wimax and 3gpp lte - télécom...
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Mobile CommunicationsResearchCCSR
WiMAX and 3GPP LTEHow are they related?How are they related?
Professor Rahim Tafazolli
Centre for Communication Systems Research (CCSR), University of Surrey (UK)[email protected]
EW 20071st - 4th April
2 Mobile CommunicationsResearch
Outline of PresentationOutline of Presentation
WiMAX & LTE salient features
Air-Interface
Network Architectures
Identify some major research issues
Answer the question “ how are they related”
3 Mobile CommunicationsResearch
WiMAXWiMAX BasicsBasicsBasic WiMAX
Designed for speeds up to ~70 Mb/sOFDM, OFDMAData-centric
Realities of NLOS propagation30 miles >>> 2 miles70 Mbps >>> few Mbps
3G: High-Speed Downlink Packet Access
Frequencies
--Rysavy Rsch
Codes
HSDPA
OFDMA
WAN
WAN
MAN
Domain
1-5 milesUp to 2.4 Mbps
CDMA2000 1x EV-DO
1-5 milesUp to 10 Mbps
WCDMA/UMTS HSDPA
1 – 3 miles
Up to 30 Mbps
WiMAX(802.16e)
RangeThrput
3G
•Optimization for data vs optimization for voice•MAN + Handover + Roaming = WAN?
4 Mobile CommunicationsResearch
WiMAXWiMAX featuresfeatures
ScalabilityScalable PHY for capable of 1.25-20 MHz.Flexible frequency re-use schemes for network planning
High Data RatesLarger MAC frames with low overheadAdaptive modulationH-ARQ for reducing packet lossFull MIMO and Beamforming
QOSTraffic types Adaptive Modulation & CodingARQH-ARQ
MobilitySecure Optimized Hard HandoverFast BS Switching HandoverPower Management with Sleep and Idle modes
5 Mobile CommunicationsResearch
WiMAXWiMAX: : OFDMA TDD Frame StructureOFDMA TDD Frame Structure
Flexible subchannelizationPseudo-random permutation for diversityContiguous permutation for selectivity
Operation in varying channel widths
1.25 MHz, 2.5, 5, 10, 15 and 20 MHz channels
Diversity permutationDownlink FUSCDownlink PUSCUplink PUSC
Contiguous permutationDownlink Band AMCUplink Band AMC
6 Mobile CommunicationsResearch
WiMAXWiMAX--Power ControlPower Control
Open loop power controlUL interfenrece+noise level broadcasted in DL MapPath loss estimate based on channel reciprocityPower offset based on ACK/NACKFast power control (by UL-MAP )
Close loop power controlPower adjustment sent in DL power controlPower adjust in 0.25dB step
Power adjustment by periodical ranging
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WiMAXWiMAX FeaturesFeatures
Tradeoff between link robustness and capacityAdaptation on a burst by burst basis
Modulation formats:BPSKQPSK16QAM64 QAM
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Advanced Antenna SystemAdvanced Antenna System
AAS (beamforming)Space time code (STC)Spatial multiplexing (SM)Adaptive MIMO switch (AMS)Space Time Block Codes and Spatial multiplexingCollaborative Spatial Multiplexing (CSM)Dynamic band allocation for AMC sub-carrier mapping
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WiMAXWiMAX
Modulation: BPSK, QPSK, 16 QAM, and 64 QAM.
Bit Detection:Soft-input soft-bit de-mapper based on MAP criterionMRC combining for multiple Rx antenna (if STBC is switched off)
FEC coding: convolutional tail biting code (CCTB), convolutionalzero padded (CCZP), convolutional turbo code (CTC), and Low Density Parity Check (LDPC)CCTB,CCZP, and CTC Rates: 1/2, 2/3, 3/4, 5/6 (through puncturing)LDPC rates: 1/2, 2/3, and 3/4
Repetition Coding
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Throughput, Cell Range, QualityThroughput, Cell Range, Quality
0 500 1000 1500 2000 25000
2
4
6
8
10
12
14x 10
5 User average throughput v.s. distance
Distance (m)
Thro
ughp
ut (b
ps)
WiMaxHSDPA
7 0 8 0 90 1 00 110 120 130 1400
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1C DF o f pa ck e t d ela y
P ac k e t de lay (n u m b e r of fra m e s )
Cum
ulat
ive
dist
ribut
ion W iM ax
HSD P A
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Capability Evolution
Typ
ical
ran
ge (
km) 30
0.1
1
10
GSMGPRS
EGPRSUMTS
HSPA
0.01 0.1 1 10
802.11a
802.16
802.11b
“Super3G”“LTE”
Drive performance and efficiencybeyond today’s limits (performance/cost ratio)
Typical user rate (Mbps)
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3G LTE3G LTE-- MotivationMotivation
Continuous growth of Mobile Communications-towards Broadband personal communications
Higher capacityReduced delayHigher data ratesAutomatic planning capabilitySimplified network managementAlways onMulti/Broadcast capability
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LTE SpecificationsLTE Specifications
Data Rates:30Mbps(UL), 100Mbps (DL)Speed: walking to bullet train
High performance/cost ratioSpectral efficiency target 5bps/Hz
Reduced latencyTTI latency <0.5msInteractive gaming, VoIP
Optimised for packet switchingPS onlyIP routing (CN & RAN)Better support of VoIP, Data
Cost efficient deploymentRe-use of 3G/2G spectrumBandwidth flexibility (1.25, 2.5, 5, 10, 15, 20MHz)Minimum network operation cost
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PHY layer Key TechnologiesPHY layer Key Technologies
