Patent ID: 7719954

Claim:
A method for measuring signal strength caused by noise in a reception apparatus of a wireless communication system supporting Orthogonal Frequency Division Multiplexing (OFDM), the method comprising: receiving a time-domain preamble signal transmitted over a plurality of subcarriers by means of an OFDM frame transmitted from a transmission apparatus; converting the time-domain preamble signal into a frequency-domain preamble signal through Fast Fourier Transform (FFT); measuring signal strength at each of subcarriers to which no signal is transmitted by the transmission apparatus, from the frequency-domain preamble signal and calculating an average signal strength based on the measured signal strength; and determining signal strength caused by noise based on the avenge signal strength, wherein the frequency-domain preamble signal has a pattern in which signals are transmitted in the subcarriers disposed at regular intervals in an entire frequency domain according to a repetition period and no signal is transmitted in remaining subcarriers.