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Connection admission control for real-time applications in WiMax networks
i
ABSTRACT
Connection admission control (CAC) algorithms are used in WiMax to decide whether an
incoming connection should be accepted or rejected. Different QoS requirements for different
types of applications leading to the implementation of CAC on WiMax networks. Basic
overview of WiMax including QoS support mechanism is presented. Theoretical concept of
CAC and its applications in WiMax to guarantee QoS are discussed. Different methods
proposed by different researcher on CAC is been presented in chapter III, IV and chapter V
including logical validation of the method. This report also critically analyzes the work done
by the researcher by comparing the outcomes of the proposed methods. Furthermore, future
research opportunities are evaluated.
Connection admission control for real-time applications in WiMax networks
ii
SUMMARY
The rapid growth of broadband wireless access (BWA) has increased the demand of new
applications such as VoIP, video conferencing, online gaming each of which has different
requirements for QoS. And for real-time applications they require some minimal level of
resources to keep their performance level on the desired state.
In the WiMax network, when a new connection request arrives at the base station, the
connection admission control (CAC) mechanism takes the decision whether to accept the
connection or reject the connection. The connection will be accepted if and only if the
minimal requirements for that request can be satisfied by the network.
This project works towards achieving desired level of quality of service for real-time
applications in WiMax networks by applying connection admission control algorithm
developed by many current and past researchers. Connection admission control algorithm is
an open issue and effective method for QoS guarantee. This report also gives an introduction
to the WiMax technology and the issues related to QoS and CAC. Three major approaches
towards admission control algorithm proposed for assuring QoS is analyzed in this report.
Three different types of approaches presents different types of methods, different outcome
and conclusions which are been logically validated also. Each of the proposed algorithm
works towards achieving better QoS for real-time applications as well as maximizing the
network utilization also.
This project report includes one specific chapter that presents a brief evaluation and critical
analysis of the three approaches toward solving the problem. Among the three approaches one
method is identified as the best one, and several recommendations for future work has been
presented also.
Connection admission control for real-time applications in WiMax networks
iii
TABLE OF CONTENT
ABSTRACT ............................................................................................................................................................I
SUMMARY........................................................................................................................................................... II
TABLE OF CONTENT ..................................................................................................................................... III
LIST OF FIGURES.............................................................................................................................................VI
LIST OF TABLES............................................................................................................................................. VII
GLOSSARY......................................................................................................................................................VIII
ACKNOWLEDGEMENTS ................................................................................................................................XI
DEDICATION ................................................................................................................................................... XII
CHAPTER I........................................................................................................................................................... 1
PROJECT INTRODUCTION ............................................................................................................................ 1
1.1 INTRODUCTION .............................................................................................................................................. 1
1.2 BACKGROUND OF THE PROJECT..................................................................................................................... 3
1.3 CONNECTION ADMISSION CONTROL.............................................................................................................. 4
1.4 ADMISSION CONTROL FOR QOS..................................................................................................................... 5
1.5 PROJECT AIMS & OBJECTIVES ....................................................................................................................... 5
1.6 PROJECT ROADMAP ....................................................................................................................................... 6
1.7 APPROACHES AND METHODOLOGY................................................................................................................ 6
1.8 TOOLS AND TECHNOLOGIES USED................................................................................................................. 7
1.9 REPORT LAYOUT ........................................................................................................................................... 7
CHAPTER II ....................................................................................................................................................... 10
WIMAX OVERVIEW AND PROBLEM IDENTIFICATION....................................................................... 10
2.1 BACKGROUND STUDY OF IEEE 802.16 AND WIMAX................................................................................... 10
2.2 WIMAX TOPOLOGIES .................................................................................................................................. 11
2.3 WIMAX PROTOCOL LAYERS........................................................................................................................ 12
2.3.1 WiMax Physical Layer ........................................................................................................................ 14
2.3.2 WiMax MAC layer .............................................................................................................................. 15
2.3.2.1 Convergence Sublayer ..................................................................................................................... 16
2.3.2.2 Medium Access Control Common Part Sublayer (MAC CPS)......................................................... 17
2.3.2.3 Security/ Privacy Sublayer............................................................................................................... 17
2.4 QOS SUPPORT IN WIMAX NETWORK........................................................................................................... 18
2.5 PROBLEM STATEMENT................................................................................................................................. 21
2.6 CONNECTION ADMISSION CONTROL (CAC) ................................................................................................ 22
2.6.1 Need of CAC in WiMax....................................................................................................................... 22
2.6.2 Purpose of Connection Admission Control in WiMax network........................................................... 23
2.6.3 Basic Components of Connection Admission Control (CAC) ............................................................. 24
2.6.4 Parameter-based and Measurement-based Admission Control.......................................................... 25
2.7 SUMMARY ................................................................................................................................................... 26
Connection admission control for real-time applications in WiMax networks
iv
CHAPTER III...................................................................................................................................................... 27
MEASUREMENT-BASED ADMISSION CONTROL ................................................................................... 27
3.1 INTRODUCTION TO RELEVANT PAPERS ......................................................................................................... 27
3.2 AIMS AND OBJECTIVE.................................................................................................................................. 27
3.3 APPROACHES AND METHODOLOGY.............................................................................................................. 28
3.4 COMPONENTS OF MEASUREMENT-BASED ADMISSION CONTROL .................................................................. 28
3.5 EXPLANATION OF THE PROCESS................................................................................................................... 29
3.5.1 M-LWDF Scheduling Algorithm ......................................................................................................... 29
3.5.2 Proposed Algorithm and Simulation Parameters ............................................................................... 31
3.6 RESULTS OBTAINED BY THE AUTHOR........................................................................................................... 35
3.6.1 Packet Delay ....................................................................................................................................... 35
3.6.2 Connection blocking probability......................................................................................................... 36
3.7 CONCLUSION BY THE AUTHOR .................................................................................................................... 37
3.8 LOGICAL VALIDATION AND CONCLUSION ................................................................................................... 37
3.9 SUMMARY ................................................................................................................................................... 38
CHAPTER IV ...................................................................................................................................................... 39
ADAPTIVE CAC FOR QOS PROVISIONING IN WIMAX........................................................................... 39
4.1 INTRODUCTION TO RELEVANT PAPERS ........................................................................................................ 39
4.2 AIMS AND OBJECTIVES ................................................................................................................................ 39
4.3 APPROACHES AND METHODOLOGIES........................................................................................................... 39
4.4 EXPLANATION OF THE PROCESS................................................................................................................... 40
4.5 RESULTS OBTAINED BY THE AUTHORS........................................................................................................ 42
4.6 AUTHORS CONCLUSION............................................................................................................................... 44
4.7 LOGICAL VALIDATION AND CONCLUSION ................................................................................................... 44
4.8 SUMMARY ................................................................................................................................................... 45
CHAPTER V........................................................................................................................................................ 46
STATISTICAL CONNECTION ADMISSION CONTROL............................................................................ 46
5.1 INTRODUCTION TO RELEVANT PAPERS ........................................................................................................ 46
5.2 AIMS AND OBJECTIVES ................................................................................................................................ 46
5.3 APPROACHES AND METHODOLOGY.............................................................................................................. 46
5.4 EXPLANATION OF THE PROCESS................................................................................................................... 47
5.5 RESULTS OBTAINED BY THE AUTHORS........................................................................................................ 49
5.6 CONCLUSION BY THE AUTHORS................................................................................................................... 50
5.7 LOGICAL VALIDATION AND CONCLUSION ................................................................................................... 50
5.8 SUMMARY ................................................................................................................................................... 51
CHAPTER VI ...................................................................................................................................................... 52
CRITICAL APPRAISAL, RECOMMENDATION AND POSSIBLE FUTURE WORK................................ 52
6.1 ANALYTICAL REVIEW/ CRITICAL APPRAISAL.............................................................................................. 52
6.2 RECOMMENDATION FOR FUTURE WORK ..................................................................................................... 55
6.3 SUMMARY ................................................................................................................................................... 56
Connection admission control for real-time applications in WiMax networks
v
CHAPTER VII .................................................................................................................................................... 57
CONCLUSIONS .............................................................................................................................................. 57
