`Understanding Broadband Wireless Networking
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`Page 1 of 51
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`Jeffrey G. Andrews + Arunabha Ghosh + Rias Muhamed
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`Prentice Hall Communications Engineering and Emerging Technologies Series
`CM MLUCNMCI)em Yee TCD
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`ZyXEL Communications Corporation Ex. 1005
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`Understanding Broadband Wireless Networking
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`Fundamentals of WiMAX
`
`yeneration
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`Jeffrey G. Andrews, Ph.D.
`
`Departmentof Electrical and Computer Engineering
`The University of Texas at Austin
`
`Arunabha Ghosh, Ph.D.
`
`AT&T Labs Inc.
`
`Rias Muhamed
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`AT&T Labs Inc.
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`nulation
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`2ption
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`ee
`eo
`eePRENTICE
`LL
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`PERKINS COIE |
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`Library of Congress Cataloging-in-Publication Data
`Andrews, Jeffrey G.
`Fundamentals of WiMAX :
`Muhamed.
`p.cm,
`
`understanding broadband wireless networking / Jeffrey G. Andrews. Arunabha Ghosh, Rias
`
`Includes bibliographical references and index.
`ISBN 0-13-222552-2 (hbk : alk. puper)
`1. Wireless communication systems, 2. Broadb:
`Title.
`TK5103.2.456 2007
`621,382—de22
`
`and communication systems.
`
`I, Ghosh, Arunabha.Il. Muhamed, Rias.II.
`
`Copyright © 2007 Pearson Education, Inc
`All rights reserved. Printed in the United States ofAmerica. This publication is protected by copyright, and permission must
`be obtained from the publisher prior to any prohibited repreduction storage in a retrieval system, or transmission in any
`form or by any means, electronic, mechanical, photocopying, recording, or likewise, For information regarding permissions,
`write tor
`Pearson Education, Inc,
`Rights and Contracts Department
`One Lake Street
`UpperSaddle River, NJ 07458
`Fax: (201) 236-3290
`ISBN 0-13-222552-2
`
`2006038505
`
`Text printed in the United States on recycled paper at Courier in Westford, Massachusetts
`
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`Introduction to Broadband
`Wireless
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`roadband wireless sits at the confluence of two of the most remarkable growth stories ofthe
`
`B 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 sub-
`scribers worldwide in 1990 to morethan 2 billion in 2005 [1]. During the sameperiod,the Inter-
`net 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 [2]. Will combining the convenience of wire-
`less with the rich performance of broadbandbe 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 endusers? Manyindustry observers believeso.
`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 oyercoaxial cable TV plant, are the predom-
`inant mass-market broadband access technologies today, Both of these technologies typically
`Provide up to a few megabits per secondofdata to each user, and continuing advances are mak-
`ing several tens of megabits per secondpossible. Since their initial deploymentin the late 1990s,
`these services have enjoyed considerable growth. The United States has more than 50 million
`broadband subscribers, including more than half of homeInternet users. Worldwide, this num-
`ber is more than 200 million today and is projected to grow to more than 400 million by 2010
`[2]. The availability of a wireless solution for broadband could potentially accelerate this
`growth.
`Whatare the applicationsthatdrive this growth? Broadbandusers worldwide are finding that
`it dramatically changes how we share information, conduct business, and seek entertainment.
`
`Abies.
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`Figure 1.1 Worldwide subscriber growth 1990-2006 for mobile telephony,Internet usage, and
`broadband access[1, 2, 3]
`Broadband access not only provides faster Web surfing and quicker file downloads but also
`enables several multimedia applications, such as real-time audio and video streaming, multimedia
`conferencing, and interactive gaming. Broadband connections are also being used for voicetele-
`phony using voice-over-Internet Protocol (VoIP) technology. More advanced broadband access
`P
`systems, such as fiber-to-the-home (FTTH) and very high data rate digital subscriber loop
`b
`(VDSL), enable such applications as entertainment-quality video, including high-definition TV
`9
`(HDTV) and video on demand (VoD). As the broadband market continues to grow, several new
`
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`applications are likely to emerge, and it is difficult to predict which ones will succeed in the
`5
`future.
