The ICI Canceller based on MMSE in OFDM

Abstract

During an OFDM transmission, a loss of sub-carrier orthogonality due to Doppler-spread of the channel leads to inter-carrier interference (ICI). This problem is especially bad in mobile reception environments. ICI causes significant degradation of the bit error rate characteristics and its influence becomes larger as the carrier frequency or velocity of the receiver increases. We have proposed a method to reduce the ICI caused by the Doppler spread of the channel. The transmission channel is modeled by a combination of multiple Doppler shifted propagation paths, and their parameters such as attenuation, relative delay and Doppler-shift are estimated using scattered pilot symbols. The ICI is canceled by multiplying the inverse matrix of the estimated channel matrix with the received OFDM symbol vector. However, the ICI canceller emphasizes a noise component, so it can't improve the bit error rate characteristics sufficiently. In this paper, we propose the ICI canceller based on MMSE which does not emphasize a noise component. Computer simulation confirmed that the ICI canceller based on MMSE can reduce the bit error rate more than ICI canceller based on zero-forcing under the Doppler-spread channel.