Abstract: The efficiency of CDMA system is degraded with number of user increases. CDMA is limited by (MAI) and (ISI) Hence when number of user increases the BER performance also increased. The main limitation in CDMA is that it involves separate coding and spreading operations. A method to enhance the performance of IDMA System turbo codes can be applied to IDMA system, called Turbo coded IDMA System, which is presented recently for combing the advantages of turbo and IDMA. We use regular Turbo coder is used. IDMA uses repetition code. To mitigate MAI and ISI, turbo type iterative MUD (Multi User Detection) is used. In contrast to CDMA, IDMA uses the iterative chip-By-chip (CBC) detection algorithm to overcome intra-cell Interference. An interleave-division multiple-access (IDMA) system supports the presence of multiple users in a cell by resorting to a different interleaver per user. The results Show that the TURBO CODED IDMA is better than other FEC code like convolution code and LDPC code under the same Parameters. Turbo coded IDMA Provide high speed of communication services and low cost of receiver. Turbo codes are used in 3G/4G mobile communications. And in (deep space) satellite communications as well as other applications.
Keywords: AWGN Channel, BPSK Modulation, IDMA, Matrix Interlever, Random interleaver, Random inter leaver, Turbo Encoder.