9400 lte ran radio principles...
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9400 LTE Radio Principles - Page 1All Rights Reserved © Alcatel-Lucent 2009
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9400 LTE RAN Radio PrinciplesDescription
STUDENT GUIDE
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contents not permitted without written authorization from Alcatel-Lucent
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Terms of Use and Legal Notices
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Both lethal and dangerous voltages may be present within the products used herein. The user is strongly advised not to
wear conductive jewelry while working on the products. Always observe all safety precautions and do not work on the
equipment alone.
The equipment used during this course may be electrostatic sensitive. Please observe correct anti-static precautions.
2. Trade Marks
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All other trademarks, service marks and logos (“Marks”) are the property of their respective holders, including Alcatel-
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9400 LTE RAN Radio Principles Description
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Course Outline
About This CourseCourse outline
Technical support
Course objectives
1. Topic/Section is Positioned HereXxx
Xxx
Xxx
2. Topic/Section is Positioned Here
3. Topic/Section is Positioned Here
4. Topic/Section is Positioned Here
5. Topic/Section is Positioned Here
6. Topic/Section is Positioned Here
7. Topic/Section is Positioned Here
1. Introduction
1.1 Why the 3G LTE ?
1.2 Standardization
1.3 Key Differentiators
2. OFDMA Principles
2.1 Modulation
2.2 OFDMA Basic Concepts
2.3 OFDMA Transmitter and Receiver
2.4 SC-FDMA in UL
2.5 OFDMA and LTE
3. Air Interface Structure
3.1 Radio Frame Structure
3.2 Protocol Stack
3.3 Radio Channels
4. eUTRAN Scenarios
4.1 RRC Connection Scenarios
4.2 E-RAB and QoS
4.3 Traffic Operation
5. LTE Antenna System
5.1 Introduction
5.2 MIMO and Co
5.3 Beamforming
6. Mobility Management
6.1 Introduction
6.2 Handover
6.3 Idle Mode
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Course Outline [cont.]
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Course Objectives
Switch to notes view!
Welcome to 9400 LTE RAN Radio Principles Description
Upon completion of this course, you should be able to:
This course provides a foundation of knowledge to understand the radio principles of the 3G
LTE. This course is designed to enable you to:
* Explain what are the drivers of the LTE and what are the key differentiators of the LTE
standard* Explain what is the principle of the LTE layer 1, the OFDMA.
* Describe the structure of the radio frame and how the channels (logical, transport and
physical) are mapped on to the resources
* List and describe the steps of the RRC connection
* Describe the bearer establishment and all the radio operations required during the traffic
* Describe the different antenna systems available and explain their interest
* Describe the mechanism of mobility with the handover and with the idle mode and the
paging
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Course Objectives [cont.]
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About this Student Guide
� Switch to notes view!Conventions used in this guide
Where you can get further information
If you want further information you can refer to the following:
� Technical Practices for the specific product
� Technical support page on the Alcatel website: http://www.alcatel-lucent.com
Note
Provides you with additional information about the topic being discussed.
Although this information is not required knowledge, you might find it useful
or interesting.
Technical Reference (1) 24.348.98 – Points you to the exact section of Alcatel-Lucent Technical
Practices where you can find more information on the topic being discussed.
WarningAlerts you to instances where non-compliance could result in equipment
damage or personal injury.
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About this Student Guide [cont.]
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Self-assessment of Objectives
� At the end of each section you will be asked to fill this questionnaire
� Please, return this sheet to the trainer at the end of the training
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Instructional objectives Yes (or globally yes)
No (or globally no)
Comments
1 To be able to XXX
2
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Course title :
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Language : Dates from : to :
Number of trainees : Location :
Surname, First name :
Did you meet the following objectives ?
Tick the corresponding box
Please, return this sheet to the trainer at the end of the training
����
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Self-assessment of Objectives [cont.]
Switch to notes view!
Instructional objectives Yes (or Globally yes)
No (or globally no)
Comments
Thank you for your answers to this questionnaire
Other comments
����
Page 1
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1 Module 1Introduction
9400 LTE RAN Radio PrinciplesDescription
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First editionOlivier Guivarc’h2009-0801
RemarksAuthorDateEdition
Document History
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9400 LTE RAN Radio Principles DescriptionIntroduction
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Module Objectives
Upon completion of this module, you should be able to:
� List the drivers of the 3G LTE
� Explain the context of the standardization of the 3G LTE
� Describe the services provided to the End User
� Give an estimation of the performance of the LTE
� List the key differentiators compared to the other Radio Access technologies
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Module Objectives [cont.]
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Table of Contents
Switch to notes view!Page
1 Why 3G LTE? 71.1 Market Trends 81.2 3G Limitations 101.3 3G LTE Requirements 11
2 Standardization 122.1 What is the 3GPP? 132.2 3GPP Release 152.3 3GPP Performance 162.4 3GPP Web Site 17
3 Key Differentiators 183.1 Key Differentiators 193.2 Architecture 20
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Table of Contents [cont.]
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9400 LTE RAN Radio Principles DescriptionIntroduction
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1 Why 3G LTE?
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1 Why 3G LTE?
1.1 Market Trends
� The trend of the market is an increase and an acceleration of the data mobile traffic in the next years.
� This has been possible thanks to the introduction of:
� EV-DO with CDMA2000
� HSDPA and HSUPA with WCDMA
Mobile Data Traffic Evolution
With the recent introduction of HSDPA and EV-DO Rev A, there has been a significant increase in mobile data
traffic, with some operators quadrupling their Packet Switched traffic in one year. At this growth rate, and
with the proliferation of new applications on the network, cells in hot pots will be quickly saturated and the
network will require densification in these overloaded areas. This can be delivered by using a higher capacity
solution such as LTE. Mobile traffic growth is illustrated on this slide: mobile data traffic (in Gigabits per
year), with a typical operator in a western country with a 60 million population.
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9400 LTE RAN Radio Principles DescriptionIntroduction
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1 Why 3G LTE?
1.1 Market Trends [cont.]
� Mobile phone user population is estimated to increase to 4 billion by 2011.
� Fixed Broadband application, massively adopted, can be exported to the mobile environment.
� The millennial generation will spread in the next years their “early adopters” way of life.
� The richer ecosystem of devices allows one to be connected all the time:
� PDA, laptop, mobile phone, USB device
All these trends require some radio access networks able to carry more and more data with stringent
requirements in terms of QoS (minimum bit rate, delay, etc.).
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9400 LTE RAN Radio Principles DescriptionIntroduction
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DL: 100Mbps &
UL: 50 Mbps
OFDM & Long symbolDuration
5MHz Spectrum
Highly sensitive to Frequency
Selective Fading
1 Why 3G LTE ?
1.2 3G Limitations and LTE Response
DL: 14.4Mbps DL & UL:5.7Mbps
1.4MHz, 3Mhz, 5MHz, 10MHz,
15MHz and 20 MHz
3G
LTE
Advantages of LTE:
� Reduce the network nodes to 2 instead of 3 as compared to previous technologies (RNC + nodeB
merged into one eNodeB component): lower latency
� Based of OFDM RF transmission technology
� One single Core Network (voice applications moved to packet core network)
� IP-based network
� Scalable system bandwidth offers deployment flexibility
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1 Why 3G LTE ?
1.3 3G LTE Requirements
� Spectrum efficiency
� DL : 3-4 times
� UL : 2-3 times
� Frequency Spectrum
� Scalable bandwidth : 1.4, 3, 5, 10, 15, 20MHz
� To cover all frequencies of IMT-2000: 450 MHz to 2.6 GHz
� Peak data rate
� DL : > 100Mb/s for 20MHz spectrum allocation
� UL : > 50Mb/s for 20MHz spectrum allocation
� Latency
� C-plane : < 100ms to establish U-plane
� U-plane : < 10ms from UE to server
� Coverage
� Performance targets up to 5km, slight degradation up to 30km
� Mobility
� LTE is optimized for low speeds 0-15km/h but
� connection maintained for speeds up to 350 or 500km/h
� Handover between 3G & 3G LTE
� Real-time < 300ms
� Non-real-time < 500ms
LTE is aimed at minimizing cost and power consumption while ensuring backward-compatibility and a cost
effective migration from UMTS systems. Enhanced multicast services, enhanced support for end-to-end
Quality of Service (QoS) and minimization of the number of options and redundant features in the
architecture are also being targeted.
The spectral efficiency in the LTE DownLink (DL) will be 3 to 4 times of that of Release 6 HSDPA while in the
UpLink (UL), it will be 2 to 3 times that of Release 6 HSUPA. The handover procedure within LTE is intended
to minimize interruption time to less than that of circuit-switched handovers in 2G networks. Moreover the
handovers to 2G/3G systems from LTE are designed to be seamless.
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9400 LTE RAN Radio Principles DescriptionIntroduction
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2 Standardization
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2 Standardization
2.1 What is the 3GPP?
� 3GPP Specified Radio Interfaces
� 2G radio: GSM, GPRS, EDGE
� 3G radio: WCDMA, HSPA, LTE
� 4G radio: LTE Advanced
� 3GPP Core Network
� 2G/3G: GSM core network
� 3G/4G: Evolved Packet Core (EPC)
� 3GPP Service Layer
� GSM services
� IP Multimedia Subsystem (IMS)
� Multimedia Telephony (MMTEL)
� Support of Messaging and other OMA functionality
� Emergency services and public warning
� Etc.
The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunication associations, to make a globally applicable third generation 3G mobile phone system specification within the scope of the International Mobile Telecommunication-2000 project of the International Telecommunication Union (ITU). 3GPP specifications are based on evolved Global Systel for Mobile Communication (GSM) specifications. 3GPP standardization encompasses Radio, Core Network and Service architecture.
The groups are the European Telecommunications Standarts Institute, Association of Radio Industries and Businesses/Telecommunication Technology Committee (ARIB/TTC) (Japan), Alliance for Telecommunications Industry Solutions (North America) and (South Korea). The project was established in December 1998.
3GPP should not be confused with 3rd Generation Partnership Project 2 (3GGP2), which specifies standards for another 3G technology based on IS-95 (CDMA), commonly known as CDMA2000.
The 3GPP has specified the following standards:
� GSM
� GPRS
� GERAN
� WCDMA
� HSPA (HSDPA and HSUPA)
3GPP2 was born out of the International Telecommunication Union's (ITU) International Mobile Telecommunications “IMT-2000” initiative, covering high speed, broadband, and Internet Protocol (IP)-based mobile systems featuring:
� network-to-network interconnection,
� feature/service transparency,
� global roaming,
� seamless services independent of location.
IMT-2000 is intended to bring high-quality mobile multimedia telecommunications to a worldwide mass market by achieving the goals of increasing the speed and ease of wireless communications, responding to the problems faced by the increased demand to pass data via telecommunications, and providing "anytime, anywhere" services.
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2 Standardization
2.2 3GPP Release Concept
201120102009200820072006200520042003200220012000
R99 R4 R5 R6 R7 R8 R9 R10
HighSpeed
Accesses
IP CoreNetwork
Services
UM
TS
HS
PA
DL
HS
PA
UL
LTE
LTE
Adv
HS
PA
+
EP
C
Com
mIM
S
IMS
MM
Tel
Each release incorporates hundreds of individual standards documents, each of which may have been through
many revisions 3GPP web site:
� http://www.3gpp.org
All the specifications are free.
� http://www.3gpp.org/ftp/Specs/html-info/36-series.htm
� Series 36 defines 3G LTE.
� TS 36.201
� Evolved Universal Terrestrial Radio Access (E-UTRA); Long Term Evolution (LTE) physical layer ->
General description
� TS 36.300
� Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access
Network (E-UTRAN) -> Overall description
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9400 LTE RAN Radio Principles DescriptionIntroduction
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3 Key Differentiators
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3 Key Differentiators
3.1 Key LTE Features to Overcome Challenges
A common evolution…
OFDM MIMO Flat IP
Robust modulation in dense
environmentsOFDMA (DL) / SC-FDMA (UL)
Increased spectral efficiency. Simplified Rx design cheaper
UE Scalable - go beyond 5 MHz limitation
Increased link capacity
Multiple-input, multiple-output UL& DL.
Collaborative MIMO (UL). Overcome multi-path
interference
Flat, scalableShort TTI: 1 ms (2 ms for HSPA). Backhaul based on IP / MPLS transport. Fits
with IMS, VoIP, SIP
L
T
E
GSM/UMTS
GSM/EDGE
GSM/EDGE
1X/EV-DO RevA
1X/EV-DO RevA
B/A+
HSPA+
UMTS/HSPA+
TD-SCDMA
WIMAX
…introducing highly efficient technologies
4G“3.9G”3G
IMT-Advanced family
Definition in progress by ITU-R
IMT-2000 family
•100 Mbps peak, mobile
•1 Gbps peak, fixedLTE introduces the building blocks of 4G
1.4MHz 3MHz 20MHz10MHz5MHz
LTE bandwidths options
CDMA2000 1X
LTE introduced in Rel 8
� Minor improvements in Rel 9 and Rel 10
Significantly increased data throughput
� Downlink target 3-4 times greater than HSDPA Release 6
� Uplink target 2-3 times greater than HSUPA Release 6
Increased cell edge bit rates
� Downlink: 70% of the values at 5% of the Cumulative Distribution Function (CDF)
� Uplink: same values at 5% of the Cumulative Distribution Function (CDF)
Significantly reduced latency
High mobility
Cell ranges up to 5 km; with best throughput, spectrum efficiency and mobility. Cell ranges up to 30 km;
Mobility with some degradation in throughput and spectrum efficiency permitted. Cell ranges up to 100 km;
Supported; degradations accepted
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9400 LTE RAN Radio Principles DescriptionIntroduction
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3 Key Differentiators
3.2 Architecture
EPS = eUTRAN + ePC
� Long Term Evolution (LTE) is the newest 3GPP standard for mobilenetwork technology.
P-GWS-GW
HSS
PDN
MGW
IMS
Transport
PCRF
PSTN
User and control
Control only
LTE
OFDM
SC-FDMA
eUTRAN
ePC
All-IP network carries all types of traffic, including VoIP.
Provides control functions for LTE access networks.
Routes and forwards user data packets to eNodeB.
Connects UE to external packet data networks.
Controls QoS policy for each service data flow that passes through the SGW and PGW.
IMS network provides services, including VoIP.
S1-MME
S1-U S5/S8
Gx
SGi
SGi
S6a
S11
MME
x2
Gxc
� The goal of the System Architecture Evolution (SAE) effort in 3GPP is to develop a framework for the
evolution and migration of current systems to a system which supports the following:
� high data rates
� low latency
� packet-optimized (all IP network)
� provides service continuity across heterogeneous access networks
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9400 LTE RAN Radio Principles DescriptionIntroduction
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End of ModuleIntroduction
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2All Rights Reserved © Alcatel-Lucent 2009
Module 2OFDMA Principles
9400 LTE RAN Radio PrinciplesDescription
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First editionLast name, first nameYYYY-MM-DD01
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 3
Module Objectives
Upon completion of this module, you should be able to:
� Explain the basic concepts of OFDM
� Describe a basic OFDMA transmitter and receiver
� Explain the application of OFDMA in LTE
� Describe the modulation used in 3G LTE
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Module Objectives [cont.]
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
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Table of Contents
Switch to notes view!Page
1 Modulation 71.1 Introduction 81.2 Modulation in LTE 101.3 Constellation 111.4 Link Adaption & Robustness 14
2 OFDMA Basic Concepts 162.1 Carrier and Bandwidth 182.2 OFDMA principles 202.3 Notion of Orthogonality 252.4 LTE Sub-carrier 302.5 Inter-symbol interference 32
3 OFDMA Transmitter and Receiver 363.1 OFDMA Transmitter 373.2 OFDMA Receiver 41
4 SC-FDMA in UL 424.1 Difference between DL and UL 434.2 Benefits 44
5 OFDMA and LTE 455.1 OFDMA parameter for LTE 46
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Table of Contents [cont.]
