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© John Moring 2007-2008
Fundamentals ofWiMAX
Broadband Wireless AccessTechnology
May 2008
John Moringwww.moring.net
760-633-1790
John Moringwww.moring.net
760-633-1790
©2007-2008 John Moring page 2
WiMAXMay 2008Objectives
Familiarity with available standards and their scopeUnderstanding of WiMAX related to competing technologiesView of work in progressOverview of features and capabilities
©2007-2008 John Moring page 3
WiMAXMay 2008Outline
WiMAX Intro - 1 hourOverviewWhat is WiMAX? Industry activities
WiMAX Technology - 1 hourTechnology overview 802.16 elements Technology features Equipment characteristics
©2007-2008 John Moring page 4
WiMAXMay 2008Overview
What is WiMAX?Broadband wireless accessCompetition
Industry activities IEEEWiMAX ForumIndustry
Technology overviewSpectrumOSI/IEEE model
IEEE: Institute of Electrical and Electronics EngineersOSI: Open System Interconnect
IEEE: Institute of Electrical and Electronics EngineersOSI: Open System Interconnect
©2007-2008 John Moring page 5
WiMAXMay 2008Overview
802.16 elementsMAC sublayers• Service-specific convergence• MAC common part• Security
PHY options• Single carrier, OFDM, OFDMA• Line of sight (10+ GHz), • Non-line of sight (<11 GHz)• Licensed, unlicensed
MAC: medium access controlOFDM: orthogonal frequency division multiplexingOFDMA: orthogonal frequency division multiple accessPHY: physical layer
MAC: medium access controlOFDM: orthogonal frequency division multiplexingOFDMA: orthogonal frequency division multiple accessPHY: physical layer
©2007-2008 John Moring page 6
WiMAXMay 2008Overview
Technology featuresTopology, symmetry, duplex, TDD, FDDQuality of service (QoS)Security• Encryption• AuthenticationReliability• Forward error correction (FEC)• Automatic repeat request (ARQ)• Adaptive modulation and coding
TDD: time division duplexFDD: frequency division duplex
TDD: time division duplexFDD: frequency division duplex
©2007-2008 John Moring page 7
WiMAXMay 2008Overview
PerformancePropagation & coverageThroughputCapacity, frequency planning
Advanced featuresMesh MobilityMIMOAdvanced antenna systems
MIMO: multiple input, multiple outputMIMO: multiple input, multiple output
©2007-2008 John Moring page 8
WiMAXMay 2008What 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
©2007-2008 John Moring page 9
WiMAXMay 2008WiMAX Targets Multiple Markets
Last mile connectivityDSL/cable alternative
BackhaulT-1/microwave alternative
Mobility/portability3G cellular/Wi-Fi alternative
©2007-2008 John Moring page 10
WiMAXMay 2008WiMAX Employs Familiar Components
Base Station (BS)
Downlink (DL)
Backhaul
Fixed Subscriber
Station (SS)
Mobile Subscriber
Station (MS)
Uplink (UL)Infrastructure
©2007-2008 John Moring page 11
WiMAXMay 2008802.16 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 2Can support any higher layer protocols and services
Medium Access Control
©2007-2008 John Moring page 12
WiMAXMay 2008Competition
A number of broadband access technologies existDSLCableT1/T3FiberMicrowaveSatelliteCellularWi-FiProprietary technologies
What distinguishes WiMAX?
©2007-2008 John Moring page 13
WiMAXMay 2008
Bluetooth
802.11
Short rangeZigBee
Wireless Data Landscape
103bps
106bps
109bps
1 m 1 km 1000 kmCOVERAGE ZONE
TH
RO
UG
HPU
T
bps: bits per secondG: generationLEO: low earth orbitVSAT: very small aperture [satellite] terminal
bps: bits per secondG: generationLEO: low earth orbitVSAT: very small aperture [satellite] terminal
Fixed wireless
VSATWiMAX
Microwave
Paging
Wide area
LEO satellite
3G CellularWiMAX
2G Cellular
©2007-2008 John Moring page 14
WiMAXMay 2008Metrics
CapacityThroughputCoverageMobilityQuality of ServiceSecurityReliabilityCostsAvailability/maturity
©2007-2008 John Moring page 15
WiMAXMay 2008What Distinguishes WiMAX?