REFERENCES:................................................................................................................................................... 59
APPENDIX A ...................................................................................................................................................... 64
APPENDIX B....................................................................................................................................................... 65
APPENDIX C ...................................................................................................................................................... 66
Connection admission control for real-time applications in WiMax networks
vi
LIST OF FIGURES
Figure 1 Illustration of wireless network type [2] .....................................................................2
Figure 2 Illustration of WiMax network in (a) PMP and (b) Mesh topology [1]....................12
Figure 3 Seven layer OSI reference model, In WiMax only the two first layers are defined [2]
..................................................................................................................................................13
Figure 4 IEEE 802.16 protocol architecture [1] ....................................................................14
Figure 5 General format of MAC PDU [2]. ............................................................................16
Figure 6 Protocol layers of IEEE 802.16 [2] ...........................................................................17
Figure 7 Security Sublayer [2] [3]...........................................................................................18
Figure 8 QoS frame work (a) uplink mode (b) downlink mode [18] ......................................19
Figure 9 QoS requirements for different applications [14] .....................................................20
Figure 10 QoS architecture in WiMax Network [18].............................................................21
Figure 11 Basic Architecture of Admission control [10] ......................................................23
Figure 12 Traditional CAC algorithm in Wireless Networks [16]..........................................25
Figure 13 Components of MBAC [16]....................................................................................29
Figure 14 M-LWDF scheduler [16]........................................................................................30
Figure 15 CAC algorithm for real-time traffic [16] ................................................................32
Figure 16 Average packet delay vs. arrival rate of request [16]..............................................36
Figure 17 Connection blocking probability vs. arrival rate [16] .............................................36
Figure 18 Comparison of new connection blocking probabilities between dynamic and fixed
guard channel schemes [6] .......................................................................................................43
Figure 19 Blocking and dropping probability in Dynamic Guard Channel scheme [6]..........43
Figure 20 Average delay among service classes [6]................................................................44
Figure 21 Traffic parameters used in [24] ...............................................................................48
Figure 22 Blocking probability [24]........................................................................................49
Figure 23 Overflow probability [24] .......................................................................................49
Figure 24 Utilization ratio [24].................................................................................................49
Figure 25 Average delay in MBCAC [16] ............................................................................54
Figure 26 Average delay in Adaptive CAC [6].......................................................................54
Connection admission control for real-time applications in WiMax networks
vii
LIST OF TABLES
Table 2.1 Basic Data in IEEE 802.16 Standards [3]. .............................................................11
Table 2.2 The five physical interfaces defined in the IEEE 802.16 standard [2]...................15
Table 3.1 Simulation Parameters used in [16]. ……………………………………………. 46
Connection admission control for real-time applications in WiMax networks
viii
GLOSSARY
AMC Adaptive Modulation and Coding
ATM Asynchronous Transmission Mode
BE Best Effort
BS Base Station
BWA Broadband Wireless Access
CAC Connection Admission Control
CPS Common Part Sublayer
CS Convergence Sublayer
CID Connection Identifier
CBR Constant Bit Rate
DSA Dynamic Service Addition
DSD Dynamic Service Deletion
DSC Dynamic Service Change
DL Downlink
FCFS First Come First Serve
FDD Frequency Division Duplexing
GSM Global System for Mobile Communications
HTTP Hypertext Transfer Protocol
ITU International Telecommunication Union
IEEE Institute of Electrical and Electronics Engineers
IETF Internet Engineering Task Force
IP Internet Protocol
IPv4 Internet Protocol version 4
Connection admission control for real-time applications in WiMax networks
ix
IPv6 Internet Protocol version 6
LAN Local Area Network
LOS Line of Sight
LLC Logical Link Control
MAC Medium Access Control
MPDU Medium Access Control Protocol Data Unit
MSDU Medium Access Control Service Data Unite
MAC CPS Medium Access Control Common Part Sublayer
MAC SAP Medium Access Control Service Access Point
MPEG Moving Picture Experts Group
MBAC Measurement Based Admission Control
M-LWDF Modified Largest Weighted Delay First
NLOS Non-line of Sight
nrtPS Non-real-time Polling Service
OFDM Orthogonal Frequency Division Multiplexing
OFDMA Orthogonal Frequency-Division Multiple Access
OSI Open Systems Interconnection
PMP Point-to-Multipoint
PHY Physical Layer
PDU Protocol Data Unite
PSDU Protocol Service Data Unite
PKM Privacy & Key management
QoS Quality of Service
rtPS Real-time Polling service
SS Subscriber Station
SDU Service Data Unite
Connection admission control for real-time applications in WiMax networks
x
TDD Time Division Duplexing
TDM Time Division Multiplexing
TDMA Time Division Multiple Access
UGS Unsolicited Grant Service
UL Uplink
VoIP Voice Over Internet Protocol
VBR Variable Bit Rate
WAN Wide Area Network
WMAN Wireless Metropolitan Area Network
WLAN Wireless Local Area Network
WPAN Wireless Personal Area Network
WiMax Worldwide Interoperability for Microwave Access
Connection admission control for real-time applications in WiMax networks
xi
ACKNOWLEDGEMENTS
Beginning with the name of Almighty ALLAH.
First and foremost, extreme gratitude and thanks are due to my Parents, who have always
supported and encouraged me throughout my academic life. They have gone through many
sacrifices and also helped me fund my studies at the London Metropolitan University, in order
to help me realise my dream to obtaining a Masters degree.
Secondly, gratitude is due to, Mr Nicholas Ionnides and prof. Igor Schagaev who has heard
my project and agreed to supervise me through out the project session. They were very much
helpful and more than a project supervisor to me.
Thirdly, gratitude is also due to, Mr Nurul Hossain, who has been more than ‘a friend, during
the course of this project and whole Masters Course. Thanks for being with me, listing to me
during my brain-storming moments and also for pushing me through to meeting the project
deadline.
And last, but not the least another note of thanks goes out to all the University teaching staff
that I had come across during the course of the Masters programme. I shall cherish the
knowledge I have acquired from you. Especially Prof. Igore and Mr Hassan Kazmanian who
introduced the technique of Research Report writing to me through course lectures of CCP
155N.
Connection admission control for real-time applications in WiMax networks
xii
DEDICATION
To my Parents,
Md Tazul Islam Bhuiyan, Mrs Peara Begum
And my dearest brother,
Robin
Connection admission control for real-time applications in WiMax networks
1
CHAPTER I
PROJECT INTRODUCTION
This chapter provides with a brief introduction to the project idea, its roadmap and also acts as
an introduction to this report.
1.1 Introduction
Wireless communication concept starts up when the Maxwell Equations (of electromagnetic
wave) shows the aspect that it is possible to transfer information without the need of any wire
[2]. All over the twentieth century a lot of research on wireless communication (electronic
propagation of signal/data) was done by many researcher and so far a lot of wireless
communication system is been introduced and today a large number of wireless transmission
technologies exists. Wireless communication technologies were a new revolution in human
civilization history. As the growth of wireless communication increases human being started
to demand more and more from it. The wireless revolution that was started by voice
transmission (GSM system) only, is now a mean of voice, video, VoIP, online gaming etc.
But it does not stops here as it comes to the point of reliability, availability, integrity and
above all a better QoS and off course with very high speed.
Over the last decade wireless communication has not only made an impact on residential
users but had made a great impact on global economy also. In the mean time both the
residential and commercial users has become much more familiar with some personal devices
like cell phones, laptops, palmtops etc... [12]. Many new multimedia based applications like
VoIP, video on demand, video conferencing was implemented also. Broadband access was
Connection admission control for real-time applications in WiMax networks
2
proposed by International Telecommunication Union (ITU) to meet up the demand of
growing wireless communication. IEEE 802 project working group 16 developed BWA
(Broadband Wireless Access) [5]. And WiMax (Commercial name of IEEE 802.16 standard)
was then proposed. WiMax guarantee a better QoS by the potential and efficient use of
bandwidth.
Rapid growth of wireless communication with the increasing number of wireless users must
provide better Quality of Service (QoS) to different service applications as well as maintaing
the high speed. For a wireless communication system, utilization of available network
resources with high QoS is a big challenging issue as it has become the fundamental
requirements for better communication. Besides interference caused by the concurrent user
transmission might get the opportunity to instigate the users to race for limited wireless
resources [1]. To cope with the need of user community the wireless network might have to
reject new connection where the available resource is limited to maintain the high level of
QoS.
Figure 1 Illustration of wireless network type [2]
Connection admission control for real-time applications in WiMax networks
3
Researchers are considering Connection Admission Control (CAC) as a solution for managing
the wireless resources. In this project I propose that, CAC is a solution for IEEE 802.16
standard that support real time applications while maintaing higher QoS. The CAC algorithms
are used to decide whether a new connection will be admitted or rejected to make sure the
required QoS is achieved. A new connection is admitted if the network has the available
resources for that connection. Furthermore, to overcome the challenge of limited resources it
needs to be assured that the available resources are utilized properly to gain improved system
performance. Therefore CAC has become an interest of many researchers.
The fundamental requirements of WiMax are to deliver desired level of QoS in order to be the
possible winning technology for tomorrow. In this paper after a details discussion of the
WiMax standard, I will provide an in depth overview on the quality of service (QoS) supports
provided by WiMax technology. I will survey the existing literature on WiMax and
Connection Admission Control (CAC) and particular attention will be given to the Admission
algorithm. I will concludes this paper with an overview of the actual research challenges,
pointing out and detailing the most promising directions to pursue further research in this
field.
1.2 Background of the Project
As stated earlier CAC is been recognised as the Radio Resource Management (RRM)
technique [16]. The functionality of CAC is to manage different types of traffic to maintain
the QoS level. CAC is an algorithm that maintains the desired level of QoS by limiting the
number of ongoing connections inside the network. CAC inside a WiMax network starts
working whenever there is a request for new connection. The working principle of this
algorithm is very simple, when a user request a new connection the CAC took its decision on
Connection admission control for real-time applications in WiMax networks
4
the basis of how much resource is available. There are few simple questions to answer before
taking any decision. What is the bandwidth required for the new connection? How much
bandwidth is available in the network to support that new connection? Will the new
connection cause any disruption to the current ongoing connections? The CAC takes the
decision after a positive feedback for all these simple questions. A new connection will be
admitted if and only if the network has enough resource to support the desired level of QoS
and it does not intercept the current ongoing calls. Even though there is some more challenge
left. Unlike wired connection wireless connection needs to be concerned about some other
factors, such as multiple channel interference, path delay, multi path propagation, handoff and
above all limited bandwidth.
1.3 Connection Admission Control
The Internet Engineering Task Force (IETF) started the Integrated Services working group to
standardize a new resource allocation architecture and service models in the early 1990's
which is based on per-flow resource reservation. To transmit traffic onto the network a new
application/connection must reserve the resource, before it starts sending traffic in order to
have the assurance for resources. There are several steps involved in this resource reservation
process. First, the application must define and characterize the source of the traffic and the
requirements of resources. The network then uses a routing protocol to and a path based on
the requested resources. Next a reservation protocol is used to install the reservation state
along the path. At each hop, an admission control module checks whether sufficient resources
(usually in terms of bandwidth and buffer space) are available to accept the new connections.
