New advances in multi-carrier spread spectrum techniques for tactical communications

Spread spectrum techniques are classically used in tactical communications, in order to mitigate interference due to jamming, while providing a low probability of intercept. This paper addresses a new SS technique, referred to as multi-carrier spread spectrum (MC-SS). An original MC-SS scheme is proposed using polyphase filtering. As for tactical communications, dramatic performance improvements are achieved, especially for partial-band jammers. Moreover, classical problems of synchronization encountered in multi-carrier modulation systems (MCM) are resolved by the proposed waveform. This provides an extremely good safety level. The MC-SS technique consists in a combination of standard DS/SS with a MCM scheme. Such a combination is motivated by the advantages of the MCM, which provides robustness in the case of frequency selective channels, as well as an efficient digital implementation in its well known OFDM form (implemented in DAB, DVB, ...). The paper highlights that this new MC-SS method fits tactical communications constraints. It shows that this new modem proposes an active and reliable method to combat agile jammers. Special attention is paid to synchronization issues. For tactical communications, this leads to a new protection feature.