Direct sequence spread spectrum scheme for an unmanned aerial vehicle PPM control signal protection

Abstract

In this letter, a new direct sequence spread spectrum scheme for protection of an unmanned aerial vehicle (UAV) binary pulse-position modulated (PPM)control signal is proposed. The UAV PPM control signal consists of data frames. Each of them contains a synchronizing pulse followed by a number of shorter pulses equal to the number of channels N. At the beginning of any pulse is the pause long 0.3ms. The proposed scheme uses (N + 1) pseudonoise (PN) codes: one of them (PN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) is assigned to the synchronizing pulse while the each of the remaining N codes (PN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , PN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , ... PN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub> ) corresponds to the appropriate channel. The same PN code is transmitted during the pause and the pulse which follows the pause. At the receiving side, the set of (N + 1) passive correlators is used to detect respective PN codes. Proposed scheme requires neither PN code tracking process nor data demodulation, so is resistant to timing jitter. Performance measures of the proposed scheme are calculated.