One-Time Spectrum Coexistence in Dynamic Spectrum Access When the Secondary User May Be Malicious

The reliable coordination of communication channels between two organizations is becoming an increasingly important problem as we move toward cognitive radio systems that support dynamic spectrum access. The benefit of such coordination is clear in scenarios when both participants are completely benign, but such benefits can be easily negated if one of the participants operates in a manner contrary to their channel assignment. In this paper, we develop and explore a maxmin transmission protocol for a primary user (PU) in a multiband wireless network, where the secondary user (SU) may be malicious and have an intent to cause interference. In this case, the threat that a SU may be an adversary changes the problem and places the PU in a dilemma: 1) if the SU is an adversary then to decrease the probability of interference it is better for the PU to select which channels it uses from a larger set of bands (i.e., possibly even including the bands reserved for the SU) and 2) if the SU turns out to be law obedient, then using a larger set of bands leads to an increased chance of being interfered with. Similarly, the SU also faces a dilemma if he is malicious: if the PU thinks that the SU is law obedient, then to increase the probability of jamming, the SU should target only the bands reserved for the PU; while, if the PU thinks that the SU is malicious, then by switching to the bands reserved for the SU, the probability of interference can be significantly or even totally reduced. Using game-theoretical tools, we formally explore these dilemmas and use the resulting analysis to explore the tradeoffs between different strategies in terms of payoffs to each user and knowledge of the SU´s characteristics.