A spectrum watermark embedding and extracting method based on spread spectrum technique

To effectively identify the radio equipment and quickly ascertain the radio interference, this paper presents a spectrum watermark embedding and extracting method based on spread spectrum technique. The spectrum watermark identifying the radio equipment is firstly modulated by the spread spectrum code whose code rate is very high and code length is very long in the transmitting terminal. Then it is periodically embedded in communication signals based on the additive rule. This method firstly detects whether the spectrum watermark exists, and divides the intermediate frequency communication signals into N segments in the receiving terminal. Then the spectrum watermark can be obtained by fusion decision based on the demodulation of these segmented signals. Theory analysis and simulation results show that the proposed method can effectively extract the spectrum watermark without harmful interference to normally demodulating of communication signals, and there is no need to demodulate the communication signal. The proposed method can effectively reduce the complexity of spectrum watermark extracting which provides a technique support for effectively identifying and ascertaining the radio equipment.