MIMO WLAN SYSTEM

• US 20080285488A1
• Filed: 04/30/2008
• Published: 11/20/2008
• Est. Priority Date: 10/25/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Howard, Steven J., Ketchum, John W., Walton, J. Rodney, Wallace, Mark S.
• Granted Patent: US 8,913,529 B2
• Time in Patent Office: Days
• US Class Current: 370/280
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• CPC Class Codes: H04B 7/0421 utilizing implicit feedback, e.g. steered pilot signals
• CPC Class Codes: H04B 7/043 using best eigenmode, e.g. beam forming or beam steering
• CPC Class Codes: H04B 7/0443 utilizing "waterfilling" technique
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0689 using different transmission schemes, at least one of them being a diversity transmission scheme
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04B 7/0871 using different reception schemes, at least one of them being a diversity reception scheme
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0017 where the mode-switching is based on Quality of Service requirement
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/0069 Puncturing patterns
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0606 Space-frequency coding
• CPC Class Codes: H04L 1/0625 Transmitter arrangements
• CPC Class Codes: H04L 1/0656 Cyclotomic systems, e.g. Bell Labs Layered Space-Time [BLAST]
• CPC Class Codes: H04L 1/08 : by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 1/16 : in which the return channel carries supervisory signals, e.g. repetition request signals
• CPC Class Codes: H04L 1/1887 : Scheduling and prioritising arrangements
• CPC Class Codes: H04L 2025/03414 : Multicarrier
• CPC Class Codes: H04L 2025/03426 : transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 25/0204 : of multiple channels
• CPC Class Codes: H04L 25/0226 : sounding signals per se
• CPC Class Codes: H04L 25/0228 : with direct estimation from sounding signals
• CPC Class Codes: H04L 25/0248 : Eigen-space methods
• CPC Class Codes: H04L 25/03343 : Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2602 : Signal structure
• CPC Class Codes: H04L 27/2607 : Cyclic extensions
• CPC Class Codes: H04L 27/2647 : Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0023 : Time-frequency-space
• CPC Class Codes: H04L 5/0048 : Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 28/20 : Negotiating bandwidth
• CPC Class Codes: H04W 28/22 : Negotiating communication rate
• CPC Class Codes: H04W 52/42 : in systems with time, space, frequency or polarisation diversity
• CPC Class Codes: H04W 52/50 : at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 72/12 : Wireless traffic scheduling
• CPC Class Codes: H04W 84/12 : WLAN [Wireless Local Area Networks]

Abstract

A multiple-access MIMO WLAN system that employs MIMO, OFDM, and TDD. The system (1) uses a channel structure with a number of configurable transport channels, (2) supports multiple rates and transmission modes, which are configurable based on channel conditions and user terminal capabilities, (3) employs a pilot structure with several types of pilot (e.g., beacon, MIMO, steered reference, and carrier pilots) for different functions, (4) implements rate, timing, and power control loops for proper system operation, and (5) employs random access for system access by the user terminals, fast acknowledgment, and quick resource assignments. Calibration may be performed to account for differences in the frequency responses of transmit/receive chains at the access point and user terminals. The spatial processing may then be simplified by taking advantage of the reciprocal nature of the downlink and uplink and the calibration.

Claims

1. A method of exchanging data in a wireless time division duplex (TDD) multiple-input multiple-output (MIMO) communication system, comprising:

receiving a pilot on an uplink from a user terminal;

deriving at least one steering vector for a downlink for the user terminal based on the received pilot; and

performing spatial processing, with the at least one steering vector, on a first data transmission sent on the downlink to the user terminal.

2. The method of claim 1, wherein a single steering vector is derived for the downlink for the user terminal, and wherein spatial processing for beam-steering is performed on the first data transmission with the single steering vector to send the first data transmission via a single spatial channel of the downlink.

3. The method of claim 1, wherein a plurality of steering vectors are derived for the downlink for the user terminal, and wherein spatial processing for spatial multiplexing is performed on first the data transmission with the plurality of steering vectors to send the first data transmission via a plurality of spatial channels of the downlink.

4. The method of claim 1, further comprising:

deriving a matched filter for the uplink for the user terminal based on the received pilot; and

performing matched filtering of a second data transmission received on the uplink from the user terminal with the matched filter.

5. The method of claim 4, wherein the matched filter comprises at least one eigenvector for at least one eigenmode of the uplink, and wherein the at least one eigenvector for the uplink is equal to the at least one steering vector for the downlink.

6. An apparatus in a wireless time division duplex (TDD) multiple-input multiple-output (MIMO) communication system, comprising:

a receive spatial processor operative to receive a pilot on an uplink from a user terminal;

a controller operative to derive at least one steering vector for a downlink for the user terminal based on the received pilot; and

a transmit spatial processor operative to perform spatial processing with the at least one steering vector on a first data transmission sent on the downlink to the user terminal.

7. The apparatus of claim 6, wherein the controller is operative to derive a single steering vector for the downlink for the user terminal, and wherein the transmit spatial processor is operative to perform spatial processing for beam-steering on the first data transmission with the single steering vector to send the first data transmission via a single spatial channel of the downlink.

