Transmission mode selection for data transmission in a multi-channel communication system

• US 20040184398A1
• Filed: 03/20/2003
• Published: 09/23/2004
• Est. Priority Date: 03/20/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Medvedev, Irina, Walton, Jay Rod
• Granted Patent: US 7,885,228 B2
• Time in Patent Office: Days
• US Class Current: 370/203
• 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 1/0016 involving special memory structures, e.g. look-up tables
• CPC Class Codes: H04L 1/0021 in which the algorithm uses adaptive thresholds
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0618 Space-time coding

Abstract

Techniques to select a suitable transmission mode for a data transmission in a multi-channel communication system with multiple transmission channels having varying SNRs. In one method, an SNR estimate is initially obtained for each of multiple transmission channels used to transmit a, data stream. An average SNR and an unbiased variance are then computed for the SNR estimates for the multiple transmission channels. A back-off factor is determined, for example, based on the SNR variance and a sealing factor. An operating SNR for the transmission channels is next computed based on the average SNR and the back-off factor. The transmission mode is then selected for the data stream based on the operating SNR. The selected transmission mode is associated with a highest required SNR that is less than or equal to the operating SNR. The method may be used for any system with multiple transmission channels having varying SNRs.

Claims

1. A method of determining a transmission mode for a data transmission in a multi-channel communication system, comprising:

obtaining a signal-to-noise ratio (SNR) estimate for each of a plurality of transmission channels used for the data transmission;

computing an average SNR based on SNR estimates for the plurality of transmission channels;

determining a back-off factor; and

determining the transmission mode for the data transmission based on the average SNR and the back-off factor.

2. The method of claim 1, wherein the SNR estimates and average SNR are in units of decibels.

3. The method of claim 1, wherein the transmission mode for the data transmission indicates a particular data rate, a particular coding scheme, and a particular modulation scheme to use for the data transmission.

4. The method of claim 1, further comprising:

computing an operating SNR based on the average SNR and the back-off factor, and wherein the transmission mode for the data transmission is associated with a required SNR that is less than or equal to the operating SNR.

5. The method of claim 4, wherein the required SNR for the transmission mode is determined based on an additive white Gaussian noise (AWGN) channel.

6. The method of claim 4, wherein a set of transmission modes is supported by the multi-channel communication system, and wherein the transmission mode for the data transmission is associated with a highest required SNR that is less than or equal to the operating SNR.

7. The method of claim 1, further comprising:

computing variance of the SNR estimates for the plurality of transmission channels, and wherein the back-off factor is determined based on the variance.

8. The method of claim 7, wherein the back-off factor is equal to a value obtained by multiplying the variance of the SNR estimates with a scaling factor.

9. The method of claim 8, wherein the scaling factor is selected based on one or more characteristics of the multi-channel communication system.

10. The method of claim 9, wherein the one or more characteristics relate to interleaving, packet size, type of coding scheme, or a combination thereof, used for the data transmission.

11. The method of claim 7, wherein the back-off factor is further determined based on the average SNR.

12. The method of claim 1, wherein the back-off factor is determined based on the average SNR.

13. The method of claim 1, wherein the back-off factor is a fixed value.

14. The method of claim 1, wherein the multi-channel communication system is an orthogonal frequency division multiplex (OFDM) communication system, and wherein the plurality of transmission channels correspond to a plurality of subbands.

15. The method of claim 1, wherein the multi-channel communication system is a multiple-input multiple-output (MIMO) communication system, and wherein the plurality of transmission channels correspond to a plurality of spatial channels.

16. The method of claim 1, wherein the multi-channel communication system is a multiple-input multiple-output (MIMO) communication system that utilizes orthogonal frequency division multiplex (OFDM).

17. The method of claim 16, wherein the plurality of transmission channels correspond to a plurality of subbands of at least one spatial channel.

18. The method of claim 16, wherein the plurality of transmission channels correspond to a plurality of subbands of at least one transmit antenna.

19. The method of claim 16, wherein the plurality of transmission channels correspond on a plurality of subbands of a plurality of transmit antennas.

20. An apparatus in a multi-channel communication system, comprising:

means for obtaining a signal-to-noise ratio (SNR) estimate for each of a plurality of transmission channels used for a data transmission;

means for computing an average SNR based on SNR estimates for the plurality of transmission channels;

means for determining a back-off factor; and

means for determining a transmission mode for the data transmission based on the average SNR and the back-off factor.

21. The apparatus of claim 20, further comprising:

means for computing an operating SNR based on the average SNR and the back-off factor, and wherein the transmission mode for the data transmission is associated with a required SNR that is less than or equal to the operating SNR.

