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© John Moring 2007-2008
Fundamentals of
WiMAX
Broadband Wireless AccessTechnology
May 2008
John Moring
www.moring.net
760-633-1790
John Moring
www.moring.net
760-633-1790
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©2007-2008 John Moring page 2
WiMAXMay 2008
Objectives
Familiarity with available standards and their scope
Understanding of WiMAX related to competingtechnologies
View of work in progress
Overview of features and capabilities
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©2007-2008 John Moring page 3
WiMAXMay 2008
Outline
WiMAX Intro - 1 hour
Overview
What is WiMAX?
Industry activities
WiMAX Technology - 1 hour
Technology overview
802.16 elements
Technology featuresEquipment characteristics
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©2007-2008 John Moring page 4
WiMAXMay 2008
Overview
What is WiMAX?
Broadband wireless access
Competition
Industry activities
IEEE
WiMAX Forum
Industry
Technology overviewSpectrum
OSI/IEEE model IEEE: Institute of Electrical and Electronics Engineers
OSI: Open System Interconnect
IEEE: Institute of Electrical and Electronics Engineers
OSI: Open System Interconnect
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WiMAXMay 2008
Overview
802.16 elements
MAC sublayers
• Service-specific convergence
• MAC common part
• Security
PHY options
• Single carrier, OFDM, OFDMA
• Line of sight (10+ GHz),• Non-line of sight (
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©2007-2008 John Moring page 6
WiMAXMay 2008
Overview
Technology features
Topology, symmetry, duplex, TDD, FDD
Quality of service (QoS)
Security• Encryption
• Authentication
Reliability• Forward error correction (FEC)
• Automatic repeat request (ARQ)
• Adaptive modulation and coding
TDD: time division duplex
FDD: frequency division duplex
TDD: time division duplex
FDD: frequency division duplex
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WiMAXMay 2008
Overview
Performance
Propagation & coverage
Throughput
Capacity, frequency planning
Advanced featuresMesh
MobilityMIMO
Advanced antenna systems
MIMO: multiple input, multiple output MIMO: multiple input, multiple output
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WiMAXMay 2008
What is WiMAX?
A marketing term…
WiMAX Forum
“Worldwide Interoperability for Microwave Access”
…representing the IEEE 802.16 standards…
“Air Interface for Fixed and Mobile Broadband
Wireless Access Systems”
“WirelessMAN®”
…for a broadband wireless access (BWA)technology supporting multimedia services
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©2007-2008 John Moring page 9
WiMAXMay 2008
WiMAX Targets Multiple Markets
Last mile connectivityDSL/cable alternative
BackhaulT-1/microwave alternative
Mobility/portability3G cellular/Wi-Fi alternative
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©2007-2008 John Moring page 10
WiMAXMay 2008
WiMAX Employs Familiar Components
Base
Station
(BS)
D o w n l i n k ( D L )
Backhaul
Fixed
Subscriber
Station
(SS)
Mobile
Subscriber
Station
(MS)
U p l i n k
( U L )
Infrastructure
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WiMAXMay 2008
802.16 Covers Lowest 1.5 OSI Layers
User/program interface
User information format
Management of sessions
End to end reliability
(e.g., TCP)
End to end delivery(e.g., IP)
Point to point delivery
Electrical, mechanical 1. Physical
6. Presentation
7. Application
5. Session
4. Transport
3. Network
2. Data Link
802.16
802.16 specifies layers 1 (PHY) and part of Layer 2
Can support any higher layer protocols and services
Medium Access Control
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©2007-2008 John Moring page 12
WiMAXMay 2008
Competition
A number of broadband access technologies exist
DSL
Cable
T1/T3
Fiber
Microwave
Satellite
Cellular
Wi-Fi
Proprietary technologies
What distinguishes WiMAX?