Exclusive resources are set up for the new connection, if the admission control module admits
a connection based on the available resources. The job of the admission control module is to
Connection admission control for real-time applications in WiMax networks
5
ensure that QoS guarantees of existing flows are not affected by the addition of a new flow;
otherwise the request must be rejected.
1.4 Admission Control for QoS
A well design admission control algorithm has important effect on the network performance,
as an inefficient algorithm may unnecessarily denies access to flows that could have been
successfully admitted [12]. Same way, an algorithm that inappropriately accepts many flows
will produce QoS violations. In principle QoS guarantees can be offered on a deterministic or
a statistical basis [11]. Deterministic guarantees are hard bound on the transport performance
(e.g. bounded packet transfer delay). Such bounds are relatively easy to support on an end-to-
end basis, particularly in the case of packet delay measure [12]. Unlike deterministic services,
a statistical or soft real-time service associates a small violation probability with the delay and
throughput bounds, as needed to a utilization gain over a purely worst case approach [12].
1.5 Project Aims & Objectives
The aims and objectives of this report are to present a research work on a specific area. The
research area of this report is the Connection Admission Control that helps maintain the
higher Level of quality of service for different applications in Wimax networks.
The main objectives of this project are:
To understand and identify the problem of real-time applications to maintain desired
QoS level in WiMax network.
To understand and present the need of CAC in WiMax networks.
To understand and present different CAC algorithms.
To identify and present relevant research approaches towards CAC algorithms.
Connection admission control for real-time applications in WiMax networks
6
To identify and categorize the different approaches done toward CAC to obtain better
QoS.
To understand, identify and analyze the first approach based on Measurement-based
admission control.
To understand, identify and analyze the second approach based on adaptive
connection admission control.
To understand, identify and analyze the third approach based on statistical connection
admission control.
To present a critical analysis and evaluate the three approaches collectively.
To recommend further possible methods towards the solution of QoS for real-time
applications in WiMax networks.
1.6 Project Roadmap
The following numbered steps give an idea of the proposed project roadmap:
1. Documentation of IEEE 802.16 (WiMax) standard and problem statement.
2. Literature study of IEEE 802.16 standard and CAC.
3. An overview of current situation of the proposed area.
4. A brief discussion on the approaches done by different researcher on CAC
5. A critical and collective analysis of the approaches toward CAC.
6. Documentation of final report.
1.7 Approaches and methodology
This thesis paper is based on logical analysis of the problem area and it also analyzes different
research approaches towards CAC to maintain the desired level of QoS in WiMax. Although
it is expectable that a thesis paper should be based on numerical and simulation approach but
Connection admission control for real-time applications in WiMax networks
7
it was not possible due to time constrains. In this research I have presented the basic structure
of WiMax; i.e., IEEE 802.16 standard theoretically. A fair approach is been made to
understand the CAC algorithm and the need of CAC algorithm in WiMax networks by
identifying a specific problem area. This thesis report briefly discusses three different
approaches towards CAC by different researcher by presenting their approaches and
methodologies. This report also present and validated the outcome achieved by the research
approaches present in this report.
1.8 Tools and Technologies Used
Several latest tools and technologies have been used in this project. Below is a brief
Mention of their usage.
Hardware and Operating Systems
Hewlett-Packard laptop computer (AMD Turion (tm) X2 Dual-Core Mobile
RM 72, 2.1 GHz Processor Speed and 4.00 GB Memory)
Microsoft Windows Vista 2007 (Home Premium, Service Pack 1)
London Metropolitan University Labs and Lab Computers.
Microsoft Office 2003/2007 for report documentation.
1.9 Report Layout
This whole document is divided into chapters. Each chapter has its own purpose and each
chapter discussed in this report presents a clear discussion of topics and issues that is relevant
to the project.
Connection admission control for real-time applications in WiMax networks
8
Chapter I: This chapter is an introduction to the project area. This chapter consists of nine
sections each of which is presented with specific issues. This chapter gives a preview of the
key area focused throughout the project such as connection admission control (CAC) and
QoS. How and by which means I am going to complete this project is presented in this
chapter including my aims and objectives of the project.
Chapter II: this chapter is the basic introduction to the platform on which I am doing my
project. This chapter presents the literature survey of the WiMax network and also discussed
the problem on which I am working throughout the project. A brief discussion of WiMax
Physical and MAC layer is presented in this chapter. The problem area is discussed as well as
the proposed solution of the problem at the end of the chapter.
Chapter III: this chapter is the first of three chapters that discusses the approaches made
towards connection admission control that is discussed in the later section project report. The
content of this chapter is presented as it is discussed in the dissertation guideline; introduction,
aims and objectives, approaches and methodologies, explanation of the process, results
obtained by the authors, authors conclusion and logical validation and methodology followed
by chapter summary.
Chapter IV: This chapter presents the second approach made towards connection admission
control for QoS provisioning in WiMax networks. This chapter is broken into section as it is
done in chapter III.
Chapter V: This chapter discusses the third approach made toward connection admission
control. The structure of the chapter is as same as chapter III and IV.
Connection admission control for real-time applications in WiMax networks
9
Chapter VI: A critical analysis of the three approaches that are been made by different
researcher that are presented in chapter III, IV and V is been presented in this chapter. By
focusing on various aspects of the problem area the solution presented by different researcher
is justified in this chapter. This chapter also presents any improvements of proposed solutions
and recommendation and possible future works.
Chapter VII: this chapter is the conclusion of the project. My personal and academic
achievements that I have gained while doing this project is been discussed here in this
chapter. I have tried to present my personal recommendation and opinion on the project in this
chapter.
Appendix A is been presented as it is recommended in this dissertation guideline. A scientific
article written in the form and format of a scientific journal is been presented in appendix A.
Appendix B contains the dissertation proposal report that was submitted to the tutors as a
form of Course work 2 of CCP 155N module prior to starting the Communication and
Dissertation Module. Appendix C presents the project plan.
All the reference used throughout this report is valid and they are presented by follow the
Vancouver system.
Connection admission control for real-time applications in WiMax networks
10
CHAPTER II
WIMAX OVERVIEW AND PROBLEM IDENTIFICATION
The purpose of this chapter is to produce an executive summary of the WiMax networks. This
chapter provides a summary of IEEE 802.16 group activities and its relationship with WiMax
networks. Some features of WiMax are discussed in this chapter and I have focused on the
technological side of WiMax by describing Physical and MAC-layer characteristics of
WiMax. A simplified version of quality of service (QoS) in WiMax network is also been
presented.
2.1 Background study of IEEE 802.16 and WiMax
WiMax (Worldwide Interoperability for Microwave Access) is defined as an Institute of
Electrical and Electronics Engineers (IEEE) telecommunication standard designated 802.16-
2004 for fixed wireless application and 802.16e-2005 for mobile wireless application. The
name Wi-Max was created by the Wi-Max forum which was formed in June 2001. From the
start till now it has emerged as a promising telecommunication technology. IEEE 802.16 was
first published in 2001 which was operating in 10 GHz-66 GHz frequency band. In 2003
IEEE 802.16a was introduced that provide some additional physical layer application for this
2 GHz-11 GHz frequency band. Later on 2004 these two standards 802.16 and 802.16a was
revised and declared as IEEE 802.16-2004 for fixed wireless application. IEEE 802.16e-2005
was published in 2005 for mobile wireless application. This newer version of WiMax was just
an amendment of IEEE 802.16-2004 standard that just added the mobility support. It has the
capability to work on both Lines Of Sight (LOS) and Non Line of sight (NLOS) condition. It
Connection admission control for real-time applications in WiMax networks
11
has the potentiality to replace current telecommunication infrastructure because the features
available with it.
Table 2.1 Basic Data in IEEE 802.16 Standards [3].
802.16 802.16-2004 802.16e-2005Status Completed December
2001Completed June 2004 Completed December
2005
Frequency Band 10 GHz - 66 GHz 2 GHz - 11GHz 2GHz – 11 GHz for fixed
2 GHz – 6 GHz for mobile applications
Applications Fixed LOS Fixed NLOS Fixed and mobile NLOSMAC architecture
Point-to-multipoint, mesh
Point-to-multipoint, mesh
Point-to-multipoint, mesh
ModulationQPSK, 16 QAM, 64 QAM
QPSK, 16 QAM, 64 QAM
QPSK, 16 QAM, 64 QAM
Multiplexing Burst TDM/TDMA Burst TDM/TDMA/OFDMA
Burst TDM/TDMA/OFDMA
Duplexing TDD and FDD TDD and FDD TDD and FDDTransmissionScheme
Single carrier only Single carrier, 256 OFDM or 2048 OFDM
Single carrier, 256 OFDM or scalable OFDM with 128, 512, 1024, 2048 subscriber
Channel bandwidths
20MHz, 25 MHz, 28 MHz
1.75 MHz, 3.5 MHz, 7 MHz, 14 MHz, 1.25 MHz, 5 MHz, 10 MHz, 15 MHz, 8.75 MHz
1.75 MHz, 3.5 MHz, 7 MHz, 14 MHz, 1.25 MHz, 5 MHz, 10 MHz, 15 MHz, 8.75 MHz
Gross data rate 32 Mbps – 134.4 Mbps
1 Mbps - 75 Mbps 1 Mbps - 75 Mbps
Air – interface designation
WirelessMAN-SC WirelessMan-SCa WirelessMan-OFDMWirelessMan-OFDMAWirelessHUMAN
WirelessMan-SCa WirelessMan-OFDMWirelessMan-OFDMAWirelessHUMAN
WiMax implementation
None 256 – OFDM as fixed WiMax
Scalable OFDMA as Mobile WiMax
2.2 WiMax Topologies
According to IEEE 802.16 standard WiMax can have two possible network topologies. Point-
to-Multipoint (PMP) topology and Mesh topology.
