In this paper, we propose an adaptive carrier frequency offsets (CFOs) compensation scheme for uplink orthogonal frequency division multiple access (OFDMA) systems. In OFDMA receivers, CFOs break the orthogonality among the subcarriers and cause interchannel interference (ICI) and multi-user interference, which are the key impairment factors in OFDMA systems. In the proposed method, we compensate the CFOs in frequency domain by using the property that multiplication in time domain is achieved equivalently by circular convolution in frequency domain. Furthermore, to reduce the computational operations, we adopt different length of convolution filter according to the magnitude of CFO. Accordingly, the proposed method has lower computational complexity compared to the conventional fixed length convolution method under the same performance.