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WiMAXMay 2008
Bluetooth
802.11
Short range
ZigBee
Wireless Data Landscape
103 bps
106 bps
109 bps
1 m 1 km 1000 km
COVERAGE ZONE
T H R O U
G H P U T
bps: bits per second
G: generation
LEO: low earth orbit
VSAT: very small aperture [satellite] terminal
bps: bits per second
G: generation
LEO: low earth orbit
VSAT: very small aperture [satellite] terminal
Fixed wireless
VSAT
WiMAX
Microwave
Paging
Wide area
LEO
satellite
3G Cellular WiMAX
2G Cellular
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©2007-2008 John Moring page 14
WiMAXMay 2008
Metrics
Capacity
Throughput
Coverage
Mobility
Quality of ServiceSecurity
Reliability
Costs
Availability/maturity
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©2007-2008 John Moring page 15
WiMAXMay 2008
What Distinguishes WiMAX?
Wide area, wireless, broadband, point tomultipointMobility option
Mesh option
Multiple frequency bands, including unlicensedFlexible & efficient use of spectrum
• Advanced, adaptive modulation• Adaptive antenna technologies
Multi-vendor interoperability
Economies of scale (expected)Inherent quality of service (QoS)
Carrier-grade security
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WiMAXMay 2008
WiMAX vs Wi-Fi
Longer range
More spectrum options
Quality of service
Mobility
Richer security features
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©2007-2008 John Moring page 17
WiMAXMay 2008
WiMAX vs Cellular
Better channel efficiency
More flexible quality of service
Potentially better economies of scale
In the cellular arena, WiMAX faces LTE
(Long Term Evolution) being
standardized by 3GPPChosen by AT&T, Verizon, Ericsson, etc.
3GPP: third generation partnership project 3GPP: third generation partnership project
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©2007-2008 John Moring page 18
WiMAXMay 2008
WiMAX vs Proprietary
Standards-based
Confidence
Multi-vendor interoperability
Economies of scale
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WiMAXMay 2008
Tradeoffs
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WiMAXMay 2008
Representative Performance
Source: WiMAX Forum
“WiMAX Deployment Considerations for Fixed Wireless Access in the 2.5 GHz and 3.5 GHz Licensed Bands”
Simulation results for 3.5GHz band, paired 3.5 MHz FDD channel
Fixed user devices
Average shared downlink throughput, per channel, includingoverhead
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©2007-2008 John Moring page 21
WiMAXMay 2008
The Many Faces of WiMAX
Fixed / mobile
Line of sight / non-line of sightDifferent bands and channel bandwidths
Licensed / unlicensed spectrum Frequency division / time division / half-duplex
frequency division channel usage
Single carrier / OFDM / OFDMA
Plus many configurable optionsSecurity
Reliability
Advanced antennasEtc.
“Profiles” collect reasonable feature sets forcertification and interoperability
OFDM : orthogonal frequency division multiplexing
OFDMA: orthogonal frequency division multiple access
OFDM : orthogonal frequency division multiplexing
OFDMA: orthogonal frequency division multiple access
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©2007-2008 John Moring page 22
WiMAXMay 2008
WiMAX Features Related to Spectrum
NLOS
OFDM, OFDMA, SC
Licensed, unlicensed
Fixed
LOS
Single carrier
Mostly licensed
Fixed
6 G H z
6 6 G H z
LOS: line of sight
NLOS: non-line of sight
OFDM: orthogonal frequency division multiplex
OFDMA: orthogonal frequency division multiple access
SC: single carrier
LOS: line of sight
NLOS: non-line of sight
OFDM: orthogonal frequency division multiplex
OFDMA: orthogonal frequency division multiple access
SC: single carrier
2 G H z
Mobile
OFDMA
1 1 G H z
1 0 G H z
Added
2004
Added
2005
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©2007-2008 John Moring page 23
WiMAXMay 2008
Outline
WiMAX Intro
Overview
What is WiMAX?Industry activities
WiMAX Technology
Technology overview
802.16 elements
Technology features
Equipment characteristics
WiMAX
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WiMAXMay 2008
Industry Activities
Institute of Electrical and Electronics Engineers (IEEE)Standards
802.3 Ethernet, 802.11 Wi-Fi, etc.
802.16 WiMAX
WiMAX ForumIndustry consortium
400+ members
Promotes the technology, defines “profiles,” certifies equipment
International bodies
Major commitments from industry leaders, e.g.,
IntelSprint
Clearwire
Motorola
Etc.
