Dynamic time-warp compensation for correlation of long sequences

Dynamic time-warping of direct-sequence spread-spectrum causes a deterioration in the process gain when time-linear correlation is applied. Applications with channels that suffer this effect are moving platforms such as to airborne communications, acoustic communications, and tape recorders. Of these, the tape recorder has the most severe time-warp. This paper describes a low powered PN-sequence which is added to the audio, such that the audible quality is not impaired. This is used for authentication of the tape recording. Tape speed errors from wow and flutter cause time based errors and a loss of the detection process gain. A technique for recovering the process gain and detecting the PN-sequence from this channel using a dynamic programming algorithm is presented