Energy efficiency and quality of service optimization for constant bit rate real-time applications in 802.11 networks

In this paper, we propose a quality of service (QoS)‐sensitive energy efficiency optimization mechanism for 802.11 networks on the basis of the dynamic and simultaneous adjustment of the content window (W) and retry attempts limit (r) of the media access control (MAC) sublayer. The use of both operational variables let us not only find the optimum operational point regarding energy efficiency but also attain a positive impact on the QoS, which improves the results obtained with current single‐variable optimization strategies. The model under consideration includes external noise and does not impose the saturation condition in stations and as such is well suited for real‐time industrial applications under noisy channels. Results obtained from simulation confirm the advantages of adjusting simultaneously W and r versus adjusting either one separately, obtaining a slight improvement in energy efficiency and resulting in less loss and delay at the MAC sublayer.Unión Europea FP7‐223866Ministerio de Ciencia e Innovación DPI2010‐1915Ministerio de Ciencia e Innovación TEC2010‐20861Junta de Andalucía TIC‐633

Improving the Performance of Wireless LANs

This book quantifies the key factors of WLAN performance and describes methods for improvement. It provides theoretical background and empirical results for the optimum planning and deployment of indoor WLAN systems, explaining the fundamentals while supplying guidelines for design, modeling, and performance evaluation. It discusses environmental effects on WLAN systems, protocol redesign for routing and MAC, and traffic distribution; examines emerging and future network technologies; and includes radio propagation and site measurements, simulations for various network design scenarios, numerous illustrations, practical examples, and learning aids

Supporting Internet Access and Quality of Service in Distributed Wireless Ad Hoc Networks

In this era of wireless hysteria, with continuous technological advances in wireless communication and new wireless technologies becoming standardized at a fast rate, we can expect an increased interest for wireless networks, such as ad hoc and mesh networks. These networks operate in a distributed manner, independent of any centralized device. In order to realize the practical benefits of ad hoc networks, two challenges (among others) need to be considered: distributed QoS guarantees and multi-hop Internet access. In this thesis we present conceivable solutions to both of these problems. An autonomous, stand-alone ad hoc network is useful in many cases, such as search and rescue operations and meetings where participants wish to quickly share information. However, an ad hoc network connected to the Internet is even more desirable. This is because Internet plays an important role in the daily life of many people by offering a broad range of services. In this thesis we present AODV+, which is our solution to achieve this network interconnection between a wireless ad hoc network and the wired Internet. Providing QoS in distributed wireless networks is another challenging, but yet important, task mainly because there is no central device controlling the medium access. In this thesis we propose EDCA with Resource Reservation (EDCA/RR), which is a fully distributed MAC scheme that provides QoS guarantees by allowing applications with strict QoS requirements to reserve transmission time for contention-free medium access. Our scheme is compatible with existing standards and provides both parameterized and prioritized QoS. In addition, we present the Distributed Deterministic Channel Access (DDCA) scheme, which is a multi-hop extension of EDCA/RR and can be used in wireless mesh networks. Finally, we have complemented our simulation studies with real-world ad hoc and mesh network experiments. With the experience from these experiments, we obtained a clear insight into the limitations of wireless channels. We could conclude that a wise design of the network architecture that limits the number of consecutive wireless hops may result in a wireless mesh network that is able to satisfy users’ needs. Moreover, by using QoS mechanisms like EDCA/RR or DDCA we are able to provide different priorities to traffic flows and reserve resources for the most time-critical applications

Energy Efficiency in Communications and Networks

The topic of "Energy Efficiency in Communications and Networks" attracts growing attention due to economical and environmental reasons. The amount of power consumed by information and communication technologies (ICT) is rapidly increasing, as well as the energy bill of service providers. According to a number of studies, ICT alone is responsible for a percentage which varies from 2% to 10% of the world power consumption. Thus, driving rising cost and sustainability concerns about the energy footprint of the IT infrastructure. Energy-efficiency is an aspect that until recently was only considered for battery driven devices. Today we see energy-efficiency becoming a pervasive issue that will need to be considered in all technology areas from device technology to systems management. This book is seeking to provide a compilation of novel research contributions on hardware design, architectures, protocols and algorithms that will improve the energy efficiency of communication devices and networks and lead to a more energy proportional technology infrastructure