WiMAX
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WiMAXMay 2008
Three Standards Specify Air Interface
IEEE Std 802.16-2004
Encompasses and supercedes
• 802.16-2001, original standard• 802.16a, adds
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WiMAXMay 2008
WiMAX Forum Promotes and Certifies
“The WiMAX Forum® is an industry-led, not-for- profit organization formed to certify and promote thecompatibility and interoperability of broadband
wireless products based upon the harmonized IEEE802.16/ETSI HiperMAN standard.
“A WiMAX Forum goal is to accelerate the
introduction of these systems into the marketplace. “WiMAX Forum Certified™ products are fully
interoperable and support broadband fixed, portable andmobile services.
“Along these lines, the WiMAX Forum works closelywith service providers and regulators to ensure thatWiMAX Forum Certified systems meet customer andgovernment requirements”
www.wimaxforum.org
WiMAX
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WiMAXMay 2008
WiBro Uses 802.16 in Asia
Korean WiBro = Wireless Broadband
“must comply with IEEE 802.16-2004 and
IEEE 802.16e/Draft3 or later versions.”
2.3 GHz band, 8.75 MHz channels
OFDMA, TDD
Mobility ≤60 km/hr
Coverage ≤1 kmPer-user throughput: 128 kbps – 3 Mbps
Nationwide service 4/2007
Multiple carriers100,000+ subscribers by 12/2007
Price per month ~$20
WiMAX
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WiMAXMay 2008
802.16 Also Active in Europe
ETSI HiPerMAN
Subset of IEEE 802.16
Fixed, 2 GHz – 11 GHzSeparate test regime from WiMAX
International Telecommunications Union
Subsets of 802.16 proposed/approved for inclusionin the IMT-2000 family of 3G/4G wireless standards
Approval allows deployment in Europe in bandsreserved for IMT (traditionally cellular)
technologies
3.5 GHz deployments in progress
ETSI – European Telecommunications Standards Institute
HiPerMAN – high performance metro area network IMT – International Mobile Telecommunications
ETSI – European Telecommunications Standards Institute
HiPerMAN – high performance metro area network IMT – International Mobile Telecommunications
WiMAX
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WiMAXMay 2008
Provider Example: Clearwire
Source: Clearwire website 9/07
WiMAX
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May 2008
Example: Clearwire
Clearwire Corporation is unwiring Nashville with the introduction of itsnext-generation wireless broadband solution. The company announcedtoday the official launch of its wireless high-speed Internet access andphone service to the city….
Nashville residents and businesses can now have a fast, simple, portable,reliable and affordable alternative to traditional dial-up, cable andDSL. Clearwire service eliminates the confines of traditional cable ortelephone wiring, allowing customers to connect at home, a localcoffeehouse, the office or virtually anywhere else in the Clearwireservice area.
…Simply purchase a modem at … Circuit City, Best Buy or online atwww.clearwire.com, and within minutes, Internet access or phone servicewill be up and running.
Clearwire’s next-generation, non-line-of-sight wireless broadbandnetwork solution connects customers through licensed or securedspectrum.
… Clearwire Internet Phone Service works with a customer’s existinghigh-speed Internet access and provides unlimited local and long-distance calling from a regular telephone.
Clearwire press release 9/07
Note: Clearwire uses Motorola Expedience “WiMAX-class” technology
WiMAX
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May 2008
Example: Clearwire
Source: Clearwire website 9/07
WiMAX
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May 2008
Vendor Quotes: Intel
“Intel currently plans to integrate WiMAX and WiFi into its
notebook platforms based on Intel® Centrino® Mobile
Technologies. Pairing the two will help bring users the ultimate in
high-speed mobile broadband. Intel believes that WiMAX, with itstechnical and economic advantages, should help enable mainstream
adoption of personal broadband.
“Intel® WiMAX Connection 2250 is a low-cost system-on-chip
that supports IEEE 802.16-2004 and IEEE 802.16e-2005, enablingWiMAX modems for use with fixed or mobile networks.
“The Intel NetStructure® WiMAX Baseband Card integrates
control plane, MAC and PHY processing in a single standards-
based card, ….”
