# US 2014/0153667 A1 · Apparatus and method for transmitting and receiving signal of ofdm system

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- Number: US 2014/0153667 A1
- Document ID: US20140153667A1
- Status: Published application
- Kind: A1
- Application number: 13/866,174
- Filed: 2013-04-19
- Published: 2014-06-05
- Earliest claimed: 2012-12-05
- Assignees: Electronics and Telecommunications Research Institute
- Inventors: Jin Hyuk SONG; Jong Soo LIM
- Web page: https://patentgrep.com/patent/US20140153667A1

## CPC

- H04L 27/2634: {Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation}
- H04L 27/2614: {Peak power aspects}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A method and apparatus for transmitting an OFDM signal including converting a distribution of a signal in which inverse Fourier transform is performed in an OFDM system and a method of receiving an OFDM signal including expanding a received signal are provided, and by changing a magnitude distribution of a signal that is output from an OFDM modulator to a bimodal Gaussian distribution, an influence of noise in a receiving terminal can be reduced, and by limiting a signal that is output from an OFDM modulator to an appropriate magnitude, a phase in the receiving terminal can be prevented being wrongly demodulated.

## Claims

### Claim 1

A method of transmitting a signal of an orthogonal frequency division multiplexing (OFDM) system, the method comprising:
modulating a source bit to a symbol signal;
performing inverse Fourier transform of the symbol signal;
converting a distribution of the signal in which inverse Fourier transform is performed; and
transmitting the signal having a converted distribution.

### Claim 2 (depends on 1)

The method of claim 1, wherein the converting of a distribution of the signal comprises converting a Gaussian distribution of the signal in which inverse Fourier transform is performed to a bimodal Gaussian distribution.

### Claim 3 (depends on 2)

The method of claim 2, wherein the converting of a distribution of the signal further comprises limiting a phase of the signal in which inverse Fourier transform is performed to −π to π.

### Claim 4 (depends on 1)

The method of claim 1, wherein the converting of a distribution of the signal comprises performing a u-law expanding process of the signal in which inverse Fourier transform is performed.

### Claim 5 (depends on 1)

The method of claim 1, wherein the transmitting of the signal comprises;
modulating a phase of the signal having a converted distribution; and
transmitting the phase modulated signal.

### Claim 6

An apparatus for transmitting a signal of an OFDM system, the apparatus comprising:
a mapper that modulates a source bit to a symbol signal;
an inverse Fourier transformer that performs inverse Fourier transform of the symbol signal;
a signal distribution converter that converts a distribution of the signal in which inverse Fourier transform is performed; and
a transmitter that transmits the signal having a converted distribution.

### Claim 7 (depends on 6)

The apparatus of claim 6, wherein the inverse Fourier transformer converts a Gaussian distribution of the signal in which inverse Fourier transform is performed to a bimodal Gaussian distribution.

### Claim 8 (depends on 7)

The apparatus of claim 7, wherein the inverse Fourier transformer limits a phase of the signal in which inverse Fourier transform is performed to a range of −π to π.

### Claim 9 (depends on 6)

The apparatus of claim 6, wherein the inverse Fourier transformer performs a u-law expanding process of the signal in which inverse Fourier transform is performed.

### Claim 10 (depends on 6)

The apparatus of claim 6, wherein the transmitter comprises a phase modulator that modulates a phase of the signal having a converted distribution and transmits the phase modulated signal.

### Claim 11

A method of receiving a signal of an OFDM system, the method comprising:
estimating a phase value of a received signal;
expanding the received signal using the estimated phase value; and
performing a Fourier operation of the expanded signal and demodulating the signal in which a Fourier operation is performed.

### Claim 12 (depends on 11)

The method of claim 11, wherein the expanding of the received signal comprises performing a u-law expanding process of the received signal.