Method and apparatus for allocating uplink resources in a multiple-input multiple-output (MIMO) communication system

• US 20020177447A1
• Filed: 05/16/2001
• Published: 11/28/2002
• Est. Priority Date: 05/16/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Howard, Steven J., Wallace, Mark S., Walton, Jay Rod
• Granted Patent: US 7,047,016 B2
• Time in Patent Office: Days
• US Class Current: 455/452.1
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04B 7/0891 Space-time diversity rake receivers H04B1/7115; space-time decoding H04L1/0631
• CPC Class Codes: H04W 72/12 Wireless traffic scheduling
• CPC Class Codes: H04W 72/121 for groups of terminals or users

Abstract

Techniques to schedule uplink data transmission for a number of terminals in a wireless communication system. In one method, a number of sets of terminals are formed for possible data transmission, with each set including a unique combination of terminals and corresponds to a hypothesis to be evaluated. The performance of each hypothesis is evaluated (e.g., based on channel response estimates for each terminal) and one of the evaluated hypotheses is selected based on the performance. The terminals in the selected hypothesis are scheduled for data transmission. A successive cancellation receiver processing scheme may be used to process the signals transmitted by the scheduled terminals. In this case, one or more orderings of the terminals in each set may be formed, with each terminal ordering corresponding to a sub-hypothesis to be evaluated. The performance of each sub-hypothesis is then evaluated and one of the sub-hypotheses is selected.

Claims

1. A method for scheduling uplink data transmission for a plurality of terminals in a wireless communication system, comprising:

forming one or more sets of terminals for possible transmission on a channel, wherein each set includes a unique combination of terminals and corresponds to a hypothesis to be evaluated;

evaluating performance of each hypothesis;

selecting one of the one or more evaluated hypotheses based on their performance; and

scheduling the terminals in the selected hypothesis for data transmission on the channel.

2. The method of claim 1, further comprising:

determining data rates for each data stream of each terminal in the selected hypothesis, and

wherein data is transmitted at the determined data rates from the terminals in the selected hypothesis.

3. The method of claim 1, further comprising:

determining a coding and modulation scheme to be used for each data stream of each terminal in the selected hypothesis, and

wherein data is processed based on the determined coding and modulation schemes prior to transmission.

4. The method of claim 1, wherein each hypothesis is evaluated based in part on channel response estimates for each terminal in the hypothesis, wherein the channel response estimates are indicative of channel characteristics between the terminal and a receiving system.

5. The method of claim 1, wherein the channel response estimates comprise signal-to-noise-plus-interference ratios (SNRs).

6. The method of claim 1, wherein the evaluating includes computing a performance metric for each hypothesis.

7. The method of claim 6, wherein the performance metric is a function of throughput achievable by each of the terminals in the hypothesis.

8. The method of claim 6, wherein the hypothesis having the best performance metric is selected for scheduling.

9. The method of claim 1, further comprising:

prioritizing the terminals to be considered for scheduling.

10. The method of claim 9, further comprising:

limiting terminals to be processed for scheduling to a group of N highest priority terminals.

11. The method of claim 9, further comprising:

maintaining one or more metrics for each terminal to be considered for scheduling, and

wherein the priority of each terminal is determined based in part on the one or more metrics maintained for the terminal.

12. The method of claim 11, wherein one metric maintained for each terminal relates to an average throughput rate achieved by the terminal.

13. The method of claim 1, wherein the one or more sets are formed from terminals of a plurality of types, wherein each terminal of a first type is capable of transmitting a single data stream on a single transmission channel and each terminal of a second type is capable of transmitting multiple independent data streams on multiple transmission channels.

14. The method of claim 13, wherein each transmission channel corresponds to a spatial subchannel in the communication system.

15. The method of claim 1, wherein each of the one or more sets includes terminals having similar link margins.

16. The method of claim 1, further comprising:

forming one or more orderings of the terminals in each set, wherein each terminal ordering corresponds to a sub-hypothesis to be evaluated, and

wherein the performance of each sub-hypothesis is evaluated and one of the plurality of sub-hypotheses is selected based on their performance.