Source: Intel website 9/07
WiMAXM 2008
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May 2008
Provider Quotes: Sprint Nextel
8/8/06. Sprint Nextel Corp. …announced its plans to develop and deploy the firstfourth generation (4G) nationwide broadband mobile network. The 4G wireless broadband network will use the mobile WiMAX IEEE 802.16e-2005 technologystandard.
Working together with Intel, Motorola and Samsung, Sprint Nextel will develop a
nationwide network … designed to offer faster speeds, lower cost, and greaterconvenience and enhanced multimedia quality.
The Sprint Nextel 4G mobility network will use the company's extensive 2.5GHzspectrum holdings, which cover 85 percent of the households in the top 100 U.S.markets …
The company's deployment plans target a launch of the advanced wireless
broadband services in trial markets by the end of 2007 with plans to deploy anetwork that reaches as many as 100 million people in 2008. Sprint Nextel plans toexpand mobile WiMAX network coverage thereafter.
The company will continue to invest in and offer access to its current wireless andSprint PowerVision mobile broadband networks to serve customer communicationsneeds today and into the future.
Sprint Nextel is expecting to invest $1 billion in 2007 and between $1.5 billion and$2 billion in 2008
Motorola and Samsung will also support Sprint's current and CDMA/EV-DOnetwork technologies by creating multimode devices that will support services on both the 4G network and the 3G network … will provide voice service using thecore 3G network.
News services
WiMAXMay 2008
S i O TM
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May 2008
Sprint XOHMTM
Aug. 16 2007 -- Sprint announced today that its WiMAX servicewill be marketed under the XOHMTM ingredient brand(pronounced ZOAM). A soft launch of the WiMAX network isexpected by the end of 2007 in the Chicago and
Baltimore/Washington markets. XOHM commercial services areexpected to be available beginning in the first half of 2008.
... partners have committed to embed 50 million WiMAX chipsetsin devices. The company expects to begin offering 4G mobilebroadband services up to two years ahead of other national
wireless carriers. Sprint Nextel expects to invest approximately $2.5 billion in
capital for WiMAX through year-end 2008. Beyond 2008, network build is expected to be increasingly success-based. The companycurrently expects that extending its coverage to approximately 125
million people by year-end 2010 would require an additionalcapital expenditure of approximately $2.5 billion.….
News services
WiMAXMay 2008
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May 2008
Sprint Quiet on WiMax Launch Date
April 2008 -- Sprint Nextel says provisioning of backhaul is the primary
hold-up to the operator's nationwide deployment of mobile WiMAX.
Sprint, which was supposed to launch its Xohm network this month, is
having difficulty finding high-capacity transport links to connect cell sites
as typical T-1 lines that feed today's mobile networks are inefficient forhigh-speed wireless broadband data, said Xohm President and Sprint
Chief Technology Officer Barry West in an interview with Telephony.
To build the network, Sprint is provisioning fiber where economically
feasible, West said. In other areas, Sprint is using microwave. The entire process has moved slower than what Sprint expected, causing the delay of
the commercial launch.
"Clearly I wanted to hit the April date," West said. "Having missed that
date, I want to make sure we come out with a robust service. Right now
I'm building sites."
WiMAXMay 2008
Ci B WiMAX I f Pl
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May 2008
Cisco Buys WiMAX Infrastructure Player
SAN JOSE, Calif. -- Cisco(R) announced a definitive agreement to purchase Richardson, TX-based Navini Networks, Inc. a leader in theMobile WiMAX 802.16e-2005 broadband wireless industry. Navini is a
pioneer in the integration of "Smart Beamforming" technologies withMulti-Input Multi-Output (MIMO) antennas, a combination that improves
the performance and range for WiMAX services and lowers the overalldeployment and operational costs for service providers….
Cisco also expects that its broadband wireless solution portfolio, that nowincludes WiMAX products, will play a key role in Cisco´s CountryTransformation and "Digital Inclusion" initiatives to drive broadband
penetration to consumers and business in emerging countries. "Emerging country service providers are in expansion mode, building out
broadband wireless networks and are concerned about deployment costsand the availability of skilled resources," said Brett Galloway, vice
president and general manager of the Wireless Networking Business Unit,Cisco. "Around the world broadband wireless networks based uponWiMAX have the potential to add millions of new Internet users whocannot be reached economically using copper or fiber infrastructures.Additionally, WiMAX networks will help drive the transition to open IP-
based broadband wireless architectures and accelerate the rollout of newapplications and services."
