27 research outputs found
Bidirectional LiFi Attocell Access Point Slicing Scheme
LiFi attocell access networks will be deployed everywhere to support diverse applications and service provisioning to various end-users. The LiFi infrastructure providers will need to offer LiFi access points (APs) resources as a service. This, however, requires a research challenge to be solved to dynamically and effectively allocate resources among service providers (SPs) while guaranteeing performance isolation among them and their respective users. This paper introduces an autonomic resource slicing (virtualization) scheme, which realizes autonomic management and configuration of virtual APs, in a LiFi attocell access network, based on SPs and their users service requirements. The developed scheme comprises of traffic analysis and classification, a local AP controller, downlink and uplink slice resources manager, traffic measurement, and information collection modules. It also contains a hybrid medium access protocol and an extended token bucket fair queueing algorithm to support uplink access virtualization and spectrum slicing. The proposed resource slicing scheme collects and analyzes the traffic statistics of the different applications supported on the slices defined in each LiFi AP and distributes the available resources fairly and proportionally among them. It uses a control algorithm to adjust the minimum contention window of user devices to achieve the target throughput and ensure airtime fairness among SPs and their users. The developed scheme has been extensively evaluated using OMNeT++. The obtained results show various resource slicing capabilities to support differentiated services and performance isolation
ORLA/OLAA: Orthogonal Coexistence of LAA and WiFi in Unlicensed Spectrum
Future mobile networks will exploit unlicensed
spectrum to boost capacity and meet growing user demands
cost-effectively. The 3rd Generation Partnership Project (3GPP)
has recently defined a License Assisted Access (LAA) scheme
to enable global Unlicensed LTE (U-LTE) deployment, aiming
at 1) ensuring fair coexistence with incumbent WiFi networks,
i.e., impacting on their performance no more than another
WiFi device; and 2) achieving superior airtime efficiency as
compared with WiFi. We show the standardized LAA fails to
simultaneously fulfill these objectives, and design an alternative
orthogonal (collision-free) listen-before-talk coexistence paradigm
that provides a substantial improvement in performance, yet
imposes no penalty on existing WiFi networks. We derive two
optimal transmission policies, ORLA and OLAA, that maximize
LAA throughput in both asynchronous and synchronous (i.e.,
with alignment to licensed anchor frame boundaries) modes of
operation, respectively. We present a comprehensive evaluation
through which we demonstrate that, when aggregating packets,
IEEE 802.11ac WiFi can be more efficient than LAA, whereas
our proposals attains 100% higher throughput, without harming
WiFi. We further show that long U-LTE frames incur up to
92% throughput losses on WiFi when using 3GPP LAA, whilst
ORLA/OLAA sustain >200% gains at no cost, even in the
presence of non-saturated WiFi and/or in multi-rate scenarios.This work was supported in part by the EC H2020 5G-Transformer Project under Grant 761536
ORLA/OLAA: Orthogonal Coexistence of LAA and WiFi in Unlicensed Spectrum
Future mobile networks will exploit unlicensed spectrum to boost capacity and
meet growing user demands cost-effectively. The 3GPP has recently defined a
Licensed-Assisted Access (LAA) scheme to enable global Unlicensed LTE (U-LTE)
deployment, aiming at () ensuring fair coexistence with incumbent WiFi
networks, i.e., impacting on their performance no more than another WiFi
device, and () achieving superior airtime efficiency as compared to WiFi.
In this paper we show the standardized LAA fails to simultaneously fulfill
these objectives, and design an alternative orthogonal (collision-free)
listen-before-talk coexistence paradigm that provides a substantial improvement
in performance, yet imposes no penalty on existing WiFi networks. We derive two
LAA optimal transmission policies, ORLA and OLAA, that maximize LAA throughput
in both asynchronous and synchronous (i.e., with alignment to licensed anchor
frame boundaries) modes of operation, respectively. We present a comprehensive
performance evaluation through which we demonstrate that, when aggregating
packets, IEEE 802.11ac WiFi can be more efficient than 3GPP LAA, whereas our
proposals can attain 100% higher throughput, without harming WiFi. We further
show that long U-LTE frames incur up to 92% throughput losses on WiFi when
using 3GPP LAA, whilst ORLA/OLAA sustain 200% gains at no cost, even in the
presence of non-saturated WiFi and/or in multi-rate scenarios.Comment: 14 pages, 7 figures, submitted to IEEE/ACM Transactions on Networkin
Quality of service differentiation for multimedia delivery in wireless LANs
Delivering multimedia content to heterogeneous devices over a variable networking environment while maintaining high quality levels involves many technical challenges. The research reported in this thesis presents a solution for Quality of Service (QoS)-based service differentiation when delivering multimedia content over the wireless LANs. This thesis has three major contributions outlined below:
1. A Model-based Bandwidth Estimation algorithm (MBE), which estimates the available bandwidth based on novel TCP and UDP throughput models over IEEE 802.11 WLANs. MBE has been modelled, implemented, and tested through simulations and real life testing. In comparison with other bandwidth estimation techniques, MBE shows better performance in terms of error rate, overhead, and loss.
