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  • 1.
    Martinez-Bauset, Jorge
    et al.
    Blekinge Institute of Technology, School of Computing.
    Popescu, Alexandru
    Blekinge Institute of Technology, School of Computing.
    Pla, Vicent
    Popescu, Adrian
    Blekinge Institute of Technology, School of Computing.
    Cognitive Radio Networks with Elastic Traffic2012Conference paper (Refereed)
    Abstract [en]

    We model and evaluate an infrastructure based cognitive radio network where impatient unlicensed or secondary users (SUs) offer elastic traffic. The interference created by SUs to the licensed users is analyzed when the secondary network uses two different spectrum access schemes, the conventional random access scheme and a new scheme we refer to as access with preference. To further control the interference, a limit is set to the number of channels SUs have access to. With this new constraint, the abandonment probability, the mean delay and throughput of the SUs degrades significantly. To improve the QoS perceived by the active SUs, we define and evaluate an admission control scheme for the SUs.

  • 2.
    Popescu, Alexandru
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Cognitive Radio Networks: Elements and Architectures2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    As mobility and computing becomes ever more pervasive in society and business, the non-optimal use of radio resources has created many new challenges for telecommunication operators. Usage patterns of modern wireless handheld devices, such as smartphones and surfboards, have indicated that the signaling traffic generated is many times larger than at a traditional laptop. Furthermore, in spite of approaching theoretical limits by, e.g., the spectral efficiency improvements brought by 4G, this is still not sufficient for many practical applications demanded by end users. Essentially, users located at the edge of a cell cannot achieve the high data throughputs promised by 4G specifications. Worst yet, the Quality of Service bottlenecks in 4G networks are expected to become a major issue over the next years given the rapid growth of mobile devices. The main problems are because of rigid mobile systems architectures with limited possibilities to reconfigure terminals and base stations depending on spectrum availability. Consequently, new solutions must be developed that coexist with legacy infrastructures and more importantly improve upon them to enable flexibility in the modes of operation. To control the intelligence required for such modes of operation, cognitive radio technology is a key concept suggested to be part of the so-called beyond 4th generation mobile networks. The basic idea is to allow unlicensed users access to licensed spectrum, under the condition that the interference perceived by the licensed users is minimal. This can be achieved with the help of devices capable of accurately sensing the spectrum occupancy, learning about temporarily unused frequency bands and able to reconfigure their transmission parameters in such a way that the spectral opportunities can be effectively exploited. Accordingly, this indicates the need for a more flexible and dynamic allocation of the spectrum resources, which requires a new approach to cognitive radio network management. Subsequently, a novel architecture designed at the application layer is suggested to manage communication in cognitive radio networks. The goal is to improve the performance in a cognitive radio network by sensing, learning, optimization and adaptation.

  • 3.
    Popescu, Alexandru
    et al.
    Blekinge Institute of Technology, School of Computing.
    Fiedler, Markus
    Blekinge Institute of Technology, School of Computing.
    On Data Representation in Cognitive Radio Networks2012Conference paper (Refereed)
    Abstract [en]

    Dynamic Spectrum Access (DSA) and routing in Cognitive Radio Networks (CRNs) present challenging operational and technological problems in beyond 4G networks. Additionally, the provision of Quality of Experience (QoE) for different applications and Cognitive Radio Devices (CRDs) requires new management architectures and knowledge information approaches. The paper advances a new data-representation solution to allow efficient multi-constraint routing and multi dimensional adaptation for multiple cognitive radio (CR) dimensions like space, frequency, power and time. The goal of the paper is to advance a system for CRN data representation, which allows optimized communication according to QoE demands between Secondary Users (SUs).

  • 4.
    Popescu, Alexandru
    et al.
    Blekinge Institute of Technology, School of Computing.
    Fiedler, Markus
    Blekinge Institute of Technology, School of Computing.
    On Routing in Cognitive Radio Networks2012Conference paper (Refereed)
    Abstract [en]

    Abstract—Cognitive Radio Networks (CRNs) are expected toaddress and to resolve important technological and operational challenges of future networks, such as Dynamic Spectrum Access (DSA), routing in heterogeneous networks and provision of Quality of Experience (QoE) for different applications. Accordingly, a number of new terminal and network functionalities are required to solve the technical problems and to provide efficient management of CRNs. The paper advances a new solution for routing in CRNs, providing communication between Secondary Users (SUs) occupying different so-called Spectrum Opportunities (SOPs), i.e., portions of spectrum not occupied by Primary Users (PUs). This entails solving a complex process composed by two fundamental elements. These elements are multi-constraint routing and multi-dimensional adaptation for multiple cognitive radio dimensions like space, frequency, power and time. The goal of the paper is to develop optimization algorithms necessary to provide end-to-end (e2e) routing paths for communication between SUs with associated QoE demands.

