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Radio Frequency Fingerprinting (RFF) is often proposed as an authentication mechanism for wireless device security, but application of existing techniques in multi-channel scenarios is limited because prior models were created and evaluated using bursts from a single frequency channel without considering the effects of multi-channel operation. Our research evaluated the multi-channel performance of four single-channel models with increasing complexity, to include a simple discriminant analysis model and three neural networks. Performance characterization using the multi-class Matthews Correlation Coefficient (MCC) revealed that using frequency channels other than those used to train the models can lead to a deterioration in performance from MCC > 0.9 (excellent) down to MCC < 0.05 (random guess), indicating that single-channel models may not maintain performance across all channels used by the transmitter in realistic operation. We proposed a training data selection technique to create multi-channel models which outperform single-channel models, improving the cross-channel average MCC from 0.657 to 0.957 and achieving frequency channel-agnostic performance. When evaluated in the presence of noise, multi-channel discriminant analysis models showed reduced performance, but multi-channel neural networks maintained or surpassed single-channel neural network model performance, indicating additional robustness of multi-channel neural networks in the presence of noise.

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Modern communication systems provide myriad opportunities for passive radar applications. Understanding the structure and potential of these signals becomes critical in the design and concept development process of passive radar systems. Although research exists for passive coherent target location, there is much to be explored in the passive radar imaging realm using signals of opportunity. This paper presents an evaluation of the IEEE 802.16-2009 WiMAX OFDM physical layer as a potential signal for a passive imaging radar system. The use of OFDM signals in radar imaging is explored and basic WiMAX imaging properties are discussed.