Method and System for Scheduling Users Based on User-Determined Ranks In A MIMO System

Abstract

In a wireless network comprising a plurality of subscriber stations and a base station capable of providing service to the subscriber stations, a subscriber station is provided that includes a rank selector and a scheduling data reporter. The rank selector is operable to select a rank for the subscriber station. The rank is operable to identify a number of antennas for transmitting data streams from the base station to the subscriber station. The scheduling data reporter is operable to report scheduling data, including the rank, to the base station.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:

FIG. 1 illustrates a wireless network capable of scheduling users based on user-determined ranks in a Multiple Input/Multiple Output (MIMO) system according to one embodiment of the disclosure;

FIGS. 2A-B are block diagrams of an orthogonal frequency division multiple access (OFDMA) transmitter and an OFDMA receiver, respectively, according to an embodiment of the disclosure;

FIG. 3 illustrates one of the subscriber stations of FIG. 1 according to one embodiment of the disclosure;

FIG. 4 illustrates details of the modulator of FIG. 2A in one of the base stations of FIG. 1 according to one embodiment of the disclosure;

FIG. 5 is a flow diagram illustrating a method for generating scheduling data in the subscriber station of FIG. 3 according to one embodiment of the disclosure;

FIG. 6 is a flow diagram illustrating a method for scheduling subscriber stations based on rank using the modulator of FIG. 4 according to one embodiment of the disclosure; and

FIG. 7 is a flow diagram illustrating a method for communicating data from the transmitter of FIG. 2A to the receiver of FIG. 2B according to one embodiment of the disclosure.

Claims

1. In a wireless network comprising a plurality of subscriber stations and a base station capable of providing service to the subscriber stations, a subscriber station comprising: a rank selector operable to select a rank for the subscriber station, the rank operable to identify a number of antennas for transmitting data streams from the base station to the subscriber station; anda scheduling data reporter operable to report scheduling data to the base station, the scheduling data comprising the rank.

2. The subscriber station as set forth in claim 1, the rank selector operable to select as a rank for the subscriber station one of low and high.

3. The subscriber station as set forth in claim 2, the number of antennas for transmitting data streams from the base station to the subscriber station identified by the rank of low comprising one; and the number of antennas for transmitting data streams from the base station to the subscriber station identified by the rank of high comprising M, M comprising a maximum number of antennas available for transmitting data streams from the base station.

4. The subscriber station as set forth in claim 1, the rank selector operable to select the rank once for each of a specified number of transmission time intervals (TTIs).

5. The subscriber station as set forth in claim 1, the rank selector operable to select the rank based on a capacity maximizing formula.

6. The subscriber station as set forth in claim 5, the capacity maximizing formula comprising the inequality log2(1+MRC)<Σi log2(1+MMSEi), the rank selector operable to select a rank of high when the inequality is satisfied and to select a rank of low when the inequality is not satisfied.

7. The subscriber station as set forth in claim 1, further comprising a channel quality indicator (CQI) calculator operable to calculate a CQI for each of a plurality of codewords received from each antenna of the base station based on the rank, the scheduling data further comprising at least one of the CQIs.

8. The subscriber station as set forth in claim 1, further comprising a pre-coding matrix selector operable to select a preferred pre-coding matrix from a set of pre-coding matrices for the subscriber station, the scheduling data further comprising the preferred pre-coding matrix.

9. The subscriber station as set forth in claim 1, the scheduling data reporter operable to report scheduling data comprising a first set of data when the base station is operating in a multi-user mode and to report scheduling data comprising a second set of data when the base station is operating in a single-user mode.

10. The subscriber station as set forth in claim 1, the scheduling data reporter operable to report scheduling data using one of explicit rank selection reporting and implicit rank selection reporting.

11. The subscriber station as set forth in claim 1, the subscriber station operable to decode frames received from the base station using hybrid automatic repeat request (HARQ) messaging.

12. A method for scheduling users in a base station based on user-determined ranks in a MIMO system, comprising: receiving scheduling data from each of a plurality of users, the scheduling data for each user comprising at least one CQI, a rank and a preferred pre-coding matrix; andscheduling the users based on the scheduling data.

13. The method as set forth in claim 12, scheduling the users based on the scheduling data comprising grouping the users into user groups, each user group comprising a same preferred pre-coding matrix.

14. The method as set forth in claim 13, scheduling the users based on the scheduling data further comprising: selecting a highest priority user group;selecting a specified number of highest priority users in the highest priority user group; andscheduling the specified number of highest priority users in the highest priority user group.

15. The method as set forth in claim 14, scheduling the users based on the scheduling data further comprising applying modulation and coding to a codeword for each of the highest priority users.

16. The method as set forth in claim 15, scheduling the users based on the scheduling data further comprising applying pre-coding to the modulated and coded codewords based on the preferred pre-coding matrix for the highest priority user group.

17. The method as set forth in claim 12, further comprising determining whether to operate in one of a multi-user mode and a single-user mode based on the scheduling data.

18. The method as set forth in claim 17, scheduling the users based on the scheduling data comprising scheduling a best user when operating in a single-user mode.

19. The method as set forth in claim 17, scheduling the users based on the scheduling data comprising scheduling a highest priority group of users when operating in a multi-user mode, the highest priority group of users comprising a same preferred pre-coding matrix.

20. A method for communicating between a transmitter and a receiver in a MIMO system, comprising: receiving a frame from the transmitter at the receiver, the frame comprising a plurality of codewords, each codeword corresponding to a different HARQ channel; andprocessing the frame using HARQ messaging.

21. The method as set forth in claim 20, processing the frame using HARQ messaging comprising: decoding a first codeword in the frame;determining whether the decoded first codeword is accurate; andsending a negative acknowledgement for the plurality of codewords from the receiver to the transmitter when the decoded first codeword is determined to be inaccurate.

22. The method as set forth in claim 21, further comprising, in response to the negative acknowledgement for the plurality of codewords, receiving a subsequent frame from the transmitter at the receiver, the subsequent frame comprising the same plurality of codewords.

23. The method as set forth in claim 22, the frame comprising two codewords, processing the frame using HARQ messaging further comprising: sending an acknowledgement for the first codeword from the receiver to the transmitter when the decoded first codeword is determined to be accurate;canceling the first codeword from the frame;decoding a second codeword in the frame;determining whether the decoded second codeword is accurate; andsending a negative acknowledgement for the second codeword from the receiver to the transmitter when the decoded second codeword is determined to be inaccurate.

24. The method as set forth in claim 23, further comprising, in response to the negative acknowledgement for the second codeword, receiving a subsequent frame from the transmitter at the receiver, the subsequent frame comprising a subsequent first codeword and the same second codeword.

25. The method as set forth in claim 24, processing the frame using HARQ messaging further comprising sending an acknowledgement for the second codeword from the receiver to the transmitter when the decoded second codeword is determined to be accurate; and in response to the acknowledgement for the second codeword, receiving a subsequent frame from the transmitter at the receiver, the subsequent frame comprising a subsequent first codeword and a subsequent second codeword.