Transcript 67440945-LTE-Workshop-Ericsson-v1-0

LTE Introduction
August, 2011
Introduction to LTE/SAE
› 4 main limitations for 3G networks
– 1.- The maximum bit rates are still low compared with other
systems.
– 2.- The latency of user plane traffic (UMTS: >30 ms) and of resource
assignment procedures (UMTS: >100 ms) is too big to handle traffic
with high bit rate variance efficiently.
– 3.- The terminal complexity for WCDMA systems is quite high,
making equipment expensive, resulting in poor performing
implementations of receivers and inhibiting the implementation of
other performance enhancements.
– 4. -Current network cost
LTE/SAE Workshop | August 2011 | Page 2
Introduction to LTE/SAE
› What are the LTE challenges
The Users’ expectation…
..leads to the operator’s challenges
• Best price, transparent flat rate
• Full Internet
• Faster connection
• reduce cost per bit
• provide high data rate
• provide low latency
User experience will have
an impact on ARPU
Price per Mbyte has to be
reduced to remain profitable
Throughput
HSPA
LTE
Latency
HSPA
Cost per MByte
LTE
UMTS
HSPA
HSPA+
LTE
LTE: lower cost per bit and improved end user experience
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Introduction to LTE/SAE
› LTE Network status (May 2011)
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Introduction to LTE/SAE
› LTE devices (July 2011)
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Introduction to LTE/SAE
› LTE Standards Development
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Introduction to LTE/SAE
› LTE Requirements
– Data Rate: Peak data rates target 100 Mbps (downlink) and 50
Mbps (uplink) for 20 MHz spectrum allocation, assuming 2 receive
antennas and 1 transmit antenna at the terminal
– Throughput: Target for downlink average user throughput per MHz
is 3-4 times better than release 6. Target for uplink average user
throughput per MHz is 2-3 times better than release 6. (release 6 –
HSPA)
– Spectrum Efficiency: Downlink target is 3-4 times better than
release 6. Uplink target is 2-3 times better than release 6
– Latency: The one-way transit time between a packet being
available at the IP layer in either the UE or radio access network
and the availability of this packet at IP layer in the radio access
network/UE is less than 5 ms
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Introduction to LTE/SAE
› LTE Requirements
– Interworking: Interworking with existing UTRAN/GERAN systems
and non-3GPP systems is ensured.
– Mobility: The system is optimized for low
mobile speed (0-15 km/h), but higher mobile
speeds are supported as well including high
speed train environment as special case.
– Quality of Service: End-to-end Quality
of Service (QoS) is supported
– Multimedia Broadcast Multicast Services
– All IP network
› Core and Access Network
LTE/SAE Workshop | August 2011 | Page 8
Introduction to LTE/SAE
› LTE Requirements
– Scalable BW: Scalable bandwidths of 5, 10, 15, 20 MHz are
supported. Also bandwidths smaller than 5 MHz are supported for
more flexibility, i.e. 1.4 MHz and 3 MHz for FDD mode
– Supported several options for MIMO configuration
– Duplexing modes of operation: FDD and TDD
– Coverage
› Full performance up to 5 km
› Slight degradation 5 km – 30 Km
› Operation up to 100 km should not be precluded by standard
– New radio access techniques:
› Downlink: OFDMA, Uplink: SC-FDMA
– SON (Self Organizing Network)
› Self-configuration network, self-optimising network
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Introduction to LTE/SAE
› Overview LTE and SAE
E-UTRAN Evolved UMTS (Universal Mobile
Telecommunication System) Terrestrial Radio
Access Network
PCRF Policy Control and Charging Rules
Function
EPC Evolved Packet Core
PDN Packet Data Network
EPS Evolved Packet System
PS Packet Switched
GERAN GSM EDGE Radio Access Network
PSTN Public Switched Telephone Network
GGSN Gateway GPRS Support Node
RNC Radio Network Controller
GW Gateway
SAE System Architecture Evolution
HSS Home Subscriber Server
SGSN Serving GPRS Support Node
