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This lecture presents a discussion of Quality of Service (QoS) in wireless networks over unlicensed
spectrum. The reason for this lecture is that the licensed spectrum is getting saturated due to the
pervasiveness of handheld devices and users’ rising demand for multimedia content, such as mov-
ies and television content, to be delivered on handheld devices. Hence, we are seeing and will see
more and more multimedia traffic going over unlicensed spectrum with protocols such as IEEE
802.11. However, to yield high quality in multimedia content transmission and delivery between
content providers and consumers, one needs to pay attention to Quality of Service, similarly as is
done in network protocols and resource management over licensed spectrum. This lecture aims to
provide the entry point for interested readers such as engineers and researchers within service pro-
viders/companies who develop and/or provide multimedia services to mobile customers or graduate
students and to other researchers who are conducting studies of the next generation of wireless
networks over unlicensed spectrum for new mobile multimedia applications.
The lecture’s aim is not to be comprehensive, since the QoS topic in wireless networks and
wireless networks over unlicensed spectrum has a very broad scope, and it has been explored in
the research community and by the industry at large over the past 15–20 years. The lecture’s goal
is to provide insights into some of the problems when one embarks on designing QoS in wireless
networks over unlicensed spectrum for multimedia applications. The focus is on some of the crucial
QoS-aware functions, abstractions, models, and corresponding protocols in this space, as well as
lessons learned that I have gathered over the past 10 years working in this area.
Chapter 1 introduces the QoS concept, the scope of the types of wireless networks, and the
QoS-aware functions we consider throughout the lecture. Chapter 2 is about formulating QoS and
resource allocation problems as optimization problems. Chapter 3 discusses QoS-aware functions,
abstractions, models, algorithms, and protocols for bandwidth allocation and management, and
Chapter 4 is about delay control and management functions and their corresponding abstractions,
algorithms, and protocols. Chapter 5 is about QoS-aware routing, and it completes the key set of
functions to consider when embedding QoS capabilities within wireless networks over unlicensed
spectrum.
Preface
xiv QUALITY OF SERVICE IN WIRELESS NETWORKS OVER UNLICENSED SPECTRUM
Chapter 1 has the main goal of introducing readers to the overall concept of Quality of
Service (QoS) as well as identifying the network scope where the QoS concept will be considered,
such as the single hop wireless networks and mobile wireless networks over unlicensed spectrum.
The chapter also outlines the key set of functions that need to be considered in order to gain certain
levels of QoS such as admission control, resource allocation, monitoring, scheduling, and routing.
Chapter 2 introduces readers to the resource allocation problem in wireless networks over un-
licensed spectrum. Important concepts, such as interference among nodes, interference/contention
graphs, clique concepts in contention graphs, and utility-based problems and price-based problem
formulations are discussed. The aim is to have a reader look at the provisioning of QoS as a resource
optimization problem and show the strong differences when provisioning QoS in wired and wire-
less networks.
Chapter 3 concentrates on bandwidth as the network resource and the goal is to provide
rate/bandwidth guarantees over unlicensed spectrum networks. This chapter presents bandwidth
allocation, enforcement, and management functions with their algorithmic designs, which represent
theoretical and practical solutions to the problems articulated in Chapter 2.
Chapter 4 is about delay guarantees, and the goal is to introduce delay functions with their
algorithmic designs. We present delay functions that enforce delay guarantees such as allocation,
monitoring and scheduling, and adaptation functions that respond to varying demands coming
from users and applications, and underlying hardware, system, and network constraints.
Chapter 5 discusses routing functions that aim to preserve QoS guarantees as traffic is routed
through a wireless network. The goal is to introduce readers to a large diversity of considerations
when routing occurs since different contextual information may influence and assist in routing. This
chapter presents routing difficulties, algorithmic solutions, and protocols, if one considers impor-
tant contexts such as location, reliability, and energy that guide routing in wireless networks over
unlicensed spectrum.
Each chapter finishes with its own conclusion discussion; hence, the overall lecture concludes
with a large number of references which might be helpful to readers as they dive into this important
and exciting area of broad interest.
Klara Nahrstedt

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