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FIXED AND MOBILE WIMAX
SEMINAR
SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE
AWARD OF THE DEGREE OF
MASTER OF TECHNOLOGY
(ELECTRONICS AND COMMUNICATION ENGINEERING)
SUBMITTED BY
NEETU GUPTA
PUNJAB TECHNICAL UNIVERSITY
JALANDHAR, INDIA
Dec, 2009
A SEMINAR REPORT ON
FIXED AND MOBILE WIMAX SUBMITTED IN PARTIAL FULFILLMENT FOR AWARD OF DEGREE OF
MASTER OF TECHNOLOGY
IN
ELECTRONICS AND COMMUNICATION ENGINEERING
BY
NEETU GUPTA
M-71304172
UNDER THE GUIDANCE OF
S. GURPADAM SINGH
(Asst. Prof. E.C.E)
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGG.
BEANT COLLEGE OF ENGINEERING AND TECHNOLOGY, GURDASPUR
Dec, 2009
CANDIDATE DECLARATION CERTIFICATE
I hereby certify that the work which is being presented in the seminar entitled “FIXED
AND MOBILE WIMAX” by “NEETU GUPTA” in partial fulfillment of requirements for
the award of degree of M.Tech. (Branch) submitted to Regional Centre, Punjab Technical
University, Department of Electronics and Communication Engineering at Beant College
of Engineering and Technology, Gurdaspur. Under PUNJAB TECHNICAL
UNIVERSITY, JALANDHAR is an authentic record of my own work carried out during a
period from August,2009 to Dec,2009 under the supervision of S. GURPADAM
SINGH( Asst Prof E.C.E).
Signature of the Student
This is to certify that the above statement made by the candidate is correct to the best of
my/our knowledge
Signature of the SUPERVISOR
The M-Tech viva-voce Examination of (NEETU GUPTA) has been held on__________
And accepted
Signature of Supervisor Signature of External Examiner
Signature of H.O.D.
ACKNOWLEDGMENT
I would like to express a deep sense of gratitude and thanks profusely to my seminar
guide S. Gurpadam Singh ( Asst. Prof. E.C.E Dept.) for his proper guidance and
valuable suggestions. Without the wise counsel and able guidance ,it would have been
impossible to complete the seminar in this manner.Their interest and constant
encouragement helped me in making the seminar a success.
The constant guidance received from Dr.Amarpal Singh Assistance Professor and H.O.D
department of Electronics and Communication Engineering BCET Gurdaspur has been of
great help in carrying out the present work.
I am thankful to all the faculty members who have directly or indirectly helped me in
completion the seminar.
Finally , I once again extend my sincere thanks to all whosoever have contributed in this
work.
vi
Neetu Gupta
M-71304172
vii
ABSTRACT
Within the last two decades, communication advances have reshaped the way we live our
daily lives. Wireless communications has grown from an obscure, unknown service to an
ubiquitous technology that serves almost half of the people on Earth. Whether we know it
or not, computers now play a dominant role in our daily activities, and the Internet has
completely reoriented the way people work, communicate, play, and learn.
However severe the changes in our lifestyle may seem to have been over the past few
years, the convergence of wireless with the Internet is about to unleash a change so
dramatic that soon wireless ubiquity will become as pervasive as paper and pen. WiMax—
which stands for Worldwide Interoperability for Microwave Access—is about to bring the
wireless and Internet revolutions to portable devices across the globe. Just as broadcast
television in the 1940’s and 1950’s changed the world of entertainment, advertising, and
our social fabric, WiMax is poised to broadcast the Internet throughout the world, and the
changes in our lives will be dramatic. In a few years, WiMax will provide the capabilities
of the Internet, without any wires, to every living room, portable computer, phone, and
handheld device.
In its simplest form, WiMax promises to deliver the Internet throughout the globe,
connecting the “last mile” of communications services for both developed and emerging
nations.
viii
INDEX
CHAPTER NO. TITLE PAGE NO.
Candidate declaration Certificate i
Acknowledgement ii
Abstract iii
Index viii
List of figures viii
List of tables viiii
List of Acronyms viiiii
CHAPTER-1 INTRODUCTION 1-6
1.1 Introduction 1
1.2 Necessity 3
1.3 Objectives 4
1.4 Organization 6
CHAPTER-2 LITERATURE SURVEY 7-11
2.1 Literature survey 7
CHAPTER-3 SYSTEM DEVELOPMENT 12-42
3.1. IEEE 802.16 12
3.2. IEEE 802.16a 14
3.3. WiMax vs. WLAN 15
3.4.WiMax VS. WiFi 15
3.5. HIPERMAN 16
3.6. WiMax 16
3.6.1. WiMax Forum 17
3.6.2. WiMAX Spectrum — Licensed and Unlicensed 19
3.7. Mesh Networks 21
3.8. Wireless Services 23
3.9. WiMax Infrastructure 24
ix
3.10. WiMax Network IP-Based Architecture 25
3.11. End-to-End WiMax Architecture 27
3.11.1 Support for Services and Applications 29
3.11.2 Interworking and Roaming 29
3.12. WiMax Protocol 30
3.13. Mobile WiMax 31
3.13.1 Introduction 31
3.13.2. Physical Layer Description 32
3.14 OFDMA Basics 33
3.15 TDD Frame Structure 34
3.16. MAC Layer Description 35
3.17. QoS Support 36
3.18. Mobility Management 37
3.19. Advanced Features of WiMax 40
3.19.1 Smart Antenna Technologies 40
3.19.2 Fractional Frequency Reuse 41
3.19.3 Multicast and Broadcast Service (MBS) 41
CHAPTER-4 PERFORMANCE ANALYSIS 43-50
4.1. Markets for WiMax 43
4.2 Current Status of WiMax 45
4.3 The WIMax Scenario 46
4.4.WiMax versus 3G and Wi-Fi 47
4.4.1 Other Comparable Systems 49
4.5 Competing technologies 49
CHAPTER- 5 CONCLUSIONS AND FUTURE SCOPE 51-57
5.1 Conclusion 51
5.2 Future scope 52
5.3 Applications of WiMax 53
REFERENCES 58-59
x
LISTOF FIGURES
FIGURE NO. TITLE PAGE NO.
Figure 1.1 Worldwide subscriber growth for mobile telephony 2
Figure 1.2 Objectives of WiMax 4
Figure 3.1 WiMax Overview. 17
Figure 3.2 Working of WiMax 23
Figure 3.3 Topologies in urban and rural areas 24
Figure 3.4 IEEE 802.16 Protocol Architecture 30
Figure 3.5 Basic Architecture of an OFDM System 33
Figure 3.6 Insertion of Cyclic Prefix (CP) 34
Figure 3.7 802.16a MAC Features 36
Figure 3.8 Mobile WiMax QoS Support 37
Figure 3.9 Fractional Frequency Reuse 41
Figure 4.1 Markets for WiMax 44
Figure 4.2 The WIMax Wireless Architecture 45
Figure 4.3 Gartner Hype Cycle for Wireless 45
Figure 4.4 WiMax Network scale 46
Figure 5.1 Substitute for the telephone company's T1/E1 or DS3 53
Figure 5.2 VoIP is the "killer app" for WiMax 54
Figure 5.3 IPTV and Video on Demand ON WiMax 55
Figure 5.4 Cellular network -mixture of wireless and PSTN 56
Figure 5.5 Mobile WiMax is mobile voice (cell phone) and data 57
Figure 5.6 WiMax as a mobile voice and data network 57
xi
LIST OF TABLES
TABLE NO. TITLE PAGE NO.
Table 3.1 Summary of 802.16 Standards 13
Table 3.2 WiMax Schedule 19
Table 3.3 WiMax, WLAN, and Bluetooth parameters 30
Table 4.1 Comparison of wireless technologies 48
LIST OF ACRONYMS
ARQ: Automatic Repeat Request. In case of errors in a transmitted packet or a
non received packet retransmission will occur.
ATM: Asynchronous Transfer Mode
BRAS: Broadband Remote Access Server
BS: Base Station
BWA: Broadband Wireless Access. Enabling high-speed broadband connections
the air instead of over wired (fixed) connections
CDMA: Code Division Multiple Access
CPE: Customer Premises Equipment
DHCP: Dynamic Host Configuration Protocol
DSL: Digital Subscriber Line
DSLAM: DSL Access Multiplexer
EIRP: Effective Isotropic Radiated Power
ETSI: European Telecommunications Standards Institute
EUL: Enhanced Up Link,
FDD: Frequency Division Duplex
GPRS: General Packet Radio Service
GSM: Global System for Mobile communication
HSPA: High Speed Packet Access, refers to both downlink (HSDPA) and uplink
(EUL/HSUPA)
HSDPA: High Speed Downlink Packet Access
HSUPA: High Speed Uplink Packet Access, same as EUL
IEEE: Institution for Electrical and Electronics Engineers. Standardization body.
IMT-2000: International Mobile Telecommunications-2000 (IMT-2000)
IMS: IP Multimedia Subsystem
IP: Internet Protocol
ITU: International Telecommunication Union.
LOS: Line-Of-Sight
xii
MAC: Medium Access Control
MAN: Metropolitan Area Network
MTBF: Mean Time Between Failure
xiii
NAT: Network Address Translation. Used to expand the addressing capabilities of
IPv4.
NLOS: Non-Line-Of-Sight
OFDM: Orthogonal Frequency Division Multiplexing
PDA: Personal Digital Assistant
PHY: Physical Layer
Prosumers: Professionals and enterprise users/subscribers
PSTN: Public Switched Telephone Network
QoS: Quality of Service
RF: Radio Frequency
SGSN: Serving GPRS Support Node
SIP: Simple Internet Protocol
SME: Small and Medium size Enterprises
SoHo: Small Office Home Office
SS: Subscriber Station
STC: Space-Time Codes
TCO: Total Cost of Ownership
TDD: Time Division Duplex
TDM: Time Division Multiplexing
TDMA: Time-Division Multiple Access
Users: Consumers, presumes, end-users and subscribers
VDSL: Very high bitrate DSL
VoIP: Voice over Internet Protocol technology enables users to transmit voice
calls via the Internet using packet-linked routes.
WCDMA: Wideband Code Division Multiple Access
WiFi: Wireless Fidelity, or Wireless Local Area Network, WLAN
WiMAX: World-wide interoperability for Microwave Access
WISP: Wireless Internet Service Provider
CHAPTER – 1
INTRODUCTION
1.1 Introduction
Broadband wireless sits at the confluence of two of the most remarkable growth stories of
the telecommunications industry in recent years. Both wireless and broadband have on
their own enjoyed rapid mass-market adoption. Wireless mobile services grew from 11
million subscribers worldwide in 1990 to more than 2 billion in 2005 [4]. During the same
period, the Internet grew from being a curious academic tool to having about a billion
users.
This staggering growth of the Internet is driving demand for higher-speed Internet-access
services, leading to a parallel growth in broadband adoption. In less than a decade,
broadband subscription worldwide has grown from virtually zero to over 200 million [5].
Will combining the convenience of wireless with the rich performance of broadband be
the next frontier for growth in the industry? Can such a combination be technically and
commercially viable? Can wireless deliver broadband applications and services that are of
interest to the end-users? Many industry observers believe so. Before we delve into
broadband wireless, let us review the state of broadband access today. Digital subscriber
line (DSL) technology, which delivers broadband over twisted-pair telephone wires, and
cable modem technology, which delivers over coaxial cable TV plant, is the predominant
mass-market broadband access technologies today. Both of these technologies typically
provide up to a few megabits per second of data to each user, and continuing advances are
making several tens of megabits per second possible. Since their initial deployment in the
late 1990s, these services have enjoyed considerable growth. The United States has more
than 50 million broadband subscribers, including more than half of home Internet users.
Worldwide, this number is more than 200 million today and is projected to grow to more
than 400 million by 2010 [5]. The availability of a wireless solution for broadband could
xiv
potentially accelerate this growth. What are the applications that drive this growth?
Broadband users worldwide are finding that it dramatically changes how we share
information, conduct business, and seek entertainment. Broadband access not only
provides faster Web surfing and quicker file downloads but also enables several
2
multimedia applications, such as real-time audio and video streaming, multimedia
conferencing, and interactive gaming. Broadband connections are also being used for
voice telephony using voice-over-Internet Protocol (VoIP) technology.
