An efficient ICI cancellation method in OFDM systems

Abstract

This paper studies an efficient ICI cancellation method for orthogonal frequency division multiplexing (OFDM) communication systems in which frequency offsets in mobile radio channels distort the orthogonality between subcarriers resulting in intercarrier interference (ICI). The scheme works in two steps. At the transmitter side, one data symbol is modulated onto a group of adjacent subcarriers with a group of weighting coefficients. The weighting coefficients are designed so that the ICI caused by the channel frequency errors can be minimized. At the receiver side, by linearly combining the received signals on these subcarriers with proposed coefficients, the residual ICI contained in the received signals can then be further reduced. The carrier-to-interference power ratio (CIR) can be increased as the group size is increased, for a channel with a constant frequency offset. Although the redundant modulation causes a reduction in bandwidth efficiency, it can be compensated. Simulations show that OFDM systems using the proposed ICI cancellation scheme performs much better than standard systems while having the same bandwidth efficiency in multipath mobile radio channels with large Doppler frequencies.