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Aida Botonjić Tieto 1 LTE Aida Botonjić
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LTE Aida Botonjić
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Why LTE?
• Applications:• Interactive gaming• DVD quality video• Data download/upload
• Targets:• High data rates at high speed• Low latency • Packet optimized radio access technology
• Goals:• Improving efficiency• Lowering costs• Reducing complexity• Improving services • Making use of new spectrum opportunities and better integration with other open
standards (such as WLAN and WiMAX)
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November 2004, 3GPP Rel8: Long-term Evolution (LTE)
Related specifications are formally known as the evolved UMTS terrestrial radio access (E-UTRA) and evolved UMTS terrestrial radio access network (E-UTRAN)
LTE encompasses the evolution of:- the radio access through the E-UTRAN- the non-radio aspects under the term System
Architecture Evolution (SAE)
Entire system composed of both LTE and SAE is called the Evolved Packet System (EPS)
Introduction
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IP Transport Network
Network Architecture
Cost efficient two node architecture
Fully meshed approach with tunneling mechanism over IP network
Access gateway (AGW) Enhanced Node B (eNB)
IP Service Network
S1
X2X2
X2X2
S1S1 S1
AGWAGW
eNB
eNB
eNB
eNB
eNB
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Network Elements
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Protocol overview
NASNAS
RRCRRC
PDCPPDCP
RLCRLC
MACMAC
PHYPHY
UE
RRCRRC
PDCPPDCP
RLCRLC
MACMAC
PHYPHY
eNB
NASNAS
MME
HandoversHandovers
Ciphering Ciphering
SegmentationSegmentation
HARQHARQ
Modulation, coding
Modulation, coding
NASNAS
RRCRRC
PDCPPDCP
RLCRLC
MACMAC
PHYPHY
UE
RRCRRC
PDCPPDCP
RLCRLC
MACMAC
PHYPHY
eNB
Control Plane User Plane
Radio bearers
Logical channels
Transport channels
Physical channels
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Frame structure
#0 #1 #2 #3 #19
One slot, Tslot = 15360Ts = 0.5 ms
One radio frame, Tf = 307200Ts=10 ms
#18
One subframe
WCDMA/HSPA:
LTE:
#0 #1 #2 #3 #14
One slot, 2/3ms
One radio frame, 10 ms
#13
One subframe, 2ms
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Channel Dependent Scheduling and Link adaptation
Frequency-domain & Time-domain adaptation Focus transmission power to each user’s best channel portion Adaptive modulation (QPSK, 16QAM, 64QAM)
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LTE PHY – Main Technologies
MIMOMultiple Input Multiple Output
OFDMOrthogonal Frequency Division Multiplexing
NTx Transmit Antennas
NRxReceive
Antennas
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LTE PHY - MIMO Basics Minimum antenna requirement: 2 at eNodeB 2 Rx at UE Transmission of several independent data streams in parallel
=> increased data rate The radio channel consists of NTx x NRx paths Theoretical maximum rate increase factor = Min(NTx x NRx)
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Sub-carriers are orthogonal
All the sub-carriers allocated to a given user are transmitted in parallel.
The carrier spacing is 15kHz
LTE PHY - OFDM Basics
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Requirement comparisonRequirement HSPA (Rel 6) LTE
Peak data rate 14 Mbps DL5.76 Mbps UL
100 Mbps DL50 Mbps UL
5% packet call throughput 64 Kbps DL5 Kbps UL
3-4x DL / 2-3x UL improvement
Averaged user throughput 900 Kbps DL150 Kbps UL
3-4x DL / 2-3x UL improvement
Control plane capacity > 200 users per cell (for 5MHz spectrum)
User plane latency 50 ms 5 ms
Call setup time 2 sec 50 ms
Broadcast data rate 384 Kbps 6-8x improvement
Mobility Up to 250 km/h Up to 350 km/h (500 km/h for wider bandwidths)
Bandwidth 5 MHz 1.25, 2.5, 5, 10, 15, 20 MHz
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Feature comparison
Feature HSPA (Rel 6) LTE
minimum TTI size 2 ms 1 ms
Modulation DL: QPSK, 16 QAMUL: QPSK
DL: QPSK, 16 QAM, 64 QAMUL: 16 QAM
HARQ Async DL,Sync UL
Async DL,Sync UL
Fast scheduling TDS (time domain) TDS and FDS (frequency domain)
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Conclusion Scalable bandwidth
Downlink and uplink peak data rates are 100 and 50 Mbit/s respectively for 20 MHz bandwidth.
MIMO
OFDM
At least 200 mobile terminals in the active state for 5MHz bandwidth.If bandwidth is more than 5MHz, at least 400 terminals should be supported.
PHY key technologies enable higher spectral efficiency, peak rate and lower latency