Figure 1.1 Worldwide subscriber growth 1990–2006 for mobile telephony, Internet
usage, and broadband access
More advanced broadband access systems, such as fiber-to-the-home (FTTH) and very
high data rate digital subscriber loop (VDSL), enable such applications as entertainment-
quality video, including high-definition TV (HDTV) and video on demand (VoD). As the
broadband market continues to grow, several new applications are likely to emerge, and it
is difficult to predict which ones will succeed in the future.
So what is broadband wireless? Broadband wireless is about bringing the broadband
experience to a wireless context, which offers users certain unique benefits and
convenience. There are two fundamentally different types of broadband wireless services.
The first type attempts to provide a set of services similar to that of the traditional fixed-
line broadband but using wireless as the medium of transmission. This type, called fixed
wireless broadband, can be thought of as a competitive alternative to DSL or cable
modem. The second type of broadband wireless, called mobile broadband, offers the
additional functionality of portability, nomadicity,1 and mobility.
3
Mobile broadband attempts to bring broadband applications to new user experience
scenarios and hence can offer the end user a very different value proposition. WiMax
(worldwide interoperability for microwave access) technology,
1.2 Necessity
In many parts of the world, existing fixed-line carriers that do not own cellular, PCS, or
3G spectrums could turn to WiMax for provisioning mobility services. As the industry
moves along the path of quadruple-play service bundles—voice, data, video, and mobility
—some service providers that do not have a mobility component in their portfolios—cable
operators, satellite companies, and incumbent phone companies—are likely to find
WiMax attractive[1]. For many of these companies, having a mobility plan will be not
only a new revenue opportunity but also a defensive play to mitigate churn by enhancing
the value of their product set.
Existing mobile operators are less likely to adopt WiMax and more likely to continue
along the path of 3G evolution for higher data rate capabilities. There may be scenarios,
however, in which traditional mobile operators may deploy WiMax as an overlay solution
to provide even higher data rates in targeted urban centers or metro zones. In addition to
higher-speed Internet access, mobile WiMax can be used to provide voiceover- IP services
in the future. The low-latency design of mobile WiMax makes it possible to deliver VoIP
services effectively. VoIP technologies may also be leveraged to provide innovative new
services, such as voice chatting, push-to-talk, and multimedia chatting. New and existing
operators may also attempt to use WiMax to offer differentiated personal broadband
services, such as mobile entertainment.
The flexible channel bandwidths and multiple levels of quality-of-service (QoS) support
may allow WiMax to be used by service providers for differentiated high-bandwidth and
low-latency entertainment applications. For example, WiMax could be embedded into a
portable gaming device for use in a fixed and mobile environment for interactive gaming.
Other examples would be streaming audio services delivered to MP3 players and video
services delivered to portable media players. As traditional telephone companies move
into the entertainment area with IP-TV (Internet Protocol television), portable WiMAX
could be used as a solution to extend applications and content beyond the home.
4
1.3 Objectives
The WiMax standard has been developed with many objectives in mind. These are
summarized below:
Fig 1.2 Objectives of WiMax
Flexible Architecture: WiMax supports several system architectures, including
Point-to-Point, Point-to-Multipoint, and ubiquitous coverage. The WiMax MAC
(Media Access Control) supports Point-to-Multipoint and ubiquitous service by
scheduling a time slot for each Subscriber Station (SS). If there is only one SS in
the network, the WiMax Base Station (BS) will communicate with the SS on a
Point-to-Point basis. A BS in a Point-to-Point configuration may use a narrower
beam antenna to cover longer distances.
High Security: WiMax supports AES (Advanced Encryption Standard) and
3DES (Triple DES, where DES is the Data Encryption Standard). By encrypting
the links between the BS and the SS, WiMax provides subscribers with privacy
(against eavesdropping) and security across the broadband wireless interface.
Security also provides operators with strong protection against theft of service.
WiMax also has built-in VLAN support, which provides protection for data that is
being transmitted by different users on the same BS.
Quick Deployment: Compared with the deployment of wired solutions, WiMax
requires little or no external plant construction. For example, excavation to support
the trenching of cables is not required. Operators that have obtained licenses to use
5
one of the licensed bands, or that plan to use one of the unlicensed bands, do not need
to submit further applications to the Government. Once the antenna and equipment are
installed and powered, WiMax is ready for service. In most cases, deployment of
WiMax can be completed in a matter of hours, compared with months for other
solutions.
Multi-Level Service: The manner in which QoS is delivered is generally based
on the Service Level Agreement (SLA) between the service provider and the end-
user. Further, one service provider can offer different SLA s to different
subscribers, or even to different users on the same SS.
Interoperability: WiMax is based on international, vendor-neutral standards,
which make it easier for end-users to transport and use their SS at different
locations, or with different service providers. Interoperability protects the early
investment of an operator since it can select equipment from different equipment
vendors, and it will continue to drive the costs of equipment down as a result of
mass adoption.
Portability: As with current cellular systems, once the WiMax SS is powered
up, it identifies itself, determines the characteristics of the link with the BS, as long
as the SS is registered in the system database, and then negotiates its transmission
characteristics accordingly.
Mobility: The IEEE 802.16e amendment has added key features in support of
mobility. Improvements have been made to the OFDM and OFDMA physical
layers to support devices and services in a mobile environment. These
improvements, which include Scaleable OFDMA, MIMO, and support for
idle/sleep mode and hand-off, will allow full mobility at speeds up to 160 km/hr.
Cost-effective: WiMax is based on an open, international standard. Mass
adoption of the standard, and the use of low-cost, mass-produced chipsets, will
drive costs down dramatically, and the resultant competitive pricing will provide
considerable cost savings for service providers and end-users.
Wider Coverage: WiMax dynamically supports multiple modulation levels,
including BPSK, QPSK, 16-QAM, and 64-QAM. When equipped with a high-
power amplifier and operating with a low-level modulation (BPSK or QPSK, for
6
example),WiMax systems are able to cover a large geographic area when the path
between the BS and the SS is unobstructed.
Non-Line-of-Sight Operation: NLOS usually refers to a radio path with its
first Fresnel zone completely blocked. WiMax is based on OFDM technology,
which has the inherent capability of handling NLOS environments. This capability
helps WiMax products deliver broad bandwidth in a NLOS environment, which
other wireless product cannot do.
High Capacity: Using higher modulation (64-QAM) and channel
bandwidth(currently 7 MHz, with planned evolution towards the full bandwidth
specified in the standards), WiMax systems can provide significant
1.4 Organization
The report is organized into five chapters.
Chapter 1 Deals with the introduction part of the report. It provides the
background information necessary for understanding WiMax. Provides a brief
introduction of broadband wireless, necessity of WiMax & its objectives.
Chapter 2 Deals with literature review of WiMax (related information available in
standard books, journals ,internet websites etc.)
Chapter 3 Deals with the System development of WiMax . For example IEEE
802.16, IEEE 802.16a, WiMax vs. WLAN, WiMax Vs. WiFi, HIPERMAN, Mesh
Networks, Wireless Services, WiMax Infrastructure, End-to-End WiMax
Architecture, WiMax Protocol, Mobile WiMax and Advanced Features of WiMax.
Chapter 4 Deals with the Performance Analysis of WiMax .This chapter shows
Markets for WiMax, Current Status of WiMax, The WiMax Scenario, and WiMax
versus 3G and Wi-Fi & Competing technologies.
Chapter 5 Deals with the Conclusion , future scope & Applications of WiMax
CHAPTER - 2
LITERATURE SURVEY
Zakhia Abichar, Yanlin Peng, and J. Morris Chang in 2006 shows WiMax:
The Emergence of Wireless Broadband The much-anticipated technology of
WIMax,the Worldwide Interoperability for Microwave Access, aims to provide
business and consumer wireless broadband services on the scale of the
Metropolitan Area Network (MAN).WiMax will bring a standards- based
technology to a sector that otherwise depended on proprietary solutions.The
technology has a target range of up to 31 miles and a target transmission rate
exceeding 100 Mbps and is expected to challenge DSL and T1 lines (both
expensive technologies to deploy and maintain) especially in emerging markets.
Dusit Niyato and Ekram Hossain in 2007 shows Integration of WiMax and
WiFi Broadband wireless access networks based on WiMax can provide backhaul
support for mobile WiFi hotspots. We consider an integrated WiMax/WiFi
network for such an application where the licensed WiMax spectrum is shared by
the WiFi access points/routers to provide Internet connectivity to mobile WiFi
users. The WiMax backbone network and WiFi hotspots are operated by different
service providers. Issues such as protocol adaptation, quality of service support,
and pricing for bandwidth sharing that are related to integration of these networks
are discussed. In addition, they propose a model for optimal pricing for bandwidth
sharing in an integrated WiMax/WiFi network
Chizu Fukao Jun in 2007 Study on the Detection Scheme of WiMax signal for
DAA Operation in MB-OFDM. In the first, by comparing the power 1-3 of the
WiMax signal derived from the FFT outputs of the MB-OFDM receiver with the
background noise, power detection scheme is performed. And using the central
limit L theorem, Correlation detection comparing power detection scheme. It was
confirmed that this scheme has much better performance than the power detection
scheme under low signal to noise ratio situation. Therefore, it references is
considered that the use of the guard interval information "Ultra-Wide Bandwidth
7
Time of WiMax signal is very effective for the detection of the Hopping Spread-
Spectrum Impulse Radio for Wireless Multiple-Access Communications signal
Kejie Lu and Yi Qian in 2007 shows a Secure and Service-Oriented Network
Control Framework for WiMax Networks, Worldwide Interoperability for
Microwave Access, is an emerging wireless communication system that can
provide broadband access with large-scale coverage. As a cost-effective solution,
multihop communication is becoming more and more important to WiMax
systems. To successfully deploy multihop WiMax networks, security is one of the
major challenges that must be addressed. Another crucial issue is how to support
different services and applications in WiMax networks. Since WiMax is a
relatively new standard, very little work has been presented in the literature. In this
article we propose a secure and service-oriented network control framework for
WiMax networks. In the design of this framework we consider both the security
requirements of the communications and the requirements of potential WiMax
applications that have not been fully addressed previously in the network layer
design. The proposed framework consists of two basic components: a service-
aware control framework and a unified routing scheme. Besides the design of the
framework, we further study a number of key enabling technologies that are
important to a practical WiMax network. Our study can provide a guideline for the
design of a more secure and practical WiMax network.
A Joon Ho Park, Mingji Ban in 2008 Designed Mobile WiMax System for
Military Applications and Its Performance in Fading Channels The IEEE
802.16e mobile WiMax system may not be quite suitable in some applications
where the uplink (UL) requires higher transmission rate than the downlink (DL). In
particular, many cases in military applications often require higher transmission
rate in the uplink. Proposal for a new mobile WiMax scheme that provides the DL
to UL ratio (DUR) to be 9:33 by modify the frame structure. Fading channels for
the modified mobile WiMax system are presented. They evaluate the bit error rate
(BER) performance and compare the throughput at the different DUR. The IEEE
802.16e mobile WiMax system may not be quite suitable in some applications
8
where the uplink (UL) requires higher transmission rate than the downlink (DL). In
particular, many cases in military applications often require higher transmission rate in
the uplink. In this paper, they propose a new mobile WiMax scheme that provides the
DL to UL ratio (DUR) to be 9:33 by modify the frame structure. Fading channels for
the modified mobile WiMax system are presented. They evaluate the bit error rate
(BER) performance and compare the throughput at the different DUR.
D. J. Shyy Jamie Mohamed in 2008 designed WIMax RF Planner Fixed
WiMax (IEEE 802.16d) is positioned as a wireless broadband alternative to the
traditional cable and Digital Subscriber Line (DSL) technologies. Mobile WiMax
(IEEE 802.16e) has been chosen as the 3G/4G technology by major mobile/cellular
service providers around the globe. Many Government organizations are also
interested in the WIiMax technologies. We have built a WIMax RF Planner, a
WiMax cell planning tool. The WiMax RF Planner incorporates all the standard
features of commercial RF planning tools with additional features tailored for
government requirements including: support of base station mobility as well as
interfacing to WiMax radios, OPNET and Google Earth.
Rajeshree Raut in 2008 presented Codec Design for WiMax System
Wireless communication is the fastest growing segment of the communication
industry. New services are being added and data is provided at higher bit rates to
the end users. With these advancements any communication system has to
critically consider data integrity. This requires, maintaining a lower bit error rate.