Byteandswitch.com 11/07
WiMAXMay 2008
S
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May 2008
Summary
New entrant to crowded market
Large potentialIndustry backing
State of the art technologies
Adaptable to diverse niches
4G in developed marketsLast mile in underdeveloped markets
WiMAXMay 2008
O tli
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May 2008
Outline
WiMAX Intro - 1 hour
What is WiMAX?
Industry activitiesWiMAX Technology - 1 hour
Technology overview
802.16 elements
Technology features
Equipment characteristics
WiMAXMay 2008
Th M F f WiMAX
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y
The Many Faces of WiMAX
Line of sight / non-line of sightDifferent bands and channel bandwidths
Licensed / unlicensed spectrum
Frequency division / time division / half-duplexfrequency division channel usage
Fixed / mobile
Single carrier / OFDM / OFDMA
Plus many configurable optionsSecurity
ReliabilityAdvanced antennas
Etc.OFDM : orthogonal frequency division multiplexing
OFDMA: orthogonal frequency division multiple access
OFDM : orthogonal frequency division multiplexing
OFDMA: orthogonal frequency division multiple access
WiMAXMay 2008
Spectrum Allocation
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y
Spectrum Allocation
3.5 GHzWidely allocated and available for WiMAX in
Europe & elsewhere
2.5 GHzIn US, mostly licensed by Sprint/Clearwire
To be allocated in Europe in 2008
Allocations exist elsewhere5.8 GHzLicensed-free in the US, parts of Europe
Other bands to watch2.3 GHz used for WiBro in Korea
700 MHz, 900 MHz, 3.6 GHz, 5.4 GHz
WiMAXMay 2008
WiMAX Features Related to Spectrum
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WiMAX Features Related to Spectrum
NLOS
OFDM, OFDMA, SC
Licensed, unlicensed
Fixed
LOS
Single carrier
Mostly licensed
Fixed
6 G H z
6 6 G H z
LOS: line of sight
NLOS: non-line of sight
OFDM: orthogonal frequency division multiplex
OFDMA: orthogonal frequency division multiple access
SC: single carrier
LOS: line of sight
NLOS: non-line of sight
OFDM: orthogonal frequency division multiplex
OFDMA: orthogonal frequency division multiple access
SC: single carrier
2 G H z
Mobile
OFDMA
1 1 G H z
1 0 G H z
Added
2004
Added
2005
WiMAXMay 2008
Mobile Network Model
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Mobile Network Model
From WiMAX Forum Network Architecture
Rn designates reference interface
R1 specified in 802.16
AAA: authentication,
authorization, accounting
ASN : access service network
ASP: application service provider
CSN : connectivity service network
GW : gateway
HA: home agent
NAP: network access provider
NSP: network service provider
PF: policy function
AAA: authentication,
authorization, accounting
ASN : access service network
ASP: application service provider
CSN : connectivity service network
GW : gateway
HA: home agent
NAP: network access provider
NSP: network service provider
PF: policy function
ASP
R6
R4
WiMAXMay 2008
Outline
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©2007-2008 John Moring page 43
Outline
WiMAX IntroOverview
What is WiMAX?
