Carrier Frequency Offset and Phase Noise Recovery in Correlated MIMO-OFDM Systems

Abstract

Many works have addressed the effect of CFO (Carrier Frequency Offset) and residual CFO (Phase Noise) on the performance of OFDM system, but few has been done to analysis the MIMO- (Multiple Input-Multiple Output) OFDM situation. In this paper, we provide an exact analysis of MIMO-OFDM performance in the presence of CFO and phase noise. A new CFO estimation method based on training sequences is proposed. The new method uses vector operation to calculate the fine frequency offset; it also reduces the noise energy and improves the signal-to-noise in the CFO estimation process. Since multiple antennas estimate the CFO, the MRC (Maximum Ratio Combining) technique is used. In this paper, adaptive phase noise mitigation (PNM) algorithm is also proposed. This method uses the pilots which insert in the data payload to track the rotation of channel response caused by residual CFO. For lower deviation, low pass filter is employed to the decision of sub-carrier after demodulation. Correlated MIMO channel TGn model is used to evaluate the performance of the proposed algorithm. With the maximum CFO (40ppm) requirement specified by the 802.11n Draft4.0 standard, simulation results show that the degradation is limited to within 3dB for the TGn channel model D and E in various modulations coding scheme (MCS) in 802.11n Draft 8.0. The results also show that the Bit Error Rate and Packet Error Rate can satisfy the requirement of the 802.11n Draft8.0