Present work focuses on the Broadcast Wireless Access standard named WiMax
(Worldwide Interoperability for Microwave Access). Possible options for
maintaining a lower bit error rate in WiMax System are worked out. In particular a
Novel Approach which uses a concatenation of RS and Turbo Codes for the Codec
design in The WiMax Communication System is presented. The paper also
discusses use of OQPSK Modulation Technique in place of the conventional
QPSK system, for performance improvement. The comparative simulation results
of existing WiMax System and the system using the novel approach are also
provided. These results are used to draw useful conclusions for reducing the bit
9
error rate.
Lang Wei-min in 2008 proposed a simple Key Management Scheme based on
WiMax WiMax security has two goals, one is to provide privacy across the
wireless network and the other is to provide access control to the network. The
security sub-layer of IEEE 802.16 employs an authenticated client/server key
management protocol in which the BS, the server, controls the distribution of
keying material to the client SS. This paper analyzes the physical layer threat and
MAC layer threat of WiMax, and then lists the security requirements of a WiMax
system. Furthermore, they propose the security architecture of WiMax and the key
management scheme from the aspects of Authorization Key (AK) exchange, TEK
exchange and AK management. In conclusion, this paper gives the security issues
and countermeasures in WiMax system.
Sassan Ahmadi in 2009 present an Overview of Next-Generation Mobile
WiMax Technology The IEEE 802.16m is designed to provide state of-the-art
mobile broadband wireless access in the next decade and to satisfy the growing
demand for advanced wireless WiMax profile are expected to be completed
by2011. Multihop relay architecture, multi-carrier operation, self-configuration,
advanced single user/ multi-user multi-antenna schemes and interference
mitigation techniques, enhanced multicast-broadcast service, increased VoIP
capacity, improved cell-edge user throughput, and support of vehicular speeds up
to 500 km/h, and so on are among the most prominent features that would make
IEEE 802.16m one of the most successful and advanced broadband wire time
applications and services.
Steven J. Vaughan in 2009 proposed Mobile WiMax The Next Wireless
Battleground The IEEE plans to adopt mobile WiMax 2.0—formally called IEEE
802.16m. The technology would offer data rates of 100 Mbps for mobile uses and
1 Gbps for fixed applications via enhanced MIMO technology. If adopted on
schedule, industry observers expect mobile WiMax 2.0 to appear in products by
2012
10
Jarno Pinola and Kostas Pentikousis in 2009 proposed IPTV over WiMax
with MIPv6 Handovers As the IPv4 unallocated address pool nears exhaustion,
an increasing number of IPv6 deployments is anticipated. In the domain of
mobility management research and development, Mobile IPv6 has long been
favored over Mobile IPv4. Nevertheless, although in principle WiMax supports
IPv6 in various configurations and requires MIPv6 for network-level mobility
management, in practice, vendors are actively deploying these capabilities only in
part. They provide a thorough review of the role of IPv6 and MIPv6 in WiMax
networks, surveying the work in relevant standardization bodies. The second
contribution of is a test bed evaluation of IPTV streaming over WiMax. They
employ two WiMax test beds deployed in Finland and Portugal, interconnected by
GEANT and Quantify MIPv6 performance in a real-time multimedia streaming
scenario over WiMax. Beyond demonstrating the feasibility of such a deployment,
their results indicate that WiMax can provide a viable option as both access and
backhauling technology.
Yue Li1 & Demetres Kouvatsos in 2009 shows Performance Modeling and
Bandwidth Management of WiMax Systems Worldwide Interpretability for
Microwave Access is a competitive connection oriented technology for
metropolitan broadband wireless access with very high data rate, large service
coverage and flexible quality of service (QoS). Due to the large number of
connections, the efficient bandwidth management and related channel allocation
for the uplink access in WiMax networks is a very challenging task of the medium
access control (MAC) protocol. In order to provide better bandwidth utilization
and network throughput, a cost-effective WiMax bandwidth management scheme
is devised, named as the WiMax partial sharing scheme (WPSS) and compared
against a simpler scheme, named as the WiMax complete sharing scheme (WCPS).
An analytic maximum entropy (ME) model is proposed for the cost-effective
performance evaluation of the two bandwidth management schemes associated
with networks with a large number of stations and/or the connections. In this
context, an open queuing network model (QNM) is devised,
11
CHAPTER 3
SYSTEM DEVELOPMENT
3.1. IEEE 802.16
The IEEE 802.16 Working Group is the IEEE group for wireless metropolitan area
network. The IEEE 802.16 standard defines the Wireless MAN (metropolitan area
network) air interface specification (officially known as the IEEE Wireless MAN
standard). This wireless broadband access standard could supply the missing link for the
“last mile” connection in wireless metropolitan area networks. Wireless broadband access
is set up like cellular systems, using base stations that service a radius of several
miles/kilometers.
Base stations do not necessarily have to reside on a tower. More often than not, the base
station antenna will be located on a rooftop of a tall building or other elevated structure
such as a grain silo or water tower. A customer premise unit, similar to a satellite TV
setup, is all it takes to connect the base station to a customer. The signal is then routed via
standard Ethernet cable either directly to a single computer, or to an 802.11hot spot or a
wired Ethernet LAN.
The IEEE 802.16 designed to operate in the 10-66 GHz spectrum and it specifies the
physical layer (PHY) and medium access control layer (MAC) of the air interface BWA
systems. At 10-66 GHz range, transmission requires Line-of-Sight (LOS).IEEE 802.16 is
working group number 16 of IEEE 802, specializing in point-to-multipoint broadband
wireless access.
The IEEE 802.16 standard provides the foundation for a wireless MAN industry.
However, the physical layer is not suitable for lower frequency applications where non-
line-of-sight (NLOS) operation is required [2]. For this reason, the IEEE published
802.16a standard to accommodate NLOS requirement in April 2003. The standard
operates in licensed and unlicensed frequencies between 2 GHz and 11 GHz, and it is an
extension of the IEEE 802.16standard.The IEEE 802.16 Working Group created a new
standard, commonly known as WiMax, for broadband wireless access at high speed and
low cost, which is easy to deploy, and which provides a scalable solution for extension of
a fiber-optic backbone.
WiMax base stations can offer greater wireless coverage of about 5 miles, with LOS (line
12
of sight) transmission within bandwidth of up to 70 Mbps.
WiMax is supported by the industry itself, including Intel, Dell, Motorola, Fujitsu, AT&T,
British Telecom, France Telecom, Reliance Infocomm, Siemens, Sify,Price Warehouse
Coopers and Tata Teleservices – forming an alliance called WiMax Forum. It represents
the next generation of wireless networking [3]. WiMAX original release the
802.16standard addressed applications in licensed bands in the 10 to 66 GHz frequency
range. Subsequent amendments have extended the 802.16 air interface standard to cover
non-line of sight (NLOS) applications in licensed and unlicensed bands in the sub 11 GHz
frequency range.
Filling the gap between Wireless LANs and wide area networks, WiMAX-compliant
systems will provide a cost-effective fixed wireless alternative to conventional wire-line
DSL and cable in areas where those technologies are readily available. And more
importantly the WiMAX technology can provide a cost-effective broadband access
solution in areas beyond the reach of DSL and cable. The ongoing evolution of IEEE
802.16 will expand the standard to address mobile applications thus enabling broadband
access directly to WiMAX-enabled portable devices ranging from smart phones and Pads
to notebook and laptop computers.
Table 3.1 Summary of 802.16 Standards
13
3.2. IEEE 802.16a
The IEEE 802.16a standard allows users to get broadband connectivity without needing
direct line of sight with the base station. The IEEE 802.16a specifies three air interface
specifications and these options provide vendors with the opportunity to customize their
product for different types of deployments. The three physical layer specifications in
802.16a are:
Wireless MAN-SC which uses a single carrier modulation format.
Wireless MAN-OFDM which uses orthogonal frequency division multiplexing
(OFDM) with 256 point Fast Fourier Transform (FFT). This modulation is
mandatory for license exempt bands.
Wireless MAN-OFDMA which uses orthogonal frequency division multiple access
(OFDMA) with a 2048 point FFT. Multiple accesses are provided by addressing a
subset of the multiple carriers to individual receivers.
In 1998, the IEEE (The Institute of Electrical and Electronics Engineers) began a
standards project to specify a point-to-multipoint broadband wireless access system
suitable for the delivery of data, voice, and video services to fixed customer sites. The
initial standard, designated IEEE 802.16, was developed for the higher microwave bands
(> 10 GHz) where line-of-sight between system antennas is required for reliable service.
Despite the availability of licensed spectrum for potential deployments, completion of the
standard in 2001 failed to have a significant impact; most vendors abandoned their
proprietary equipment and did not attempt to implement high-frequency multipoint
systems based on the 802.16 standard.
Factors beyond equipment cost (e.g., installation, roof rights, backhaul, spectrum costs)
were significant contributors to the poor economics of the high-frequency multipoint
systems. In early 2000, work on a low-frequency (<11 GHz) revision of the 802.16
standard was begun by the IEEE working group. This revision (designated 802.16a)
incorporated new radio link system options more suitable for low-frequency service while
maintaining most of the access control system specifications of the original standard
Completed in January 2000, the 802.16a standard included features supporting:
Non-line-of-sight service capability
Multiple radio modulation options (single carrier, OFDM)
Licensed and unlicensed band implementations
14
Versatile access control and QoS features, including TDM and packet services, advanced
security A corrected and modified version of 802.16a (designated 802.16-REVd) was
completed in June 2004. Initial WiMAX profiles are a subset of the 802.16-
REVdstandard. A mobile extension to the low-frequency 802.16 standard is now being
developed by the IEEE 802.16e working group. This extension will support delivery of
broadband data to a moving wireless terminal, such as a laptop computer with an
integrated WiMAX modem being used by a passenger on a commuter train. The WiMAX
Forum expects to endorse a mobile profile following completion of the 802.16e standard.
3.3. WiMax vs. WLAN
Unlike WLAN, WiMAX provides a media access control (MAC) layer that uses a grant
request mechanism to authorize the exchange of data. This feature allows better
exploitation of the radio resources, in particular with smart antennas, and independent
management of the traffic of every user. This simplifies the support of real-time and voice
applications.
One of the inhibitors to widespread deployment of WLAN was the poor security feature of
the first releases. WiMAX proposes the full range of security features to ensure secured
data exchange:
Terminal authentication by exchanging certificates to prevent rogue devices,
User authentication using the Extensible Authentication Protocol (EAP),
Data encryption using the Data Encryption Standard (DES) or Advanced
Encryption Standard (AES), both much more robust than the Wireless Equivalent
Privacy (WEP) initially used by WLAN. Furthermore, each service is encrypted
with its own security association and private keys.
3.4. WiMax VS. WiFi
WiMAX operates on the same general principles as WiFi -- it sends data from one
computer to another via radio signals. A computer (either a desktop or a laptop) equipped
with WiMAX would receive data from the WiMAX transmitting station, probably using
encrypted data keys to prevent unauthorized users from stealing access.
The fastest WiFi connection can transmit up to 54 megabits per second under optimal
conditions. WiMAX should be able to handle up to 70 megabits per second. Even once
that70 megabits is split up between several dozen businesses or a few hundred home users,
15
it will provide at least the equivalent of cable-modem transfer rates to each user.
The biggest difference isn't speed; it's distance. WiMAX outdistances WiFi by miles.
WiFi's range is about 100 feet (30 m). WiMAX will blanket a radius of 30 miles (50 km)
with wireless access. The increased range is due to the frequencies used and the power of
the transmitter. Of course, at that distance, terrain, weather and large buildings will act to
reduce the maximum range in some circumstances, but the potential is there to cover huge
tracts of land.
WiMax is not designed to clash with WiFi, but to coexist with it. WiMax coverage is
measured in square kilometers, while that of WiFi is measured in square meters. The
original WiMax standard (IEEE 802.16) proposes the usage of 10-66 GHz frequency
spectrum for the WiMax transmission, which is well above the WiFi range (up to 5GHz
maximum). But 802.16a added support for 2-11 GHz frequency also[4]. One WiMax base
station can be accessed by more than 60 users. WiMax can also provide broadcasting
services also. WiMax specifications also provides much better facilities than WiFi,
providing higher bandwidth and high data security by the use of enhanced encryption
schemes. WiMax can also provide service in both Line Of Sight (LOS) and Non-Line Of
Sight (NLOS) locations, but the range will vary accordingly.
