基于扩频的频谱水印嵌入与提取方法研究及实现

Research and implement of spectrum watermark embedding and extracting method based on spread spectrum

针对无线电系统身份识别问题,提出了一种基于扩频的频谱水印嵌入与提取方法,该方法中发射端首先选择一个码片速率高、码长长的扩频码来调制用于标识无线电系统身份的频谱水印信号,然后利用加性准则周期性地将其嵌入到无线电信号中.接收端首先将接收的中频信号分成N段,并对每段信号进行解扩和解调,最后利用N次解调结果实施综合融合判决来提取频谱水印.同时基于USRP平台构建了基于扩频的频谱水印嵌入与提取方法的验证系统,理论分析与实验验证结果表明:提出的方法能够在不对原始信号正常解调产生有害干扰的条件下,可有效提取频谱水印,具有较强的通用性和鲁棒性,为有效标识和识别无线电系统提供技术手段.

To effectively identify the radio system,this paper presents a spectrum watermark embed-ding and extracting method based on the spread spectrum.The spectrum watermark identifying the radio equipment is modulated by the spread spectrum code with high code rate and long code length at the trans-mitting terminal,and is periodically embedded in the communication signals based on the additive rule. The received intermediate frequency communication signal is divided into N segments at the receiving ter-minal.The spectrum watermark can be obtained by the fusion decision based on the demodulation of these segmented signals.The experiment system testing the proposed method is built based on the USRP plat-form.Theory analysis and experiment results show that the proposed method can effectively extract the spectrum watermark with no harmful inference to normal demodulation of the communication signal,and there is no need to demodulate the communication signal.The proposed method can effectively reduce the complexity of spectrum watermark extraction which provides a technique support for effectively identifying and ascertaining the radio system.