Interleaver and puncturing in turbo codes

Theoretically, turbo codes must be implemented with large block sizes. To reduce delay and complexity in practical communications systems, we need to utilize small block sizes. In these cases, interleaving and puncturing play important roles in the code performance. In this paper, we introduce an algorithm, called interleaver trellis, to analyze a specific interleaver. This will enable us to select the best interleaver among given, designed, or randomly generated interleavers when the bit error rate (BER) is considered as the performance criterion. Then we will design a good puncturing pattern for the selected interleaver to increase the code rate with the minimum degradation or even performance improvement.