22. The apparatus of claim 20, further comprising:

means for computing variance of the SNR estimates for the plurality of transmission channels, and wherein the back-off factor is determined based on the variance.

23. The apparatus of claim 22, wherein the back-off factor is further determined based on a scaling factor.

24. The apparatus of claim 20, further comprising:

means for storing a set of transmission modes supported by the multi-channel communication system and a required SNR for each of the transmission modes in the set.

25. A receiver unit in a multi-channel communication system, comprising:

a channel estimator operative to provide channel estimates for a plurality of transmission channels used for a data transmission; and

a controller operative to obtain a signal-to-noise ratio (SNR) estimate for each of the plurality of transmission channels based on the channel estimates, compute an average SNR based on SNR estimates for the plurality of transmission channels, determine a back-off factor, and determine a transmission mode for the data transmission based on the average SNR and the back-off factor.

26. The receiver unit of claim 25, wherein the controller is further operative to compute variance of the SNR estimates for the plurality of transmission channels, and wherein the back-off factor is determined based on the variance.

27. The receiver unit of claim 26, wherein the back-off factor is further determined based on a scaling factor.

28. The receiver unit of claim 25, further comprising:

a memory unit operative to store a set of transmission modes supported by the multi-channel communication system and a required SNR for each of the transmission modes in the set.

29. An article of manufacture comprising

code for obtaining a signal-to-noise ratio (SNR) estimate for each of a plurality of transmission channels used for a data transmission;

code for computing an average SNR based on SNR estimates for the plurality of transmission channels;

code for determining a back-off factor;

code for determining a transmission mode for the data transmission based on the average SNR and the back-off factor; and

a computer-usable medium configured to store the codes.

30. The article of claim 29, further comprising:

code for computing variance of the SNR estimates for the plurality of transmission channels, and wherein the back-off factor is determined based on the variance.

31. The article of claim 30, wherein the back-off factor is further determined based on a scaling factor.

32. A method of determining transmission modes for data transmission in a multi-channel communication system, comprising:

obtaining a signal-to-noise ratio (SNR) estimate for each of a first plurality of transmission channels used for a first data stream;

computing a first average SNR and a first SNR variance based on SNR estimates for the first plurality of transmission channels;

determining a first back-off factor based on the first SNR variance;

determining a first transmission mode for the first data stream based on the first average SNR and the first back-off factor;

obtaining an SNR estimate for each of a second plurality of transmission channels used for a second data stream;

computing a second average SNR and a second SNR variance based on SNR estimates for the second plurality of transmission channels;

determining a second back-off factor based on the second SNR variance;

determining a second transmission mode for the second data stream based on the second average SNR and the second back-off factor.

33. The method of claim 32, wherein the first plurality of transmission channels is for a first antenna and the second plurality of transmission channels is for a second antenna.

34. The method of claim 32, wherein the multi-channel communication system is a multiple-input multiple-output (MIMO) communication system, and wherein the first plurality of transmission channels is for a first spatial channel and the second plurality of transmission channels is for a second spatial channel.

35. A method of processing data for transmission in a multi-channel communication system, comprising:

obtaining a transmission mode indicative of a particular data rate, a particular coding scheme, and a particular modulation scheme to use for a data transmission on a plurality of transmission channels, wherein the transmission mode is selected based on an average signal-to-noise ratio (SNR) and a back-off factor, and wherein the average SNR is computed based on SNR estimates for the plurality of transmission channels;

receiving traffic data at the particular data rate;

coding the traffic data with the particular coding scheme to provide coded data; and

modulating the coded data with the particular modulation scheme to provide modulation symbols.

36. An apparatus in a multi-channel communication system, comprising:

means for obtaining a transmission mode indicative of a particular data rate, a particular coding scheme, and a particular modulation scheme to use for a data transmission on a plurality of transmission channels, wherein the transmission mode is selected based on an average signal-to-noise ratio (SNR) and a back-off factor, and wherein the average SNR is computed based on SNR estimates for the plurality of transmission channels;

means for receiving traffic data at the particular data rate;

means for coding the traffic data with the particular coding scheme to provide coded data; and

means for modulating the coded data with the particular modulation scheme to provide modulation symbols.

37. A transmitter unit in a multi-channel communication system, comprising:

a transmit data processor operative to receive traffic data at a particular data rate, code the traffic data with a particular coding scheme to provide coded data, and modulate the coded data with a particular modulation scheme to provide modulation symbols, wherein the particular data rate, coding scheme, and modulation scheme are indicated by a transmission mode selected for a data transmission on a plurality of transmission channels, wherein the transmission mode is selected based on an average signal-to-noise ratio (SNR) and a back-off factor, and wherein the average SNR is computed based on SNR estimates for the plurality of transmission channels.