Connection admission control for real-time applications in WiMax networks
12
Point-to-Multipoint topology: PMP can be defined as a centralized topology where
the Base Station (BS) is the centre of the total system. The traffic in PMP mode may take
place only between a BS and its Subscriber Stations (SS).
Mesh Topology: Mesh topology is not centralized and the traffic in Mesh mode can
be routed through other SSs until the BS and can even take place only between SSs [2]. Each
station creates its own communication with other station in the network. The reach of BS is
much greater and it depends on the number of nodes [2].
Figure 2 Illustration of WiMax network in (a) PMP and (b) Mesh topology [1]
2.3 WiMax Protocol Layers
WiMax, the IEEE 802.16 Broadband Wireless Access standard applies the OSI network
model which is mostly used to describe the different aspects of a network technology [2]. The
WiMax PHY and MAC layer standard described by the IEEE 802.16 applies on the last two
layer of the OSI network model. But the data link layer of OSI reference model is been split
into two parts by the IEEE 802.16 standard, Medium Access Control (MAC) and Logical
Link Control (LLC) layer[2].
Connection admission control for real-time applications in WiMax networks
13
Figure 3 Seven layer OSI reference model, In WiMax only the two first layers are defined
[2]
In general the basic protocol architecture of IEEE 802.16 standard is defined in the figure 3.
From the figure it can be seen that, a common media access control (MAC) is working on top
of the PHY layer [1]. The difference between the physical layer and the MAC layer is
accommodated by the Transmission Convergence Sublayer. The MAC layer is divided into
three sublayer security/privacy sublayer, MAC Common Part Sublayer (MAC CPS) and
Convergence Sublayer (CS) [1].
Connection admission control for real-time applications in WiMax networks
14
Figure 4 IEEE 802.16 protocol architecture [1]
2.3.1 WiMax Physical LayerThe physical layer which is based on orthogonal frequency division multiplexing (OFDM) is
responsible for the establishment of physical connection between peering sides in both
direction uplink and downlink. Physical layer is also responsible for transmission of the bit
sequence [2]. The physical layer also defines the type of signal used, kind of modulation and
demodulation, the transmission power and it also defines the physical interfaces [2]. In IEEE
802.16 standard, five physical interfaces are been defined each performing in different
frequency range, different section in the IEEE 802.16 standard and each has different MAC
options. These interfaces were proposed based on the frequency range, Duplexing method
they use. Table 2.2 summarises the interfaces provided in the WiMax physical layer.
Connection admission control for real-time applications in WiMax networks
15
Table 2.2 the five physical interfaces defined in the IEEE 802.16 standard [2]
Designation Frequency Band
Section in the Standard
Duplexing MAC options
WirelessMAN-SC
10 – 66 GHz (LOS)
8.1TDD and FDD
WirelessMAN-SCa
Below 11 GHz (NLOS) ;Licensed
8.2
TDD and FDD
AAS (6.3.7.6), ARQ(6.3.4), STC(8.2.1.4.3), mobility
WirelessMAN-OFDM
Below 11 GHz ;Licensed
8.3
TDD and FDD
AAS (6.3.7.6), ARQ(6.3.4), STC(8.3.8), mesh (6.3.6.6), mobility
WirelessMAN-OFDFMA
Below 11 GHz ;Licensed
8.4
TDD and FDD
AAS (6.3.7.6), ARQ(6.3.4), HARQ (6.3.17) STC(8.4.8), mobility
WirelessHUMAN Below 11 GHz ;License exempt
8.5 (in addition to 8.2, 8.3, 8.4)
TDD only
AAS (6.3.7.6), ARQ(6.3.4), STC(8.4.8), mesh (6.3.6.6)
2.3.2 WiMax MAC layer
The MAC layer in the WiMax architecture manages the radio resources in an efficient way.
The main task of the MAC layer is to provide an effective communication link between the
higher transport layer and the physical layer [3]. The MAC protocol is connection oriented
and centralized [1]. MAC layer takes packets from the upper layer for transmit over the air by
organizing the packets into MAC Protocol Data Unite (MPDU). These higher layer packets
are called MAC Service Data Unite (MSDU). This MAC PDU is received as a PSDU
(physical SDU) by the physical layer [2].
Connection admission control for real-time applications in WiMax networks
16
Figure 5 General format of MAC PDU [2].
2.3.2.1 Convergence Sublayer
The convergence sublayer (CS) was included into MAC design of IEEE 802.16- 2004 and
IEEE 802.16e – 2005 standard [3]. The convergence layer is there so that it can accommodate
a variety of high layer protocols such as ATM, TDM voice, Ethernet, IP and many other
known protocols [3]. The convergence sublayer uses the services that are provided by the
MAC common part sublayer (MAC CPS) via the MAC Service Access Point (MAC SAP).
The functions provided by the convergence sublayer are as follows: [2]
Accepting higher layer PDUs from the higher layer.
Classifying and mapping the MSDUs into appropriate CIDs (Connection Identifier).
Processing the higher layer PDUs based on classification.
Delivering CS PDUs to the appropriate MAC SAP and receiving CS PDUs from peer
unity.
IEEE 802.16 standard defines two types of different specific convergence sublayer [figure 3].
This is used for service mapping to the MAC layer. The ATM convergence sublayer is
defined specifically for ATM traffic whereas the packet convergence sublayer is defined for
mapping protocol suits like IPv4, IPv6, Ethernet and Virtual LAN [1].
Connection admission control for real-time applications in WiMax networks
17
Figure 6 Protocol layers of IEEE 802.16 [2]
2.3.2.2 Medium Access Control Common Part Sublayer (MAC CPS)
The common part sublayer is responsible for the following:
Allocation of bandwidth
Establishment of connection
Connection maintenance between two sides
The common part sublayer provides the basic MAC rules and signalling mechanisms to
access the system [1]. In terms of bandwidth allocation the common part sublayer allocates
bandwidth on request from the subscriber stations (SS) and after the fulfilment of QoS
requirements.
2.3.2.3 Security/ Privacy Sublayer
One of the key parts in the WiMax protocol that maintains the security of WiMax networks.
The security sublayer provides authentication, secure key exchange, encryption and integrity
control across the system. Two main protocols are there to maintain the security.
Connection admission control for real-time applications in WiMax networks
18
Figure 7 Security Sublayer [2] [3]
An encapsulation protocol secures packet data across BWA network. It is basically a set of
cryptographic suites doing encryption and authentication algorithms and the rules, which
apply those algorithms to a MAC PDU payload.
Privacy & Key management (PKM) protocol for secure distribution of keying
data from BS to SS, Work in Security sub layer [2]. MS & BS synchronize keying
data through this PKM and BS also can enforce conditional access to network
services using protocol [3].
2.4 QoS Support in WiMax Network
A formal definition QoS are yet still to be defined but according to International
Telecommunication Union (ITU) recommendation E.800 in 1994 QoS was defined in 6 broad
components: Support, Operability, Accessibility, Retainability, Integrity and Security [4].
QoS mechanism is included in the Medium Access Control (MAC) layer of the WiMax
network. MAC layer is responsible to define service flows for IP based end-to-end QoS by
scheduling bandwidth to different users. MAC layer performs bandwidth allocation based on
the service requirements. Different applications require different levels of QoS which is been
accommodated into four service flows that will be discussed in later section of this paper [4].
Connection admission control for real-time applications in WiMax networks
19
Both the Base Stations (BS) and Subscriber Stations (SS) can create, delete and change these
service flows by using Dynamic Service Addition (DSA), Dynamic Service Deletion (DSD)
and Dynamic Service Change (DSC) messages [4].
Figure 8 QoS frame work (a) uplink mode (b) downlink mode [18]
In a PMP (Point-to-Multipoint) mode the BSs and the SSs act in a broadcast manner where all
the SSs receives the same transmission from the BSs. Transmissions from the SSs are directed
and coordinated to and by the BSs centrally. Data transmission in both downlink and uplink
occurs in separate time frames. Before the data transmission occurs there is a need of
scheduling to meet the QoS requirements.
As because the BSs controls and allocates the required bandwidth for each application to the
SSs on demand, a mechanism for bandwidth allocation exists. To support the QoS
requirements four types of service flows are been defined in WiMax network.
Connection admission control for real-time applications in WiMax networks
20
Unsolicited Grant Service (UGS): designed to support real-time applications with a
provision of strict delay requirements [1]. SSs request a fixed amount of bandwidth to
the BS. Bandwidth requesting occurs in a periodic basis on the connection setup phase.
There is no other request for bandwidth after this connection phase.
Real Time Polling Service (rtPS): designed to support real time applications with less
strict delay requirements. Supports variable bit rate (VBR) such as video traffic (e .g:
MPEG) and VoIP [1].
Non-real Time Polling Service (nrtPS): designed to support the applications that
does not have any kind of specific delay requirements [1]. In nrtPS service the BS
provides uplink request polls on a regular basis which is unicast [2].
Best Effort (BE): designed to support best effort traffic such as HTTP [16]. Uses
contention based bandwidth request [1]. No minimum service guarantees are required
for this kind of service flow [2].
