  In this paper, we present a simple technique to approximate the performance
union bound of a punctured turbo code. The bound approximation exploits only
those terms of the transfer function that have a major impact on the overall
performance. We revisit the structure of the constituent convolutional encoder
and we develop a rapid method to calculate the most significant terms of the
transfer function of a turbo encoder. We demonstrate that, for a large
interleaver size, this approximation is very accurate. Furthermore, we apply
our proposed method to a family of punctured turbo codes, which we call
pseudo-randomly punctured codes. We conclude by emphasizing the benefits of our
approach compared to those employed previously. We also highlight the
advantages of pseudo-random puncturing over other puncturing schemes.