IMS Internet Protocol Multimedia Service
SGi Reference Point in LTE
LTE Long Term Evolution (of UMTS)
UTRAN UMTS (Universal Mobile
Telecommunication System) Terrestrial Radio
Access Network
MME Mobility Management Entity
eNB Enhanced Node B
LTE/SAE Workshop | August 2011 | Page 10
Introduction to LTE/SAE
LTE UE Categories
•
•
•
All categories support 20 MHz
64QAM mandatory in downlink, but not in uplink (except Class 5)
2x2 MIMO mandatory in other classes except Class 1
Class 1
Peak rate DL/UL
10/5 Mbps
Class 2
Class 3
Class 4
Class 5
50/25 Mbps 100/50Mbps 150/50Mbps 300/75Mbps
RF bandwidth
20 MHz
20 MHz
20 MHz
20 MHz
20 MHz
Modulation DL
64QAM
64QAM
64QAM
64QAM
64QAM
Modulation UL
16QAM
16QAM
16QAM
16QAM
64QAM
Yes
Yes
Yes
Yes
Yes
Optional
2x2
2x2
2x2
4x4
Rx diversity
MIMO DL
LTE/SAE Workshop | August 2011 | Page 11
Introduction to LTE/SAE
› Multiple Access Methods
User 2
User 1
TDMA
• Time Division
User 3
User ..
OFDMA
FDMA
CDMA
• Frequency Division
• Code Division
• Frequency Division
• Orthogonal subcarriers
f
f
t
t
f
f
f
t
f
t
f
OFDM is the state-of-the-art and most efficient and robust air interface
LTE/SAE Workshop | August 2011 | Page 12
f
Introduction to LTE/SAE
Downlink: OFDM Orthogonal Frequency Division Multiplexing
• Orthogonal: all other subcarriers zero at sampling point
• Parallel transmission using a large number of narrowband “sub-carriers”
• Sub carrier spacing 15 kHz (MBMS also 7.5 kHz)
Benefits
+
+
+
Robust against ISI
Flexible BW
Classic technology
(WLAN, WiMax)
Δf=15kHz
Drawbacks
-
Sensitive to freq
errors
-
High PAPR (not
suitable for uplink)
f
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Introduction to LTE/SAE
› Downlink – OFDM with Cyclic Prefix
– Cyclic Prefix:
› Guard band at the start of each symbol which provides protection against multi-path
delay spread.
› Represents and overhead
› The duration of CP should be greater than the multi-path delay spread
– LTE specifies both normal and extended CP (high delay spread)
Copy
TCP  4.7 s
Configuration, f
CP
length
Symbols
per slot
Normal
15 kHz
4.7 s*
7
15 kHz
16.7 s
6
7.5 kHz
33.3 s
3
Extended
TCP-E  16.7 s
TSYMBOL=66.67 s =
1/15 KHz
* First symbol of each slot has a CP length of 5.2 s
In the case of the 7.5 KHz subcarrier spacing, the resource block
consist of 24 subcarriers, (RB bandwidht is still 180 KHz)
– The IFFT is used to generate a time domain OFDMA symbol from a combination of the
modulated subcarriers
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Introduction to LTE/SAE
› SC-FDMA (Single Carrier Frequency Division Multiple
Access)
– Solution for uplink in LTE
– Reduce PAPR but requires additional baseband processing
› Single stream over the air
– Is a power-efficient adaptation of OFDMA
– Lower cost UEs
› Supports larger cells due the better link budget
› Improved UL signal quality at the cell edge
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Introduction to LTE/SAE
› Comparing OFDMA & SC-FDMA
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Introduction to LTE/SAE
› LTE Frame Structure ( FDD mode)
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Introduction to LTE/SAE
› LTE Frame Structure (TDD mode)
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Introduction to LTE/SAE
› LTE Physical Resource Block
– PRB (Physical Resource Block) is 12 sub-carriers (15KHz) during one 0.5
ms slot
– One Resource Block =
12 x 7 = 84 Resource Elements
– The basic TTI is 1 ms
– TTI (Transmission Time Interval)
› Minimal unit assigned by
the scheduling strategy
– Modulation:
› QPSK
› 16QAM
› 64QAM
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Introduction to LTE/SAE
› Flexible Bandwidths, Parameters
› ETSI parameters
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Introduction to LTE/SAE
› Frecuency
Bands in LTE
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Introduction to LTE/SAE
› E-UTRAN Protocol Stack (Control Plane)
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Introduction to LTE/SAE
› E-UTRAN Protocol Stack (User Plane)