Wide area, wireless, broadband, point to multipoint
Mobility optionMesh option
Multiple frequency bands, including unlicensedFlexible & efficient use of spectrum
• Advanced, adaptive modulation• Adaptive antenna technologies
Multi-vendor interoperabilityEconomies of scale (expected)Inherent quality of service (QoS)Carrier-grade security
©2007-2008 John Moring page 16
WiMAXMay 2008WiMAX vs Wi-Fi
Longer rangeMore spectrum optionsQuality of serviceMobilityRicher security features
©2007-2008 John Moring page 17
WiMAXMay 2008WiMAX vs Cellular
Better channel efficiencyMore flexible quality of servicePotentially better economies of scale
In the cellular arena, WiMAX faces LTE (Long Term Evolution) being standardized by 3GPP
Chosen by AT&T, Verizon, Ericsson, etc.
3GPP: third generation partnership project3GPP: third generation partnership project
©2007-2008 John Moring page 18
WiMAXMay 2008WiMAX vs Proprietary
Standards-based ConfidenceMulti-vendor interoperabilityEconomies of scale
©2007-2008 John Moring page 19
WiMAXMay 2008Tradeoffs
©2007-2008 John Moring page 20
WiMAXMay 2008Representative 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 channelFixed user devicesAverage shared downlink throughput, per channel, including overhead
©2007-2008 John Moring page 21
WiMAXMay 2008The Many Faces of WiMAX
Fixed / mobileLine of sight / non-line of sight
Different bands and channel bandwidthsLicensed / unlicensed spectrumFrequency division / time division / half-duplex frequency division channel usageSingle carrier / OFDM / OFDMAPlus many configurable options
SecurityReliabilityAdvanced antennasEtc.
“Profiles” collect reasonable feature sets for certification and interoperability
OFDM: orthogonal frequency division multiplexingOFDMA: orthogonal frequency division multiple access
OFDM: orthogonal frequency division multiplexingOFDMA: orthogonal frequency division multiple access
©2007-2008 John Moring page 22
WiMAXMay 2008WiMAX Features Related to Spectrum
NLOSOFDM, OFDMA, SCLicensed, unlicensed
Fixed
LOSSingle carrier
Mostly licensedFixed
6GH
z
66G
Hz
LOS: line of sightNLOS: non-line of sightOFDM: orthogonal frequency division multiplexOFDMA: orthogonal frequency division multiple accessSC: single carrier
LOS: line of sightNLOS: non-line of sightOFDM: orthogonal frequency division multiplexOFDMA: orthogonal frequency division multiple accessSC: single carrier
2GH
z
MobileOFDMA
11G
Hz
10G
Hz
Added 2004
Added 2005
©2007-2008 John Moring page 23
WiMAXMay 2008Outline
WiMAX IntroOverview What is WiMAX? Industry activities
WiMAX TechnologyTechnology overview 802.16 elements Technology features Equipment characteristics
©2007-2008 John Moring page 24
WiMAXMay 2008Industry Activities
Institute of Electrical and Electronics Engineers (IEEE)Standards802.3 Ethernet, 802.11 Wi-Fi, etc.802.16 WiMAX
WiMAX ForumIndustry consortium400+ membersPromotes the technology, defines “profiles,” certifies equipment
International bodiesMajor commitments from industry leaders, e.g.,
IntelSprintClearwireMotorolaEtc.
©2007-2008 John Moring page 25
WiMAXMay 2008Three Standards Specify Air Interface
IEEE Std 802.16-2004Encompasses and supercedes
• 802.16-2001, original standard• 802.16a, adds <11 GHz• 802.16c, adds profiles
Sometimes called “802.16d”IEEE Std 802.16-2004/Cor1
Corrigendum, adds correctionsIEEE Std 802.16e-2005
Amendment, adds mobility, etc.
