Rate control for multi-channel communication systems

• US 7,184,713 B2
• Filed: 06/20/2002
• Issued: 02/27/2007
• Est. Priority Date: 06/20/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Kadous, Tamer, Fernandez-Corbaton, Ivan Jesus
• Primary Examiner(s): LEE, JOHN J
• Application Number:
  US10/176,567
• Publication Number:
  US 20030236080A1
• Time in Patent Office: 1,713 Days
• Field of Search: 455423-425, 455450-453, 455 6711- 6716, 455 59- 60, 4551142-1154, 4552261-2264, 455/296, 455/299, 455/522, 455/69, 455101-105, 370250-252, 370/253, 375346-351
• US Class Current: 455/67.13
• 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 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0675 characterised by the signaling
• CPC Class Codes: H04L 1/16 in which the return channel carries supervisory signals, e.g. repetition request signals
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 28/22 Negotiating communication rate
• CPC Class Codes: H04W 52/26 using transmission rate or quality of service QoS [Quality of Service]

Abstract

Techniques to determine a set of rates for a set of data streams to be transmitted in a multi-channel communication system. A group of transmission channels to be used for each data stream is initially identified. An equivalent system for each group is then defined to have an AWGN (or flat) channel and a spectral efficiency equal to the average spectral efficiency of the transmission channels in the group. A metric for each group is then derived based on the associated equivalent system, e.g., set to the SNR needed by the equivalent system to support the average spectral efficiency. A rate for each data stream is then determined based on the metric associated with the data stream. The rate is deemed to be supported by the communication system if the SNR required to support the data rate by the communication system is less than or equal to the metric.

Claims

1. In a multi-channel communication system, a method for determining a rate for a data transmission over a wireless communication channel, comprising:

identifying a plurality of transmission channels to be used for the data transmission;

defining an equivalent system for the transmission channels based on one or more estimated channel characteristics of the transmission channels;

deriving a metric for the transmission channels based on the equivalent system; and

determining a particular rate for the data transmission based on the metric.

2. The method of claim 1, further comprising:

determining an average spectral efficiency of the transmission channels based on the one or more estimated channel characteristics, and

wherein the equivalent system is defined to have an additive white Gaussian noise (AWGN) channel and a spectral efficiency equal to the average spectral efficiency of the transmission channels.

3. The method of claim 2, further comprising:

estimating a spectral efficiency of each transmission channel based on the one or more estimated channel characteristics, and

wherein the average spectral efficiency of the transmission channels is determined based on the estimated spectral efficiencies of the transmission channels.

4. The method of claim 3, wherein the spectral efficiency of each transmission channel is estimated based on a constrained spectral efficiency function.

5. The method of claim 4, wherein the spectral efficiency of each transmission channel is further estimated based on a modulation scheme to be used for the data transmission.

6. The method of claim 3, wherein the spectral efficiency of each transmission channel is estimated based on an unconstrained spectral efficiency function.

7. The method of claim 2, wherein the deriving the metric includes

determining an equivalent signal-to-noise-and-interference ratio (SNR) for the equivalent system, and wherein the metric is related to the equivalent SNR.

8. The method of claim 7, wherein the equivalent SNR is determined based on an inverse function of a spectral efficiency function used to estimate a spectral efficiency of each transmission channel.

9. The method of claim 7, wherein the deriving the metric further includes

adjusting the equivalent SNR to account for losses in the communication system, and wherein the metric is related to the adjusted equivalent SNR.

10. The method of claim 1, further comprising:

determining a particular modulation scheme to use for the data transmission, and wherein the equivalent system is further defined based on the modulation scheme.

11. The method of claim 1;

further comprising;

determining an SNR required to support the particular data rate by the communication system, and wherein the particular data rate is determined to be supported by the transmission channels if the required SNR is less than or equal to the metric.

12. The method of claim 1, wherein the one or more estimated channel characteristics comprise an SNR for each transmission channel.

13. The method of claim 1, wherein the one or more estimated channel characteristics comprise an estimated frequency response and an estimated noise variance for the transmission channels.