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Introduction to LTE/SAE
› Main Physical Channels
Access Network
Traffic
HARQ feedback
CQI reporting
UL scheduling request
RI reporting for MIMO
related feedback
Broadcast MIB
Slot/Frame
synchronization &
Cell Id identification
Cell reference,
Traffic
Control information
Paging
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eNode-B
HARQ feedback
Transport format
UL scheduling grant
Resource allocation
Introduction to LTE/SAE
› Mapping Physical Channels of E-UTRAN
– Logical Channel ->Defined by the type of information that it carries
– Transport Channel -> Defined by how and with what characteristics
the information is transmitted (Transport Block and Format)
– Physical Channel ->Defined by actual physical layer characteristics,
bandwidth, size FFT
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Introduction to LTE/SAE
› Example Downlink Structure 5 MHz
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Introduction to LTE/SAE
› Example Uplink Structure 5 MHz
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Introduction to LTE/SAE
› MIMO concepts
– Offer significant performance improvement over single antenna
› increased cell capacity
› Increased cell range/area
› Increased throughput
› Quality of experience for all users
– The technique involves several uncorrelated antennas in the TX and
RX
– Since the RX can distinguish between the various uncorrelated
antennas, it is possible to transmit different data STREAMs in
different paths
– 3GPP has specified the following antenna configuration
› 2 x 2 MIMO, 4 x 4 MIMO
LTE/SAE Workshop | August 2011 | Page 28
Introduction to LTE/SAE
› Different transmission types
SIMO 1X2
eNodeB
Stream 1
UE
Rx Diversity
TxDiv 2X2
Stream 1
UE
eNodeB
Rx Diversity
MIMO 2X2
eNodeB
Stream 1
UE
Stream 2
MIMO
LTE/SAE Workshop | August 2011 | Page 29
Introduction to LTE/SAE
› Example of LTE options
Techniques
Benefits
Transmit diversity
Increase cell coverage and reliability
SU-MIMO
Increase user throughput/cell throughput
MU-MIMO
Increase number of users/cell capacity and throughput
LTE/SAE Workshop | August 2011 | Page 30
Introduction to LTE/SAE
› Access Networks LTE
– The basic building blocks of the E-UTRA access network are the eNB
(Evolved Node B) plus backhaul – and nothing else
› Selection of MME at attachment (more than one MME can be connected to the
same eNB)
› Scheduling of paging messages
› Routing of user plane to S-GW
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Introduction to LTE/SAE
› X2 interface
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Introduction to LTE/SAE
› LTE Radio Interface
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Introduction to LTE/SAE
› Transport Network Solutions / RBS6000
– The Ericsson RAN evolves towards a common RAN with a common
RBS (RBS 6000) to support all RATs
› Common shared IP infrastructure for all Ericsson RAN
RBS 6000
SIU
GSM
WCDMA
LTE
Site
Power
Transport
2G BTS 3G NodeB LTE eNodeB
(Site Integration Unit)
Integral part of the RBS, providing
- Aggregation
- Site size reductions
- Power reductions
- Opex reductions
- Transport cost optimization
– One backhaul, not three
– Reduced backhaul cost
SIU
Legacy TDM
equipment
RBS Site
Transport Network
LTE/SAE Workshop | August 2011 | Page 34
GE/FE or IP over TDM (ML-PPP)
Introduction to LTE/SAE
› Transport Network Solutions
› IP RAN solution
- Several transport network media
IP RAN Reference solution
Site
solution
Site solution
Microwave
PSTN
BSC
2G BTS
BTS
SIU
Copper
Metro
Ethernet
M-PBN
RNC
3G Node B
IP Core
Fiber
BTS
LTE eNodeB
RBS Site
LTE/SAE Workshop | August 2011 | Page 35
SGW
Mobile Backhaul
Switch Site
Internet
Introduction to LTE/SAE
› Transport Network Solutions
› SIU
Sync Port
Clock input/output
(to eNodeB/NodeB)
TDM Access Ports
Up to 16 E1/T1s for GSM RBSes, Legacy
RBSes requireing circuit emulation or PDH
based transport networks (using IP over
E1/T1)
Ethernet ports
8 Ethernet ports to be used for Transport
Network connectivity as well as
connectivity to NodeBs, eNodeBs and
other site equipment.
