Like other OFDM-based systems, OFDMA system is very sensitive to frequency synchronization errors, especially in the uplink channel where many mobile users have individually different CFOs (Carrier Frequency Offset). When many different CFOs exist, the orthogonality between the subcarriers will be lost so that 1CI (Inter Carrier Interference) as well as MAI (Multi-Access Interference) will be generated to disturb the received signal. Therefore, the system BER performance will be seriously degraded. Thus, research on the suppression to the interference caused by many different CFOs is of great importance. In this paper, we firstly analyze the interferences, including ICI and MAI, caused by multiple CFOs in the uplink channel of OFDMA system. Next, the suppression method based on block type pilots is proposed to overcome this interference simultaneously. From the simulation results, it can be seen that the multiple CFOs will make serious degradation to the system performance. However, by the proposed suppression processing method, the system performance can be significantly improved.
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