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
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1 Modulation
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
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1 Modulation
1.1 Introduction
� A baseband signal can not be sent directly to an antenna
� The signal is not broadcast over the air interface
� The baseband signal or “message” is carried by a carrier over the air interface
� The carrier is modulated by the baseband signal by the transmitter and demodulated by the receiver
message
transmitted signal
carrier
Modulator Demodulatormessage
Transmitter Receiver
The modulation allows one to mix the message and the carrier
There are 3 ways to modulate the carrier:
� The amplitude: the receiver can identify the bit by analyzing the amplitude
� The frequency
� The phase
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1 Modulation
1.2 Modulation in LTE
� The 3G LTE uses 3 Quadrature Amplitude Modulations (QAMs) depending on the radio quality.
� QAM uses both the amplitude and the phase.
� The LTE supports in DL and UL the following modulations:
� QPSK, the most robust but the less efficient
� 16-QAM
� 64-QAM, the less robust but the most efficient
Data bits 0 1 0 0 1
Unmodulated carrier
Amplitude Modulation (AM)
Frequency Modulation (FSK)
(Differential) Phase Modulation (DPSK)
QAM is a modulation method modifying the phase and the amplitude of the carrier signal.
QAM symbols are represented by the carrier signal being transmitted with specific phase / amplitude
(dictated by the message), for finite periods of time.
One symbol is identified by a Q and an I value.
Transmission channels with a limited bandwidth limit the amount of symbols per second (Baud rate) that can
be transmitted.
To increase the bit per sec (bps) capacity of a channel, while keeping the Baud rate at the low values imposed
by the channel bandwidth, the symbols carry (represent) more than one single bit.
Symbols will represent a number of n bits, increasing the channel capacity by a factor of n.
The price paid is the presence of multiple symbols in the channel, increasing the probability of incorrect
symbol identification at the receiver.
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
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1 Modulation
1.3 Constellation
� The QPSK is the most robust modulation. It can be represented by a constellation:
� The radius, R, represents the amplitude.
� The angle, φ, represents the phase.
I
Q
R
φ
� There are 1 amplitude but 4 phases to 4 different states.
� 2 bits can be coded with 1 QPSK symbol.
00
0111
10
By analyzing the phase and the amplitude, the receiver
can identify the bits
01 11
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
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1 Modulation
1.3 Constellation [cont.]
� The 16-QAM can modulate 4 bits per symbol.
modulation technique
nu
mb
er o
f sy
mb
ols
nu
mb
er o
f b
its
per
sym
bo
l
bit
rat
e / B
aud
ra
te
number of
amp
litu
des
ph
ases constellation
4QAM (QPSK)
24 2/1 1 4
01 11
00 10
Q
I-1 +1+1
-1
16QAM 416 4/1 3 12
not all combinations are
used
0010 0110 1110 1010
0011 0111 1111 1011
0011 0101 1101 1001
0000 0100 1100 1000
Q
I-1-3 +3+1
+3
+1
-1
-3
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 12
000101 001101 011101 010101 110101 111101 101101 100101
000111 001111 011111 010111 110111 111111 101111 100111
000110 001110 011110 010110 110110 111110 101110 100110
000010 001010 011010 010010 110010 111010 101010 100010
000011 001011 011011 010011 110011 111011 101011 100011
000001 001001 011001 010001 110001 111001 101001 100001
000000 001000 011000 010000 110000 111000 101000 100000
000100 001100 011100 010100 110100 111100 101100 100100
Q
I-1-3-5-7 +7+5+3+1
+3
+5
+7
+1
-1
-3
-5
-7
1 Modulation
1.3 Constellation [cont.]
� The 64-QAM can modulate 6 bits per symbol.
modulation technique
nu
mb
er o
f sy
mb
ols
nu
mb
er o
f b
its
per
sym
bo
l
bit
rat
e / B
aud
ra
te
number of
amp
litu
des
ph
ases constellation
64QAM 664 6/1 9 52
not all combinations are
used
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 13
1 Modulation
1.4 Link Adaption & Robustness
� In reception, it may be difficult to make the distinction between 2 states, i.e. 2-bit sequence. If the wrong state is selected, there are errors of reception.
000101 001101 011101 010101 110101 111101 101101 100101
000111 001111 011111 010111 110111 111111 101111 100111
000110 001110 011110 010110 110110 111110 101110 100110
000010 001010 011010 010010 110010 111010 101010 100010
000011 001011 011011 010011 110011 111011 101011 100011
000001 001001 011001 010001 110001 111001 101001 100001
000000 001000 011000 010000 110000 111000 101000 100000
000100 001100 011100 010100 110100 111100 101100 100100
Q
I-1-3-5-7 +7+5+3+1
+3
+5
+7
+1
-1
-3
-5
-7
The use of higher-order modulation provides the possibility for higher bandwidth utilization, that is the
possibility to provide higher data rates within a given bandwidth.
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 14
1 Modulation
1.4 Link Adaption & Robustness
� Before processing the data (bit stream) to send it on the air interface, the transmitter performs the encoding, to be able to detect or correct errors of reception.
� The amount of parity bits is defined by a rate, called coding rate
10011100
Bit stream
Encoder 1101011111110101
Parity bits
2
1==rofBitTotalNumbe
efulBitNumberOfUsCodingRate
If the coding rate = ½, the number of bits
transmitted on the air interface is multiplied
by 2
The typical coding rates are ½, 2/3, ¾.
The coding methods are:
� Convolutional
� Turbo
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 15
1 Modulation
1.4 Link Adaption & Robustness [cont.]
� The combination of the modulation and the channel coding (identified by its rate) forms one of the possible Modulation and Coding Schemes
� The link adaptation is done by the selection of the most adapted modulation to the current radio conditions.
64 QAM
16 QAM
QPSK
Radio Quality
Spectrum efficiency
The 3GPP defines 32 possible MCS
MCS corresponding to the CQI index such that the PDSCH could be received with a transport block error
probability not exceeding 10 %
The best modulation does not always give the best performance. If the radio quality is not good enough, the
receiver is not able to correctly decode the modulation. It may be more efficient to select a less robust
modulation depending on the radio quality.
Coding rate = (transport Block Size + number of CRC bits)/number of bits transmitted on RF interface
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 16
2 OFDMA Basic Concepts
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 17
2 OFDMA Basic Concepts
2.1 Carrier and Bandwidth
� TDD = Time Division Duplex
� The Uplink and the downlink transmissions are separated by the time.
� Only one bandwidth is used.
� Example: WiMAX
frequency DLtime
UL DL UL
� FDD = Frequency Division Duplex
� The Uplink and the downlink transmissions are separated by the frequency.
� 2 bandwidths are used.
� Example: WCDMA, CDMA2000
frequency
DL
UL DL timeUL
frequency
The LTE PHY is a highly efficient means of conveying both data and control information between an enhanced
base station (eNodeB) and mobile user equipment (UE). The LTE PHY employs some advanced technologies
that are new to cellular applications. These include Orthogonal Frequency Division Multiplexing (OFDM) and
Multiple Input Multiple Output (MIMO) data transmission.
Although the LTE specs describe both Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD)
to separate UL and DL traffic, market preferences dictate that the majority of deployed systems will be
FDD.
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 18
2 OFDMA Basic Concepts
2.1 Carrier and Bandwidth [cont.]
� The 3GPP specifies that the 3G LTE can be deployed in the existing IMT-2000 frequency bands.
� IMT-2000 bands: from 450 MHz to 2.6 GHz� Including WCDMA/HSPA, CDMA2000/EV-DO, and GSM bands
Band 7 (2,6 Ghz)
DLUL
2500 2570 2620 2690
Frequency(MHz)
� The bandwidth is more flexible than in the previous 3GPP standards.
� Scalable from 1.4, 3, 5, 10, 15, 20MHz
� The capacity of a cell depends strongly on its allocated bandwidth.
Frequency
5 MHz 10 MHz 20 MHz
The FDD frequency bands are paired to allow simultaneous transmission on two frequencies. The bands also
have a sufficient separation to enable the transmitted signals not to unduly impair the receiver performance.
If the signals are too close then the receiver may be "blocked" and the sensitivity impaired. The separation
must be sufficient to enable the roll-off of the antenna filtering to give sufficient attenuation of the
transmitted signal within the receive band.
With the interest in TDD LTE, there are several unpaired frequency allocations that are being prepared for
LTR TDD use. The TDD LTE allocations are unpaired because the uplink and downlink share the same
frequency, being time multiplexed.
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 19
2 OFDMA Basic Concepts
2.1 Carrier and Bandwidth [cont.]
� e-UTRAN is designed to operate in the frequency bands defined in the following table:
Spectral efficiency is increased by up to four-fold compared with UTRA, and improvements in architecture and
signalling reduce round-trip latency. Multiple Input / Multiple Output (MIMO) antenna technology should
enable 10 times as many users per cell as 3GPP’s original W CDMA radio access technology.
To suit as many frequency band allocation arrangements as possible, both paired (FDD) and unpaired (TDD)
band operation is supported. LTE can co-exist with earlier 3GPP radio technologies, even in adjacent
channels, and calls can be handed over to and from all 3GPP’s previous radio access technologies
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 20
2 OFDMA Basic Concepts
2.1 Carrier and Bandwidth [cont.]
� The supported carrier depends on the eNodeB hardware
� Bandwidth examples:
2.1 GHz
Frequency(MHz)
700 MHz
900 MHz1800 MHz
1GHz 2GHz
2.6 GHz
f
5 MHz 10 MHz
f
5 MHz 10 MHz
UL Band DL Band
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 21
2 OFDMA Basic Concepts
2.2 OFDMA Principles
� There are several ways to transmit over the frequency band and to share the resource between several devices.
FDMA• The users are
separated by the frequency
• The 3G LTE used an improved FDMA called OFDMA
TDMA• The users are
separated by the the time
• Used by the GSM
CDMA• The users are separated
by the codes. They receive data at the same time at the same frequency.
• Used in the CDMAOne, CDMA200 and WCDMA
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2 � 22
2 OFDMA Basic Concepts
2.3 Notion of Orthogonality
� In FDM, the sub-carriers are separated in the frequency domain to avoid interference between the sub-channels
� It results in a loss of spectrum efficiency because the frequency guard band can not be used to send data.
� The OFDM allows one to remove the frequency guard band.
� Benefit: There are more sub-carriers, so more symbols are sent at the same time. The orthogonality brings a better spectrum efficiency.
5 MHz
Frequency guard band
5 MHz
In OFDM, the sub-carrier frequencies are chosen so that the sub-carriers are orthogonal to each other,
meaning that cross-talk between the sub-channels is eliminated and inter-carrier guard bands are not
required. This greatly simplifies the design of both the transmitterand the receiver; unlike conventional FDM a
separate filter for each sub-channel is not required.
The orthogonality requires that the sub-carrier spacing is ∆f = k/(TU) Hertz, where TU seconds is the useful
symbol duration (the receiver side window size), and k is a positive integer, typically equal to 1. Therefore,
with N sub-carriers, the total passband bandwidth will be B ≈ N�∆f (Hz).
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 23
2 OFDMA Basic Concepts
2.3 Notion of Orthogonality [cont.]
� That leads to the representation of a sub-carrier.
Temporal domainFrequency domain
1/T2
T2
T1/T
� The duration of the symbol depends on the width of the sub-carrier.
� It is inversely proportional. The shorter the symbol, the wider the sub-carrier and vice-versa.
� The frequency center of the sub-carrier is linked to the frequency of the carrier.
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 24
2 OFDMA Basic Concepts
2.3 Notion of Orthogonality [cont.]
� The inter-channel (or inter sub-carrier) interferences are cancelled because they are located in a such way that when there is the peak for a given sub-carrier, the adjacent subcarriers are null.
4 5 6 7 8 9
x 105
-0.2
0
0.2
0.4
0.6
0.8
1
The red and the blue sub-carriers are crossing the zero point when the green
one is at its maximum
� OFDM allows high density of carriers, without generating Inter-Channel Interference (ICI).
BASIC IDEA : The channel bandwidth is divided into multiple subchannels to reduce ISI and frequency-selective
fading.
� A single wideband signal is transformed into multiple narrow band signals transmitted on orthogonal sub-
carriers
� One single stream at high rate
� Each symbol occupies the whole bandwidth
� Very short symbol duration to ensure high rate
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 25
2 OFDMA Basic Concepts
2.4 LTE Sub-carrier [cont.]
� There are different kinds of sub-carriers:
� Data sub-carrier
� Pilot Sub-carrier
� DC sub-carrier
� Guard Sub-carrier
DC sub-carrier Pilot Sub-carrierData sub-carriers
Bandwidth from 1.4 to 20 MHz
DC stands for Direct Current and it is a subcarrier that has no information sent on it. This is an important
subcarrier in OFDM based systems. It is used by the mobile device to locate the center of the OFDM frequency
band. So, if LTE does not have a DC subcarrier, it would be a big deal .
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2 � 26
2 OFDMA Basic Concepts
2.5 Inter-Symbol Interference
� What is the multipath?
� Due to the signal propagation phenomena, like reflection or diffraction, a receiver can receive several delayed versions of the same signal.
� This creates Inter-Symbol Interference (ISI).
eNode-B
t
Symbol Duration
t
Symbol Duration
Inter-symbol interference
The multi-path impact is an overlapping of 2 symbols, called Inter-Symbol Interference (ISI).
The modulation is based on the amplitude and on the phase, so in case of overlapping there are 2 different
amplitudes and phases.
The receiver is not able to decode the state of the symbol.
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2 OFDMA Basic Concepts
2.6 Cyclic Prefix
� The problem is fixed by adding a guard time between each symbol to avoid the ISI.
� The ISI is still present but is not disturbing for the receiver.
Principle : add a prefix to absorb channel effect and avoid ISI
� Cyclic prefix permits to facilitate demodulation
� The cyclic prefix transform the classical channel convolution into a cyclic convolution which permits easy
demodulation after FFT
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
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2 OFDMA Basic Concepts
2.5 Inter-Symbol Interference [cont.]
� The guard time is called the Cyclic Prefix (CP). It permits to facilitate demodulation.
� The cyclic prefix transforms the classical channel convolution into a cyclic convolution which permits easy demodulation after FFT.
Symbol Duration
Copy Copy
Useful OFDM symbol
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 29
3 OFDMA Transmitter and Receiver
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 30
3 OFDMA Transmitter and Receiver
3.1 OFDMA Transmitter
10 01
Bit stream SerialTo
Parallel
Add CPEncoding
Interleaving
11010111With a coding
rate ½
Data protection
Digital Modulation
2 bits per symbol with QPSK
“11” carried by the Sub-Ca #1
“01” carried by the Sub-Ca #2
“01” carried by the Sub-Ca #3
“11” carried by the Sub-Ca #4
Add CP
ODFMA symbol
SerialTo
Parallel&
ChannelMapping
iFFT
Frequency to time domain
In the downlink, OFDM is selected to efficiently meet E-UTRA performance requirements. With OFDM, it is
straightforward to exploit frequency selectivity of the multi-path channel with lowcomplexity
receivers. This allows frequency selective in addition to frequency diverse scheduling and one cell reuse of
available bandwidth.
Furthermore, due to its frequency domain nature, OFDM enables flexible bandwidth operation with low
complexity. Smart antenna technologies are also easier to support with OFDM, since
each sub-carrier becomes flat faded and the antenna weights can be optimized on a per sub-carrier (or block
of sub-carriers) basis.
In addition, OFDM enables broadcast services on a synchronized single frequency network (SFN) with
appropriate cyclic prefix design.
This allows broadcast signals from different cells to combine over the air, thus significantly increasing the
received signal power and supportable data rates for broadcast services.