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`b
`So what is broadband wireless? Broadbandwireless is about bringing the broadband experi-
`s
`ence to a wireless context, which offers users certain unique benefits and convenience. There are
`
`‘|
`two fundamentally different types of broadbandwireless services. Thefirst type attempts to pro-
`
`vide a set of services similar to that of the traditional fixed-line broadband but using wireless as
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`the medium of transmission. This type, called fixed wireless broadband, can be thought of as a
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`competitive alternative to DSL or cable modem. The second type of broadband wireless, called
`
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`mobile broadband,offers the additional functionality of portability, nomadicity,! and mobility.
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`Mobile broadband attempts to bring broadbandapplications to new user experience scenarios |
`
`|*
`and hencecanoffer the end user a very different value proposition. WiMAX (worldwide interop-
`
`erability for microwave access) technology, the subject of this book, is designed to accommo-
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`PI
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`speeds.
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`For example, in February 1997, AT&T announced that it had developed a wireless access system
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`Wireless
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`1.1 Evolution of Broadband Wireless
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`5
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`In this chapter, we provide a brief overview of broadband wireless. The objective is to
`present the the background and context necessary for understanding WiMAX. Wereview the
`history of broadband wireless, enumerate its applications, and discuss the business drivers and
`challenges. In Section 1.7, we also survey the technical challenges that need to be addressed
`while developing and deploying broadband wireless systems,
`
`1.1 Evolution of Broadband Wireless
`The history of broadband wireless as it relates to WiMAX can be traced back to the desire to
`find a competitive alternative to traditional wireline-access technologies. Spurred by the deregu-
`lation of the telecom industry and the rapid growth ofthe Internet, several compctitive carriers
`were motivated to find a wireless solution to bypass incumbentservice providers. During the
`past decade orso, a number of wireless access systems have been developed, mostly by start-up
`companies motivated by the disruptive potential of wireless. These systems varied widely in
`their performance capabilities, protocols, frequencyspectrum used, applications supported, and
`a host of other parameters. Some systems were commercially deployed only to be decommis-
`sioned later. Successful deployments have so far been limited to a few niche applications and
`markets. Clearly, broadband wireless has until now had a checkered Tecord, in part because of
`the fragmentation of the industry due to the lack of a common standard. The emergence of
`WiMAXasan industry standard is expected to change this situation.
`Given the wide variety of solutions developed and deployed for broadbandwireless in the
`past, a full historical survey of these is beyond the scope ofthis section. Instead, we provide a
`bricf review of some ofthe broader patterns in this development, A chronological listing of some
`of the notable events related to broadband wircless developmentis given in Table 1.1,
`WiMAXtechnology has evolved through four stages, albeit not fully distinet or clearly
`sequential: (1) narrowband wireless local-loop systems, (2) first-generation line-of-sight (LOS)
`broadband systems, (3) second-generation non-line-of-sight (NLOS) broadband systems, and
`(4) standards-based broadband wireless systems.
`
`ee
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`1.1.1 Narrowband Wireless Local-Loop Systems
`Naturally, the first application for which a wireless alternative was developed and deployed was
`voice telephony. These systems, called wireless local-leop (WLL), were quite successful in
`developing countries such as China, India, Indonesia, Brazil, and Russia, whose high demand
`for basic telephone services could not be served using existing infrastructure. In fact, WLL sys-
`tems based on the digital-enhanced cordless telephony (DECT) and code division multiple
`access (CDMA)standardscontinue to be deployed in these markets.
`In markets in which a robust local-loop infrastructure already existed for voice telephony.
`WLLsystems had to offer additional value to be competitive. Following the commercialization
`of the Internet in 1993, the demand for Internet-access services began to surge, and many saw
`Providing high-speed Internet-access as a way for wireless systems to differentiate themselves.
