Determining responses of rapidly varying MIMO-OFDM communication channels using observation scalars

• US 9,148,311 B2
• Filed: 10/29/2011
• Issued: 09/29/2015
• Est. Priority Date: 10/15/2008
• Status: Active Grant

• Current Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV), STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Karthik, Muralidhar, Vlantis, George A.
• Primary Examiner(s): Liu, Shuwang
• Assistant Examiner(s): TAYONG, HELENE E
• Application Number:
  US13/284,879
• Publication Number:
  US 20120114080A1
• Time in Patent Office: 1,431 Days
• Field of Search: 375/260, 375/259, 375/316, 375/346, 375/350, 375/340
• US Class Current: 1/1
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/03821 Inter-carrier interference cancellation [ICI]
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems

Abstract

In an embodiment, a channel estimator includes first, second, and third stages. The first stage is configurable to generate a first observation scalar for a first communication path of a first communication channel, and the second stage is configurable to generate a second observation scalar for a first communication path of a second communication channel. And the third stage is configurable to generate channel-estimation coefficients in response to the first and second observation scalars. For example, such a channel estimator may use a recursive algorithm, such as a Vector State Scalar Observation (VSSO) Kalman algorithm, to estimate the responses of channels over which propagate simultaneous orthogonal-frequency-division-multiplexed (OFDM) signals (e.g., MIMO-OFDM signals) that suffer from inter-carrier interference (ICI) due to Doppler spread. Such a channel estimator may estimate the channel responses more accurately, more efficiently, with a less-complex algorithm, and with less-complex software or circuitry, than conventional channel estimators.

Claims

1. A Multiple-Input-Multiple-Output (MIMO) channel estimator for MIMO communication with first and second signals respectively over first and second communication channels, the MIMO channel estimator comprising:

a first stage configured to generate a path independent observation scalar for each of the first and second signals based upon pilot subcarriers in the first and second signals;

a second stage configured to generate a path dependent observation scalar for the first and second signals; and

a third stage configured to generate channel-estimation coefficients in response to the path independent and path dependent observation scalars for each of the first and second signals and for the MIMO communication over the first and second communication channels.

2. The MIMO channel estimator of claim 1 wherein the first stage is configured to receive the first signal having a first pilot subcarrier, and to generate the path independent observation scalar in response to first information carried by the first pilot subcarrier;

and wherein the second stage is configured to receive the second signal having a second pilot subcarrier, and to generate the path dependent observation scalar in response to second information carried by the second pilot subcarrier.

3. The MIMO channel estimator of claim 1 wherein the channel-estimation coefficients include a multi-dimensional array of frequency-domain channel-estimation coefficients for the first and second communication channels.

4. The MIMO channel estimator of claim 1 further comprising:

a fourth stage configured to generate a third observation scalar; and

a fifth stage configured to generate a fourth observation scalar, the second stage being configured to generate the channel-estimation coefficients in response to the third and fourth observation scalars.

5. The MIMO channel estimator of claim 1 further comprising:

a fourth stage configured to generate first path-estimation coefficients; and

a fifth stage configured to generate second path-estimation coefficients the third stage being configured to generate the channel-estimation coefficients in response to the first and second path-estimation coefficients.

6. The MIMO channel estimator of claim 5 wherein the first and second path-estimation coefficients each comprises time-domain coefficients;

and wherein the channel-estimation coefficients comprise frequency-domain coefficients.

7. The MIMO channel estimator of claim 1 further including:

a fourth stage configured to generate a third observation scalar;

a fifth stage configured to generate a fourth observation scalar;

a sixth stage configured to generate first path-estimation coefficients in response to the first observation scalar;

a seventh stage configured to generate second path-estimation coefficients in response to the second observation scalar;

an eighth stage configured to generate third path-estimation coefficients in response to the third observation scalar; and

a ninth stage configured to generate fourth path-estimation coefficients in response to the fourth observation scalar, the third stage being configured to generate the channel-estimation coefficients in response to the first, second, third, and fourth path-estimation coefficients.

8. The MIMO channel estimator of claim 1 further comprising:

a first Kalman filter configured to generate in response to the path independent observation scalar first intermediate coefficients;

a second Kalman filter configured to generate in response to the path dependent observation scalar second intermediate coefficients;

a fourth stage configured to generate first path-estimation coefficients in response to the first intermediate coefficients; and

a fifth stage configured to generate second path-estimation coefficients in response to the second intermediate coefficients, the third stage being configured to generate the channel-estimation coefficients in response to the first and second intermediate coefficients.