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 31
3 OFDMA Transmitter and Receiver
3.2 OFDMA Receiver
Synchronization Remove CP FFT Sub-Carrier Demapping
Signal in baseband
Demodulation
De-interleavingDecoding1001
Bit stream
Time to frequency domain
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 32
4 SC-FDMA in UL
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 33
� OFDMA
� Advantages
� Robust against narrow-band co-channel interference
� Robust against Intersymbol interference (ISI) and fading
� High spectral efficiency
� Efficient implementation using FFT
� Drawbacks
� High Peak-to-Average Power Ratio
4 SC-FDMA in UL
4.1 Difference between DL and UL
The power limitation is more problematic in UL than in DL
Signal with high PAPR will limit the Tx power in UL and reduce coverage
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 34
LTE uses in UL a modified form of OFDMA process, called SC-FDMA� SC-FDMA = Single Carrier – Frequency Division Multiple Access
� SC-FDMA improves the peak-to-average power ratio (PAPR) compared to OFDM� Reduced power amplifier cost for mobile
� Reduced power amplifier back-off � improved coverage
eNode-B
DL : OFDMA
UL : SC-FDMA
4 SC-FDMA in UL
4.1 Difference between DL and UL
t
Amplitude
t
Amplitude
t
Amplitudet
Amplitude
+
+
In DL, use OFDM together with some PAPR reduction techniques (“clipping and filtering”, “tones reservation”,
etc…)
In UL, find an alternative to OFDM combining some of OFDM’s advantages, but with a PAPR equivalent to
single carrier’s one: DFT-Spread OFDM (DFT-SOFDM), also known as Single-Carrier FDMA (SC-FDMA)
Page 35
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 35
4 SC-FDMA in UL
4.2 Benefits
� DFT spreading of modulation symbols reduces PAPR
� In OFDM, each modulation symbols “sees” a single 15 kHz subcarrier (flat channel)
� In SC-FD-A, each modulation symbol “sees” a wider bandwidth (i.e. m x 180 KHz)
� Equalization is required in the SC-FDMA receiver
OFDMA Sub-carriers SC-FDMA Sub-carriers
5 or 10 MHz
DFT-spread OFDM (DFTS-OFDM) is a transmission scheme that can combine
the desired properties discussed in the previous sections, i.e.:
• Small variations in the instantaneous power of the transmitted signal (‘singlecarrier’ property).
• Possibility for low-complexity high-quality equalization in the frequency domain.
• Possibility for FDMA with flexible bandwidth assignment.
Due to these properties, DFTS-OFDM has been selected as the uplink transmission scheme for LTE
Page 36
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 36
5 OFDMA and LTE
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 37
5 OFDMA and LTE
5.1 OFDMA Parameter for LTE
� The width of a Sub-carrier is 15 kHz whatever the bandwidth
� The bandwidths are: 1.4, 3, 5, 10, 15 and 20 MHz
� Note that in LA1.1, only 5, 10 MHz are implemented
5 MHz 10 MHz
… …
15 kHz Sub-carrier
� The symbol duration is always the same whatever the bandwidth
� There are 2 times more sub-carriers in 10 MHz than in 5 MHz
� 2 times more symbols can be sent or received at the same time.
� The capacity is multiplied by 2
Reduced subcarrier spacing of 7.5 KHz for MBSFN operation also supported
• Center subcarrier (DC subcarrier) not used to allow for direct conversion receiver implementation
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 38
5 OFDMA and LTE
5.1 OFDMA Parameter for LTE [cont.]
1200 (1201)900 (901)600 (601)300 (301)180 (181)72 (73)Number of useful sub-carriers
204815361024512256128Number of sub-carriersFFT size
30.72 MHz(8 × 3.84)
23.04 MHz(6 × 3.84)
15.36 MHz(4 × 3.84)
7.68 MHz(2 × 3.84)3.84 MHz
1.92 MHz(1/2 × 3.84)
Sampling frequency
15 kHz Sub-carrier spacing
20 MHz15 MHz10 MHz5 MHz3 MHz1.4 MHzSpectrum allocation
5 MHz7.68 MHz
� For the 5 MHz, there are 512 sub-carriers of 15 kHz. The total band is 7.68 MHz. It is larger than the 5 MHz band!
� But only 301 sub-carriers are used (Pilot, DC, data), the other ones are guard sub-carriers:
� 301 Sub-ca * 15 kHz = 4.515 MHz
Used bandwidth
Flexible bandwidth allocation supported by OFDM
• Still different RF filter will be required
• Frame structure always the same
• Sampling frequency is an transmitter and receiver implementation issue
• Sampling rate is multiple of 3.84 MHz Ł single clock for multi-mode UE with WCDMA
• Smallest bandwidth that is supported was modified recently and needs to be updated
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 39
5 OFDMA and LTE
5.1 OFDMA Parameter for LTE [cont.]
�The symbol duration depends on the sub-carrier width.
� 2 Cyclic Prefixes are defined by the 3GPP:
� Long CP: 16.67 micro seconds
� Normal CP: 4.69 micro seconds
� Only the normal CP is supported in LA1.x
� The total duration of a symbol is:
� Useful duration + CP = 66.6 + 4.69
� Total duration = 71.29 µs � With normal CP
#4#3#2#1
User 1
User 1
User 1
User 2
User 2
User 2
User 2
User 3
User 3
User 3User 4User 4
Time
skHzthCarrierWidSub
olDurationUsefulSymb µ6.6615
11 ==−
=
Exercise
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 40
Exercise 1
� Let‘s assume the following 2 radio conditions:
� Case 1: Radio conditions -> 16 QAM and coding rate ½
� Case 2: Radio Conditions -> QPSK and coding rate 2/3
� How many symbols are required to transmit 100 bits when radioconditions are similar to:
� case 1?
� case 2?
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 41
Exercise 2
� What is the maximum bit rate of a sub-carrier?
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 42
Module Summary
� The link adaption is done by the selection on the most suitable MCS (Modulation Coding Scheme) using the QPSK, the 16-QAM and the 64-QAM modulation
� The OFDMA uses multiple Sub-carriers into the bandwidth to send several symbol on the same time and to reach several users
� The width of a sub-carrier, the number of sub-carrier, the bandwidth and the symbol duration are fixed by the 3GPP
� To fix the ISI issue, a guard time called Cyclic prefix, is added on each symbol
� The SC-FDMA is used in UL like it is more efficient than the OFDMA in the point of view of the limited power capacity of the UE
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9400 LTE RAN Radio Principles DescriptionOFDMA Principles
2 � 43
End of ModuleOFDMA Principles
Page 1
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Do not delete this graphic elements in here:
3All Rights Reserved © Alcatel-Lucent 2009
Module 3Air Interface Structure
9400 LTE RAN Radio PrinciplesDescription
TMO18214 D0 SG DEN Issue 4
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
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First editionLast name, first nameYYYY-MM-DD01
RemarksAuthorDateEdition
Document History
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 3
Module Objectives
Upon completion of this module, you should be able to:
� Describe the structure of an LTE radio frame
� List the radio protocols and their functions
� Describe the channels architecture of the air interface
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3 � 4
Module Objectives [cont.]
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 5
Table of Contents
Switch to notes view!Page
1 Radio Frame Structure 71.1 Basic Frame Structure 81.2 Resource Block 101.3 Resource Element Group 11
2 Protocol Stack 122.1 Radio Interface Overview 132.2 Terminology 152.3 RRC 162.4 PDCP 192.5 RLC 212.6 MAC 22
3 Radio Channels 263.1 Channel Architecture 273.2 Logical Channel 293.3 Transport Channel 313.4 From the Transport to the Physical Channel 353.5 Physical Channel 37
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Table of Contents [cont.]
Switch to notes view!
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 7
1 Radio Frame Structure
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3 � 8
1 Radio Frame Structure
1.1 Basic Frame Structure
� In FDD, the DL and UL Radio Frames (RFs) are not on the same carrier.
� The RF frame is called Type 1 by the 3GPP.
� The RF length is 10 ms.
RF #3RF #2RF #1 ……
DL Carrier
UL Carrier
� The radio frame is made up of 10 sub-frames of 1 ms.
� Each sub-frame is made up of 2 slots of 0.5ms.
RF #1
10 sub-frames
2 slots
RF #3RF #2RF #1
#9#8#7#6#5#4#3#2#1#0
#2#1
For FDD, 10 subframes are available for downlink transmission and 10 subframes are available for uplink
transmissions in each 10 ms interval. Uplink and downlink transmissions are separated in the frequency
domain.
A Frame structure type 2 is also defined and is applicable to TDD
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3 � 9
1 Radio Frame Structure
1.1 Basic Frame Structure [cont.]
� Each slot is made up of:
� 7 symbols in case of normal CP (guard time between symbols)
#9#8#7#6#5#4#3#2#1#0
RF #1
10 sub-frames
Tu= 66.7µs
Tu = Useful Symbol DurationTcp = Cyclic Prefix durationTecp = Extended Cyclic Prefix duration
#7
Tcp = 4.7 µs
#6#5#4#3#2#1
#6#5#4#3#2#1
Tecp = 16.7 µs
#2#1
Since OFDM offers a better flexibility in terms of sub-frame structure and pilot allocation, there is no reason
to consider the same structure as for DFT-SOFDM.
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 10
DwPTS GuardPeriod
UpPTS
1 Radio Frame Structure
1.1 Basic Frame Structure [cont.]
� The frame structure for the type 2 frames used on LTE TDD is somewhat different.
� The 10 ms frame comprises two half frames, each 5 ms long.
� The LTE half-frames are further split into five sub frames, each 1ms long.
Frame N-1 Frame N+1Frame N
SF0 SF8SF2 SF7SF5 SF9SF3 SF4
10 ms 10 ms10 ms
1ms 1ms
Half Frame Half Frame
1ms DwPTS Guard
PeriodUpPTS
The subframes may be divided into standard subframes of special subframes.
The special subframes consist of three fields:
� DwPTS - Downlink Pilot Time Slot
� GP - Guard Period
� UpPTS - Uplink Pilot Time Stot.
These three fields are also used within TD-SCDMA and they have been carried over into LTE TDD (TD-LTE)
and thereby help the upgrade path. The fields are individually configurable in terms of length, although the
total length of all three together must be 1ms.
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 11
1 Type 2 LTE Frame Structure
1.4 LTE TDD Subframe Allocations
� One of the advantages of using LTE TDD is that it is possible to dynamically change the up and downlink balance and characteristics to meet the load conditions.
� In order that this can be achieved in an ordered fashion, a total of seven up / downlink configurations have been set within the LTE standards, in order to make possible
D/ U is a subframe for downlink/ Uplink transmission and S is a "special" subframe used for a guard time.
D
D
D
D
D
D
U
9
U
D
D
D
D
U
U
8
U
D
D
D
U
U
U
7
S
D
D
D
S
S
S
6
D
D
D
D
D
D
D
5
U
D
D
U
D
D
U
4
U
D
U
U
D
U
U
3
U
U
U
U
U
U
U
2
S
S
S
S
S
S
S
1
D
D
D
D
D
D
D
0
SUBFRAME NUMBER
5 ms
10 ms
10 ms
10 ms
5 ms
5 ms
5 ms
Down to Up link Switch periodicity
5
3
1
6
4
2
0
Up/ Down
Link Config
� In the case of the 5ms switch point periodicity, a special subframe exists in both half frames.
� In the case of the 10 ms periodicity, the special subframe exists in the first half frame only.
� It can be seen from the table below that the subframes 0 and 5 as well as DwPTS are always reserved for
the downlink.
� It can also be seen that UpPTS and the subframe immediately following the special subframe are always
reserved for the uplink transmission.
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 12
One downlink slot, Tslot
subc
arri
ers
NB
WDL
Resource element
OFDM symbolsOFDM symbols
NB
Wsu
bcar
rier
sR
B
Resource block
RBBW
DLsymb NN ×
resource elements
RBBW
DLsymb NN ×
resource elements
1 Radio Frame Structure
1.2 Resource Block
4324
86Extended cyclic prefix
9712
Normal cyclic prefix
Frame structure type 2
Frame structure type 1
ConfigurationRBBWN
DLsymbN
kHz 15=∆f
kHz 15=∆f
kHz 5.7=∆f
Note*: This system bandwidth is used only for FDD migrationNote**: This system bandwidth is used only for TDD migration
100755025[15] or [16]
76Number of resource
blocks
2015105[3] or [3.2]
1.6**1.4*Operating system bandwidth [MHz]
Multiplex multiple users both in time and frequency, together with pilots and control signals.
The time-frequency plane is divided into chunks=minimum resource allocation unit.
The traffic multiplexing is performed by allocating to each user a certain number of chunks depending on its
data rate/geometry.
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 13
1 Radio Frame Structure
1.3 Physical Resource Block
PRB is the minimum unit of allocation in LTE
2 Slots (14 symbols)= 1 ms
Physical Resource Block (PRB) = 14 OFDM symbols(2 slots) x 12 Subcarrier
In OFDMA, users are allocated a specific number of subcarriers for a predetermined amount of time. These are
referred to as physical resource blocks (PRBs) in the LTE specifications. PRBs thus have both a time and
frequency dimension. Allocation of PRBs is handled by a scheduling function at the 3GPP base station
(eNodeB).
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 14
1 Radio Frame Structure
1.4 Resource Element Group
�For the control channel, the radio signaling, the Resource Block is not the adapted unit.
�The control channels mapped on the Resource Elements Groups (REGs), which represent less radio resources
�A REG is made up of 4 (or 6 if there are pilot sub-carriers) sub-carriers during 1 symbol.
� The REG are grouped into the CCE (Control Channel Element) Sub-carriers
Symbols1 REG
#12
#11
#10
#9
#8
#7
#6
#5
#4
#3
#2
#1
Exercise
Resource element groups are sued for defining the mapping of control channels to resource elements.
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 15
2 Protocol Stack
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 16
2 Protocol Stack
2.1 Radio Protocol Stack Overview
eNB
PHY
UE
PHY
MAC
RLC
MAC
MME
RLC
NAS NAS
RRC RRC
PDCP PDCP
User & Control Plane
Control Plane Only
In the C-plane, the NAS functional block is used for network attachment, authentication, setting up bearers,
and mobility management. All NAS messages are ciphered and integrity protected by the MMEand UE.
The radio resource control (RRC) layer in the eNB makes handover decisions based on neighbor cell
measurements reported by the UE, performs paging of the users over the air interface, broadcasts system
information, controls UE measurement and reporting functions such as the periodicity of channel quality
indicator (CQI) reports and further allocates cell-level temporary identifiers to active users. It also executes
transfer of UE context from the serving eNB to the target eNB during handover and performs integrity
protection of RRC messages. The RRC layer is responsible for setting up and maintenance of radio bearers.
In the U-plane, the Packet Data Convergence Protocol (PDCP) layer is responsible for compressing or
decompressing the headers of user-plane IP packets using robust header compression (RoHC) to enable
efficient use of air interface resources . The radio link control (RLC) layer is used to format and transport
traffic between the UE and the eNB .
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3 � 17
2 Protocol Stack
2.1 Radio Protocol Stack Overview
eNode-B
Control PlaneUser Plane Control PlaneUser Plane
Logical Channel
Radio Bearer
Transport Channel
Physical Channel
Non-Access StratumSignaling between Core Network and UE
Radio Signaling
PDCP
Physical Layer
MAC Layer
RLC
RRC
NAS
PDCP
Physical Layer
MAC Layer
RLC
RRC
NAS
Layer 2 is split into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC) and
Packet Data Convergence Protocol (PDCP)
Segm.ARQ etc
Multiplexing UE1
Segm.ARQ etc
...
HARQ
Multiplexing UEn
HARQ
BCCH PCCH
Scheduling / Priority Handling
Logical Channels
Transport Channels
MAC
RLC Segm.ARQ etc
Segm.ARQ etc
PDCPROHC ROHC ROHC ROHC
Radio Bearers
Security Security Security Security
...CCCH
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3 � 18
2 Protocol Stack
2.2 Terminology
� PDU = Protocol Data Unit
� SDU = Service Data Unit
Layer N Layer N
Layer N+1
Layer N receives an SDU from Layer N+1
2 protocols of the same layer exchange PDU
SDU (layer N+1)Header Layer N
PDU (Layer N)
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3 � 19
2 Protocol Stack
2.3 RRC
Higher layers
� The Radio Resource Connection (RRC) protocol is implemented in the eNodeB and the UE. In WCDMA, it is implemented in the RNC!
� RRC is the highest protocol in the control plane on the radio side. The RRC protocol allows:
� 2 instances (eNodeB and UE) to exchange signaling messages.
� to forward signaling messages coming from the core network, called NAS signaling.