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`for the 1,900MHz PCS (personal communicationsservices) band that could deliver two voice
`lines and a 128kbps data connection to subscribers. This system, developed under the code name
`“Project Angel,” also had the distinction of being one ofthe first commercial wireless systemsto
`use adaptive antenna technology. Afterfield trials for a few years and a brief commercial offer-
`ing, AT&T discontinuedthe service in December 2001, citing cost run-ups and poortake-rate as
`reasons.
`
`During the sametime, several small start-up companies focused solely on providing Inter-
`net-access services using wireless. These wireless Internet service provider (WISP) companies
`typically deployed systems in the license-exempt 900MHz and 2.4GHz bands. Most of these
`systems required antennasto be installed at the customer premises, cither on rooftops or under
`the eaves oftheir buildings. Deployments werelimited mostly to select neighborhoods and small
`towns. These early systems typically offered speeds up to a few hundred kilobits per second.
`Later evolutionsoflicense-exempt systems were able to provide higher speeds.
`
`1.1.2 First-Generation Broadband Systems
`As DSL and cable modemsbeganto be deployed, wireless systems had to evolve to support
`much higher speeds to be competitive. Systems began to be developed for higher frequencies,
`such as the 2.5GHz and 3.5GHz bands. Very high speed systems, called local multipoint distri-
`bution systems (LMDS), supporting up to several hundreds of megabits per second, were also
`developed in millimeter wave frequency bands, such as the 24GHz and 39GHz bands. LMDS-
`based services were targeted at businessusers andin the late 1990s enjoyed rapid but short-lived
`success. Problems obtaining access to rooftops for installing antennas, coupled with its shorter-
`range capabilities, squashed its growth.
`Tn the late 1990s, one of the more important deployments of wireless broadband happened
`in the so-called multichannel multipoint distribution services (MMDS) band at 2.5GHz. The
`MMDSband washistorically used to provide wireless cable broadcast video services, especially
`in rural areas where cable TV services were not available. The adventofsatellite TV ruined the
`wireless cable business, and operators were Jooking for alternative waysto use this spectrum. A
`few operators began to offer one-way wireless Internet-access service, using telephoneline as
`the return path. In September 1998, the Federal Communications Commission (FCC) relaxed
`the rules of the MMDSbandin the United States to allow two-way communication services,
`sparking greater industry interest in the MMDS band. MCI WorldCom and Sprint each paid
`approximately $1 billion to purchase licenses to use the MMDS spectrum, and several compa-
`mes started developing high-speed fixed wireless solutions for this band.
`Thefirst generation of these fixed broadband wireless solutions were deployed using the
`same towersthat served wireless cable subscribers. These towers were typically several hundred
`feettall and enabled LOS coverage to distances up to 35 miles, using high-power transmitters.
`First-generation MMDS systems required that subscribers install at their premises outdoor
`antennas high enough and pointed toward the tower for a clear LOS transmission path. Sprint
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`Table 1.1 Important Dates in the Development of Broadband Wireless
`¢ two voice
`Date
`Event
`code name
`AT&T announces developmentoffixed wireless technology code named “Project
`iets
`February 1997 eagel
`cial offer-
`‘ake-rate as |
`FCCauctions 30MHzspectrum in 2.3GHz bandfor wireless communications services
`February 1997
`(WCS)
`American Telecasting (acquired later by Sprint) announceswireless Internet access
`September 1997
`services in the MMDS band offering 750kbps downstream with telephonedial-up
`modem upstream
`September 1998
`FCCrelaxes rules forMMDSbandto allow two-waycommunications
`
`:
`;
`5
`
`April 1999
`MCI andSprint acquire several wireless cable operators to get access to MMDS
`spectrum
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`July 1999
`First working group meeting of IEEE 802,16 group
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`March 2000
`AT&Tlaunchesfirst commercial high-speed fixed wireless service after years oftrial
`
`May 2000
`Sprint launches first MMDS deployment in Phoenix, Arizona, using first-generation
`LOStechnology
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`June 2001
`1 WiMAX Forum established
`
`October 2001
`Sprint halts MMDS deployments
`
`December 2001 AT&T discontinues fixed wireless services
`December2001
`IEEE 802.16 standards completed for> 11GHz.
