Spectral Efficient IDMA System Using Multi User Detection

With the prevailing CDMA, high information rates are often achieved by reducing spreading factor or adopting multi-code CDMA, however the previous leads to reduced spreading gain against fading and interference, and latter has to overcome the interference among spreading sequences. In contrast, high rate transmission can be achieved in IDMA systems by assigning the FEC codes with high coding rates. Neglecting intra-cell interference at low computational price the multiple access interference (MAI) could be a major concern for both CDMA and IDMA cellular networks. The present CDMA mitigates the MAI by multi-user detection (MUD). However, the high computational price concerned in MUD that limits the high range of userapplication in practical systems. In distinction to CDMA, IDMA uses the iterative chip-by-chip (CBC) detection formula to combat intra-cell interference. The per-user computational quality of the CBC is independent of the quantity of users concerned. It achieves multi-user gain in the case of each user with a rate constraint. The features of IDMA distinguished from the other MA techniques should be thought-about in MAC design for IDMA based networks. IDMA involves dynamic power management to boost link capacity and guarantee QoS for users. So, IDMA will perform better for large range of users. It supports asynchronous transmission. The orthogonal MA technologies, like time-division multiple-access (TDMA), frequency-division multiple-access (FDMA) and orthogonal-FDMA (OFDMA), need frame synchronization to keep up orthogonality. In IDMA networks, there's no subtle synchronization demand on data transmission. Keywords— Orthogonal-FDMA; inter symbol interference; orthogonality; interleaver; IDMA.