17. The method of claim 16, wherein the evaluating for each sub-hypothesis includes

processing signals hypothetically transmitted from the terminals in the sub-hypothesis based on spatial or space-time equalization to provide post-processed signals, and

determining signal-to-noise-plus-interference ratios (SNRs) for the post-processed signals for the terminals in the sub-hypothesis.

18. The method of claim 17, wherein the SNRs for the post-processed signals for the terminals are dependent on a particular ordering in which the terminals are processed, and wherein signals transmitted from the terminals are processed in an order defined by the selected sub-hypothesis.

19. The method of claim 17, wherein one sub-hypothesis is formed for each hypothesis, and wherein the ordering in the sub-hypothesis is based on the SNRs for the post-processed signals for the terminals in the hypothesis.

20. The method of claim 16, wherein the performance of each sub-hypothesis is evaluated based on a successive cancellation receiver processing scheme.

21. The method of claim 20, wherein the successive cancellation receiver processing scheme performs a plurality of iterations to recover signals hypothetically transmitted from the terminals in the sub-hypothesis, one iteration for each hypothetically transmitted signal to be recovered.

22. The method of claim 21, wherein each iteration includes

processing a plurality of input signals in accordance with a particular linear or non-linear processing scheme to provide a plurality of post-processed signals,

detecting the post-processed signal corresponding to the hypothetically transmitted signal being recovered in the iteration to provide a decoded data stream, and

selectively deriving a plurality of modified signals based on the input signals and having interference components due to the decoded data stream approximately removed, and

wherein the input signals for a first iteration are signals received from the terminals in the sub-hypothesis and the input signals for each subsequent iteration are the modified signals from a preceding iteration.

24. The method of claim 23, wherein the evaluating includes

processing a signal hypothetically transmitted from each terminal in the sub-hypothesis based on a particular receiver processing scheme to provide a post-processed signal, and

determining a signal-to-noise-plus-interference ratio (SNR) for the post-processed signal for each terminal in the sub-hypothesis.

25. The method of claim 23, wherein one sub-hypothesis is formed for each hypothesis, and wherein the ordering in the sub-hypothesis is selected based on priority of terminals in the hypothesis.

26. The method of claim 25, wherein a lowest priority terminal in the hypothesis is processed first and a highest priority terminal is processed last.

27. The method of claim 23, wherein one sub-hypothesis is formed for each hypothesis, and wherein the ordering in the sub-hypothesis is selected to achieve the best performance for the hypothesis.

30. The base station of claim 29, wherein the at least one receive processor is further operative to perform linear spatial processing on the received symbol streams.

31. The base station of claim 29, wherein the at least one receive processor is further operative to perform space-time processing on the received symbol streams.

32. The base station of claim 29, wherein the at least one receive processor is further operative to estimate a quality of each received symbol stream to derive the CSI for the associated decoded data stream.

33. The base station of claim 32, wherein the quality estimate is the signal-to-noise-plus-interference ratio (SNR) for the received symbol stream after spatial or space-time processing.

34. The base station of claim 29, wherein the set of one or more transmission parameters for each selected terminal includes a date rate for each data stream to be transmitted by the selected terminal.

35. The base station of claim 29, wherein the set of one or more transmission parameters for each selected terminal includes a coding and modulation scheme to be used for each data stream to be transmitted by the selected terminal.

37. The base station of claim 36, wherein each processing stage except a last stage includes

a channel processor configured to process the input symbol streams to provide a decoded data stream, and

a interference canceller configured to derive the modified symbol streams based on the decoded data stream and the input symbol streams.

38. The base station of claim 37, wherein each processing stage includes

a channel quality estimator operative to estimate a quality of the recovered symbol stream to derive the CSI for the associated decoded data stream.

39. The base station of claim 38, wherein the channel quality estimator is operative to estimate the signal-to-noise-plus-interference ratio (SNR) for the recovered symbol stream.