Other amendments cover specific areas
©2007-2008 John Moring page 26
WiMAXMay 2008WiMAX Forum Promotes and Certifies
“The WiMAX Forum® is an industry-led, not-for-profit organization formed to certify and promote the compatibility and interoperability of broadband wireless products based upon the harmonized IEEE 802.16/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 and mobile services. “Along these lines, the WiMAX Forum works closely with service providers and regulators to ensure that WiMAX Forum Certified systems meet customer and government requirements”
www.wimaxforum.org
©2007-2008 John Moring page 27
WiMAXMay 2008WiBro 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 channelsOFDMA, TDDMobility ≤60 km/hrCoverage ≤1 kmPer-user throughput: 128 kbps – 3 Mbps
Nationwide service 4/2007Multiple carriers100,000+ subscribers by 12/2007Price per month ~$20
©2007-2008 John Moring page 28
WiMAXMay 2008802.16 Also Active in Europe
ETSI HiPerMANSubset of IEEE 802.16Fixed, 2 GHz – 11 GHzSeparate test regime from WiMAX
International Telecommunications UnionSubsets of 802.16 proposed/approved for inclusion in the IMT-2000 family of 3G/4G wireless standardsApproval allows deployment in Europe in bands reserved for IMT (traditionally cellular) technologies
3.5 GHz deployments in progressETSI – European Telecommunications Standards InstituteHiPerMAN – high performance metro area networkIMT – International Mobile Telecommunications
ETSI – European Telecommunications Standards InstituteHiPerMAN – high performance metro area networkIMT – International Mobile Telecommunications
©2007-2008 John Moring page 29
WiMAXMay 2008Provider Example: Clearwire
Source: Clearwire website 9/07
©2007-2008 John Moring page 30
WiMAXMay 2008Example: Clearwire
Clearwire Corporation is unwiring Nashville with the introduction of its next-generation wireless broadband solution. The company announced today the official launch of its wireless high-speed Internet access and phone service to the city….Nashville residents and businesses can now have a fast, simple, portable, reliable and affordable alternative to traditional dial-up, cable and DSL. Clearwire service eliminates the confines of traditional cable or telephone wiring, allowing customers to connect at home, a localcoffeehouse, the office or virtually anywhere else in the Clearwire service area. …Simply purchase a modem at … Circuit City, Best Buy or online at www.clearwire.com, and within minutes, Internet access or phone service will be up and running. Clearwire’s next-generation, non-line-of-sight wireless broadband network solution connects customers through licensed or secured spectrum.… Clearwire Internet Phone Service works with a customer’s existing high-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
©2007-2008 John Moring page 31
WiMAXMay 2008Example: Clearwire
Source: Clearwire website 9/07
©2007-2008 John Moring page 32
WiMAXMay 2008Vendor 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 its technical and economic advantages, should help enable mainstreamadoption of personal broadband.“Intel® WiMAX Connection 2250 is a low-cost system-on-chipthat supports IEEE 802.16-2004 and IEEE 802.16e-2005, enabling WiMAX 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
©2007-2008 John Moring page 33
WiMAXMay 2008Provider Quotes: Sprint Nextel
8/8/06. Sprint Nextel Corp. …announced its plans to develop and deploy the first fourth generation (4G) nationwide broadband mobile network. The 4G wireless broadband network will use the mobile WiMAX IEEE 802.16e-2005 technology standard. Working together with Intel, Motorola and Samsung, Sprint Nextel will develop a nationwide network … designed to offer faster speeds, lower cost, and greater convenience and enhanced multimedia quality. The Sprint Nextel 4G mobility network will use the company's extensive 2.5GHz spectrum 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 a network that reaches as many as 100 million people in 2008. Sprint Nextel plans to expand mobile WiMAX network coverage thereafter. The company will continue to invest in and offer access to its current wireless and Sprint PowerVision mobile broadband networks to serve customer communications needs today and into the future. Sprint Nextel is expecting to invest $1 billion in 2007 and between $1.5 billion and $2 billion in 2008Motorola and Samsung will also support Sprint's current and CDMA/EV-DO network technologies by creating multimode devices that will support services on both the 4G network and the 3G network … will provide voice service using the core 3G network.