Downlink-OFDMUplink-Single Carrier FDMAMultiple antenna techniques for high capacityInter-cell interference mitigationMulticast and Broadcast servicesChannel Frequency & Time domains exploitation for rate and/or power adaptation
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DownlinkDownlink
• OFDMA (1.25, 2.5, 5, 10, 15, 20MHz)
• Sub-frame duration: 0.5ms
• Sub-carrier spacing: 15KHz
• FFT size –Occupied Sub-carriers: 128-76(1.25MHz), 256-151, 512-301, 1024-601, 1536-901, 2048-1201
• NUM. OFDM Symbols per sub-frame:7 (with short CP)6 (with long CP)
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UPLINKUPLINK
Power-efficient CoverageLow peak-average power ratioLow power consumption by UESupporting wide area coverage
Support scalable bandwidth and flexible scheduling
FDMA
Similar frame structure as downlinkFlexible Cyclic prefix (CP) structure
Orthogonality among uplink users, Cyclic prefix to account for relative timing difference
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Advanced Antenna SystemAdvanced Antenna System
Single data stream per userBeamforming
Coverage, longer battery life
Spatial Division Multiple Access (SDMA)Multiple users in same radio resource
Multiple data stream per userDiversity
Link robustness
Spatial muliplexingSpectral efficiency, high data rate support
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Diversity and MultiplexingDiversity and Multiplexing
Basic 2 Tx, 2RxSpatial multiplexing
Different modulation/coding per streamMultiuser MIMOClosed loop with feedback
Spatial diversityOpen loop transmit diversity
» Cyclic delay diversity» Space time coding
Closed loop transmit diversity» Beamforming» Antenna selection
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Interference MitigationInterference Mitigation
ObjectiveOne cell freq. re-use for simplified planning
ProblemsCell edge users suffer interference from neighbouring cells
Possible solutionsInter-cell interference randomisationInter-cell interference cancellationInter-cell interference co-ordination
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InterInter--cell Interference Mitigationcell Interference Mitigation
Inter-cell Interference RandomizationCell-specific interleaved division multiple access (IDMA)
» Interleaving pattern depends on cell-IDFrequency hopping
Inter-cell Interference cancellationSpatial suppression by beamformingInterference cancellation with IDMA
Inter-cell Interference CoordinationFlexible Soft Freq. re-use (SFR)
» Primary and secondary freq. bands» Primary band: reuse > 1, higher TX power» Secondary bands: Remainng spectrum» Cell-edge users: Use primary band good SIR» Cell-centre users: use entire band high data rates
Supported by means of frequency domain scheduling
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LTE System ArchitecturesLTE System Architectures4X44X4
4 protocol optionsGTP-U tunneling based mechanismGTP-U Tunneling + MIP based mechanismGTP-U Tunneling + PMIP based mechanismPure MIP based mechanism
4 Packet Core Architecture OptionsOption 1 (Full Split)Option 2 (Traditional SGSN/GGSN like)Option 3 (Combined User Plane Node)Option 4 (All in One)
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SAE Evolved Packet Core SAE Evolved Packet Core Architecture OptionsArchitecture Options
S6
UPE S5b
S5cMME S5aS1a
S1b
S2
S3
Inter ASAnchor
S4
S2
S7
Gi
Option 1 (“Full Split”):S3a
MME/UPE
S5
S1
S2
S3
Inter ASAnchor
S4
S2
S7
S6
Gi
Option 2 (“Traditional SGSN/GGSN-like”):
MMES5d
Inter ASAnchor/
UPE
S1c
S1d
S2 S2
S6S3 S4
Gi
S7
Option 3 (“Combined User Plane Node”):
MME/ UPE / Inter AS AnchorS1
S2 S2
S6
S7S3
Gi
S4
Option 4 (“All in One”):
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InterInter-- SAE LTE mobilitySAE LTE mobility
Source MME/UPE
Target MME/UPE
Source Evolved RAN
HSS
UE handoff
Source LTE/SAE Network
Target LTE/SAE Network
Inter Access System Anchor
Target Evolved RAN
IP Network
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Research IssuesResearch Issues
• Minimum capacity per user similar to xDSL (8Mbps)• Capacity at cell edge
Interference mitigation schemesIntelligent schedulers
• Self-optimisation and planningA multidimensional and multivariable problemPositioning technique
• Multihop communications• Wireless Mesh Backhaul• Evaluation of Network architecture options
Mobility management (fast vertical handover)QoS, SecurityIP to e-Node BScalabilityCross-cells resource management and self-organised network operation
• Always on and end-to-end delay optimisation
25 Mobile CommunicationsResearch
How are they related?How are they related?
Not relatedLTE is an e-2-e system whereas WiMAX is an Radio Access technology WiMAX should be considered as 2nd Generation of Wireless LAN
Wifi with mobilityGood solution for Fixed operators enter mobile business
3GPP LTE is a step towards 4G Cellular system, ITU-R IMT-AdvanceLooking at AI options, LTE is much simpler whereas WiMAXhas many options but not necessary leading in significant performance difference
LTE addresses main concerns of cellular operators with backward compatibility, enhancing performance/cost ratio through self-organisation and network management