Towards physical layer identification of cognitive radio devices

Increasing demand has led to wireless spectrum shortages, with many parts of the existing spectrum being heavily used. Dynamic spectrum access (DSA) has been proposed to allow cognitive radio networks to use existing spectrum more efficiently. It will allow secondary users to transmit on already allocated spectrum on a non-interference basis. Cognitive radios are able to change bandwidth and other transmission characteristics to take greater advantage of this spectrum. It is necessary to identify all devices on the network in order to enforce spectrum access rules. Manufacturing variation cause minute differences in signals from supposedly identical devices. Physical layer identification (also called device fingerprinting) techniques allow identification of devices based on small but unique variation due to these imperfections. Fingerprinting is very sensitive to any changes in the signal capture setup or the device's environment. The changes in bandwidth that would occur in a DSA system cause device fingerprinting to fail. In this paper we extend current device identification methods to include identification of devices with changing bandwidth. Experimental results are demonstrated on a collection of over 50 transmitters, with a significant improvement over current methods.