wimax part i: phyjain/cse574-10/ftp/j_aman.pdf · key features of wimax works on many bands: 2.3...
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10-1©2010 Raj JainCSE574sWashington University in St. Louis
WiMAX WiMAX Part I: PHYPart I: PHY
Raj JainProfessor of Computer Science and Engineering
Washington University in Saint LouisSaint Louis, MO 63130
Audio/Video recordings of this lecture are available at:http://www.cse.wustl.edu/~jain/cse574-10/
10-2©2010 Raj JainCSE574sWashington University in St. Louis
What is WiMAXPrevious Broadband Wireless Access: LMDS, MMDSWiMAX PHY LayerFrequency ReuseSubchannelizationFrame structure
OverviewOverview
10-3©2010 Raj JainCSE574sWashington University in St. Louis
What is WiMAX?What is WiMAX?
Telco Core
Point to Multipoint
Point to Point
Base Stations (BSs)
Subscriber Station (SSs)
(Rural Areas)
(Congested Areas)
<50km
<70Mbps
Downlink (DL)Uplink (UL)
<120km/sec(Mobile Users)
10-4©2010 Raj JainCSE574sWashington University in St. Louis
Data rate vs. MobilityData rate vs. Mobility
0.1 1 10 100 ++
User/Link Bit Rate Mbits/second
WiFi
WiMAX
CellularMob
ility
Vehicular
Stationary
Nomadic
10-5©2010 Raj JainCSE574sWashington University in St. Louis
Key Features of WiMAXKey Features of WiMAXWorks on many bands: 2.3 GHz, 2.5 GHz, 3.5 GHz, …Scalable ⇒ Can use any available spectrum width: 1.25 MHz to 28 MHzStrong securityOpen technology like WiFiReach and mobility like Cellular but much higher data rates
High data rate, up to 70MbpsLong distance, up to 50kmsMobility, up to 120 to 150 km/hour
Data rate vs Distance trade off using adaptive modulation. 64QAM to BPSKOffers non-line of site (NLOS) operationStrong QoS ⇒ Guaranteed services for data, voice, and video
10-6©2010 Raj JainCSE574sWashington University in St. Louis
Prior Attempts: LMDS & MMDS Prior Attempts: LMDS & MMDS Local Multipoint Distribution Service (1998)1.3 GHz around 28 GHz band (Ka Band)28 GHz ⇒ Rain effectsMulti-channel Multipoint Distribution Services (1999-2001)2.1, 2.5-2.7 GHz Band ⇒ Not affected by rain
Issues: Equipment too expensive, Roof top LoS antennas, short range (LMDS) or too small capacity (MMDS)
Modem
PoP
10-7©2010 Raj JainCSE574sWashington University in St. Louis
WiMAXWiMAX
WiMAX ≠ IEEE 802.16Worldwide Interoperability for Microwave Access420+ members including Semiconductor companies, equipment vendors, integrators, service providers. Like Wi-Fi AllianceNarrows down the list of options in IEEE 802.16 Plugfests started November 2005WiMAX forum lists certified base stations and subscriber stations from many vendorshttp://www.wimaxforum.org
10-8©2010 Raj JainCSE574sWashington University in St. Louis
Spectrum OptionsSpectrum Options
10-9©2010 Raj JainCSE574sWashington University in St. Louis
Effect of FrequencyEffect of FrequencyHigher Frequencies have higher attenuation, e.g., 18 GHz has 20 dB/m more than 1.8 GHzHigher frequencies need smaller antennaAntenna > Wavelength/2, 800 MHz ⇒ 6”Higher frequencies are affected more by weatherHigher than 10 GHz affected by rainfall60 GHz affected by absorption of oxygen moleculesHigher frequencies have more bandwidth and higher data rateHigher frequencies allow more frequency reuseThey attenuate close to cell boundaries. Low frequencies propagate far.Mobility ⇒ Below 10 GHz
10-10©2010 Raj JainCSE574sWashington University in St. Louis
IEEE 802.16 PHYsIEEE 802.16 PHYsFunction LOS Freq.