`
`
`February 2002
`Koreaallocates spectrum in the 2.3GHzband for wireless broadband (WiBro)
`
`January 2003
`IEEE 802.16a standard completed
`
`June 2004
`IEEE 802. 16-2004 standard completed and approved
`
`September 2004
`Intel begins shipping the first WiMAX chipset, called Rosedale
`December 2005
`IEBFE 802.16e standard completed and approved
`
`
`January 2006
`First WiMAX Forum-certified product announced forfixed applications
`
`June 2006
`WiBro commercial services launched in Korea
`
`August 2006
`Sprint Nextel announcesplansto deploy mobile WiMAX in the United States
`in a few markets in early 2000. The outdoor antenna and LOS requirements proved to be signifi-
`cant impediments. Besides, since a fairly large area was being served by a single tower, the
`Capacity of these systems was fairly limited. Similar first-generation LOS systems were
`deployedinternationally in the 3.5GHzband.
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`dand Wireless
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`1.1 Evolution of Broadband Wireless
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`1.1.3 Second-Generation Broadband Systems
`Second-generation broadbandwireless systems were able to overcome the LOS issue and to pro-
`vide more capacity. This was done throughthe use of a cellular architecture and implementation
`of advanced-signal processing techniques to improve the link and system performance under
`multipath conditions. Several start-up companies developed advancedproprietary solutions that
`provided significant performance gains over first-generation systems. Most of these new sys-
`tems could perform well under non-line-of-sight conditions, with customer-premise antennas
`typically mounted underthe eaves or lower. Many solved the NLOSproblem byusing such tech-
`niques as orthogonal frequency division multiplexing (OFDM), code division multiple access
`(CDMA), and multiantenna processing. Some systems, such as those developed by SOMA Net-
`works and Navini Networks, demonstrated satisfactory link performance over a few miles to
`desktop subscriber terminals without the need for an antenna mounted outside. A few megabits
`per second throughput over cell ranges of a few miles had become possible with second-
`generation fixed wireless broadband systems.
`
`1.1.4 Emergence of Standards-Based Technology
`In 1998, theInstitute of Electrical and Electronics Engineers (IEEE) formed a group called
`802.16 to develop a standard for what was called a wireless metropolitan area network, or wire-
`less MAN.Originally, this group focused on developing solutions in the 10GHz to 66GHz band,
`with the primary application being delivering high-speed connections to businesses that could
`not obtain fiber. These systems, like LMDS, were conceived as being able to tap into fiber rings
`andto distribute that bandwidth through a point-to-multipoint configuration to LOS businesses.
`The IEEE 802.16 group produced a standard that was approved in December 2001. This stan-
`dard, Wireless MAN-SC,specified a physical layer that used single-carrier modulation tech-
`niques and a media access control (MAC) layer with a burst time division multiplexing (TDM)
`structure that supported both frequency division duplexing (FDD) and time division duplexing
`(TDD).
`After completing this standard, the group started work on extending and modifying it to
`work in both licensed and license-exempt frequencies in the 2GHz to 11GHz range, which
`would enable NLOS deployments. This amendment, IEEE 802.16a, was completed in 2003,
`with OFDM schemes added as part of the physical layer for supporting deploymentin multipath
`environments, By this time, OFDM hadestablished itself as a methodof choicefor dealing with
`multipath for broadband and wasalready part of the revised IEEE 802.11 standards. Besides the
`OFDMphysical layers, 802.16a also specified additional MAC-layer options, including support
`for orthogonal frequency division multiple access (OFDMA).