14. The method of claim 1, wherein the transmission channels are frequency subchannels or spatial subchannels, or both, in a multipath wireless communication channel with frequency selective fading.

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

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

17. The method of claim 1, wherein the multi-channel communication system is a multiple-input multiple-output (MIMO) communication system that employs orthogonal frequency division multiplex (OFDM), and the transmission channels correspond to frequency subchannels of spatial subchannels.

18. The method of claim 1, wherein a set of rates is available for the data transmission, the method further comprising:

evaluating each of one or more available rates to determine a highest rate supported by the transmission channels.

19. In a multi-channel communication system, a method for determining a rate for a data transmission over a wireless communication channel, comprising:

identifying a group of transmission channels to be used for the data transmission;

obtaining an estimated signal-to-noise-and-interference ratio (SNR) of each transmission channel;

estimating spectral efficiency of each transmission channel based on the estimated SNR for the transmission channel;

determining an average spectral efficiency of the transmission channels based on estimated spectral efficiencies of the transmission channels;

determining an equivalent SNR for an equivalent system with a spectral efficiency equal to the average spectral efficiency of the transmission channels;

determining a required SNR to support a particular data rate by the communication system; and

determining whether the particular rate is supported by the transmission channels for the data transmission based on the equivalent SNR and the required SNR.

20. The method of claim 19, wherein the spectral efficiency of each transmission channel is estimated based on an unconstrained spectral efficiency function.

21. The method of claim 19, wherein the spectral efficiency of each transmission channel is further estimated based on a modulation scheme to be used for the data transmission.

22. The method of claim 19, wherein the multi-channel communication system is a MIMO communication system that employs OFDM.

23. In a multi-channel communication system, a method for determining a set of rates for a set of data streams to be transmitted over a wireless communication channel, comprising:

identifying a group of transmission channels to be used for each data stream;

defining an equivalent system for each transmission channel group based on one or more estimated channel characteristics of the transmission channels in the group;

deriving a metric for each transmission channel group based on the associated equivalent system; and

determining a rate for each data stream based on the metric associated with the data stream.

24. The method of claim 23, further comprising:

estimating a spectral efficiency of each transmission channel based on the one or more estimated channel characteristics, and

determining an average spectral efficiency of the transmission channels in each group based on estimated spectral efficiencies of the transmission channels, and

wherein the equivalent system for each transmission channel group is defined to have an additive white Gaussian noise (AWGN) channel and a spectral efficiency equal to the average spectral efficiency of the transmission channels in the group.

25. The method of claim 24, wherein the spectral efficiency of each transmission channel is estimated based on an unconstrained or constrained spectral efficiency function.

26. The method of claim 23, further comprising:

for each data stream, determining an SNR required to support a particular rate by the communication system, and wherein the particular rate is determined to be supported by the group of transmission channels for the data stream if the required SNR is less than or equal to the metric associated with the data stream.

27. The method of claim 23, wherein the multi-channel communication system is a MIMO communication system that employs OFDM, and the transmission channels correspond to frequency subchannels of spatial subchannels.

28. The method of claim 27, wherein each data stream is transmitted over a respective transmit antenna, and each transmission channel group includes all frequency subchannels for one transmit antenna.

29. A memory communicatively coupled to a digital signal processing device (DSPD) capable of interpreting digital information to:

identify a plurality of transmission channels to be used for the data transmission;

define an equivalent system for the transmission channels based on one or more estimated channel characteristics of the transmission channels;

derive a metric for the transmission channels based on the equivalent system; and

determine a particular rate for the data transmission based on the metric.

30. The memory of claim 29, wherein the DSPD is further capable of interpreting digital information to:

estimate a spectral efficiency of each transmission channel based on the one or more estimated channel characteristics, and

determine an average spectral efficiency of the transmission channels based on estimated spectral efficiencies of the transmission channels, and

wherein the equivalent system is defined to have an additive white Gaussian noise (AWGN) channel and a spectral efficiency equal to the average spectral efficiency of the transmission channels.

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

a channel estimator operative to derive estimates of one or more characteristics of a plurality of transmission channels; and

a rate selector operative to

define an equivalent system based on the one or more estimated channel characteristics of the transmission channels,

derive a metric for the transmission channels based on the equivalent system, and

determine a particular rate for the data transmission based on the metric.