Console Port
Fast Ethernet
Power Supply
Front size
power access
(+ 24/-48V)
›
›
›
›
1 Sync port, RS422 (1 PPS input, 1PPS output)
1 Fast Ethernet ”console port” (Telnet access)
16 E1/T1 ports (twisted pair cables 120/100 ohms, 2 ports/contact)
8 Gigabit Ethernet ports (4 electrical 10/100/1000Mbps, 4 SFP/eletrical combo ports
LTE/SAE Workshop | August 2011 | Page 36
Introduction to LTE/SAE
› Multiple basestations
› Transport Network Solutions
– Mix of GSM, WCDMA and LTE
– Support for legacy basestations
› Cell site
› Common interface to the transport network
– Either Ethernet or ML-PPP TDM
GSM RBSs
› Common synchronization
BTS
L2/L3
BTS
`
Transport
Packet Abis
Gigabit Ethernet
Site LAN
SIU
WAN
NodeB
Ethernet
WCDMA RBS
CES
ET-MFX
LTE RBS
Legacy
TDMbased
RBS
eNodeB
DUL
LTE/SAE Workshop | August 2011 | Page 37
E1/T1
TDM
Transport
Introduction to LTE/SAE
› Multi-standard with RBS6000
› RBS6000 equipped with:
– GSM, WCDMA and LTE simultaneously
– SIU as aggregation
– One transport interface
› Technologies co-transported in the
transport network
– Aggregations gains reduces capacity needs
Transport Network
GE/FE or IP over TDM
LTE/SAE Workshop | August 2011 | Page 38
RBS 6000
WCDMA
GSM
LTE
Introduction to LTE/SAE
› Questions (1)
– Identify three key objectives for LTE
– Identify the following interfaces names
› eNodeB to MME
› eNodeB to S-GW
› S-GW to PDN-GW
› MME to HSS
– What is the subcarrier spacing used in all E-UTRA channel bandwidths?
– How is a „Resource Block‟ defined for the E-UTRA physical layer?
– Which is the physical channel used in LTE for paging?
– In LTE protocol architecture which component carrier signalling data
transparently from the UE to the EPC?
– What is the SIU function and why we have to use it?
LTE/SAE Workshop | August 2011 | Page 39
Introduction to LTE/SAE
› Questions (2)
– Which of the following are all valid channel bandwidth options in the set
currently defined for E-UTRA?
› a) 3 MHz, 5 MHz and 10 MHz
› b) 2 MHz, 10 MHz and 20 MHz
› c) 3 MHz, 15 MHz and 25 MHz
› d) 1.4 MHz, 7 MHz and 10 MHz
– Why does LTE use SC-FDMA in the uplink direction?
– What is the main differences between LTE, SAE, EPS and EPC?
– SU-MIMO in OFDMA involves re-use the same subcarriers form different
transmit antennas for a given user to increase peak data rate (True/False)
– MU-MIMO in OFDMA involves use same subcarriers for different user in the
same cell (True/False)
– Which are the main differences betwen the control plane and user plane?
LTE/SAE Workshop | August 2011 | Page 40
Introduction to LTE/SAE
› Exercise calculate theoretical DL Throughtput
– INPUTS
› Channel Bandwidth 10 MHz
› Modulation 64 QAM
› Code rate ¾
› MIMO 2 x 2
› Normal CP
› Operation mode FDD
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