On the Performance of Transport Control Protocol in Cognitive Radio Networks

Transmission Control Protocol (TCP) is the most commonly used transport protocol on the Internet. All indications assure that it will be an integral part of the future Internetworks. In this chapter, the authors present how regular TCP, which was designed for wired networks, is not suitable for dynamic spectrum access networks. They develop an analytical model to estimate the TCP throughput of dynamic spectrum access networks. Dynamic spectrum access networks deal with opportunistic spectrum access leading to greater utilization of the spectrum. The extent of utilization depends on the primary user’s traffic and also on the way the spectrum is accessed by the primary and secondary users. The proposed model considers primary and secondary user traffic in estimating the TCP throughput by modeling the spectrum access using continuous-time Markov chains, thus providing more insight on effect of dynamic spectrum access on TCP performance than the existing models.

The Impact of Regulations on the Business Case for Cognitive Radio

Cognitive Radio holds an interesting promise for improved utilisation of the radio spectrum. However, there is a considerable degree of uncertainty regarding the potential application of cognitive radio. One of the reasons for this uncertainty is the need for changes in the regulatory regime to allow for more dynamic forms of spectrum access. In addressing the necessary changes in regulations, the regulator should be well aware of the perspective of the entrepreneur. Eventually, it is the entrepreneur who invests in CR technology and thereby realises the goal of improved utilisation of the radio spectrum. This chapter addresses the impact on the business case for cognitive technologies of the regulatory regime and the choices on the fundamental CR technology that regulators will have to make.

Lending a Hand

Cooperative networking is considered one of the main enablers for achieving enhanced data rates in wireless communications. This is due to the fact that through cooperation the adverse effects of fading can be alleviated significantly. Thus, more reliable communication systems deployments can be devised, and performance enhancements can be achieved. In this chapter, the authors discuss the main aspects of cooperative networking starting from the main historical milestones that shaped the idea. Then they focus on the main mechanisms and techniques that foster cooperation and continue by studying performance metrics for various possible deployments, such as capacity bounds and outage probabilities. Finally, the authors take a more practical viewpoint and discuss aspects related to medium access control design and implementation that can serve as a stepping stone for the widespread deployment of cooperative networking.

Dynamic Resource Configurations for the Convergence of Optical and Wireless Networks

In the current landscape of Mobile Communication Networks, evolved radio access technologies, such as Long Term Evolution (LTE), offer higher bitrates to mobile end users, providing support for a range of resource-demanding applications. In this context, one can imagine that the full potential of the communication infrastructures can be unleashed, in a cost-effective way, by enabling a smart convergence between the evolved access of the mobile world and the Passive Optical Networks (PONs) of the fixed world. In this context, this chapter introduces a novel management system called CONFES, Converged Network Infrastructure Enabling Resource Optimization and Flexible Service Provisioning, aiming at the proactive determination of PON clients’ needs in bandwidth resources, and the efficient and reasonable allocation of resources to multiple clients according to such needs and the corresponding Service Level Agreements. Furthermore, the present chapter proposes, studies, and compares physical architecture solutions (both centralized and distributed) that can realize such advanced management systems.

Real-World Experimentation of Distributed DSA Network Algorithms

The problem of spectrum scarcity in uncoordinated and/or heterogeneous wireless networks is the key aspect driving the research in the field of flexible management of frequency resources. In particular, distributed Dynamic Spectrum Access (DSA) algorithms enable an efficient sharing of the available spectrum by nodes in a network without centralized coordination. While proof-of-concept and statistical validation of such algorithms is typically achieved by using system level simulations, experimental activities are valuable contributions for the investigation of particular aspects such as a dynamic propagation environment, human presence impact, and terminals mobility. This chapter focuses on the practical aspects related to the real world-experimentation with distributed DSA network algorithms over a testbed network. Challenges and solutions are extensively discussed, from the testbed design to the setup of experiments. A practical example of experimentation process with a DSA algorithm is also provided.