RRC
RRC
eNode-B
ePC
Radio signaling
NAS signaling
Broadcast of system information related to non-access stratum (NAS),
- Broadcast of system information related to access stratum (AS),
- Paging,
- Establishment, maintenance and release of an RRC connection between the UE and the e-UTRAN including:
� Allocation of temporary identifiers between UE and e-UTRAN,
� Configuration of signalling radio bearer(s) for RRC connection:
� Low priority SRB and high priority SRB,
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3 � 20
2 Protocol Stack
2.3 RRC [cont.]
Establishment, maintenance and release of an RRC connection between the UE and E-UTRAN
NAS direct message transfer to/from NAS from/to UE
Broadcast of System Information
UE measurement reporting and control of the reporting
Mobility Management
Paging
RRC Functions
The establishment and maintenance of the RRC connection includes:
� Allocation of temporary identifiers between UE and E-UTRAN.
� Configuration of signaling radio bearer(s) for RRC connection.
� Low priority SRB and high priority SRB.
� Security functions including key management.
� Establishment, configuration, maintenance and release of point to point Radio Bearers
The Mobility management functions includes:
� UE measurement reporting and control of the reporting for inter-cell and inter-RAT mobility.
� Handover.
� UE cell selection and reselection and control of cell selection and reselection.
� Context transfer at handover.
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2 Protocol Stack
2.3 RRC [cont.]
� RRC uses the following states:
RRC_Idle:•The UE is not connected. There is no radio link. •The network knows that the UE is present on the network and is able to reach it in case of incoming call.•The UE switches in idle mode when it isconnected and there is no traffic to save radio resources and its battery.
RRC_Idle:•The UE is not connected. There is no radio link. •The network knows that the UE is present on the network and is able to reach it in case of incoming call.•The UE switches in idle mode when it isconnected and there is no traffic to save radio resources and its battery.
RRC_Connected•The UE has an e-UTRAN-RRC connection.•The network can transmit/receive data to/from the UE and knows its location at the cell level.•The network manages the mobility with handover.
RRC_Connected•The UE has an e-UTRAN-RRC connection.•The network can transmit/receive data to/from the UE and knows its location at the cell level.•The network manages the mobility with handover.
The LTE UE could have one of the two following states:
� RRC Connected, when it has a RRC connection with a given eNB
� RRC IDLE when it has no valid RRC link with any eNB.
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2 Protocol Stack
2.4 PDCP
� The main services provided by the Packet Data Convergence Protocol (PDCP) are:
PDCP
Physical Layer
MAC Layer
RLC
RRC
NAS
User Plane Control Plane� For the user plane:
� IP header compression and decompression with the Robust Header Compression (ROHC) method only
� Ciphering
� Transfer of user data
� In-sequence delivery of upper layer PDUs at HO in the uplink
� For the control plane:
� Ciphering and Integrity Protection to secure the transmission of core network signaling
� The main services and functions of the PDCP sublayer for the user plane include:
� Header compression and decompression: ROHC only;
� Transfer of user data;
� In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM;
� Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM;
� Retransmission of PDCP SDUs at handover for RLC AM;
� Ciphering and deciphering;
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3 � 23
2 Protocol Stack
2.4 PDCP [cont.]
� The header of an IP packet is 20 octets.
� For example, during an FTP transfer, a lot of IP packets are sent over the air interface and the IP headers are almost always the same. They represent a significant amount of data which can be reduced thanks to a compression method.
� The PDCP header is 1 (or 2) octet.
� The Robust Header Compression (ROHC) is a standardized method used to compress IP, UDP, TCP and RTP headers.
� RFC 4995
Payload (http, ftp, rtp for voice …) Header
- Length- Destination IP address- Source IP address- TTL
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3 � 24
2 Protocol Stack
2.5 RLC
� The Radio Link Control (RLC) protocol provides the following services:
PDCP
Physical Layer
MAC Layer
RLC
RRC
NAS
User Plane Control Plane� Segmentation of SDU according to the size
� Re-Segmentation of PDU
� Radio Bearer to logical channel mapping
� Transfer of data in 3 modes:
� TM Transparent Mode
Without retransmission. For real-time service.
� UM Unacknowledged Mode
Without retransmission, but error statistics (BLER)
It can be used for the signaling.
� AM Acknowledged Mode
With retransmission. For non real-time services, like internet.
� The main services and functions of the RLC sublayer include:
� Transfer of upper layer PDUs;
� Error Correction through ARQ (only for AM data transfer);
� Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer);
� Re-segmentation of RLC data PDUs (only for AM data transfer);
� In sequence delivery of upper layer PDUs (only for UM and AM data transfer);
� Protocol error detection and recovery;
� RLC SDU discard (only for UM and AM data transfer);
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2 Protocol Stack
2.6 MAC
� The MAC protocol provides the following services:
PDCP
Physical Layer
MAC Layer
RLC
RRC
NAS
User Plane Control Plane� Logical Channel to Transport channel mapping
� Scheduling:
There is no dedicated channel allocated to a UE. Time and frequency resources are dynamically shared between the users in DL and UL.
The scheduler is part of the MAC layer and controls the assignment of uplink and downlink resources.
� Multiplexing/Demultiplexing of RLC PDU
� The main services and functions of the MAC sublayer include:
� Mapping between logical channels and transport channels;
� Multiplexing/demultiplexing of MAC SDUs belonging to one or different logical channels into/from
transport blocks (TB) delivered to/from the physical layer on transport channels;
� scheduling information reporting;
� Error correction through HARQ;
� Priority handling between logical channels of one UE;
� Priority handling between UEs by means of dynamic scheduling;
� Transport format selection;
� Padding.
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3 � 26
2 Protocol Stack
2.6 MAC [cont.]
eNodeB
DL
UL
Frequency
Time
� The scheduler (in the eNodeB) determines dynamically, each 1 ms, which UEs are supposed to receive data on the DL shared channel and on the UL shared channel and on what resources.
� The basic time-frequency unit is the resource block.
� To select the adapted modulation and coding rate, the scheduler needs measurement reports in DL and UL.
The eNodeB allocates physical layer resources for the uplink and downlink shared channels (UL-SCH and DL-
SCH).
Resources are composed of Physical Resource Blocks (PRB) and Modulation Coding Scheme (MCS). The MCS
determines the bit rate, and thus the capacity, of PRBs.
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2 Protocol Stack
2.6 MAC [cont.]
eNode-B
eNodeB
Scheduler
Buffer
Data
Multiplexing
Modulation, Coding
Transmission
eNodeB
UE
DL channel quality measurement
� In downlink, the scheduler needs the following inputs to schedule data:
� Amount of data
� Nature of the data
� Radio resource available
� Radio Condition in DL
� The UE reports regularly its measurement report, called Channel Quality Indicator (CQI).
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 28
UE
2 Protocol Stack
2.6 MAC [cont.]
eNode-B
eNodeB
Scheduler
Buffer
Data
Multiplexing
Modulation, Coding
Transmission
eNodeB
UL channel quality measurement
� In uplink, the mechanism is similar but:
� Measurements are made by the eNodeB
� The eNodeB scheduler controls the UE transmission
Request to transmit
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
3 � 29
3 Radio Channels
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3 � 30
Radio Bearer
Logical Channel
Transport Channel
Physical Channel
3 Radio Channels
3.1 Channel Architecture
PDCP
Physical Layer
MAC Layer
RLC
PDCP
Physical Layer
MAC Layer
RLC
eNode-B
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3 � 31
3 Radio Channels
3.1 Channel Architecture [cont.]
� A Logical Channel is defined by the type of information it carries. Logical channels are classified into control and traffic channels.
� Answer to the question: what is it being transported?
� A Transport Channel is defined by how and with what characteristics the information is transmitted.
� Answer to the question: how is it being transported?
� A Physical Channel is defined by the physical resources used to transmit the data. At the physical level, a distinction can be made between:
� The physical channel on which are mapped transport channels.
� The physical signal, which does not carry information but is used for synchronization or measurement.
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3 Radio Channels
3.2 Logical Channel
� The following control logical channels have been defined by the 3GPP:
� BCCH, Broadcast Control Channel, used for the transmission of system control information. A UE needs to decode it before requesting a connection.
� PCCH, Paging Control Channel, is a downlink channel that transfers paging information and system information change notifications. This channel is used for paging when the network does not know the location cell of the UE.
� CCCH, Common Control Channel is a channel for transmitting control information between UEs and network. This channel is used for UEs having no RRC connection with the network.
� DCCH, Dedicated Control Channel is a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. Used by UEshaving an RRC connection.
� MCCH, Multicast Control Channel is a point-to-multipoint downlink channel used for transmitting MBMS control information from the network to the UE, for one or several MTCHs. This channel is only used by UEs that receive MBMS.
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3 Radio Channels
3.2 Logical Channel [cont.]
� The following traffic logical channels have been defined by the 3GPP:
� DTCH, Dedicated Traffic Channel, is a point-to-point channel, dedicated to one UE, for the transfer of user information. A DTCH can exist both in uplink and downlink.
� MTCH, Multicast Traffic Channel is a point-to-multipoint downlink channel for transmitting traffic data from the network to the UE. This channel is only used by UEs that receive MBMS.
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3 Radio Channels
3.3 Transport Channel
� A transport channel defines how and with what characteristics the information is transmitted.
� Inherited from the WCDMA, data on the transport channel is organized into “Transport Blocks”, TBs.
� A Transport block can be transmitted every TTI = 1 ms
� The “Transport Format”, TF, defines how the blocks can be transmitted:
� Transport block size, it depends on the MCS and the number of PRB allocated
� Allowed modulation scheme
� Antenna mapping
Transport Block
TTI = 1 ms
Transport Block
Note: In case of multi-antenna system, there can be 2 TBs for each TTI.
Each TTI, the scheduler decides which chunk to allocate to which user. The chunks are not standardized.
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3 Radio Channels
3.3 Transport Channel [cont.]
� The following transport channels in DL have been defined by the 3GPP:
� Broadcast Channel (BCH) characterized by a fixed, pre-defined transport format with a robust modulation to be broadcast in the entire coverage area of the cell.
� Downlink Shared Channel (DL-SCH) characterized by:� a dynamic link adaptation by varying the modulation, coding and transmit power
� support for H-ARQ (radio retransmission).
� Paging Channel (PCH) characterized by:� Requirement to be broadcast in the entire cell.
� Multicast Channel (MCH) characterized by:� requirement to be broadcast in the entire coverage area of the cell
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9400 LTE RAN Radio Principles DescriptionAir Interface Structure
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3 Radio Channels
3.3 Transport Channel [cont.]
� The following transport channels in UL have been defined by the 3GPP:
� Uplink Shared Channel (UL-SCH) characterized by:� support for dynamic link adaptation by varying the transmit power and potentially modulation and coding
� support for H-ARQ
� support for both dynamic and semi-static resource allocation.
� Random Access Channel (RACH) characterized by:� limited control information
� collision risk
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3 � 37
MAC Layer
3 Radio Channels
3.3 Transport Channel [cont.]
BCCHPCCH CCCH MCCHDCCH DTCH MTCH
BCHPCH DL-SCH MCHUL-SCH
Transport Channel
Logical Channel
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3 Radio Channels
3.4 From the Transport to the Physical Channel
� Transport channels are then mapped on the physical channels which are sent over the air interface
� A CRC is calculated and appended to each TB. It allows the receiver to detect errors. It is used by retransmission mechanisms like H-ARQ
� Depending on the Transport Format and the radio quality, the TB is coded and interleaved.
� The H-ARQ is a process running in the UE and in the eNodeB to allow a fast retransmission in case of errors.
� The resulting bit sequence is modulated and mapped on the sub-carriers of the Resource Block used for the transmission (one or several RBs).
100 bits Transport Block
Physical Layer
Add CRC
TB CRC
Coding, Interleaving
TB CRC Parity bits
H-ARQ If activated
Data Modulation
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3 � 39
3 Radio Channels
3.4 From the Transport to the Physical Channel [cont.]
� The data are modulated and mapped on the sub-carriers.
� The basic time-frequency unit is the Resource Block.7 symbols
12 sub-carriersData Modulation
11111111111111111111111
16 QAM Modulation -> 4 bits per symbol48 bits can be sent with the 1st symbol of the RB
1111
1111
1111
1111
1111
1111
1111
1111
1111
1111
1111
1111
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3 Radio Channels
3.5 Physical Channel
� A distinction has to made between:� The physical channel
� The physical signal
� Carries information originating from the upper layer
Physical channel
PDCP
Physical Layer
MAC Layer
RLC
Data or signaling
� Does not carry information from the upper layer
� Used for synchronization or measurement
Physical signal
eNode-B
PHY
PHY
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3 Radio Channels
3.5 Physical Channel [cont.]
� The DL physical channels are:
� Physical DL Shared Channel (PDSCH)� It is a shared channel used to carry user data, radio & core network, system information (BCH), paging message.
� Physical DL Control Channel (PDCCH)� It is a shared signaling channel to carry the allocation of the resources (PDSCH).
� Physical Broadcast Channel (PBCH)� It is the channel used to broadcast the system information.
� The UL physical channels are:
� Physical Random Access Channel (PRACH)� It is a shared channel used for the access procedure.
� Physical UL Shared Channel (PUSCH)� It is a shared channel used to carry user data, radio & core network,
� Physical UL Control Channel (PUCCH)� It is a shared signaling channel in uplink to allow the UE to request resources on the PUSCH.
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3 Radio Channels
3.5 Physical Channel [cont.]
PHY Layer
UL-SCHDL-SCH BCH RACH MCH
PDCCH
PDSCH PUSCH
PUCCH
PBCH
Physical Channel
Transport Channel
PMCHPRACH
PCH
Physical control channel in DL and UL
Exercise
BCCHPCCH CCCH MCCHDCCH DTCH MTCH
Logical Channel
MAC Layer
PCFICH
PHICH
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3 � 43
Exercise 1
� The aim is to calculate the max theoretical raw bit of a cell.
� This max bit rate is only theoretical and can not be reached on a real network
� Assumptions:
� MIMO 4×4
� That means that are 4 antennas on the eNodeB and 4 antennas on the UE. The eNodeB can transmit 4 independent streams on the same time to the UE.
� Bandwidth: 20 MHz
� The overhead per Resource Block is:
� 6 Resource Elements due to the PDCCH (physical DL control channel)
� 10 Resources Elements due to the Reference signal (for measurements)
� Best Modulation: 64 QAM
� Follow the method on the next slides to calculate the max raw bit rate
30 minutes
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Exercise 1
� Step 1: Calculate the number of useful Resource Element in a Resource Block
� Step 2: Calculate the number of Resource Block
� Step 3: Calculate the number of useful Resource Element in the sub-frame
� Step 4: Calculate the max number of bit in the sub frame
� Step 5: Calculate the raw bit rate for 1 antenna
� Step 6: Calculate the max bit rate for MIMO 4×4
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Exercise 2
� Match each of the entities listed below to its appropriate location on the diagram (see next page).
� MAC header
� RLC SDU
� CRC
� RLC header
� Transport Block
� PDCP header
� MAC SDU
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Exercise 2
Voice sampleRTPUDPIP HTTPTCPIP
PDCP header compression
Voice sampleheaders HTTPheaders
Voice sampleheaders HTTPheaders1 1
RLC Segmentation, Concatenation
2 2
3 3
MAC Multiplexing 54
6 7PHY
1
2
3
4
5
6
7
MAC headerRLC SDUCRCRLC headerTransport BlockPDCP headerMAC SDU
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Module Summary
� The duration of type 1 radio frame is 10 ms. It is made of 10 sub-frame (1 ms)
� A sub-frame is made 2 slots
� A slot is made of 7 symbols
� A Resource Block is made of 12 sub-carriers and 7 symbol (a slot)
� A Resource Element is a 1 Sub-carrier/1 Symbol
� The RRC protocol is the head of the air interface
� The DL and UL scheduler are running in the MAC layer in the eNodeB
� The Radio Bearer is mapped on Logical channel -> Transport Channel -> Physical Channel
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End of ModuleAir Interface Structure
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Do not delete this graphic elements in here:
4All Rights Reserved © Alcatel-Lucent 2009
Module 4eUTRAN Scenarios
9400 LTE RAN Radio PrinciplesDescription
TMO18214 D0 SG DEN Issue 4
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Blank Page
This page is left blank intentionally
First editionLast name, first nameYYYY-MM-DD01
RemarksAuthorDateEdition
Document History
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Module Objectives
Upon completion of this module, you should be able to:
� Describe the steps and the resources used by a UE to request a connection
� Describe the different traffic operations, i.e. what are the different mechanisms to allow a traffic with a UE
� Describe the bearer establishment scenario
� Describe the measurement report mechanisms
� Describe the radio retransmission mechanisms
� Describe the resources allocation
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Module Objectives [cont.]
