In this paper, a robust and efficient hybrid multitransmission scheme, previously introduced by the authors, is further investigated from the viewpoint of the encoder design, on the basis of its average distance spectrum. This scheme uses a channel coding system based on punctured turbo codes. Since the computation of the transfer function and, consequently, the union bound on the Bit or Frame Error Rate (BER or FER) of a punctured turbo code becomes highly intensive as the interleaver size and the puncturing period increase, a rapid method to calculate the most significant terms of the transfer function of a punctured turbo code is proposed and validated. The adopted channel coding system is based on the use of punctured turbo codes. This new scheme performs particularly well when the user has to cope with some random packet erasures due, e.g., to deep fading conditions on wireless links, or to congestions on wired networks. In this sense, it can be used for many different applications, e.g., in Automatic Repeat Request (ARQ) schemes, in Space-Time coding systems, in Multicast transmission of scalable sources using receiver driven hierarchical Forward Error Correction (FEC), and many others.