Figure 9 QoS requirements for different applications [14]
Connection admission control for real-time applications in WiMax networks
21
Figure 10 QoS architecture in WiMax Network [18]
2.5 Problem Statement
Wireless networks now days are facing more and more challenges as the number of its users
are growing. The increasing demand from its users making it more and more concerned about
its capability, availability, reliability, integrity, quality, mobility and security. In order to
provide better quality of service (QoS) to its user’s wireless networks needs to make sure that,
it overcomes with all the obstacles to it. People are becoming more and more wireless
depended on their day to day work. Unlike wired networks wireless networks needs to be
more concerned about the available resources. Utilization of the network must be done in a
full and complete way. Provisioning better quality of service (QoS) in a high speed wireless
network is a very challenging issue. That’s why high speed wireless networks are still now a
big challenge to researchers. This project was chosen to face this challenge and to propose
something new to maintain the highest level of QoS for the WiMax networks.
Connection admission control for real-time applications in WiMax networks
22
2.6 Connection Admission Control (CAC)
Main distinguishable parameter of a wired and wireless connection is the availability of
resources. In a wireless network amount of available resources is limited. This limitation raise
the need of connection admission control (CAC) in order to make sure the wireless network
can guarantee the essential QoS for the admitted connection. Connection Admission Control
(CAC) alongside with other scheduling algorithms makes it possible for the WiMax to
support both real time traffic and non-real time traffic [9]. Connection admission control
algorithm’s objective is to maintain the QoS level by limiting the number of ongoing calls
through the WiMax network. Connection admission control operates when a new connection
or new service is being initiated. The IEEE 802.16 standard does not define any CAC or
scheduling algorithm for QoS provisioning it has to be defined specifically by the vendors
only.
2.6.1 Need of CAC in WiMax
WiMax is a new Broadband Wireless Access (BWA) technology which is becoming more and
more demandable. The growing need of broadband wireless access has increased the need of
high QoS with better network utilization. In order to have a balance between the high quality
of service (QoS) and efficient network utilization an efficient admission algorithm is must.
This kind of challenges is mitigated by using the connection admission control algorithm.
Different types of service have different types of QoS requirements. CAC maintains the QoS
level in WiMax network by accepting or declining the new connection as required.
Connection Admission Control (CAC) is used to decide whether an incoming connection will
be accepted or rejected through the use of connection control algorithm. In [16], the author
presented the need of connection admission control in the broadband wireless access (BWA).
Connection admission control for real-time applications in WiMax networks
23
All the research paper I have studied focuses on one common point for the need of connection
admission control and that is the availability of limited resources in wireless technology.
According to the author [16], “CAC is an algorithm that is built to manage radio/microwave
resources in order to adapt to traffic variations”
There are some common features in wireless network like multiple path propagation, channel
interference, handoff requirements and limited bandwidth which is not present in the wired
connections. Because of these, CAC in a wireless network is more complicated than a wired
network. The main objective of CAC in a wireless network is to guarantee QoS while
permitting a new connection without effecting other connections. CAC gives different priority
to different service applications to optimize the network revenue [16].
Figure 11 Basic Architecture of Admission control [10]
2.6.2 Purpose of Connection Admission Control in WiMax network
CAC plays a very important role in WiMax network. How and why CAC is important in
WiMax network can be seen from below:
Connection admission control for real-time applications in WiMax networks
24
CAC manages the radio resources of Wimax as it is a shared network
CAC regulates the new connections in order to ensure the highest level of QoS.
CAC ensures the minimum data transmission rate
CAC guarantee the minimum requirements for high quality of the connection.
2.6.3 Basic Components of Connection Admission Control (CAC)
Designing of a connection admission control mechanism comes up with some challenges such
as managing simultaneous calls. Upcoming new connections and soft handoff of continuing
connections have to be dealt as the first challenge of CAC mechanism. In terms of quality
assurance blocking the new connection instead of terminating a progress connection is more
preferred.
CAC makes it decision on three basic components [16] and these components are traffic
descriptor, admission criteria and network QoS state and flow information. Traffic descriptor
and QoS requirements are taken as an input to the admission control module. Based on the
input the decision is taken whether to admit the flow or to deny the flow if in any case the
QoS state is not met. Traffic descriptor is parameter based and it takes the source traffic
parameters as its decision components. Admission criteria sets up the rules which is been
proposed by the CAC algorithm [16].
Connection admission control for real-time applications in WiMax networks
25
Figure 12 Traditional CAC algorithm in Wireless Networks [16]
2.6.4 Parameter-based and Measurement-based Admission Control
In [10], two types of admission control is defined- (1) Parameter-based and (2) Measurement-
based
Parameter-based admission control works on a mechanism where worst case of delay or
packet loss gets computed. This computation is based on the traffic profile of existing and
new flows. Parameter-based connection admission is also called traffic descriptor approach.
In [10], the authors described this admission control mechanism as a consertive approach
because in this mechanism the ongoing flows may not always use the maximum amount of
resources as specified in the traffic descriptor. In this mechanism all flow information and
available network resources are stored in a specific database known as token bucket. The
admission control unit pop this information to calculate the worst-case delay then compare
Connection admission control for real-time applications in WiMax networks
26
with the required delay and take decision [10]. This kind of admission control is suitable for
applications that need guaranteed delay like video conferencing, VoIP etc.
In the circumstances like bursty traffic, parameter-based admission control can not describe
the traffic characteristics and lower the network utilization [10]. This leads the proposal for
measurement-based admission control by S.Jamin, P.B. Danzig, S. Shenker and L. Zhang in
1995 ( A Measuremetn-based Admission Control Algorithm for Integrated Services Packet
Networks). It is made up of two parts :( 1) measurement, that estimate the current network
load and (2) admission control based on estimated network load [10].
2.7 Summary
This chapter is an overview of the WiMax technology. I have presented the technological
aspects of WiMax in short in this chapter. A critical evaluation of two important layer of
WiMax is been presented in this chapter. The QoS parameters related to WiMax is been
discusses here in this chapter. I have also discussed the critical aspects related to connection
admission control in this chapter.
Connection admission control for real-time applications in WiMax networks
27
CHAPTER III
MEASUREMENT-BASED ADMISSION CONTROL
The purpose of this chapter to introduce some work that is been done by different researcher
so far on connection admission control to maintain the QoS level of WiMax network. At the
beginning of the chapter relevant paper is been introduced. I will focus on the working
process of the authors of the relevant papers and the results obtained by them.
3.1 Introduction to relevant papers
Measurement-based admission control is one of the proposed algorithms to maintain QoS in
WiMax networks. Different researcher proposed the measurement-based algorithm in
different schemes. In [16], the author proposed an algorithm that is based on delay factor and
throughput analysis as well as the utilization of the network resources. The method proposed
in [14] by R.Guuerin, H.Ahmadi, and M.Naghshineh is based on delay factor which is
measured on equivalent capacity process is different from the one proposed in [16]. Many
other researcher proposed admission algorithm like in [25] [17] which is based on network
load estimation to perform admission control. In [17] the authors define the CAC in two
different ways (1) by estimating the average number of free slots and (2) by tuning the
network load.
3.2 Aims and Objective
The aims and of the papers that is discussed in this chapter is to provide better QoS for real-
time applications such as VoIP, video streaming in WiMax network. And the desired level of
QoS is achieved by:
Connection admission control for real-time applications in WiMax networks
28
Analyzing the amount of traffic for every request
Analyzing the amount of bandwidth required for the request
Analyzing the amount of available bandwidth in hand
Analyzing the amount of current ongoing connection in the network
3.3 Approaches and methodology
The approaches and methodologies used in the relevant papers that are discussed in this
chapter are experimental based. The connection admission decision is been made on the basis
of available bandwidth and/or total number of ongoing connection. If the bandwidth required
for the new request is available or the new connection does not exceeded the maximum
amount of connection permitted in the network then the new connection will be admitted. For
real-time traffic in wireless network the QoS is been measured in terms of packet delay.
3.4 Components of measurement-based admission control
Figure 12 shows the basic components of the admission control scheme. A description of the
mechanism follows:
In order to perform flow establishment, a signalling protocol is required to communicate
resource reservation requests [4] from the origin node to the destination node. It is very
important that each request for a new flow characterises the nature of the flow. Because of the
varying nature of network traffic, most flows are characterized by their token bucket
parameters. The total admission control mechanism is controlled centrally be an admission
control unit.
The admission decision algorithm gathers the information about the estimated available
resources and the ongoing amount of traffic frequently from the system. The traffic estimator
Connection admission control for real-time applications in WiMax networks
29
provides the information needed to it [16]. Apart from giving the information of the amount
of traffic only the estimator provides the information about the characteristics of the traffic
also. The resource estimator keeps up updating the admission algorithm with the information
of remaining resources in the system [16].
Figure 13 Components of MBAC [16]
3.5 Explanation of the process
The author [16] proposed a scheme called Modified Largest Weighted Delay First (M-
LWDF) that ensures the feasibility of QoS provisioning in WiMax network. The M-LWDF
algorithm maintains the delay level of each traffic flow below the predefined value.
According to this algorithm the new connection will be denied if the packet delay experiences
the delay closer to the predefined value.
3.5.1 M-LWDF Scheduling Algorithm
M-WLDF proposed in [16] is a scheduling algorithm that supports better QoS for real-time
application in WiMax networks. The algorithm deals with the delay constrains in the network.
Connection admission control for real-time applications in WiMax networks
30
The algorithm provides two different types of QoS in terms of delay and throughout [16]. To
support the packet flow of real-time of applications must not exceed the predefined value by
the vendors. This condition is defined as, Pr (Wi > Ti) ≤ ξi where Wi is the packet delay for
each individual user, Ti and ξi are the delay bound and maximum probability of exceeding the
delay bound respectively. According to this algorithm, another form of QoS is achieved by
the average throughput Ri provided to each individual user i where the throughput provided to
each user must be equal to or greater than a specified value ri , Ri ≥ ri.