This page is left blank intentionally
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Table of Contents
Switch to notes view!Page
1 RRC Connection Scenarios 71.1 Overview 81.2 Synchronization 121.2 Synchronization & BCH for TDD Frame 171.3 Obtain Cell Parameters 181.4 Random Access Procedure 201.5 RRC Connection Establishment 241.6 Attach Setup 25
2 Bearer Management 262.1 EPS Bearer 272.1 EPS Bearer [CONT] 282.2 QoS Parameters 292.2 QoS Parameters [CONT] 302.3 Radio Bearer 31
3 Traffic Operation 353.1 Traffic Operation Overview 363.2 Data Transmission in DL 433.3 Data Transmission in UL 473.4 DCI 513.5 Measurement Report 533.6 Radio Retransmission 573.6.1 H-ARQ Mechanism in DL 59
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Table of Contents [cont.]
Switch to notes view!Page
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1 RRC Connection Scenarios
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1 RRC Connection Scenarios
1.1 Overview
eNodeB MME Gateway
ePC
Synchronization
Obtain DL Parameters
RRC Connection
Initial Network Attach
� When the UE is powered up, it has to be RRC connected to be able to exchange data and signaling with the network.
� After the RRC connection, the Initial network attach allows to establish all the bearers to carry the data from the UE to the gateway.
Scanning
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1 RRC Connection Scenarios
1.1 Overview [cont.]
� After the RRC connection, Signaling Radio Bearers (SRBs) are established.
� An SRB is a Radio Bearer that only carries the signaling:
� SRB1 carries the RRC signaling.
� SBR2 carries the NAS signaling, i.e. between the Core Network and the UE.
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1 RRC Connection Scenarios
1.1 Overview [cont.]
� During the Initial Attach:
� An MME is selected.
� The UE is authenticated.
� An IP address is allocated to the UE.
� S-GW and P-GW are selected.
� Bearers are established on the S1-U, S5/S8 and on the air interface.
� The RRC connection is reconfigured to allow user data traffic.
� At the end of the Initial Attach, the UE is able to reach external networks.
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1 RRC Connection Scenarios
1.1 Overview [cont.]
� The RRC Connection is basically made up of 2 steps:
� Contention Based Random Access.
� Exchange of Signaling to establish the connection.
� When a UE requests a connection, it has no dedicated resources to reach the eNodeB. It uses an uplink common channel which is able to manage the collision between 2 UEs requesting an access at the same time.
eNodeB
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1 RRC Connection Scenarios
1.2 Synchronization
� After the power on, the UE knows:
� the UE category and capability.
� the preferred PLMN.
� the carriers.
� The UE needs to know:
� The frame synchronization to be able to decode the DL radio frame.
� The cell parameters to be able request a connection.
� The UE can use:
� The PSS: Primary Synchronization Signal.
� The SSS: Secondary Synchronization Signal.
� The BCH, the broadcast channel.
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1 RRC Connection Scenarios
1.2 Synchronization [cont.]
� The synchronization signals provide the cell id to the UE.
� LTE supports 510 different cell identities.
� They are divided into 170 cell id groups and there are 3 cell ids per group.
� Cell id = 3* Cell_Group_id + Cell_id_in_group
0 to 169Provided by the SSS
0 to 2Provided by the PSS
0 1
2
Cell Group #23
Cellid #69 Cellid #70
Cellid #71
0 1
2
Cell Group #100
Cellid #300 Cellid #301
Cellid #302
P-SCH & s-SCH location:
over the 62 central frequencies of the spectrum (regarless of the system bandwidth)
In the fifth and sixth symbol position of slot 0 of subframes 0 & 5
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1 RRC Connection Scenarios
1.2 Synchronization [cont.]
� The Primary Synchronization Signal (PSS):
� is used for the slot synchronization.
� is on the last OFDM symbol of slots 0 & 10 in the 1st & 6th sub-frames of each frame.
� carries one of the 3 cell id in group sequence.
Frame
TS0
SF1
TS1 TS2 TS3
SF0 SF5 SF9
TS10 TS11 TS18 TS19
10ms
1ms
0.5ms
Sb0 Sb1 Sb2Sb
NDL-2
Sb
NDL-1
…….. ……..
…….. ……..
Sb0 Sb1 Sb2Sb
NDL-2
Sb
NDL-1
0.5ms
PSS PSS
P-SCH decoding
P-SCH sequence is encoded according to one of 3 possible CAZAC sequences (identical in subframe 0 & 5)
The UE performs correlation of the known sequence with the received samples over half a frame and keeps the highest
correlation
slot boundary is known and subframe known modulo 5 subframes
Nid2 = 0..2 is retrieved from p-SCH decoded sequence
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1 RRC Connection Scenarios
1.2 Synchronization [cont.]
� The Secondary Synchronization Signal (SSS):
� is used for the frame synchronization.
� is on the same slot as PSS.
� is on the next to last OFDM symbol of slots 0 & 10 in the 1st & 6th sub-frames of each frame.
� carries one of the 170 unique cell group identifiers.
Frame
TS0
SF1
TS1 TS2 TS3
SF0 SF5 SF9
TS10 TS11 TS18 TS19
10ms
1ms
0.5ms
Sb0 Sb1 Sb2SbNDL-2
SbNDL-1
…….. ……..
…….. ……..
Sb0 Sb1 Sb2SbNDL-2
SbNDL-1
0.5ms
Frame
TS0
SF1
TS1 TS2 TS3
SF0 SF5 SF9
TS10 TS11 TS18 TS19
Sb0 Sb1 Sb2SbNDL-2
SbNDL-1
…….. ……..
…….. ……..
Sb0 Sb1 Sb2SbNDL-2
SbNDL-1
SSS SSS SSS SSS
S-SCH decoding
S-SCH sequence is encoded according to one of 168 possible sequences (differing in subframes 0 & 5)
The UE performs correlation of the known sequence with the two possible locations and keeps the highest correlation
Frame boundaries are known
Nid1 = 0..167 is retrieved from s-SCH decoded sequence
Ncellid is derived from these previous computation
Ncellid=3*Nid1+Nid2
Ncellid used as input for all channels encoding
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1.2 Synchronization [cont.]
� The PSS, the SSS and the BCH are carried over 6 Resource Blocks (RB) whatever the bandwidth
� 6 RBs = 6 * 12 Sub-ca = 72 Sub-carriers
6 central RBs
� By this way, these signals are independent from the bandwidth and can decode this signal without knowing it.
Bandwidth: from 1.4 to 20 Mhz
P-SCH & s-SCH location:
over the 62 central frequencies of the spectrum (regarless of the system bandwidth)
In the fifth and sixth symbol position of slot 0 of subframes 0 & 5
pBCH location:
over the 72 central frequencies of the spectrum (regarless of the system bandwidth)
In the first four symbol positions of slot 1 of subframes 0 not used by RS signal
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1.2 Synchronization & BCH for TDD Frame
� The Primary synchronization signal (PSS): is placed at the third symbol in subframes#1 and #6.
� The secondary synchronization signal (SSS): is placed at the last symbol in subframes#0 and #5.
� The S-RACH is transmitted on the UpPTS within the special frame.
� The Primary Broadcast Channel (P-BCH) and the Dynamic Broadcast Channel (D-BCH): are located as in LTE FDD.
SF0 SF8SF2 SF7SF5 SF9SF3 SF4
SSS
SSS
PSS
PSS
S-RACH/SRS
RACH
S-RACH/SRS
RACHPBCH
DBCH
Mapping of critical control channels to TDD configuration #1
Random access typically uses one of the normal subframes as in FDD, allowing for a relatively long
random-access preamble providing coverage and capacity also in large cells. However, in scenarios
where random-access coverage is not an issue, a short random access preamble in the UpPTS can be
used instead.
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1 RRC Connection Scenarios
1.3 Obtain Cell Parameters
� To provide the most critical information to the UEs, the eNodeB uses the BCH channel
� The information is sent on pre-defined time-frequency resources
� This information is organized into different information blocks:� The MIB, the Master Information Block.
� System Frame Number
� DL System Bandwidth
� Number of Transmit Antennas at eNodeB
� Periodicity: 4 RFs
� SIB1� How other SIBs are scheduled and cell accessibility
� Periodicity: 8 RFs
� SIB2: Access Info
� SIB3: Serving Cell info for Cell reselection
� SIB4: Intra-frequency neighbors
� SIB5: Other e-UTRA frequency
� SIB6: UTRA frequency
� MasterInformationBlock defines the most essential physical layer information of the cell required to
receive further system information;
� SystemInformationBlockType1 contains information relevant when evaluating if a UE is allowed to access
a cell and defines the scheduling of other system information blocks;
� SystemInformationBlockType2 contains common and shared channel information;
� SystemInformationBlockType3 contains cell re-selection information, mainly related to the serving cell;
� SystemInformationBlockType4 contains information about the serving frequency and intra-frequency
neighbouring cells relevant for cell re-selection (including cell re-selection parameters common for a
frequency as well as cell specific re-selection parameters);
� SystemInformationBlockType5 contains information about other E-UTRA frequencies and inter-frequency
neighbouring cells relevant for cell re-selection (including cell re-selection parameters common for a
frequency as well as cell specific re-selection parameters);
� SystemInformationBlockType6 contains information about UTRA frequencies and UTRA neighbouring cells
relevant for cell re-selection (including cell re-selection parameters common for a frequency as well as
cell specific re-selection parameters);
� SystemInformationBlockType7 contains information about GERAN frequencies relevant for cell re-selection
(including cell re-selection parameters for each frequency);
� SystemInformationBlockType8 contains information about CDMA2000 frequencies and CDMA2000
neighbouring cells relevant for cell re-selection (including cell re-selection parameters common for a
frequency as well as cell specific re-selection parameters);
� SystemInformationBlockType9 contains a home eNB identifier (HNBID);
� SystemInformationBlockType10 contains an ETWS primary notification;
� SystemInformationBlockType11 contains an ETWS secondary notification.
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1 RRC Connection Scenarios
1.3 Obtain Cell Parameters [cont.]
� The MIB is carried by the BCH channel.
� All the SIBs are carried by the DL-SCH.
BCCH
System Information
BCH DL-SCH
PBCH PDSCH
MIB only Other SIB
System information are broadcast in the whole cell
Transmitted in PDSCH with QPSK modulation and good coding rate
Signaled through PDCCH DCI1A with reserved RNTI value = SI-RNTI (0xffff)
System informations blocks are aggregated in system information (SI):
• systemInformationBlockType1 is a special SI that contains the most basic system informations as well as the
scheduling details of the other SI
• Other SI contain one ore more System information sharing the same transmission periodicity,
• Each SI is transmitted in parallel with other SI and benefits from HARQ repetitions
• Special HARQ processes identified by the SI-RNTI and the SI number (in the example above, 3 HARQ processes are
defined
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1 RRC Connection Scenarios
1.4 Random Access Procedure
� When the UE has obtained system information, it has to request an RRC connection. Like it has no dedicated resources, the UE requests the connection using the Random Access Procedure using common uplinkresources.
� At the end of the procedure, the UE is RRC connected
� UE and eNodeB are able to exchange data using dedicated radio resources
� This procedure is also used in case of:
� Initial access from RRC_IDLE
� RRC Connection Re-establishment procedure
� Handover
RRC_CONNECTED
(active state)
RRC_NULL
(detachedstate)
Traffic / HORRC Connection using Random
Access procedure
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1 RRC Connection Scenarios
1.4 Random Access Procedure [cont.]
� There are 4 steps to allow the UE to exchange signaling messages with the eNodeB
eNodeBRandom Access Preamble (msg1)
On the PRACH/RACH
Random Access Response (msg2)
On the PDCCH
Scheduled Transmission (msg3)
On the UL-SCH/PUSCH
Contention Resolution (msg4)
On the DL-SCH/PDSCH
The UE receives temporary C-RNTI to identify it on the air interface
The message also conveys the RRC Connection Request
Not synchronized with the previous message. The Temporary C-RNTI is promoted C-RNTI
Random Access Response
PDSCH signaled through PDCCH with RNTI = PRACH subframe number
Contains the signature index of the detected RACH preamble (1rst contention resolution step)
Contains the timing alignment command to apply (2 ways transmission time)
Contains a temporary RNTI assigned to the UE
Contains the resource assignment for next PUSCH (acts as DCI0)
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1.4 Random Access Procedure [cont.]
� The Physical Random Access Channel (PRACH):
� is made up of 6 RBs anywhere in the spectrum.
� occupies between 1 and 3 sub-frames per frame.
� The preamble:
� is generated from the Zadoff-Chu sequence.
� is associated to an RA-RNTI.
� There are 64 preamble sequences available per cell.
eNodeBPreamble
UL
DL
6 RBsfor the PRACH
The random access preambles are generated from Zadoff-Chu sequences with zero correlation zone (ZC-ZCZ)
generated from one or several root Zadoff-Chu sequences.
The random access preamble is 0.9 ms long (i.e. a 0.1 ms guard interval not to overlap in the next subframe)
It is Sent in specific subframes depending on RACH configuration parameter. It Contains an orthogonal
sequence chosen among 64 possible signatures
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1.4 Random Access Procedure [cont.]
� The response conveys:
� The RA-RNTI, to match the response with the preamble
� Timing alignment information
� The Temporary C-RNTI
� The initial UL grant, allocation of resources for the temporary C-RNTI.
� The C-RNTI identifies an RRC Connection.
eNodeB
Preamble Associated to an RA-RNTI
Random access response on PDCCH
PUSCH(RRCConnectionRequest)
contains RRC message for RRC connection establishment
NAS identity (S-TMSI) or randomNumber included in RRC message)
PDSCH(RRCConnectionSetup)
PDSCH signaled through PDCCH with RNTI = RNTI previously assigned to the UE
Contains a MAC header ‘contention resolution octet’ which is a repetition of the RRC PDU (2nd contention resolution step)
Contains a RRC message providing with signaling radio bearer configuration + physical configuration
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1.5 RRC Connection Establishment
� The main steps of the RRC connection establishment are:
eNodeBRRC Connection Request
RRC Connection Setup
RRC Connection setup complete
The request includes:- UE id (like TMSI)- Establishment cause
Radio resources configuration to establish the SRB1
SRB = Signaling Radio Bearer
Id of selected PLMNNAS dedicated information
After an RRC connection, several SRBs are established.
An SRB is a Radio Bearer (RB) used only for the transmission of RRC and NAS messages. More specifically, the
following three SRBs are defined:
� SRB0 is for RRC messages using the CCCH logical channel.
� SRB1 is for RRC messages as well as for NAS messages prior to the establishment of SRB2, all using the DCCH
logical channel.
� SRB2 is for NAS messages, using the DCCH logical channel. SRB2 has a lower priority than SRB1 and is always
configured by e-UTRAN after security activation.
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1.6 Attach Setup
� The Attach setup aims at establishing a default EPS bearer for user data between the UE and the P-GW.
� It includes:
� Authentication
� Allocation IP address
� Establishment of Radio bearer, S1 bearer, S5 bearer
PSTN
Internet
eNodeB
eUTRAN
CSCF
SGW
MGCF
MGWIMS
MME
P-GW
ePC
UE
EPS Bearer
S-GW
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2 Bearer Management
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2 Radio Management
2.1 EPS Bearer
� EPS is a connection-oriented transmission network and, as such, it requires the establishment of a “virtual” connection between two endpoints (e.g. a UE and a PDN-GW)
� This virtual connection is called an “EPS Bearer”
� It provides a “bearer service”, i.e. a transport service with specific QoSattributes.