WiMax will allow the interpenetration for broadband service provision of VoIP, video,
and internet access – simultaneously. WiMax can also work with existing mobile
networks. WiMax antennas can "share" a cell tower without compromising the function of
cellular arrays already in place.
3.5. Hiperman
The ETSI has created wireless MAN standard for frequency band between 2 GHz and
11GHz. The ETSI Hiperman standard was issued in Nov 2003. The ETSI works closely
with the IEEE 802.16 group and the HIPERMAN standard has essentially followed
802.16’s lead.
The Hiperman standard provides a wireless network communication in the 2 – 11 GHz
bands across Europe. The Hiperman working group utilizes the 256 point FFT OFDM
modulation scheme. It is one of the modulation schemes defined in the IEEE 802.16a
standard.
3.6. WiMax
Worldwide Interoperability for Microwave Access (WiMAX) is currently one of the
hottest technologies in wireless. The Institute of Electrical and Electronics Engineers
16
(IEEE) 802 committee, which sets networking standards such as Ethernet (802.3) and
WiFi (802.11), has published a set of standards that define WiMAX. IEEE 802.16-2004
(also known as Revision D) Was published in 2004 for fixed applications; 802.16
Revision E (which adds mobility) is duplicated in July 2005. The WiMAX Forum is an
industry body formed to promote the IEEE 802.16 standard and perform interoperability
testing. The WiMAX Forum has adopted certain profiles based on the 802.16 standards for
interoperability testing and “WiMAX certification”.
These operate in the 2.5GHz, 3.5GHz and 5.8GHz frequency bands, which typically are
licensed by various government authorities. WiMAX, is based on an RF technology called
Orthogonal Frequency Division Multiplexing (OFDM), which is a very effective means of
transferring data when carriers of width of 5MHz or greater can be used. Below 5MHz
carrier width, current CDMA based 3G systems are comparable to OFDM in terms of
performance.
WiMAX is a standard-based wireless technology that provides high throughput broadband
connections over long distance. WiMAX can be used for a number of applications,
including “last mile” broadband connections, hotspots and high-speed connectivity for
business customers. It provides wireless metropolitan area network (MAN) connectivity at
speeds up to
70 Mbps and the WiMAX base station on the average can cover between 5 to 10 km.
Figure 3.1. WiMAX Overview.
3.6.1. WiMax Forum
WiMax Forum is a non-profit corporation that was formed in April 2001 by equipment
17
and component suppliers to help to promote and certify the compatibility and
interoperability of Broadband Wireless Access (BWA) equipment. As of May 2004, there
are over 100 members of WiMax Forum. WiMax’s members, which include Air span,
Alcatel, Alvarion, Fujitsu, Intel, OFDM Forum, Proxim, Siemens, account for over 75
percent of sales in the 2 to 11 GHz BWA market.
The WiMax Forum (the Forum) is a coalition of wireless and computer industry
companies that has endorsed and is aggressively marketing the WiMax standard. A
principal purpose of the organization is to promote and certify compatibility and
interoperability of devices based on the various 802.16 specifications and to develop such
devices for the global marketplace.
The Forum believes that the adoption of industry standards will be a key factor in any
successful deployment of WiMax technology [7]. For example, one of the most significant
problems with WiFi initial deployment was the lack of any early industry standards. In the
early days of WiFi deployment, the marketplace was saturated with equipment well before
industry standards were adopted. As a result, equipment often lacked interoperability and
was expensive.
One of the purposes of the WiMax Forum is to create a single interoperable standard from
the IEEE and ETSI BWA standards. In order to create a single interoperable standard,
WiMax has decided to focus on the 256 FFT OFDM which is common between 802.16a
and HIPERMAN. WiMax has developed system profiles covering the popular licence-
exempted bands in 2.4 GHz and 5 GHz and other licensed bands in 2.3 GHz, 2.5 GHz and
3.5 GHz. At the moment, WiMax will focus its conformance and interoperability test
procedures on equipment that operates in 2.5 GHz and 3.5 GHz licensed bands and 5.8
GHz unlicensed band using 256 FFT OFDM modulation scheme. The flexible channel
plan from 1.5 MHz to 20 MHz per channel will be adopted by WiMax.
The WiMax Forum strategy has been formed in an attempt to promote high-volume,
worldwide adoption of WiMax equipment. Components of the WiMax Forum strategy
include:
Select a workable subset of the many allowed system profiles and variations in the
802.16standard
Develop a testing and certification process to validate that equipment submitted by
vendors conforms to “WiMax” certification requirements of standard compliance
18
and multi-vendor interoperabilit
Continue to support IEEE 802.16 standard updates and corrections, including the
current mobile enhancement project (802.16e)
The availability of a standard eliminates the need for the large investment by equipment
vendors required to develop and verify basic radio and access control systems from
scratch.
With volume, equipment costs are further lowered as component makers and system
integrators achieve manufacturing efficiencies. Service providers (and ultimately
consumers) benefit from the interoperability requirement, as multiple vendors compete for
business during initial system build-out, expansion, and evolutionary upgrades.
The WiMax Forum timeline (past and projected) for standard development, certification
testing, and availability of initial “WiMax” equipment is shown
Table3.2. WiMax Schedule
3.6.2. WiMax Spectrum — Licensed and Unlicensed
As with any other spectrum based technology, successful WiMAX deployment will
depend largely upon the availability and suitability of spectrum resources. For entities
providing wireless communications services, two sources of spectrum are available:
19
Licensed spectrum and
Unlicensed spectrum.
Licensed spectrum requires an authorization/license from the Commission, which offers
that individual user or “Licensee” the exclusive rights to operate on a specific frequency
(or frequencies) at a particular location or within a defined geographic area.
In contrast, unlicensed spectrum permits any user to access specific frequencies within any
geographic area inside the United States without prior Commission authorization. While
users of this spectrum do not have to apply for individual licenses or pay to use the
spectrum, they are still subject to certain rules. First, unlicensed users must not cause
interference to licensed users and must accept any interference they receive. Second, any
equipment that will be utilized on unlicensed spectrum must be approved in advance by
the Commission. Because of its broad operating range, licensed and unlicensed spectrum
options for WiMax technology are extensive. To take best advantage of the benefits
provided by WiMax systems, large block spectrum assignments are most desirable. This
enables systems to be deployed in TDD mode with large channel bandwidths, flexible
frequency re-use and with minimal spectral inefficiencies for guard-bands to facilitate
coexistence with adjacent operators.
Another key activity for the WiMax Forum is collaborating with standards and regulatory
bodies worldwide to promote the allocation of spectrum in the lower frequency bands (< 6
GHz) that is both application and technology neutral. Additionally, there is a major push
for greater harmonization in spectrum allocations so as to minimize the number equipment
variants required to cover worldwide
The initial system performance profiles that will be developed by the WiMax Forum for
the recently approved 802.16-2005 air interface standard are expected to be in the licensed
2.3 GHz, 2.5 GHz and 3.5 GHz frequency bands. The 2.3 GHz band has been allocated in
South Korea for WiBro services based on the Mobile WiMax technology[8].
With a 27 MHz block of spectrum assignment to each operator, this band will support a
TDD deployment with 3 channels per base station and a nominal channel bandwidth of
8.75 MHz. The 2.5 to 2.7 GHz band is already available for mobile and fixed wireless
services in the United States. This band is also currently underutilized and potentially
available in many countries throughout South America and Europe as well as some
countries in the Asia-Pacific region. The 3.5 GHz band is already allocated for fixed
20
wireless services in many countries worldwide and is also well-suited to WiMax solutions
for both fixed and mobile services.
3.7. Mesh Networks
The IEEE 802.16 WiMax standard provides a mechanism for creating multi-hop mesh,
which can be deployed as a high speed wide-area wireless network. Beyond just providing
a single last hop access to a broadband ISP, WiMax technology can be used for creating
wide-area wireless backhaul network. When a backhaul-based WiMax is deployed in
Mesh mode, it does not only increase the wireless coverage, but it also provides features
such as lower backhaul deployment cost, rapid deployment, and re configurability.
Various deployment scenarios include citywide wireless coverage, backhaul for
connecting 3G RNC (Radio Network Controller) with base stations, and others. In
addition to the single hop IEEE 802.16 PMP (point-to multipoint) operation, IEEE
802.16a standard defined the basic signaling flows and message formats to establish a
mesh network connection.
Subsequently, the Mesh mode specifications were integrated into the IEEE 802.16-2004
revision. Although single hop WiMax provides high flexibility to attain Quality of Service
in terms of data throughput, achieving the same in multi-hop WiMax mesh is challenging.
One of the major problems is dealing with the interference from transmission of the
neighboring WiMax nodes. Cross-layer design and optimization is known to improve the
performance of wireless communication and mobile networks. Interference in wireless
systems is one of the most significant factors that limit the network capacity and
scalability of wireless mesh networks. Consideration of interference conditions during
radio resource allocation and route formation processes impacts the design of concurrent
transmission schemes with better spectral utilization while limiting the mutual
interference.
A newly formed group within 802.16, the Mesh Ad Hoc committee, is investigating ways
to improve the coverage of base stations even more. Mesh networking allows data to hop
from point to point, circumventing obstacles such as hills[9] Only a small amount of
meshing is required to see a large improvement in the coverage of a single base station. If
this group’s proposal is accepted, they will become Task Force F and develop an 802.16f
standard.
21
In comparison to IEEE 802.11a/b/g based mesh network, the 802.16-based WiMax mesh
provides various advantages apart from increased range and higher bandwidth. The
TDMA based scheduling of channel access in WiMax-based multi-hop relay system
provides fine granularity radio resource control. This TDMA based scheduling mechanism
allows centralized slot allocation, which provides overall efficient resource utilization
suitable for fixed wireless backhaul network. (The WiMax based mesh backhaul
application differs from the802.11a/b/gbased mesh, which targets mobile ad hoc
networks.) However, the interference remains a major issue in multi hop WiMax mesh
networks. To provide high spectral usage, inefficient algorithm for slot allocation is
needed, so as to maximize the concurrent transmissions of data in the mesh. The level of
interference depends upon how the data is routed in the WiMax network.
In IEEE 802.16 Mesh mode, a Mesh base station (BS) provides backhaul connectivity of
the mesh network and controls one or more subscriber stations (SS). When centralized
scheduling scheme is used, the Mesh BS is responsible for collecting bandwidth request
from subscriber stations and for managing resource allocation. First will be introduced the
802.16 Mesh network entry process (i.e., a process by which a new node joins the mesh),
and then we describe the network resource allocation request/granting procedure.
In IEEE 802.16 Mesh mode, Mesh Network Configuration (MSH-NCFG) and Mesh
Network Entry (MSH-NENT) messages are used for advertisement of the mesh network
and for helping new nodes to synchronize and to joining the mesh network. Active nodes
within the mesh periodically advertise MSH-NCFG messages with Network Descriptor,
which outlines the basic network configuration information such as BS ID number and the
base channel currently used. A new node that plans to join an active mesh network scans
for active networks and listens to MSH-NCFG message.
The new node establishes coarse synchronization and starts the network entry process
based on the information given by MSHNCFG. Among all possible neighbors that
advertise MSH-NCFG, the joining node (which is Called Candidate Node in the 802.16
Mesh mode terminologies) selects a potential Sponsoring Node to connect to. A Mesh
Network Entry message (MSH-NENT) with Net Entry Request information is then sent by
the Candidate Node to join the mesh. The IEEE 802.16 Mesh mode MAC supports both
centralized scheduling and distributed scheduling.
Centralized mesh scheme is used to establish high-speed broadband mesh connections,
where the Mesh BS coordinates the radio resource allocation within the mesh network. In
22
the centralized scheme, every Mesh SS estimates and sends its resource request to the
Mesh BS, and the Mesh BS determined the amount of granted resources for each link and
communicates. The request and grant process uses the Mesh Centralized Scheduling
(MSHCSCH) message type. A Subscriber Stations capacity requests are sent using the
MSHCSCH:
Request message to the Subscriber Station’s parent node. After the Mesh BS determines
the resource allocation results, the MSH-CSCH: Grant is propagated along the route from
Mesh BS. To disseminate the link, node, and scheduling tree configuration information to
all participants within the mesh network, the Mesh Centralized Scheduling Configuration
(MSHCSCF) message is broadcasted by the Mesh BS and then re-broadcasted .
