Deployment Of Cognitive Radio Networks Research Articles

Incorporating Primary Occupancy Patterns in Compressive Spectrum Sensing

Wideband spectrum sensing remains one of the challenging problems facing the wide deployment of cognitive radio networks. Compressive sensing (CS) was proposed as a promising approach to this problem by utilizing the sparse structure of the underutilized spectrum to capture the spectrum with fewer measurements and simpler hardware requirements. Most of the work in compressive spectrum sensing solely exploits the spatial- and frequency-domain structure of the spectrum neglecting the temporal structure arising from the regularity of primary user (PU) traffic patterns. In this paper, we explore the effectiveness of incorporating PU traffic patterns in compressive spectrum sensing. This achieves improved sensing performance by exploiting the statistics of the PU activity in the CS recovery algorithms. The experimental analysis through simulation shows that the proposed schemes can substantially improve the receiver operating characteristic performance at lower sampling rate noisy spectrum measurements.

Cognitive Radio Ad-Hoc Network Architectures: A Survey

Combating the growing necessity of radio spectrum, which is a limited natural resource, proper utilization of the radio spectrum is a must. Cognitive radio network (CRN) plays a vibrant role to solve this spectrum scarcity problem. Cognitive radio uses an open spectrum allocation technique to make more efficient utilization of the wireless radio spectrum and reduces the bottleneck on the frequency bands. Thus, accessible spectrum information is required for communication in CRN, which can be acquired by using spectrum database or by spectrum sensing. In addition, a robust architecture with appropriate communication protocol is preconditioned in the deployment of CRN. The state of the art of cognitive radio ad-hoc network architecture is surveyed in this paper, where the paper specifies the formation mechanisms and performance evaluations of the studied architectures. The reviewed papers have addressed some vital issues for the concrete deployment of cognitive radio ad-hoc network; however, there remain some issues that need to be addressed. Thus, this paper conveys a thorough and abstract understanding of cognitive radio ad-hoc network architecture, and also points out some open research issues in this area.

Power Control for Cognitive Radio Networks: Axioms, Algorithms, and Analysis

The deployment of cognitive radio networks enables efficient spectrum sharing and opportunistic spectrum access. It also presents new challenges to the classical problem of interference management in wireless networks. This paper develops an axiomatic framework for power allocation in cognitive radio networks based on four goals: QoS protection to primary users, opportunism to secondary users, admissibility to secondary users, and autonomous operation by individual users. Two additional goals, licensing and versatility, which are desirable rather than essential, are also presented. A general class of Duo Priority Class Power Control (DPCPC) policies that satisfy such goals is introduced. Through theoretical analysis and simulation, it is shown that a specific interference-aware power-control algorithm reaches such goals.

Anti-Jamming Games in Multi-Channel Cognitive Radio Networks

Crucial to the successful deployment of cognitive radio networks, security issues have begun to receive research interests recently. In this paper, we focus on defending against the jamming attack, one of the major threats to cognitive radio networks. Secondary users can exploit the flexible access to multiple channels as the means of anti-jamming defense. We first investigate the situation where a secondary user can access only one channel at a time and hop among different channels, and model it as an anti-jamming game. Analyzing the interaction between the secondary user and attackers, we derive a channel hopping defense strategy using the Markov decision process approach with the assumption of perfect knowledge, and then propose two learning schemes for secondary users to gain knowledge of adversaries to handle cases without perfect knowledge. In addition, we extend to the scenario where secondary users can access all available channels simultaneously, and redefine the anti-jamming game with randomized power allocation as the defense strategy. We derive the Nash equilibrium for this Colonel Blotto game which minimizes the worst-case damage. Finally, simulation results are presented to verify the performance.

Interference estimation and its applications in cognitive radio networks

Cognitive Radio (CR) has been proposed as a system-level means to improve the spectrum utilization efficiency. The most significant premise for CR networks is to avoid harmful interference to the licensed users. Therefore, it is very important to estimate the potential interference introduced by the deployment of CR networks so that CR networks can be coexistence with Licensed User (LU) networks by designing proper system parameters. In this paper, two statistical models of potential interference due to CR networks are developed based on transmitter and receiver oriented spectrum sensing schemes, respectively. The approximate probability distributions of aggregate interference introduced by CR networks are then derived with respect to the obtained models. With the help of these probability distributions, a method is further presented to get the critical system parameter, i.e., sensing distance and user density of the CR networks, so that the introduced interference can be controlled to predefined level. Numerical results validate the proposed interference estimation method and confirm the effectiveness of interference distribution based system parameter design.

Replacement of Spectrum Sensing in Cognitive Radio

Two major challenges exist in the development and deployment of cognitive radio networks: spectrum sensing and hidden terminal problem. In this research, we consider a network structure where the spectrum sensing task is separated from the unlicensed users (secondary users). The service provider for the secondary users needs to place sensing devices within the networks of licensed users (primary users). These sensing devices sense the primary users' activity. The sensing devices also decide whether to admit a secondary user's transmission. A new cognitive cycle is proposed accordingly. The proposed protocol is analyzed using the theory of Lame curve. The problem of optimally locating sensing devices and the properties of the proposed system are studied for single-user case and multi-user case. For the case without a separate control channel, a low temperature handshake technique is proposed for handshakes between the secondary users and the sensing devices. The other advantage of the proposed scheme is from the business model point of view: the expensive sensing devices will be implemented by the cognitive radio service provider, instead of being built in the secondary user devices which are usually consumer products demanding low cost.