Blind estimation of scrambler offset using encoder redundancy

Abstract

A self-recovering receiver for encoded and scrambled binary data streams is proposed in this paper. The generating polynomial of the scrambling sequence is known, as well as the encoder structure and coefficients, but the scrambler time offset is unknown. Taking profit of redundancy introduced by the encoder, we proposed a method which is able to estimate the scrambling sequence offset from the observed scrambled stream. The method is based on the projection of the observed data on the encoder orthogonal subspace. Once the offset has been estimated, classical data descrambling and decoding can be used to recover the information stream.