An Improved Frequency Offset Estimation Based on Companion Matrix in Multi-User Uplink Interleaved OFDMA Systems

In this letter, we consider a multiuser uplink orthogonal frequency-division multiple access (OFDMA) system. To estimate the carrier frequency offset (CFO) efficiently, a modified pilot structure has been proposed to allow sufficient frequency separation between the subcarriers allocated to any two users. The proposed structure can reduce the ambiguity problem caused by the multiple signal classification (MUSIC) based algorithm when a CFO of one user is close to that of a different user. We present a CFO estimation method based on the companion matrix obtained using the received signal from the proposed pilot structure. Simulation results show that the proposed CFO estimator performs better than the conventional estimator and maintains its performance as the CFO range increases.