A Belief-Based Decision-Making Framework for Spectrum Selection in Cognitive Radio Networks

This paper presents a comprehensive cognitive management framework for spectrum selection in cognitive radio (CR) networks. The framework uses a belief vector concept as a means to predict the interference affecting the different spectrum blocks (SBs) and relies on a smart analysis of the scenario dynamicity to properly determine an adequate observation strategy to balance the tradeoff between achievable performance and measurement requirements. In this respect, the paper shows that the interference dynamics in a given SB can be properly characterized through the second highest eigenvalue of the interference state transition matrix. Therefore, this indicator is retained in the proposed framework as a relevant parameter to drive the selection of both the observation strategy and spectrum selection decision-making criterion. This paper evaluates the proposed framework to illustrate the capability to properly choose among a set of possible observation strategies under different scenario conditions. Furthermore, a comparison against other state-of-the-art solutions is presented

On Demonstrating Spectrum Selection Functionality for Opportunistic Networks

This paper presents a testbed platform to demonstrate and validate spectrum opportunity identification and spectrum selection functionalities in Opportunistic Networks (ONs). The hardware component of the testbed is based on reconfigurable devices able to transmit and receive data at different operating frequencies, which are dynamically configured. The software component has been developed to perform the creation and maintenance of ON radio links, including spectrum opportunity identification and selection decision making as well as all the necessary signaling to support the ON operation. Therefore, the presented platform provides a powerful tool for testing different algorithms in real operational radio environments under various interference conditions, thus enabling to gain deeper insight into the performance of algorithmic solutions, beyond the purely theoretical analyses based on models and/or simulations. Results presented in the paper validate the implementation conducted at the laboratory and illustrate the reconfigurability capabilities of the ON links under different conditions

Specification of Cooperative Access Points Functionalities version 1

The What to do With the Wi-Fi Wild West H2020 project (Wi-5) combines research and innovation to propose an architecture based on an integrated and coordinated set of smart Wi-Fi networking solutions. The resulting system will be able to efficiently reduce interference between neighbouring Access Points (APs) and provide optimised connectivity for new and emerging services. The project approach is expected to develop and incorporate a variety of different solutions, which will be made available through academic publications, in addition to other dissemination channels. The present document includes the specification of the first version of the Cooperative AP Functionalities, which are being defined within Work Package (WP) 4 of the Wi-5 project. In this deliverable after the Executive Summary and the literature review, the first version of the Cooperative Access Point Solutions are illustrated. In particular, a section with a general cooperative framework that jointly includes functionalities for an optimized AP channel assignment, Radio Resource Management (RRM) and smart AP allocation is presented. The optimized APs channel assignment enables an important improvement of the network performance in terms of SINR. Furthermore, the results analysed in this deliverable validate the flexibility and practicality of the proposed algorithm in different scenarios. The smart AP allocation solution introduces the innovative Fittingness Factor (FF) concept that efficiently matches the suitability of the available spectrum resource to the application requirements. Moreover, the basis required for a seamless mobility functionality in the framework is also included in the section. Next, a first assessment of the algorithms proposed in this deliverable is presented through the analysis of several performance results in a simulated environment. In detail, the AP channel assignment and the smart AP allocation algorithms are assessed and compared against other strategies found in the literature. Finally, a set of monitoring procedures to be conducted on the Wi-5 APs and on the Wi-5 controller are presented. These procedures will allow the correct deployment of the cooperative APs functionalities proposed in this deliverable. After summarising the main conclusions, the document ends with future work

Quality of Service Oriented Access Point Selection Framework for Large Wi-Fi Networks

This paper addresses the problem of Access Point (AP) selection in large Wi-Fi networks. Unlike current solutions that rely on Received Signal Strength (RSS) to determine the best AP that could serve a wireless user’s request, we propose a novel framework that considers the Quality of Service (QoS) requirements of the user’s data flow. The proposed framework relies on a function reflecting the suitability of a Wi-Fi AP to satisfy the QoS requirements of the data flow. The framework takes advantage of the flexibility and centralised nature of Software Defined Networking (SDN). A performance comparison of this algorithm developed through an SDN-based simulator shows significant achievements against other state of the art solutions in terms of provided QoS and improved wireless network capacity

Evaluation results

The H2020 What to do With the Wi-Fi Wild West (Wi-5) project combines research and innovation to propose a Software Defined Networking (SDN) architecture based on an integrated and coordinated set of smart Wi-Fi networking solutions. The resulting system will be able to efficiently reduce interference between neighboring Access Points (APs) and provide optimized connectivity for new and emerging services. In this document we present a general overview of the testing and field trials work and then describe the setup of the system in PrimeTel and the planning and description of the different tests and trials that were carried out in the SOHO and community Wi-Fi scenarios. We also provide a thorough explanation of the testing process and the important observations and results from the field trials conducted, including some conclusions about each test and application that was included during the field trials. In the final section we give a general assessment to the currently implemented Wi-5 applications regarding their functionality and performance. We also refer to the aspects of the system and functionalities of the system, in which, we believe that future work should aim at improving. Finally, we give a general recap of the problems and difficulties faced in the trials in an attempt to guide future work

A Centralized Framework for Smart Access Point Selection based on the Fittingness Factor