10. The MIMO channel estimator of claim 1 wherein the first and second signals each comprises an orthogonal-frequency-division-multiplexed signal.

9. A channel estimator comprising:

a first stage configured to generate a first observation scalar for a first communication path of a first communication channel;

a second stage configured to generate a second observation scalar for a first communication path of a second communication channel;

a third stage configured to generate channel-estimation coefficients in response to the first and second observation scalars;

a first Kalman filter configured to generate in response to the first observation scalar first intermediate coefficients;

a fourth stage configured to generate first path-estimation coefficients in response to the first intermediate coefficients;

a second Kalman filter configured to generate in response to the second observation scalar second intermediate coefficients;

a fifth stage configured to generate second path-estimation coefficients in response to the second intermediate coefficients;

a sixth stage configured to generate a third observation scalar for a second communication path of the first communication channel;

a third Kalman filter configured to generate in response to the third observation scalar third intermediate coefficients;

a seventh stage configured to generate third path-estimation coefficients in response to the third intermediate coefficients;

an eighth stage configured to generate a fourth observation scalar for a second communication path of the second communication channel;

a fourth Kalman filter configured to generate in response to the fourth observation scalar fourth intermediate coefficients; and

a ninth stage configured to generate fourth path-estimation coefficients in response to the fourth intermediate coefficients, the third stage being configured to generate the channel-estimation coefficients in response to the first, second, third, and fourth path-estimation coefficients.

11. A receiver device comprising:

an antenna; and

a Multiple-Input-Multiple-Output (MIMO) channel estimator coupled to said antenna and for MIMO communication with first and second signals respectively over first and second communication channels, the MIMO channel estimator comprising

a first stage configured to generate a path independent observation scalar for each of the first and second signals based upon pilot subcarriers in the first and second signals,

a second stage configured to generate a path dependent observation scalar for the first and second signals, and

a third stage configured to generate channel-estimation coefficients in response to the path independent and path dependent observation scalars for each of the first and second signals and for the MIMO communication over the first and second communication channels.

12. The receiver device of claim 11 wherein the first stage is configured to receive the first signal having a first pilot subcarrier, and to generate the path independent observation scalar in response to first information carried by the first pilot subcarrier;

and wherein the second stage is configured to receive the second signal having a second pilot subcarrier, and to generate the path dependent observation scalar in response to second information carried by the second pilot subcarrier.

13. The receiver device of claim 11 wherein the channel-estimation coefficients include a multi-dimensional array of frequency-domain channel-estimation coefficients for the first and second communication channels.

14. The receiver device of claim 11 wherein said MIMO channel estimate further comprises:

a fourth stage configured to generate a third observation scalar; and

a fifth stage configured to generate a fourth observation scalar, the second stage being configured to generate the channel-estimation coefficients in response to the third and fourth observation scalars.

15. The receiver device of claim 11 wherein said MIMO channel estimate further comprises:

a fourth stage configured to generate first path-estimation coefficients; and

a fifth stage configured to generate second path-estimation coefficients the third stage being configured to generate the channel-estimation coefficients in response to the first and second path-estimation coefficients.

16. The receiver device of claim 15 wherein the first and second path-estimation coefficients each comprises time-domain coefficients;

and

wherein the channel-estimation coefficients comprise frequency-domain coefficients.

17. The receiver device of claim 11 wherein said MIMO channel estimate further comprises:

a fourth stage configured to generate a third observation scalar;

a fifth stage configured to generate a fourth observation scalar;

a sixth stage configured to generate first path-estimation coefficients in response to the first observation scalar;

a seventh stage configured to generate second path-estimation coefficients in response to the second observation scalar;

an eighth stage configured to generate third path-estimation coefficients in response to the third observation scalar; and

a ninth stage configured to generate fourth path-estimation coefficients in response to the fourth observation scalar, the third stage being configured to generate the channel-estimation coefficients in response to the first, second, third, and fourth path-estimation coefficients.

18. The receiver device of claim 11 wherein said MIMO channel estimate further comprises:

a first Kalman filter configured to generate in response to the path independent observation scalar first intermediate coefficients;

a second Kalman filter configured to generate in response to the path dependent observation scalar second intermediate coefficients;

a fourth stage configured to generate first path-estimation coefficients in response to the first intermediate coefficients; and

a fifth stage configured to generate second path-estimation coefficients in response to the second intermediate coefficients, the third stage being configured to generate the channel-estimation coefficients in response to the first and second intermediate coefficients.

