The recent increase in commercial availability of Remote Control Aircraft (RCA) has created numerous security and privacy concerns for the general public. In particular, RCAs jeopardize public safety in the already crowded airspace surrounding many large airports. An approach for protection from illegally operated RCAs is to utilize smart jamming methodologies against the frequency hopping radios commonly used in these applications. However, the abundance of radio manufacturers, along with their often closed or proprietary physical layer protocols, challenges existing smart jamming schemes. In this paper we propose a method to automatically synchronize in time and frequency with a frequency hopping radio at the physical layer by modelling the radio as a Hidden Markov Model (HMM). Our approach automates the determination of hop rates, hop frequencies, and timing of the target radio. We present multiple algorithms for identifying key HMM parameters and compare these algorithms using simulated data. We present the results of our HMM approach as we vary simulated noisy channel characteristics.
['John Narayan', 'T. Charles Clancy']
A Hidden Markov Model approach for automatic closed protocol hop synchronization