Issue In Cognitive Radio Research Articles

A survey on security issues in cognitive radio based cooperative sensing

Cognitive radio based cooperative spectrum sensing (CSS) is severely affected when some secondary users maliciously attack it. Two attacks regarded as key adversaries to the success of CSS are spectrum sensing data falsification (SSDF) and primary user emulation attack (PUEA). Defending SSDF and PUEAs has received significant attention in research in the past decade globally. This paper performs a state-of-the-art comprehensive survey of the researches on defending SSDF and PUEAs. First, the preliminaries like Hypothesis testing for detecting the primary user and different models of CSS are discussed briefly. Then a categorization of the defence mechanisms for defending both the attacks has been proposed as active and passive. Active mechanisms are suitable for an immediate defence in a limited time span, while passive mechanisms are suitable for flexible CSS systems that are ready to detect the attacks over a period of time and suppress them permanently by bringing changes in their underlying operations. An in-depth tutorial on both the defence mechanisms is provided from the perspectives of the secondary users throughput and the interference to the primary user. Finally, a detailed survey on the open research problems in this area and some possible solutions has been performed.

An urban expressway forwarding scheme for cognitive Internet of vehicles

The Internet of vehicles is an essential component for building smart cities that can improve traffic safety and provide multimedia entertainment services. The cognitive radio–enabled Internet of vehicles was proposed to resolve the conflict between the increasing demand of Internet of vehicles applications and the limited spectrum resources. The multi-hop transmission is one of the most important issues in cognitive radio–enabled Internet of vehicles networks. Nevertheless, most existing forwarding solutions designed for the cognitive radio–enabled Internet of vehicles did not consider the urban expressway scenario, where primary base stations are densely installed with small coverage areas. In this case, it is difficult to ensure that the sender and the receiver of the same cognitive radio link have similar channel availability statistics, which makes cognitive radio links more likely to be interrupted. To address this challenge, we develop a multi-hop forwarding scheme to minimize the end-to-end delay for such networks. We first formulate the delay minimization problem as a non-linear integer optimization problem. Then, we propose an approach to select the relay candidates by jointly considering the high mobility of vehicles and the unique cognitive radio spectrum usage distributions in urban expressway scenarios. Finally, we propose the low-latency forwarding strategies by considering the channel availability and the delay cost of different situations of relay candidates. Simulations show the advantages of our proposed scheme, compared with state-of-art methods.

A Survey on Security Issues in Cognitive Radio

Cognitive radio in recent times promises to solve our problem of scarcity of bandwidth and other natural resources. This paper presents a comprehensive survey of trends, issues of cognitive radio. Further, it also discusses the technological integration of cognitive radio, recent security attacks and countermeasures.

Routing Protocol for Cognitive Radio Ad Hoc Networks

Routing is an important issue in cognitive radio ad hoc networks (CRAHNs) owing to the stochastic activity of primary users (PUs). In particular, route stability remains an important issue in the CRAHN protocols. In this paper, the authors propose a stability-weighted cumulative expected transmission time (SWCETT) routing protocol. The SWCETT routing protocol aims towards providing the most optimal route based on both quality of service (QoS) metrics, such as delay and throughput, and stability of the route in the CRAHN. The performance of the SWCETT routing protocol is determined through simulations and compared with other routing protocols. The proposed routing protocol is capable of providing better delay and throughput than other routing protocols. The results prove the importance of the route stability metric in raising the performance of CRAHNs.

Research on Soft Computing Techniques for Cognitive Radio

Presently, the world of wireless communication is going under some crucial challenges, which attracts the attention of several researchers. Cognitive radio is defined as a multidimensional aware, autonomous radio system that learns from its experiences to reason, plan & decide future actions to meet user needs. Such a highly varied radio environment calls on intelligent management, allocation & usage of scarce resources. Issues like spectrum sensing & allocation, environmental learning i.e., adaptability & capability to learn attracts the attention of several soft computing learning & optimization techniques like neural networks, fuzzy logic, genetic algorithm & swarm intelligence. The cognitive engine behind the radio combines the sensing, learning, switching, and optimization algorithms to control & adapt the radio system from the physical layer to the top of the communication stack. This paper presents a critical review on different soft computing approaches applied over the cognitive radio issues & also points out different research directions over it.

Energy-Efficient Resource Management in OFDM-Based Cognitive Radio Networks Under Channel Uncertainty

In this paper, we investigate the energy consumption issue in cognitive radio (CR) networks. We aim to maximize the energy efficiency of the CR network while considering practical restrictions, including the power budget of the system, the interference thresholds of the primary users (PUs), the rate requirements of the secondary users, and the fairness among them. Particularly, due to the lack of explicit support from the PU system, perfect channel state information may not be acquired. Thus, the interference constraint is posed as chance-constrained form and tackled by Bernstein approximation. Then, we convert the optimization task into a quasi-convex problem via relaxing the integer variables, followed by a simple rounding technique to yield feasible subchannels assignment. We derive a fast algorithm to distribute power among subchannels by exploiting the structure of the power-allocation problem. Moreover, we give an efficient heuristic algorithm for subchannels assignment, which reduces the computation load dramatically. Simulation results show that both our proposed resource allocation schemes perform well in practical scenarios. The energy efficiency obtained by the integer subchannels assignment and the fast power distribution achieves more than 98% of the upper bound. On the other hand, the proposed heuristic subchannels assignment with optimal power allocation achieves a good tradeoff between computation complexity and energy efficiency.

