Coherent System Design for Cognitive Radio Networks

Cognitive radio (CR) is an emerging technique for wireless communication devices to autonomously discover free spectrum, and intelligently make dynamic spectrum access (DSAC) strategies to efficiently share the free spectrum with others. This research strives to design protocols for the cognitive radio network (CRN) so as to lay the foundation to apply the technique of CR in industry and deploy the CRNs in daily life.;At present, the progress of prescribing commercial CRN protocols is still in infant stage. The major reasons are: (1) conventional dynamic spectrum allocation (DSAL) algorithms with purpose of optimizing the spectrum utility being complicated and ignoring the constraints of realistic communication services; (2) the lack of work dedicated to providing a platform for executing DSALs; (3) the ignorance of the indispensible role of the security issue for the CRN. Therefore, our researches are dedicated to the design of practical DSAL algorithms, DSAL driven MAC frameworks and security mechanisms.;In this research, we improve conventional DSALs to be more practical and simpler from two ways: one is to embed the quality-of-service (QoS) requirement into the DSAL process, which results in our QoS aware DSALs; the other is to control the interference between CRs under negligible scale through regulating transmission power or refraining links with strong interference from simultaneously transmitting, which derives our IT-DSALs.;For the DSAL driven MAC framework design, the current research focuses on the game theoretic DSAL driven MAC framework since game theory model most seamlessly describe the interactive and adaptive behaviors of CRs. Based on the analysis of challenges for executing the game theoretic DSAL we design a unified game theoretic DSA-driven MAC framework.;Moreover, we work on unique security issues directly related to DSA C paradigm in CRN. At current stage, following issues are investigated: (1) primary user emulation (PRE) defense system. The PRE attack is a unique attack in CRNs, where adversary CRs misuse the protection law of CRs to the primary receiver (PR) to pretend as PRs so as to keep benign CRs from accessing the freed spectrum. The defense mechanism is composed of signature design for PR authentication, as well as the design of public key infrastructure. (2) DSAC based confidentiality. The DSAC paradigm contributes intrinsic security capability to the CR by hiding information in the unpredictable spectrum access patterns. In this research, we systematically formalizes the Frequency Hopping DSA (FH-DSAC) based cryptography by introducing the model of dynamic bit (dybit) whose state indicates both the binary value and the DSAC strategy. With the FH-DSAC cryptography model, we investigate FH-DSAC secure data communication (FH-DSA C-SDC) in both centralized and distributive CRNs.