BandCarrier Duplexing
WirelessMAN SC Pt-to-pt LOS 10-66 GHz
Single TDD, FDD
WirelessMAN SCa
Pt-to-pt LOS 2-11 GHzLicensed
Single TDD, FDD
WirelessMAN OFDM (16d)
Pt-to-mpt NLOS 2-11 GHzLicensed
256 TDD, FDD
WirelessMANOFDMA (16e)
Pt-to-mpt NLOS 2-11 GHzLicensed
2048 TDD, FDD
WirelessHUMAN(High-speed Unlicensed)
Pt-to-mpt NLOS 2-11 GHzLicense Exempt
1/256/ 2048
TDDDynamic Freq. Sel.
10-11©2010 Raj JainCSE574sWashington University in St. Louis
IEEE 802.16 PHY: FeaturesIEEE 802.16 PHY: Features
Features discussed previously:Scalable OFDMATDD and FDDAdaptive Modulation and CodingSpace Time Block Codes (STBC)Adaptive Antenna System
Other Features:Subchannelization and permutationSlots, tiles, and clusters, bursts
10-12©2010 Raj JainCSE574sWashington University in St. Louis
Frequency ReuseFrequency ReuseNxSxK frequency reuse patternN=Number of cells per clusterS= Number of sectors in a cellK = Number of frequency allocations per cell
1X3X3
10-13©2010 Raj JainCSE574sWashington University in St. Louis
Frequency Reuse (Cont)Frequency Reuse (Cont)
11
1 11
1 11
1
11
1
11
1
11
1
11
1
11
1
11
1
11
1
SS
21
32
1
3 21
3
21
3
21
3
21
3
21
3
21
3
21
3
21
3
SS
1
1
1
1
1
1
1
1
1
1
SS
1
3
2
3
1
2
3
2
3
1
SS
11
13
3
3 22
2
33
3
11
1
22
2
33
3
22
2
33
3
11
1
SS
21
38
7
9 54
6
87
9
21
3
54
6
87
9
54
6
87
9
21
3
SS
1x3x1 1x3x3 1x1x1
3x1x1 3x3x1 3x3x3
10-14©2010 Raj JainCSE574sWashington University in St. Louis
Fractional Frequency ReuseFractional Frequency ReuseUsers close to the BS use all frequency subchannelsUsers at the cell boundary use only a fraction of available subchannels
F1,F2,F3
F1
F2
F3
F1,F2,F3
F1,F2,F3
10-15©2010 Raj JainCSE574sWashington University in St. Louis
OFDM SubcarriersOFDM Subcarriers
Data subcarriersPilot Subcarriers: Used for channel estimationGuard subcarriers: At the edges. No powerDC subcarrier: At the center for frequency band. No power.