Figure 14 M-LWDF scheduler [16]
For example let us consider that there are N users in the system and assume that each user is
able to receive data flow. In order to maintain the QoS level for each flow it is important to
have the delay requirements of each flow stable. The M-LWDF algorithm choose user i at a
time t and for every user it choose, it adds a maximum value of delay bound γiWi(t)ri(t),
Connection admission control for real-time applications in WiMax networks
31
where Wi(t) is the packet delay for a queue i , ri(t)is the capacity of the channel and γi arbitrary
positive constant which can be different for each user[16] . This algorithm is open to the
vendor’s option as the delay requirements for different types of application can meet by
setting the value of γi. The M-LWDF scheduler use a time scale of arriving data packets for
each user. It keeps monitoring the current situation of the queue length.
3.5.2 Proposed Algorithm and Simulation Parameters
The algorithm proposed by the author [16] mainly works under the M-LWDF scheduling
policy. The scheme used here can be used for any type of traffic flow. But for this case the
author considers real-time traffic such as voice. The proposed algorithm is used to measure
the average packet delay for existing real-time users in the system.
The following diagram, figure: 15 is been used to measure the delay for real-time traffic.
From the diagram it can be seen that upon arrival of a new connection request the admission
control algorithm rejects the new request is the new connection does not match the predefine
delay bound of existing connections. A traffic priority scheme is been used in this algorithm
where the real-time applications receives higher priority than the non-real-time applications.
Connection admission control for real-time applications in WiMax networks
32
Figure 15 CAC algorithm for real-time traffic [16]
Connection admission control for real-time applications in WiMax networks
33
In order to lower the connection blocking or rejection provability the proposed algorithm uses
the resource reservation scheme for real-time applications. That means a certain portion of
resource is exclusively reserved for real-time traffics. The following is the proposed algorithm
proposed by the author in [16].
Admission Control Algorithm [16]
if NumofConReq > 0 then
if (MeasuredDelay < MaximumV oiceDelay) then
Accept the request
NumofConReq = NumofConReq - 1;
NumofExistCon = NumofExistCon + 1;
else
Deny the request
NumofConReq = NumofConReq - 1;
Blockconnections = Blockconnections + 1;
end if
end if
if NumofConReqnrt > 0 then
if (number of the free resources > Rs1) then
Accept the request
NumofConReqnrt = NumofConReqnrt - 1;
NumofExistConnrt = NumofExistConnrt + 1;
else
Deny the request
NumofConReqnrt = NumofConReqnrt - 1;
Connection admission control for real-time applications in WiMax networks
34
Blockconnectionsnrt = Blockconnectionsnrt + 1;
end if
end if
Execute the M-LWDF Scheduler Return MeasuredDelay and number of the free
resources.
Whereas;
NumofConReqt = the number of waiting real-time request
MeasuredDelay= the packet delay observed of existing real-time users
MaximumVoiceDelay = the delay bound
NumofExistCon = the number of existing connection in the system
Blockconnections= the number of blocking connections in the system
NumofConReqnrt= the number of waiting non-real-time connections
NumofExistConnrt= the number of existing non-real-time connections in the system
Blockconnectionsnrt= the number of blocking non real-time connections
The author [16] focuses on the packet delay and call blocking provability in his admission
control scheme. Effective simulation procedures were conducted by the author using
MATLAB to evaluate the proposed algorithm. The experiment was done by considering the
network in point-to-multipoint (PMP) mode which is composed of one single Base Station
(BS) and 20 Subscriber Stations (SSs). The MAC frame is of fixed length of 10ms and is
subdivided into uplink and downlink sub frame with equal length. Maximum packet delay is
150 ms. The following are the other related simulation parameters
Connection admission control for real-time applications in WiMax networks
35
Table 3.1: Simulation Parameters used in [16]
Parameter ValueBS power budget 20 WattSystem bandwidth 5MHzQueue size 106 bitsVoice packet size 66 *8 bitsPreamble 2 OFDM symbolFCH 1 OFDM symbolTTG 2 OFDM symbolMPDU header 6 byteMPDU CRC 4 byteDL-MAP 9 + 4 * n byten Number of transmitted bursts in each DL sub frameOFDM symbol duration 13.891 μ secRs1 6 msRs-Rs1 4 ms
3.6 Results obtained by the author
The results obtained by Randa Ibrahim Aljohani [16], are based on his mathematical analysis
and are founded by the simulation outcomes. The author analyses the channel gain as
exponentially distributed with in the range of 5 to 25 dB.
3.6.1 Packet Delay
Measured delay was obtained from the scheduler. As there was a predefined delay level, the
measured delay must be less then or equal to that predefined delay. Figure 16, presents the
results obtained by the author. It is notable that the packet delay increases as the number of
accepted connection increases thus increasing the network load. When the system load is low
(request arrival rate < 8 request) the packet delay is low whereas the delay increases rapidly at
> 8 connection request or ≤ 12 connection request. In case of heavy connection request the
packet delay rises sharply and here in this stage the CAC scheme take attempts to maintain
the packet delay requirement low by rejecting new connections.
Connection admission control for real-time applications in WiMax networks
36
Figure 16 Average packet delay vs. arrival rate of request [16]
3.6.2 Connection blocking probability
Figure 17 shows the connection blocking probability at different arrival rate of connections. It
is notable in the figure that connection blocking probability for real-time traffic is zero when
the network load is low. It is an indication of that, no new connection will be blocked at this
level. But as the network load increases the probability of connection blocking increases.
Figure 17 Connection blocking probability vs. arrival rate [16]
Connection admission control for real-time applications in WiMax networks
37
3.7 Conclusion by the Author
The author [16] presented an efficient M-LWDF scheduling algorithm that can support real-
time applications in WiMax networks. The author is convinced that the objectives of
admission control can be achieved with this algorithm. The author here though agreed that he
did not consider the traffic behaviour or not even considers the mobility and handoff schemes
but he is convinced that the proposed algorithm is an acceptable method to deploy in WiMax
network. The simulation results obtained by the author go according to the algorithm
proposed and therefore it is an acceptable CAC scheme.
More over in [17], Jani Lakkakorpi and Alexander Syenko conclude their proposed schemes
with a combined solution of measurement based and parameter based admission control.
They, in their research take the traffic arrival pattern into consideration where they stated that
the arrival pattern of the traffic was not according to the Poisson process every time.
According to their opinion if the traffic arrives in Poisson process then there is not much
difference between measurement-based admission control and parameter-based admission
control. However if not than in that cases the proposed parameter-based admission control as
a better method.
3.8 Logical Validation and Conclusion
All the approaches based on CAC that are discussed in this chapter focuses towards
measurement based admission control. The findings of the research that is been discussed in
this chapter was well discussed and mathematically proven. Measurement-based admission
control basically works by allocating bandwidth on demand. Means all the new requests are
allocated their required bandwidth on demand if the network has enough available resources
to deliver the desired level of QoS for that application. All the papers that is been discussed in
Connection admission control for real-time applications in WiMax networks
38
this chapter addresses the issue of QoS in WiMax network by considering the limitation of
resources. The papers discussed in this chapter does not present any discussion related to
mobility and handoff issues. There was no sign on connection rejection until and unless the
network load is high enough that is unable to support the new connection. What ever the
traffic arrival process is the network load goes high as the number of request for new
connection request goes high. However in each research paper there is a lot more scope for
more improvements.
3.9 Summary
This chapter discuss the first approach toward CAC in WiMax networks to achieve better
QoS. Two CAC scheme based on measurement-based CAC has been explained here in short.
A short discussion on the proposed algorithm has been presented in this chapter. I have also
discussed and logically validated the findings that is been mathematically proven the authors.
Connection admission control for real-time applications in WiMax networks
39
CHAPTER IV
ADAPTIVE CAC FOR QOS PROVISIONING IN WIMAX
4.1 Introduction to Relevant Papers
In [6], the authors Shafaq B. Chaudry, Ratan K. Guha has presented a connection admission
control scheme and a packet scheduling algorithm. According to the propose scheme the
CAC reserves an adaptive temporal channel bandwidth for subscribers while the scheduler
allocates slots to user based on application data rate. The proposed scheme works on priority
based where real time applications are given more priority than the non real time applications.
4.2 Aims and Objectives
The aims and objectives of the authors of the relevant paper are to assure maximum level of
QoS for real time applications.
4.3 Approaches and Methodologies
The approaches taken in the relevant paper is for the better solution in QoS provisioning in
WiMax networks. The authors, in [6] presented the existing QoS architecture in short to find
out the problem area more specifically. The proposed scheme prioritizes the real time
applications over non real time applications. The prioritization is done in accordance with the
QoS parameters that are defined by the service flow in IEEE 802.16 standard. The most
effective part of this proposed algorithm is that it also considers the hand off issues.
Connection admission control for real-time applications in WiMax networks
40
4.4 Explanation of the process
Different types of traffic class have different types of bandwidth requirements. The algorithm
proposed by the author defines minimum and maximum bandwidth for each types of traffic.
Guard channels are taken into consideration for admission policy. The authors of the paper
proposed some maximum and minimum bandwidth value for each type of traffic in order to
prevent starvation of low priority traffic like best effort (BE). The proposed CAC scheme is
been implemented by using fixed guard channel admission policy where new connections
beyond some predefined guard channel will be blocked [6]. This guard channel admission
policy is been used while considering new connection and handoff connection. The value of
the guard channel is been dynamically allocated and in terminology they are presented as thmin
and thmax where the value thmin and thmax is less then the total bandwidth B. dynamic adaption
of thmin and thmax depends on the arriving handoff request and termination of existing handoff
requests New connections which are beyond some specific guard channel are blocked [6]. But
in terms of hand off connections, they are always accepted as long as the system has available
capacity. The guard channel has minimum and maximum threshold values for handoff which
are thmin and thmax respectively where thmin and thmax is less than that of the total bandwidth B.