23. A method for scheduling data transmission for a plurality of terminals in a wireless communication system, comprising:

forming one or more sets of terminals for possible transmission on a channel, wherein each set includes a unique combination of terminals and corresponds to a hypothesis to be evaluated;

forming one or more orderings of the terminals in each set, wherein each terminal ordering corresponds to a sub-hypothesis to be evaluated;

evaluating performance of each sub-hypothesis;

selecting one of the plurality of evaluated sub-hypotheses based on their performance; and

scheduling the terminals in the selected sub-hypothesis for data transmission on the channel, and

wherein signals transmitted from the scheduled terminals are processed in an order defined by the selected sub-hypothesis.

28. A multiple-input multiple-output (MIMO) communication system, comprising:

a base station comprising

a plurality of front-end processors configured to process a plurality of signals received from a plurality of terminals to provide a plurality of symbol streams,

at least one receive processor coupled to the front-end processors and configured to process the symbol streams in accordance with a successive cancellation receiver processing scheme to provide a plurality of decoded data streams, and to further derive channel state information (CSI) indicative of channel estimates for the plurality of terminals,

a scheduler configured to receive the CSI, select a set of one or more terminals for data transmission on an uplink, assign a particular order of processing for the one or more selected terminals, and provide a schedule for the one or more selected terminals and their transmission parameters, and

a transmit data processor operatively coupled to the receive processor and configured to process the schedule for transmission to the one or more selected terminals; and

one or more terminals, each terminal comprising

at least one demodulator configured to receive and process one or more signals from the base station to recover the transmitted schedule, and

a transmit data processor configured to adaptively process data for transmission to the base station based on the transmission parameters for the terminal included in the recovered schedule.

29. A base station in a multiple-input multiple-output (MIMO) communication system, comprising:

a plurality of front-end processors configured to process a plurality of signals received from a plurality of terminals to provide a plurality of received symbol streams;

at least one receive processor coupled to the front-end processors and configured to process the received symbol streams to provide a plurality of decoded data streams and to derive channel state information (CSI) associated with the decoded data stream;

a scheduler configured to receive the CSI, select a set of one or more terminals for data transmission on the uplink and provide a schedule for the one or more selected terminals and a set of one or more transmission parameters for each selected terminal; and

a transmit processor configured to receive and process the schedule for transmission to the plurality of terminals, and

wherein the one or more data streams from each scheduled terminal are adaptively processed prior to transmission based in part on the transmission parameters for the terminal included in the schedule.

36. A base station in a multiple-input multiple-output (MIMO) communication system, comprising:

a plurality of front-end processors configured to process a plurality of signals received from a plurality of terminals to provide a plurality of received symbol streams;

at least one receive processor coupled to the front-end processors and configured to process the received symbol streams to provide a plurality of decoded data streams, each receive processor including a plurality of processing stages, each stage configured to process input symbol streams to provide a respective decoded data stream and derive channel state information (CSI) associated with the decoded data stream;

a scheduler configured to receive the CSI, select a set of one or more terminals for data transmission on the uplink, assign a particular order of processing for the one or more selected terminals, and provide a schedule for the one or more selected terminals and a set of one or more transmission parameters for each selected terminal; and

a transmit processor configured to receive and process the schedule for transmission to the plurality of terminals, and

wherein the one or more data streams from each selected terminal are adaptively processed prior to transmission based in part on the set of one or more transmission parameters for the selected terminal.

40. A terminal in a multiple-input multiple-output (MIMO) communication system, comprising:

at least one front-end processor configured to process at least one received signal to provide at least one received symbol stream;

at least one receive processor coupled to the at least one front-end processor and configured to process the at least one received symbol stream to recover a schedule for the terminal, wherein the schedule include an indication of a particular time interval in which the terminal is scheduled for data transmission and a set of one or more transmission parameters to be used by the terminal for the data transmission;

a transmit processor configured to receive and adaptively process data for transmission in accordance with the set of one or more transmission parameters, and

wherein the terminal is one of one or more terminals included in a set scheduled for data transmission in the particular time interval, and wherein the set of one or more terminals scheduled for data transmission is selected from among one or more sets of terminals based on performance evaluated for each set.

41. The terminal of claim 40, wherein the recovered set of one or more transmission parameters includes a coding and modulation scheme to be used for each data stream to be transmitted by the terminal.