3.8. Wireless Services
What this points out is that WiMax actually can provide two forms of wireless service:
There is the non-line-of-sight, WiFi sort of service, where a small antenna on
subscriber computer connects to the tower. In this mode, WiMAX uses a lower
frequency range 2GHz to 11 GHz (similar to WiFi). Lower-wavelength
transmissions are not as easily disrupted by physical obstructions -- they are better
able to diffract, or bend, around obstacles.
Figure 3.2 Working of WiMax
23
There is line-of-sight service, where a fixed dish antenna points straight at the WiMax
tower from a rooftop or pole. The line-of-sight connection is stronger and more stable, so
it's able to send a lot of data with fewer errors. Line-of-sight transmissions use higher
frequencies, with ranges reaching a possible 66 GHz. At higher frequencies, there is less
interference and lots more bandwidth
WiFi-style access will be limited to a 4-to-6 mile radius (perhaps 25 square miles or 65
square km of coverage, which is similar in range to a cell-phone zone). Through the
stronger line-of sight antennas, the WiMax transmitting station would send data to
WiMAX-enabled computers or routers set up within the transmitter's 30-mile radius
(2,800 square miles or 9,300 square km of coverage). This is what allows WiMAX to
achieve its maximum range..
3.9. WiMax Infrastructure
Typically, a WiMax system consists of two parts:
A WiMax Base Station- Base station consists of indoor electronics and a WiMax
tower. Typically, a base station can cover up to 10 km radius (Theoretically, a
base station can cover-up to 50 kilo meter radius or 30 miles, however practical
considerations limit it to about 10km or 6 miles). Any wireless node within the
coverage area would be able to access the Internet.
A WiMax receiver - The receiver and antenna could be a stand-alone box or a PC
card that sits in your laptop or computer. Access to WiMax base station is similar
to accessing a Wireless Access Point in a WiFi network, but the coverage is more.
Figure 3.3. Topologies in urban and rural areas
24
Several base stations can be connected with one another by use of high-speed backhaul
microwave links. This would allow for roaming by a WiMax subscriber from one base
station to another base station area, similar to roaming enabled by Cellular phone
companies. Several topology and backhauling options are to be supported on the WiMax
base stations wire line backhauling (typically over Ethernet), microwave Point-to-Point
connection, as well as WiMax backhaul. With the latter option, the base station has the
capability to backhaul itself. This can be achieved by reserving part of the bandwidth
normally used for the end-user traffic and using it for backhauling purposes.
3.10. WiMAX Network IP-Based Architecture
The network specifications for WiMax-based systems are based on several basic network
architecture tenets, including those listed below. Some general tenets have guided the
development of Mobile WiMax Network Architecture and include the following:
Provision of logical separation between such procedures and IP addressing,
routing and connectivity management procedures and protocols to enable use of
the access architecture primitives in standalone and interworking deployment
scenarios,
Support for sharing of ASN(s) (Access Service Networks) of a Network Access
Provider (NAP) among multiple NSPs, - Support of a single NSP (Network
Service Provider) providing service over multiple ASN(s) – managed by one or
more NAPs,
Support for the discovery and selection of accessible NSPs by an MS or SS,
Support of NAPs that employ one or more ASN topologies,
Support of access to incumbent operator services through internetworking
functions as needed,
Specification of open and well-defined reference points between various groups of
network functional entities (within an ASN, between ASNs, between an ASN and
a CSN (Connectivity Service Network) , and between CSNs), and in particular
between an MS, ASN and CSN to enable multi-vendor interoperability,
Support for evolution paths between the various usage models subject to
reasonable technical assumptions and constraints,
Enabling different vendor implementations based on different combinations of
25
functional entities on physical network entities, as long as these implementations
comply with the normative protocols and procedures across applicable reference
points, as defined in the network specifications
Support for the most trivial scenario of a single operator deploying an ASN
together with a limited set of CSN functions, so that the operator can offer basic
Internet access service without consideration for roaming or interworking.
The WiMax architecture also allows both IP and Ethernet services, in a standard mobile IP
compliant network. The flexibility and interoperability supported by the WiMax network
provides operators with a multi-vendor low cost implementation of a WiMax network
even with a mixed deployment of distributed and centralized ASN’s in the network. The
WiMax network has the following major features:
Security. The end-to-end WiMax Network Architecture is based on a security
framework that is agnostic to the operator type and ASN topology and applies
consistently across Greenfield and internetworking deployment models and usage
scenarios. In particular there is support for:
1. Strong mutual device authentication between an MS and the WiMax
network, based on the IEEE 802.16 security framework,
2. All commonly deployed authentication mechanisms and authentication in
home and visited operator network scenarios based on a consistent and
extensible authentication framework
3. Data integrity, replay protection, confidentiality and non-repudiation using
applicable key lengths,
4. Use of MS initiated/terminated security mechanisms such as Virtual Private
Networks (VPNs),
5. Standard secure IP address management mechanisms between the MS/SS
and its home or visited NSP.
Mobility and Handovers. The end-to-end WiMax Network Architecture has
extensive capability to support mobility and handovers. It will:
1. Include vertical or inter-technology handovers— e.g., to Wi-Fi, 3GPP (The
Third Generation Partnership Project) , 3GPP2, DSL, or MSO (Multiple
Service Operators) – when such capability is enabled in multi-mode MS,
26
2. Support IPv4 (IP Version 4) or IPv6 based mobility management. Within
this framework, and as applicable, the architecture shall accommodate MS
with multiple IP addresses and simultaneous IPv4 and IPv6 connections,
3. Support roaming between NSPs,
4. Utilize mechanisms to support seamless handovers at up to vehicular
speeds— satisfying well defined (within WiMax Forum) bounds of service
disruption.
Some of the additional capabilities in support of mobility include the support of:
1. Dynamic and static home address configurations,
2. Dynamic assignment of the Home Agent in the service provider network as a
form of route optimization, as well as in the home IP network as a form of load
balancing
3. Dynamic assignment of the Home Agent based on policies.
Quality of Service. The WiMax Network Architecture has provisions
for support of QoS mechanisms. In particular, it enables flexible
support of simultaneous use of a diverse set of IP services. The
architecture supports:
1. Differentiated levels of QoS - coarse-grained (per user/terminal) and/or fine-
grained (per service flow per user/terminal),
2. Admission control, and
3. Bandwidth management Extensive use is made of standard IETF mechanisms for
managing policy definition and policy enforcement between operators.
3.11. End-to-End WiMax Architecture
The IEEE only defined the Physical (PHY) and Media Access Control (MAC) layers in
802.16. This approach has worked well for technologies such as Ethernet and WiFi, which
rely on other bodies such as the IETF (Internet Engineering Task Force) to set the
standards for higher layer protocols such as TCP/IP, SIP, VoIP and IPSec[11]. In the
mobile wireless world, standards bodies such as 3GPP and 3GPP2 set standards over a
wide range of interfaces and protocols because they require not only air link
interoperability, but also inter-vendor internet work interoperability for roaming, multi-
vendor access networks, and inter-company billing.
Vendors and operators have recognized this issue, and have formed additional working
27
groups to develop standard network reference models for open inter-network interfaces.
Two of these are the WiMax Forum’s Network Working Group, which is focused on
creating higher-level networking specifications for fixed, nomadic, portable and mobile
WiMax systems beyond what is defined in the IEEE 802.16 standard, and Service
Provider Working Group which helps write requirements and prioritizes them to help
drive the work of Network WG. The Mobile WiMax End-to-End Network Architecture is
based an All-IP platform, all packet technology with no legacy circuit telephony. It offers
the advantage of reduced total cost of ownership during the lifecycle of a WiMax network
deployment.
The use of All-IP means that a common network core can be used, without the need to
maintain both packet and circuit core networks, with all the overhead that goes with it. A
further benefit of All-IP is that it places the network on the performance growth curve of
general processing advances occur much faster than advances in telecommunications
equipment because general purpose hardware is not limited to telecommunications
equipment cycles, which tend to be long and cumbersome. The end result is a network that
continually performs at ever higher capital and operational efficiency, and takes advantage
of 3rd party developments from the Internet community. This results in lower cost, high
scalability, and rapid deployment since the networking functionality is all primarily
software-based services. In order to deploy successful and operational commercial
systems, there is need for support beyond 802.16 (PHY/MAC) air interface specifications.
Chief among them is the need to support a core set of networking functions as part of the
overall End-to-End WiMax system architecture. Before delving into some of the details of
the architecture, we can note a few basic tenets that have guided the WiMax architecture
development:
The architecture is based on a packet-switched framework, including native
procedures based on the IEEE 802.16 standard and its amendments, appropriate
IETF RFCs and Ethernet standards.
The architecture permits decoupling of access architecture (and supported
topologies) from connectivity IP service. Network elements of the connectivity
system are agnostic to the IEEE 802.16 radio specifics.
The architecture allows modularity and flexibility to accommodate a broad range
of deployment options such as:
28
1. Small-scale to large-scale (sparse to dense radio coverage and capacity)
WiMax networks.
2. Urban, suburban, and rural radio propagation environments
3. Licensed and/or licensed-exempt frequency bands
4. Hierarchical, flat, or mesh topologies, and their variants
5. Co-existence of fixed, nomadic, portable and mobile usage models
3.11.1 Support for Services and Applications. The end-to-end architecture includes the
support for:
Voice, multimedia services and other mandated regulatory services such as
emergency services and lawful interception,
Access to a variety of independent Application Service Provider (ASP) networks
in an agnostic manner,
Mobile telephony communications using VoIP,
Support interfacing with various interworking and media gateways permitting
delivery of incumbent/legacy services translated over IP (for example, SMS over
IP, MMS, WAP) to WiMax access networks and
Support delivery of IP Broadcast and Multicast services over WiMax access
networks.
3.11.2 Interworking and Roaming. Another key strength of the End-to-End Network
Architecture with support for a number of deployment scenarios. In particular, there will
be support of - Loosely-coupled interworking with existing wireless networks such as
3GPP and 3GPP2 or existing wire line networks such as DSL, with the interworking
interface(s) based on a standard IETF suite of protocols,
Global roaming across WiMAX operator networks, including support for
credential reuse, consistent use of AAA for accounting and billing, and
consolidated/common billing and settlement,
A variety of user authentication credential formats such as username/password,
digital certificates, Subscriber Identify Module (SIM), Universal SIM (USIM),
and Removable User Identify Module (RUIM).
WiMax Forum industry participants have identified a WiMax Network Reference
Model(NRM) that is a logical representation of the network architecture. The NRM
29
identifies functional entities and reference points over which interoperability is achieved
between functional entities. The architecture has been developed with the objective of
providing unified support of functionality needed in a range of network deployment
models and usage scenarios (ranging from fixed – nomadic – portable – simple mobility –
to fully mobile subscribers).
3.12. WiMax Protocol
An 802.16 wireless service provides a communications path between a subscriber site and
a core network such as the public telephone network and the Internet.
Table3.3 WiMax, WLAN, and Bluetooth parameters
This wireless broadband access standard provides the missing link for the "last mile"
connection in metropolitan area networks where DSL, Cable and other broadband access
methods are not available or too expensive. The Wireless MAN technology is also
branded as WiMax
IEEE 802.16 Protocol Architecture has 4 layers: Convergence, MAC, Transmission and
physical, which can be map to two OSI lowest layers: physical and data link, as shown at
Figure
Figure 3.4 IEEE 802.16 Protocol Architecture
30
3.13 Mobile WiMax
3.13.1 Introduction
The WiMax technology, based on the IEEE 802.16-2004 Air Interface Standard is rapidly
proving itself as a technology that will play a key role in fixed broadband wireless
metropolitan area networks. The first certification lab, established at Cetecom Labs in
Malaga, Spain is fully operational and more than 150 WiMax trials are underway in
Europe, Asia, Africa and North and South America. Unquestionably, Fixed WiMax, based
on the
IEEE 802.16-2004 Air Interface Standard, has proven to be a cost-effective fixed wireless
alternative to cable and DSL services. In December, 2005 the IEEE ratified the 802.16e
amendment to the 802.16 standard. This amendment adds the features and attributes to the
standard that is necessary to support mobility. The WiMax Forum is now defining system
performance and certification profiles based on the IEEE 802.16e Mobile Amendment
and, going beyond the air interface, the WiMax Forum is defining the network architecture
necessary for implementing an end-to-end Mobile WiMax2 network. Release-1 system
profiles were completed in early 2006.
