Improved decoding of woven convolutional codes via hierarchical near-EEP code structure

A hierarchically designed channel coding scheme protects a few number of input data streams so–called layers with decreasing amount of redundancy from layer 0 to layer L. Such a code design clearly leads to unequal error protection, but as shown in [9] it can be superior in the average bit error rate compared to an equal error protection (EEP) design, if the protection of layers is not too different. This is due to the fact, that a near–EEP hierarchical design can match the properties of the iterative decoder. In this paper we extend the result to Woven Convolutional Codes (WCC) [8]. Based on asymptotical analysis of the convergence of iterative decoding by means of EXIT charts [4] we show that for infinite interleaver size the hierarchical structure is superior. Furthermore, we show that even for practical block sizes used in modern communication systems a significant improvement is possible by hierarchical design.