Performance Analysis of Optimum Interleaver based on Prime Numbers for Multiuser Iterative IDMA Systems

Interleavers In Digital Communication

In communication systems, most of the well-known codes have been developed to combat against the noise that is assumed to be statistically independent. Typical channel model causing this type of noise would be Additive White Gaussian Noise channel (AWGN). However, there are some physical channels that show bursty error characteristics, such as multipath fading channel, in which fading often causes the signal to fall below the noise level and, thus, results in the burst type of error. Interleaving is frequently used in digital communication and storage systems to improve the performance of forward error correcting codes. Many communication channels are not memoryless: errors typically occur in bursts rather than independently. If the number of errors within a code word exceeds the error-correcting code's capability, it fails to recover the original code word. Interleaving ameliorates this problem by shuffling source symbols across several code words, thereby creating a more uniform distribution of errors.

Interleaving is a technique commonly used to overcome correlated channel noise such as burst error or fading (Rappaport, 2002; Tse, 2005; Olavarrieta, 2004). In interleaving mechanism, the input data rearranges itself such that consecutive data are split among different blocks. At the receiver end, the interleaved data is arranged back into the original sequence by the de-interleaver. As a result of interleaving, correlated noise introduced in the transmission channel appears to be statistically independent at the receiver and thus allows better error correction.