In this paper, we study tactical covert timing networks with dynamic spectrum access capability amidst adversaries. We present a two-tier game framework to model the attackdefense scenario. There are very few studies available in the literature on covert timing channels with multiple parallel transmissions. This paper presents a new paradigm combining the time diversity provided by covert timing channels and frequency diversity provided by dynamic spectrum switching, to combat jamming. The dynamic sensing of different spectrum bands and subsequent jamming by the attacker, and the camouflaging defense by the covert network are modeled as a two-tier game. We present a dynamic minimax camouflaging strategy for the covert network and sensing and jamming strategies for the attacker. We compare the performance of our proposed equilibrium strategies with that of other well known strategies and demonstrate the effectiveness of our proposed solution. We use theoretical analysis, simulations and testbed experiments to illustrate our ideas. I.

personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission.

allow a Cognitive Radio (CR) device to opportunistically access unused or less crowded spectrum while ensuring protection for the incumbents. Though DSA shows great potential to enhance spectrum efficiency, the associated constraints on QoS may limit its usefulness. QoS support in a DSA-based network is not trivial due to the fact that in addition to unfavorable characteristics of the wireless medium, the secondary devices are subject to additional interference and interruption from incumbents. In this paper, we present a case-study of key QoS provisioning techniques in DSA protocol design that facilitate the required application QoS. Specifically, we consider a CR system that supports high quality multimedia (including HDTV) streaming over UHF frequency bands. We model and evaluate the QoSoriented CR system together with the underlying QoS-Provisioned DSA Protocol (referred as QPDP) through extensive simulations. The results show the effectiveness of DSA coupled with QoS provisioning, in supporting QoS-demanding consumeroriented network applications in TV bands. This outcome is significant as FCC has recently approved UHF bands for unlicensed operations in the second Report and Order in the USA, and various DSA-based personal/portable CR systems are being actively considered by the consumer wireless industry. Keywords—QoS provisioning, DSA, cognitive radio I.

Abstract Dynamic Spectrum Access (DSA) is a promising solution to the problem of spectrum inefficiency. Based on Cognitive Radio (CR) technology, DSA allows a CR device to opportunistically access unused or less crowded spectrum while ensuring protection for the incumbents. Though DSA shows great potential to enhance network performance, its adverse side-effects on application QoS may limit its usefulness. QoS support in a DSAbased network is not trivial due to the fact that in addition to unfavorable characteristics of the wireless medium, the secondary devices must face additional interference and interruption from incumbents that have to be protected. In this paper, we present a case study of key DSA protocol characteristics necessary for QoS provisioning. Specifically, we consider a personal/portable CR system that supports high quality multimedia (including HDTV) streaming over UHF frequency bands. We model and evaluate the QoS-oriented CR system together with the underlying QoS-Provisioned DSA Protocol (called QPDP) through extensive simulations. The results show the effectiveness of the proposed DSA QoS provisioning approach in sustaining high levels of QoS, e.g., supporting HDTV streaming in TV bands. This outcome is significant as FCC has recently approved UHF bands for unlicensed operations in the USA, and various DSA-based CR systems are being actively designed by the wireless industry. The techniques outlined in this work can be generalized to be applicable to generic DSA design in various spectrum bands. A. Kumar (B) · K. G. Shin

Professor Kang G. Shin, for his constant encouragement and support during the course of my doctoral study. His guidance, insights, and strong pursuit of excellence have helped my growth tremendously, both professionally and as a person. I also thank my dissertation committee members—Professors Morley Mao, Prabal Dutta, and Ted Zellers for their valuable feedback and suggestions that resulted in a greatly improved PhD work. I wish to acknowledge my parents who have constantly given me endless love and encouragement at every stage of my life. This dissertation is dedicated to them. I also thank my dear sister and brother-in-law for their support through the highs and lows of this phase. I want to specially mention my nephew little Arnav whose playful frolics always cheered me up during every visit. I am also grateful to my talented colleagues, whose invaluable comments and critical input improved the quality of my work. I thank the present and former RTCL members, especially Hyoil Kim, Alex Min, Kyu-Han Kim, Xin Hu, Xinyu Zhang, Eugene Chai, and others. I am also thankful to my collaborators and former

Abstract—Spectrum sensing is essential in cognitive radio to enable dynamic spectrum access. In many scenarios, primary user signal must be detected reliably in low signal-to-noise ratio (SNR) regime under required sensing time. We propose to use stochastic resonance, a nonlinear filter having certain resonance frequency, to detect primary users when the SNR is very low. Both block and sequential detection schemes are studied. Simulation results show that, under the required false alarm rate, both detection probability and average detection delay can be substantially improved. A few implementation issues are also discussed. Keywords—spectrum sensing, stochastic resonance I.