Cyclic interleaving scheme for an IFDMA system

Abstract

In this paper, a new interleaving scheme for an interleaved frequency division multiple access (IFDMA) system is proposed. The proposed scheme combines the advantages of code division multiple access (CDMA) with maximal length sequence (m-sequence) and orthogonal frequency division multiple access (OFDMA). Multiaccess interference (MAI) among users is eliminated by employing orthogonal carriers, and the intersymbol interference (ISI) due to multipath channels is minimized by using cyclic interleaving. Diversity gain is achieved in the proposed method with maximal ratio combining (MRC) in the case of a Rayleigh environment. Compared to complex multiuser (MU) detection, the detection process in the proposed method is relatively simple. Multipath orthogonality is achieved in the proposed method, avoiding the need for channel equalization. The proposed method is compared with the conventional interleaving employing well-known minimum mean square error frequency domain equalization (MMSE-FDE). The Monte Carlo simulation results prove the superiority of the proposed interleaving over conventional interleaving with MMSE-FDE, showing that the present scheme is suitable for both uplink and downlink mobile radio transmissions.