Traffic Control and Quality of Service in Wireless LANs

The thesis deals with two aspects of the IEEE 802.11 standard. The first is the so-called “performance anomaly”: the variable bandwidth of the links and the use of multiple transmission rates push the throughput of all stations to align to the slowest one. To tackle this problem we designed and developed a simple channel-aware scheduling algorithm, called DTT, which actualises the proportional fairness concept, thus leading to noteworthy improvements, and in particular to flow isolation. This is achieved by measuring link quality as the time needed to deliver a frame. The resource to share is no longer capacity, but the time the channel is in use. DTT has then been integrated into a prototype Access Point, which is the first working implementation of a scheduler based on proportional fairness. Secondly, we focused on 802.11e networks, which, though enhancing QoS support, still offer scarce reliability of QoS guarantees and suffer from network congestion. We devised two admission control algorithms to assess the maximum number of users allowable to the services while satisfying QoS requirements. Following the studies on DTT, both algorithms centre the admission test on the time occupancy of the medium. The first algorithm builds on an analytical model of the EDCA mode in non-saturation conditions. This closely matches the real behaviour of a network carrying time-sensitive applications, thus overcoming the limits of all previous works, based on saturation models. The second algorithm uses and extends to 802.11e the NUC, a parameter defined and proved effective for 802.11b systems. This scheme needs measures of the actual state of the network. Simulations run within the E-model framework show good accuracy performance for both models

A Novel Voice Priority Queue (VPQ) Schedule and Algorithm for VoIP over WLAN Network

The VoIP deployment on Wireless Local Area Networks (WLANs), which is based on IEEE 802.11 standards, is increasing. Currently, many schedulers have been introduced such as Weighted Fair Queueing (WFQ), Strict Priority (SP) General processor sharing (GPS), Deficit Round Robin (DRR), and Contention-Aware Temporally fair Scheduling (CATS). Unfortunately, the current scheduling techniques have some drawbacks on real-time applications and therefore will not be able to handle the VoIP packets in a proper way. The objective of this research is to propose a new scheduler system model for the VoIP application named final stage of Voice Priority Queue (VPQ) scheduler. The scheduler system model is to ensure efficiency by producing a higher throughput and fairness for VoIP packets. In this paper, only the final Stage of the VPQ packet scheduler and its algorithm are presented. Simulation topologies for VoIP traffic were implemented and analyzed using the Network Simulator (NS-2). The results show that this method can achieve a better and more accurate VoIP quality throughput and fairness index over WLANs

A novel Voice Priority Queue (VPQ) scheduler and algorithm for VOIP over WLAN network

The VoIP deployment on Wireless Local Area Networks (WLANs), which is based on IEEE 802.11 standards, is increasing.Currently, many schedulers have been introduced such as Weighted Fair Queueing (WFQ), Strict Priority (SP) General processor sharing (GPS), Deficit Round Robin (DRR), and Contention-Aware Temporally fair Scheduling(CATS).Unfortunately, the current scheduling techniques have some drawbacks on real-time applications and therefore will not be able to handle the VoIP packets in a proper way.The objective of this research is to propose a new scheduler system model for the VoIP application named final stage of Voice Priority Queue (VPQ) scheduler.The scheduler system model is to ensure efficiency by producing a higher throughput and fairness for VoIP packets.In this paper, only the final Stage of the VPQ packet scheduler and its algorithm are presented.Simulation topologies for VoIP traffic were implemented and analyzed using the Network Simulator (NS-2).The results show that this method can achieve a better and more accurate VoIP quality throughput and fairness index over WLANs

