Military Communications and Information Technology: A Trusted ...

Chapter 4: Information Assurance & Cyber Defence
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and time of the analyzed signal on the receiver side. The principle of the synchronization
algorithm is based on the measurement of the value of angle phase difference between
two adjacent harmonics (8). For low values of drift m (or high, approaching N) the phase
difference value approaches 0 (or 2π). Therefore, the determined drift is encumbered
with high error. The best results are obtained for drift falling within 50-950 samples.
Synchronization accuracy can be improved by extending the time of the analyzed
signal on the receiver side or increasing the pilot line power (increasing the power
by 3 dB above the LT min level does not deteriorate the audio signal).
Figure 7. Synchronization accuracy in the function of drift
Figure 8. Synchronization accuracy in the function of signal analysis time
The results for extraction efficiency in the function of signal analysis time
on the receiver side are provided in Fig. 9. The analysis was carried out for drift
m = 10 samples and m = 300 samples, for two watermark signal power correction