An application of direct sequence spread spectrum to unmanned aerial vehicle PPM control signal protection

Direct sequence spread spectrum (DS-SS) technique is widely used in modern telecommunications and it represents the latest advancement in radio control systems. In this paper we present an application of DS-SS technique for unmanned aerial vehicle (UAV) pulse position modulation (PPM) control signal protection. At first, recently reported scheme with (N+1) pseudonoise (PN) codes is described. One of them (PN₀) is assigned to the synchronizing pulse while the each of the remaining N codes (PN₁, PN₂, ... PN_N) corresponds to the appropriate channel. Owing to the specific structure of the transmitted signal it has been shown that only small amount of false alarms corrupts receiver performances. Furthermore, it has been pointed to the importance of the structure of the PN codes used. In this paper we calculate the percentage of false alarms that are corruptive and discuss the optimal choice of the set of PN codes.