Semi-random interleaver design criteria

A spread interleaver of length N is a semi-random interleaver based on the random selection without replacement of N integers from 1 to N under a design constraint. This paper extends the spread-interleaver design method to multiple error events, based on the interleaver's role in overall turbo code error event distances. The extension helps to explain why the spread interleaver is specifically designed to be semi-random. Simulation results show the performance achieved for a symbol-interleaved parallel concatenated trellis coded modulation (PCTCM) scheme.