2. An intelligent Prioritized Adaptive Scheme (iPAS), which provides QoS service differentiation for multimedia delivery in wireless networks. iPAS assigns dynamic priorities to various streams and determines their bandwidth share by employing a probabilistic approach-which makes use of stereotypes. The total bandwidth to be allocated is estimated using MBE. The priority level of individual stream is variable and dependent on stream-related characteristics and delivery QoS parameters. iPAS can be deployed seamlessly over the original IEEE 802.11 protocols and can be included in the IEEE 802.21 framework in order to optimize the control signal communication. iPAS has been modelled, implemented, and evaluated via simulations. The results demonstrate that iPAS achieves better performance than the equal channel access mechanism over IEEE 802.11 DCF and a service differentiation scheme on top of IEEE 802.11e EDCA, in terms of fairness, throughput, delay, loss, and estimated PSNR. Additionally, both objective and subjective video quality assessment have been performed using a prototype system.
3. A QoS-based Downlink/Uplink Fairness Scheme, which uses the stereotypes-based structure to balance the QoS parameters (i.e. throughput, delay, and loss) between downlink and uplink VoIP traffic. The proposed scheme has been modelled and tested through simulations. The results show that, in comparison with other downlink/uplink fairness-oriented solutions, the proposed scheme performs better in terms of VoIP capacity and fairness level between downlink and uplink traffic
Energy efficiency in wireless communications for mobile user devices
Mención Internacional en el tÃtulo de doctorMobile user devices’ market has experi-enced an exponential growth worldwide over the last decade, and wireless communications are the main driver for the next generation of 5G networks. The ubiquity of battery-powered connected devices makes energy efficiency a major research issue.
While most studies assumed that network interfaces dominate the energy consumption of wireless communications, a recent work unveils that the frame processing carried out by the device could drain as much energy
as the interface itself for many devices. This discovery poses doubts on prior energy models for wireless communications and forces us to reconsider existing energy-saving schemes.
From this standpoint, this thesis is de-voted to the study of the energy efficiency
of mobile user devices at multiple layers. To that end, we assemble a comprehensive en-ergy measurement framework, and a robust methodology, to be able to characterise a wide range of mobile devices, as well as individual parts of such devices.
Building on this, we first delve into the en-ergy consumption of frame processing within the devices’ protocol stack. Our results identify the CPU as the leading cause of this energy consumption. Moreover, we discover that the characterisation of the energy toll ascribed to the device is much more complex than the previous work showed. Devices with complex CPUs (several frequencies and sleep states) require novel methodologies and models to successfully characterise their consumption.
We then turn our attention to lower levels of the communication stack by investigating the behaviour of idle WiFi interfaces. Due to the design of the 802.11 protocol, together with the growing trend of network densification, WiFi devices spend a long time receiving frames addressed to other devices when they might be dormant. In order to mitigate this issue, we study the timing constraints of a commercial WiFi card, which is developed into a standard-compliant algorithm that saves energy during such transmissions.
At a higher level, rate adaptation and power control techniques adapt data rate and output power to the channel conditions. However, these have been typically studied with other metrics rather than energy efficiency in mind (i.e., performance figures such as throughput and capacity). In fact, our analyses and sim-ulations unveil an inherent trade-off between throughput and energy efficiency maximisa-tion in 802.11. We show that rate adaptation and power control techniques may incur inef-ficiencies at mode transitions, and we provide energy-aware heuristics to make such decisions following a conservative approach.