DC GuardGuardPilot Data
10-16©2010 Raj JainCSE574sWashington University in St. Louis
SubchannelizationSubchannelizationSubchannel = Group of subcarriersEach user is given one or more subchannel.Subcarriers of a subchannel can be contiguous or distributed
Contiguous ⇒ Subchannels allocated based on use's SINR ⇒ Band AMC ⇒ Not suitable for mobile applications
Subchannel 1
10-17©2010 Raj JainCSE574sWashington University in St. Louis
Subcarrier PermutationsSubcarrier Permutations
Subcarriers are randomly assigned to a channel and changed every symbol time ⇒ Frequency hoppingAll subcarriers are used ⇒ Full Usage of Subcarriers (FUSC) – Not in WiMAX Forum ProfilesPartial Usage of Subcarriers (PUSC) - in WiMAX Forum profiles ⇒ commonly used
10-18©2010 Raj JainCSE574sWashington University in St. Louis
Downlink Partial Usage of SubcarriersDownlink Partial Usage of SubcarriersSubcarriers are divided in to 6 groups and only some groups may be used in a sector or cellData and pilots are arranged in clusters of 14 subcarriers over 2 symbols = 24 data + 4 pilot Clusters are renumbered using a pseudo random numbering schemeThe clusters are then divided into 6 groups (segments 0 through 5)Subchannel = Two clusters from the same groupIt is possible to allocate some subset of groups to each transmitter in a cell, e.g., 2 groups per sector
10-19©2010 Raj JainCSE574sWashington University in St. Louis
Symbols, Clusters, and Slots (PUSC DL)Symbols, Clusters, and Slots (PUSC DL)10 MHz = 1024 FFT = 840 subcarriers + 1 DC + 183 GuardTotal 30 subchannels = 30×28 = 840 subcarriers
PilotData
Cluster=2 symbols× 14 subcarriers
Slot=2 Clusters
Time
Frequency
Symbols
Subcarriers
Subchannel=28 subcarriers
10-20©2010 Raj JainCSE574sWashington University in St. Louis
PilotData
Tile=3 symbols× 4 subcarriers
Slot=6 Tiles
Time
Frequency
Symbols
Subcarriers
Subchannel=24 subcarriers
Symbols, Tiles, and Slots (PUSC UL)Symbols, Tiles, and Slots (PUSC UL)10 MHz = 1024 FFT = 840 subcarriers + 1 DC +183 GuardTotal 35 subchannels = 35X24 = 840 subcarriers
10-21©2010 Raj JainCSE574sWashington University in St. Louis
802.16 Frame Structure802.16 Frame Structure
TDD = Time Division DuplexingDL = Downlink (Base to subscriber)FCH = Frame control header:
Preamble FCH Burst 1 Burst n
Burst1
Burstm
Preamble UL Burst
DL Subframe UL Subframe DL Subframe UL SubframeTDD
…
…
FDD = Freq Div DuplexingUL = Uplink
Contention forInitial Ranging
Contention forBandwidth Req.
Burst2
Burst Profile, Down-link map, Uplink map, DL channel descriptor, etc.
10-22©2010 Raj JainCSE574sWashington University in St. Louis
Mobile WiMAX FrameMobile WiMAX FramePr
eam
ble
DL-
MA
PU
L-M
AP
FCH
UL-
MA
P (C
ont)
Ran
ging
Fast Feedback (CQICH)A
ck-C
HBurst 1
Burst 3
Burst 2
Burst 5
Burst 4Burst 1
Burst 2
Burst 3
Burst 4
Time
Freq
uenc
y
10-23©2010 Raj JainCSE574sWashington University in St. Louis
Frame StructureFrame StructureDL Preamble: Time and frequency synchronizationFrame Control Header (FCH): MAPs lengths, modulation and coding, usable subcarriersDownlink MAP: Burst profile (time, freq., modulation, coding)Uplink MAP: Burst profile for transmission from each user. MAPs can be compressedContention-based region: Ranging, bandwidth request, best-effort dataRanging Channel:
Closed loop frequency, time, and power adjustmentsChannel quality indicator channel (CQICH) CINR measurementAck Channel: subscriber stations
Initially, 5 ms frames only.
10-24©2010 Raj JainCSE574sWashington University in St. Louis
Subscriber InitializationSubscriber Initialization
Subscriber scans pre-set frequencies for base stationSubscriber finds base transmissions and synchronizes to it
Subscriber sends a ranging-request to BS at low powerSubscriber resends a ranging-request to BS at higher powersBase sends ranging response giving management conn IDs
Subscriber reports its PHY capabilities (modulation, coding, xDD)Base accepts subscriber or rejects some PHY capabilitiesBase-Subscriber Authentication using X.509 Certificates
10-25©2010 Raj JainCSE574sWashington University in St. Louis
SummarySummary
WiMAX supports non-line of sight using scalable OFDMAAny band any bandwidthSophisticated frequency reuse2D frame structure
10-26©2010 Raj JainCSE574sWashington University in St. Louis
References: BooksReferences: Books1. Cal Eklund, Roger B. Marks, Subbu Ponnuswamy, Kenneth
L. Stanwoood, Noco J.M. van Waes, "WirelessMAN: Inside the IEEE 802.16 Standard for Wireless Metropolitan Area Networks," IEEE, May-06, ISBN:0738148423.
