Intercarrier interference self-cancellation scheme for OFDM mobile communication systems

For orthogonal frequency-division multiplexing (OFDM) communication systems , the frequency offsets in mobile radio channels distort the orthogonality between subcarriers resulting in intercarrier interference (ICI), This pape r studies an efficient ICI cancellation method termed ICI self-cancellation scheme. The scheme works in two very simple 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 t he receiver side, by linearly combining the received signals on these subca rriers with proposed coefficients, the residual ICI contained in the receiv ed signals can then be further reduced. The carrier-to-interference power r atio (CIR) can be increased by 15 and 30 dB when the group size is two or t hree, respectively, for a channel with a constant frequency offset. Althoug h the redundant modulation causes a reduction in bandwidth efficiency, it c an be compensated, for example, by using larger signal alphabet sizes. Simu lations show that OFDM systems using the proposed ICI self-cancellation sch eme perform much better than standard systems while having the same bandwid th efficiency in multipath mobile radio channels with large Doppler frequen cies.