News services
©2007-2008 John Moring page 34
WiMAXMay 2008Sprint XOHMTM
Aug. 16 2007 -- Sprint announced today that its WiMAX service will be marketed under the XOHMTM ingredient brand (pronounced ZOAM). A soft launch of the WiMAX network is expected by the end of 2007 in the Chicago and Baltimore/Washington markets. XOHM commercial services are expected 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 mobile broadband 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 company currently expects that extending its coverage to approximately 125 million people by year-end 2010 would require an additional capital expenditure of approximately $2.5 billion.….
News services
©2007-2008 John Moring page 35
WiMAXMay 2008Sprint 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 for high-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."
©2007-2008 John Moring page 36
WiMAXMay 2008Cisco Buys WiMAX Infrastructure Player
SAN JOSE, Calif. -- Cisco(R) announced a definitive agreement to purchase Richardson, TX-based Navini Networks, Inc. a leader in the Mobile WiMAX 802.16e-2005 broadband wireless industry. Navini is a pioneer in the integration of "Smart Beamforming" technologies with Multi-Input Multi-Output (MIMO) antennas, a combination that improves the performance and range for WiMAX services and lowers the overall deployment and operational costs for service providers….Cisco also expects that its broadband wireless solution portfolio, that now includes WiMAX products, will play a key role in Cisco´s Country Transformation 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 costs and 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 upon WiMAX have the potential to add millions of new Internet users who cannot 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 new applications and services."
Byteandswitch.com 11/07
©2007-2008 John Moring page 37
WiMAXMay 2008Summary
New entrant to crowded market
Large potentialIndustry backingState of the art technologies
Adaptable to diverse niches4G in developed marketsLast mile in underdeveloped markets
©2007-2008 John Moring page 38
WiMAXMay 2008Outline
WiMAX Intro - 1 hourWhat is WiMAX? Industry activities
WiMAX Technology - 1 hourTechnology overview 802.16 elements Technology features Equipment characteristics
©2007-2008 John Moring page 39
WiMAXMay 2008The Many Faces of WiMAX
Line of sight / non-line of sightDifferent bands and channel bandwidths
Licensed / unlicensed spectrumFrequency division / time division / half-duplex frequency division channel usageFixed / mobileSingle carrier / OFDM / OFDMAPlus many configurable options
SecurityReliabilityAdvanced antennasEtc.
OFDM: orthogonal frequency division multiplexingOFDMA: orthogonal frequency division multiple access
OFDM: orthogonal frequency division multiplexingOFDMA: orthogonal frequency division multiple access
©2007-2008 John Moring page 40
WiMAXMay 2008Spectrum Allocation
3.5 GHzWidely allocated and available for WiMAX in Europe & elsewhere
2.5 GHz In US, mostly licensed by Sprint/ClearwireTo be allocated in Europe in 2008Allocations exist elsewhere
5.8 GHz Licensed-free in the US, parts of Europe
Other bands to watch2.3 GHz used for WiBro in Korea700 MHz, 900 MHz, 3.6 GHz, 5.4 GHz
©2007-2008 John Moring page 41
WiMAXMay 2008WiMAX Features Related to Spectrum
NLOSOFDM, OFDMA, SCLicensed, unlicensed
Fixed
LOSSingle carrier
Mostly licensedFixed
6GH
z
66G
Hz
LOS: line of sightNLOS: non-line of sightOFDM: orthogonal frequency division multiplexOFDMA: orthogonal frequency division multiple accessSC: single carrier
LOS: line of sightNLOS: non-line of sightOFDM: orthogonal frequency division multiplexOFDMA: orthogonal frequency division multiple accessSC: single carrier
2GH
z
MobileOFDMA
11G
Hz
10G
Hz
Added 2004
Added 2005
©2007-2008 John Moring page 42
WiMAXMay 2008Mobile Network Model
From WiMAX Forum Network Architecture
Rn designates reference interfaceR1 specified in 802.16