32. The receiver unit of claim 31, wherein the rate selector is further operative to

estimate a spectral efficiency of each transmission channel based on the one or more estimated channel characteristics, and

determine an average spectral efficiency of the transmission channels based on estimated spectral efficiencies of the transmission channels, and

wherein the equivalent system is defined to have an additive white Gaussian noise (AWGN) channel and a spectral efficiency equal to the average spectral efficiency of the transmission channels.

33. The receiver unit of claim 32, wherein the spectral efficiency of each transmission channel is estimated based on a constrained or unconstrained channel spectral efficiency function.

34. The receiver unit of claim 32, further comprising:

a memory configured to store one or more tables for a function used to estimate the spectral efficiency of each transmission channel.

35. The receiver unit of claim 31, further comprising:

a controller operative to provide feedback information comprised of the particular rate.

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

means for identifying a plurality of transmission channels to be used for the data transmission;

means for defining an equivalent system based on one or more estimated channel characteristics of the transmission channels;

means for deriving a metric for the transmission channels based on the equivalent system; and

means for determining a particular rate for the data transmission based on the metric.

37. The receiver apparatus of claim 36, further comprising:

means for estimating a spectral efficiency of each transmission channel based on the one or more estimated channel characteristics, and

means for determining an average spectral efficiency of the transmission channels based on estimated spectral efficiencies of the transmission channels, and

wherein the equivalent system is defined to have an additive white Gaussian noise (AWGN) channel and a spectral efficiency equal to the average spectral efficiency of the transmission channels.

38. The receiver apparatus of claim 37, further comprising:

means for storing one or more tables for a function used to estimate the spectral efficiency of each transmission.

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

a controller operative to identify a rate to use for a data transmission over a plurality of transmission channels in a wireless communication channel, wherein the rate is determined based on an equivalent system defined for the transmission channels based on one or more estimated channel characteristics of the transmission channels;

a transmit data processor operative to code data, provided at the identified rate, in accordance with a particular coding scheme to provide coded data; and

a modulator operative to modulate the coded data in accordance with a particular modulation scheme to provide modulated data.

40. The transmitter unit of claim 39, further comprising:

a transmitter operative to generate at least one modulated signal for the modulated data.

41. The transmitter unit of claim 39, wherein the multi-channel communication system is a MIMO communication system that employs OFDM, and the transmission channels correspond to frequency subchannels of spatial subchannels.

42. An apparatus in a wireless communication system, comprising:

means for identifying a rate to use for a data transmission over a plurality of transmission channels in a wireless communication channel, wherein the rate is determined based on an equivalent system defined for the transmission channels based on one or more estimated channel characteristics of the transmission channels;

means for coding data, provided at the identified rate, in accordance with a particular coding scheme to provide coded data; and

means for modulating the coded data in accordance with a particular modulation scheme to provide modulated data.

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

a controller operative to identify a set of rates for a set of data streams to be transmitted over a wireless communication channel, wherein the rate for each data stream is determined based on an equivalent system defined for a group of transmission channels used for the data stream, and wherein the equivalent system for each transmission channel group is defined based on one or more estimated channel characteristics of the transmission channels in the group;

at least one transmit data processor operative to code each data stream, provided at the identified rate, in accordance with a coding scheme selected for the data stream to provide a corresponding coded data stream; and

at least one modulator operative to modulate each coded data steam in accordance with a modulation scheme selected for the data stream to provide a corresponding modulation stream.

44. A multi-channel communication system comprising:

a receiver unit including

a channel estimator operative to derive estimates of one or more characteristics of a plurality of transmission channels, and

a rate selector operative to define an equivalent system based on the one or more estimated channel characteristics of the transmission channels, derive a metric for the transmission channels based on the equivalent system, and determine a particular rate for the data transmission based on the metric; and

a transmitter unit including

at least one transmit data processor operative to code data, provided at the determined rate, in accordance with a coding scheme to provide coded data, and

at least one modulator operative to modulate the coded data in accordance with a modulation scheme to provide modulated data.