Industry activitiesWiMAX TechnologyTechnology overview
802.16 elements
• Protocol model – Service-Specific Convergence Sublayer – MAC Common Part Sublayer
– Security Sublayer
– Physical layer
• ModulationTechnology features
Equipment characteristics
WiMAXMay 2008
Protocol Models
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Protocol Models
802.16 Model
Physical
Presentation
Application
Session
Transport
Network
Data Link
Logical Link
Control 802.2
Physical
Medium
Access
Control
Service-SpecificConvergence Sublayer
Security Sublayer
MAC Common
Part Sublayer
Physical
OSI Model IEEE Model
Note: mappings are approximate
WiMAXMay 2008
Service-Specific Convergence Sublayer
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Service-Specific Convergence Sublayer
Service-Specific Convergence Sublayer (CS)Supports higher layer “services”
• ATM
• Packet – IPv4
– IPv6
– Ethernet
– VLAN
Classify data to the proper MAC connection, preserve or enable QoS, and enable bandwidthallocation; optional header suppression
There may be multiple CS per MAC/PHY
PHYMAC
CS CS
IP ATM
ATM : asynchronous transfer mode
IP: Internet protocol MAC : medium access control
PHY : physical layer
QoS: quality of service
VLAN : virtual local area network
ATM : asynchronous transfer mode
IP: Internet protocol
MAC : medium access control
PHY : physical layer
QoS: quality of service
VLAN : virtual local area network
WiMAXMay 2008
MAC Common Part Sublayer
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MAC Common Part Sublayer
Core MAC functions
Quality of service (QoS) management
Reliability• Dynamic forward error correction (FEC) and
modulation management
• Automatic repeat request (ARQ)
Packet fragmentation/defragmentation
Scheduling
MAC: medium access control MAC: medium access control
WiMAXMay 2008
WiMAX is Connection Oriented
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WiMAX is Connection Oriented
Allows robust QoS
Connection-oriented
A connection, session, or association is formed between the communicating end devices
All circuit technologies
Some packet technologies• "Virtual circuits"
• E.g., TCP, Frame Relay, ATM, WiMAX
vs Connectionless
No association, each packet treated individuallyEthernet, IP, UDP
ATM : Asynchronous Transfer Mode
IP: Internet ProtocolTCP: Transmission Control Protocol
UDP: User Datagram Protocol
ATM : Asynchronous Transfer Mode
IP: Internet Protocol
TCP: Transmission Control Protocol
UDP: User Datagram Protocol
WiMAXMay 2008
Security Sublayer
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Security Sublayer
Encryption
Provides user data privacy
Uses encryption algorithms and crypto keys
Authentication/authorization
Verifies identity of SS
Verifies identity of BS (added in 802.16e)
Uses certificates, digital signatures, trusted third-
party verification
BS: base station
SS: subscriber station
BS: base station
SS: subscriber station
WiMAXMay 2008
Security Features
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Security Features
EncryptionProvides user data privacy
• NOT MAC header or most management messages
Uses encryption algorithms and crypto keys• Traffic encryption key (TEK)
Authentication/authorizationVerifies identity of SS
Verifies identity of BS (added in 802.16e)
Uses certificates, digital signatures, trusted third-partyverification
Key exchangeManagement plane
Control message validation
BS: base station
SS: subscriber station
BS: base station
SS: subscriber station
WiMAXMay 2008
Security Concepts
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Security Concepts
Crypto suites
Triple Data Encryption Standard (3DES)
Advanced Encryption Standard (AES)• Counter Mode with Cipher Block Chaining with Message
Authentication Code Protocol (CCMP)
Privacy Key Management (PKM)
PKMv1PKMv2
• RSA (Rivest, Shamir, Aldeman)
• EAP (Extensible Authentication Protocol)Security Associations (SA)
Holds security info (e.g., keys) for each connection
WiMAXMay 2008
Modulations used in 802.16
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Modulations used in 802.16
Modulation and coding adjusted to adapt to signal path
BPSK
1 bit/symbol
QPSK
2 bits/symbol
16-QAM
4 bits/symbol
64-QAM
8 bits/symbol
256-QAM
16 bits/symbol
-1.5
-1
-0.5
0
0.5
1
1.5
- 1.5 -1 - 0.5 0 0.5 1 1.5
Example: BPSK uses phase shift(here 45º and -135º) to represent2 values
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
- 2 - 1.5 - 1 - 0.5 0 0.5 1 1.5 2
Example: 16-QAM uses both
phase (angle from horizontal) and
amplitude (distance from origin)
phase
a m p l i t u
d e
BPSK : binary phase shift keying
QAM : quadrature amplitude modulationQPSK : quadrature phase shift keying
BPSK : binary phase shift keying
QAM : quadrature amplitude modulation
QPSK : quadrature phase shift keying
WiMAXMay 2008
Outline
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WiMAX Intro
What is WiMAX?