`Furtherrevisions to 802.16a were made and completed in 2004. This revised standard, IEEE
`802.16-2004,replaces 802.16, 802.16a, and 802.16c with a single standard, whichhasalso been
`adopted as the basis for HIPERMAN(high-performance metropolitan area network) by ETST
`(European Telecommunications Standards Institute). In 2003, the 802.16 group began work on
`enhancements to the specifications to allow vehicular mobility applications. That revision,
`
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`1 4 Evolution of Broadband Wireless
`9
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`Sidebar 1.1 A Brief History of OFDM
`
`Although OFDM has become widely used only recently, the concept dates
`back some 40 years. This brief history of OFDM cites some Jandmarkdates.
`
`1966: Chang shows that multicarrier modulation can solve the multipath
`problem without reducing data rate [4]. This is generally considered
`the first official publication on multicarrier modulation. Someearlier
`work was Holsinger’s 1964 MIT dissertation [5] and some of Gal-
`lager’s early work on waterfilling [6].
`1971: Weinstein and Ebert show that multicarrier modulation can be
`accomplished using a DFT [7].
`1985: Cimini at Bell Labs identifies many of the key issues in OFDM
`transmission and does a proof-of-conceptdesign[8].
`following
`1993: DSL adopts OFDM,
`also called discrete multitone,
`successfulfield trials/competitions at Bellcore versus equalizer-based
`systems.
`1999: The IEEE 802.11 committee on wireless LANsreleases the 802.1la
`standard for OFDM operation in SGHz UNIband.
`2002: The [EEE 802.16 committee releases an OFDM-based standard for
`. wireless broadband access for metropolitan area networks underrevi-
`sion 802.16a.
`2003: The IEEE 802.11 committee releases the 802.11g standard for opera-
`tion in the 2.4GHz band.
`2003: The multiband OFDMstandard for ultrawideband is developed, show-
`ing OFDM’susefulness in low-SNR systems.
`
`
`
`:o Broadband Wireless
`
`S issue andto pro-
`ad implementation
`verformance under
`tary solutions that
`of these new sys-
`-premise antennas
`y using such tech-
`n multiple access
`:d by SOMA Net-
`er a few miles to
`2. A few megabits
`ble with second-
`
`d a group called
`network, or wire-
`z to 66GHzband,
`nesses that could
`
`ip into fiber rings
`LOSbusinesses.
`2001. This stan-
`modulation tech-
`tiplexing (TDM)
`vision duplexing
`
`modifying it to
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`npleted in 2003,
`rent in multipath
`for dealing with
`irds. Besides the
`icluding support
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`1 standard, IEEE
`ch has also been
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`802.16¢, was completed in December 2005 and was published formally as TERE 802.16e-2005.
`It specifies scalable OFDM forthe physical layer and makes further modifications to the MAC
`layer to accommodate high-speed mobility.
`As it turns out, the IEEE 802.16 specifications are a collection of standards with a very
`broad scope. In order to accommodate the diverse needs of the industry, the standard incorpo-
`rated a wide variety of options. In order to develop interoperable solutions using the 802.16 fam-
`ily of standards, the scope of the standard had to be reduced by establishing consensus on what
`Optionsof the standard to implement andtest for interoperability. The IEEE developedthe spec-
`ifications butleft to the industry the task of converting them into an interoperable standard that
`can be certified. The WiMAX Forum was formedto solvethis problem and to promote solutions
`based on the IEEE 802.16 standards. The WiMAX Forum was modeled along the lines of the
`Wi-Fi Alliance, which has had remarkable success in promoting and providing interoperability
`testing for products based on the IEEE 802.11 family of standards.
`The WiMAX Forum enjoys broad participation from the entire cross-section of the industry,
`
`twork) by ETSI
`' began work on
`That revision,
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`including semiconductor companies, equipment manufacturers, system integraters, and service
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`° Introduction to Broadband Wireless
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`providers. The forum has begun interoperability testing and announcedits first certified product
`based on IEEE 802.16-2004 forfixed applications in January 2006. Preducts based on IEEE
`802.18e-2005 are expected to be certified in early 2007. Manyof the vendors that previously
`developed proprietary solutions have announced plans to migrate to fixed and/or mobile
`WiMAX.Thearrival of WiMAX-certified products is a significant milestone in the history of
`broadbandwireless.
