Source: https://patents.google.com/patent/US8964523B2/en
Timestamp: 2019-05-24 13:37:43
Document Index: 589720326

Matched Legal Cases: ['Application No. 60', 'art.\n3', 'art.\n13', 'art.\n26', 'art.\n33', 'art 16', 'Application No. 201080039485']

US8964523B2 - Scattered pilot pattern and channel estimation method for MIMO-OFDM systems - Google Patents
US8964523B2
US8964523B2 US13/765,523 US201313765523A US8964523B2 US 8964523 B2 US8964523 B2 US 8964523B2 US 201313765523 A US201313765523 A US 201313765523A US 8964523 B2 US8964523 B2 US 8964523B2
US13/765,523
US20130223553A1 (en
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This application is a continuation of U.S. application Ser. No. 13/586,660, filed on Aug. 15, 2012, which is itself is a continuation of U.S. application Ser. No. 12/468,624, filed on May 19, 2009, and issued as U.S. Pat. No. 8,254,246 on Aug. 28, 2012, which is itself a continuation of U.S. application Ser. No. 11/819,690, filed on Jun. 28, 2007 and issued as U.S. Pat. No. 7,545,734 on Jun. 9, 2009, which is itself a continuation of U.S. application Ser. No. 10/038,883, filed on Jan. 8, 2002, which has issued as U.S. Pat. No. 7,248,559 on Jul. 24, 2007, and claims the benefit thereof, which itself claims the benefit of U.S. Provisional Application No. 60/329,509 filed Oct. 17, 2001, the contents of which are incorporated in its entirety herein by reference.
[ H 11 H 21 ] = 1  P 1  2 +  P 2 ⁢  2 ⁡ [ P 1 * - P 2 P 2 * P 1 ⁢ ] ⁡ [ Y 1 , 1 Y 1 , 2 ]
[ H 12 H 22 ] = 1  P 1  2 +  P 2  2 ⁡ [ P 1 * - P 2 P 2 * P 1 ⁢ ] ⁡ [ Y 2 , 1 Y 2 , 2 ]
where k=3, . . . , 2Npilot−2. It is to be understood that other filtering algorithms may be employed.
In some embodiments, every OFDM symbol contains some pilot insertion points and as such this completes the interpolation process. In other embodiments, there are some OFDM symbols which do not have any pilot insertion points.
To get channel estimates for these OFDM symbols, an interpolation in time of the previously computed channel estimates is performed. In high mobility applications, pilots should be included in every OFDM symbol avoiding the need for this last interpolation in time step.
1. A method of inserting pilot symbols into Orthogonal Frequency Division Multiplexing (OFDM) frames at an OFDM base station having at least one transmitting antenna, the OFDM base station having an adjacent OFDM base station having at least one transmitting antenna, the OFDM frames having a time domain and a frequency domain, each OFDM frame comprising a plurality of OFDM symbols in the time domain and a plurality of sub-carriers in the frequency domain, the method comprising:
for each transmitting antenna of the OFDM base station, inserting scattered pilot symbols in a scattered pattern in time-frequency, wherein the scattered pattern is offset from a scattered pattern of the adjacent OFDM base station.
2. The method according to claim 1, wherein the scattered pattern in time-frequency includes a first plurality of pilot symbols, each pilot symbol of the first plurality of pilot symbols spaced six sub-carriers apart.
3. The method according to claim 2, wherein the scattered pattern in time-frequency includes a second plurality of pilot symbols, each pilot symbol of the second plurality of pilot symbols spaced six sub-carriers apart, the second plurality of pilot symbols offset from the first plurality of pilot symbols by three sub-carriers.
4. The method according to claim 3, wherein the second plurality of pilot symbols is offset in time from the first plurality of pilot symbols.
5. The method according to claim 1, wherein the scattered pattern is a diagonal-shaped lattice.
6. The method according to claim 5, wherein for each antenna, inserting pilot symbols in an diagonal-shaped lattice comprises for each point in the diagonal shaped lattice inserting a number of pilot symbols on a single sub-carrier for N consecutive OFDM symbols, where N is the number of transmitting antennas.
7. The method according to claim 6, wherein the diagonal shaped lattice is a diamond shaped lattice.
8. The method of claim 7 further comprising transmitting the pilot symbols with a power level which is dynamically adjusted as a function of a modulation type applied to the sub-carriers carrying data.
9. The method according to claim 6 wherein N>1, further comprising for each point in the diagonal-shaped lattice:
performing space time block coding (STBC) on the group of L uncoded pilot symbols to produce an N×N STBC block, L and N determining an STBC code rate; and
10. The method according to claim 5, wherein the diagonal shaped lattice pattern comprises:
a first plurality of equally spaced sub-carrier positions; and
an Orthogonal Frequency Division Multiplexing (OFDM) base station having at least one transmit antenna; and
an adjacent OFDM base station having at least one transmit antenna; the OFDM base station being adapted to insert pilot symbols into OFDM frames having a time domain and a frequency domain, each OFDM frame comprising a plurality of OFDM symbols in the time domain and a plurality of sub-carriers in the frequency domain, by, for each antenna, inserting pilot symbols in a scattered pattern in time-frequency, wherein the scattered pattern is offset from a scattered pattern of the adjacent OFDM base station.
12. The system according to claim 11, wherein the scattered pattern in time-frequency includes a first plurality of pilot symbols, each pilot symbol of the first plurality of pilot symbols spaced six sub-carriers apart.