A heterogeneous short-range communication platform for internet of vehicles

The automotive industry is rapidly accelerating toward the development of innovative industry applications that feature management capabilities for data and applications alike in cars. In this regard, more internet of vehicles solutions are emerging through advancements of various wireless medium access-control technologies and the internet of things. In the present work, we develop a short-range communication–based vehicular system to support vehicle communication and remote car control. We present a combined hardware and software testbed that is capable of controlling a vehicle’s start-up, operation and several related functionalities covering various vehicle metric data. The testbed is built from two microcontrollers, Arduino and Raspberry Pi 3, each of which individually controls certain functions to improve the overall vehicle control. The implementation of the heterogeneous communication module is based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 and IEEE 802.15 medium access control technologies. Further, a control module on a smartphone was designed and implemented for efficient management. Moreover, we study the system connectivity performance by measuring various important parameters including the coverage distance, signal strength, download speed and latency. This study covers the use of this technology setup in different geographical areas over various time spans

Comunicações cooperativas em redes IEEE 802.11 multi-débito

Doutoramento em TelecomunicaçõesEsta tese apresenta um estudo sobre alguns dos protocolos de cooperação MAC para redes sem fios utilizando o sistema IEEE 802.11 multi-débito. É proposto um novo modelo de arquitetura para a categorização e análise da cooperação em redes sem fios, tendo este modelo sido aplicado a protocolos cooperativos existentes para camada MAC. É investigado como as características do meio físico, assim como os requisitos de níveis superiores podem ser aplicados ao processo de cooperação, com vista a melhorar as características de funcionamento da rede de comunicações. Para este propósito são exploradas as métricas mais relevantes para o processo de cooperação. São igualmente estudados os limites impostos pelos protocolos da camada MAC e as limitações práticas impostas por protocolos da família de normas que compõem o IEEE 802.11. Neste trabalho foi criada uma métrica multicamada, que permite considerar os requisitos aplicacionais de performance e o tipo de tráfego, assim como a mobilidade dos dispositivos, no funcionamento dos mecanismos de cooperação. Como forma de validação, e para corretamente avaliar o impacto da métrica, um novo protocolo de cooperação foi desenvolvido e implementado. O seu funcionamento é descrito de forma analítica assim como validado através de a um ambiente de simulação. Os resultados obtidos mostram que a utilização de uma métrica multicamada é uma técnica robusta, fornecendo melhorias consistentes no contexto de redes IEEE 802.11. São igualmente demonstradas várias outras características de funcionamento com impacto para as comunicações. Estes dados fornecem uma visão real e encorajadora para a realização de mais pesquisas para a melhoria da performance dos protocolos cooperativos, assim como a sua utilização num variado número de aplicações futuras. No final do documento são apresentados alguns desafios para a continuação da investigação deste tópico.This thesis presents a study on cooperative MAC protocols in Multi-rate IEEE 802.11 wireless networks. We proposed a novel architectural framework for cooperation algorithms in wireless network. This behavior model was considered for existing cooperative MAC protocols. A classification of these protocols was presented based on their cooperation objectives. We investigate how physical layer specifications and higher layer requirements can be applied in cooperation MAC protocols to enhance the overall network performance. For this purpose, we exploit the appropriate metrics which are consistent to the cooperation objectives. Performance bounds provided by MAC protocols and practical limitations posed by IEEE 802.11 standards have been also studied. A cross layer metric was achieved in cooperative MAC protocols to adapt cooperation performance to traffic service requirements and mobility scenario. In order to realize the impact of this metric, a new cooperative MAC protocol is designed and implemented. Analytical and simulation of this protocol was performed in different scenarios and environments. The obtained results have shown a robust technique in providing consistent cross layer optimization in context of IEEE 802.11 networks. A number of findings was experienced which are illustrated at the end. These observations would enhance and encourage potential research in the area and optimize the performance of cooperative protocols for a number of interesting applications in future. A summary of future research challenges is presented at the end

Voice-over-IP (VoIP) over wireless local area networks (WLAN).

