Page 205 - 卫星导航2021年第1-2合期

Wang et al. Satell Navig (2021) 2:4 Page 5 of 9

Fig. 5 Schematic diagram of using data-channel signal authentication

where ω o is the frequency of the local carrier, ϕ o,d is the When the receiver tracks pilot signal and data sig-
initial phase of the local carrier, and n i,d , n q,d are the nal independently, the above two methods are directly
noises of the I and Q channels, respectively. combined to get the normalized detection value V as
Equation (9) tells that to use the data channel for
authentication, it is necessary to eliminate the infuence V = V i + V q (18)
of data bits. First, the Q channel signal in Eq. (15) is cor- While if the receiver tracks pilot signal and data signal
related and integrated with the data channel spreading jointly, it is necessary to determine the phase relation
code c d and the phase hopping sequence c(k) respectively. between V i and V q according to the practical tracking
Te higher-order components will be cleared after the loop and make a right combination.
flter in the authentication module. Ten the infuence To use the above three methods, we only need to add
of data bit inversion is eliminated according to the data an identity authentication module in the classic tracking
bit estimation of the I channel. Next, to further improve loop. Table 1 shows the increase in hardware complexity,
C N , a coherent accumulation for the length of T coh is which is mainly refected in the number of code sequence

0
carried out, and the normalized detection value V q is generators and correlators.

V q = − P r2 (ϕ PH · π/180) (16)
Performance analysis
when θ is small, sin θ ≈ θ . Te threshold value V t is In order to verify the performance of the binary phase
hopping based SCA technique, this paper simulates the

V t = σ n −2 ln P fa (17) performance loss and detection probability, then com-
pares it with the inserting chip based SCA technique. It is
where σ n is the standard deviation of the noise, and P fa is assumed that the energy proportion of the authentication
false alarm probability. If V q is higher than V t , the authen- part is the same, i.e., (sin ϕ PH ) .
2
tication successes, otherwise fails.

3. Both data and pilot channels used for authentication