13. The system according to claim 12, wherein the scattered pattern in time-frequency includes a second plurality of pilot symbols, each pilot symbol of the second plurality of pilot symbols spaced six sub-carriers apart, the second plurality of pilot symbols offset from the first plurality of pilot symbols by three sub-carriers.
14. The system according to claim 13, wherein the second plurality of pilot symbols is offset in time from the first plurality of pilot symbols.
15. The system according to claim 11, wherein the scattered pattern is a diagonal-shaped lattice.
16. The system according to claim 11, wherein for each antenna, inserting pilot symbols in an scattered pattern comprises for each point in the scattered pattern inserting a number of pilot symbols on a single sub-carrier for N consecutive OFDM symbols, where N is the number of transmitting antennas, where N>=1.
17. The system according to claim 16, wherein the scattered pattern is a diamond shaped lattice.
18. The system according to claim 11, wherein N>1, further adapted to, for each point in the scattered pattern:
perform space time block coding (STBC) on the group of L pilot symbols to produce an N×N STBC block; and
19. The system according to claim 18, wherein the scattered pattern is a diamond-shaped lattice.
20. The system according to claim 11, wherein the pilot symbols are transmitted with a power level greater than a power level of data symbols.
21. The system according to claim 20, wherein the pilot symbols are transmitted with a power level greater than a power level of data symbols depending on a value reflective of channel conditions.
22. A method of receiving pilot symbols in Orthogonal Frequency Division Multiplexing (OFDM) frames at an OFDM receiver having at least one receiving antenna from an OFDM base station having at least one transmitting antenna, the OFDM base station having an adjacent OFDM base station having at least one transmitting antenna, the OFDM frames having a time domain and a frequency domain, each OFDM frame comprising a plurality of OFDM symbols in the time domain and a plurality of sub-carriers in the frequency domain, the method comprising:
receiving scattered pilot symbols in a scattered pattern in time-frequency for each transmitting antenna, wherein the scattered patterns is offset from a scattered pattern of the adjacent OFDM base station.
23. The method according to claim 22, further comprising estimating a plurality of channel responses at the OFDM receiver by:
using the pilot symbols of the received OFDM frames to estimate a channel response for each point in the scattered pattern; and
estimating the channel response of a plurality of points not on the scattered pattern by performing interpolation of channel responses determined for points in the scattered pattern.
24. The method according to claim 23, further comprising for each transmitting antenna, receiving antenna combination:
performing an interpolation in the frequency direction to estimate the channel responses corresponding to remaining OFDM sub-carriers within each OFDM symbol.
25. The method according to claim 23, wherein the scattered pattern in time-frequency includes a first plurality of pilot symbols, each pilot symbol of the first plurality of pilot symbols spaced six sub-carriers apart.
26. The method according to claim 25, wherein the scattered pattern in time-frequency includes a second plurality of pilot symbols, each pilot symbol of the second plurality of pilot symbols spaced six sub-carriers apart, the second plurality of pilot symbols offset from the first plurality of pilot symbols by three sub-carriers.
27. The method according to claim 26, wherein the second plurality of pilot symbols is offset in time from the first plurality of pilot symbols.
28. The method according to claim 22, wherein the scattered pattern is a diagonal-shaped lattice.
29. An OFDM receiver configured to receive pilot symbols in OFDM frames, comprising:
at least one receiving antenna configured to receive communications from an OFDM base station having at least one transmitting antenna, the OFDM base station having an adjacent OFDM base station having at least one transmitting antenna, the OFDM frames having a time domain and a frequency domain, each OFDM frame comprising a plurality of OFDM symbols in the time domain and a plurality of sub-carriers in the frequency domain; and
one or more processors configured to receive scattered pilot symbols in a scattered pattern in time-frequency for each transmitting antenna, wherein the scattered patterns is offset from a scattered pattern of the adjacent OFDM base station.
30. The OFDM receiver of claim 29, the one or more processors further configured to estimate a plurality of channel responses by:
for each transmitting antenna-receiving antenna combination:
31. The OFDM receiver of claim 30, the one or more processors further configured to, for each transmitting antenna-receiving antenna combination, perform an interpolation in the frequency direction to estimate the channel responses corresponding to remaining OFDM sub-carriers within each OFDM symbol.
32. The OFDM receiver of claim 30, wherein the scattered pattern in time-frequency includes a first plurality of pilot symbols, each pilot symbol of the first plurality of pilot symbols spaced six sub-carriers apart.
33. The OFDM receiver of claim 32, wherein the scattered pattern in time-frequency includes a second plurality of pilot symbols, each pilot symbol of the second plurality of pilot symbols spaced six sub-carriers apart, the second plurality of pilot symbols offset from the first plurality of pilot symbols by three sub-carriers.
34. The OFDM receiver of claim 33, wherein the second plurality of pilot symbols is offset in time from the first plurality of pilot symbols.
35. The OFDM receiver of claim 29, wherein the scattered pattern is a diagonal-shaped lattice.
36. The OFDM receiver of claim 29, the one or more processors further configured to estimate a plurality of channel responses using the received scattered pilot symbols.
37. The method according to claim 22, further comprising estimating a plurality of channel responses at the OFDM receiver using the received scattered pilot symbols.
US13/765,523 2001-10-17 2013-02-12 Scattered pilot pattern and channel estimation method for MIMO-OFDM systems Active 2022-06-27 US8964523B2 (en)
US13/586,660 Continuation US8406118B2 (en) 2001-10-17 2012-08-15 Scattered pilot pattern and channel estimation method for MIMO-OFDM systems
US14/249,127 Continuation US8971169B2 (en) 2001-10-17 2014-04-09 Scattered pilot pattern and channel estimation method for MIMO-OFDM systems
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