Multi-user MIMO systems and methods
View Patent ↗A method is provided for scheduling data transmission in a Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) system. The MIMO-OFDM system may comprise at least one MIMO-OFDM transmitter and at least one MIMO-OFDM receiver. Feedback from one or more receivers may be used by a transmitter to improve quality, capacity, and scheduling in MIMO-OFDM communication systems. The method may comprise generating or receiving information pertaining to a MIMO channel metric and information pertaining to a Channel Quality Indicator (CQI) in respect of a transmitted signal; and sending a next transmission to a receiver using a MIMO mode selected in accordance with the information pertaining to the MIMO channel metric, and an adaptive coding and modulation selected in accordance with the information pertaining to the CQI.
1. A method in a Multiple-Input Multiple-Output (MIMO) transmitter, the method comprising:
a) receiving from a receiver a composite metric based on information pertaining to a MIMO channel metric and information pertaining to a Channel Quality Indicator (CQI) in respect of a transmitted signal, the composite metric specifying the CQI, and a MIMO mode;
b) sending a next transmission to a receiver using a MIMO mode selected in accordance with the composite metric, and an adaptive coding and modulation selected in accordance with the composite metric.
2. The method of claim 1 , wherein the composite metric serves as a basis for selecting between at least two MIMO modes selected from a group consisting of: BLAST, STTD, beamforming, and spatial multiplexing, and other space-time mapping schemes.
3. The method of claim 1 , wherein the MIMO transmitter is a MIMO Orthogonal Frequency Division Multiplexing (MIMO-OFDM) transmitter.
4. The method of claim 1 , further comprising:
receiving from a receiver MIMO capability information indicating MIMO capabilities of the receiver.
5. The method of claim 1 , wherein the composite metric further specifies whether a MIMO channel is orthogonal.
6. The method of claim 1 , further comprising selecting and scheduling one or more transmit antennas at the MIMO transmitter for data transmission to a given receiver based on the composite metric.
7. The method of claim 1 , wherein the MIMO channel metric is determined by one of
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where H is a matrix of the channel state information, H i is a matrix of the channel state information for the i th resource block, ρ i =λmax i /λmin i for each H i , and SNR i is the Signal to Noise Ratio for each H i .
8. The method of claim 1 , wherein, at the transmitter, the composite metric is used to affect the modulation and coding rates only if the MIMO mode is one of spatial multiplexing.
9. A method in a MIMO receiver, the method comprising:
a) generating a MIMO channel metric and CQI of a received signal at the receiver; and
b) feeding back information pertaining to the MIMO channel metric and information pertaining to the CQI in the form of a composite metric that specifies the CQI and a MIMO mode.
10. The method of claim 9 , wherein the MIMO channel metric is determined by one of
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and
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where H is a matrix of the channel state information, H i is a matrix of the channel state information for the i th resource block, ρ i =λmax i /λmin i for each H i , and SNR i is the Signal to Noise Ratio for each H i .
11. The method of claim 9 , wherein the information pertaining to the MIMO channel metric selects serves as the basis for selecting between at least two MIMO modes selected from a group consisting of: BLAST, STTD, beamforming, spatial multiplexing, and other space-time mapping schemes.
12. The method of claim 9 , wherein a MIMO mode is selected on the basis that:
i. when the CQI indicates a low channel quality, the MIMO mode is selected to be a space time block code regardless of the information pertaining to the channel metric;
ii. when the information pertaining to the CQI indicates a high channel quality and the information pertaining to the channel metric is high, the MIMO mode is selected to be spatial multiplexing, and
iii. when the information pertaining to the CQI indicates a high channel quality and the information pertaining to the channel metric is low, the MIMO mode is selected to be one of a space time block code and a spatial multiplex mode.
13. The method of claim 9 ,
wherein the composite metric further indicates an orthogonality of a MIMO channel.
14. The method of claim 9 , further comprising selecting a MIMO mode in accordance with the composite metric, and an adaptive coding and modulation selected in accordance with the composite metric.
15. The method of claim 9 , further comprising using the information pertaining to the MIMO channel metric and the information pertaining to the CQI to determine the composite metric from a lookup table in the receiver.
16. A computer program product comprising a computer-readable medium storing instructions which, when executed by a processor, causes a MIMO transmitter to receive from a receiver a composite metric based on information pertaining to a MIMO channel metric and information pertaining to a CQI in respect of a transmitted signal, the composite metric specifying a CQI and a MIMO mode; and
causes a MIMO transmitter to send a next transmission to a receiver using a MIMO mode selected in accordance with the composite metric, and an adaptive coding and modulation selected in accordance with the composite metric.
17. The computer program product of claim 16 , wherein the composite metric selects between at least two MIMO modes selected from a group consisting of: BLAST, STTD, beamforming, spatial multiplexing, and other space-time mapping schemes.
18. The computer program product of claim 16 , wherein the MIMO transmitter is a MIMO Orthogonal Frequency Division Multiplexing (MIMO-OFDM) transmitter.
19. The computer program product of claim 16 , further comprising instructions which, when executed by a processor cause the processor to select and schedule one or more transmit antennas at the MIMO transmitter for data transmission to a given receiver based on the composite metric.
20. The computer program product of claim 16 , wherein the MIMO channel metric is determined by one of
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and
min
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where H is a matrix of the channel state information, H i is a matrix of the channel state information for the i th resource block, ρ i =λmax i /λmin i for each H i , and SNR i is the Signal to Noise Ratio for each H i .
21. The computer program product of claim 16 , wherein the composite metric has a first bit to specify CQI and a second bit to specify a MIMO mode.
22. A system for processing signals received from a receiver comprising:
an input for receiving the signals; and
a processor configured to:
receive a composite metric based on information pertaining to a MIMO channel metric and information pertaining to a CQI of the signals, the composite metric specifying the CQI and a MIMO mode; and
select a MIMO mode based on the composite metric.
23. The system of claim 22 comprising a MIMO Orthogonal Frequency Division Multiplexing (MIMO-OFDM) transmitter, the MIMO Orthogonal MIMO-OFDM transmitter comprising the processor.
24. The system of claim 22 , wherein the processor uses the composite metric to select between at least two MIMO modes selected from a group consisting of: BLAST, STTD, beamforming, spatial multiplexing, and other space-time mapping schemes.
25. The system of claim 23 , wherein the processor is further configured to select and schedule one or more transmit antennas at the MIMO-OFDM transmitter for data transmission to a given receiver based on the information pertaining to the MIMO channel metric and information pertaining to the CQI.
26. The system of claim 22 , wherein the MIMO channel metric is determined by one of
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and
min
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where H is a matrix of the channel state information, H i is a matrix of the channel state information for the i th resource block, ρ i =λmax i /λmin i for each H i , and SNR i is the Signal to Noise Ratio for each H i .