103 research outputs found

    Per-Flow Radio Resource Management to Mitigate Interference in Dense IEEE 802.11 Wireless LANs

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    Current interference management solutions for dense IEEE 802.11 Wireless Local Area Networks (WLANs) rely on locally measuring the cumulative interference at the Acess Point (AP) in charge of adjusting the spectrum resources to its clients. These solutions often result in coarse-grained spectrum allocation that often leaves many wireless users unsatisfied and increases the spectrum congestion problem instead of easing it. In this paper we present a centralised interference management algorithm that treats the network-wide interference impact of each channel individually and allows the controller to adjust the radio resource of each AP while it is utilised. This coordinated allocation takes into account the Quality of Service (QoS) requirements of downlink flows while minimising its effect on neighbouring APs. Therefore, this paper proposes a novel approach for quantifying the interference impact of each employed channel and jointly addressing the user-side quality requirements and the network-side interference management. The algorithm is tailored for operator-agnostic Software-Defined Networking (SDN)-based Radio Resource Management (RRM) in dense Wireless Fidelity (Wi-Fi) networks and adopts a fine-grained per-flow approach. Simulation results show that our algorithm outperforms existing solutions in terms of reducing the overall interference, increasing the capacity of the wireless channel and improving the users’ satisfaction

    Final Specification of Cooperative Functionalities

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    This deliverable presents the specification of the final version of the Cooperative AP Functionalities that have been designed in the context of Work Package (WP) 4 of the Wi-5 project. In detail, we present a general cooperative framework that includes functionalities for a Radio Resource Management (RRM) algorithm, which provides channel assignment and transmit power adjustment strategies, an AP selection policy, which also provides horizontal handover, and a Radio Access Technology (RAT) selection solution for vertical handover. The RRM algorithm achieves an important improvement for network performance in terms of several parameters through the channel assignment approach and the transmit power adjustment. The AP selection solution extends the approach presented in deliverables D4.1 and D4.2 and is based on a centralised potential game, which optimises the distribution of the so-called Fittingness Factor (FF) parameter among the Wi-Fi users. Such a parameter efficiently matches the suitability of the available spectrum resource to the users’ application requirements. Moreover, the RAT selection solution extends the AP selection algorithm towards vertical handover functionality including 3G/4G networks. The assessment of the newest algorithms developed in the context of WP4 is illustrated in this deliverable through the analysis of several performance results in a simulated environment against other strategies found in the literature. Finally, the set of smart AP functionalities developed in the context of WP3, implemented on the Wi5 APs and on the Wi-5 controller, and their use in the proposed algorithms are illustrated. Specifically, this deliverable describes how these functionalities can enable the correct deployment of the proposed cooperative AP solutions in realistic scenarios. Therefore, the main novel contributions of this deliverable are i) the strengthening of the AP selection algorithm, ii) the design and assessment of a new algorithm for vertical handover and iii) the presentation of the finalised integration of the cooperative AP functionalities of the Wi-5 system

    Spectrum and power optimization for wireless multiple access networks.

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    Emerging high-density wireless networks in urban area and enterprises offer great potential to accommodate the anticipated explosion of demand for wireless data services. To make it successful, it is critical to ensure the efficient utilisation of limited radio resources while satisfying predefined quality of service. The objective of this dissertation is to investigate the spectrum and power optimisation problem for densely deployed access points (APs) and demonstrate the potential to improve network performance in terms of throughput and interference. Searching the optimal channel assignment with minimum interference is known as an AfV-haxd problem. The increased density of APs in contrary to the limited usable frequencies has aggravated the difficulty of the problem. We adopt heuristic based algorithms to tackle both centralised and distributed dynamic channel allo cation (DCA) problem. Based on a comparison between Genetic Algorithm and Simulated Annealing, a hybrid form that combines the two algorithms achieves good trade-off between fast convergence speed and near optimality in centralised scenario. For distributed DCA, a Simulated Annealing based algorithm demon strates its superiority in terms of good scalability and close approximation to the exact optimal solution with low algorithm complexity. The high complexity of interactions between transmit power control (TPC) and DCA renders analytical solutions to the joint optimisation problems intractable. A detailed convergence analysis revealed that optimal channel assignment can strengthen the stability condition of TPC. Three distributed algorithms are pro posed to interactively perform the DCA and TPC in a real time and open ended manner, with the ability to appropriately adjust power and channel configurations according to the network dynamics. A real network with practical measurements is employed to quantify and verify the theoretical throughput gain of their inte gration. It shows that the integrated design leads to a substantial throughput improvement and power saving compared with conventional fixed-power random channel allocation system

