Paper Performance Analysis of OFDM-IDMA and SC-FDMA-IDMA Scheme in Underwater Communication

Abstract

The IDMA scheme based receiver complexity over multi-path channels is related to the channel length. OFDM-IDMA scheme was proposed as an alternative to plain IDMA over multi-path channels. OFDM-IDMA scheme inherits most of the merits of OFDM and IDMA scheme. The key advantage of OFDM-IDMA scheme is that MUD can be realized efficiently with complexity per user, independent of the channel length and the number of users, which is significantly lower than that of other alternatives. Single Carrier Frequency Division Multiple Access (SC-FDMA-IDMA) scheme structure is achieved by adding Discrete Fourier Transform (DFT) and inverse DFT (IDFT) blocks at the transmitter and receiver respectively, so SC-FDMA scheme is sometimes referred to as DFT-spread or DFT-precoded OFDMA scheme. The transmitter of SC-FDMA scheme uses different subcarriers to transmit information data as in OFDMA scheme. However SC-FDMA schemes transmit the subcarriers sequentially rather than in parallel. Due to addition of above blocks low PAPR is obtained which is important to increase cell coverage and to prolong the battery lifetime of mobile terminals. There are no major differences between the BER performance of SC-FDMA-IDMA and OFDM-IDMA schemes, but SC-FDMA- IDMA scheme has low PAPR than OFDM-IDMA scheme.