Patent ID: 7664192
Filing Date: 2010-02-16
Classification: H04B,H04L

Abstract:
1. A transmitter for minimizing a Peak-to-Average Power Ratio (PAPR) in a multi carrier communication system, the transmitter comprising: at least one transmit antenna; a precoder for coding input symbols so that signal rotation is generated, and generating a complex vector including the coded symbols; an encoder for performing a frequency-space mapping for the symbols generated as the complex vector according to an Alamouti scheme; a random mapper for randomly mapping the symbols for which the frequency-space mapping has been performed on a frequency plane through said at least one transmit antenna, and for performing a random selection of the symbols for adjacent sub-carriers; an Inverse Fast Fourier Transform (IFFT) unit for performing an IFFT for the symbols for which the frequency-space mapping has been performed; and a gradient algorithm unit for receiving IFFTed signals from the IFFT unit and for reducing the PAPR, wherein the gradient algorithm unit comprises: a P-waveform generator for receiving a predetermined number of tones having reserved positions among a total number of tone signals, and for generating a P-waveform having impulse characteristics; a peak detector for detecting a maximum peak value of complex output signals x after the IFFT; a position circulation movement unit for circularly moving a position of the P-waveform to a position of the detected maximum peak value; a phase rotator for harmonizing the circularly moved P-waveform with the phase of the maximum peak value detected on a complex plane; a scaling unit for scaling a value of the P-waveform such that it is smaller than a system setup PAPR; and a complex adder for performing complex addition for the complex output signals x after the IFFT and the scaled value, wherein the P-waveform is selected by repeating, a predetermined number of times, a process for randomly selecting the predetermined number of tones having positions reserved among the total number of tone signals, and wherein in the selection process, a value having a smallest power value is selected from remaining values except for a peak value from among values generated through the repetition.