AAA: authentication, authorization, accountingASN: access service networkASP: application service providerCSN: connectivity service networkGW: gatewayHA: home agentNAP: network access providerNSP: network service providerPF: policy function
AAA: authentication, authorization, accountingASN: access service networkASP: application service providerCSN: connectivity service networkGW: gatewayHA: home agentNAP: network access providerNSP: network service providerPF: policy function
ASPR6
R4
©2007-2008 John Moring page 43
WiMAXMay 2008Outline
WiMAX IntroOverviewWhat is WiMAX? Industry activities
WiMAX TechnologyTechnology overview 802.16 elements
• Protocol model– Service-Specific Convergence Sublayer– MAC Common Part Sublayer– Security Sublayer– Physical layer
• Modulation Technology features Equipment characteristics
©2007-2008 John Moring page 44
WiMAXMay 2008Protocol Models
802.16 Model
Physical
Presentation
Application
Session
Transport
Network
Data Link
Logical Link Control 802.2
Physical
Medium Access Control
Service-Specific Convergence Sublayer
Security Sublayer
MAC Common Part Sublayer
Physical
OSI Model IEEE ModelNote: mappings are approximate
©2007-2008 John Moring page 45
WiMAXMay 2008Service-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 bandwidth allocation; optional header suppressionThere may be multiple CS per MAC/PHY
PHYMAC
CS CS
IP ATM
ATM: asynchronous transfer modeIP: Internet protocolMAC: medium access controlPHY: physical layerQoS: quality of serviceVLAN: virtual local area network
ATM: asynchronous transfer modeIP: Internet protocolMAC: medium access controlPHY: physical layerQoS: quality of serviceVLAN: virtual local area network
©2007-2008 John Moring page 46
WiMAXMay 2008MAC Common Part Sublayer
Core MAC functionsQuality of service (QoS) managementReliability• Dynamic forward error correction (FEC) and
modulation management• Automatic repeat request (ARQ)
Packet fragmentation/defragmentationScheduling
MAC: medium access controlMAC: medium access control
©2007-2008 John Moring page 47
WiMAXMay 2008WiMAX is Connection Oriented
Allows robust QoSConnection-oriented
A connection, session, or association is formed between the communicating end devicesAll circuit technologiesSome packet technologies
• "Virtual circuits"• E.g., TCP, Frame Relay, ATM, WiMAX
vs ConnectionlessNo association, each packet treated individuallyEthernet, IP, UDP
ATM: Asynchronous Transfer ModeIP: Internet ProtocolTCP: Transmission Control ProtocolUDP: User Datagram Protocol
ATM: Asynchronous Transfer ModeIP: Internet ProtocolTCP: Transmission Control ProtocolUDP: User Datagram Protocol
©2007-2008 John Moring page 48
WiMAXMay 2008Security Sublayer
EncryptionProvides user data privacyUses encryption algorithms and crypto keys
Authentication/authorizationVerifies identity of SSVerifies identity of BS (added in 802.16e)Uses certificates, digital signatures, trusted third-party verification
BS: base stationSS: subscriber station
BS: base stationSS: subscriber station
©2007-2008 John Moring page 49
WiMAXMay 2008Security Features
EncryptionProvides user data privacy
• NOT MAC header or most management messagesUses encryption algorithms and crypto keys
• Traffic encryption key (TEK)
Authentication/authorizationVerifies identity of SSVerifies identity of BS (added in 802.16e)Uses certificates, digital signatures, trusted third-party verification
Key exchangeManagement plane
Control message validationBS: base stationSS: subscriber station
BS: base stationSS: subscriber station
©2007-2008 John Moring page 50
WiMAXMay 2008Security Concepts
Crypto suitesTriple 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
©2007-2008 John Moring page 51
WiMAXMay 2008Modulations used in 802.16
Modulation and coding adjusted to adapt to signal pathBPSK
1 bit/symbol
QPSK2 bits/symbol
16-QAM4 bits/symbol
64-QAM8 bits/symbol