  • 5.
    Popescu, Alexandru
    et al.
    Blekinge Institute of Technology, School of Computing.
    Fiedler, Markus
    Blekinge Institute of Technology, School of Computing.
    On Routing in Cognitive Radio Networks (extended version)2012In: MTA Review, ISSN 1843-3391, Vol. XXII, no 4, p. 197-212Article, review/survey (Refereed)
    Abstract [en]

    Cognitive Radio Networks are expected to resolve important technological and operational challenges of future networks, such as Dynamic Spectrum Access, routing in heterogeneous networks and provisioning of Quality of Experience for different applications. Accordingly, a number of new terminal and network functionalities are required to solve the technical problems and to provide efficient management. The paper advances a new solution for routing in Cognitive Radio Networks, providing communication between Secondary Users occupying different socalled Spectrum Opportunities, i.e., portions of spectrum not occupied by Primary Users. This entails solving a complex process composed by two fundamental elements. These are the multi-constraint routing and the multi-dimensional adaptation for multiple cognitive radio dimensions like space, frequency, power and time. The goal of the paper is to develop optimization algorithms necessary to provide end-to-end routing paths for communication between Secondary Users with associated Quality of Experience demands.

  • 6.
    Popescu, Alexandru
    et al.
    Blekinge Institute of Technology, School of Computing.
    Yao, Yong
    Blekinge Institute of Technology, School of Computing.
    Fiedler, Markus
    Blekinge Institute of Technology, School of Computing.
    On Mobility Generated Signaling in Cognitive Radio Network Clusters2013Conference paper (Refereed)
    Abstract [en]

    The rapid migration towards wireless connectivity means that the radio spectrum must be efficiently utilized to conserve capacity and to avoid overcrowding, particularly in densely populated areas. Towards this goal, cognitive radio technology is a key concept. The basic idea is to allow unlicensed users access to licensed spectrum, under the condition that the interference perceived by the licensed users is minimal. A novel architecture designed and developed at the application layer has been suggested by researchers at Blekinge Institute of Technology for the management of cognitive radio networks. Emphasizing on signaling facilities in this architecture and common control channel dimensioning aspects, the paper reports on simulation results regarding node mobility for a particular network model. To reduce the energy consumption of mobile devices, innovative signaling strategies are a very important topic to consider in novel mobile system architectures.

  • 7.
    Popescu, Alexandru
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Yao, Yong
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Fiedler, Markus
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popescu, Adrian
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    A Management Architecture for Multimedia Communication in Cognitive Radio Networks2015In: Multimedia over Cognitive Radio Networks: Algorithms, Protocols, and Experiments / [ed] Hu, F; Kumar, S, CRC Press, 2015, p. 3-31Chapter in book (Other academic)
  • 8.
    Popescu, Alexandru
    et al.
    Blekinge Institute of Technology, School of Computing.
    Yao, Yong
    Blekinge Institute of Technology, School of Computing.
    Fiedler, Markus
    Blekinge Institute of Technology, School of Computing.
    Popescu, Adrian
    Blekinge Institute of Technology, School of Computing.
    Communication Mechanisms for Cognitive Radio Networks2013Conference paper (Refereed)
    Abstract [en]

    Comprehensive communication in cognitive radio networks is an important research topic within the scope of empowering cognitive radio functionality in beyond-4G mobile networks. Providing communication for secondary users without interference with primary users is an ambitious task, which requires innovative management architecture designs and routing solutions. Operational challenges such as opportunistic spectrum access, solving problems related to spectrum and network heterogeneities and requests for the provisioning of Quality-of-Service to different applications must be resolved. As part of a novel management architecture, the paper advances a new approach to end-to-end communication in cognitive radio networks based on combining ad-hoc algorithms with spectrum mobility algorithms.