Mobile WiMax is a broadband wireless solution that enables convergence of mobile and
fixed broadband networks through a common wide area broadband radio access
technology and flexible network architecture. The Mobile WiMax Air Interface adopts
Orthogonal Frequency Division Multiple Access (OFDMA) for improved multi-path
performance in non line-of-sight environments. Scalable OFDMA (SOFDMA) is
introduced in the IEEE 802.16eAmendment to support scalable channel bandwidths from
1.25 to 20 MHz.
The Mobile Technical Group (MTG) in the WiMax Forum is developing the Mobile
WiMAX system profiles that will define the mandatory and optional features of the IEEE
standard that are necessary to build a Mobile WiMax compliant air interface that can be
certified by the WiMAX Forum. The Mobile WiMax System Profile enables mobile
systems to be configured based on a common base feature set thus ensuring baseline
functionality for terminals and base stations that are fully interoperable. Some elements of
the base station profiles are specified as optional to provide additional flexibility for
deployment based on specific deployment scenarios that may require different
configurations that are either capacity-optimized or coverage-optimized. Release-1 Mobile
WiMax profiles will cover 5,7, 8.75, and 10 MHz channel bandwidths for licensed
31
worldwide spectrum allocations in the2.3 GHz, 2.5 GHz, and 3.5 GHz frequency bands.
Mobile WiMax systems offer scalability in both radio access technology and network
architecture, thus providing a great deal of flexibility in network deployment options and
service offerings. Some of the salient features supported by Mobile WiMax are:
High Data Rates. The inclusion of MIMO (Multiple Input Multiple Output)
antenna techniques along with flexible sub-channelization schemes, Advanced
Coding and Modulation all enable the Mobile WiMax technology to support peak
DL data rates up to 63Mbps per sector and peak UL data rates up to 28 Mbps per
sector in a 10 MHz channel.
Quality of Service (QoS). The fundamental premise of the IEEE 802.16 MAC
architecture is QoS. It defines Service Flows which can map to Diff Serv code
points that enable end-to end IP based QoS. Additionally, sub channelization
schemes provide a flexible mechanism for optimal scheduling of space, frequency
and time resources over the air interface on a frame by-frame basis.
Scalability. Despite an increasingly globalize economy, spectrum resources for
wireless broadband worldwide are still quite disparate in its allocations. Mobile
WiMax technology therefore, is designed to be able to scale to work in different
canalizations from 1.25 to 20 MHz to comply with varied worldwide requirements
as efforts proceed to achieve spectrum harmonization in the longer term. This also
allows diverse economies to realize the multifaceted benefits of the Mobile
WiMax technology for their specific geographic needs such as providing
affordable internet access in rural settings versus enhancing the capacity of mobile
broadband access in metro and suburban areas.
Security. Support for a diverse set of user credentials exists including; SIM/USIM
cards, Smart Cards, Digital Certificates, and Username/Password schemes.
Mobility. Mobile WiMax supports optimized handover schemes with latencies
less than 50milliseconds to ensure real-time applications such as VoIP perform
without service degradation. Flexible key management schemes assure that
security is maintained during handover.
3.13.2. Physical Layer Description
WiMax must be able to provide a reliable service over long distances to customers using
indoor terminals or PC cards (like today's WLAN cards). These requirements, with limited
32
transmit power to comply with health requirements, will limit the link budget. Sub
channeling in uplink and smart antennas at the base station has to overcome these
constraints. The WiMax system relies on a new radio physical (PHY) layer and
appropriate MAC (Media Access Controller) layer to support all demands driven by the
target applications.
The PHY layer modulation is based on OFDMA, in combination with a centralized MAC
layer for optimized resource allocation and support of QoS for different types of
services(VoIP, real-time and non real-time services, best effort). The OFDMA PHY layer
is well adapted to the NLOS propagation environment in the 2 - 11 GHz frequency range.
It is inherently robust when it comes to handling the significant delay spread caused by the
typical NLOS reflections. Together with adaptive modulation, which is applied to each
subscriber individually according to the radio channel capability, OFDMA can provide a
high spectral efficiency of about 3 - 4 bit/s/Hz. However, in contrast to single carrier
modulation, the OFDMA signal has an increased peak: average ratio and increased
frequency accuracy requirements. Therefore, selection of appropriate power amplifiers and
frequency recovery concepts are crucial. WiMax provides flexibility in terms of
channelization, carrier frequency, and duplex mode (TDD and FDD) to meet a variety of
requirements for available spectrum resources and targeted services.
3.14 OFDMA Basics
Orthogonal Frequency Division Multiplexing (OFDM) is a multiplexing technique that
subdivides the bandwidth into multiple frequency sub-carriers as shown in Figure In an
OFDM system, the input data stream is divided into several parallel sub-streams of
reduced data rate (thus increased symbol duration) and each sub-stream is modulated and
Figure 3.5. Basic Architecture of an OFDM System
33
transmitted on a separate orthogonal sub-carrier. The increased symbol duration improves
the robustness of OFDM to delay spread. Furthermore, the introduction of the cyclic prefix
(CP) can completely eliminate Inter-Symbol Interference (ISI) as long as the CP duration
is longer than the channel delay spread. The CP is typically a repetition of the last samples
of data portion of the block that is appended to the beginning of the data payload as shown
The CP prevents inter-block interference and makes the channel appear circular and
permits low complexity frequency domain equalization. A perceived drawback of CP is
that it introduces overhead, which effectively reduces bandwidth efficiency. While the CP
does reduce bandwidth efficiency somewhat, the impact of the CP is similar to the “roll-
off factor” in raised-cosine filtered single-carrier systems. Since OFDM has a very sharp,
almost “brick wall” spectrum, a large fraction of the allocated channel bandwidth can be
utilized for data transmission, which helps to moderate the loss in efficiency due to the
cyclic prefix.
.
Figure 3.6. Insertion of Cyclic Prefix (CP)
OFDM exploits the frequency diversity of the multipath channel by coding and
interleaving the information across the sub-carriers prior to transmissions. OFDM
modulation can be realized with efficient Inverse Fast Fourier Transform (IFFT), which
enables a large number of sub-carriers (up to 2048) with low complexity. In an OFDM
system, resources are available in the time domain by means of OFDM symbols and in the
frequency domain by means of sub-carriers. The time and frequency resources can be
organized into sub-channels for allocation to individual users.
3.15 TDD Frame Structure
The 802.16e PHY supports TDD, FDD, and Half-Duplex FDD operation; however the
34
initial release of Mobile WiMax certification profiles will only include TDD. With
ongoing releases, FDD profiles will be considered by the WiMax Forum to address
specific market opportunities where local spectrum regulatory requirements either prohibit
TDD or are more suitable for FDD deployments. To counter interference issues, TDD
does require system-wide synchronization; nevertheless, TDD is the preferred duplexing
mode for the following reasons:
TDD enables adjustment of the downlink/uplink ratio to efficiently support
asymmetric downlink/uplink traffic, while with FDD, downlink and uplink always
have fixed and generally, equal DL and UL bandwidths.
TDD assures channel reciprocity for better support of link adaptation, MIMO and
other closed loop advanced antenna technologies.
Unlike FDD, which requires a pair of channels, TDD only requires a single
channel for both downlink and uplink providing greater flexibility for adaptation
to varied global spectrum allocations.
Transceiver designs for TDD implementations are less complex and therefore less
expensive.
3.16 MAC Layer Description
The 802.16 standard was developed from the outset for the delivery of broadband services
including voice, data, and video. The MAC layer is based on the time-proven DOCSIS
standard and can support bursty data traffic with high peak rate demand while
simultaneously supporting streaming video and latency-sensitive voice traffic over the
same channel. The resource allocated to one terminal by the MAC scheduler can vary
from a single time slot to the entire frame, thus providing a very large dynamic range of
throughput to a specific user terminal at any given time. Furthermore, since the resource
allocation information is conveyed in the MAP messages at the beginning of each frame,
the scheduler can effectively change the resource allocation on a frame-by-frame basis to
adapt to the bursty nature of the traffic.
35
Every wireless network operates fundamentally in a shared medium and as such that
requires a mechanism for controlling access by subscriber units to the medium. The
802.16a standard uses a slotted TDMA protocol scheduled by the BTS to allocate capacity
to subscribers in a point-to-multipoint network topology. While this on the surface sounds
like a one line, technical throwaway statement, it has a huge impact on how the system
Figure 3.7. 802.16a MAC Features
operates and what services it can deploy. By starting with a TDMA approach with
intelligent scheduling, WiMax systems will be able to deliver not only high speed data
with SLAs, but latency sensitive services such as voice and video or database access are
also supported. The standard delivers QoS beyond mere prioritization, a technique that is
very limited in effectiveness as Traffic load and the number of subscriber’s increases. The
MAC layer in WiMax certified systems has also been designed to address the harsh
physical layer environment where interference, fast fading and other phenomena are
prevalent in outdoor operation.
3.17 QoS Support
With fast air link, symmetric downlink/uplink capacity, fine resource granularity and a
flexible resource allocation mechanism, Mobile WiMax can meet QoS requirements for a
wide range of data services and applications.
36
Figure 3.8 Mobile WiMax QoS Support
This is a unidirectional flow of packets that is provided with a particular set of QoS
parameters. Before providing a certain type of data service, the base station and user
terminal first establish a unidirectional logical link between the peer MACs called a
connection. The outbound MAC then associates packets traversing the MAC interface into
a service flow to be delivered over the connection. The QoS parameters associated with
the service flow define the transmission ordering and scheduling on the air interface. The
connection-oriented QoS therefore, can provide accurate control over the air interface.
Since the air interface is usually the bottleneck, the connection-oriented QoS can
effectively enable the end-to-end QoS control. The service flow parameters can be
dynamically managed through MAC messages to accommodate the dynamic service
demand. The service flow based QoS mechanism applies to both DL and UL to provide
improved QoS in both directions.
3.18 Mobility Management
Battery life and handoff are two critical issues for mobile applications. Mobile WiMax
supports Sleep Mode and Idle Mode to enable power-efficient MS operation. Mobile
WiMax also supports seamless handoff to enable the MS to switch from one base station
37
to another at vehicular speeds without interrupting the connection.
Power Management. Mobile WiMax supports two modes for power efficient
operation Sleep Mode and Idle Mode. Sleep Mode is a state in which the MS
conducts pre-negotiated periods of absence from the Serving Base Station air
interface. These periods are characterized by the unavailability of the MS, as
observed from the Serving Base Station, to DL or UL traffic. Sleep Mode is
intended to minimize MS power usage and minimize the usage of the Serving Base
Station air interface resources. The Sleep Mode also provides flexibility for the MS
to scan other base stations to collect information to assist handoff during the Sleep
Mode. Idle Mode provides a mechanism for the MS to become periodically
available for DL broadcast traffic messaging without registration at a specific base
station as the MS traverses an air link environment populated by multiple base
stations. Idle Mode benefits the MS by removing the requirement for handoff and
other normal operations and benefits the network and base station by eliminating
air interface and network handoff traffic from essentially inactive MSs while still
providing a simple and timely method (paging) for alerting the MS about pending
DL traffic.
Handoff. The IEEE 802 Handoff Study Group, is another group chartered with
addressing roaming that studies hand-offs between heterogeneous 802 networks.
The key here will be enabling the “hand-off” procedures that allow a mobile device
to switch the connection from one base station to another, from one 802 network
type to another (such as from 802.11b to 802.16), and even from wired to 802.11
or 802.16 connections. The goal is to standardize the hand-off so devices are
interoperable as they move from one network type to another. Today, 802.11 users
can move around a building or a hotspot and stay connected, but if they leave, they
lose their connection. With 802.16e, users will be able to stay “best connected”—
connected by 802.11 when they’re within a hot spot, and then connected to 802.16
when they leave the hot spot but are within a WiMax service area. Furthermore,
having a standard in place opens the door to volume component suppliers that will
allow equipment vendors to focus on system design, versus having to develop the
whole end-to-end solution. When having either 802.16e capabilities embedded in a
PDA or notebook (or added through an 802.16e-enabled card) user remain
38
connected within an entire metropolitan area. For example, a notebook could connect
via Ethernet or 802.11 when docked, and stay connected with 802.16 when roaming
the city or suburbs. There are three handoff methods supported within the 802.16e
standard – Hard Handoff(HHO), Fast Base Station Switching (FBSS) and Macro
Diversity Handover (MDHO). Of these, the HHO is mandatory while FBSS and
MDHO are two optional modes. The WiMax Forum has developed several techniques
for optimizing hard handoff within the framework of the 802.16e standard. These
improvements have been developed with the Security Mobile WiMax supports best in
class security features by adopting the best technologies available today. Support
exists for mutual device/user authentication, flexible key management protocol, strong
traffic encryption, control and management plane message protection and security
protocol optimizations for fast handovers. The usage aspects of the security features
are:
Key Management Protocol. Privacy and Key Management Protocol Version 2
(PKMv2) is the basis of Mobile WiMax security as defined in 802.16e. This
protocol manages the MAC security using Traffic Encryption Control, Handover
Key Exchange and Multicast/Broadcast security messages all are based on this
protocol.
