A novel pilot-based carrier frequency offset estimation in MC-DS-CDMA uplink

Carrier frequency offset (CFO) of different users in the multicarrier DS-CDMA (MC-DS-CDMA) system may violate the orthogonality among subcarriers and induce inter-carrier interference (ICI) and inter-user interference (IUI). This paper develops a new algorithm based on pilot clusters for CFO estimation of the uplink of MC-DS-CDMA system. By exploiting the low-pass property of fast Fourier transform (FFT) vector of the complex exponential function as well as the non-coherent property of the pilot clusters among users, we can obtain a signal matrix in the frequency domain at the receiver and the CFO of all users can be estimated from its row vectors, which are made up of the complex exponential function sequences including CFO of different users. Under the case of CFO in the fine tracking phase and the slowly time-varying flat-fading channel, the simulation shows that the mean value of the CFO estimation error is close to 0.01% subcarrier spacing when the signal to noise ratio (SNR) is 10 dB.