Abstract: This paper focuses on addressing the Access Point (AP) selection problem by relying on a centralized controller that provides a global view of the network. This approach follows the Software-Defined Networking (SDN) concept, which has long been considered in the literature as an innovative method to control management functionalities for wired networks and that is also now becoming a hot topic in the context of Wi-Fi networks. The proposed AP selection approach is based on a novel algorithm which relies on the Fittingness Factor (FF) concept, to maximize a function that reflects the suitability of the available spectrum resources to the application requirements. Specifically, this paper describes the development of a framework that implements the FF-based algorithm for smart AP selection in a centralized controller. The simulated performance comparison of this algorithm against a strategy that maximizes the achievable data rate considered in many papers in the literature, illustrates the important achievements that have been obtained in terms of saved bandwidth and users' satisfaction

SDN-Based Channel Assignment Algorithm for Interference Management in Dense Wi-Fi Networks

The popularity of Wi-Fi-enabled devices alongside the growing demand for non-licensed spectrum, has made the Wi-Fi networks exceedingly congested. This endangers the efficiency of Wi-Fi and negatively affect the users' experience. The problem is especially pressing in dense areas (e.g. shopping centers) where Wi-Fi channel assignment is more likely to be uncoordinated and the working environment of Wi-Fi Access Points (APs) has become increasingly time-variant. As a result, the availability of Software-Defined Networking (SDN) and network virtualization technologies has motivated the use of centralized resource management as a solution. This paper provides an algorithm for channel assignment functionality in the context of SDN-based centralized resource management, which captures the live status of a Wi-Fi network and is capable of optimising the Radio Frequency (RF) channel assignment process. The APs' network arrangement, the current assignment of the channels and the characteristics of the RF channels in IEEE 802.11 have all been taken into account in the proposed model. The performance of the proposed model in terms of the level of the interference, the spectral efficiency at each AP and the Signal to Interference plus Noise Ratio (SINR) at the user-side is evaluated through simulation and compared against state of the art solutions

Fine-Grained Radio Resource Management to Control Interference in Dense Wi-Fi Networks

In spite of the enormous popularity of Wi-Fienabled devices, the utilization of Wi-Fi radio resources (e.g. RF spectrum and transmission power levels) at Access Points (APs) is degraded in current decentralized Radio Resource Management (RRM) schemes. Most state of the art central control solutions apply configurations in which the network-wide impacts of the involved parameters and their mutual relationships are ignored. In this paper, we propose an algorithm for jointly adjusting the transmission power levels and optimizing the RF channel assignment of APs by taking into account the flows’ required qualities while minimizing their interference impacts throughout the network. The proposed solution is tailored for an operatoragnostic and Software Defined Wireless Networking (SDWN)- based centralised RRM in dense Wi-Fi networks. Our extensive simulation results validate the performance improvement of the proposed algorithm compared to the main state of the art alternative by showing more than 25% higher spectrum efficiency, satisfying the users’ demands and further mitigating the networkwide interference through a flow-based and quality-oriented power level adjustment

Testbed Description and Definition of the Tests

The H2020 What to do With the Wi-Fi Wild West (Wi-5) project combines research and innovation to propose a Software Defined Networking (SDN) architecture based on an integrated and coordinated set of smart Wi-Fi networking solutions. The resulting system will be able to efficiently reduce interference between neighbouring Access Points (APs) and provide optimised connectivity for new and emerging services. The project approach is expected to develop and incorporate a variety of different solutions, which will be made available through academic publications, in addition to other dissemination channels. In this document, we will present a description of the testbed to be used in the project and provide a definition of the tests to be done. First, the smart and cooperative solutions provided by the SDN based Wi-5 architecture will be briefly described. Next, we will define and explain the modular approach to be taken to model Wi-5 APs and the Wi-5 controller. According to this approach, we will describe the functionalities of both the Wi-5 AP that is modelled as a combination of the monitoring and network configuration modules, and the Wi-5 controller which is composed of the monitoring, decision, and network configuration modules. Then, we will define and explain the Wi5 integration strategy that will be utilized to integrate the smart and the cooperative functionalities in terms of assembly of the modules utilized to model the Wi-5 AP and the Wi-5 controller. Moreover, we will provide the definition of the performance metrics that will be utilized to evaluate and validate the performance of the monitoring, decision and network configuration modules with the use cases and performance requirements developed in Wi-5. This deliverable will focus on the definition and the explanation of the following two issues: Integration of the smart and cooperative functionalities provided by the SDN based Wi-5 architecture. Testing strategy to evaluate the performance of the Wi-5 architecture considering the use cases and requirements that focus on the selected scenarios

Lack of correlation between N-myc and MAX expression in neuroblastoma tumors and in cell lines: implication for N-myc-MAX complex formation

Detectable levels of MAX messenger RNA were found in a set of human neuroblastoma tumors and established cell lines. MAX mRNA levels were independent of tumor stage and N-myc genomic amplification. By contrast, N-myc mRNA transcripts were detectable only in tumors with amplification of N-myc gene and in cell lines. Analysis by reverse transcriptase polymerase chain reaction and hybridization to specific oligodeoxynucleotide probes revealed approximately equal amounts of two MAX transcripts in all cases analyzed. Immunoprecipitations with a specific antibody to MAX detected two proteins of M(r) 21,000 and 22,000 in approximately equal amounts in all neuroblastoma lines regardless of N-myc amplification and/or expression. On the other hand, protein binding to the myc DNA consensus sequence correlated with N-myc expression in neuroblastoma cells. Thus, N-myc expression might be a limiting factor in the formation of the N-myc-MAX heterodimer in neuroblastomas