Method and apparatus for reducing peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signal and transmitter

1. A method for reducing a peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal in a multiple-input multiple-output (MIMO) communication system, the method comprising:

estimating an interference level in a communication channel between a transmitter and a user terminal;

determining a clipping ratio (CR), based on the estimated interference level;

clipping the OFDM signal based on the determined CR; and

filtering the clipped OFDM signal,

wherein the estimating of the interference level comprises:

estimating a cross correlation level of the communication channel in response to the MIMO communication system performing a matched filter (MF) precoding;

determining the interference level based on the estimated cross correlation level,

wherein the interference level comprises an inter-user interference (IUI) level.

2. The method of claim 1 , wherein the determining of the CR comprises determining the CR to reduce a power of a clipping distortion to be less than a power of the interference level.

3. The method of claim 1 , wherein the determining of the CR comprises determining the CR based on at least one of an inter-cell interference level, an inter-carrier interference (ICI) level, an inter-user interference (IUI) level, or a result of calculating a sum of the IUI level, the inter-cell interference level, and the ICI level.

4. The method of claim 1 , wherein the determining of the CR comprises determining the CR based on at least one of a number of transmission antennas, a number of user terminals, or a communication bandwidth.

5. The method of claim 1 , wherein the estimating of the interference level comprises estimating at least one of an inter-carrier interference (ICI) or inter-cell interference in response to the MIMO communication system not performing the MF precoding.

6. The method of claim 1 , wherein the determining of the CR comprises:

determining the CR, based on an energy efficiency and an error vector magnitude (EVM) of the MIMO communication system.

7. The method of claim 1 , wherein the clipping and the filtering of the OFDM signal comprises clipping and filtering the OFDM signal repeatedly in a predetermined range.

8. The method of claim 1 , further comprising estimating a communication channel between a transmitter and a user terminal for configuring the MIMO communication system.

9. The method of claim 1 , wherein the estimating of the interference level comprises determining the interference level based on at least one of a number of transmission antennas, a number of user terminals, or a communication bandwidth.

10. A multiple-input multiple-output (MIMO) apparatus comprising:

an interference level estimator configured to estimate an interference level in a communication channel between a transmitter and a user terminal;

a clipping ratio (CR) determiner configured to determine a CR to be applied to an orthogonal frequency division multiplexing (OFDM) signal, based on the interference level; and

a clipper and a filter configured to clip the OFDM signal based on the CR and filter the clipped OFDM signal,

wherein the transmitter is configured to transmit the clipped and filtered OFDM signal to the user terminal, and

wherein the interference level estimator estimates the interference level by

estimating a cross correlation level of the communication channel in response to the MIMO communication system performing a matched filter (MF) precoding; and

determining the interference level based on the estimated cross correlation level,

wherein the interference level comprises an inter-user interference (IUI) level.

11. The apparatus of claim 10 , wherein the CR determiner is configured to determine the CR, based on at least one of an inter-user interference (IUI) level, an inter-cell interference level, an inter-carrier interference (ICI) level, or a result of calculating a sum of the IUI level, the inter-cell interference level, and the ICI level.

12. An apparatus for reducing a peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal, the apparatus comprising:

a channel estimator configured to estimate a communication channel between a transmitter and a user terminal in a multiple-input multiple-output (MIMO) communication system;

an interference level estimator configured to estimate an interference level in the MIMO communication channel; and

a clipping ratio (CR) determiner configured to determine a CR, based on the interference level, and to provide the determined CR to the transmitter,

wherein the transmitter is configured to transmit the clipped and filtered OFDM signal to the user terminal, and

wherein the interference level estimator estimates the interference level by

estimating a cross correlation level of the MIMO communication channel in response to the MIMO communication system performing a matched filter (MF) precoding; and

determining the interference level based on the estimated cross correlation level,

wherein the interference level comprises an inter-user interference (IUI) level.

13. The apparatus of claim 12 , wherein the CR determiner is configured to determine the CR to reduce a power of a clipping distortion to be less than a power of the interference level.

14. The apparatus of claim 12 , wherein the CR determiner is configured to determine the CR based on at least one of an inter-user interference (IUI) level, an inter-cell interference level, an inter-carrier interference (ICI) level, or a result of calculating a sum of the IUI level, the inter-cell interference level, and the ICI level.

15. The apparatus of claim 12 , wherein the CR determiner is configured to determine the CR based on at least one of a number of transmission antennas, a number of user terminals, or a communication bandwidth.

16. The apparatus of claim 12 , wherein the CR determiner is configured to determine the CR based on an energy efficiency and an error vector magnitude (EVM) of the MIMO communication system.

17. The apparatus of claim 12 , wherein the channel estimator is configured to estimate the communication channel based on at least one of an uplink pilot signal provided by a terminal or a channel sounding.

18. The apparatus of claim 12 , wherein the CR determiner is configured to:

increase the CR when energy efficiency of a power amplifier takes precedence over a clipping distortion; and

reduce the CR when maintaining an original signal takes precedence over the energy efficiency of the power amplifier.