Page 208 - 卫星导航2021年第1-2合期

Wang et al. Satell Navig (2021) 2:4 Page 8 of 9

satellite and the receiver processing spreading code
sequence need to be adjusted. The insert position and
time need to update, and the transmission and syn-
chronization of these updated information also need
additional resources, which is less flexible.
For the binary phase hopping based SCA technique,
to change the energy proportion of the authentica-
tion part in the signal, only the phase hopping ampli-
tude needs to be changed. The receiver does not need
to change the receiving mode and processing strategy,
which has high implementation flexibility.

Applicability analysis
Te modulation mode adopted in the simulation is Direct

Fig. 12 ROC performance ( C N = 35 dB·Hz) Sequence Spread Spectrum (DSSS)/QPSK, and code rate is
0
1.023 Mcps. In the design of a modern GNSS signal struc-
ture, subcarrier modulation and higher code rate are also
used for some signals. Compared with the proposed modu-
signal jitter are near the ideal eight phase points. Fig- lation method, the diference of the subcarrier modulation
ure 11 shows the constellation diagram of demodula- process is that it adds a subcarrier modulation module
tion with the steady-state value of dynamic stress error before the carrier modulation. Te corresponding demod-
θ e being 5°. Tere is a fxed deviation between the phase ulation in the receiver does not afect the constellation
points of the actual signal and the eight ideal phase diagram of the signal, which means it does not afect the
points. receiver authentication module. At the same time, higher
Figure 12 shows the ROC performance of authen- code rate will bring higher spreading gain, which can also
tication module for the cases that the root-mean- improve the performance of the receiver authentication
square error of phase jitter is 5° and 10°, the steady module. Terefore, the proposed scheme is suitable for
value of dynamic stress error is 5° and 10°, and C N modern GNSS signals.

0
is 35 dB·Hz. Compared with the ideal (i.e., without
error), the dynamic stress error hardly affects the Conclusion
ROC performance of authentication module, while the In this paper, a new SCA technique of the binary phase
phase jitter does, but not much deteriorate the ROC hopping based SCA technique is proposed. Te perfor-
performance. mance of this technique is compared with the inserting
chip based SCA technique through a simulation. In terms
of compatibility, the proposed technique is more com-
Flexibility analysis patible with the existing receiver architecture, and also
The premise of successful authentication is the correct reduces the impact on the receivers that do not participate
detection of the authentication code, which requires in identity authentication. In terms of authentication suc-
low false alarm probability and high detection prob- cess rate, the binary phase hopping based SCA technique
ability. The success rate of authentication is related has stronger anti-multiple access interference ability and
to the power and time of authentication signal. When higher authentication success rate in the same condition.
the total power of the signal is constant, the higher In terms of fexibility, the binary phase hopping based SCA
the power proportion of the authentication signal, technique is more fexible and easier to adjust. Te binary
the shorter the necessary time for successful authen- phase hopping based SCA technique provides an efcient
tication will be, otherwise the longer the authentica- implementation scheme for future GNSS security design.
tion time should be adopted. Therefore, there is a need
for a tradeoff between the authentication component Acknowledgements
Not applicable.
power proportion and the real-time authentication,
which can be adjusted if necessary. Authors’ contributions
For the inserting chip based SCA technique, if SW and HL accomplish thesis writing, simulation and modifcation; ZT
we want to change the percentage of unpredictable proposed the idea of this paper; BY assisted in carrying out the simulation. All
authors read and approved the fnal manuscript.
sequence inserted in the spreading code sequence,
the strategies of generating spreading sequence on the