Wang Wei.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.Includes bibliographical references (leaves 80-83).Abstracts in English and Chinese.Chapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Motivations and Contributions --- p.1Chapter 1.2 --- Organization of the Thesis --- p.4Chapter Chapter 2 --- Background --- p.6Chapter 2.1 --- IEEE 802.11 --- p.6Chapter 2.1.1 --- Distributed Coordination Function (DCF) / Point Coordination Function (PCF) --- p.7Chapter 2.1.2 --- Types of Networks --- p.8Chapter 2.1.3 --- The 802.11 MAC Sublayer Protocol --- p.9Chapter 2.1.4 --- Why CSMA/CA for Wireless LAN? --- p.11Chapter 2.2 --- Voice over IP (VoIP) --- p.13Chapter 2.2.1 --- Speech Codec --- p.13Chapter 2.2.2 --- The H.323 Standard --- p.13Chapter 2.3 --- Related Work --- p.15Chapter 2.3.1 --- Capacity limits of VoIP over WLAN --- p.16Chapter 2.3.2 --- Methods for increasing VoIP capacity over WLAN --- p.16Chapter 2.3.3 --- Interference between traffic of VoIP and other applications --- p.18Chapter Chapter 3 --- VoIP Multiplex-Multicast Scheme --- p.20Chapter 3.1 --- System Architecture --- p.20Chapter 3.2 --- Packet Multiplexing and Multicasting --- p.22Chapter 3.3 --- Header Compression --- p.24Chapter 3.4 --- Connection Establishment --- p.29Chapter Chapter 4 --- Capacity Analysis --- p.31Chapter 4.1 --- VoIP Capacity Analysis for 802. 11b --- p.31Chapter 4.1.1 --- Capacity of Ordinary VoIP over WLAN --- p.32Chapter 4.1.2 --- Capacity of Multiplex-Multicast Scheme over WLAN --- p.33Chapter 4.2 --- "VoIP Capacity Analysis for 802,11a and 802.11g" --- p.34Chapter 4.3 --- VoIP Capacity with VBR Sources --- p.38Chapter 4.4 --- Simulations --- p.38Chapter Chapter 5 --- Delay Performance --- p.41Chapter 5.1 --- Access Delay --- p.42Chapter 5.2 --- Extra Delay Incurred by the Multiplex-Multicast Scheme --- p.47Chapter Chapter 6 --- VoIP Co-existing with TCP Interference Traffic --- p.49Chapter 6.1 --- Ordinary VoIP co-existing with TCP over WLAN --- p.49Chapter 6.1.1 --- Problem Caused by TCP Interference --- p.49Chapter 6.1.2 --- Solutions --- p.52Chapter 6.2 --- M-M VoIP coexisting with TCP over WLAN --- p.53Chapter 6.3 --- 802.11e --- p.56Chapter 6.3.1 --- EDCA --- p.56Chapter 6.3.2 --- ACK Policies --- p.58Chapter 6.3.3 --- VoIP over EDCA --- p.58Chapter Chapter 7 --- Experimental Validation --- p.61Chapter 7.1 --- Transmission Errors --- p.61Chapter 7.2 --- Prototype Implementation --- p.62Chapter Chapter 8 --- VoIP over Ad Hoc Networks --- p.65Chapter 8.1 --- Mobile Ad Hoc Networks (MANET) and Wireless Distributed System (WDS) --- p.65Chapter 8.2 --- The M-M Scheme in WDS --- p.67Chapter 8.2.1 --- Modified System Architecture --- p.67Chapter 8.2.2 --- Delay Performance --- p.68Chapter 8.2.3 --- Analysis of M-M Scheme in WDS --- p.69Chapter 8.2.4 --- Capacity Improvement --- p.70Chapter 8.2.5 --- Delay Improvement --- p.71Chapter 8.2.6 --- Spectrum Reuse --- p.71Chapter Chapter 9 --- Conclusions --- p.76References --- p.8