19. The receiver device of claim 11 wherein the first and second signals each comprises an orthogonal-frequency-division-multiplexed signal.

20. A method for operating a Multiple-Input-Multiple-Output (MIMO) channel estimator for MIMO communication with first and second signals respectively over first and second communication channels, the method comprising:

operating a first stage to generate a path independent observation scalar for each of the first and second signals based upon pilot subcarriers in the first and second signals;

operating a second stage to generate a path dependent observation scalar for the first and second signals; and

operating a third stage to generate channel-estimation coefficients in response to the path independent and path dependent observation scalars for each of the first and second signals and for the MIMO communication over the first and second communication channels.

21. The method of claim 20 wherein the first stage is configured to receive the first signal having a first pilot subcarrier, and to generate the path independent observation scalar in response to first information carried by the first pilot subcarrier;

and wherein the second stage is configured to receive the second signal having a second pilot subcarrier, and to generate the path dependent observation scalar in response to second information carried by the second pilot subcarrier.

22. The method of claim 20 wherein the channel-estimation coefficients include a multi-dimensional array of frequency-domain channel-estimation coefficients for the first and second communication channels.

23. The method of claim 20 further comprising:

operating a fourth stage to generate a third observation scalar; and

operating a fifth stage to generate a fourth observation scalar, the second stage being configured to generate the channel-estimation coefficients in response to the third and fourth observation scalars.

24. The method of claim 20 further comprising:

operating a fourth stage to generate first path-estimation coefficients; and

operating a fifth stage to generate second path-estimation coefficients the third stage being configured to generate the channel-estimation coefficients in response to the first and second path-estimation coefficients.

25. The method of claim 24 wherein the first and second path-estimation coefficients each comprises time-domain coefficients;

and wherein the channel-estimation coefficients comprise frequency-domain coefficients.

26. The method of claim 20 further including:

operating a fourth stage to generate a third observation scalar;

operating a fifth stage to generate a fourth observation scalar;

operating a sixth stage to generate first path-estimation coefficients in response to the first observation scalar;

operating a seventh stage to generate second path-estimation coefficients in response to the second observation scalar;

operating an eighth stage to generate third path-estimation coefficients in response to the third observation scalar; and

operating a ninth stage to generate fourth path-estimation coefficients in response to the fourth observation scalar, the third stage being configured to generate the channel-estimation coefficients in response to the first, second, third, and fourth path-estimation coefficients.

27. The method of claim 20 further comprising:

operating a first Kalman filter to generate in response to the path independent observation scalar first intermediate coefficients;

operating a second Kalman filter to generate in response to the path dependent observation scalar second intermediate coefficients;

operating a fourth stage to generate first path-estimation coefficients in response to the first intermediate coefficients; and

operating a fifth stage to generate second path-estimation coefficients in response to the second intermediate coefficients, the third stage being configured to generate the channel-estimation coefficients in response to the first and second intermediate coefficients.

28. The method of claim 20 where the first and second signals each comprises an orthogonal-frequency-division-multiplexed signal.

29. A non-transitory computer-readable medium storing instructions that, when executed by a computing apparatus, cause the computing apparatus to perform a method for operating a Multiple-Input-Multiple-Output (MIMO) channel estimator for MIMO communication with first and second signals respectively over first and second communication channels, the method comprising:

operating a first stage to generate a path independent observation scalar for each of the first and second signals based upon pilot subcarriers in the first and second signals;

operating a second stage to generate a path dependent observation scalar for the first and second signals; and

operating a third stage to generate channel-estimation coefficients in response to the path independent and path dependent observation scalars for each of the first and second signals and for the MIMO communication over the first and second communication channels.

30. The non-transitory computer-readable medium of claim 29 wherein the first stage is configured to receive the first signal having a first pilot subcarrier, and to generate the path independent observation scalar in response to first information carried by the first pilot subcarrier;

and wherein the second stage is configured to receive the second signal having a second pilot subcarrier, and to generate the path dependent observation scalar in response to second information carried by the second pilot subcarrier.

31. The non-transitory computer-readable medium of claim 29 wherein the channel-estimation coefficients include a multi-dimensional array of frequency-domain channel-estimation coefficients for the first and second communication channels.

32. The non-transitory computer-readable medium of claim 29 wherein the method further comprises:

operating a fourth stage to generate a third observation scalar; and

operating a fifth stage to generate a fourth observation scalar, the second stage being configured to generate the channel-estimation coefficients in response to the third and fourth observation scalars.