A subset of the synchronization algorithms in a wireless receiver are responsible for tracking the phase and frequency of a digitally modulated signal. If variations of the phase in the signal are substantial, then the receiver might be unable to track them leading to inability to demodulate the data. In this paper we propose a method for improving the secrecy of wireless communication by ensuring that an arbitrary unauthorized receiver (URx) cannot track these phase and frequency changes but a legitimate (LRx) one can. This is accomplished by introducing artificial variations in the phase of a wireless transmitted signal that exceed the capabilities of a certain class of receivers. We explore receivers that employ closed-loop synchronization, namely a phase-lock loop (PLL) and we devise an artificial frequency variation pattern that can de-synchronize it. Our results indicate that with our method the bit error rate (BER) of an URx can be maintained at a pretty high level even for very favorable channel conditions.

无线接收机中同步算法的一个子集负责跟踪数字调制信号的相位和频率。如果信号中的相位变化很大，则接收器可能无法跟踪它们，从而导致无法解调数据。在本文中，我们提出一种方法，通过确保任意未经授权的接收器（URx）不能跟踪这些相位和频率变化，但可以通过合法的（LRx）跟踪来提高无线通信的保密性。这是通过在无线传输信号的相位中引入超出某些类接收器能力的人为变化来实现的。我们探索采用闭环同步的接收器，即锁相环（PLL），我们设计了一种可以使其不同步的人工频率变化模式。我们的结果表明，使用我们的方法，即使在非常有利的信道条件下，也可以将URx的误码率（BER）维持在相当高的水平。