Energy-Efficient Relay Selection Scheme for Physical Layer Security in Cognitive Radio Networks

Security is a critical issue in cognitive radio (CR) relay networks. Most previous work concentrates on maximizing secrecy capacity (SC) as a criterion to guarantee the security requirements in CR relay networks. However, under the requirement of “green” radio communication, the energy consumption is largely ignored. This paper proposes a relay selection scheme which jointly considers the best relay selection and dynamic power allocation in order to maximize SC and to minimize energy consumption. Moreover, we consider finite-state Markov channels and residual relay energy in the relay selection and power allocation process. Specifically, the formulation of the proposed relay selection and power allocation scheme is based on the restless bandit problem, which is solved by the primal-dual index heuristic algorithm. Additionally, the obtained optimal relay selection policy has an indexability property that dramatically reduces the computational complexity. Numerical results are presented to show that our proposed scheme has the maximum SC and minimum energy consumption compared to the existing ones.

Energy-Efficient Sensing for Delay-Constrained Cognitive Radio Systems Via Convex Optimization

Spectrum sensing is a critical issue in cognitive radio (CR) systems. When the energy of the CR system is constrained, using the energy efficiently is an important problem, which must be considered. In this paper, the energy efficiency is defined as the ratio of average spectrum efficiency of the CR system over average power consumed by the CR system. We consider a joint optimization of sensing time and power allocation to maximize the energy efficiency under the condition of sufficient protection to primary user and the delay constraint. It is demonstrated that convex optimization plays an essential role in solving the problem. An efficient iterative algorithm is proposed to obtain the optimal values. Then, we propose a block sensing scheme in which several adjacent frames are bundled as a block. Our results show that significant improvement in the energy efficiency is obtained via joint optimization of sensing time and power allocation. The energy efficiency and the delay performance can be further improved by using the proposed block sensing scheme.

Cognitive radio resource management exploiting heterogeneous primary users and a radio environment map database

The efficient utilization of radio resources is a fundamental issue in cognitive radio (CR) networks. Thus, a novel cognitive radio resource management (RRM) is proposed to improve the spectrum utilization efficiency. An optimization framework for RRM is developed that makes the following contributions: (i) considering heterogeneous primary users (PUs) with multiple features stored in a radio environment map database, (ii) allowing variable CR demands, (iii) assuring interference protection towards PUs. After showing that the optimal solution is computationally infeasible, a suboptimal solution is consequently proposed. Performance evaluation is conducted in terms of total achieved data rate and satisfaction of CR requirements.

An Approach to Efficient Spectrum Sensing in Cognitive Wireless Sensor Networks (C-WSNs)

Spectrum sensing is the most important issue in cognitive radio (CR) that increases spectrum utilization. Therefore, an accurate, reliable and real-time method to detect the unused spectrums and available bands is required necessarily. Several methods have been introduced for spectrum sensing, which the MultiTaper nonparametric estimation Method (MTM) is the most appealing. This method is not only an efficient technique for spectrum sensing in CR systems, but also is nearly optimal for wideband signals, providing a close approximation to the maximum likelihood (ML) estimation. In this paper, we propose using MTM efficient method to Cognitive Wireless Sensor Networks (C-WSNs), and compare our results with the case of using the periodgram for spectrum sensing.

Performance Evaluation of Multimedia Traffic Transmission Under Binomial and Poissonian Primary Traffics in Cognitive Radio Networks

Cognitive Radio is an enabling agile technology for communication and channels sharing in multimedia and wireless networks. The authors consider multimedia traffic transmission over Cognitive Radio (CR) networks using a progressive source coding associated to fountain codes. For a Cognitive Radio infrastructure where the spectrum is owned by Primary Users (PUs) that have Binomial and/or Poissonian traffics, Secondary Users (SUs) are allowed to share these spectral resources using the Opportunistic Spectrum Sharing feature of the Cognitive Radio concept. The objective of this paper lies in characterizing the reliability and as a result evaluating the performance of the secondary multimedia service provision under both primary traffic types in lossy Cognitive Radio environments. The authors have conducted a general analysis for many still open issues in Cognitive Radio and tackle three critical factors responsible for secondary service disruption: primary traffic interruptions, concurrent access to shared frequency bands leading to collisions and subchannels characteristics. Numerical simulations, in view of the average Spectral Efficiency, examine the performance of the multimedia transmission under the primary interruptions caused by the Binomial and the Poissonian primary applications and consider also the dynamics between the competing secondary peers in addition to subchannels fading and noise.

