective interference;

means for determining a product of the probability and an energy density profile of the dynamic effective interference; and

means for summing the energy density profile of the static effective interference and the product.

27. The apparatus as defined in claim 25, wherein the means for determining the energy density profile of the static effective interference is configured to utilize a known channel symbol profile.

28. The apparatus as defined in claim 27, wherein the known channel symbol profile includes an orthogonal frequency division multiplex (OFDM) symbol.

29. The apparatus as defined in claim 25, wherein the symbol is configured according to orthogonal frequency division multiplexing (OFDM).

30. An apparatus for setting timing of sampling of one or more symbols in a wireless device comprising:

means for calculating a composite energy profile of the at least one symbol based on an estimated channel energy profile including a summation of a short term channel energy profile and a long term channel energy profile, the composite energy profile includes energy from inter-symbol interference, channel estimation loss and inter-carrier interference; and

means for setting a start of timing of the at least one symbol based on the composite energy profile.

31. The apparatus as defined in claim 30, further comprising:

means for determining short and long term profiles by low-pass filtering an estimated channel energy profile of the symbol.

32. The apparatus as defined in claim 30, wherein the low-pass filtering of the short and long term profiles is performed with respective first and second effective bandwidths, where the first effective bandwidth is less than the second effective bandwidth.

33. The apparatus as defined in claim 30, further comprising:

means for multiplying the short and long term profiles by respective first and second weighting factors; and

means for calculating the composite energy profile by summing the short and long terms profiles after being multiplying by the first and second weighting factors.

34. The apparatus as defined in claim 30, wherein the symbol is configured according to orthogonal frequency division multiplexing (OFDM).