While considering the handoffs issue the value of thmin is a value equals to th, here th is some
value which is dynamically adjustable based on admission of arriving handoffs. The algorithm
proposed by the author in [6] is as follows:
th < thmin
At time epoch t,
forall(pending connections c) do
if(service class i of c is in {nrtPS,BE}) then
bi = bmin of class i
else
bi = bmax of class i
Connection admission control for real-time applications in WiMax networks
41
endif
if(type is handoff and service class is i) then
if( bi +b(t) <= B ) then
accept handoff
if(bi + b(t) < thmax) then
th <- min(thmax, (th + bi))
endif
else //no more capacity in B
reject handoff
endif
else// it is a new connection
if( bi + b(t) <= th ) then accept new
else reject new
endif
endif
endforall
forall(terminating connections c) do
if(type is handoff and service class is i) then
if(i is in {nrtPS,BE}) then
bi = bmin of class i
else
bi = bmin of class i
endif
if(th > thmin) then
th <- max(thmin, (th – bi))
endif
Connection admission control for real-time applications in WiMax networks
42
endif
endforall
At the base station the uplink scheduler calculates the OFDMA slots needed for the new
requests. The scheduler first assigns slots equals to its minimum bandwidth requirements. The
assigned bandwidth is allocated to ensure the fairness. In case of downlink connections, a
traffic classifier associates service flow IDS and QoS parameters at the MAC layer. The
SDUs are then converted to MAC PDUs after fragmentation and packing. The DL
(Downlink) scheduler makes the decision of choosing the packet to transmit. Deflect Round
Robin algorithm is used at each subscriber stations to schedule packets that are waiting in the
queues to be transmitted.
4.5 Results Obtained by the Authors
The results obtained by Shafaq B. Chaudhry, Ratan K. Guha are mathematical based and
obtained by simulation. The first approach was to find out the system behaviour within
different system load. The following diagrams shows the difference between the connection
blocking probability and handoff dropping probability in fixed and dynamic guard channel. It
is noticeable from the diagrams 18 and 19, that when the system load is low there is not much
difference between new connection blocking probabilities and handoff dropping probabilities
in both fixed and dynamic guard channel scheme
Connection admission control for real-time applications in WiMax networks
43
Figure 18 Comparison of new connection blocking probabilities between dynamic and fixed guard channel schemes [6]
The authors conducted further experiment to find out how the real time traffics are prioritized
over non real time traffics and how the dynamic schemes gives more priority to handoff over
new connections.
Figure 19 Blocking and dropping probability in Dynamic Guard Channel scheme [6]
Connection admission control for real-time applications in WiMax networks
44
While calculating delay for different class of traffics it is observed that delay increases as the
load of the network increases. And as the proposed scheme works on priority based, it is
observed that the class of traffic which was given less priority experience more delay. For
example in the following diagram BE traffic has the highest delay than real-time and non real-
time traffic.
Figure 20 Average delay among service classes [6]
4.6 Authors Conclusion
The authors, in [6]; concludes that they have proposed an architecture for providing QoS for
mobile WiMax networks by proposing adaptive connection admission control algorithm.
They conclude by mentioning that their proposed scheme considers both the new connections
and handoff connections to take admission decision. A priority based scheme is proposed
where handoff connections gets more priority over new connections.
4.7 Logical Validation and Conclusion
The authors of the papers discussed in this chapter proposed a new connection admission
control algorithm that not only works on bandwidth allocation scheme but it also considers
the handoff connections. A traditional CAC scheme mainly focuses on the allocation of
bandwidth. According to the conventional CAC scheme a new connection is accepted as long
as the system has the available resources but does not consider the existing connections in the
Connection admission control for real-time applications in WiMax networks
45
system. The relevant paper discussed in this chapter focuses on the issue of handoff
connections as well as bandwidth allocations. The proposed scheme of the relevant paper
allocates resources by differentiating between real time service and non real time service and
also gives priority to handoff connections over new connections. According to the proposed
scheme a new connection will not be accepted if the system has to compromise about the QoS
of ongoing connections or in case of handoff connections.
4.8 Summary
This chapter presents the second approach toward QoS provisioning by using CAC algorithm.
The approach presented in this chapter comes out of the traditional CAC scheme, where we
only think about bandwidth allocation to new request as long as it meets the QoS
requirements. This chapter brings on a new issue of consideration, like hand off connections.
Connection admission control for real-time applications in WiMax networks
46
CHAPTER V
STATISTICAL CONNECTION ADMISSION CONTROL
5.1 Introduction to Relevant Papers
Statistical connection admission control is another method of QoS provisioning in WiMax
networks. The authors in [9], Ju Yong Lee and Ki Baek Kim proposed an CAC algorithm
towards better QoS provisioning that has three different characteristics, (1) variation of air
capacity (2) mean and variance occupancy ratio of the frame and (3) a specific region that
determine the traffic overflow probability. In [24] Ke Yu , Xuan Wang, Songlin Sun, Lin
Zhang and Xiaofei Wu has also proposed a CAC algorithm which is more similar to that one
proposed in [9] but it omitted the mean and variance occupancy ratio of different types of
traffic.
5.2 Aims and Objectives
The aims and objectives of the authors related to the papers were to gain higher QoS as well
as to utilize the network more efficiently. The authors in [24] presented their findings in
different category. Findings of blocking probability, traffic overflow probability, traffic delay
and bandwidth usage are presented and discussed accordingly.
5.3 Approaches and methodology
The approaches discussed in this chapter by [24], Xuan Wang, Songlin Sun, Lin Zhang,
Xiaofei Wu is a mathematical and numerical approach toward CAC in WiMax network for
QoS assurance. The approach of the papers was to propose a statiscal CAC algorithm based
Connection admission control for real-time applications in WiMax networks
47
on Complete Sharing (CS) algorithm while considering the traffic overflow probability. The
authors discuss a simple model of air interface capacity in the physical layer. In [24] the
authors provide a Markov model to analyze the CAC performance by producing the results of
connection blocking probability, connection overflow probability and resource utilization
ratio. The authors in [9] and [24] presented their method in numerical and mathematical way.
The simulation method done was based on network simulator ns-2.
5.4 Explanation of the process
Since the real-time applications shows variability in the traffic stream the bandwidth needed
to support them with desired QoS is also variable. In order to deal with variable bit rate the
channel capacity need to vary also. According to the authors if the bandwidth needed is
greater than the air interface capacity then the QoS of the ongoing connections will be
degradable. So it is proposed that the overflow probability should be under a constraint which
is presented as
Pr [B ≥ C] ≤ ε [24]
Where B is the Bandwidth needed, C is the air interface capacity and ε is the overflow
probability ratio. The value of air capacity varies in terms of SS, Adaptive Modulation and
Coding (AMC). We can have a fixed value of air capacity if the SS is fixed and AMC level; is
fixed. Total air capacity can be affected by the positions of users in the cell and interference
of the other cells [9].
For a given time interval if there is M kinds of traffic in the system where each types of traffic
has N connections then the total bandwidth B of the system for that given interval will be
Connection admission control for real-time applications in WiMax networks
48
B = Ni
jij
M
i
M
i i BB [24]
Real-time applications consist of variable size of data packet and they arrive at different
interval as well as other applications. Like real-time traffic all other types of traffic have their
own minimal traffic rate. In wireless network we can see some similarity between the real-
time traffic and non-real-time traffic in terms of bit rate but the flow of packet makes the
actual difference between them. In [24], the proposed algorithm significantly notified the
issue of air interface capacity. The bit rate of real-time traffic and non-real-time traffic
changes due to the channel variation. According to the proposed algorithm in [24] there is
affixed value of air interface capacity ratio up to which the new connection request will be
accepted and ongoing connection will be dropped. Though there is no strict ratio value of air
interface capacity but the channel condition sometimes make some changes in the AMC level.
Changes in the AMC scheme make some changes in the bandwidth allocation scheme also.
According to the authors in [24] a new connection is accepted if and only if it satisfies the
requirements stated in the air interface capacity ratio.
To find out the efficiency of the proposed algorithm the authors simulate their network model
by implementing CAC in an ns-2 based IEEE 802.16 simulation platform. For variable and
constant bit rate traffic the authors used first come first served (FCFS) packet scheduling. The
traffic parameter used for this simulation is as follows
Figure 21 Traffic parameters used in [24]
The packet arrival rate for CBR traffic is 50 packets per second with the packet size of 0.16
Kbytes and the packet arrival rate of VBR traffic is 25 packets per second with minimal
Connection admission control for real-time applications in WiMax networks
49
packet size 0.5 Kbytes. The overflow probability value ε is 0.01 to 0.5 and the air interface
capacity used in the paper is defined by the IEEE 802.16 standard [9].
5.5 Results Obtained by the Authors
The results obtained by the authors [24] are based on mathematical analysis and numerical
solution. The author presented the traffic overflow probability, network utilization ratio, and
traffic delay and bandwidth usage specifically. The authors presented the blocking
probability, overflow probability and utilization ratio in different traffic intensity. Figure 22,
23 and 24 shows the results obtained for traffic blocking probability, traffic overflow
probability and utilization ratio respectively.
