PRECODER AND PRECODING METHOD IN A MULTI-ANTENNA SYSTEM

• US 20080181285A1
• Filed: 01/29/2008
• Published: 07/31/2008
• Est. Priority Date: 01/29/2007
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd., Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Samsung Electronics Co. Ltd., Board of Regents of the University of Texas System (University of Texas System)
• Inventors: KWUN, Jong-Hyung, SHIM, Sei-Joon, CHAE, Chan-Byoung, Heath, Robert, HWANG, In-Soo
• Granted Patent: US 8,204,142 B2
• Time in Patent Office: Days
• US Class Current: 375/148
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0439 utilizing channel inversion
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0632 Channel quality parameters, e.g. channel quality indicator [CQI]
• CPC Class Codes: H04B 7/0639 Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection

Abstract

A precoder and a precoding method in a multiuser multi-antenna system are provided. The precoder includes a channel checker for determining a DownLink (DL) channel condition of terminals in a service coverage area, a pre-compensator for pre-compensating, for channel distortion, signals to be sent to the terminals when a nonlinear algorithm is selected based on the channel condition of the terminals, and an interference remover for canceling interference in a channel by multiplying the pre-compensated signals by inverse channels of the terminals, and for canceling interference between the terminals. Accordingly, the pre-equalization can be carried out without global channel state information, and an increase of the transmit power can be prevented in the permutation.

Claims

1. A precoder in a multiuser multi-antenna system, comprising:

a channel checker for determining a DownLink (DL) channel condition of terminals in a service coverage area;

a pre-compensator for selecting a nonlinear algorithm according to a feedback scheme of channel state information from the terminals, and for pre-compensating, for a channel distortion of signals to be sent to the terminals by applying the selected nonlinear algorithm; and

an interference remover for canceling interference in a channel by multiplying the pre-compensated signals by inverse channels of the terminals, to cancel interference between the terminals.

2. The precoder of claim 1, wherein the channel checker determines the channel condition of the terminals using signals fed back from the terminals.

3. The precoder of claim 1, further comprising:

a scheduler for selecting terminals to be serviced based on channel state information of the terminals; and

an adaptive modulator for adaptively modulating signals to be sent to the terminals based on the channel condition of the selected terminals and for outputting the modulated signals to the pre-compensator.

4. The precoder of claim 1, wherein the pre-compensator selects a first nonlinear algorithm when the terminal, feed back the channel state information using at least one of an analog feedback scheme and a channel sounding scheme, and selects a second nonlinear algorithm when the terminals feed back the channel state information using a Channel Quality Indicator (CQI) scheme.

5. The precoder of claim 1, wherein the pre-compensator comprises:

a symbol generator for generating perturbing symbols based on the channel condition of the terminals to perform a vector perturbation, when the terminals feed back the channel state information using at least one of an analog feedback scheme and a channel sounding scheme; and

a symbol selector for selecting a perturbing symbol which minimizes a magnitude of a transmit power of the signals to be sent to the terminals from among the perturbing symbols generated at the symbol generator.

6. The precoder of claim 5, wherein the symbol generator generates the perturbing symbols using at least one of a minimum transmit symbol power algorithm and a minimum Peak to Average Power Ratio (PAPR) algorithm.

7. The precoder of claim 5, wherein the symbol generator generates the perturbing symbols using at least one of information relating to the terminals to be serviced, channel statue information of the terminals and adaptive modulation information.

8. The precoder of claim 1, wherein the pre-compensator comprises:

a symbol codebook for selecting perturbing symbols, based on the channel condition of the terminals, from a codebook which comprises perturbing symbols based on the channel condition for the vector perturbation, when the terminals feed back the channel state information using a CQI scheme; and

a symbol selector for selecting a perturbing symbol which minimizes a magnitude of a transmit power of the signals to be sent to the terminals from among the perturbing symbols selected at the symbol codebook.

9. The precoder of claim 8, wherein the symbol codebook generates the codebook using at least one of a Grassmannian algorithm, a Givens rotation matrix and a Lloyd algorithm.

10. The precoder of claim 8, wherein the symbol codebook selects the perturbing symbols in a predetermined codebook using at least one of information relating to the terminals to be serviced, channel state information of the terminals and adaptive modulation information.

11. The precoder of claim 1, wherein the interference remover comprises:

a pre-equalizer for canceling the interference in the channel by multiplying the pre-compensated signals by the inverse channels; and

an interference removing part for canceling the interference between the terminals from the pre-equalized signal.

12. The precoder of claim 11, wherein the pre-equalizer uses at least one of a Zero-Forcing (ZF) scheme and a Minimum Mean Square Error (MMSE) scheme.

13. The precoder of claim 1, further comprising:

an antenna mapper for mapping the interference-free signals to one or more antennas and transmitting the signals to the terminals.

14. A precoding method in a multiuser multi-antenna system, comprising:

determining a DownLink (DL) channel condition of terminals in a service coverage area;

selecting a nonlinear algorithm according to a feedback scheme of channel condition of the terminals;

pre-compensating for a channel distortion in signals to be sent to the terminals by applying the selected nonlinear algorithm;

canceling interference in a channel by multiplying the pre-compensated signals by inverse channels of the terminals; and

canceling interference between the terminals.

15. The precoding method of claim 14, further comprising:

selecting terminals to be serviced based on channel state information of the terminals; and

adaptively modulating signals to be sent to the terminals based on the channel condition of the selected terminals,

wherein the adaptively modulated signal is pre-compensated.

16. The precoding method of claim 14, wherein the selecting of the nonlinear algorithm comprises:

selecting a first nonlinear algorithm when the terminals feed back the channel state information using at least one of an analog feedback scheme and a channel sounding scheme; and

selecting a second nonlinear algorithm when the terminals feed back the channel state information using a CQI scheme.

17. The precoding method of claim 14, wherein the pre-compensating using the nonlinear algorithm comprises:

generating perturbing symbols according to at least one of information relating to the terminals to be serviced, channel state information of the terminals and adaptive modulation information, to perform a vector perturbation, when the terminals feed back the channel state information using at least one of an analog feedback scheme and a channel sounding scheme; and

selecting a perturbing symbol which minimizes a magnitude of a transmit power of the signals to be sent to the terminals, among the generated perturbing symbols.

18. The precoding method of claim 17, wherein the perturbing symbols are generated using at least one of a minimum transmit symbol power algorithm and a minimum Peak to Average Power Ratio (PAPR) algorithm.

19. The precoding method of claim 14, wherein the pre-compensating using the nonlinear algorithm comprises:

selecting perturbing symbols in a codebook which comprises perturbing symbols based on the channel condition to perform a vector perturbation, according to at least one of information relating to terminals to be serviced, channel state information of the terminals and adaptive modulation information, when the terminals feed back the channel state information using a CQI scheme; and

selecting a perturbing symbol which minimizes a magnitude of a transmit power of the signals to be sent to the terminals, among the selected perturbing symbols.

20. The precoding method of claim 19, wherein codebook is generated using at least one of a Grassmannian algorithm, a Givens rotation matrix and a Lloyd algorithm.

21. The precoding method of claim 14, wherein the channel interference is cancelled using at least one of a Zero-Forcing (ZF) scheme and a Minimum Mean Square Error (MMSE) scheme.

22. The precoding method of claim 14, further comprising:

mapping the interference-free signals to at least one antenna and transmitting the signals to the terminals.