Device/User Authentication. Mobile WiMax supports Device and User
Authentication using IETF EAP (Internet Engineering Task Force Extensible
Authentication Protocol) by providing support for credentials that are SIM-based,
USIM-based or Digital Certificate or Username/Password-based.
Traffic Encryption. Cipher used techniques for protecting all the user data over
the Mobile WiMax MAC interface. The keys used for driving the cipher are
generated from the EAP authentication. A Traffic Encryption State machine that
has a periodic key (TEK) refresh mechanism enables sustained transition of keys to
further improve protection.
Fast Handover Support: A 3-way Handshake scheme is supported by Mobile
WiMax to optimize the re-authentication mechanisms for supporting fast
handovers. This mechanism is also useful to prevent any man-in-the-middle-
attacks.
39
3.19 Advanced Features of WiMax
An important and very challenging function of the WiMax system is the support of various
advanced antenna techniques, which are essential to provide high spectral efficiency,
capacity, system performance, and reliability:
Beam forming using smart antennas provides additional gain to bridge long
distances or to increase indoor coverage; it reduces inter-cell interference and
improves frequency reuse,
Transmit diversity and MIMO techniques using multiple antennas take advantage
of multipath reflections to improve reliability and capacity.
3.19.1 Smart Antenna Technologies
Smart antenna technologies typically involve complex vector or matrix operations on
signals due to multiple antennas. OFDMA allows smart antenna operations to be
performed on vector-flat sub-carriers. Complex equalizers are not required to compensate
for frequency selective fading. OFDMA therefore, is very well-suited to support smart
antenna technologies. In fact, MIMO-OFDM/OFDMA is envisioned as the corner-stone
for next generation broadband communication systems. Mobile WiMax supports a full
range of smart antenna technologies to enhance system performance. The smart antenna
technologies supported include:
Beam forming. With beam forming, the system uses multiple-antennas to transmit
weighted signals to improve coverage and capacity of the system and reduce
outage probability.
Space-Time Code (STC). Transmit diversity such as Alamouti code is supported
to provide spatial diversity and reduce fade margin.
Spatial Multiplexing (SM). Spatial multiplexing is supported to take advantage of
higher peak rates and increased throughput. With spatial multiplexing, multiple
streams are transmitted over multiple antennas. If the receiver also has multiple
antennas, it can separate the different streams to achieve higher throughput
compared to single antenna systems. With 2x2 MIMO, SM increases the peak data
rate two-fold by transmitting two data streams. In UL, each user has only one
transmit antenna, two users can transmit collaboratively in the same slot as if two
streams are spatially multiplexed from two antennas of the same user.
40
3.19.2 Fractional Frequency Reuse
WiMax supports frequency reuse of one, i.e. all cells/sectors operate on the same
frequency channel to maximize spectral efficiency. However, due to heavy co channel
interference (CCI) in frequency reuse one deployment, users at the cell edge may suffer
degradation in connection quality. Users can operate on sub channels, which only occupy
a small fraction of the whole channel bandwidth; the cell edge interference problem can be
easily addressed by appropriately configuring sub channel usage without resorting to
traditional frequency planning. The flexible sub-channel reuse is facilitated
Figure 3.9. Fractional Frequency Reuse
by sub-channel segmentation and permutation zone. A segment is a subdivision of the
available OFDMA sub-channels (one segment may include all sub-channels). One
segment is used for deploying a single instance of MAC.
3.19.3 Multicast and Broadcast Service (MBS)
Multicast and Broadcast Service (MBS) supported by WiMax satisfy the following
requirements:
High data rate and coverage using a Single Frequency Network (SFN)
Flexible allocation of radio resources
Low MS power consumption
Support of data-casting in addition to audio and video streams
Low channel switching time
The WiMax Release-1 profile defines a toolbox for initial MBS service delivery. The
41
MBS service can be supported by either constructing a separate MBS zone in the DL
frame along with unicast service (embedded MBS) or the whole frame can be dedicated to
MBS (DL only) for standalone broadcast service.
42
CHAPTER – 4
PERFORMANCE ANALYSIS
4.1. Markets for WiMax
Broadband Wireless Access (BWA) has been serving enterprises and operators for years,
to the great satisfaction of its users. However, the new IP-based standard developed by the
IEEE 802.16 is likely to accelerate adoption of the technology. It will expand the scope of
usage thanks to: the possibility of operating in licensed and unlicensed frequency bands,
unique performance under Non-Line-of-Sight (NLOS) conditions, Quality of Service
(QoS) awareness, extension to nomad city, and more. In parallel, the WiMax forum,
backed by industry leaders, will encourage the widespread adoption of broadband wireless
access by establishing a brand for the technology and pushing interoperability between
products.
A wireless MAN based on the WiMax air interface standard is configured in much the
same way as a traditional cellular network with strategically located base stations using a
point-to multipoint architecture to deliver services over a radius up to several kilometers
depending on frequency, transmit power and receiver sensitivity. In areas with high
population densities the range will generally be capacity limited rather than range limited
due to limitation in the amount of available spectrum. The base stations are typically
backhauled to the core network by means of fiber or point-to-point microwave links to
available fiber nodes or via leased lines from an incumbent wire-line operator. The range
and NLOS capability makes the technology equally attractive and cost-effective in a wide
variety of environments. The technology was envisioned from the beginning as a means to
provide wireless “last mile” broadband access in the Metropolitan Area Network (MAN)
with performance and services comparable to or better than traditional DSL, Cable or
T1/E1 leased line services.
Residential and SOHO High Speed Internet Access. The main contenders for
residential and SOHO market are the DSL, and Cable Internet technologies. These
technologies have already established a market presence, and have proven track record
in meeting the demands of the residential and SOHO customers. WiMax provides an
alternative to existing access methods, where it is not feasible to use DSL or Cable
Internet. Typical application will be in remote areas where it is not economically
43
feasible to have a DSL or Cable Internet. WiMax is also expected to be more reliable
due to wireless nature of communication between the customer premises and the base
station. This is particularly useful in developing countries where the reliability and
quality of land-line communications infrastructure is often poor. Today, this market
segment is primarily dependent on the availability of DSL or cable. In some areas the
available services may not meet customer expectations for performance or reliability
and/or are too expensive. In many rural areas residential customers are limited to low
speed dial-up services. In developing countries there are many regions with no
available means for internet access. The analysis will show that the WiMax technology
will enable an operator to economically address this market segment and have a
winning business case under a variety of demographic conditions.
Small and Medium Business. The WiMax BWA is well suited to provide the
reliability and speed for meeting the requirements of small and medium size
businesses in low density environments. One disadvantage of WiMax is the spectral
limitation, in other words limitation of wireless bandwidth. For use in high density
areas, it is possible that the bandwidth may not be sufficient to cater to the needs of a
large clientele, driving the costs high.
This market segment is very often underserved in areas other than the highly competitive
urban environments. The WiMax technology can cost-effectively meet the requirements of
small and medium size businesses in low density environments and can also provide a
cost-effective alternative in urban areas competing with DSL and leased line services.
WiFi Hot Spot Backhaul. Another area where WiMax connectivity is for WiFi hot.
Figure 4.1. Markets for WiMAX
44
spots connectivity. As of now, there have been several WiFi hotspots and a WiMax
backhaul provides full wireless solution to these wireless networks
WiFi hot spots are being installed worldwide at a rapid pace. One of the obstacles for
continued hot spot growth however, is the availability of high capacity, cost-effective
backhaul solutions. This application can also be addressed with the WiMax technology.
And with nomadic capability, WiMax can also fill in the coverage gaps between WiFi hot
spot coverage areas.
Figure 4.2. The WiMAX Wireless Architecture
4.2 Current Status of WiMax
Figure 4.3. Gartner Hype Cycle for Wireless
45
With many technologies, there is a tendency for expectations initially to far exceed the
achievable reality. The “Gartner Hype Cycle for Wireless Networking, 2004” shows
WiMax technology at the “Peak of Inflated Expectations,” with the “Plateau of
Productivity” expected in the “two to five years” time frame.
4.3 The WiMAX Scenario
Here's what would happen if you got WiMax. An Internet service provider sets up a
WiMAX base station 10 miles from your home. You would buy a WiMax-enabled
computer or upgrade your old computer to add WiMax capability. You would receive a
special encryption code that would give you access to the base station. The base station
would beam data from the Internet to your computer (at speeds potentially higher than
today's cable modems), for which you would pay the provider a monthly fee. The cost for
this service could be much lower than current high-speed Internet-subscription fees
because the provider never had to run cables.
Network scale. The smallest-scale network is a personal area network (PAN). A PAN
allows devices to communicate with each other over short distances. Bluetooth is the best
example of a PAN. The next step up is a local area network (LAN). A LAN allows devices
to share information, but is limited to a fairly small central area, such as a company's
headquarters, a coffee shop or your house. Many LANs use WiFi to connect the network
wirelessly. WiMax is the wireless solution for the next step up in scale, the metropolitan
area network (MAN), as shown at Figure . A MAN allows areas the size of cities to be
connected.
Figure 4.4. WiMax Network scale
46
The WiMax protocol is designed to accommodate several different methods of data
transmission, one of which is Voice Over Internet Protocol (VoIP). VoIP allows people to
make local, long-distance and even international calls through a broadband Internet
connection, bypassing phone companies entirely. If WiMax-compatible computers
become very common, the use of VoIP could increase dramatically. Almost anyone with a
laptop could make VoIP calls.
4.4.WiMAX versus 3G and Wi-Fi
How does WiMAX compare with the existing and emerging capabilities of 3G and Wi-Fi?
The throughput capabilities of WiMax depend on the channel bandwidth used. Unlike 3G
systems, which have a fixed channel bandwidth, WiMax defines a selectable channel
bandwidth from 1.25MHz to 20MHz, which allows for a very flexible deployment. When
deployed using the more likely 10MHz TDD (time division duplexing) channel, assuming
a 3:1 downlink-to-uplink split, WiMax offers 46Mbps peak downlink throughput and
7Mbps uplink.
The reliance of Wi-Fi and WiMax on OFDM modulation, as opposed to CDMA as in 3G,
allows them to support very high peak rates. The need for spreading makes very high data
rates more difficult in CDMA systems.
More important than peak data rate offered over an individual link is the average
throughput and overall system capacity when deployed in a multicultural environment.
From a capacity standpoint, the more pertinent measure of system performance is spectral
efficiency. WiMax specifications accommodated multiple antennas right from the start
gives it a boost in spectral efficiency. In 3G systems, on the other hand, multiple-antenna
support is being added in the form of revisions. Further, the OFDM physical layer used by
WiMax is more amenable to MIMO implementations than are CDMA systems from the
standpoint of the required complexity for comparable gain. OFDM also makes it easier to
exploit frequency diversity and multi-user diversity to improve capacity. Therefore, when
compared to 3G, WiMax offers higher peak data rates, greater flexibility, and higher
average throughput and system capacity.
Another advantage of WiMax is its ability to efficiently support more symmetric links
useful for fixed applications, such as T1 replacement—and support for flexible and
dynamic adjustment of the downlink-to-uplink data rate ratios. Typically, 3G systems have
a fixed asymmetric data rate ratio between downlink and uplink what about in terms of
47
supporting advanced IP applications, such as voice, video, and multimedia?
How do the technologies compare in terms of prioritizing traffic and controlling quality?