    Specification of Cooperative Access Points Functionalities version 2

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    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. This deliverable presents the specification of the second version of the Cooperative AP Functionalities that are being designed in the context of Work Package (WP) 4 of the Wi-5 project. Specifically, we present a general cooperative framework that includes functionalities for a Radio Resource Management (RRM) algorithm, which provides channel assignment and transmit power adjustment strategies, an AP selection policy, and a solution for vertical handover. The RRM achieves an important improvement for network performance in terms of several parameters through the channel assignment approach, that can be further improved by including the transmit power adjustment. The AP selection solution extends the approach presented in deliverable D4.1 based on the Fittingness Factor (FF) concept, which is a parameter for efficiently matching the suitability of the available spectrum resource to the application requirements. Moreover, the preliminary details, which will allow us to extend AP selection towards vertical handover functionality including 3G/4G networks, are also presented. The assessment of the algorithms proposed in this deliverable is illustrated through the analysis of several performance results in a simulated environment against other strategies found in the literature. Finally, a set of monitoring capabilities implemented on the Wi-5 APs and on the Wi-5 controller are illustrated. These capabilities will enable the correct deployment of the cooperative APs functionalities proposed in this deliverable in realistic scenarios

    Self management of high density wireless networks

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    IEEE 802.11 wireless networks are very popular in today’s world. This popularity has been stimulated due to the use of mobile computing devices such as laptops, tablets, and Wi-Fi enabled phones. We can get 802.11 connectivity in schools, squares, parks and other public places. All of these places can have a high concentration of users. Moreover, there are other nonpublic places like lecture halls, hotel ballrooms, and convention centers that are common examples of spaces with high concentration of users in a high-density wireless communications environment. Dense deployments of wireless networks suffer from increased interference and, as a result, bad user experience. The interference caused by the co-channel and adjacent channel interference driven by co-located devices is one of the main issues to address to improve network performance. The limited number of nonoverlapping channels may lead to severe interference scenarios if no appropriated spectrum planning is employed. In this work, we present an in-depth review of research work for the channel allocation strategies. Then, we formalize the channel allocation as a minimization problem of the interference level and we propose three different manners to optimize channel assignment between participating Access Points with the aim to improve network performance. The algorithms that we propose can be classified as local and uncoordinated, coordinated and distributed, and centralized. The local and uncoordinated solution behaves well in our testbed but present oscillatory issues that we tackle with a feedback control technique. Finally, this work presents an evaluation of the strategies, on a testbed and on a simulation environment. In the testbed we demonstrate the practical deployability of the solutions and lead to the conclusion that the local and uncoordinated implementation is worthy to be considered as a good strategy for the channels allocation problem where Access Points works in isolated manner. In the simulation, we test the scalability of both, the coordinated and centralized solution, and we show that they can be deployed in networks with more than thirty Access Points and as a results, we conclude that the centralized implementation is the best strategy to perform optimization decisions for channel allocation in connected networks.Las redes inalámbricas IEEE 802.11 son muy populares en el mundo actual. Esta popularidad ha sido estimulada debido al uso de dispositivos móviles tales como laptops, tablets y teléfonos Wi-Fi compatibles. Se puede tener conectividad 802.11 en escuelas, plazas, parques y otros lugares públicos. Todos estos lugares pueden tener una gran concentración de usuarios. Más aún, hay otros lugares no públicos como las bibliotecas, centros de convenciones, salas de conferencias en hoteles, los cuales también son ejemplo de espacios comunes con una gran concentración de usuarios en entornos de comunicación inalámbrica de alta densidad. Instalaciones de redes cámbricas densas experimentan una interferencia creciente, y como resultado, una mala experiencia de usuario. Las interferencias co-canal y de canal adyacente producidas por dispositivos próximos entre sí, son uno de los principales problemas a abordar para mejorar la performance de la red. El número limitado de canales que no se superponen pueden conducir a escenarios de severa interferencia si no se emplea una planificaci´on apropiada del espectro. En este trabajo, se presenta una revisi´on profunda de los trabajos de investigación para estrategias de asignaci´on de canales. Luego, se formaliza la asignación de canales como un problema de minimización del nivel de interferencia y se proponen tres diferentes maneras para optimizar la asignación de canales entre los Puntos de Acceso participantes con el objetivo de mejorar la performance de la red. Los algoritmos propuestos pueden clasificarse como local y no-coordinado, coordinado y distribuido, y centralizado. La solución local y no- coordinada se comparta de manera aceptable en el prototipo pero presenta problemas de oscilación que se aborda con una técnica de control por retro alimentación. Finalmente, este trabajo presenta una evaluación de las estrategias, en un prototipo y en un entorno de simulación. En el prototipo se demuestra el despliegue práctico de las soluciones y se llega a la conclusi´on que la implementación local y no-coordinada es digna de ser considerada como una buena estrategia para el problema de asignación de canales cuando los Puntos de Acceso trabajan en forma aislada. En la simulación, se prueban la escalabilidad de las soluciones coordinada y centralizada, y se muestra que pueden ser desplegadas en redes con más de treinta Puntos de Acceso y como resultado, se concluye que la implementación centralizada es la mejor estrategia para realizar decisiones de optimizaci´on para la asignaci´on de canales en redes conectadas