Industry activities
WiMAX Technology
Technology overview
802.16 elements
Technology features• Topology
• Time/frequency division
• Quality of service (QoS)
• Reliability
• Mobility
Equipment characteristics
WiMAXMay 2008
Topologies Illustrated
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p g
Point to point
Point to multipoint
Mesh
Dynamic mobile mesh
Mesh BS
Nodes
Infrastructure
relay
Mesh BS Nodes
Mesh BS
a c t i v e
WiMAXMay 2008
TDD and FDD
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WiMAX includes support for both Frequency DivisionDuplexing (FDD) and Time Division Duplexing (TDD)
FDD
Requires paired channels• Usually licensed• Each unit requires dual transceivers
Good for symmetric traffic
May be full duplex or half duplex at subscriber
TDDSingle shared channel
• Some channel inefficiencies when radio switches betweentransmit and receive
Half duplexMay use fixed or adaptive slot sizes
• Good for asymmetric traffic
WiMAXMay 2008
Single Carrier
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g
One radio channel carries each
transmitter’s signal
P o w e r
Frequency f
Bandwidth (BW)
WiMAXMay 2008
OFDM Employs Subcarriers
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p y
Data
Pilot - reference
Guard – interference avoidance
P o w e r
Frequency
Subcarriers typically ~10 kHz wide
Number of subcarriers related to Fast Fourier Transform (FFT) size
Bandwidth (BW)
OFDM: orthogonal frequency
division multiplexing
OFDM: orthogonal frequency
division multiplexing
WiMAXMay 2008Orthogonal Frequency Division
Multiplexing (OFDM)
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Multiplexing (OFDM)
Essentially sends data over several parallel channels
Provides frequency diversity
Reduces inter-symbol interference
Used in 802.11a/g (Wi-Fi) and elsewhere
Users share the channel via time slots
Data
Split to
subcarriers
AntennaRadio
WiMAXMay 2008
OFDM with TDMA
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U s e r 3
T i m e
Each transmitter’s signal is carried in a series ofrelated subcarriers
One transmitter on the channel at a time
P o w e r
Frequency f 0 f n
U s e
r 2
U s e r 1
OFDM: orthogonal frequency division multiplexingTDMA: time division multiple access
OFDM: orthogonal frequency division multiplexingTDMA: time division multiple access
WiMAXMay 2008Orthogonal Frequency Division Multiple
Access (OFDMA)
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Access (OFDMA)
Subsets of subcarriers are allocated to different usersUplink and downlink
Multiple users may share the channel simultaneously
A superior frequency can be chosen for a given user
User 2Data
Split to
subcarriers
AntennaRadio
User 1
Data
Downlink side illustrated
WiMAXMay 2008
OFDMA
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Each transmitter’s signal is assigned to a subchannel ,
i.e., subset of the available subcarriers
P o w e r
Frequency
User4
T i m e
U s e r 2
User5
User1
User4User1
User3
User5
User3
WiMAXMay 2008
Quality of Service (QoS)
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QoS is required to support the requirements of
different traffic types
Access to the channel is controlled by the BSUnlike Wi-Fi or Ethernet, which use contention
access schemes under control of the stations
BS can efficiently allocate uplink and downlinkresources based on requests from SS
BS: base station
SS: subscriber station
BS: base station
SS: subscriber station
WiMAXMay 2008
Fundamental QoS Metrics
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Throughput
Connection capacity, in bits per second
LatencyConnection delay, in milliseconds (ms)
Jitter
Variability of delay, in milliseconds
How much…
How quick…
How consistent…
WiMAXMay 2008
Robust Reliability Options
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Forward error correction (FEC)
Code rates adapt to link quality
Reed-Solomon (RS)
Optional Block Turbo Codes and Convolutional Turbo Codes
Automatic Repeat Request (ARQ)
MAC Block based
Acknowledgements (ACKs) can be selective or cumulative;standalone or piggybacked
Optional Hybrid ARQ (HARQ)
• Incorporates FEC as well ACKs and resends
WiMAXMay 2008
Mobility
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802.16e introduces the Mobile Station (MS)
class of SS
Moving MS may cross BS coverage boundariesHandover: MS migrates from one BS to another
Break-before-make
Make-before-break • Fast BS switching
• Macro diversity handover
ASN-anchored vs. CSN anchored
ASN: access service network
BS: base station
CSN: connectivity service network SS: subscriber station
ASN: access service network
BS: base station
CSN: connectivity service network
SS: subscriber station
WiMAXMay 2008
Outline
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WiMAX Intro
What is WiMAX?
