Post on 30-Jul-2018
© 2
012 T
ieto
Corp
ora
tio
n
LTE (Technology brief to Students of Lund
University)
Prasad Pechetty
System Architect
Tieto,
Prasad.V.Pechetty@tieto.com
© 2012 Tieto Corporation
Table of contents
• Motivation
• LTE Network Architecture
• Channels
• Frame Structure
• LTE PHY Key aspects
2012-02-06 2
© 2012 Tieto Corporation
3GPP releases
• R99: WCDMA Evolved
• R5: HSDPA – High Speed Downlink Packet Access
• R6: HSUPA – Enhanced Uplink
• LTE – Long-Term Evolution
• LTE Advanced.
Enhanced Uplink
(HSUPA) MIMO
CPC
Rel 4 Rel 5 Rel 6
HSDPA WCDMA
R99 Rel 7 Rel 8
HSPA Evolution
LTE
= Third Generation Partnership Project
1999 2002 2004 2007 2008 2011 2012
3
HSUPA
LTE Advanced
© 2012 Tieto Corporation 5
• Higher User throughput of 3-4 times that of HSDPA (Rel.6) in downlink and 3-4 times that of enhanced Uplink (Rel.6)
• Mobility optimized for low mobile speed from 0 to 15 km/h, also supports higher mobile speeds
• Optimal cell size of 5 km, 30 km sizes with reasonable performance, and up to 100 km cell sizes supported with acceptable performance
• Supports a large number of users per cell of at least 200 users/cell (5Mhz)
• Spectrum flexibility & Co-existence with legacy standards
Motivation
© 2012 Tieto Corporation
3G Evolution • Radio side ( LTE – Long Term Evaluation)
• Spectral flexibility, Spectral efficiency, User throughput & Latency
• Simplification of the Radio Network
• Efficient support og packet based services ( MBMS, IMS etc)
• Network side ( SAE – System Architecture Evaluation) • Improvement in latency, capacity & throughout
• Simplification of the core network
• Optimization for IP traffic and services
• Simplified support and handover to non-3GPP access Technologies
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© 2012 Tieto Corporation
LTE is Packet Only • 2G/3G and CDMA
• LTE
Packet
domain
Circuit
domain
2G /3G
Access
Packet
domain
LTE
Access
CS Bearer
PS Bearer
PS Bearers
Voice
Internet
Access
Voice or
TV
Internet
Access
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© 2012 Tieto Corporation 10
LTE Network Architecture • The LTE architecture comprises of
radio access network and core network • The evolved radio access network is
referred to as E-UTRAN (Evolved-UTRAN)
• The evolved core network is referred to as EPC
(Evolved Packet Core network)
• This is collectively referred to as Evolved packet system
eNB
MME / S-GW MME / S-GW
eNB
eNB
S1
S1
S1
S1
X2
X2X
2
E-UTRAN
Ref:3GPP TS 36.300 V8.7.0
© 2012 Tieto Corporation 11
Functions of eNodeB :
• Functions for Radio Resource Management, i.e Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink
• IP header compression and encryption of user data stream;
• Selection of an MME at UE attachment when no routing to an MME can be determined from the information provided by the UE
• Routing of User Plane data towards Serving Gateway
• Scheduling and transmission of paging messages (originated from the MME);
• Scheduling and transmission of broadcast information
eNB
MME / S-GW MME / S-GW
eNB
eNB
S1
S1
S1
S1
X2
X2
X2
E-UTRAN
© 2012 Tieto Corporation 12
• MME
• Inter CN node signalling for mobility between 3GPP access networks
• Idle mode UE Reachability
• Tracking Area list management (for UE in idle and active mode)
• PDN GW and Serving GW selection
• MME selection for handovers with MME change
• SGSN selection for handovers to 2G or 3G 3GPP access networks
• Roaming
• Authentication
• S-GW
• The local Mobility Anchor point for inter-eNB handover
• Lawful Interception
• Packet routing and forwarding
Functions of MME & S-GW
eNB
MME / S-GW MME / S-GW
eNB
eNB
S1
S1
S1
S1
X2
X2
X2
E-UTRAN
© 2012 Tieto Corporation
IP Transport Network
LTE Network
• 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
X2 X2
X2 X2
S1 S1 S1
AGW AGW
eNB
eNB
eNB
eNB
eNB
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© 2012 Tieto Corporation
NAS
RRC
PDCP
RLC
MAC
PHY
UE
RRC
PDCP
RLC
MAC
PHY
eNB
NAS
MME
Handovers
Ciphering
Segmentation
HARQ
Modulation,
coding
NAS
RRC
PDCP
RLC
MAC
PHY
UE
RRC
PDCP
RLC
MAC
PHY
eNB
Control Plane User Plane
Radio bearers
Logical channels
Transport channels
Physical channels
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Protocol overview
© 2012 Tieto Corporation 17
LTE Transport Channels
• Broadcast Channel (BCH)
• Paging Channel (PCH)