Spectrum Aggregation in Cognitive Radio Access Networks from Power Control Perspective

Spectrum scarcity has motivated researchers and standardization bodies to work towards flexible spectrum usage. One of the solutions, Spectrum Aggregation, as proposed by 3GPP, is a way to increase wireless capacity through providing additional bandwidth to users. This chapter presents the Spectrum Aggregation scenario as it is proposed to be incorporated in LTE-Advanced. Furthermore, the interesting extensions of FP7 SACRA European research project regarding Spectrum Aggregation are described. The business and the functional aspects stemming from the incorporation of this solution in the LTE-Advanced networks are presented in detail. From the functionalities that are the cornerstone of the Spectrum Aggregation, namely spectrum sensing, admission control, and power control, the latter one is studied, which is not thoroughly investigated yet, and the authors present its key features. Moreover, a typical power control algorithm is described and enhanced with learning capabilities and policies in order to meet the requirements of the Spectrum Aggregation scenario; the simulation results highlight the need for power control schemes in Spectrum Aggregation cases.

Resource Allocation Strategies in Cognitive Radio Networks Under QoS Constraints

The rapid growth of spectral resources’ demands, as well as the increasing Quality of Service (QoS) requirements of wireless users have led to the necessity for new resource allocation schemes which will take into account the differentiated QoS needs of each wireless user. Towards this direction, the researchers have introduced the concept of effective capacity, which is defined as the maximum rate that the channel can support in order to guarantee a specified QoS requirement. This concept has been considered as a “bridge” among the physical layer characteristics and the upper-layer metrics of QoS. During the last years, it has been widely employed for resource allocation problems in various wireless networks leading to efficient mechanisms. This chapter focuses on the employment of the effective capacity theory in Cognitive Radio (CR) systems, presenting an extensive survey on QoS-driven resource allocation schemes proposed in the literature. Some useful conclusions are presented and future research directions on this subject are highlighted and discussed.

Architectures and Information Signaling Techniques for Cognitive Networks

The introduction of self-awareness, self-management, and self-healing into networks leads to a novel paradigm known as cognitive networking. This chapter overviews recent developments of this concept, discussing possible cognitive node structure and candidate cognitive network architecture. It explains the functionality of cognitive algorithms and discusses opportunities for potential optimization. Furthermore, the concept of cognitive information services is introduced. Information signaling techniques are then classified, reviewed in details, and compared among them. Finally, the performance of cognitive communication protocols is presented for a choice of examples.

Security in Cognitive Radio Networks

While potentially solving the spectrum underutilization problem using methods such as dynamic and opportunistic spectrum access, Cognitive Radios (CRs) also bring a set of security issues and potential breaches that have to be addressed. These issues come from the two important capabilities implemented within CRs: their cognition ability and reconfigurability. This chapter focuses on identifying, presenting, and classifying the main potential security attacks and vulnerabilities, as well as proposing appropriate counter-measures and solutions for them. These are supplemented by simulation results and metrics, with the intention of estimating the efficiency of each of the observed attacks and its counter-measure. The presented simulations are performed in the proprietary C/C++ and Matlab/Simulink simulators. nSHIELD is a major ongoing European embedded systems security-related project, which is used to demonstrate the practicability of the potential implementation of the proposed countermeasures and solutions for the discussed security problems and issues.

Cognitive Techniques for the Development of Services in Broadband Networks

Information and Communication Systems have tremendously evolved in the past years. This has resulted to the respective increase of the use of communication systems, devices, and applications. To follow this evolution, the applications now focus not only on the delivery of each application, but also on adaptability, so as to meet users’ needs. This is aimed to be achieved by adapting to these needs in the most efficient and seamless way, thus offering an advanced experience to the user. To this end, this chapter focuses on an application of cognitive networks, presenting the mechanism by which self-adaptation can be added. More specifically, this chapter discusses e-learning management systems and showcases the methodology by which such a system may be adapted to users’ preferences and achieve effective learning. This is achieved by using vocabulary teaching as a specific instance of e-learning. Scenarios and the respective results of this methodology are also presented.