Rate-adaptive Multiple Input/Multiple Output (MIMO) systems

• US 20060166626A1
• Filed: 03/22/2006
• Published: 07/27/2006
• Est. Priority Date: 01/31/2003
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Winters, Jack Harriman, Luo, Hui, Sollenberger, Nelson Ray
• Granted Patent: US 7,463,867 B2
• Time in Patent Office: Days
• US Class Current: 455/69
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0667 of delayed versions of same signal using space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0891 Space-time diversity rake receivers H04B1/7115; space-time decoding H04L1/0631
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• 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 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 1/1671 the supervisory signal being transmitted together with control information
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

A rate-adaptive method of communicating over a multipath wireless communication system uses multiple links such that each end of a link uses multiple transmit and receive antennas. A number of independent streams that are to be transmitted for each link is determined based on an overall system performance measure. In addition, the system may also jointly determine the best modulation, coding, power control, and frequency assignment for each link, based on an overall system performance measure. In OFDM systems, the number of independent streams, as well as the modulation, coding, and power control, may be determined on a tone-by-tone basis based on an overall system performance measure.

Claims

1. An arrangement with a plurality of antennas B responsive to signals transmitted from a transmitter with a plurality of antennas A, which signals pass through a transmission channel, where the receiver includes decoding circuitry that decodes information received by antennas B in each frame of a flow of frames, the improvement comprising:

processing-and-communication circuitry that processes the signals received in each frame of the flow of frames to determine nature of information that is to be sent by the transmitter in the immediately following frame, and transmits a rate-adaptation instruction to the transmitter that specifies the nature of information that is to be sent by the transmitter in the immediately following frame.

2. The arrangement of claim 1 where the processing-and-communication circuitry transmits the rate-adaptation instruction to the transmitter via a plurality of transmit antennas.

3. The arrangement of claim 1 where the decoding circuitry and the processing-and-communication circuitry are adapted to process frame signals that include information in a training sequence field, a payload field, a payload validation field, and a control field.

4. The arrangement of claim 3 where the information in the payload validation fields is a cyclic redundancy check (CRC) code.

5. The arrangement of claim 3 where the decoding circuitry utilizes the training sequence field information of a frame to estimate characteristics of the transmission channel for a frame.

6. The arrangement of claim 3 where the decoding circuitry and the processing-and-communication circuitry are adapted to utilize the control field information.

7. The arrangement of claim 6 where the control field information is used to identify attributes of the payload field information.

8. The arrangement of claim 3 where detection of signals in the control field assumes that information in the control field of frames that are concurrently transmitted by the transmitter is the same.

9. The arrangement of claim 3 where the processing-and-communication circuitry computes a selected measure of goodness for each frame of the flow of frames, and constructs the rate-adaptation instruction based on the validation field information and the selected measure of goodness.

10. The arrangement of claim 9 where the selected measure of goodness is a signal-to-interference-and-noise-ratio (SINR).

11. The arrangement of claim 9 where the selected measure of goodness is a mean-squared error between a received training sequence as decoded from the received training sequence field information and a known training sequence.

12. The arrangement of claim 9 where the rate adaptation instruction relates to (a) number of data streams that are to be sent by the transmitter'"'"'s antennas A, (b) modulation method used by the transmitter, (c) coding scheme used by the transmitter, or/and (d) coding rate used by the transmitter.

13. The arrangement of claim 9 where the rate adaptation instruction relates to whether to

(a) resend some or all of the information sent in the current frame,

(b) send new information, while maintaining existing number of data streams, modulation method, coding scheme, and coding rate, or

(c) send new information with a modified (i) number of data streams that are to be sent by the transmitter'"'"'s antennas A, (ii) modulation method, (iii) coding scheme, or/and (iv) coding rate.

14. The arrangement of claim 1 further comprising said transmitter that includes a plurality of transmitting antennas A and a plurality of receiving antennas.

15. The arrangement of claim 1 where the receiver is connected to a computer, and the transmitter is a wireless access point.

16. The arrangement of claim 15 where both the receiver and the transmitter have 4 antennas that are used for receiving and transmitting.

17. A method executed in a receiver having B receiving antennas that is responsive to a transmitter having M transmitting antennas, with a transmission channel existing between the transmitter and the receiver, where the receiver is adapted to concurrently receive, in a frame interval, a signal from each of the B receiving antennas, which signal results either from one signal sent by the transmitter or from a plurality of signals concurrently sent by the transmitter during the frame interval, where the signal or signals sent by the transmitter have a predetermined modulation method, coding scheme and coding rate, and where the signal in a frame interval includes information in a training sequence field, a payload field, and a validation field, comprising the steps of:

receiving a first set of B signals in a frame interval;

processing the information received in the training sequence fields of the B signals to develop a transmission channel approximation, which is a matrix, and B weights that are applied to payload field information of respective ones of the B signals in the course of combining the payload field information to form a composite signal;

decoding said composite signal;

estimating how many data streams should be transmitted to said receiver in an immediately following frame interval;

constructing a rate-adaptation message based on the step of estimating; and

transmitting the rate-adaptation message to the transmitter.

18. The method of claim 17 where the developed weights are adapted to minimize a mean-square error when decoding said composite signal.

19. The method of claim 17 where said estimating is based on average signal-to-interference-and-noise ratio (SINR), the number of correctly decoded signals obtained from the step of decoding, and the transmission channel approximation.

20. The method of claim 17 where the transmitting of the rate-adaptation message is via a plurality of antennas.

21. The method of claim 17 where the step of estimating assesses the rank of the transmission channel approximation matrix.