Industry activitiesWiMAX Technology
Technology overview
802.16 elementsTechnology features
Equipment characteristics
WiMAXMay 2008
Equipment Characteristics
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Subscriber station
Base station
Certification
Antennas
Alvarion BreezeMAX
WiMAXMay 2008
Subscriber Station
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Fixed
Indoor
• Consumer installation
• Inexpensive, low performance
Outdoor
• Technician mounted
• Expensive, high gain, better path
Mobile
Dedicated WiMAX devices (e.g., tablet, phone)
Add on (PC card)
Embedded in multipurpose devices (e.g., PC, phone)
WiMAXMay 2008
Base Station
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Comparable to cellular base stations Indoor equipment
Outdoor equipment
Antenna spec, mounting Technical featuresBand, bandwidth, FDD/TDD, ….
Support for optional features
Management interface CapacitySectors, channels, connections, ….
Performance specsPower, sensitivity, ….
Interfaces
WiMAXMay 2008
WiMAX Forum Certification
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Includes conformance and interoperability tests
Certified equipment must conform to
Specific IEEE 802.16 standard
A particular defined profile
WiMAX Forum test documentation
• System Profiles
• Test Suite Structure (TSS) and Test Purposes (TP)• Protocol/Profile Implementation Conformance Statements (PICS)
Tests must be performed by a Designated Certification
Laboratory
AT4 Wireless (Spain), Telecommunications Technology
Association (Korea), China Academy of Telecommunication
Research (China)
WiMAXMay 2008
Certification Stagesa cti
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Wave 1: Air interface
3.5 GHz, 2.3 GHz, other
Wave 2: QoS, security, advanced radiofeatures for outdoor customer premiseequipment (CPE)
Wave 3: Indoor CPE, PC cards, nomadicservice
Wave 4: Handoffs, simple mobilityWave 5: Full mobility
ac t i v e
WiMAXMay 2008
Availability
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Certified products*
Fixed only
• 2.3 and 3.5 GHz only
10+ companies
30+ products
• Base station, subscriber
A number on “WiMAX-class”
products are on the market
*As of April 2007
WiMAXMay 2008
Antennas
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802.16 offers protocol support for advanced
antenna options under 11 GHz
Adaptive antenna systems (AAS)
• AKA “smart antennas,” “beam forming”
Multiple input/multiple output (MIMO)
Space time coding (STC)
Line of sight systems above 11 GHz do not get
much benefit from these features
WiMAXMay 2008MIMO Exploits
Spatial & Frequency Diversity
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Multiple Input Multiple OutputEssentially sends data over several parallel radios/channels
Provides spatial and frequency diversity
Used in 802.11n and elsewhere
802.16 provides protocol support for MIMOExtended in 802.16e
Options include open loop and closed loop (i.e., with feedback)
RadiosAntennas
Data
Split to
subcarriers
WiMAXMay 2008
Performance
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Can be evaluated using many different criteriaCoverage
User data throughput
User capacity
Reliability
Cost
TNSTAAFLOptimizing one aspect of performance generally
impacts performance in other areas
TNSTAAFL: There’s no such thing as a free lunch!TNSTAAFL: There’s no such thing as a free lunch!
WiMAXMay 2008
Representative Performance
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“WiMAX Deployment Considerations for Fixed Wireless Access in the 2.5 GHz and 3.5 GHz Licensed Bands”
Simulation results for 3.5GHz band, paired 3.5 MHz FDD channel Fixed user devices
Average shared downlink throughput, per channel, includingoverhead
WiMAXMay 2008
References
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IEEE (specs)
WiMAX Forum (white papers,
certification) News feeds
Texts
WiMAXMay 2008
Summary
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New entrant to crowded market
Large potentialIndustry backing
State of the art technologies
Adaptable to diverse niches
4G in developed marketsLast mile in underdeveloped markets