� The QoS parameters associated to the bearer are: QCI, ARP, GBR and AMBR.
Internet
(PDN)
eNodeB
e-UTRANMME
P-GW
UE
EPS Bearer
S-GW
As a concept, the EPS Bearer corresponds to the “PDP Context” used in GPRS
As the mobile device is already known in the core network the following radio bearers are now established
automatically:
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2 Radio Management
2.1 EPS Bearer [CONT]
� A data radio bearer transports the packets of an EPS bearer between a UE and an eNB. � When a data radio bearer exists, there is a one-to-one mapping between this data radio bearer and the EPS bearer/E-RAB.
� An S1 bearer transports the packets of an E-RAB between an eNodeB and a Serving GW.
� An S5/S8 bearer transports the packets of an EPS bearer between a Serving GW and a PDN GW.
� The QoS parameters associated to the bearer are: QCI, ARP, GBR and AMBR.
P-GWS-GW PeerEntity
UE eNB
EPS Bearer
Radio Bearer S1 Bearer
End-to-end Service
External Bearer
Radio S5/S8
Internet
S1
E-UTRAN EPC
Gi
E-RAB S5/S8 Bearer
A low priority signaling (message) bearer (SRB1)
A high priority signaling (message) bearer (SRB2)
A data radio bearer (DRB), i.e. a bearer for IP packets
Part of the bearer establishment procedure are authentication and activation of encryption. The required
data for this process is retrieved by the base station (the eNodeB or eNB in 3GPP talk) from the Access
Gateway (aGW), or more precisely from the Mobility Management Entity (MME). The MME also delivers all
necessary information that is required to configure the data radio bearer, like for example min/max
bandwidth, quality of service, etc.
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2 Radio Management
2.2 QoS Parameters
� The QoS Class Identifier (QCI) is a scalar that is used as a reference to access node-specific parameters that control bearer level packet forwarding treatment (e.g. scheduling weights, admission thresholds, queue management thresholds, link layer protocol configuration, etc.).
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2.2 QoS Parameters [CONT]
� The Allocation and Retention Priority (ARP) primarily allows one to decide whether a bearer establishment request can be accepted orrejected in case of resource limitations.
� In addition, the ARP can be used by the eNodeB to decide which bearer(s) to drop during exceptional resource limitations (e.g. at handover).
� Each GBR bearer is additionally associated with the following bearer level QoS parameter:
� GBR = Guaranteed Bit Rate, the bit rate that can be expected to be provided by a GBR bearer
� MBR = Maximum Bit rate
� Each non-GBR is additionally associated with the following bearer level QoS parameter:
� UE-AMBR = UE Aggregate Maximum Bit Rate (in UL)
� APN-AMBR = APN Aggregate Maximum Bit Rate (in DL)
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2.3 Radio Bearer
� There are 2 types of Radio Bearers (RB):
� To carry signaling. There are called the SRB (Signaling Radio Bearer)
� To carry user data. There are associated with an EPS Bearer
� In LA1.X, the maximum number of RB per UE is 4
eNodeBUE
Signaling RB
User data -> RB
S-GW
S1 Bearer
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2.3 Radio Bearer [cont.]
The following types of Radio Bearer are defined:
� SRB1: RRC signaling with high priority
� SRB2: RRC signaling and NAS signaling (lower priority)
� Best Effort: also defined as the default EPS Bearer
� GBR: Radio Bearer with a guaranteed bit rate
� VoIP: Radio bearer to carry the VoIP
In LA1.X the following combination are supported:
� SRB1
� SRB1+SRB2+Best Effort
� SRB1+SRB2+Best Effort + GBR
� SRB1+SRB2+Best Effort + VoIP
� SRB1+SRB2+Best Effort + Best Effort
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2 Radio Management
2.3 Radio Bearer [cont.]
� At the RRC connection, the eNodeB scheduler creates a context for the UE containing the UEBearerList.
� this list is limited to 4 per user in LA1.X
� Each bearer is identified by the LCID (Logical Channel ID)
� Each bearer is associated with QoS parameters like :
� Max bit rate and guaranteed bit rate
� VoIP or not
� H-ARQ usage
UE
eNodeB
UEBearerList
Bearer1 ->LCID, QoS parameterBearer2 ->LCID, QoS parameterBearer3 ->LCID, QoS parameter
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2 Radio Management
2.3 Radio Bearer [cont.]
� Default Bearer vs Dedicated Bearer
� A default bearer is bearer able to carry all kinds of traffic (no filter) without QoS. It is typically created during the attach procedure
� A dedicated bearer is a bearer to carry a specific data flow, identify by the TFT (Traffic Flow Template), with a given QoS.
� Example: Voice, streaming
� It can be established:
� During the Attach procedure (depending on the user profile)
� After the Attach procedure, on demand
UEeNodeB
Established during the attach procedureSRB 1
SRB2
Default Bearer (Best Effort)
Established after the attach procedure
VoIP
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3 Traffic Operation
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3 Traffic Operation
3.1 Traffic Operation Overview
eNode-B
UE1
UE2
UE1
1. PUCCH / Reported CQIs
1. PUCCH / Reported CQIs
Scheduler
3. Control Information (PDCCH)
Data transmission (PDSCH)
4. PUCCH / Ack-Nack
2. Scheduling decisionDL Data Transmission
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3 Traffic Operation
3.1 Traffic Operation Overview [cont.]
eNode-B
UE1
1. PUCCH / Scheduling request
3. PDCCH / Scheduling Grants
Scheduler
4. PUSCH / Control & Data info
5. PHICH / Ack-Nack
2. Scheduling decisionUL Data Transmission
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3 Traffic Operation
3.1 Traffic Operation Overview [cont.]
� DL and UL schedulers are running in the eNodeB.
� From the following inputs, the eNodeB schedules the data on the air interface and indicates to the UE how to send (in UL) or receive (in DL) the data.
Scheduler
UE Category
Radio Resources available
Radio Measurement
Associated QoS parameters
Amount of data in the buffer
Scheduled user
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3 Traffic Operation
3.1 Traffic Operation Overview [cont.]
The DL scheduler is spit into 3 functional parts:
� The Static Scheduler:Which assigns a fixed amount of Transport Blocks as well as PDCCH and PDSCH resources for
the BCCH over the DL-SCH Transport Channel.
Those resources are permanently allocated.
� The Semi-static Scheduler:Which assigns Transport Blocks as well as PDCCH and PDSCH resources for PCCH and CCCH
over the PCH and DL PDSCH SCH Transport Channels.
The semi-static scheduler also assigns a regular set of Transport Blocks for all established
VoIP bearers.
� The Dynamic Scheduler:
Which assigns Transport Blocks as well as PDCCH and PDSCH resources for DCCH & DTCH
over the DL-SCH Transport Channels.
The dynamic scheduler is also in charge of sending the MAC Control Timing Advance control
messages in order to keep the UE in the connected mode, synchronized with the network
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3 Traffic Operation
3.1 Traffic Operation Overview [cont.]
The LTE DL scheduler is composed of 2 main algorithms:
� A pre-booking stage which reserve resources over the PDSCH for the static and semi-static schedulers.
� A scheduling stage which assign the resources over the PDSCH for effective traffic.
Static schedulerPre-booking
Every 20msInput is the Time Frequency ResBlock Occupancy with available PDSCH resources for L2
Semi-Static schedulerPre-booking
Output is Time Frequency Res Block Occupancy With blocks reserved for static and semi static scheduler.
Every msInput is the TimeFrequencyResBlocOccupancy with blocks reserved for static and semi-static scheduler.
Static schedulerScheduling
Semi-Static schedulerScheduling
Dynamic schedulerscheduling
Output is the interface to L1 for PDSCH& PDCCH
DL Scheduler pre-booking stage
DL Scheduler scheduling stage
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3 Traffic Operation
3.1 Traffic Operation Overview [cont.]
� UE categories
� These UE categories are often referred to as UE classes. The low end UE does not support MIMO but the high end UE will support 4x4 MIMO
� Whatever category a UE belongs to, it has to be capable of receiving transmissions from up to four antenna ports. This is because the system information can be transmitted on up to four antenna ports.
It should be noted that some of the capabilities are outside the UE category info. For example the Inter-RAT
capabilities like the support of EV-DO or GSM, etc is not specified as part of the UE categories. Similarly the
support of duplexing schemes and the support of UE-specific reference signals are outside the scope of this.
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3 Traffic Operation
3.1 Traffic Operation Overview [cont.]
� The channels used to carry high transmission data are:
� The PDSCH in Downlink
� The PUSCH in uplink
� The usage of these channels is packet optimized.
� There are no dedicated resources allocated to a UE.
� The resources, RB and slot, are allocated by the eNodeB scheduler dynamically.
� It takes in account the QoS requirements of each stream.
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� The data in DL are sent on the PDSCH
� A minimum of 2 RBs are allocated by the eNodeBs.� A RB is 12 sub-carriers on a slot (7 symbols).
� The eNodeB sends on the PDCCH the required information to allow the UE decode the data on the PDSCH.� On which slot?
� On which Resource blocks?
� How are the data modulated?
eNodeBPDSCH
RF A Slot
PDCCH
You will receive on the PDSCH
f
Resources Blocks
3 Traffic Operation
3.2 Data Transmission in DL
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3 Traffic Operation
3.2 Data Transmission in DL [cont.]
� The Physical Downlink Shared Channel (PDSCH) carries:
� User data
� User signaling
� Paging messages
� System information message
� The PDSCH can use all the resources not used by the other channel:
� Synchronization channels
� Reference signal
� PDCCH
� PBCH
� PCFICH
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3 Traffic Operation
3.2 Data Transmission in DL [cont.]
� The PDCCH, Physical Downlink Control Channel, allocates the DL and UL resources.
� There is one PDCCH per sub-frame.
� It helps the UE retrieve the transport blocks from the PDSCH:
� Allocated RB
� Modulation and Coding Scheme (MCS)
� Multi-antenna transmission
1 sub-frame PDCCH
� PDCCH
� Shared between all UE of the cell
� Each TTI contains an aggregation of PDCCH allowing to address several users simultaneously (UL and/or
DL)
� The CRC of each PDCCH is scrambled (XOR) with the UE RNTI
� Each UE tries to decode PDCCH and compares the resulting RNTI with its own identity (blind decoding)
� PDCCH resource granularity = 1 CCE (Control Channel Element)
� 1 CCE = 36 Resource Element = 72 bits (QPSK modulation only for PDCCH)
� Physical mapping is such that RE of a same CCE are scattered in time and frequency to get the best
diversity
� Physical mapping depends on the physical parameter ncell_id so that CCE of synchronized neigbouring
cells do not collide
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3 Traffic Operation
3.2 Data Transmission in DL [cont.]
� The reception of the PDCCH is essential for the data transmission.
� Its size and location are not pre-defined since the amount of control data depends on the traffic.
� The Physical Control Format Indication Channel (PCFICH):
� allows the UE to decode the PDCCH.
� is carried on pre-defined time-frequency resources.
� indicates the number of symbols occupied by the PDCCH.
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3 Traffic Operation
3.3 Data Transmission in UL
� In UL, the UE has no dedicated resources to transmit directly when new data arrived in the buffer from higher layer.
� It requests resources to transmit them.
� It receives radio resources.
� It transmits them.
eNodeB
MAC Layer
Data (http request)
How to send this packet?
MAC Layer
Scheduling Request
UL Grant
Buffer status & Data transmission
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3 Traffic Operation
3.3 Data Transmission in UL [cont.]
� The scheduling request is sent on the Physical Uplink Control Channel (PUCCH).
� This channel carries radio signaling in uplink:� Scheduling Request to grant resources in UL� Radio measurement report from the UEs� Radio retransmission ack or nack
� The UE can know from the SIB how to use the PUCCH.� The response, the UL grant, is sent on the PDCCH.
eNode-B
MAC Layer
Data (http request)
MAC Layer
Scheduling Request on the PUCCH
UL Grant on the PDCCH
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3 Traffic Operation
3.3 Data Transmission in UL [cont.]
� The Physical Uplink Share Channel (PUSCH) carries:
� User data
� User Signaling
� The resources are dynamically assigned in time and frequency.
� The PUSCH supports the H-ARQ.
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3 Traffic Operation
3.3 Data Transmission in UL [cont.]
� When the UE transmits in UL, it transmits also UL reference signals.
� Data demodulation reference signal (DM-RS)� Sent with each packet transmission in order to
demodulate data
� Occupies center SC-FDMA symbol of the slot, only sent over bandwidth allocated for data transmission
� Sounding reference signal (SRS)
� Used to sound uplink channel to support frequency selective scheduling
� SRS parameters are UE specific and configured semi-statically
� 1 symbol in subframe used for SRS
� Periodicity: {2, 5, 10, 20, 40, 80, 160, 320} ms
� Bandwidth: typically transmitted over the entire PUSCH bandwidth (does not include PUCCH region)
� SRS is not sent when there is a scheduling request (SR) or CQI to be sent on PUCCH (to avoid multi-carrier transmission)
UE 1
UE 2
UE 3
Slot = 0.5ms
Slot = 0.5ms
SRS (wideband)
DM-RS UE 1
DM-RS UE 2
DM-RS UE 3
1. Data demodulation reference signal (DM-RS)
� Sent with each packet transmission in order to demodulate data
� Occupies center SC-FDMA symbol of the slot, only sent over bandwidth allocated for data transmission
2. Sounding reference signal (SRS)
� Used to sound uplink channel to support frequency selective scheduling
� Channel sensitive scheduling in both time and frequency
� SRS parameters are UE specific and configured semi-statically
� 1 symbol in subframe used for SRS
� Periodicity: {2, 5, 10, 20, 40, 80, 160, 320} ms
� Bandwidth: typically transmitted over the entire PUSCH bandwidth (does not include PUCCH region)
� SRS is not sent when there is a scheduling request (SR) or CQI to be sent on PUCCH (to avoid multi-
carrier transmission)
� ALU implementation configures a wideband SRS with a period of 5ms
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3 Traffic Operation
3.4 DCI
� The PDCCH carries Downlink Control Information or DCI to indicate the resource assignment in UL or DL for one RNTI.
� A DCI can conveys various pieces of information, but the useful content depends on the specific case of system deployment or operations.� If the MIMO is not used during the transmission , there is no need to transmit the MIMO parameter in the DCI
� There are several format of DCI defined by the 3GPP for each need
eNodeB
PDCCH
DCIDCI
RB AssignmentMSC
H-ARQ infoPower Control
PUSCH
Data transmission
� UE feed backs the network with CQI (Channel Quality Indication) giving an estimation of the channel
quality
� The network adapts downlink transmission accordingly by changing:
� The coding rate (amount of information bits over number of transmitted bits)
� The modulation (QPSK, 16QAM, 64QAM)
� Radio resources are shared among users: a trade-off is needed between maximizing the bitrate and using
the smallest amount of resource blocks
� For MIMO configuration, the RI and PMI are also reported
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3 Traffic Operation
3.4 DCI [cont.]
� The main DCI formats are:
� Format 0
� For scheduling of the PUSCH (UL Grant)
� Format 1A
� Used during the Random Access Procedure
� Format 1
� For the scheduling of the PDSCH (DL Grant)
� In case of TxDiv
� Format 2A
� For the scheduling of the PDSCH (DL Grant)
� In case of Open Loop SU- MIMO
� Format 2
� For the scheduling of the PDSCH (DL Grant)� In case of Closed Loop SU- MIMO
� Downlink Control Information (DCI) used to grant UL/DL traffic
� DCI0 for uplink grant of PUSCH
� DCI1 and DCI1A for downlink grant of PDSCH with one single codeword
� DCI2 for downlink grant of PDSCH with one or two codewords (closed-loop MIMO)
� DCI2A for downlink grant of PDSCH with one or two codewords (open-loop MIMO)
� DCI carried in PDCCH transport channel
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3 Traffic Operation
3.5 Measurement Report
� The UE reports its measurements to the eNodeB.
� It is a key mechanism for:
� The Link adaptation, the selection of the modulation and coding rate.
� The e-UTRA mobility, in case of mobility in the e-UTRA coverage.