F2-MAC: an efficient channel sensing and access mechanism for cognitive radio networks

One of the most challenging issues in cognitive radio (CR) systems is channel sensing and accessing. In this paper, a CR channel access mechanism is proposed. The mechanism consists of two phases: fast channel accessing and proactive channel vacating. In fast channel accessing, a pair of CR users time-efficiently searches an available channel to deliver data. In proactive channel vacating, a pair of CR users periodically makes channel access opportunities to primary users (PUs) and vacates the occupied channel as quick as possible. We utilize the concept of channel hopping to reduce the average channel searching time. Furthermore, our vacating mechanism allows CR users to create opportunities for PUs to claim the spectrum and thus minimize the caused interference to PUs. We evaluate the performance of our approach through a two-dimensional Markov chain model as well as simulations. The performance study indicates that the proposed protocol achieves low channel searching time, high throughput, and fairness.

Guest Editorial - Advances in cognitive radio networking and communications (I)

The objective of this special issue is to bring together the state-of-art research results, designs, and industrial applications of cognitive radio (CR) networks and communications. We received 110 paper submissions and, after a careful review process to assess the quality of the papers, we accepted 37 papers, which will be published in this and the next IEEE Journal on Selected Areas in Communications (J-SAC) issue. In this issue, there are 18 papers, which cover spectrum sensing techniques, physical layer spectrum sharing optimization, cognitive radio design, and interference modeling. The first set of seven papers in this issue is related to spectrum sensing techniques. The second set of six papers is related to the design and optimization of spectrum sharing from a physical layer perspective. The third set of papers is related to CR design and interference modeling. In the next issue of 19 papers, the topics include medium access control, routing and Quality-of-Service (QoS) support in cognitive radio networks, spectrum auction and trading, and security issues in cognitive radio.

Cyclostationary Beacon for Assisting Spectrum Sensing in Opportunistic Spectrum Access

Cognitive radio is a promising solution to the problem of spectrum scarcity by means of allowing secondary radio networks access the spectrum opportunistically. One of the most important issues in cognitive radio is how to detect existing over-the-air signals reliably. Not a few literatures have reported that signals could be detected via their inherent or embedded properties. However, this approach may not be reliable and flexible enough for all kinds of signals with different modulation types. In this paper, we propose a type of multitone beacon signal carrying cyclostationary signatures, which is able to enhance the reliability and efficiency of signal detection at low cost of spectrum overhead. This beacon not only can indicate the presence or absence of user signal but also can reveal some other information helpful to opportunistic spectrum access through the information bits carried on its cyclostationary signatures. It could be applied to device/network identification, indication of spectrum allocation and spectrum rendezvous, both for primary and secondary users. Based on our previous work reported in [1], the generation and detection algorithm of the beacon signal are extended with improved spectral efficiency. Performance is discussed with both computer simulation and testbed validation.

Propagation Modelling Using Integral Equation Methods to Enable Co-existence and Address Physical Layer Security Issues in Cognitive Radio

In this paper it is envisaged that cognitive radios (CRs) consult a supporting network infrastructure for per-mission to transmit. The network server either grants or rejects these requests by estimating, from the CR’s geo-location and antenna features, the likely impact its transmission would have on incumbents and other CR devices. This decision would be based on a real-time radio environment map [1] which would be kept up to date with readings from CRs, sensors and dynamic radio propagation prediction. By this means coexistence with incumbents and other CRs can be satisfied. It is maintained here that integral-equation (IE) - based al-gorithms are suitable candidates for the propagation engine given their ‘automatic’ nature and that they can be implemented to give results arbitrarily close to the exact numerical solution. IE methods based on the Fast Multipole Method are examined as a likely route to achieve the accuracy and speed necessary for real-time propagation mapping. It is concluded that the results obtained using one of the most recent of these, the Field Extrapolation Method (FEXM) [2], are promising for rural/suburban profiles and could serve to enable co-existence, for example, in IEEE802.22 networks. It is also explained how dynamic propagation prediction can address some fundamental security threats to CR networks.

A Blind OFDM Detection and Identification Method Based on Cyclostationarity for Cognitive Radio Application

The key issue in cognitive radio is to design a reliable spectrum sensing method that is able to detect the signal in the target channel as well as to recognize its type. In this paper, focusing on classifying different orthogonal frequency-division multiplexing (OFDM) signals, we propose a two-step detection and identification approach based on the analysis of the cyclic autocorrelation function. The key parameters to separate different OFDM signals are the subcarrier spacing and symbol duration. A symmetric peak detection method is adopted in the first step, while a pulse detection method is used to determine the symbol duration. Simulations validate the proposed method.