Figure 22 Blocking probability [24]
Figure 23 Overflow probability [24]
Figure 24 Utilization ratio [24]
Connection admission control for real-time applications in WiMax networks
50
The blocking probability is little higher when the traffic intensity is high this is because the
proposed algorithm considers the variability of the traffic and reserves more bandwidth. The
authors noticed that overflow probability increases as the traffic intensity increases. And for
utilization ratio the higher the VBR traffic intensity the higher the utilization ration. The
reason for that is the VBR traffic is allocated more bandwidth [24].
5.6 Conclusion by the Authors
In [24] the authors conclude that the variability of traffic and channel state affects the traffic
overflow and thus compromises the QoS of ongoing connections. The authors mentioned that
by applying the CAC algorithm proposed by them can help to reduce the traffic overflow. But
there is some limitation with this proposed algorithm as it follows the Gaussian process
approximation and the Gaussian process has some limitation of its own.
5.7 Logical Validation and Conclusion
The authors in [24] researching on statistical admission control takes into account one
important issue which was not taken by the researcher contribution discussed in chapter 3 and
chapter 4. The authors of the relevant papers [9] and [24] discussed in this chapter focused on
an important issue of air interface capacity. Two other important issues, traffic overflow and
traffic variability that impacts the QoS is been clearly discussed in Th relevant papers.
Mathematical validation proves the effect of air interface capacity ratio in QoS provisioning
in WiMax networks. Most of the admission control algorithms use traffic characteristics for
bandwidth allocation only for admission decision but the variation of traffic in terms of time
was neglected. Here in the proposed scheme by the authors [9] [24] clearly presented that the
characteristics of the traffic changes with the change in air interface capacity or channel
Connection admission control for real-time applications in WiMax networks
51
capacity changes. The theoretical and logical outcome of the proposed algorithm is bit similar
to that of the outcome discussed in chapter 3 and 4 but it clearly shows that air interface
capacity has some significant difference when we consider network utilization, connection
rejection or connection blocking thus affecting the QoS of the connection.
5.8 Summary
This chapter presents the third major approach towards connection admission control for
assuring quality of service (QoS) in WiMax networks. Based on the characteristics of wireless
networks and the limitation of wireless networks statistical admission control is proposed. The
scheme proposed in this proves the impact of air interface in WiMax network as well as how
to overcome the challenges of air interface is also been proposed.
Connection admission control for real-time applications in WiMax networks
52
CHAPTER VI
CRITICAL APPRAISAL, RECOMMENDATION AND
POSSIBLE FUTURE WORK
6.1 Analytical Review/ Critical Appraisal
A high speed broadband wireless access (BWA) technology like WiMax must deliver desired
level of QoS for every single application. But the principal drawback of wireless technology
is the limited amount of resources. To be the technology for today it has to overcome all the
challenging issues. Whatever the available resources are it must be ensured that desired level
of QoS is achieved for every applications. In order to make sure that the applications that are
accepted gets the QoS guarantee. Some researcher proposed CAC algorithm to ensure the
QoS in WiMax network.
Chapter III, IV and V discusses some proposed CAC algorithms proposed by some
researcher. All the researcher has tried to ensure the QoS as well as utilizing the network
resources properly. The problem area that was been introduced in this project was to ensure
QoS in WiMax network. The first group of researcher proposed measurement-based
admission control algorithm as the solution. The second group of researcher proposed
adaptive connection admission control algorithm while the third group of researcher proposed
statistical admission control algorithm. All the approaches made to the solution have its own
methodology and logical values.
Connection admission control for real-time applications in WiMax networks
53
In measurement based admission control algorithm is good to adopt as it does not need any
prior knowledge of traffic specification. Measurement based admission control measures the
actual traffic load and the QoS performance to make the decision. When there is a request for
new connection it checks the ongoing reserved amount of downlink and uplink bandwidth and
if the minimum reserve rate of traffic for the new request is below the corresponding limit
then the new connection request is accepted. The logic is simple but it comes with some
bottleneck also. the measurement based admission algorithm bears the risk of predicting the
resource requirements for the next request. It has one more drawback, which is the handoff
issue.
In adaptive admission control algorithm a new method is proposed. Though it does not have
the drawback of handoff issue like measurement based admission control it works as similar
as the measurement based admission control. It allocates the bandwidth dynamically and
prioritizes the traffic. Real-time applications are given more priority than other traffics. In
terms of new connection and handoff issue the proposed algorithm prioritizes the handoff
connection over the new connection request. And with this algorithm we can see less
connection blocking probability and less packet delay for real-time traffic than measurement
based admission algorithm. Figure 25 and 26 shows the difference.
Connection admission control for real-time applications in WiMax networks
54
Figure 25 Average delay in MBCAC [16]
Figure 26 Average delay in Adaptive CAC [6]
On the other hand statistical admission control contents the characteristics which are not
present in the adaptive and measurement based. With the change in the air channel it is
obvious that there capacity changes also. The changes in the air capacity effect the admission
decision. Taking the air capacity into account makes the proposed algorithm a better one to
apply.
Connection admission control for real-time applications in WiMax networks
55
6.2 Recommendation for Future Work
Connection admission control is a reasonable solution to ensure the quality of service (QoS)
in WiMax networks. Though all the proposed algorithms are mathematically proven by
simulation and numerical analysis but still there is lot of scope left for future work.
The connection admission mechanisms presented here in this project either ensuring QoS for
real-time traffics by blocking new connection request while there is shortage of bandwidth in
the system or by prioritizing the real-time traffic over other traffics.
In the measurement based admission control each new connections is getting accepted as long
as the system has the available bandwidth and the QoS requirements is been met. The
proposed algorithm discussed in chapter III ensures the quality of service (QoS) in terms of
delay and throughput where the packet delay does not exceeds the certain value which is
predefined. But in this proposed scheme , handoff issue and mobility was not considered.
Future work can be done on this two important issue.
Connection admission control based on adaptive CAC algorithm addresses the issue of
handoff connection. The bandwidth is allocated dynamically and to make sure the QoS level
of real-time traffic remains onto the desired level this algorithm gives priority to real-time
traffic over other traffics. But this kind of algorithm has the drawback of network utilization
issue. This is where we need some more future work.
In the statistical connection admission mechanism we consider some new issues. Last two
mechanism did not consider the issue of traffic variation with the variation of air capacity. But
statistical admission control does. For statistical admission algorithm the researcher did not
propose any scheduling algorithm for different types of traffic. The variation of traffic arrival
Connection admission control for real-time applications in WiMax networks
56
was measured as Gaussian process which is limited and do not support the traditional traffic
arrival process used in wireless network sector.
Each of the proposed mechanism are good for QoS assurance in WiMax network but still
there is plenty of future work left. And many researcher are currently working on it. To my
knowledge a combined algorithm of measurement and adaptive admission algorithm will be
more effective in provisioning QoS for real-time traffic in WiMax network. But to make my
personal recommendation on the problem area more logical and valid I need more in depth
knowledge and to implement my knowledge I need simulation tools which my university
failed to provide. Not only the absence of simulation tools but the shortage of time is an
important fact also.
6.3 Summary
This chapter critically comments and analyzes the approaches and methodologies towards the
solution of the problem. This chapter presents a analytical review of the works done by
different researcher by comparing the simulation results and outcome of their proposed
solution. This chapter also presents some recommendations for future work which is possible
to complete.
Connection admission control for real-time applications in WiMax networks
57
CHAPTER VII
CONCLUSIONS
WiMax itself is a new technology and CAC mechanism in WiMax to maintain QoS is newly
deployed. CAC was first meant to be used for ATM technology. But the mechanism of CAC
suits WiMax network very well as well. As WiMax needs to provide better service to the
applications like video conferencing, VoIP, online gaming etc there is a definite need of
maintaining better QoS. By managing the wireless resources more effectively CAC assure the
QoS for different applications in WiMax networks. This may be an issue to deploy CAC in
WiMax network and many researchers have proved this already. Different CAC algorithms
have been proposed by the researchers and have already been implemented.
This research was a analytical and logical approach to attain a suitable CAC algorithm for
real-time applications in WiMax network that ensures better QoS. The generic area of WiMax
was discussed followed by the identification of problem in chapter II. The problem area
identified was to ensure better QoS for real-time applications by using CAC algorithm.
The researches towards connection admission control algorithm for QoS provisioning in real-
time applications were categorized into three major approaches in this report. The approaches
were based on measurement based admission control, adaptive connection admission control
and statistical connection admission. How the approaches are implemented and what were the
outcome of their implementation were explained in this report followed by logical validation
and conclusions.
Connection admission control for real-time applications in WiMax networks
58
This project report is completed in a way which fulfill my aims and objectives that are stated
in chapter I. By discussing the three approaches of CAC towards QoS assurance in chapter III,
IV and V; I have gained some extra knowledge which fulfills my dissertation objectives. The
critical analysis and recommendation for future work section presents an idea of the
knowledge and experience I have learnt throughout the project.
While doing my research work on CAC for provisioning QoS in WiMax network I have
found some interesting findings, which is motivating me to do more work on this area. This
research paper has also provided some theoretical and technological background of the
standard and CAC. Doing future research on CAC to fulfill QoS constraints is more wide
open.
Wireless technologies are one of the fastest growing technologies in this decade. People all
over the world are getting more and more dependent to this technology for their day to day
life. Growing demands of this technology leading towards more and more research to make it
more effective and more useful. This research project was started with a view to contribute
something to the ongoing researches. If, my research do contribute a bit I will consider this as
a successful approach.
Connection admission control for real-time applications in WiMax networks
59
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Appendix A
SCIENTIFIC ARTICLE
Connection admission control for real-time applications in WiMax networks
65
Appendix B
DISSERTATION PROPOSAL REPORT
Connection admission control for real-time applications in WiMax networks
66
Appendix C
PROJECT PLAN