� The Inter-RAT mobility, if the UE is leaving the LTE coverage.
� The UE is able to measure:
� The serving cell
� The e-UTRA neighbors
� The UTRAN cell
� The GERAN cell
� The CDMA2000 cell eNodeB
To be able to optimize downlink transmissions by adapting the modulation and coding scheme (MCS), the
mobile device has to send channel quality indications (CQI) on the PUCCH and the PUSCH). In addition, the
mobile also collects measurements on neighboring cells and reports them to the base station whenever a
threshold is crossed (e.g. a neighboring cell is received better than the current cell).
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3 Traffic Operation
3.5 Measurement Report [cont.]
� The UE measures the Reference Signal which is a cell specific signal.� It depends on the Cell ID and so is different in 2 adjacent cells.
� It is sent every sub-frame
� Here is the mapping of this signal on a sub-frame:
12 sub-Ca = 1 RB
14 symbols = 2 slots = 1 Sub-frame
Cell-specific reference signals shall be transmitted in all downlink sub-frames in a cell supporting non-MBSFN
transmission. In case the sub-frame is used for transmission with MBSFN, only the first two OFDM symbols in a
sub-frame can be used for transmission of cell-specific reference symbols.
The measurement quantities on the RS are:
� The Reference Signal Received Power (RSRP)
� It is defined as the linear average over the power contributions of the resource elements that
carry cell-specific reference signals within the considered measurement frequency bandwidth.
� The Reference Signal Received Quality (RSRQ)
� It is defined as the ratio N×RSRP/(e-UTRA carrier RSSI), where N is the number of RBs of the E-
UTRA carrier RSSI measurement bandwidth. The measurements in the numerator and denominator
shall be made over the same set of resource blocks.
� The Received Signal Strength Indicator (RSSI)
� It comprises the linear average of the total received power observed only in OFDM symbols
containing reference symbols, in the measurement bandwidth, over N number of resource blocks
by the UE from all sources, including co-channel serving and non-serving cells, adjacent channel
interference, thermal noise etc.
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3 Traffic Operation
3.5 Measurement Report [cont.]
� The UE reports the Channel Quality Indicator (CQI) about its serving cell.
� The CQI is used by the scheduler to select the most adapted MCS.
5.554794864QAM15
5.115287364QAM14
4.523477264QAM13
3.902366664QAM12
3.322356764QAM11
2.730546664QAM10
2.406361616QAM9
1.914149016QAM8
1.476637816QAM7
1.1758602QPSK6
0.8770449QPSK5
0.6016308QPSK4
0.3770193QPSK3
0.2344120QPSK2
0.152378QPSK1
out of range0
efficiencycode rate x 1024modulationCQI index
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3 Traffic Operation
3.5 Measurement Report [cont.]
� The CQI is reported:
� periodically by the PUCCH.
� aperiodically by the PUSCH.
� In case multiple antennas are used, the UE can also report by means of the following channels:
� Precoding Matrix Indicator (PMI).
� Rank Indicator (RI).
eNodeB
PUCCH: periodic report
PUSCH: aperiodic report
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3 Traffic Operation
3.6 Radio Retransmission
� The radio retransmission mechanism is called Hybrid Automatic Request (H-ARQ).
� H-ARQ allows to retransmit fastly erroneous blocks between the eNodeBand the UE.
� It avoids long retransmission between 2 TCP layers.
Internet
e-UTRANMME
P-GW
ePC
UE
EPS Bearer
S-GW
Web server
TCP retransmission
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3 Traffic Operation
3.6 Radio Retransmission [cont.]
� The H-ARQ process runs in the eNodeB and in the UE.
� The H-ARQ is based on ACK/NACK messages carried by PUCCH or PUSCH.
� The LA1.X implementation is a hard HARQ technique:
� It reserves the same RB resources & MCS used for the initial transmission.
CombiningRx packets
Packet transmission
H-ARQ Re-Tx
H-ARQ NACK
H-ARQ ACK
eNode-B UE
Using information that was sent in the previous transmissions of the same block to increase the probability of
decoding
If data block not received correctly, soft values are stored in order to reuse them after the retransmission of
the block
When data is retransmitted, a different puncturing scheme is used so that the transmitted bit do not carry the
same information as the first time
If puncturing schemes are disjoint between two transmission, number of coded bits transmitted after the
second transmission is twice as high, thus coding rate has been divided by 2. After the third transmission,
coding rate has been divided by 3. Probability to decode the block is increased after each transmission.
If puncturing schemes are not disjoint, soft values corresponding to the samed bits are added. Decisions’
average reliability increases
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3.6 Radio Retransmission
3.6.1 H-ARQ Mechanism in DL
Transport Block#1
PDCCH
PDSCH
1
Soft buffer
TB #1
TB #1
2
Nack
PUCCH3
1. The Transport block is transmitted to the UE on the PDSCH.
2. The UE receives it but it is erroneous. The TB is stored in a buffer.
3. The UE transmits directly a NACK concerning the erroneous block on the PUCCH.
One HARQ entity in the UE and the e-UTRAN
Made of 8 HARQ processes in each direction (extended to 16 in DL MIMO)
Each process handles STOP and WAIT HARQ protocol
Each process is responsible for generating ACK or NACK indicating delivery status of PDSCH/PUSCH
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3.6 Radio Retransmission
3.6.1 H-ARQ Mechanism in DL [cont.]
Transport Block#1
PDCCH
PDSCH 1 Retransmission
Transportblock #1
TB #1 TB #1
Soft buffer
2 Combination
Ack
PUCCH
3 Acknowledgement
1. On reception of the NACK, the eNodeB retransmits the TB.
2. The UE receives it. Even if the retransmitted TB (Transport Block) is erroneous, the UE can try to
recombine the 2 TB to have a correct one.
3. The UE send a ACK on the PUCCH
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3.6 Radio Retransmission
3.6.2 H-ARQ Mechanism in UL [cont.]
Transport Block
PUSCH
1
TB #1
Soft buffer
TB #1
2
PHICH
NACK
3
In UL, it is the same principle, but the eNodeB send the ACK/NACK on a channel dedicated to the H-ARQ
called the PHICH.
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Answer the Questions 1
� Which ID is assigned by the eNodeB to the UE during the Random Access Procedure ?
A. The GUTI
B. The TMSI
C. The C-RTNI
D. The IP address
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Answer the Questions 2
� After the RRC connection, the UE can download a file by ftp ?
A. TRUE
B. FALSE
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Answer the Questions 3
� The CQI is:
A. Class identifier to attribute QoS parameters to EPS Bearer
B. Measurement feedback
C. Format of information on the PDCCH to assigned resources on the PDSCH
D. Name of a transport channel
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Answer the Questions 4
� To receive data on the PDSCH, the UE decodes:
A. The PBCH channel
B. The PDCCH channel
C. The PCFICH channel
D. The PUCCH channel
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Exercise 1
� Could you match each task with the appropriate channel?
� A task can require several channels.
Transmit user data in UL
Send a CQI
Reference signal
PUCCH
PUSCH
PDCCH
Identify the cell ID
Measure the quality of an adjacent cell
Receive user data in DL
PSS & SSS
PDSCH
PBCH
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Module Summary
� Thanks to the PSS, the SSS and the BCH, the UE can be synchronized and can obtain the System parameters
� The Random Access procedure allows a UE to contact the eNodeB using preamble on the PRACH
� During the RRC connection, a Signaling Radio Bearer (SRB) is established to exchange signaling between the UE and the eNodeB
� The attach procedure between the UE and the ePC is made of the authentication, the allocation of an IP address and the establishment of radio bearer depending on the user profile
� During data transfer, the UE measurement report allows the eNodeB to adapt the transmission
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End of ModuleeUTRAN Scenarios
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5All Rights Reserved © Alcatel-Lucent 2009
Module 5LTE Antenna System
9400 LTE RAN Radio PrinciplesDescription
TMO18214 D0 SG DEN Issue 4
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First editionLast name, first nameYYYY-MM-DD01
RemarksAuthorDateEdition
Document History
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Module Objectives
Upon completion of this module, you should be able to:
� Explain what is the Rx Diversity
� Explain what is the Tx Diversity
� Describe the different types of MIMO
� Explain what is the Beamforming
� Page 4
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Module Objectives [cont.]
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Table of Contents
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1 Terminology 71.1 Introduction 81.2 Single Antenna 91.3 Transmit Diversity 101.4 Receive Diversity 111.5 MIMO 121.5 MIMO Single User 141.6 MIMO Multi User 171.7 MIMO & Cell Traffic 18
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Table of Contents [cont.]
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1 Terminology
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1 Terminology
1.1 Introduction
� The multiple-antenna technique is not a synonym of MIMO.
� The main techniques are:
� MIMO
� Beamforming
� Diversity
� The principle is to use several antennas in transmission and/or reception to improve signal robustness and consequently system capacity or coverage.
eNodeB
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1 Terminology
1.2 Single Antenna
� SISO = Single Input Single Output
� It is the most basic radio channel access mode.
� Only one transmit antenna and one receive antenna are used.
� This is the form of communications that has been the default one since radio has begun. SISO is the baseline against which all the multiple antenna techniques are compared.
eNodeB
Using the 1 antenna in transmission and 1 antenna in reception is the standard configuration since the
beginning of the telecom.
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1 Terminology
1.3 Transmit Diversity
� MISO = Multiple Input Single Output� Principle
� More complex than SISO.
� 2 or more transmitters and one receiver.
� MISO is more commonly referred to as transmit diversity.
� The same data is sent on both transmitting antennas but coded in such a way that the receiver can identify each transmitter.
� Benefits� Transmit diversity increases the robustness of the signal to fading and can increase performance in low Signal-to-Noise Ratio (SNR) conditions.
� It does not increase data rates as such, but rather supports the same data rates using less power.
eNodeB
When the eNodeB uses 2 antennas in DL to transmit twice the same data, it is the diversity in transmission,
also called the TxDiv. It improve the quality and the coverage at the cell edge.
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1 Terminology
1.4 Receive Diversity
� SIMO = Single Input Multiple Output
� Principle
� It uses one transmitter and 2 or more receivers.
� It is often referred to as receive diversity.
� Benefits
� It is particularly well suited for low SNR conditions in which a theoretical gain of 3 dB is possible when two receivers are used.
� No change in the data rate since only one data stream is transmitted, but coverage at the cell edge is improved due to the lowering of the usable SNR.
eNodeB
The UE in UL can transmit only one stream, but with 2 antennas in reception, the eNodeB can receive twice
the signal. So it can combine them to improve the reception quality.
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1 Terminology
1.5 MIMO
� MIMO = Multiple Input Multiple Output
� 2 or more transmitters and 2 or more receivers.
� MIMO transmits several streams whereas SIMO or MISO transmits only one stream.
� If there are N streams, there will be at least N antennas (here only 2).
� By spatially separating N streams across at least N antennas, N receivers
will be able to fully reconstruct the original data streams
eNodeB
MIMO requires N antennas in transmitter and receiver and by this way it can transmit N streams in the same
radio resources on the same time. Currently, N=2 and there are 2 2 antennas on the eNodeB and 2 antennas
on the UE.
It allows to transmit 2 TB (Transport Block) on the same subframe for a given UE and by this it boosts the radio
performance.
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1 Terminology
1.5 MIMO [cont.]
� The transmissions from each antenna must be uniquely identifiable so that each receiver can determine what combination of transmissions has been received. This identification is usually done with pilot signals, which use orthogonal patterns for each antenna.
� There are several MIMO methods.
� The stream are sent on the same time, on the same frequency
Each antenna on the receiver receives the 2 TB (the red and the blue one). There are able after to separate
them.
The 2 TB are same on the same time and on the same frequencies (PRB). The receiver can separate them
because it knows the characteristics of transmission for each antennas in real time. There are a lot of RE
use for the reference signal of each antenna to allow the UE to distinguish them.
If the UE is not able to separate the 2 TB (because the 2 transmission paths are not enough different or the
radio condition are bad) the transmitter send the same TB on the 2 antennas.
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1 Terminology
1.6 MIMO Single User
� SU-MIMO = Single User MIMO
� It is the most common form of MIMO.
� Each user is served by only one BS and it occupies the resource exclusively, including time, frequency.
� It can be applied in the uplink or downlink.
� But it is generally applied only in DL. The UE can easily have 2 antennas in reception but only 1 antenna can transmit
eNodeB
The Single User MIMO is used in DL and means that the 2 TB send by the 2 antennas using the same radio
resources are for the same UE.
In UL, it is not possible to use this MIMO.
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1 Terminology
1.6 MIMO Single User
eNodeB
2 antennas on UE
2 antennas on eNodeB
ePC
� There are two operation modes in SU-MIMO spatial multiplexing:
� the closed-loop spatial multiplexing mode
� The UE reports the CQI, the RI (Rank Indicator) and the PMI (Precoding Matrix indicator)
� the open-loop spatial multiplexing mode
� The reports only the CQI and the RI
� The RI (Rank Indicator) indicates the number of spatial layers (data streams) that can be supported by the current channel experienced at the UE
� The PMI (Precoding Matrix Indicator) is the UE feedback
RI, PMI
The required UE feedback for the MIMO are:
- RI, Rank Indicator. By this one the UE can indicate if it is able to separate 2 TB. If Yes the eNodeB can use
the MIMO. If not it uses the TxDiv
- PMI, Precoding Matrix indicator. It is used only for the Closed Loop MIMO. The UE indicates the eNodeB how
to map the data on the 2 antennas to optimize the reception.
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1 Terminology
1.7 MIMO Multi User
� MIMO-MU = Multi user
� It is used only in Uplink.
� MIMO-MU does not increase the individual user’s data rate but it does offer cell capacity gains that are similar to, or better than, those provided by MIMO-SU.
� The UE does not require the expense and power drain of two transmitters, yet the cell still benefits from increased capacity.
� The UE must be well aligned in time and power as received at the eNB.
eNode-B
In UL, the UE can not transmit 2 different signal like it has only 1 amplifier. So to take benefit of the MIMO
capabilities, the eNodeB can allocates the same radio resources to 2 UEs (PRB and sub-frame). By this way,
he eNodeB boosts the capacity in UL.
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1 Terminology
1.8 MIMO & Cell Traffic
� The Tx Div can be applied on all the physical channels:
� Physical DL Shared Channel (PDSCH)
� Physical Broadcast Channel (PBCH)
� Physical Control Format Indicator Channel (PCFICH)
� Physical Downlink Control Channel (PDCCH)
� The other MIMO schemes are only applicable to the PDSCH
Like the MIMO required a UE-specific feedback (RI and PMI), it is not possible to use it for all the channel.
Only the PSDCH supports the MIMO and only for UE specific data.
For example, the SIB2 is transmitted on the PDSCH but it is received by all the UE, so TxDiv. The HO command
is transmitted only to a given UE, so MIMO can be used if criterion are fullfilled.
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1 Terminology
1.8 MIMO & Cell Traffic
� The 3 possible transmission mode are:
� TxDiV only
� MIMO-SU Open Loop
� MIMO-SU Closed Loop
� Depending on the selected mode, some specific CQI report modes can be configured and some specific DCI can be used
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Module Summary
� The TxDiv is the fact to transmit twice the same data stream in DL to improve the quality of the transmission
� The RxDiv is the fact to receive the signal with 2 antennas (in UL) to improve the quality of the transmission
� The MIMO uses multiple antennas on the receiver on the transmitter to send several streams on the same time and on the same sub-carrier
� In DL, it is the SU-MIMO (Single User)
� In UL, it is the MU-MIMO (Multi-User)
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End of ModuleLTE Antenna System
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Module 6Mobility Management
9400 LTE RAN Radio PrinciplesDescription
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First editionLast name, first nameYYYY-MM-DD01
RemarksAuthorDateEdition
Document History
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Module Objectives
Upon completion of this module, you should be able to:
� Describe the mobility mechanism when the UE is RRC connected, i.e. the handover
� Describe the mobility mechanism when the UE is in idle mode, i.e. the paging, the TAU and cell reselection
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Module Objectives [cont.]