• Downlink Shared Channel (DL-SCH)
• Multicast Channel (MCH)
• Uplink Shared Channel (UL-SCH)
• Random Access Channel (RACH)
© 2012 Tieto Corporation 18
LTE Physical Channels • DL
• Physical Broadcast Channel (PBCH)
• Physical Control Format Indicator Channel (PCFICH)
• Physical Downlink Control Channel (PDCCH)
• Physical Hybrid ARQ Indicator Channel (PHICH)
• Physical Downlink Shared Channel (PDSCH)
• Physical Multicast Channel (PMCH)
• UL • Physical Uplink Control Channel (PUCCH)
• Physical Uplink Shared Channel (PUSCH)
• Physical Random Access Channel (PRACH)
© 2012 Tieto Corporation 19
BCH PCH DL-SCHMCH
Downlink
Physical channels
Downlink
Transport channels
PBCH PDSCHPMCH PDCCH
Uplink
Physical channels
Uplink
Transport channels
UL-SCH
PUSCH
RACH
PUCCHPRACH
Mapping between Transport and
Physical Channels
© 2012 Tieto Corporation 21
LTE Frame Structure
• Frame Type 1: FDD
#0 #1 #2 #3 #19#18
One radio frame, Tf = 307200Ts = 10 ms
One slot, Tslot = 15360Ts = 0.5 ms
One subframe
• Frame Type 2: TDD
One slot,
Tslot=15360Ts
GP UpPTSDwPTS
One radio frame, Tf = 307200Ts = 10 ms
One half-frame, 153600Ts = 5 ms
30720Ts
One subframe,
30720Ts
GP UpPTSDwPTS
Subframe #2 Subframe #3 Subframe #4Subframe #0 Subframe #5 Subframe #7 Subframe #8 Subframe #9
© 2012 Tieto Corporation 22
DL& UL Configurations in TDD
Uplink-
downlink
configura
tion
Downlink-
to-Uplink
Switch-
point
periodicit
y
Subframe number
0 1 2 3 4 5 6 7 8 9
0 5 ms D S U U U D S U U U
1 5 ms D S U U D D S U U D
2 5 ms D S U D D D S U D D
3 10 ms D S U U U D D D D D
4 10 ms D S U U D D D D D D
5 10 ms D S U D D D D D D D
6 5 ms D S U U U D S U U D
© 2012 Tieto Corporation
One downlink slot, Tslot
sub
carr
iers
NB
WDL
Resource element
OFDM symbolsDLsymbN OFDM symbolsDLsymbN
NB
Wsu
bca
rrie
rsR
B
Resource block
RBBW
DLsymb NN resource elements
RBBW
DLsymb NN resource elements
Resource Grid
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© 2012 Tieto Corporation 24
DL Reference Signals • To carry out downlink coherent demodulation
• Transmitted during the first and third last OFDM symbols of each slot with a frequency-domain spacing of six subcarriers
• Four symbols per Slot
• Is the product of a pseudo-random sequence and an orthogonal sequence.
© 2012 Tieto Corporation
Sampling Frequency and BW
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Bandwidth 1.4
MHz
3
MHz
5
MHz
10
MHz
15
MHz
20
MHz
Sampling
Frequency
1.92
MHz
3.84
MHz
7.68
MHz
15.36
MHz
23.04
MHz
30.72
MHz
FFT Size 128 256 512 1024 1536 2048
RBs 6 15 25 50 75 100
© 2012 Tieto Corporation
• MIMO
Multiple Input Multiple Output
• OFDM Orthogonal Frequency Division Multiplexing
NTx Transmit
Antennas
NRx Receive
Antennas
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© 2012 Tieto Corporation
• Sub-carriers are orthogonal
• All the sub-carriers allocated to a given user are transmitted in parallel.
• The carrier spacing is 15kHz
OFDM
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© 2012 Tieto Corporation
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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© 2012 Tieto Corporation 31
• An example of how samples are mapped:
• Maps onto resources on each of the antenna ports
• The values of the precoding matrix are selected from the codebook configured in the eNodeB and the UE.
)(
)(
)(
)(
)(
)1(
)0(
)1(
)0(
ix
ix
iW
iy
iy
P
)(iW
MIMO
© 2012 Tieto Corporation
Requirement comparison Requirement HSPA (Rel 6) LTE
Peak data rate 14 Mbps DL
5.76 Mbps UL
300 Mbps DL
150 Mbps UL
5% packet call throughput 64 Kbps DL
5 Kbps UL
3-4x DL / 2-3x UL
improvement
Averaged user throughput 900 Kbps DL
150 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 1.4, 3, 5, 10, 15, 20 MHz
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© 2012 Tieto Corporation
Feature comparison
Feature HSPA (Rel 6) LTE
minimum TTI size 2 ms 1 ms
Modulation DL: QPSK, 16 QAM
UL: QPSK
DL: QPSK, 16 QAM, 64
QAM
UL: 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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© 2012 Tieto Corporation
Conclusion • Scalable bandwidth
• Downlink and uplink peak data rates are 300 and 150 Mbps respectively for 20 MHz band width.
• 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
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