    Optimizing multiuser MIMO for access point cooperation in dense wireless networks

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    As the usage of wireless devices continues to grow rapidly in popularity, wireless networks that were once designed to support a few laptops must now host a much wider range of equipments, including smart phones, tablets, and wearable devices, that often run bandwidth-hungry applications. Improvements in wireless local access network (WLAN) technology are expected to help accommodate the huge traffic demands. In particular, advanced multicell Multiple-Input Multiple-Output (MIMO) techniques, involving the cooperation of APs and multiuser MIMO processing techniques, can be used to satisfy the increasing demands from users in high-density environments. The objective of this thesis is to address the fundamental problems for multiuser MIMO with AP cooperation in dense wireless network settings. First, for a very common multiuser MIMO linear precoding technique, block diagonalization, a novel pairing-and-binary-tree based user selection algorithm is proposed. Second, without the zero-forcing constraint on the multiuser MIMO transmission, a general weighted sum rate maximization problem is formulated for coordinated APs. A scalable algorithm that performs a combined optimization procedure is proposed to determine the user selection and MIMO weights. Third, we study the fair and high-throughput scheduling problem by formally specifying an optimization problem. Two algorithms are proposed to solve the problem using either alternating optimization or a two-stage procedure. Fourth, with the coexistence of both stationary and mobile users, different scheduling strategies are suggested for different user types. The provided theoretical analysis and simulation results in this thesis lay out the foundation for the realization of the clustered WLAN networks with AP cooperation.Ph.D