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Table of Contents
Switch to notes view!Page
1 Introduction 71.1 Mobility Management 8
2 Handover 122.1 Types of Handover 132.2 Intra E-UTRAN Handover 142.3 Process 152.4 Measurements 17
3 Idle Mode 183.1 Principles 193.2 Paging 203.3 Tracking Area 233.4 Cell reselection 24
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Table of Contents [cont.]
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1 Introduction
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1 Introduction
1.1 Mobility Management
� The mobility management of a UE depends on its state.
� Depending on its state, there are different mechanisms to manage the mobility:
� Handover intra e-UTRA
� Handover Inter-RAT
� Cell reselection
� Idle mode and paging mechanisms
eNodeB
ePC
MME
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1 Introduction
1.1 Mobility Management [cont.]
� There are 2 EMM states
� EMM-DEREGISTERED
� The UE is not reachable by the MME.
� Some UE context is kept by the MME.
� EMM-REGISTERED
� The MME assigns this state to UE up on successful Attach.
� UE location is known by the MME at least with an accuracy of the tracking area list allocated to the UE.
� The UE, MME, S-GW and P-GW, all keep the UE context.
� Changing states
� The MME changes the UE state from EMM-REGISTERED to EMM-DERGISTERED for events like Attach Reject, TAU reject, Detach (for example, when the UE powers
off).
� EMM = EPS Mobility Management
Attach
Detach
EMM-DEREGISTERED EMM-REGISTERED
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1 Introduction
1.1 Mobility Management [cont.]
� There are 2 ECM states:
� ECM-Idle
� No Non-Access Stratum (NAS) signaling connection between UE and MME.
� The UE continues to take cell measurements for cell selection or reselection.
� ECM-Connected
� A UE has NAS signaling connection with the MME.
� UE location is known by the MME with an accuracy of the serving eNB.
� Mobility is handled by handover procedures.
� Changing states
� Transition to the ECM-Connected state is initiated by Attach, TAU, and service requests (for example, the UE clicks a button to read email).
� ECM -> EPS Connection Management
Signaling Connection
Established
Signaling Connection
Released
ECM-IDLE ECM-CONNECTED
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1 Introduction
1.1 Mobility Management [cont.]
No Mobility Management
EMM-DEREGISTERED EMM-REGISTERED
The UE is RRC_idle. It is known at the Tracking Area level• paging & TA update
ECM-IDLE
The UE is RRC Connected. It is known at the eNodeBlevel• Handover
ECM-CONNECTED
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2 Handover
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2 Handover
2.1 Types of Handover
WCDMA cell
CDMA2000 cell
� The Handover is the process of transferring an ongoing call or data session from one cell connected to the core network to another
� It is transparent for the end user
� It is network controlled and UE assisted
� The 3GPP defines handover:� Intra e-UTRAN
� Inter RAT with 3GPP technologies (GSM, WCDMA)
� Inter RAT with non-3GPP technologies (CDMA2000, HRPD)
ePC
MME
eNodeB
eNodeB
HO intra e-UTRAN
HO inter-RAT
HO inter-RAT with non-3GPP standard
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2 Handover
2.2 Intra E-UTRAN Handover
� The UE is RRC connected.
� During the HO:
� The radio link is released from the eNodeB 1 and re-established on the eNodeB 2
� The Control plane is switched to the eNodeB 2 and the MME
� The User plane is switched to the eNodeB 2 and the S-GW
eNodeB 1
MME
Serving GW
eNodeB 2
x2
S1-MME
S1-U
S11
User data
The Intra-e-UTRAN-Access Mobility Support for UEs in ECM-CONNECTED handles all necessary steps for
relocation/handover procedures, like processes that precede the final HO decision on the source network side
(control and evaluation of UE and eNB measurements taking into account certain UE specific area restrictions),
preparation of resources on the target network side, commanding the UE to the new radio resources and
finally releasing resources on the (old) source network side. It contains mechanisms to transfer context data
between evolved nodes, and to update node relations on C-plane and U-plane.
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2 Handover
2.3 Process
Source eNB Target eNB MME S-GW
Measurements
HO Decision
HO Request
Admission Control
HO ResponseRRC Reconfig
HO command
Detach from old cellSynchro with new cell
RRC Reconfig
SRB and RB re-establishment
The source eNB issues a HANDOVER REQUEST message to the target eNB passing the necessary information to
prepare the HO on target side (UE X2 signaling context reference at source eNB, UE S1 EPC signaling context
reference, target cell ID, KeNB*, RRC context including the C-RNTI of the UE in the source eNB, AS-
configuration, E-RAB context and physical layer ID of the source cell + MAC for possible RLF recovery). UE X2 /
UE S1 signaling references enable the target eNB to address the source eNB and the EPC. The E-RAB context
includes necessary RNL and TNL addressing information, and QoS profiles of the E-RABs.
Admission Control may be performed by the target eNB dependent on the received E-RAB QoS information to
increase the likelihood of a successful HO, if the resources can be granted by the target eNB. The target eNB
configures the required resources according to the received E-RAB QoS information and reserves a C-RNTI and
optionally an RACH preamble.
The target eNB prepares HO with L1/L2 and sends the HANDOVER REQUEST ACKNOWLEDGE to the source eNB.
The HANDOVER REQUEST ACKNOWLEDGE message includes a transparent container to be sent to the UE as an
RRC message to perform the handover. The container:
� includes a new C-RNTI, target eNB security algorithm identifiers for the selected security algorithms,
� may include a dedicated RACH preamble, and possibly some other parameters i.e. access parameters, SIBs,
etc.
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2 Handover
2.3 Process [cont.]
Source eNB Target eNB MME S-GW
Path switch
RequestUser plane update
Request
User plane update
ResponsePath switch
AckUE context
Release
Release Resources
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2 Handover
2.4 Measurements
� Measurements to be performed by a UE for intra/inter-frequency mobility are controlled by e-UTRAN, using broadcast or dedicated control.
� If the frequency center of the measured cell is the same
� No measurement gaps are required
� If the frequency center of the measured cell is not the same
� Measurement gaps are required
Source eNB
Measurement Control
Data Transfer and Measurements
Measurement Report
In RRC_CONNECTED state, a UE shall follow the measurement configurations specified by RRC directed from
the e-UTRAN (e.g. as in UTRAN MEASUREMENT_CONTROL).
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3 Idle Mode
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3 Idle Mode
3.1 Principles
� When there is no traffic during a given time, the radio link can be released to save resources. The RRC state is switched to RRC_Idle
� The UE is still attached to the network and the radio link can be re-established fastly in case of incoming traffic.
RRC Connected• UE has an e-UTRAN-RRC connection;• e-UTRAN knows the cell which the UE
belongs to• Network can transmit and/or receive
data to/from UE• Network controlled mobility (handover);• Neighbor cell measurements
RRC Idle• Broadcast of system information
• Paging
• Cell reselection mobility
• No RRC context stored in the eNB
Traffic
Traffic
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3 Idle Mode
3.2 Paging
� The idle UE is reachable in case of incoming traffic thanks to the paging mechanisms
MME
ePC
e-UTRAN
S-GW
P-GW
Incoming data
1
Paging message
2
Paging message over the air interface
3
Paging receivedIt requests a connection4
S-GW
When the UE is in idle mode, the Radio bearer and the S1 bearer are released. But the S5 bearer is still
maintains. By this way, when there are incoming data, the PGW is able to forward them to the SGW.
The SGW knows that the UE is attached but not connected. So it requests to the MME to wake up the UE by
paging.
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3 Idle Mode
3.2 Paging [cont.]
� The UE is inactive but monitors periodically the paging messages sent on the PDSCH.
� The DRX cycle is configurable.
� There is one paging occasion per cycle:
� It is negative if there is no DL incoming traffic.
� It is positive if there is an incoming packet.
� Rules known by the UE and the eNodeB allows to synchronize the paging occasion.
PCCH
PCH
PDCSH
Radio Frame
DRX cycle
Paging message
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3 Idle Mode
3.2 Paging [cont.]
� At the reception of a paging message, the UE requests the re-establishment of its context including SRB and RB for user traffic.
� The UE context is stored in the MME.
UE eNB MME
S1- AP: INITIAL CONTEXT SETUP COMPLETE+ eNB UE signalling connection ID+ Bearer Setup Confirm (eNB TEID)
S1-AP: INITIAL UE MESSAGE (FFS)+ NAS: Service Request+ eNB UE signalling connection ID
S1-AP: INITIAL CONTEXT SETUP REQUEST+ (NAS message)+ MME UE signalling connection ID+ Security Context+ UE Capability Information (FFS)+ Bearer Setup (Serving SAE-GW TEID, QoS profile)
RRC: Radio Bearer Setup(NAS Message)
RRC: Radio Bearer Setup Complete
Random Access Procedure
NAS: Service Request
PagingPaging
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3 Idle Mode
3.3 Tracking Area
� In idle mode, the network knows the location of the UE at the Tracking Area level.
� The Tracking Area is a group of cells. The Tracking Area Identifier (TAI) is sent over the Broadcast Channel.
� A paging message is sent on the UE tracking area and not on the whole network.
TAI 1
TAI 1
TAI 1
TAI 1
TAI 1
TAI 2
TAI 2
TAI 2
TAI 2
TAI 2
TAI 2
TAI 3
TAI 3
TAI 3
TAI 3
Tracking Area 1
Tracking Area 2Tracking Area 3
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3 Idle Mode
3.4 Cell Reselection
� Cell Reselection
� The UE in idle mode measures regularly the selected cell and the adjacent cells to always select the best cell.
� When the UE reselects a cell, it checks the TAI.
� It is not the same TAI as in the previous cell. So it performs a Tracking Area Update (TAU) to update its location.
TAI 1
TAI 1
TAI 1
BCCH
TAI 1
TAI 1
TAI 2
TAI 2
TAI 2
TAI 2
TAI 2
TAI 2
TAI 3
TAI 3
TAI 3
TAI 3
Tracking Area 1
Tracking Area 2Tracking Area 3
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Module Summary
� When a UE is EMM-REGISTERED, its context is known by the MME, the S-GW and the P-GW but it can be RRC connected or not (idle mode)
� The Handover is controlled by the eNodeB based on the UE measurement.
� If there is not enough traffic, the UE switches in Idle mode. It is not connected but still active to reselect always the best cell and to monitor the paging message
� In Idle mode, its location is known at the Tracking Area level (group of cell). There is a Tracking Area Update (TAU) when the UE reselect a cell which belongs to the current TA.
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End of ModuleMobility Management
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9400 LTE RAN Radio Principles DescriptionAbbreviations
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Abbreviations and Acronyms
Switch to notes view!
3G third Generation 3GPP third Generation Partnership Project
A
AAA Authentication, Authorization and Accounting AM Acknowledgement Mode AM Amplitude Modulation AMBR Aggregated Maximum Bit Rate ARP Allocation and Retention Priotity AS Access Stratum B
BCCH Broadcast Control Channel BCH Broadcast Channel
C
CCCH Common Control CHannel (GPRS) CDMA Code Division Multiple Access CP Cyclic Prefix CQI Channel Quality Indicator CRC Cyclic Redundancy Cycle C-RNTI Cell – Radio Network Temporary Identifier CS Coding Scheme CSCF Call Session Control Function
D
DCCH Dedicated Control Channel DL DownLink DL-SCH Downlink – Shared Channel DPSK Differential Phase Shift Keying DRX Discontinuous Reception DTCH Dedicated Traffic Channel E
ECM EPS Connection Management EDGE Enhanced Data rates for GSM Evolution EMM EPS Mobility Management eNB enhanced Node B ePC evolved Packet Core EPS evolved Packet Switch e-RAB evolved RAB e-UTRA evolved UTRA e-UTRAN evolved UTRAN EV-DO Evolution Data Optimized F FDD Frequency Division Duplex FDM Frequency Division Multiplexing FDMA Frequency Division Multiple Access FTT Fast Fourier Transformation FSK Frequency Shift Keying FT Fourier Transform G GBR Guaranteed Bit Rate GERAN GSM EDGE Radio Access Network GPRS General Packet Radio Service GSM Global System for Mobile communications
H
H-ARQ Hybrid Automatic Request HO Handover HRPD High Rate Packet Data HSDPA High-Speed Downlink Packet Access HSPA High-Speed Packet Access HSS Home Subscriber Server HSUPA High-Speed Uplink Packet Access HTTP HyperText Transfer Protocol
I ICI Inter-Channel Interference iFFT inverse Fast Fourier Transformation IMS IP Multimedia Subsystem IP Internet Protocol ISI Inter-Symbol Interference ITU International Telecommunications Union
L
LTE Long-Term Evolution M MAC Medium Access Control (GPRS) MBMR Multiband Multimode Radio MBMS Multimedia Broadcast/Multicast Service MBR Maximum Bit Rate MBSFN MBMS Single Frequancy Network MCCH MBMS point-to-multipoint Control Channel MCH Multicast Channel MCS Modulation Coding Scheme MGCF Media Gateway Control Function MGW Media Gateway MIB Management Information Base MIMO Multiple Input Multiple Output MIMO-MU MIMO-Multi User MIMO-SM MIMO-Spatial Multiplexing MIMO-STBC MIMO-Spatial Time Block Coding MIMO-SU MIMO-Single User MISO Multiple Input Single Output MME Mobility Management Entity MTCH MBMS point-to-multipoint Traffic Channel
N NAS Non-Access Stratum
O
OFDM Orthogonal Frequency Division Multiplexing OFDMA Orthogonal Frequency Division Multiplex
Access
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9400 LTE RAN Radio Principles DescriptionAbbreviations
6 � 3
Abbreviations and Acronyms [cont.]
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P PBCH Packet Broadcast Control Channel PCCCH Packet Common Control Channel PCFICH Physical Control Format Indication
Channel PCH Paging Channel PCRF Policy and Charging Rule Function PDA Personal Digital Assistant PDCCH Physical Downlink Control Channel PDCP Packet Data Convergence Protocol PDN Packet Data Network PDSCH Physical Downlink Shared Channel PDU Packet Data Unit P-GW PDN Gateway PLMN Public Land Mobile Network PMI Precoding Matrix Indicator PRACH Packet Random Access Channel P-SCH Primary SCH PSDSCH Physical Downlink Shared Channel PSTN Public Switched Telephone Network PUCCH Physical Uplink Control Channel PUSCH Physical Uplink Shared Channel Q QAM Quadrature Amplitude Modulation QCI QoS Class Identifier QoS Quality of Service QPSK Quadrature Phase Shift Keying R RAB Radio Access Bearer RACH Random Access Channel RA-RNTI Random Access – Radio Network
Temporary Identifier RAT Radio Access Technology RB Radio Bearer RB Resource Block REG Resource Element Group RF Radio Frame RFC Request For Comments RI Rank Indicator RLC Radio Link Control ROHC Robust Header Compression RRC Radio Resource Connection RSRP Reference Signal Received Power RSRQ Reference Signal Receive Quality RSSI Received Signal Strength Indicator RTP Real-Time Protocol Rx Reception
S
SC-FDMA Single Carrier - Frequency Division Multiple Access
SDU Service Data Unit S-GW Serving Gateway SIB Service Independent Building Block SIMO Single Input Multiple Output SISO Single Input Single Output SNR Signal-to-Noise Ratio SRB Signaling Radio Bearer
S-SCH Secondary Synchronization Channel
T
TA Tracking Area TAI Tracking Area Identifier TAU Tracking Area Update TB Transport Block TCP Transport Control Protocol TDD Time Division Duplex TF Transport Format TM Transport Mode TMSI Temporary Mobile Subscriber Identity TTI Transmission Time Interval TTL Time To Live Tx Transmission
U UDP User Data Packet UE User Equipment UL UpLink UL-SCH Uplink Shared Channel UM Unacknowledge Mode UMA Unlicensed Mobile Access UMTS Universal Mobile Telecommunications System UTRA Universal Terrestrial Radio Access UTRAN Universal Terrestrial Radio Access Network V VoIP Voice over IP W
WCDMA Wideband Code Division Multiple Access WiMAX Worldwide interoperability for Microwave Access Z
ZC-ZCZ Zadoff-Chu sequences with Zero Correlation Zone
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9400 LTE RAN Radio Principles DescriptionAbbreviations
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End of Module
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