Patent ID: 7675888

Claim:
A method for Orthogonal Frequency Division Multiplexing Access (OFDMA) ranging in a communication system, said method comprising: receiving, at a base station (BS), a signal having a plurality of OFDMA symbols; performing, at the BS, a Fast Fourier Transform (FFT) on said plurality of OFDMA symbols; extracting, at the BS, a plurality of ranging codes from the results of said FFT; finding, at the BS, ranging codes matching a ranging code hypothesis; calculating, at the BS, Z k Z* k+1 , where Z k =Y k ×{circumflex over (X)} k , {circumflex over (X)} k is one of the ranging codes and Y k is the received signal, where k denotes subcarrier number and Z k Z* k+1 , is the product Z k and the complex conjugate of Z k+1 where “*” means the complex conjugate; summing, at the BS, Z k Z* k+1 values over all subcarriers k, for which subcarriers k and k+1 are both subcarriers used for ranging; estimating, at the BS, a transmit power by using the magnitude of said sum; and determining, at the BS, if the power for a given code is above a threshold.