256-QAM16 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 represent 2 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)
phaseam
plitude
BPSK: binary phase shift keyingQAM: quadrature amplitude modulationQPSK: quadrature phase shift keying
BPSK: binary phase shift keyingQAM: quadrature amplitude modulationQPSK: quadrature phase shift keying
©2007-2008 John Moring page 52
WiMAXMay 2008Outline
WiMAX IntroWhat is WiMAX? Industry activities
WiMAX TechnologyTechnology overview 802.16 elements Technology features
• Topology• Time/frequency division• Quality of service (QoS)• Reliability• Mobility
Equipment characteristics
©2007-2008 John Moring page 53
WiMAXMay 2008Topologies Illustrated
Point to point
Point to multipoint
Mesh
Dynamic mobile mesh
Mesh BS
Nodes
Infrastructurerelay
Mesh BS Nodes
Mesh BS
active
©2007-2008 John Moring page 54
WiMAXMay 2008TDD and FDD
WiMAX includes support for both Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD)FDD
Requires paired channels• Usually licensed• Each unit requires dual transceivers
Good for symmetric trafficMay be full duplex or half duplex at subscriber
TDDSingle shared channel
• Some channel inefficiencies when radio switches between transmit and receive
Half duplexMay use fixed or adaptive slot sizes
• Good for asymmetric traffic
©2007-2008 John Moring page 55
WiMAXMay 2008Single Carrier
One radio channel carries each transmitter’s signal
Pow
er
Frequencyf
Bandwidth (BW)
©2007-2008 John Moring page 56
WiMAXMay 2008OFDM Employs Subcarriers
DataPilot - referenceGuard – interference avoidance
Pow
er
FrequencySubcarriers typically ~10 kHz wideNumber of subcarriers related to Fast Fourier Transform (FFT) size
Bandwidth (BW)
OFDM: orthogonal frequency division multiplexing
OFDM: orthogonal frequency division multiplexing
©2007-2008 John Moring page 57
WiMAXMay 2008Orthogonal Frequency Division
Multiplexing (OFDM)Essentially sends data over several parallel channelsProvides frequency diversityReduces inter-symbol interferenceUsed in 802.11a/g (Wi-Fi) and elsewhereUsers share the channel via time slots
DataSplit to
subcarriers
AntennaRadio
©2007-2008 John Moring page 58
WiMAXMay 2008
Use
r3
Time
OFDM with TDMA
Each transmitter’s signal is carried in a series of related subcarriersOne transmitter on the channel at a time
Pow
er
Frequencyf0 fn
Use
r2U
ser1
OFDM: orthogonal frequency division multiplexingTDMA: time division multiple access
OFDM: orthogonal frequency division multiplexingTDMA: time division multiple access
©2007-2008 John Moring page 59
WiMAXMay 2008Orthogonal Frequency Division Multiple
Access (OFDMA)Subsets of subcarriers are allocated to different users
Uplink and downlinkMultiple users may share the channel simultaneouslyA superior frequency can be chosen for a given user
User 2Data
Split to subcarriers
AntennaRadio
User 1Data
Downlink side illustrated
©2007-2008 John Moring page 60
WiMAXMay 2008OFDMA
Each transmitter’s signal is assigned to a subchannel, i.e., subset of the available subcarriers
Pow
er
Frequency
User4
TimeU
ser2
User5
User1
User4User1
User3
User5
User3
©2007-2008 John Moring page 61
WiMAXMay 2008Quality of Service (QoS)
QoS is required to support the requirements of different traffic typesAccess to the channel is controlled by the BS
Unlike Wi-Fi or Ethernet, which use contention access schemes under control of the stations
BS can efficiently allocate uplink and downlink resources based on requests from SS
BS: base stationSS: subscriber station
BS: base stationSS: subscriber station
©2007-2008 John Moring page 62
WiMAXMay 2008Fundamental QoS Metrics
ThroughputConnection capacity, in bits per second
LatencyConnection delay, in milliseconds (ms)
JitterVariability of delay, in milliseconds
How much…
How quick…
How consistent…
©2007-2008 John Moring page 63
WiMAXMay 2008Robust Reliability Options
Forward error correction (FEC)Code rates adapt to link qualityReed-Solomon (RS)Optional Block Turbo Codes and Convolutional Turbo Codes