Finally, our research experience on simula-tion methods pointed us towards the need for new simulation tools commited to the middle-way approach: less specificity than complex network simulators in exchange for easier and faster prototyping. As a result, we developed a process-oriented and trajectory-based discrete-event simulation package for the R language, which is designed as a easy-to-use yet pow-erful framework with automatic monitoring capabilities. The use of this simulator in net-working is demonstrated through the energy modelling of an Internet-of-Things scenario with thousands of metering devices in just a few lines of code.El mercado de los dispositivos de usuario móviles ha experimentado un crecimiento exponencial a nivel mundial en la última década, y las comunicaciones inalámbricas son el principal motor de la siguiente generación de redes 5G. La ubicuidad de estos dispos-itivos alimentados por baterÃas hace de la eficiencia energética un importante tema de investigación.
Mientras muchos estudios asumÃan que la interfaz de red domina el consumo energético de las comuni-caciones inalámbricas, un trabajo reciente revela que el procesado de tramas que se lleva a cabo en el disposi-tivo podrÃa gastar tanta energÃa como la propia interfaz para muchos dispositivos. Este descubrimiento plantea dudas sobre los anteriores modelos energéticos para comunicaciones inalámbricas y nos obliga a reconsid-erar los esquemas de ahorro energético existentes.
Desde este punto de vista, esta tesis está dedicada al estudio de la eficiencia energética de dispositivos de usuario móviles en múltiples capas. Para ello, se construye un completo sistema de medida de energÃa, y una metodologÃa robusta, capaz de caracterizar un amplio rango de dispositivos móviles, asà como partes individuales de tales dispositivos.
A partir de esto, en primer lugar se profundiza en el consumo energético del procesamiento de tramas en la pila de protocolos de los dispositivos. Nuestros resul-tados identifican a la CPU como principal causa de tal consumo. Además, se descubre que la caracterización de la cuota energética adscrita al dispositivo es mucho más compleja que lo mostrado por el trabajo ante-rior. Los dispositivos con CPU complejas (múltiples frecuencias y modos de apagado) requieren nuevas metodologÃas y modelos para caracterizar su consumo de manera existosa.
En este punto, volvemos nuestra atención hacia niveles más bajos de la pila de comunicaciones para investigar el comportamiento de las interfaces WiFi en estado inactivo. Debido al diseño del protocolo 802.11, junto con la tendencia creciente hacia la densifi-cación de las redes, los dispositivos WiFi pasan mucho tiempo recibiendo tramas destinadas a otros dispos-itivos cuando podrÃan estar apagados. Para mitigar este problema, se estudian las limitaciones temporales de una tarjeta WiFi comercial, lo que posteriormente se utiliza para desarrollar un algoritmo conforme con el estándar que es capaz de ahorrar energÃa durante dichas transmisiones.
A un nivel más alto, las técnicas de adaptación de tasa y control de potencia adaptan la tasa de datos
y la potencia de salida a las condiciones del canal.
No obstante, estas técnicas han sido tÃpicamente es-tudiadas con otras métricas en mente (i.e., figuras de rendimiento como la tasa total y la capacidad). De hecho, nuestros análisis y simulaciones desvelan un conflicto entre la maximización de la tasa total y la efi-ciencia energética en 802.11. Se muestra que las técni-cas de adaptación de tasa y control de potencia pueden incurrir en ineficiencias en los cambios de modo, y se proporcionan heurÃsticos para tomar tales decisiones de un modo conservador y eficiente energéticamente.
Finalmente, nuestra experiencia investigadora en métodos de simulación nos hizo conscientes de la necesidad de nuevas herramientas de simulación comprometidas con un enfoque intermedio: menos especificidad que los complejos simuladores de re-des a cambio de facilidad y rapidez en el prototipado. Como resultado, se desarrolló un paquete de simu-lación por eventos discretos para el lenguaje R orien-tado a procesos y basado en trayectorias, el cual está diseñado como una herramienta fácil de utilizar a la par que potente con capacidad de monitorización au-tomática integrada. El uso de este simulador en redes se demuestra mediante el modelado en energÃa de un escenario de la Internet de las Cosas con miles de dis-positivos de medida en tan solo unas pocas lÃneas de código.Programa Oficial de Doctorado en IngenierÃa TelemáticaPresidente: Juan Manuel López Soler.- Secretario: Francisco Valera Pintor.- Vocal: Paul Horatiu Patra