8. The apparatus of claim 6, wherein the controller is operative to derive a plurality of steering vectors for the downlink for the user terminal, and wherein the transmit spatial processor is operative to perform spatial processing for spatial multiplexing on first the data transmission with the plurality of steering vectors to send the first data transmission via a plurality of spatial channels of the downlink.

9. The apparatus of claim 6, wherein the controller is further operative to derive a matched filter for the uplink for the user terminal based on the received pilot, and wherein the receive spatial processor is further operative to perform matched filtering of a second data transmission received on the uplink from the user terminal with the matched filter.

10. The apparatus of claim 9, wherein the matched filter comprises at least one eigenvector for at least one eigenmode of the uplink, and wherein the at least one eigenvector for the uplink is equal to the at least one steering vector for the downlink.

11. An apparatus in a wireless time division duplex (TDD) multiple-input multiple-output (MIMO) communication system, comprising:

means for receiving a pilot on an uplink from a user terminal;

means for deriving at least one steering vector for a downlink for the user terminal based on the received pilot; and

means for performing spatial processing, with the at least one steering vector, on a first data transmission sent on the downlink to the user terminal.

12. The apparatus of claim 11, wherein a single steering vector is derived for the downlink for the user terminal, and wherein spatial processing for beam-steering is performed on the first data transmission with the single steering vector to send the first data transmission via a single spatial channel of the downlink.

13. The apparatus of claim 11, wherein a plurality of steering vectors are derived for the downlink for the user terminal, and wherein spatial processing for spatial multiplexing is performed on first the data transmission with the plurality of steering vectors to send the first data transmission via a plurality of spatial channels of the downlink.

14. The apparatus of claim 11, further comprising:

means for deriving a matched filter for the uplink for the user terminal based on the received pilot; and

means for performing matched filtering of a second data transmission received on the uplink from the user terminal with the matched filter.

15. The apparatus of claim 14, wherein the matched filter comprises at least one eigenvector for at least one eigenmode of the uplink, and wherein the at least one eigenvector for the uplink is equal to the at least one steering vector for the downlink.

16. A method of transmitting and receiving pilots in a wireless multiple-input multiple-output (MIMO) communication system, comprising:

transmitting a MIMO pilot from a plurality of antennas and on a first communication link, wherein the MIMO pilot comprises a plurality of pilot transmissions sent from the plurality of antennas, and wherein the pilot transmission from each antenna is identifiable by a communicating entity receiving the MIMO pilot; and

receiving a steered pilot via at least one eigenmode of a second communication link from the communicating entity, wherein the steered pilot is generated based on the MIMO pilot.

17. The method of claim 16, wherein the first communication link is an uplink, the second communication link is a downlink, and the communicating entity is a user terminal.

18. The method of claim 16, wherein the first communication link is a downlink, the second communication link is an uplink, and the communicating entity is an access point.

19. The method of claim 16, wherein the pilot transmission from each antenna is associated with a different orthogonal code.

20. The method of claim 16, wherein the steered pilot is received via a single eigenmode of the second communication link and is transmitted at full transmit power from a plurality of antennas at the communicating entity.

21. The method of claim 16, wherein the steered pilot is received via a plurality of eigenmodes of the second communication link.

22. The method of claim 16, wherein the steered pilot is transmitted by the communicating entity for a time duration configurable by the system.

23. An apparatus in a wireless multiple-input multiple-output (MIMO) communication system, comprising:

a transmit spatial processor operative to generate a MIMO pilot for transmission from a plurality of antennas and on a first communication link, wherein the MIMO pilot comprises a plurality of pilot transmissions sent from the plurality of antennas, and wherein the pilot transmission from each antenna is identifiable by a communicating entity receiving the MIMO pilot; and

a receive spatial processor operative to process a steered pilot received via at least one eigenmode of a second communication link from the communicating entity, wherein the steered pilot is generated based on the MIMO pilot.

24. The apparatus of claim 23, wherein the pilot transmission from each antenna is associated with a different orthogonal code.

25. The apparatus of claim 23, wherein the steered pilot is received via a single eigenmode of the second communication link and is transmitted at full transmit power from a plurality of antennas at the communicating entity.

26. The apparatus of claim 23, wherein the steered pilot is received via a plurality of eigenmodes of the second communication link.

27. An apparatus in a wireless multiple-input multiple-output (MIMO) communication system, comprising:

means for transmitting a MIMO pilot from a plurality of antennas and on a first communication link, wherein the MIMO pilot comprises a plurality of pilot transmissions sent from the plurality of antennas, and wherein the pilot transmission from each antenna is identifiable by a communicating entity receiving the MIMO pilot; and

means for receiving a steered pilot via at least one eigenmode of a second communication link from the communicating entity, wherein the steered pilot is generated based on the MIMO pilot.

28. The apparatus of claim 27, wherein the pilot transmission from each antenna is associated with a different orthogonal code.

29. The apparatus of claim 27, wherein the steered pilot is received via a single eigenmode of the second communication link and is transmitted at full transmit power from a plurality of antennas at the communicating entity.

30. The apparatus of claim 27, wherein the steered pilot is received via a plurality of eigenmodes of the second communication link.