On the Estimation of Synchronous Scramblers in Direct Sequence Spread Spectrum Systems

In a non-cooperative context, the receiver has no information about communication parameters; therefore, it must perform communication forensics, which is the process of identifying what information it can from the collected data. This paper proposes a novel method for parameter estimation of synchronous scramblers in direct sequence spread spectrum systems. For the estimation, we use the bitwise relations inherent in the scrambling sequence and the repetitive patterns by the spreading code inherent in the scrambled sequence. Regarding computational complexity, previous studies of parameter estimation of synchronous scramblers require exponential computational complexities. Unlike the existing methods, our proposed method can practically estimate the feedback polynomial and initial state of the synchronous scrambler with polynomial computational complexity.