A Modified Direct-sequence Spread Spectrum Modulation Scheme for Burst Transmissions

The Direct-Sequence Spread Spectrum modulation (DSSS) is a very attractive modulation technique for military communication systems, mainly due to its resistance to interference and low probability of detection. However, the synchronisation to the spreading code phase in the receiver takes time, which makes this technique less interesting for sending very short messages. In this paper a novel direct-sequence modulation scheme for spread spectrum communication systems is presented, defined as the Delay-and-AddDirect-Sequence (DADS) modulation. The DADS spread spectrum modulation is easy to implement and there is no more need for code alignment at the receiver side, which makes it very suitable for short burst transmissions. The performance of the DADS technique is studied in Additive White Gaussian Noise (AWGN) and flat Rayleigh channels, as well as the influence of some important parameters in the modulation scheme.