A Novel CFO Suppression Algorithm for OFDMA Uplink Communication System

In orthogonal frequency division multiple access uplink system, orthogonal multiple subcarriers are assigned to different users for parallel high data rate communications. However, carrier frequency offset (CFO), which is due to oscillator mismatches and/or Doppler shift, will destroy the orthogonality among subcarriers and introduce intercarrier interference (ICI) as well as multiple-access interference (MAI). Thus, system performance will be seriously degraded. To overcome this problem, it is of great importance to do research on suppression of the interferences caused by CFO. Especially, for the application services of the fast time-varying WiMAX, LTE and vehicular communication, the most important property of the suppression algorithm of the multiple CFOs effects is the efficient and high speed processing to compensate the ICI as well as MAI due to the multiple CFOs effects. In this paper, we propose a novel fast time domain inverse matrix receiver to suppress the interference of multiple CFOs. Compared with the conventional frequency domain direct ZF inverse matrix method, which has high complexity in obtaining the ICI matrix and its inverse matrix, the proposed method has very low complexity in obtaining the interference matrix. Furthermore, the signal after interference suppression is a frequency domain signal. Thus the FFT processing in conventional receiver can be skipped and receiver complexity can be simplified. Simulation results show that the proposed simple system works very fast and it does not show the serious error floor phenomenon in high SNR range and this algorithm has almost the same performance to the frequency domain direct ZF inverse matrix method.