The WiMax media access control layer is built from the ground up to support a variety of
traffic mixes, including real-time and non-real-time constant bit rate and variable bit rate
traffic, prioritized data, and best-effort data. Such 3G solutions as HSDPA and 1x EV-DO
were also designed for a variety of QoS levels. Perhaps the most important advantage for
WiMax may be the potential for lower cost owing to its lightweight IP architecture. Using
an IP architecture simplifies the core network, 3G has a complex and separate core
network for voice and data and reduces the capital and operating expenses. IP also puts
WiMax on a performance/price curve that is more in line with general-purpose processors
(Moore’s Law), thereby providing greater capital and operational efficiencies. IP also
allows for easier integration with third-party application developers and makes
convergence with other networks and applications easier.
Table 4.1 Comparison of wireless technologies
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In terms of supporting roaming and high-speed vehicular mobility, WiMAX capabilities
are somewhat unproven when compared to those of 3G. In 3G, mobility was an integral
part of the design; WiMax was designed as a fixed system, with mobility capabilities
developed as an add-on feature.
In summary, WiMax occupies a somewhat middle ground between Wi-Fi and 3G
technologies when compared in the key dimensions of data rate, coverage, QoS, mobility,
and price. Table 4.1 provides a summary comparison of WiMax with 3G and Wi-Fi
technologies.
4.4.1 Other Comparable Systems
So far, we have limited our comparison of WiMax to 3G and Wi-Fi technologies. Two
other standards based-technology solutions could emerge in the future with some overlap
with WiMAX: the IEEE 802.20 and IEEE 802.22 standards under development. The IEEE
802.20 standard is aimed at broadband solutions specifically for vehicular mobility up to
250 kmph.
This standard is likely to be defined for operation below 3.5GHz to deliver peak user data
rates in excess of 4Mbps and 1.2Mbps in the downlink and uplink, respectively. This
standards development effort began a few years ago but it has not made much progress,
owing to lack of consensus on technology and issues with the standardization process. The
IEEE 802.22 standard is aimed specifically at bringing broadband access to rural and
remote areas through wireless define a cognitive radio that can take advantage of unused
TV channels that exist in these sparsely populated areas. Operating in the VHF and low
UHF bands provides favorable propagation conditions that can lead to greater range. This
development effort is motivated by the fact that the FCC plans to allow the use of this
spectrum without licenses as long as a cognitive radio solution that identifies and operates
in unused portions of the spectrum is used. IEEE 802.22 is in early stages of development
and is expected to provide fixed broadband applications over larger coverage areas with
low user densities.
4.5 Competing technologies
Speed vs. Mobility of wireless systems: Wi-Fi, HSPA, UMTS, GSM Within the
marketplace, WiMax's main competition comes from existing, widely deployed wireless
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systems such as UMTS, CDMA2000 and of course long range mobile Wi-Fi and mesh
networking.
3G cellular phone systems usually benefit from already having entrenched infrastructure,
having been upgraded from earlier systems. Users can usually fall back to older systems
when they move out of range of upgraded equipment, often relatively seamlessly.
The major cellular standards are being evolved to so-called 4G, high-bandwidth, low-
latency, all-IP networks with voice services built on top. The worldwide move to 4G for
GSM/UMTS and AMPS/TIA (including CDMA2000) is the 3GPP Long Term Evolution
effort. A planned CDMA2000 replacement called Ultra Mobile Broadband has been
discontinued. For 4G systems, existing air interfaces are being discarded in favor of
OFDMA for the downlink and a variety of OFDM based techniques for the uplink, similar
to WiMax.
In some areas of the world, the wide availability of UMTS and a general desire for
standardization has meant spectrum has not been allocated for WiMax: in July 2005, the
EU-wide frequency allocation for WiMax was blocked.
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CHAPTER- 5
CONCLUSION AND FUTURE SCOPE
5.1 Conclusion
WiMax offers benefits for wire line operators who want to provide last mile access to
residences and businesses, either to reduce costs in their own operating areas, or as a way
to enter new markets. 802.16e offers cost reductions to mobile operators who wish to offer
broadband IP services in addition to 2G or 3G voice service, and allows operators to enter
new markets with competitive services, despite owning disadvantaged spectrum. The
capital outlay for WiMAX equipment will be less than for traditional 2G and 3G wireless
networks, although the supporting infrastructure of cell sites, civil works, towers and so on
will still be needed. WiMax’s all-IP architecture lends itself well to high bandwidth multi-
media applications, and with QoS will also support mobile voice and messaging services,
re-using the mobile networks IP core systems.
The latest developments in the IEEE 802.16 group are driving a broadband wireless access
revolution to a standard with unique technical characteristics. In parallel, the WiMax
forum, backed by industry leaders, helps the widespread adoption of broadband wireless
access by establishing a brand for the technology. Initially, WiMax will bridge the digital
divide and thanks to competitive equipment prices, the scope of WiMax deployment will
broaden to cover markets with high DSL unbundling costs or poor copper quality which
have acted as a brake on extensive high-speed Internet and voice over broadband. WiMax
will reach its peak by making Portable Internet a reality. When WiMax chipsets are
integrated into laptops and other portable devices, it will provide high-speed data services
on the move, extending today's limited coverage of public WLAN to metropolitan areas.
Integrated into new generation networks with seamless roaming between various accesses,
it will enable end-users to enjoy an "Always Best Connected" experience. The
Combination of these capabilities makes WiMax attractive for a wide diversity of people:
fixed operators, mobile operators and wireless ISPs (Internet Service Provider), but also
for many vertical markets and local authorities. Alcatel, the worldwide broadband market
leader with a market share in excess of 37%, is committed to offer complete support
across the entire investment and operational cycle required for successful deployment of
WiMax services
• WiMax is based on a very flexible and robust air interface defined by the IEEE 802.16
51
group.
• The WiMax physical layer is based on OFDM, which is an elegant and effective
technique for overcoming multipart distortion.
• The physical layer supports several advanced techniques for increasing the reliability of
The link layer. These techniques include powerful error correction coding, including turbo
coding and LDPC, hybrid-ARQ, and antenna arrays.
• WiMax supports a number of advanced signal-processing techniques to improve overall
system capacity. These techniques include adaptive modulation and coding, spatial
multiplexing, and multi-user diversity.
• WiMax has a very flexible MAC layer that can accommodate a variety of traffic types,
Including voice, video, and multimedia, and provide strong QoS.
• Robust security functions, such as strong encryption and mutual authentication, are built
Into the WiMax standard.
• WiMax has several features to enhance mobility-related functions such as seamless
handover and low power consumption for portable devices.
• WiMax defines a flexible all-IP-based network architecture that allows for the
exploitation of all the benefits of IP. The reference network model calls for the use of IP-
based protocols to deliver end-to-end functions, such as QoS, security, and mobility
Management.
• WiMax offers very high spectral efficiency, particularly when using higher-order MIMO
solutions.
5.2 Future scope
The IEEE 802.16m standard is the core technology for the proposed Mobile WiMax
Release 2, which enables more efficient, faster, and more converged data communications.
The IEEE 802.16m standard has been submitted to the ITU for IMT-Advanced
standardization. IEEE 802.16m is one of the major candidates for IMT-Advanced
technologies by ITU. Among many enhancements, IEEE 802.16m systems can provide
four times faster data speed than the current Mobile WiMax Release 1 based on IEEE
802.16e technology.
Mobile WiMax Release 2 will provide strong backward compatibility with Release 1
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solutions. It will allow current Mobile WiMax operators to migrate their Release 1
Solutions to Release 2 by upgrading channel cards or software of their systems. Also, the
subscribers who use currently available Mobile WiMax devices can communicate with
new Mobile WiMax Release 2 systems without difficulty.
It is anticipated that in a practical deployment, using 4X2 MIMO in the urban micro cell
scenario with only a single 20 MHz TDD channel available system wide, the 802.16m
system can support both 120 Mbit/s downlink and 60 Mbit/s uplink per site
simultaneously. It is expected that the WiMax Release 2 will be available commercially in
the 2011-2012 time frame The goal for the long-term evolution of WiMax is to achieve
100 Mbit/s mobile and 1 Gbit/s fixed-nomadic bandwidth as set by ITU for 4G NGMN
(Next Generation Mobile Network).
5.3 Applications of Wimax
Fixed Wireless (IEEE 802.16-2004) Applications Perhaps the most lucrative
application for WiMax is that of substitute for the telephone company's copper wire.
This is achieved through fixed wireless solutions. A majority of US
Figure 5.1 WiMax offers a substitute for the telephone company's T1/E1 or DS3
businesses and residences receive their telephone service and internet access via the
53
Telephone company's copper wires. A T1 data line from the telephone company may re-
tail for $800/month in many US cities. About 50% of that expense is "local loop" charges
or paying to use the telephone company's copper wire to access a wider network. As the
diagram below illustrates, a WiMax service provider could purchase the bandwidth
equivalent of a T1 (1.54 Mbps) at, say, $45 and resell to an enterprise customer for $400.
WiMax VoIP
A fixed wireless solution not only offers competitive internet access, it can do the same for
telephone service thus further bypassing the telephone company's copper wire network.
Voice over Internet Protocol (VoIP) offers a wider range of voice services at reduced cost
to subscribers and service providers alike. The diagram below illustrates a typical solution
where a WiMax service provider can obtain wholesale VoIP services (no need for the
WiMax service provider to install and operate a VoIP soft switch) at about
$5/number/month and resell to enterprise customers at $50 In residential markets, VoIP is
Figure 5.2: WiMax application in VoIP is the "killer app" for WiMAX
54
a "must offer" service. Without the additional revenue per user (think ARPU where "A" is
for average), WiMax does not offer a compelling reason to switch from other forms of
residential broadband. When bundled with broadband internet access and IPTV, a WiMax
triple play becomes very attractive to residential subscribers. Given the QoS, security and
reliability mechanisms built into WiMax, sub-scribers will find WiMax VoIP is good
1. WiMax& IPTV The third leg of the triple play is Internet Protocol Television
(IPTV). IPTV enables a WiMax service provider to offer the same programming as
cable or satellite TV service providers. IPTV, depending on compression algorithms,
requires at least 1 Mbps of bandwidth between the WMAX base station and the
subscriber.
In addition to IPTV programming, the service provider can also offer a variety of
video on demand (VoD) services. The subscriber can select programming a la carte
for their television, both home and mobile, viewing needs. This may be more
desirable to the sub-scriber as they pay only for what they want to watch as opposed
to having to pay for dozens of channels they don't want to watch. IPTV over WiMax
also enables the service provider to offer local programming as well as revenue
generating local advertising.
Figure 5.3: IPTV and Video on Demand enable a WiMAX service provider to offer
programming identical to cable and satellite providers
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WiMax Mobile Applications (802.16e)
In order to execute a true quadruple play strategy, a service provider will need to offer
mobile services. Even though it's called "mobile", 802.16e-2005 offers a number of ad-
vantages to the fixed wireless market as well. Better building penetration as well as im-
provements in security and QoS point to a strategy of "one network serves all".
1 WiMax as cellular alternative of all the sub industries in telecommunications, perhaps
the one best positioned to take advantage of WiMax is the cellular service providers. They
have a lot going for them including a wireless culture (RF engineers, wireless savvy sales
staff, etc) and millions of "early adaptor" customers. On the other hand, the transition from
legacy circuit switching and a dependency on the incumbent telephone service provider's
network will not be easy or inexpensive As the diagram below supports a large percentage
of a cell phone operator's monthly operating expense (OPEX) is T1 backhaul to
support their base stations. In addition, they use aging circuit switches (Class 4 and 5 as
well as Mobile Switching Centers) to switch phone calls. These come with expensive
annual service contracts. A WiMax substitute for the cell phone infrastructure could be
operated at as little as 10% of the OPEX of a cellular operator using legacy infrastructure.
Source: Trendsmedia Replacing a cell phone infrastructure with WiMax will need to
Figure 5.4: The cellular network is a mixture of wireless and PSTN architectures
56
incorporate a large mo-bile data and mobile TV element with it as data bandwidth
demands on the system will be far greater than what is now seen with a voice-centric cell
phone network. The diagram below provides a high overview of a converged voice and
data wireless network. to come to mind is cell phone service which is a huge industry
Figure 5.5: Perhaps the most immediate application for mobile WiMax
in itself. However, mobile now connotes a wide range of services be-yond voice to
include mobile data and TV, as well as emergency services
Figure 5.6: WiMAX as a mobile voice and data network
A wireless operator will want to pay close attention to their ARPU while minimizing their
OPEX. WiMax allows an operator to do both simultaneously. Failure to update a legacy
network could put an operator at risk of losing business to new market entrants armed with
WiMax.
57
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