Automatic Repeat Request (ARQ)MAC Block basedAcknowledgements (ACKs) can be selective or cumulative; standalone or piggybackedOptional Hybrid ARQ (HARQ)
• Incorporates FEC as well ACKs and resends
©2007-2008 John Moring page 64
WiMAXMay 2008Mobility
802.16e introduces the Mobile Station (MS) class of SSMoving MS may cross BS coverage boundariesHandover: MS migrates from one BS to another
Break-before-makeMake-before-break
• Fast BS switching• Macro diversity handover
ASN-anchored vs. CSN anchored
ASN: access service networkBS: base stationCSN: connectivity service networkSS: subscriber station
ASN: access service networkBS: base stationCSN: connectivity service networkSS: subscriber station
©2007-2008 John Moring page 65
WiMAXMay 2008Outline
WiMAX IntroWhat is WiMAX? Industry activities
WiMAX TechnologyTechnology overview 802.16 elements Technology features Equipment characteristics
©2007-2008 John Moring page 66
WiMAXMay 2008Equipment Characteristics
Subscriber stationBase stationCertificationAntennas
Alvarion BreezeMAX
©2007-2008 John Moring page 67
WiMAXMay 2008Subscriber Station
FixedIndoor
• Consumer installation• Inexpensive, low performance
Outdoor• Technician mounted• Expensive, high gain, better path
MobileDedicated WiMAX devices (e.g., tablet, phone)Add on (PC card)Embedded in multipurpose devices (e.g., PC, phone)
©2007-2008 John Moring page 68
WiMAXMay 2008Base Station
Comparable to cellular base stationsIndoor equipmentOutdoor equipment
Antenna spec, mountingTechnical features
Band, bandwidth, FDD/TDD, ….Support for optional featuresManagement interface
CapacitySectors, channels, connections, ….
Performance specsPower, sensitivity, ….
Interfaces
©2007-2008 John Moring page 69
WiMAXMay 2008WiMAX Forum Certification
Includes conformance and interoperability testsCertified equipment must conform to
Specific IEEE 802.16 standardA particular defined profileWiMAX 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)
©2007-2008 John Moring page 70
WiMAXMay 2008Certification Stages
Wave 1: Air interface3.5 GHz, 2.3 GHz, other
Wave 2: QoS, security, advanced radio features for outdoor customer premise equipment (CPE) Wave 3: Indoor CPE, PC cards, nomadic serviceWave 4: Handoffs, simple mobilityWave 5: Full mobility
active
©2007-2008 John Moring page 71
WiMAXMay 2008Availability
Certified products*Fixed only
• 2.3 and 3.5 GHz only
10+ companies30+ products
• Base station, subscriber
A number on “WiMAX-class”products are on the market
*As of April 2007
©2007-2008 John Moring page 72
WiMAXMay 2008Antennas
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
©2007-2008 John Moring page 73
WiMAXMay 2008MIMO Exploits
Spatial & Frequency DiversityMultiple Input Multiple Output
Essentially sends data over several parallel radios/channelsProvides spatial and frequency diversityUsed in 802.11n and elsewhere
802.16 provides protocol support for MIMOExtended in 802.16eOptions include open loop and closed loop (i.e., with feedback)
Radios AntennasData
Split to subcarriers
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WiMAXMay 2008Performance
Can be evaluated using many different criteriaCoverageUser data throughputUser capacityReliabilityCost
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!
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WiMAXMay 2008Representative 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 channelFixed user devicesAverage shared downlink throughput, per channel, including overhead
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WiMAXMay 2008References
IEEE (specs)WiMAX Forum (white papers, certification)News feeds Texts
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WiMAXMay 2008Summary
New entrant to crowded market
Large potentialIndustry backingState of the art technologies
Adaptable to diverse niches4G in developed marketsLast mile in underdeveloped markets
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