Mitigating Blind Detection Through Protograph Based Interleaving for Turbo Codes

The complexity involved to blindly detect the channel code parameters in the case of their imperfect knowledge is generally measured in terms of the minimum number of frames that an eavesdropper needs to observe for successful detection, adding an additional layer of privacy. In this work, starting from a defined almost regular interleaver for Turbo codes, we propose methods to construct a larger set of distinct interleavers that increases the minimum number of observations by a factor equal to the size of the constructed set. Furthermore, the generated sets of interleavers can be described by defining only a small number of parameters and are shown to achieve a comparable error correcting performance to base interleavers. To validate the proposed implementation-friendly method, an application example for information frame sizes $\mathrm{K}=128$ bits and $\mathrm{K}=512$ bits is provided for the construction of two sets of 8192 interleavers, prohibitively increasing detection complexity by state-of-the-art methods.