Channel Coding Schemes Protection Against Jamming For Direct Sequence Spread Spectrum Telecommand Links

Space missions may be subject to intentional jamming attacks, which are particularly dangerous for Telecommand (TC) links. To counter the threat, error correcting codes, interleaving and direct sequence spread spectrum (DSSS) can be jointly used to limit the jamming impact on the system. The error correcting code currently included in the Committee for Space Data Systems (CCSDS) [1] and the European Cooperation for Space Standardization (ECSS) [2] recommendations for TC applications is the BCH(63, 56) code, with hard-decision decoding at the receiver side. In this paper we show that the performances of this code over jamming channels are not very good: the jamming attack may prevent a correct functioning of the system. This behavior confirms similar limitations emerged on the Additive White Gaussian Noise (AWGN) channel. In order to improve the scheme performance, more powerful codes are currently under study within CCSDS Working Groups. A study focusing on the performance of new, state-of-the-art, codes over the AWGN channel is presented in a companion paper [3], covering binary and non-binary Low-Density Parity-Check (LDPC) codes, turbo codes, soft-decision decoded BCH codes. In this paper we present the performance of these new schemes over pulsed and continuous wave jamming channels. Analysis on the impact of interleaving and DSSS processing gain are also provided. The results show that the new codes can achieve large gains with respect to the BCH(63, 56) code of the current recommendation. In many situations where the current code is not able to guarantee a proper functioning, because the jamming induces an unacceptable floor on the error rate performance, the new codes are able to limit the jamming impact.