Recovery of unknown constraint length and generator polynomials for linear convolutional encoders in noise

In cases where the parameters of a forward error correcting encoder (the constraint length K and the generator polynomials) are unknown, they must be obtained before the message data can be recovered. The synthetic impulse response sequence (SIRS) algorithm, through observation and manipulation of the encoded output, composes a synthetic impulse response and from this sequence performs encoder parameter recovery. With these parameters in hand, selection of a suitable (Viterbi) decoder and recovery of message data is straightforward. We apply the SIRS algorithm in a noisy environment. The elements of the algorithm are extended to accommodate erroneous encoded data, and the impact of noise upon the probability of a correct solution are considered.