2. Jeffrey G. Andrews, Arunabha Ghosh, Rias Muhamed, "Fundamentals of WiMAX: Understanding Broadband Wireless Networking," Prentice-Hall, ISBN:0132225522.
3. Loutfi Nuaymi, "WiMAX: Technology for Broadband Wireless Access," Wiley, Mar-07, 310 pp., ISBN:0470028087.
Note: These are the best 3 of 12+ books on WiMAX.
10-27©2010 Raj JainCSE574sWashington University in St. Louis
Reading ListReading ListJ. Thiel, “Metropolitan and Regional Wireless Networking: 802.16, 802.20 and 802.22,” http://www.cse.wustl.edu/~jain/cse574-06/wimax.htmM. Wood, “An Analysis of the Design and Implementation of QoS over IEEE 802.16,” http://www.cse.wustl.edu/~jain/cse574-06/wimax_qos.htm
10-28©2010 Raj JainCSE574sWashington University in St. Louis
Related Wikipedia PagesRelated Wikipedia Pageshttp://en.wikipedia.org/wiki/WiMAXhttp://en.wikipedia.org/wiki/IEEE_802.16http://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiple_accesshttp://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexinghttp://en.wikipedia.org/wiki/Symbol_ratehttp://en.wikipedia.org/wiki/WiBrohttp://en.wikipedia.org/wiki/WiMAX_MIMOhttp://en.wikipedia.org/wiki/Wireless_broadbandhttp://en.wikipedia.org/wiki/Wireless_local_loop
10-29©2010 Raj JainCSE574sWashington University in St. Louis
Related Wikipedia Pages (Cont)Related Wikipedia Pages (Cont)http://en.wikipedia.org/wiki/Local_Multipoint_Distribution_Servicehttp://en.wikipedia.org/wiki/Multichannel_Multipoint_Distribution_Servicehttp://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Cellular_network#Frequency_reusehttp://en.wikipedia.org/wiki/Xohmhttp://en.wikipedia.org/wiki/Clearwirehttp://en.wikipedia.org/wiki/List_of_deployed_WiMAX_networks
10-30©2010 Raj JainCSE574sWashington University in St. Louis
List of AcronymsList of AcronymsAAS Adaptive Antenna SystemAPAC Asia PacificBS Base StationBTC Block Turbo CodesCC Convolutional CodingRS-CC Reed-Solomon Convolutional CodesCINR Carrier to Interference and Noise RatioCQICH Channel quality indicator channelCTC Convolutional Turbo CodesDC Direct CurrentDIUC Downlink Interval Usage CodeDL DownlinkGHz Giga HertzIEEE Institution of Electrical and Electronics EngineersLMDS Local Multipoint Distribution Service
10-31©2010 Raj JainCSE574sWashington University in St. Louis
List of Acronyms (Cont)List of Acronyms (Cont)MAC Media Access ControlMAP Media Access Profile?MCS Modulation and Coding schemeMHz Mega HertzMIB Management Information BaseMIMO Multiple Input Multiple OutputMMR Mobile Multihop RelayOFDM Orthogonal Frequency Division MultiplexingOFDMA Orthogonal Frequency Division Multiple AccessPCMCIA Personal Computer Memory Card International AssociationPHY Physical LayerPUSC Partial Usage of SubcarriersQAM Quadrature Amplitude ModulationRSSI Received Signal Strength IndicatorSINR Signal to Interference and Noise RatioSTBC Space Time Block Codes