Bandwidth hopping spread spectrum (BHSS) has recently been proposed as a spectrum-efficient technique to combat jamming. In BHSS, the transmitter is randomly hopping the signal bandwidth in order to make it unpredictable to an attacker. When the signal bandwidth is unpredictable, the attacker cannot match its interference bandwidth to the signal bandwidth of the transmitter, and the receiver can filter out the interference power (or parts of it) prior demodulation, and thus increase decoding performance. The main challenge in BHSS is that the bandwidth must be hopping very rapidly at the symbol level in order to prevent a reactive jammer from following the hopping pattern by simple tracking techniques. Existing receiver filtering techniques as proposed in prior work require a long time to estimate the filter parameters and are thus unable to suppress the interference from the jammer when the bandwidth is hopping at the symbol level. In this paper, we propose a new filtering approach adapted for BHSS which is able to suppress arbitrary jamming interference even when the signal bandwidth is hopping after every symbol. Our approach is based on a filter bank which applies different filters in parallel and dynamically selects the best filter for every symbol according to the soft-state output of the demodulator. We evaluate the improvement of our method over classical filtering techniques in experiments using software-defined radios. Our results show a gain in interference suppression above 30 dB with respect to state-of-the-art solutions. We further implement frequency hopping for a BHSS system, and demonstrate the superiority of a system combining hopping in bandwidth, code and frequency against jamming attacks.

We present bandwidth hopping spread spectrum (BHSS), a novel technique to improve the jamming resistance of wireless communications. In BHSS, the bandwidth of a signal is hopped rapidly in a manner that is unpredictable to the jammer. We show in this work that by combining bandwidth hopping at the transmitter with adaptive filtering at the receiver, BHSS is able to improve the jamming resistance of the communication beyond the processing gain of conventional spread spectrum techniques such as DSSS and FHSS without an increase in RF spectrum requirements. We have designed and implemented a BHSS transmitter and receiver system on off-the-shelf software-defined radios. Our experimental results with different hopping patterns show that BHSS is able to boost the power advantage of spread spectrum communication by 8 to 20 dB for jammers of fixed bandwidth. When both transmitter and jammer hop randomly, the average power advantage we achieve with our system is 11.4 dB.