Apparatus and method for reducing PAPR in an OFDM mobile communication system

• US 7,319,723 B2
• Filed: 11/08/2002
• Issued: 01/15/2008
• Est. Priority Date: 11/09/2001
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Ryu, Heung-Gyoon, Jin, Byoung-Il, Kim, In-Bae, Jung, Ki-Ho
• Primary Examiner(s): Ghayour; Mohammed
• Assistant Examiner(s): Malek; Leila
• Application Number:
  US10/290,950
• Publication Number:
  US 20030142754A1
• Time in Patent Office: 1,894 Days
• Field of Search: 375/396, 375/285, 375/345, 375/296, 375/295, 455/63.1, 455/114.2
• US Class Current: 375/296
• CPC Class Codes: H04L 27/2614 Peak power aspects

Abstract

Disclosed is an apparatus and method for reducing a peak-to-average power ratio (PAPR) due to multiple subcarriers in an OFDM (Orthogonal Frequency Division Multiplexing) mobile communication system. In the OFDM mobile communication system, a transmitter pre-emphasizes an output signal of an IFFT (Inverse Fast Fourier Transform) block, and a receiver de-emphasizes a received signal before FFT (Fast Fourier Transform), thereby efficiently reducing PAPR due to multiple subcarriers.

Claims

1. A method for controlling a value of symbols in order to reduce a peak-to-average power ratio (PAPR) in a transmitter for a mobile communication system for generating OFDM (Orthogonal Frequency Division Multiplexing) modulation symbols by performing IFFT (Inverse Fast Fourier Transform) on input data, the method comprising the steps of;

pre-emphasizing a symbol value S(n) with different gains according to whether the symbol value S(n) is less than a first prescribed reference value k₁ or not; and

converting a digital value S_pre of the pre-emphasized symbol value into an analog signal and amplifying the analog signal at a prescribed gain,

wherein the pre-emphasized symbol value for a case where the symbol value S(n) is less than the first prescribed reference value k₁ (0≦

S(n)≦

k₁) is defined as

$S_{\mathrm{pre}}<br><br>\left(n\right)=\frac{k_2}{k_1}<br><br>S<br><br>\left(n\right)$

where k₂ is a second prescribed reference value and the pre-emphasized symbol value for a case where the symbol value S(n) is greater than or equal to the first prescribed reference value k₁ (k₁≦

S(n)≦

L) is defined as

$S_{\mathrm{pre}}<br><br>\left(n\right)=\frac{L-k_2}{L-k_1}<br><br>S<br><br>\left(n\right)+L<br><br>\left(1-\frac{L-k_2}{L-k_1}\right)$

where L is a maximum value of the S(n); and

wherein the prescribed reference value k₁ is amplitude defined as a pre-emphasis change point.

2. An apparatus for controlling a value of symbols in order to reduce a peak-to-average power ratio (PAPR) in a transmitter for a mobile communication system for generating OFDM (Orthogonal Frequency Division Multiplexing) modulation symbols by performing IFFT (Inverse Fast Fourier Transform) on input data, the apparatus comprising:

a pre-emphasis block for pre-emphasizing a symbol value S(n) with different gains according to whether the symbol value S(n) is less than a first prescribed reference value k₁ or not;

a digital-to-analog converter for converting a digital symbol value S_pre output from the pre-emphasis block into an analog signal; and

a high-power amplifier for amplifying the analog signal from the digital-to-analog converter at a prescribed gain,

wherein the pre-emphasized symbol value for a case where the symbol value S(n) is less than the first prescribed reference value k₁ (0≦

S(n)≦

k₁) is defined as

$S_{\mathrm{pre}}<br><br>\left(n\right)=\frac{k_2}{k_1}<br><br>S<br><br>\left(n\right)$

where k₂ is a second prescribed reference value and the pre-emphasized symbol value for a case where the symbol value S(n) is greater than or equal to the first prescribed reference value k₁ (k₁≦

S(n)≦

L) is defined as

$S_{\mathrm{pre}}<br><br>\left(n\right)=\frac{L-k_2}{L-k_1}<br><br>S<br><br>\left(n\right)+L<br><br>\left(1-\frac{L-k_2}{L-k_1}\right)$

where L is a maximum value of the S(n); and

wherein the prescribed reference value k₁ is amplitude defined as a pre-emphasis change point.

3. A method for receiving by a receiver modulation symbols transmitted from a transmitter through IFFT (Inverse Fast Fourier Transform)-based OFDM (Orthogonal Frequency Division Multiplexing) in a mobile communication system, the method comprising the steps of:

low-noise-amplifying the modulation symbols and converting the amplified modulation symbols into digital symbol values;

de-emphasizing the symbol values S_pre(n) with different gains according to whether the symbol values S_pre are less than a first prescribed reference value k₂ or not; and

performing FFT (Fast Fourier Transform) on the pre-emphasized symbol values S(n),

wherein the pre-emphasized symbol value for a case where the symbol value S_pre(n) is less than the first prescribed reference value k₂ (0≦

S_pre(n)≦

k₂) is defined as

$S<br><br>\left(n\right)=\frac{k_1}{k_2}<br><br>S_{\mathrm{pre}}<br><br>\left(n\right)$

where k₁ is a second prescribed reference value and the pre-emphasized symbol value for a case where the symbol value S_pre(n) is greater than or equal to the first prescribed reference value k₂ (k₂≦

S_pre(n)≦

L) is defined as

$S<br><br>\left(n\right)=\frac{L-k_1}{L-k_2}<br><br>S_{\mathrm{pre}}<br><br>\left(n\right)+L<br><br>\left(1-\frac{L-k_1}{L-k_2}\right)$

where L is a maximum value of the S(n); and

wherein the prescribed reference value k₂ is amplitude defined as a pre-emphasis change point.

4. An apparatus for receiving modulation symbols transmitted from a transmitter through IFFT (Inverse Fast Fourier Transform)-based OFDM (Orthogonal Frequency Division Multiplexing) in a receiver for a mobile communication system, the apparatus comprising:

a low-noise amplifier for low-noise-amplifying the modulation symbols;

an analog-to-digital converter for converting the amplified modulation symbols into digital symbol values;

a de-emphasis block for de-emphasizing the symbol values S_pre(n) with different gains according to whether the symbol values S_pre are less than a first prescribed reference value k₂ or not; and

an FFT (Fast Fourier Transform) block for performing FFT on the pre-emphasized symbol values S(n),

wherein the pre-emphasized symbol value for a case where the symbol value S_pre (n) is less than the first prescribed reference value k₂ (0≦

S_pre(n)k₂) is defined as

$S<br><br>\left(n\right)=\frac{k_1}{k_2}<br><br>S_{\mathrm{pre}}<br><br>\left(n\right)$

where k₁ is a second prescribed reference value and the pre-emphasized symbol value for a case where the symbol value S_pre(n) is greater than or equal to the first prescribed reference value k₂ ≦

S_pre(n)≦

L) is defined as

$S<br><br>\left(n\right)=\frac{L-k_1}{L-k_2}<br><br>S_{\mathrm{pre}}<br><br>\left(n\right)+L<br><br>\left(1-\frac{L-k_1}{L-k_2}\right)$

where L is a maximum value of the S(n); and

wherein the prescribed reference value k₂ is amplitude defined as a pre-emphasis change point.