  This paper investigates the anti-jamming performance of the NR-DCSK system.
We consider several practical jamming environments including broad-band jamming
(BBJ), partial-time jamming (PTJ), tone jamming (TJ) consisting of both
single-tone and multi-tone, and sweep jamming (SWJ). We first analytically
derived the bit error rates of the considered system under the BBJ and the PTJ
environments in closed-form expressions. Our derived results show that the
system performances under these two jamming environments are enhanced as $P$
increases, where $P$ is the parameter of the NR-DCSK modulation scheme denoting
the number of times a chaotic sample is repeated. In addition, our results
demonstrate that for the PTJ, the optimal value of the jamming factor is close
to zero when the jamming power is small, however, it increases and approaches
one as the jamming power enlarges. We then investigate the performance of the
considered system under the TJ and the SWJ environments via Monte-Carlo
simulations. Our simulations show that single-tone jamming causes a more
significant performance degradation than that provided by multi-tone jamming
counterparts. Moreover, we point out that the system performance is
significantly degraded when the starting frequency of the sweep jammer is close
to the carrier frequency of the transmitted chaotic signals, the sweep
bandwidth is small, and the sweep time is half of the transmitted bit duration.
