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.