  • 9.
    Popescu, Alexandru
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Yao, Yong
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Fiedler, Markus
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popescu, Adrian
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Network Architecture to Support Multimedia over CRN2014In: Multimedia over Cognitive Radio Networks: Algorithms, Protocols, and Experiments / [ed] Hu, Fei; Kumar, Sunil, CRC Press , 2014Chapter in book (Refereed)
  • 10.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, School of Computing.
    Popescu, Alexandru
    Blekinge Institute of Technology, School of Computing.
    Ngoga, Said Rubatayiro
    Blekinge Institute of Technology, School of Computing.
    Popescu, Adrian
    Blekinge Institute of Technology, School of Computing.
    On Prioritized Spectrum Access in Cognitive Radio Networks with Imperfect Sensing2013Conference paper (Refereed)
    Abstract [en]

    Cognitive Radio networks allow the unlicensed users to share the available spectrum opportunities. However, this demands for solving the problem of contention among multiple unlicensed user packets for transmission. In our paper, we consider the Opportunistic Spectrum Access model for packet transmission between two unlicensed users. We suggest a priority scheme for a unlicensed user to concurrently transmit different types of packets. Our scheme reserves a fixed number of queueing places in the buffer for the prioritized packets. We study the transmission performance under both the priority scheme and imperfect spectrum sensing, with respect to the blocking probabilities, average transmission delay and transmission throughput of unlicensed users packets. The Markov chain based numerical analysis is validated by simulation experiments. Our results show that the suggested priority scheme is able to enhance transmission throughput of unlicensed users packets, together with significant decreased average transmission delay and minor decreased total transmission throughput.

  • 11.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popescu, Alexandru
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popescu, Adrian
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    On Fuzzy Logic-Based Channel Selection in Cognitive Radio Networks2014In: Software-Defined and Cognitive Radio Technologies for Dynamic Spectrum Management / [ed] Kaabouch, Naima; Hu, Wen-Chen, Hershey, PA 17033, USA: IGI-Global , 2014Chapter in book (Refereed)
    Abstract [en]

    Cognitive radio networks are a new technology based on which unlicensed users are allowed access to licensed spectrum under the condition that the interference perceived by licensed users is minimal. That means unlicensed users need to learn from environmental changes and to take appropriate decisions regarding the access to the radio channel. This is a process that can be done by unlicensed users in a cooperative or non-cooperative way. Whereas the non-cooperative algorithms are risky with regard to performance, the cooperative algorithms have the capability to provide better performance. Our paper reports therefore a new fuzzy logic based decision making algorithm for channel selection. The underlying decision criterion considers statistics of licensed users channel occupancy as well as information about the competition level of unlicensed users. Our theoretical studies indicate that the unlicensed users can obtain an efficient sharing of the available channels. Simulation results are reported to demonstrate the performance and effectiveness of the suggested algorithm.

  • 12.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popescu, Alexandru
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popescu, Adrian
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    On prioritised opportunistic spectrum access in cognitive radio cellular networks2015In: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 27, no 2, p. 294-310Article in journal (Refereed)
    Abstract [en]

    Cognitive radio (CR) networks allow secondary users (SUs) to opportunistically access licensed spectrum, thus providing efficient use of radio resources. Different studies carried out on CR networks have focused on the procedure of spectrum handoff of SUs such as the data transmission in a communication that can be carried out in different channels. In this paper, we consider cellular networks enhanced with facilities for CR communication where a user with a call in progress moves across neighbouring cells, that is, the so-called inter-cell handoff. Our model assumes that the cell gives priority to inter-cell handoff calls over the calls originating within it. A finite queue is used in every cell for SUs, and a fixed number of buffer slots are reserved for the inter-handoff SU calls. With these considerations, we study the transmission performance of SUs by using Markov chains-based modelling approach. The numerical analysis is validated by simulation experiments. We also suggest a fuzzy logic-based hybrid decision-making algorithm to select the best solution for inter-handoff prioritisation. The goal is to optimise the transmission performance of SUs by leveraging their requirements on service completion throughput and waiting time in each cell. Copyright © 2014 John Wiley & Sons, Ltd.

1 - 12 of 12
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