Mitigating jamming attacks in wireless broadcast systems

Wireless communications are vulnerable to signal jamming attacks that can block mission-critical messages from being received. Spread spectrum techniques mitigate these attacks by spreading normal narrowband signals over a much wider band of frequencies and forcing jammers who do not know the spreading pattern to expend much more effort to launch the attack. In broadcast systems, however, jammers can easily find out the spread pattern by compromising just a single receiver. Several group-based approaches have been proposed to deal with insider jammers who compromise receivers in broadcast systems; they can tolerate up to t malicious receivers as long as the system can afford 2t additional copies for each broadcast message. In this paper, we introduce a novel jamming-resistant broadcast system that organizes receivers into multiple channel-sharing broadcast groups and isolates malicious receivers using adaptive re-grouping. By letting receivers in different groups partially share their channels, this scheme reduces the extra communication cost from 2t to (2− ρ)t copies, where ρ is the channel sharing factor (0<ρ<1); this is much closer to optimal given the previously proven lower bound of t additional copies. In addition, we propose two extensions to the scheme to further improve the system performance: a sequential test-based scheme that saves communication costs without reducing security and an unpredictable channel assignment scheme that removes the requirement of operating on multiple channels at the same time, greatly reducing the required hardware complexity. We evaluate our schemes with analysis and simulation.