    Specification of Smart AP solutions - version 2

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    This document includes the specification of the second version of the Smart Access Point (AP) Solutions, which are being developed within WP3 of the Wi-5 project. After the Literature Review, a global view of the Wi-5 architecture is presented which includes not only the Smart AP Solutions but also the Cooperative Functionalities being developed in WP4. Next, the Smart AP Solutions are described including the summary of the general approach being followed based on Light Virtual APs (LVAPs). The functionalities enabling Radio Resource Management (i.e. Dynamic Channel Allocation, Load Balancing and Power Control) are reported in detail and the current status of the implementation of the solutions is detailed, with a set of improvements aimed at integrating the support of different channels within the Wi-5 framework. A multi-channel handoff scheme has been designed, requiring a good synchronisation between the different events, in order to make the LVAP switching happen at the same moment when the STA switches its channel. In addition, the beacon generation has been modified in order to improve the scalability and to give a better user experience during handoffs. Tests measuring the handoff delay are presented using three wireless cards from different manufacturers, and using as test traffic a flow of an online game with real-time constraints. The results show that fast handovers ranging from 30 to 200 milliseconds can be achieved. The savings provided by frame aggregation, and its effect on subjective quality have also been studied. A methodology including subjective tests with real users has evaluated this effect, using paired comparison. The results indicate that bandwidth usage savings and especially significant packet rate reduction can be obtained without degrading players’ Quality of Experience (QoE), as long as the overall latency is kept under 100ms. An important finding coming from these results is that the players do not register delay variation introduced by multiplexing

    Efficient radio resource management for future generation heterogeneous wireless networks

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    The heterogeneous deployment of small cells (e.g., femtocells) in the coverage area of the traditional macrocells is a cost-efficient solution to provide network capacity, indoor coverage and green communications towards sustainable environments in the future fifth generation (5G) wireless networks. However, the unplanned and ultra-dense deployment of femtocells with their uncoordinated operations will result in technical challenges such as severe interference, a significant increase in total energy consumption, unfairness in radio resource sharing and inadequate quality of service provisioning. Therefore, there is a need to develop efficient radio resource management algorithms that will address the above-mentioned technical challenges. The aim of this thesis is to develop and evaluate new efficient radio resource management algorithms that will be implemented in cognitive radio enabled femtocells to guarantee the economical sustainability of broadband wireless communications and users' quality of service in terms of throughput and fairness. Cognitive Radio (CR) technology with the Dynamic Spectrum Access (DSA) and stochastic process are the key technologies utilized in this research to increase the spectrum efficiency and energy efficiency at limited interference. This thesis essentially investigates three research issues relating to the efficient radio resource management: Firstly, a self-organizing radio resource management algorithm for radio resource allocation and interference management is proposed. The algorithm considers the effect of imperfect spectrum sensing in detecting the available transmission opportunities to maximize the throughput of femtocell users while keeping interference below pre-determined thresholds and ensuring fairness in radio resource sharing among users. Secondly, the effect of maximizing the energy efficiency and the spectrum efficiency individually on radio resource management is investigated. Then, an energy-efficient radio resource management algorithm and a spectrum-efficient radio resource management algorithm are proposed for green communication, to improve the probabilities of spectrum access and further increase the network capacity for sustainable environments. Also, a joint maximization of the energy efficiency and spectrum efficiency of the overall networks is considered since joint optimization of energy efficiency and spectrum efficiency is one of the goals of 5G wireless networks. Unfortunately, maximizing the energy efficiency results in low performance of the spectrum efficiency and vice versa. Therefore, there is an investigation on how to balance the trade-off that arises when maximizing both the energy efficiency and the spectrum efficiency simultaneously. Hence, a joint energy efficiency and spectrum efficiency trade-off algorithm is proposed for radio resource allocation in ultra-dense heterogeneous networks based on orthogonal frequency division multiple access. Lastly, a joint radio resource allocation with adaptive modulation and coding scheme is proposed to minimize the total transmit power across femtocells by considering the location and the service requirements of each user in the network. The performance of the proposed algorithms is evaluated by simulation and numerical analysis to demonstrate the impact of ultra-dense deployment of femtocells on the macrocell networks. The results show that the proposed algorithms offer improved performance in terms of throughput, fairness, power control, spectrum efficiency and energy efficiency. Also, the proposed algorithms display excellent performance in dynamic wireless environments
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