Frequency rotation for suppressing path interference and achieving large frequency diversity in uplink IFDMA

The novel frequency rotation techniques for suppressing the path interference and increasing the frequency diversity gain are proposed in uplink IFDMA system. In IFDMA, the path interference in multipath fading channel and the reduction of frequency diversity gain degrades the error rate performance, especially more significantly as the number of simultaneous access users becomes large. For suppressing the path interference and enlarging the frequency diversity gain, the frequency rotation has been proposed for down link access but it cannot be applied to the uplink due to the distortion of user frequency orthogonality. In the proposed frequency rotation, multiple users do not share the multiple frequency orthogonal channels and thus the orthogonality among the users can be maintained. The effect of the revised technique is shown by computer simulation.