Patent ID: 8520778
Filing Date: 2013-08-27
Classification: H04L

Abstract:
1. A method of determining carrier frequency offset (CFO) in OFDM beacon signal in Multi-input Multi-output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) based wireless communication systems, comprising: providing a MIMO-OFDM transmitter corresponding to the transmission of a beacon symbol allocated with a predetermined sequence of null subcarriers; providing an OFDM receiver corresponding to the beacon symbol transmitted from the transmitter; receiving the OFDM beacon signals on at least one receiving antenna and removing a cyclic prefix associated with each received OFDM beacon signal; combining the cyclic prefix removed signals using a diversity combining technique; converting the combined signals to the frequency domain by a N-point DFT operation including computing at the DFT output the energy content of all the N-subcarriers; computing the total energy of designated null subcarrier indices by introducing trial cyclic shifts from 0 to N−1; storing the total energy of the designated null subcarriers against the trail integer offset shift in an N-element array; and conducting a search to identify the minimum energy and the corresponding integer shift which represents the integer frequency offset experienced by the MIMO-OFDM signal.