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`1.2 Fixed BroadbandWireless: Market Drivers and Applications
`Applications using a fixed wireless solution can be classified as point-to-point or point-to-multi-
`point. Point-to-pointapplications include interbuilding connectivity within a campus and micro-
`wave backhaul. Point-to-multipoint applications include (1) broadband for residential, small
`office/home office (SOHO), and small- to medium-enterprise (SME) markets, (2) Tl orfrac-
`tional T1-like services to businesses, and (3) wireless backhaul for Wi-Fi hotspots. Figure 1.2
`illustrates the various point-to-multipoint applications.
`Consumer and small-business broadband: Clearly, one of the largest applications of
`WiMAXin the near future is likely to be broadband access for residential, SOHO, and SME
`markets. Broadband services provided using fixed WiMAX. could include high-speed Internet
`access, telephony services using voice over IP, and a host of other Internet-based applications.
`Fixed wireless offers several advantages over traditional wired solutions. These advantages
`include lower entry and deploymentcosts; faster and easier deployment andrevenuerealization;
`ability to build out the network as needed: lower operational costs for network maintenance,
`management, and operation; and independence from the incumbentcarriers.
`From a customer premise equipment (CPE) or subscriber station (SS) perspective, two
`types of deployment models can be usedfor fixed broadbandscrvices to the residential, SOHO,
`and SME markets. One model requires the installation of an outdoor antenna at the customer
`premise; the other uses an all-in-one integrated radio modem that the customer can install
`indoorslike traditional DSL or cable modems, Using outdoor antennas improvesthe radio link
`and hence the performance of the system. This model allows for greater coverage area per base
`Station, which reduces the density of base stations required to provide broadband coverage,
`thereby reducing capital expenditure. Requiring“an outdoor antenna, however, meansthatinstal-
`lation will require a truck-roll with a trained professional and also implies a higher SS cost.
`Clearly, the two deploymentscenarios showa trade-off between capital expenses and operating
`expense: between basestation capital infrastructure costs and $$ and installation costs. In devel-
`oped countries, such as the United States, the high labor cost of truck-roll, coupled with con-
`sumer dislike for outdoorantennas, will likely favor an indoor SS deployment, at least for the
`
`residential application. Further, an indoorself-install SS will also allow a business modelthat
`can exploit the retail distribution channel and offer consumers a variety of SS choices. In devel-
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`2. The CPEis referred to as a subscriberstation (SS) in fixed WiMAX.
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`and Wireless
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`1.2 Fixed Broadband Wireless: Market Drivers and Applications
`11
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`so powerful, an outdoor-SS deployment model may make more economic sense.
`In the United States and other developed countries with good wired infrastructure, fixed
`wireless broadband is more likely to be used in rural or underserved areas, where traditional
`meansof serving them is more expensive. Services to these areas may be provided by incumbent
`telephone companies or by smaller players, such as WISPs, or local communities and utilities. It
`is also possible that competitive service providers could use WiMAX to compete directly with
`DSLand cable modem providers in urban and suburbaw markets.In the United States, the FCC’s
`August 2005 decision to rollback cable plant sharing needs is likely to increase the appeal of
`fixed wireless solutions to competitive providersas they look for alternative means to reach sub-
`scribers. The competitive landscape in the United States is such that traditional cable TV compa-
`nies and telephone companies are competingto offer a full bundle of telecommunications and
`entertainment services to customers.In this environment,satellite TV companies may be pushed
`to offering broadband services including voice and data in order to stay competitive with the
`telephone and cable companies, and may
`look to WiMAX asa potential solution to achievethis.
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`business market. Given that only a small fraction of commercial buildings worldwide have
`
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`access to fiber, there is a clear need for alternative high-bandwidth solutions for enterprise
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`Chapter
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`« Introduction to Broadband Wireless
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`customers. In the business market, there is demand for symmetrical T1/E1 services that cable
`and DSL have so far not met the technical requirements for. Traditional telco services continue
`to serve this demand withr