Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel inversion

• US 20030048856A1
• Filed: 05/17/2001
• Published: 03/13/2003
• Est. Priority Date: 05/17/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ling, Fulyun, Howard, Steven J., Ketchum, John W., Wallace, Mark S., Walton, Jay Rod
• Granted Patent: US 7,688,899 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0068 by puncturing
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 2001/0096 Channel splitting in point-to-point links
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/346 distributing total power among users or channels
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

Techniques to process data for transmission over a set of transmission channels selected from among all available transmission channels. In an aspect, the data processing includes coding data based on a common coding and modulation scheme to provide modulation symbols and pre-weighting the modulation symbols for each selected channel based on the channel'"'"'s characteristics. The pre-weighting may be achieved by “inverting” the selected channels so that the received SNRs are approximately similar for all selected channels. With selective channel inversion, only channels having SNRs at or above a particular threshold are selected, “bad” channels are not used, and the total available transmit power is distributed across only “good” channels. Improved performance is achieved due to the combined benefits of using only the N_s best channels and matching the received SNR of each selected channel to the SNR required by the selected coding and modulation scheme.

Claims

1. A method for processing data for transmission over multiple transmission channels in a multi-channel communication system, comprising:

determining characteristics of a plurality of transmission channels available for data transmission;

selecting one or more available transmission channels based on the determined characteristics and a threshold;

coding data for all selected transmission channels based on a particular coding scheme to provide coded data;

modulating the coded data for all selected transmission channels based on a particular modulation scheme to provide modulation symbols; and

weighting modulation symbols for each selected transmission channel based on a respective weight indicative of a transmit power level for the selected transmission channel and derived based in part on the determined characteristics of the selected transmission channel.

2. The method of claim 1, wherein the weights for the selected transmissions are derived to distribute total available transmit power among all selected transmission channels to achieve similar received quality for modulation symbols received via the selected transmission channels.

3. The method of claim 2, wherein the received quality is estimated by signal-to-noise-plus-interference ratios (SNRs).

4. The method of claim 1, wherein the determined characteristics for the available transmission channels are channel gains.

5. The method of claim 4, wherein transmission channels having power gains greater than or equal to a particular power gain threshold are selected, and wherein the power gains are determined based on the channel gains.

6. The method of claim 1, wherein the determined characteristics for the available transmission channels are received signal-to-noise-plus-interference ratios (SNRs).

7. The method of claim 6, wherein transmission channels having SNRs greater than or equal to a particular SNR threshold are selected.

8. The method of claim 1, wherein the determined characteristics for the available transmission channels are expressed via power control information.

9. The method of claim 8, wherein the power control information is indicative of requests for changes in power level.

10. The method of claim 1, wherein the weight for each selected transmission channel is further determined based on total transmit power available for data transmission.

11. The method of claim 1, wherein the weight for each selected transmission channel is further derived based on a normalization factor, which is determined based on the characteristics of the selected transmission channels.

12. The method of claim 1, wherein the threshold is selected to provide high throughput for the selected transmission channels.

13. The method of claim 1, wherein the threshold is selected to provide a highest throughput for the available transmission channels.

14. The method of claim 1, wherein the threshold is derived based on a particular target SNR for all selected transmission channels.

15. The method of claim 1, further comprising:

transmitting the weighted modulation symbols on the selected transmission channels.

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

17. 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 available transmission channels correspond to a plurality of spatial subchannels of a MIMO channel.

18. The method of claim 17, wherein the MIMO communication system utilize OFDM, and wherein the plurality of available transmission channels correspond to spatial subchannels of a plurality of frequency subchannels.

19. A method for transmitting data over multiple transmission channels in a multi-channel communication system, comprising:

determining characteristics of each of a plurality of transmission channels available for data transmission;

coding data for selected ones of the available transmission channels to provide coded data;

modulating the coded data to provide modulation symbols;

weighting modulation symbols for each selected transmission channel based on a respective weight indicative of a transmit power level for the selected transmission channel and derived based in part on the determined characteristics of the selected transmission channel; and

transmitting the weighted modulation symbols on the selected transmission channels.

20. The method of claim 19, wherein the data for the selected transmission channels is coded based on a common coding scheme.

21. The method of claim 20, wherein the common coding scheme is selected from among a plurality of possible coding schemes.

22. The method of claim 19, wherein the modulation symbols for the selected transmission channels are derived based on a common modulation scheme.

23. The method of claim 22, wherein the common modulation scheme is selected from among a plurality of possible modulation schemes.

24. The method of claim 19, wherein the data for the selected transmission channels is coded based on a common coding scheme and the modulation symbols for the selected transmission channels are derived based on a common modulation scheme.

25. The method of claim 19, further comprising:

selecting one or more of the available transmission channels for data transmission based on the determined characteristics of the channels and a threshold.

26. In a multi-channel communication system, a method for determining a threshold used to select transmission channels for data transmission, comprising:

defining a set of code rates, wherein each code rate is selectable for coding data prior to transmission;

defining a set of setpoints, wherein each setpoint corresponds to a respective code rate and is indicative of a target signal-to-noise-plus-interference ratio (SNR) required at the corresponding code rate for a particular level of performance;

determining a particular number of transmission channels supported by each code rate and capable of achieving the setpoint corresponding to the code rate;

determining a performance criteria for each code rate based in part on the number of supported transmission channels; and

selecting the threshold based on the determined performance criteria for the code rates in the set, and

wherein transmission channels are selected for use for data transmission based on the threshold.

27. The method of claim 26, wherein the number of transmission channels supported by each code rate is determined by distributing total available transmit power among the supported transmission channels such that the setpoint corresponding to the code rate is achieved for each supported transmission channel.

28. The method of claim 26, wherein the determined performance criteria for each code rate is an overall throughput computed for the supported transmission channels.

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

a controller configured to receive channel state information (CSI) indicative of characteristics of a plurality of transmission channels available for data transmission and to select one or more available transmission channels based on the channel characteristics and a threshold;

a transmit data processor coupled to the controller configured to receive and code data for all selected transmission channels based on a particular coding scheme to provide coded data, modulate the coded data for all selected transmission channels based on a particular modulation scheme to provide modulation symbols, and weight modulation symbols for each selected transmission channel based on a respective weight, wherein each weight is indicative of a transmit power level for the corresponding selected transmission channel and is derived based in part on the characteristics of the selected transmission channel.

30. The transmitter of claim 29, wherein the controller is further configured to select the coding and modulation schemes based on the characteristics of the available transmission channels and to provide one or more control signals indicative of the selected coding and modulation schemes.

31. The transmitter of claim 29, wherein the controller is further configured to determine the threshold based on the characteristics of the available transmission channels.

32. The transmitter of claim 29, further comprising:

a transmit channel processor coupled to the transmit data processor and configured to receive and demultiplex the weighted modulation symbols for the selected transmission channels into a plurality of streams, one stream for each antenna used to transmitted the data.

33. The transmitter of claim 29, wherein the CSI comprise signal-to-noise-plus-interference ratio (SNR) estimates for the available transmission channels.

34. The transmitter of claim 29, wherein the CSI comprise channel gain estimates for the available transmission channels.

35. The transmitter of claim 29, wherein the CSI comprise power control information for the available transmission channels.

36. The transmitter of claim 29, wherein the transmitter unit is operative to transmit data on a downlink in the communication system.

37. The transmitter of claim 29, wherein the transmitter unit is operative to transmit data on an uplink in the communication system.