A VOICE PRIORITY QUEUE (VPQ) SCHEDULER FOR VOIP OVER WLANs

The Voice over Internet Protocol (VoIP) application has observed the fastest growth in the world of telecommunication. The Wireless Local Area Network (WLAN) is the most assuring of technologies among the wireless networks, which has facilitated high-rate voice services at low cost and good flexibility. In a voice conversation, each client works as a sender and as a receiver depending on the direction of traffic flow over the network. A VoIP application requires a higher throughput, less packet loss and a higher fairness index over the network. The packets of VoIP streaming may experience drops because of the competition among the different kinds of traffic flow over the network. A VoIP application is also sensitive to delay and requires the voice packets to arrive on time from the sender to the receiver side without any delay over WLANs. The scheduling system model for VoIP traffic is still an unresolved problem. A new traffic scheduler is necessary to offer higher throughput and a higher fairness index for a VoIP application. The objectives of this thesis are to propose a new scheduler and algorithms that support the VoIP application and to evaluate, validate and verify the newly proposed scheduler and algorithms with the existing scheduling algorithms over WLANs through simulation and experimental environment. We proposed a new Voice Priority Queue (VPQ) scheduling system model and algorithms to solve scheduling issues. VPQ system model is implemented in three stages. The first stage of the model is to ensure efficiency by producing a higher throughput and fairness for VoIP packets. The second stage will be designed for bursty Virtual-VoIP Flow (Virtual-VF) while the third stage is a Switch Movement (SM) technique. Furthermore, we compared the VPQ scheduler with other well known schedulers and algorithms. We observed in our simulation and experimental environment that the VPQ provides better results for the VoIP over WLANs

Slicing in WiFi networks through airtime-based resource allocation

Network slicing is one of the key enabling technologies for 5G networks. It allows infrastructure owners to assign resources to service providers (tenants), which will afterwards use them to satisfy their end-user demands. This paradigm, which changes the way networks have been traditionally managed, was initially proposed in the wired realm (core networks). More recently, the scientific community has paid attention to the integration of network slicing in wireless cellular technologies (LTE). However, there are not many works addressing the challenges that appear when trying to exploit slicing techniques over WiFi networks, in spite of their growing relevance. In this paper we propose a novel method of proportionally distributing resources in WiFi networks, by means of the airtime. We develop an analytical model, which shed light on how such resources could be split. The validity of the proposed model is assessed by means of simulation-based evaluation over the ns-3 framework.This work has been supported in part by the European Commission and the Spanish Government (Fondo Europeo de desarrollo Regional, FEDER) by means of the EU H2020 NECOS (777067) and ADVICE (TEC2015-71329) projects, respectively

Providing air-time usage fairness in IEEE 802.11 networks with the deficit transmission time (DTT) scheduler

Wireless systems based on the IEEE 802.11 standard are known to suffer a performance degradation when just a single station in the network experiences bad channel conditions toward the Access Point (AP). This phenomenon, known as the "performance anomaly", is mainly due to the max-min throughput fairness of the CSMA/CA algorithm of the 802.11 MAC. The simple FIFO scheduling policy usually implemented in the AP also contributes to this problem. In order to overcome the performance anomaly, we propose the Deficit Transmission Time (DTT) scheduler. The aim of DTT is guaranteeing each station a fair medium usage in terms of transmission time. This feature, directly related to the proportional fairness concept, allows to ideally achieve exact isolation among the traffic flows addressed to different stations. DTT achieves this goal taking advantage of measurements of actual frame transmission times. Experiments carried out using a prototype implementation of DTT are compared with analogous tests performed with a classic FIFO queue of a commercial AP and a recently proposed traffic shaping scheme aimed at solving the same 802.11 performance anomaly

Proceedings of the 7th International Conference EEDAL 2013 Energy Efficiency in Domestic Appliances and Lighting

This book contains the papers presented at the seventh international conference on Energy Efficiency in Domestic Appliances and Lighting. EEDAL'2013 was organised in Coimbra, Portugal in September 2013. This major international conference, which was previously been staged in Florence 1997, Naples 2000, Turin 2003, London 2006, B2e0r0l9in, Copenhagen 2011 has been very successful in attracting an international community of stakeholders dealing with residential appliances, equipment, metering liagnhdti ng (including manufacturers, retailers, consumers, governments, international organisations aangde ncies, academia and experts) to discuss the progress achieved in technologies, behavioural aspects and poliacineds , the strategies that need to be implemented to further progress this important work. Potential readers who may benefit from this book include researchers, engineers, policymakers, and all those who can influence the design, selection, application, and operation of electrical appliances and lighting.JRC.F.7-Renewables and Energy Efficienc

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen