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Exploring LTEDay 1
11-12 th Sep 13
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Contents
Day 1 LTE Overview LTE Architecture LTE Interfaces and Protocols LTE Air Interface
OFDMA and SC- FDMA Frame Structure
MIMO Air Interface Channels and Protocols LTE EPS Session Management LTE Mobility Aspects LTE Network Planning
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Contents
Day 2 LTE Signaling
LTE Procedures Parameters
KPIs and Counters NSN LTE solution approach
Radio Transport Core
LTE Key Features
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Contents
Day 1 LTE Overview LTE Architecture LTE Interfaces and Protocols LTE Air Interface
OFDMA and SC- FDMA Frame Structure
MIMO Air Interface Channels and Protocols LTE EPS Session Management LTE Mobility Aspects LTE Network Planning
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Mobile broadband traffic more than doublesevery year, Video traffic dominates since 2011
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Motivation for LTEThe Communications Service Provider view
Source: Light Reading (adapted)Voice dominated Data dominated
Traffic volume
Revenue
Time
Network cost (LTE)
Network cost(existing technologies)
Profitability
LTE reduces the cost/Mb
LTE improves
user experience
Mobile network
traffic and costs
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Motivation for LTESubscriber view: better broadband experience
Broadbandeverywhere
LTEon low
frequencybands, e.g.digital dividend
High-SpeedBroadband
Capacity forall
LTE
on largefrequency bands,e.g. 2.6GHz
10-20ms latency100 Mbps peak data rate
already with initial devices
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Main LTE Requirements [3GPP TS25.913]
Peak data rates of uplink/downlink 50/100 Mbps Reduced Latency:
Enables round trip time
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Standardisation bodies around LTE
Next Generation Mobile Networks . Is a group of mobileoperators to share, assess, and drive aspects of mobilebroadband technologies focusing on LTE & EPC (EvolvedPacket Core) and its evolution .More in www.ngmn.org
Collaboration agreement established in December1998. The collaboration agreement brings together anumber of telecommunications standards bodies: ARIB,CCSA, ETSI, ATIS, TTA, and TTC.More in www.3gpp.org
LTE/SAE Trial Initiative . The LTE/SAE Trial Initiative (LSTI)is a global collaborative technology trial driven by vendorsand network operator focused on accelerating the availabilityof commercial and inter-operable next generation LTE mobilebroadband systems.More in http://www.lstiforum.com/
LSTI
http://www.ngmn.org/http://www.3gpp.org/http://www.lstiforum.com/http://www.lstiforum.com/http://www.3gpp.org/http://www.ngmn.org/8/12/2019 LTE Overview 110913 Day1 v3
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TD-LTE specific Initiative : GTI
Founded by leading mobile network operators in 2011.
Global TD-LTE Initiative (GTI) is a virtual open platform toadvocate co-operation among global operators to promote TD-LTE.
GTI is formed to create value for stakeholders across the TD-LTEecosystem for early adoption of the technology and convergenceof TD-LTE and LTE FDD.
GTI organizes a series of activities to bring operators andvendors together for sharing development strategies andtechnology know-how, expediting the development of terminalsand fostering of global roaming and low-cost terminals, etc
More info http://www.lte-tdd.org/
http://www.lte-tdd.org/http://www.lte-tdd.org/http://www.lte-tdd.org/http://www.lte-tdd.org/8/12/2019 LTE Overview 110913 Day1 v3
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3GPP LTE Background (1/2)Milestones
End 2004 3GPP workshop on UTRAN Long Term Evolution March 2005 Study item started December 2005 Multiple access selected March 2006 Functionality split between radio and core agreed September 2006 Study item closed & approval of the work items December 2007 1st version of all radio specs approved
March 2008 3GPP Release 8 Stage 1 specifications were frozen December 2008 3GPP freeze of LTE as part of Release 8 (exceptionsfor the EPC to be completed until March2009)
2005 2006 2007 2008
Feasibilitystudy started
Multipleaccess
selected
Feasibilitystudy closed
Work itemstarted
Work planapproved
Stage 2approved
Stage 3approved
Radio Specsapproved
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3GPP LTE Background (2/2)Schedule
2009 Start of Customer Trials March 2009 Ratification of 3GPP Release 8: LTE standardization is completed and approved by 3GPP Release 8 supporting FDD and
TDD modes with the same specification and hardware components
2010 3GPP Release 9 gets ready. Self-organised networks 2011 3GPP Release 10 gets ratified (LTE A) 2012 3GPP Release 8 networks deployments for TDD
2008 2009 2010 2011
DemonstrateLTE AirInterface
Performance
Operator Trials.Friendly-usenetworks
LTE NetworksLaunch:
commercialsolution
available(3Q2010)
Large Scale LTENetworks.
VoIP serviceoptimized.
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LTE OverviewMarket Trends
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Why LTE?Superior mobile broadband user experience
GSM HSPA+
LTE
Throughput latency
GSM HSPA+ LTE
10ms
100 Mbps 150ms
380 million LTE subscribersby 2015
Forecast for LTE lead markets by Research andMarkets
Technology convergence
GSM
WCDMA
CDMA
WiMAX
TD-SCDMA
FDDLTE
TD-LTE
LTEAdvanced>90% harmonizedin 3GPP
Extensive range of radio spectrum support
23 different FDD frequency band options11 different TDD frequency band options
+ new ones still being specifiedboth for new
band deployment and re-farmingcases
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LTE in 2012
continuing in 2013
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Worldwide LTE Footprints
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LTE Network Deployments
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TDD LTE Presence
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Global TDD LTE Networks
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LTE Operating Bands
LTE TDDbands
LTE FDDbands
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Spectrum used in LTE FDD deployments
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Mobile Subscriptions by Technology
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LTE Subscriptions
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Worldwide LTE Subscribers Key Operators
Source Infonetics Research
As of Ju ne 30, 2013 (2Q13)
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LTE Regional Subscriptions Share: Q1 2013
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LTE User Segmentation
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LTE Device Update
Multi-band, multi-mode LTE dongles and CPEs are commercially available from allmajor chipset and device manufacturers.Most of the 948 LTE user devices confirmed by GSA are Category 3 as defined by the3GPP standard40 Category 4 devices are available, in most form factors
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TDD LTE Devices
Bands 38 (2.6 GHz) and 40 (2.3 GHz) have the largest ecosystems of TDLTE user devices.
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What are the LTE challenges?
Best price, transparent flat rate Full Internet Click-bang responsiveness
reduce cost per bit provide high data rate provide low latency
The Users expectation ..leads to the operators challenges
Netwok challenges Backhaul Devices availability Interoperability
LTE: lower cost per bit and improved end user experience
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Contents
Day 1 LTE Overview
LTE Architecture LTE Interfaces and Protocols LTE Air Interface
OFDMA and SC- FDMA Frame Structure MIMO
Air Interface Channels and Protocols LTE EPS Session Management LTE Mobility Aspects LTE Network Planning
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Evolution Path to LTEOperator migration paths to LTE
Enabling flat broadband architecture
TDSCDMAGSM /
(E)GPRS
LTE
CDMA
I-HSPA
WCDMA /HSPA
>90 % of world radio access market migrating to LTE
TD-LTE
WiMaX
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Network Architecture Evolution
S- GW + P-GWGGSN
SGSN
RNC
Node B(NB)
Direct tunnel
GGSN
SGSN
I-HSPA
MME
HSPA R7 HSPA R7 LTE R8
Node B +RNC
Functionality
EvolvedNode B(eNB)
GGSN
SGSN
RNC
Node B(NB)
HSPA
HSPA R6
LTE
User planeControl Plane
Flat architecture : single network element in userplane in radio network and core network
LTE/EPC N k A hi
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LTE/EPC Network Architecture
Main references to architecture in 3GPP specs: TS23.401,TS23.402,TS36.300
Evolved UTRAN (E-UTRAN)
MME S10
S6a
ServingGateway
S1-U
S11
PDNGateway
PDN
Evolved Packet Core (EPC)
PCRFGx Rx
SGiS5/S8
HSS
MobilityManagement
Entity Policy &Charging Rule
Function
S-GW /P-GWLTE-UE
Evolved Node B(eNB)
X2
LTE-Uu
eNB
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LTE Interworking with 2G/3G Networks
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LTE Interworking with 3G Alternative
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EPC Network Elements (1/2)MME: Mobility Management Entity Pure signalling entity inside the EPC:
Signalling coordination for EPC bearer setup/release Subscriber attach/detach Tracking area updates Roaming Control Trigger and distribution of paging messages to UE
Security control Authentication, integrity protection
Serving Gateway Manages the user data in the EPC
Receives packet data from the eNodeB and sends packet data to it
HSSeNB
MME
ServingGateway
S1-U
S1-MME
S11S6a
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EPC Network Elements (2/2)
Packet Data Network Gateway Connection between EPC and a number of external data networks (comparable
to GGSN in 2G/3G networks) IP Address Allocation for UE Packet Routing/Forwarding between
Serving GW and external Data Network Packet screening (firewall functionality)
Policy and Charging Rule Function Quality of Service (QoS) negotiation with the external PDN Charging Policy: How packets should be accounted
HSS: Home Subscriber Server Permanent and central subscriber database Stores mobility and service data for every subscriber Contains AuC (authentication center) functionality
MME
ServingGateway
S5/S8
PDNGateway
PDNSGi
PCRFS7 Rx+
S11HSS
S6a
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Inter-cell RRM: HO, load balancing between cells
Radio Bearer Control: setup , modifications andrelease of Radio Resources
Connection Mgt. Control: UE State Management,MME-UE Connection
Radio Admission Control
eNode B Meas. collection and evaluation
Dynamic Resource Allocation (Scheduler)
eNB Functions
IP Header Compression/ de-compression
Access Layer Security: ciphering and integrityprotection on the radio interface
MME Selection at Attach of the UE
User Data Routing to the S-GW/ P-GW
Transmission of Paging Msg coming from MME
Transmission of Broadcast Info (e.g. System info,MBMS)
Only network element defined aspart of eUTRAN
Replaces the old Node B / RNCcombination from 3G.
Provides all radio managementfunctions
To enable efficient inter-cell radiomanagement for cells not attachedto the same eNB, there is a inter-eNB interface X2 specified. It willallow to coordinate inter-eNBhandovers without direct involvementof EPC during this process.
Evolved Node B (eNB)
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LTE/EPC Network Architecture
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LTE/EPC Network Architecture
Main references to architecture in 3GPP specs: TS23.401,TS23.402,TS36.300
Evolved UTRAN (E-UTRAN)
MME S10
S6a
ServingGateway
S1-U
S11
PDNGateway
PDN
Evolved Packet Core (EPC)
PCRFGx Rx
SGiS5/S8
HSS
MobilityManagement
Entity Policy &Charging Rule
Function
S-GW /P-GWLTE-UE
Evolved Node B(eNB)
X2
LTE-Uu
eNB
LTE R di I f d h X2 I f
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LTE Radio Interface and the X2 Interface
LTE-Uu interface Air interface of LTE
Based on OFDMA in DL and SC-FDMA inUL
FDD and TDD duplex methods Scalable bandwidth 1.4MHz to currently
20 MHz
X2 interface Inter eNB interface X2AP: special signalling protocol Functionalities:
In inter- eNB HO to facilitate handoverand provide data forwarding.
Provides load information toneighbouring eNBs Logical interface: It does not need direct
site-to-site connection
(E)-RRC User PDUs User PDUs
PDCP
..
RLC
MAC
LTE-L1 (FDD/TDD-OFDMA/SC-FDMA)
TS 36.300
eNB
LTE-Uu
eNB
X2
User PDUs
GTP-U
UDP
IPL1/L2
TS 36.424
X2-UP(User Plane)X2-CP
(Control Plane)
X2-AP
SCTP
IPL1/L2TS 36.421
TS 36.422
TS 36.423
TS 36.421
TS 36.420[currently also in TS 36.300]
S1 MME & S1 U I f
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S1-MME & S1-U Interfaces
S1-MME interface Control interface between eNB and
MME S1AP:S1 Application Protocol MME and UE will exchange non-
access stratum signaling via eNBthrough this interface (i.e.authentication, tracking area updates)
S1-U interface
User plane interface between eNB andserving gateway Pure user data interface (U=User plane)
MME
ServingGateway
S1-MME(Control Plane)
S1-U
(User Plane)
NAS Protocols
S1-AP
SCTP
IP
L1/L2
User PDUs
GTP-U
UDP
IP
L1/L2
TS 36.411
TS 36.411
TS 36.412
TS 36.413
TS 36.414
TS 36.410[currently in TS 36.300]
eNB
S1 interface is divided into two parts:
S10 d S6 i f
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S10 and S6a interfaces
S10
Interface between different MMEs Used during inter-MME tracking area
updates It is a pure signaling interface, no user
data runs on it
S6a
Interface between the MME and theHSS The MME uses it to retrieve
subscription information from HSSduring attach
S11 d S5/8 i f
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S11 and S5/8 interface
S11 Interface between MME and SGW
A single MME can handle multipleServing GWs, each one with itsown S11 interface
Used to coordinate theestablishment of SAE bearerswithin the EPC.
S5/S8 Interface between SGW and
PGW S5: If Serving GW and PDN GW
belong to the same network (non-roaming case)
S8: Roaming case, mainly usedto transfer user packet databetween PDN GW and SGW
S7 d SGi I t f
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S7 and SGi Interface
S7> Interface between PGW and PCRF
> It allows the PCRF to request thesetup of a SAE bearer withappropriate QoS
> To indicate profile changes to thePCRF to apply a new policy rule.
SGi> Interface used by the PDN GW to
send and receive data to and from theexternal data network> It is either IPv4 or IPv6> This interface corresponds to the Gi
interface in 2G/3G networks
S3 d S4 I t f
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S3 and S4 Interface
S3/S4> Interfaces between EPC and 2G/3G packet switched core network domain> They would allow inter-system changes between SAE and 2G/3G> The S3 is a pure signaling interface used to coordinate the inter-system change between
MME and SGSN> The S4 is the user plane interface and it is located between SGSN and Serving GW
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S9 Interface
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S9 Interface
S9> Interface between the hPCRF and the vPCRF used in roaming cases.> To retrieve QoS profile from hPCRF to vPCRF
SCTP
IP
L1/L2
DIAMETER
S9 Application
hPCRF
S9(Control Plane)
vPCRF
TS 29.215
Charging Architecture Non Roaming
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Charging Architecture Non Roaming
Charging Architecture
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Charging Architecture
> Charging for LTE/SAE is performed on a per IP bearer basis.
> The network elements involved in LTE/SAE charging are:> The PCRF for charging rule instructions
> The PDN GWs Policy & Charging Enforcement Function (PCEF) with its collectionand credit control client functions,
> The Serving GW with its collection functions for interoperator charging.
> The Charging Gateway Function (CGF), collecting CDR for offline charging.> The Online Charging Function (OCS), containing credit information for online
charging.
> The Billing System (BS)
Gy Interface
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Gy Interface
SCTP
IP
L1/L2
DIAMETER
DCCA
Gy(based on Diameter)
OCS
TS 32.299
PDNGateway
PCEF
Gy Interface between the P-GW and the Online Charging System (OCS) OCS is used for flow based charging information transfer. The Gy interface uses Diameter Credit-Control application (DCCA), as
defined in IETF RFC 4006
LTE/SAE Roaming Architecture Case 1
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LTE/SAE Roaming Architecture Case 1
LTE/SAE Roaming Architecture Case 2
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LTE/SAE Roaming Architecture Case 2
LTE Interworking with non 3gpp Access
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LTE Interworking with non 3gpp Access
Contents
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Contents
Day 1 LTE Overview
LTE Architecture LTE Interfaces and Protocols LTE Air Interface
OFDMA and SC- FDMA Frame Structure MIMO
Air Interface Channels and Protocols LTE EPS Session Management LTE Mobility Aspects LTE Network Planning
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LTE Air InterfaceOFDM Concepts
Multiple Access
1 2 3UE 1 UE 2 UE 3 4 UE 4 UE 55
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Multiple Access
1 2 3 4 5
2
12345
4 2
1
23
45
31
15
53
3
24
1
P o w e r
Frequency
TDMATime Division
MultipleAccess,
2G e.g. GSM,PDC
FDMAFrequency
DivisionMultipleAccess
1G e.g. AMPS,NMT, TACS
CDM
Code DivisionMultiple Access3G e.g. UMTS,
CDMA2000
1 2 3UE 1 UE 2 UE 3 4 UE 4 UE 55
OFDMAOrthogonalFrequency
DivisionMultiple Access
e.g. LTE
OFDM Technology
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OFDM TechnologyOFDM stands for Orthogonal Frequency Division Multiplexing
OFDM is a multicarrier transmission technique which is based on FDM. The maindifference between single carriers system and OFDM relates to how the informationis mapped onto many separately modulated carriers
FDM System: FDM system utilizes multiple frequencies to simultaneously transmit multiple signals inparallel
OFDM System: OFDM uses the similar concept as FDM but increases the spectral efficiency by enablingthe spacing between subcarriers to be reduced untill they are effectively overlapping. This can be done sinceOFDM utilizes subcarrier frequencies which are orthogonal
OFDM
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OFDM[+] Advantages: The cancellation of inter-symbol interference makes more complex the
hardware design of the receivers. In WCDMA for instance the RAKE receiverrequires a huge amount of DSP capacity with high data rate. OFDM makes theISI cancellation more easy.
OFDM makes the radio interface more robust Easy for system design with IFFT/FFT, low cost Flexible for resource selection on Frequency domain
[-] Disadvantage: OFDM system has high requirement on time
and frequency synchronization High PAPR
Multicarrier Transmission and Reception
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Multicarrier Transmission and Reception
Use of IFFT and FFT in generating OFDM Signal
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Use of IFFT and FFT in generating OFDM Signal
OFDM Basics (I)
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OFDM Basics (I)
Transmits hundreds or even thousands of separately modulated radio signals
using orthogonal subcarriers spread across a wideband channel
Orthogonality:
The peak (centrefrequency) of onesubcarrier
intercepts thenulls of theneighbouringsubcarriers
15 kHz in LTE: fixed
Total transmission bandwidth
OFDM Basics (II)
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OFDM Basics (II)
Data is sent in parallel across the set of subcarriers, each subcarrier onlytransports a part of the whole transmission
The throughput is the sum of the data rates of each individual (or used) subcarrierswhile the power is distributed to all subcarriers
FFT (Fast Fourier Transform) is used to create the orthogonal subcarriers. Thenumber of subcarriers is determined by the FFT size (by the bandwidth)
Power
frequency
bandwidth
Challenges for the Air Interface Design
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Challenges for the Air Interface Design
The usage of the pulse leads to other challenges to be solved:
1. ISI = Intersymbol InterferenceDue to multipath propagation
2. ACI = Adjacent Carrier InterferenceDue to the fact that FDM = frequency division multiplexing willbe used
3. ICI = Intercarrier Interference
Losing orthogonality between subcarriers because of effectslike e.g. Doppler
What should be the solutions to these challenges? (see next slides)
OFDM and Multipath
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OFDM and Multipath
Multipath causes Inter Symbol Interference (ISI) which affects the subcarrierorthogonality due to phase distortion
Solution to avoid ISI is to introduce a Guard Period (Tg) after the pulse Tg needs to be long enough to capture all the delayed multipath signals To make use of that Tg (no transmission) Cyclic Prefix is transmitted
4
time
TsTime Domain
time
time
Tg
1
2
3
time
When the delayspread of the multi-path is greater thanthe guard periodduration (Tg) there isinter-symbolinterference (ISI) 4
12
3
Cyclic Prefix (CP) and Guard Time
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Cyclic Prefix (CP) and Guard Time
Note: CP represents anoverhead resulting in symbolrate reduction.
Having a CP reduces thebandwidth efficiency but thebenefits in terms of minimisingthe ISI compensate for it
t
total symbol time T(s)
Guard Time
T(g)
CPT(g)
Useful symboltime T(b)
Consists in copying the last part of a symbol shape for a duration of guard-timeand attaching it in front of the symbol
CP needs to be longer than the channel multipath delay spread. A receiver typically uses the high correlation between the Cyclic Prefix (CP) and
the last part of the following symbol to locate the start of the symbol and beginthen with decoding
2 CP options in LTE: Normal CP: for small cells or with short multipath delay spread Extended CP: designed for use with large cells or those with long delay profiles
OFDM: Orthogonal Frequency Division Multi-Carrier
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O D : O t ogo a eque cy D v s o u t Ca e
OFDM allows a tight packing of small carrier - called thesubcarriers - into a given frequency band.
No ACI (Adjacent Carrier Interference) in OFDM
due to the orthogonal subcarriers !
P o w e r
D e n
s i t y
P o w e r
D e n s
i t y
Frequency (f/fs) Frequency (f/fs)
SavedBandwidth
Challenges for the Air Interface Design
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g g
The usage of the pulse leads to other challenges to be solved:
1. ISI = Intersymbol InterferenceDue to multipath propagation solution: use cyclic prefix
2. ACI = Adjacent Carrier Interference
Due to the fact that FDM = frequency division multiplexingwill be used
solution: orthogonal subcarriers
3. ICI = Intercarrier InterferenceLosing orthogonality between subcarriers because of effectslike e.g. Doppler solution: use reference signals will be explained later
Different Methods for OFDM Multiple Access
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.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Plain OFDM
time
s u
b c a r r
i e r
...
...
...
...
...
...
...
...
...
1
1
1
1
11
.
.
.
2
2
2
2
22
.
.
.
3
3
3
3
33
.
.
.
.
.
.
.
.
.
Time Division Multiple Accesson OFDM
time
s u
b c a r r i e r
...
...
...
...
...
...
...
...
...
1
1
1
1
11
2
2
2
2
22
OFDMA is registered trademark of Runcom Technologies Ltd.
1 1 1
1
.
.
.
2
2 2
2...
3 33 3 3
.
.
.
.
.
.
.
.
.
Plain Orthogonal FrequencyMultiple Access
OFDMA
time
...
...
...
...
...
...
...
...
...
1 1
1 1 1 1
2 22
2 2 2
13 33 3 3
1 1 1 1
s u
b c a r r
i e r
1
1
1
.
.
.
2
.
.
.
3
.
.
.
.
.
.
.
.
.
Orthogonal FrequencyMultiple Access
OFDMA
time
...
...
...
...
...
...
...
...
...
1
1
1 1
2
22
2 2
3 33 3 3
1
s u
b c a r r
i e r
1
1 1 1
111
3 3 3
33 3 3 3
3
Resource Block (RB)1 2 3 common info(may be addressed via HL)UE 1 UE 2 UE 3
p
OFDMA Parameters
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Frame duration: 10ms created from slots and subframes Subframe duration (TTI): 1 ms (composed of 2x0.5ms slots)
Subcarrier spacing: Fixed to 15kHz Sampling Rate: Varies with the bandwidth but always factor ormultiple of 3.84 to ensure compatibility withWCDMA by using common clocking
Frame Duration
Subcarrier Spacing
Sampling Rate (MHz)
Data Subcarriers
Symbols/slot
CP length
1.4MHz 3 MHz 5 MHz 10 MHz 15 MHz 20 MHz
10 ms
15 kHz
Normal CP=7, extended CP=6
Normal CP=4.69/5.12 sec, extended CP= 16.67sec
1.92 3.84 7.68 15.36 23.04 30.72
72 180 300 600 900 1200
10ms
Peak-to-Average Power Ratio in OFDMA
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g
The transmitted power is the sum of thepowers of all the subcarriers
Due to large number of subcarriers, thepeak to average power ratio (PAPR)tends to have a large range
The higher the peaks, the greater therange of power levels over which thepower amplifier is required to work
Having a UE with such a PA that worksover a big range of powers would beexpensive
Not best suited for use with mobile(battery-powered) devices
SC-FDMA and OFDMA
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OFDMA transmits data in parallel across multiple subcarriers SC-FDMA transmits data in series employing multiple subcarriers
In the example: OFDMA: 6 modulation symbols (01,10,11,01,10 and 10) are transmitted per OFDMA
symbol, one on each subcarrier SC-FDMA: 6 modulation symbols are transmitted per SC-FDMA symbol using all
subcarriers per modulation symbol. The duration of each modulation symbol is 1/6 th of themodulation symbol in OFDMA
OFDMA SC-FDMA
SC-FDMA and OFDMA
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LTE Air InterfaceFrame Structure
LTE Physical Layer Structure Frame Structure
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(FDD) FDD Frame structure ( also called Type 1 Frame ) is common to both uplink and
downlink. Divided into 20 x 0.5ms slots
Structure has been designed to facilitate short round trip time
10 ms frame
0.5 ms slot
s0
s1
s2
s3
s4
s5
s6
s7
s 18 s 19..
1 ms sub-frame
SF 0 SF 1 SF 2 SF 9..
sy 4sy 0 sy 1 sy 2 sy 3 sy 5 sy 6
0.5 ms slot
SF 3
- Frame length =10 ms- FDD: 10 ms sub-frame for UL
and 10 ms sub-frame for DL
- 1 Frame = 20 slots of 0.5ms each- 1 slot = 7 ( normal CP) or 6
symbols ( extended CP)
SF: SubFrame
s: slot
Sy: symbol
LTE Physical Layer Structure Frame Structure
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Presentation / Author / Date
(TDD) Frame Type 2 : similar in time-domain to FDD but with some specific fields to
enable also TD-SCDMA co-existence (China)
A radio frame (10ms) contains 2 half frames of 5ms each Two switching point periodicities: 5m or 10 ms Each half frame carries 5 subframes Subframes 1 and 6 are special subframes and consist of three specialised fields
inherited from TD-SCDMA with configurable lengths subject to a total of 1ms
Subframes 0, 5 and DwPTS are always reserved for downlink Subframes 2, 7 and UpPTS are reserved for uplink in case 5 ms switch-pointperiodicity
Remaining fields are dynamically assigned between UL and DL
DwPTS: Downlink Pilot time Slot
UpPTS: Uplink Pilot Time SlotGP: Guard Period to separate between UL/DL
UL/DL Configurations ( TDD)
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TDD allows for flexible bandwidth allocation between uplink and downlink tosupport asymmetric traffic The number of subframes dedicated to uplink and downlink within the 10ms frame can be
adjusted7 different frame configurations
Chosen UL/DL Configuration should be the same across all cells of a network to avoidinterference between transmission directions
NSNs first TD release (RL15TD) supports Configuration 1 and 2 only. Configuration1 provides almost 1:1 UL-to-DL ratio
Special Subframe Configuration (TDD)
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Total length of special subframe is 1ms but the length of the each field may vary 9 different formats supported NSNs first TD release supports formats 5 and 7
Fields : Downlink Pilot time Slot
A regular shortened downlink subframe Contains reference signals and control information It may carry data at discretion of the scheduler
Contains PSS (note: SSS is transmitted on the last symbol of subframe 0) Uplink Pilot Time Slot
Mainly used for RACH transmission Guard Period
Switching point between downlink and uplink transmission
Compensates for the delay when switching between transmission directions Its length determines the maximum supportable cell size
SUBFRAME 1
Subframe structure and CP length
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Normal cyclic prefix:
Extended cyclic prefix:
Copy= Cyclic prefix
= Data
5.21 s
16.67 s
Subframe length is 1 ms for all bandwidths A Subframe contains 2 slots. The slot length is 0.5 ms Slot carries 7 symbols with normal CP or 6 symbols with extended CP. The
length of the CP depends on the symbol position within the slot: Normal CP: symbol 0 in each slot has a CP length of = 160 x Ts (5.21 s) and
remaining symbols have a CP length of = 144 x Ts (4.7 s) Extended CP: CP length for all symbols in the slot is 512 x Ts (16.67s)
Ts: sampling time of theoverall channel. Basic TimeUnit
Ts =1 sec
Subcarrier spacing X max FFT size
Ts = 32.5nsec
Normal and Extended Cyclic Prefix
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Normal Cyclic Prefix
160 Ts 144 Ts
2048 Ts
Ts = 1/30720 msCyclic Prefix
144 Ts 144 Ts 144 Ts 144 Ts 144 Ts
2048 Ts 2048 Ts 2048 Ts 2048 Ts 2048 Ts 2048 Ts
7 2048 Ts+ 6 144 Ts+ 1 160 Ts
15360 Ts = 0.5 ms
Main Body
512 Ts 512 Ts
2048 Ts
Ts = 1/30720 ms
Cyclic Prefix
512 Ts 512 Ts 512 Ts 512 Ts
2048 Ts 2048 Ts 2048 Ts 2048 Ts 2048 Ts
6 2048 Ts+ 6 512 Ts
15360 Ts = 0.5 ms
Main Body
Extended Cyclic Prefix
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Resource Element
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Theoretical minimum capacity allocation unit
Equivalent to one subcarrier x one symbol period 72 or 84 Resource Elements per Resource Block Each Resource Element can accommodate 1 modulation symbol, e.g. 2
bits for QPSK, 4 bits for 16QAM and 6 bits for64 QAM Modulation symbol rate per Resource Block is 144 ksps or 168 ksps
Case 1: Normal Cyclic Prefix Case 2: Extended Cyclic Prefix
7 symbols = 0.5 ms 6 symbols = 0.5 ms
F r e q u e
n c y
D o m a
i n
1 2 s u
b c a r r i e r s =
1 8 0 k H z
Resource Element
1 2 s u
b c a r r
i e r s =
1 8 0 k H z
Time Domain Time Domain
Modulation Schemes
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b 0 b 1
QPSK
Im
Re10
11
00
01
b 0 b 1b 2b 3
16QAM
Im
Re
0000
1111
Im
Re
64QAM
b 0 b 1b 2b 3 b 4 b 5
3GPP standard defines the following options: QPSK,16QAM, 64QAM in both directions (UL and DL) UL 64QAM not supported in RL15TD
Not every physical channel is allowed to use anymodulation scheme:
Scheduler decides which form to use depending on carrierquality feedback information from the UE
QPSK:
2 bits/symbol
16QAM:
4 bits/symbol
64QAM:
6 bits/symbol
Physicalchannel
Modulation
PDSCH QPSK,16QAM,64QAM
PMCH QPSK,16QAM,64QAM
PBCH QPSKPDCCH
(PCFICH,)
QPSK
PUSCH QPSK,16QAM,64QAM
PUCCH BPSKand/orQPSK
PHICH BPSK
Modulation and TB Size
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DL MCSsMCS I TBS MCS_index Mod order
0-QPSK 0 0 21-QPSK 1 1 22-QPSK 2 2 2
3-QPSK 3 3 24-QPSK 4 4 25-QPSK 5 5 26-QPSK 6 6 27-QPSK 7 7 28-QPSK 8 8 29-QPSK 9 9 2
10-16QAM 9 10 411-16QAM 10 11 4
12-16QAM 11 12 413-16QAM 12 13 414-16QAM 13 14 415-16QAM 14 15 416-16QAM 15 16 417-64QAM 15 17 618-64QAM 16 18 619-64QAM 17 19 620-64QAM 18 20 6
21-64QAM 19 21 622-64QAM 20 22 623-64QAM 21 23 624-64QAM 22 24 625-64QAM 23 25 626-64QAM 24 26 627-64QAM 25 27 628-64QAM 26 28 6
From TS 36.213 (DL example shown here)
MCS index -> from 0 to 28 -> it is decided bythe scheduler which should translate a specificCQI in an MCS index
Modulation Order -> indicates the modulationtype (QPSK, ) by indicating the number of bitsper symbolQPSK = 216QAM = 464QAM = 6
ITBS = TBS indexThe TBS Index is mapped to a specific TBS sizefor a specific #RBsUses a different table
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LTE Air InterfaceMIMO
Multiple-Input Multiple-Output MIMO Principle
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Tm
T2
T1
Rn
R2
R1
Input
M x NMIMOsystem
Output
MIMO: Multiple-Input Multiple Output M transmit antennas, N receive antennas form MxN MIMO system huge data stream (input) distributed toward m spatial distributed
antennas; m parallel bit streams (Input 1..m) Spatial Multiplexing generate parallel virtual data pipes using Multipath effects instead of mitigating them
Signal from j th Tx antenna
S j
MIMOProcessor
MIMO Principle (2/2)
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Tm
T2
T1
Rn
R2
R1
MIMOProcessor
Input
M x NMIMO
Output
h 1,1h 2,1h n,1
h n,2
h n,m
h 2,2h 2,m
h1,mh 1,2
Receiver learns Channel Matrix H inverted Matrix H -1 used forrecalculation
of original input data streams 1..mm
ji j jii n sh y
1,
Signal at i th Rx antenna
YiSignal from j th Tx antenna
S j
n i: Noise at receiver
H =h 1,1h 2,1
h n,1
h 1,2h 2,2
h n,2
h 1,mh 2,m
h n,m
Transmit diversity for two antennas
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Benefit: Diversity gain, enhanced cell coverage
Each Tx antenna transmits the same stream of data with different coding and
different subcarriers -> Receiver gets replicas of the same signal which increasesthe SINR. Synchronization signals are transmitted only via the 1 st antenna eNode B sends different cell-specific reference signals per antenna It can be enabled on cell basis by O&M configuration
Processing is completed in 2 phases: Layer Mapping: distributing a stream of data into two streams Pre-coding: generation of signals for each antenna port
Spatial multiplexing (MIMO) for two antennas
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S1
S2
Benefit: Double the peak rate compared to a 1Tx antenna
Spatial multiplexing with two code words Supported physical channel: PDSCH
Two code words(S1+S2) are
transmitted inparallel to oneUE whichdoubles thepeak rate
LayerMapping
L1
L2
Precoding
Map ontoResourceElements
Map ontoResourceElements
OFDMA
OFDMA
Modulation
Modulation
Code word1
Code word2
Scale
W2
W1
2 code wordstransferred whenchannelconditions aregood
Signal generation is similar to TransmitDiversity: i.e. Layer Mapping & Precoding
Can be open loop or closed loop dependingif the UE provides feedback
DL adaptive open loop MIMO for two antennas
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Benefit: High peak rates (two code words) and good celledge performance (single code word)
2 TX antennas Dynamic selection between
Transmit diversity Open loop spatial multiplexing with
two code words Supported physical channel: PDSCH Dynamic switch considers the UE specific
link qualityTwo code words (A+B) aretransmitted in parallel to one UEwhich doubles the peak rate
One code word A istransmitted via twoantennas to one UEwhich improves the LiBu
AB
A
Downlink Adaptive Closed Loop MIMO
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2 TX antennas
Transmission mode 4 Dynamic selection for between
Rank 1 Rank 2
based on filtered CQI, PMI and rank
information Operator configurable thresholds for the
MIMO switch
same codewords
differentcodewords
Contents
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Day 1 LTE Overview
LTE Architecture LTE Interfaces and Protocols LTE Air Interface
OFDMA and SC- FDMA Frame Structure MIMO
Air Interface Channels and Protocols LTE EPS Session Management LTE Mobility Aspects LTE Network Planning
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Air Interface Protocols
Radio Protocols Architecture
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MAC
RLC
PDCP
Physical Layer
RRC
L1
L2
L3
Radio Bearer
Logical Channel
Transport Channels
Control Plane User Plane
Physical Channels
LTE Protocol Layers
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9696
RRC:
Broadcast of system information Radio connection management & Radio bearers Paging, handovers, QoS management, Radio Measurement Control
PDCP:
Ciphering, Header Compression (RoCH) Integrity protection for C-plane data Transfer of U-plane and RRC Data
LTE Protocol Layers
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9797
MAC:
Mapping & multiplexing of logical channels to transport channels Hybrid-ARQ error correction Priority handling, Scheduling Random access management Transport format selection (part of LA)
RLC: Transfer of upper-layer PDUs Managing different transfer modes Error correction (ARQ) Concatenation, Segmentation and reassembly of RLC SDUs
IP / TCP | UDP |
Application LayerNAS Protocol(s)(Attach/TA Update/)
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FDD | TDD - Layer 1( DL: OFDMA, UL: SC-FDMA )
Medium Access Control (MAC)
Physical Channels
Transport Channels
RLC(Radio Link
Control)
PDCP (Packet Data
ConvergenceProtocol)
RLC(Radio Link
Control)
PDCP (Packet Data
ConvergenceProtocol)
RLC(Radio Link
Control)
PDCP(Packet Data
ConvergenceProtocol)
RLC(Radio Link
Control)
PDCP(Packet Data
ConvergenceProtocol)
RLC(Radio Link
Control)
PDCP(Packet Data
ConvergenceProtocol)
Logical Channel
(E-)RRC(Radio Resource Control)
IP / TCP | UDP |
Radio Bearer
ROHC (RFC 3095)
Security
Segment./Reassembly
ARQ
Scheduling /Priority Handling
HARQ
De/Multiplexing
CRC
Coding/Rate Matching
Interleaving
Modulation
Resource Mapping/MIMO
NAS Protocols Transfer
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MME
eNBUE MME
NAS NAS
RRC RRC
PDCP PDCP
RLC RLC
MAC MAC
PHY PHY
Data Flow ExampleE-Mail (IP packet) FTP Download (IP packet)
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Header HeaderPayload Payload
PDCPHeader
PDCPHeader
PDCP PDU PDCP PDU
PDCP SDU PDCP SDU
RLCHeader
RLCHeader
RLCHeaderRLC SDU RLC SDU RLC SDU
MACHeader
MACHeader
RLC PDU RLC PDU
Transport block Transport blockCRC CRC
( p ) ( p )
H HPayload PayloadPDCP
RLC
MAC
PHY
PDU = Protocol Data UnitSDU = Service Data Unit
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LTE Channels
LTE Channels
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Upper Layers
RLC
MAC
PHY
Logicalchannels
Transportchannels
B C C H
C C C H
P C C H
MT
C H
M C C H
B C H
P C H
DL - S
C H
RA
C H
UL - S
C H
P B
C H
P D
S C H
P HI C H
P D
C C H
P C F I C H
P M
C H
P U C C H
P RA
C H
P U S C H
M C H
C C C H
D C C H
DT
C H
ULDL
Air interface
D C C H
DT
C H
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Downlink Physical Channels
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PDSCH: Carries user dataPBCH: For system info (cell IDs, cell status, allowed
services, RACH parameters)
PMCH: For multicast traffic as MBMS servicesPHICH: Carries H-ARQ Ack/Nack messages from eNB
to UE in response to UL transmission
There are no dedicated channels in LTE, neither in UL nor DL
PCFICH: Carries details of PDCCHs format (e.g.# of symbols)PDCCH: Carries resource assignment messages for downlink capacity allocations and scheduling
grants for uplink allocations
Downlink Physical Channels Allocation PBCH
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PBCH: Occupies the central 72 subcarriers across 4 symbols Transmitted during second slot of each 10 ms radio frame on
all antennas PCFICH: Can be transmitted during the first 3 symbols of
each TTI Occupies up to 16 RE per TTI
PHICH:
Normal CP: Tx during 1 st symbol of each TTI Extended CP: Tx during first 3 symbols of each TTI Each PHCIH group occupies 12 RE
PDCCH: Occupies the RE left from PCFICH and PHICH within the first 3
symbols of each TTI Minimum number of symbols are occupied. If PDCCH data is
small then it only occupies the 1 st symbol PDSCH:
Is allocated the RE not used by signals or other physicalchannels
Uplink Channels
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MAC layer provides the logical channels to RLC layer Transport channels in LTE have been reduced (also for DL direction) by using
in shared channel operation ( no dedicated channels like in WCDMA )
Uplink Physical Channelsh l l k h d h l
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PUSCH : Physical Uplink Shared Channel Intended for the user data (carries traffic for
multiple UEs)
PUCCH: Physical Uplink Control Channel Carries H-ARQ Ack/Nack indications, uplink
scheduling request, CQIs and MIMO feedback If control data is sent when traffic data is being
transmitted, UE multiplexes both streamstogether
If there is only control data to be sent the UEuses Resources Element at the edges of thechannel with higher power
PRACH: Physical Random Access Channel For Random Access attempts. PDCCH
indicates the Resource elements for PRACHuse PBCH contains a list of allowed preambles
(max. 64 per cell in Type 1 frame) and therequired length of the preamble
RACH
CCCH DCCH DTCH
UL-SCH
PRACH PUSCH PUCCH
Logical
Transport
PHYS.
RLC
MAC
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Physical Resource Mapping
DL Cell-Specific Reference Signals Mapping
Channel estimation in LTE is based on reference signals
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0l 0 R
0 R
0 R
0 R
6l 0l 0 R
0 R
0 R
0 R
6l
O n e a n
t e n n a p o r t
T w o a n
t e n n a p o r t s
Resource element ( k,l )
Not used for transmission on this antenna port
Reference symbols on this antenna port
0l 0 R
0 R
0 R
0 R
6l 0l 0 R
0 R
0 R
0 R
6l 0l
1 R
1 R
1 R
1 R
6l 0l
1 R
1 R
1 R
1 R
6l
0l 0 R
0 R
0 R
0 R
6l 0l 0 R
0 R
0 R
0 R
6l 0l
1 R
1 R
1 R
1 R
6l 0l
1 R
1 R
1 R
1 R
6l
F o u r a n
t e n n
a p o r t s
0l 6l 0l
2 R
6l 0l 6l 0l 6l 2 R
2 R
2 R
3 R
3 R
3 R
3 R
even-numbered slots odd-numbered slots
Antenna port 0
even-numbered slots odd-numbered slots
Antenna port 1
even-numbered slots odd-numbered slots
Antenna port 2
even-numbered slots odd-numbered slots
Antenna port 3
Cell-specific reference signals shall be transmitted in all downlink Slots Reference signals position in time domain is fixed whereas in frequency
domain it depends on the Cell ID and slot number parity In case more than one antenna is used (e.g. MIMO) the Resource
elements allocated to reference signals on one antenna are DTX on theother antennas
MIMO and the OFDMA Reference SymbolsANTENNA 1 ANTENNA 2f
UnusedResourceElement
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OFDM Symbols/ Time Domain
S u
b - c a r r
i e r s
/ F r e q u e n c y
D o m a i n
ANTENNA 1
OFDM Symbols/ Time Domain
S u
b - c a r r
i e r s
/ F r e q u e n c y
D o m a i n
ANTENNA 2 ReferenceSymbol
DL Physical Channels Allocation PBCH:
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PBCH: Occupies the central 72 subcarriers across 4 symbols Transmitted during second slot of each 10 ms frame
on all antennas PCFICH:
Transmitted during the first symbol of each TTI Occupies up to 16 RE per TTI
PHICH: Tx during 1 st symbol of each TTI or alternativ during
symbols 1 to 3 of each TTI PhichDur Each PHCIH group occupies 12 RE
PDCCH: Occupies the REs not used by PCFICH and PHICH
within the first 1, 2 or 3 symbols of each TTI (case 1.4MHz: within the first 2, 3 or 4 symbols)
In RL15TD: configuration static bymaxNrSymPdcch
PDSCH: Is allocated the RE not used by signals or other
physical channels
RB
Uplink Physical Signals and Channels
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Uplink Reference Signals Demodulation Signals:
Used for channel estimation in theeNodeB receiverLocated in the 4 th symbol of each slotand spans the same bandwidth as theallocated uplink data
Sounding Reference Signals:Provides uplink channel qualityestimation as basis for the ULscheduling decisions -> similar in use asthe CQI in DLSent in different parts of the bandwidthwhere no uplink data transmission isavailable.
Uplink Physical Channels Physical Uplink Shared Channel (PUSCH) Physical Uplink Control Channel (PUCCH) Physical Random Access Channel
(PRACH)
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Mobility and Connection States (1/2)
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2 sets of states for the UE are defined based on the information held in the MME : EMM: EPS Mobility Management States
ECM: EPS Connection Management States EMM:
EMM- DEREGISTEREDMME holds no valid location information about the UE (location unknown)
EMM- REGISTEREDUE performs Tracking Area Update procedures to notify availabilityUE responds to paging messagesUE performs service request procedure to establish the radio bearers whenuplink data is to be sent
EMMderegistered
EMMregistered
AttachDetach
EPS: EvolvedPacket System
Mobility and Connection States (2/2)
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ECM: UE and MME enter ECM-CONNECTED state when the signaling connection is
established between UE and MME UE and E-UTRAN enter RRC-CONNECTED state when the signaling
connection is established between UE and the E-UTRAN
ECM idle ECMconnected
S1 connection establishment
S1 connection release
RRC idle RRC
connected
RRC connectionestablishment
RRC connectionrelease
UEE-UTRAN MME
MMES1 connectionRRC connection
LTE Radio Resource Control (RRC) States
dl d
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RRC Idle state No signalling connection between UE
and network exists
UE performs cell reselections Paging needed when the there is data in
downlink direction RACH procedure used on RRC
connection establishment No RRC context stored in the eNB (No
C-RNTI).
UEs RRC connection can be maintained even if UE is inactive RRC connection may be released due to the following reasons:
RRC Connected State A signalling connection exists between
UE and network
UE location is known in MME with anaccuracy of a cell ID
The mobility of UE is handled by thehandover procedure
The UE performs the tracking areaupdate procedure
inactive > x min1. UE is inactive for a long time
2. Max number of RRC connected UEs reached.Then, longest inactive UE is released
EMM & ECM States TransitionsPower On
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EMM_Deregistered
ECM_Idle
Power On
Registration (Attach)
EMM_Registered
ECM_Connected
Allocate C-RNTI, S_TMSI Allocate IP addresses Authentication Establish security context
Release RRC connection Release C-RNTI Configure DRX for paging
EMM_Registered
ECM_Idle
Release due toInactivity
Establish RRC Connection Allocate C-RNTI
New TrafficDeregistration (Detach)Change PLMN
Release C-RNTI, S-TMSI Release IP addresses
Timeout of Periodic TAUpdate
Release S-TMSI Release IP addresses
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LTE Bearers
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The Default Bearer Concept
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Each UE that is attached to the LTE network has at least one beareravailable, that is called the default bearer .
Its goal is to provide continuous IP connectivity towards the EPC ( always-on concept) From the QoS point of view, the default bearer is normally a quite basic
bearer If an specific service requires more stringent QoS attributes, then a
dedicated bearer should be established.
cell
S1-U
UE
S5PDN
Sgi
eNB
ServingGateway
PDNGateway
Default EPS Bearer
MME
S1-MMES11
EPS Bearer QoS Attributes
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EPS Bearer QoS Parameters(To be defined per Bearer )
Default Bearer/Dedicated Bearer
GBR/N-GBR
MBR
UL/DL-TFT
QCI
ARP
EPS Bearer QoS Parameters(To be defined per User) AMBR
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Contents
Day 1
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Day 1 LTE Overview LTE Architecture LTE Interfaces and Protocols LTE Air Interface
OFDMA and SC- FDMA Frame Structure MIMO
Air Interface Channels and Protocols LTE EPS Session Management LTE Mobility Aspects LTE Network Planning
LTE/EPS Mobility Areas
T d fi d f h dli f bili i LTE/EPS
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Two areas are defined for handling of mobility in LTE/EPS:
Tracking Area (TA) It is the successor of location and routing areas from 2G/3G. When a UE is attached to the network, the MME will know the UEs
position on tracking area level. In case the UE has to be paged, this will be done in the full tracking
area. Tracking areas are identified by a Tracking Area Identity (TAI).
The Cell Smallest entity regarding mobility When the UE is connected to the network, the MME will know the
UEs position on cell level Cells are identified by the Cell Identification (CI) and by the Physical
Cell Identification (PCI)
Tracking Areas
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S-eNBTAI3TAI3
TAI3
TAI3
TAI3TAI3
TAI3
MME
eNB
TAI2
TAI2TAI2
TAI2
TAI2
TAI2TAI2
TAI2
TAI1
TAI1TAI1
TAI1
TAI1 eNB 1 2
MME
3
Cell Identity
Tracking Area
Tracking Area Identity (TAI) vs. Tracking Area Code (TAC)TAI= MCC + MNC + TAC
Tracking Area Update(TAU)Procedure triggered by theLTE-UE moving to a newTA.TAU are performed by theLTE-UE in both idle andconnected mode.(GSM/UMTS difference)For further info refer to TS23.401 chapter 5.3.3.0
LTE Handover Principles
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Lossless Packets are forwarded from the source to the target
Network-controlled Target cell is selected by the network, not by the UE Handover control in E-UTRAN (not in packet core)
UE-assisted Measurements are made and reported by the UE to the network
Late path switch Only once the handover is successful, the packet core is involved
Handover Procedure
Handover Late path
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S-GW + P-GW
MME
SourceeNB
TargeteNB
MME MME MME
= Data in radio= Signalling in radio= GTP tunnel= GTP signalling
= S1 signalling= X2 signalling
Before handover Handoverpreparation Radio handoverLate pathswitching
S-GW + P-GW
S-GW + P-GW S-GW + P-GW
X2
Intra frequency handover via X2
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Basic Mobility Feature Event triggered handover based
on DL measurements (ref.signals)
Network evaluated HO decision Operator configurable
thresholds for
coverage based and best cell based handover
Data forwarding via X2 Admission Control gives priority
to HO related access over otherscenarios
S1
S1 X2
MMES-GW
P-GW
Feature ID(s): LTE53
A reliable and lossless mobility
Intra LTE Handover via S1
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Extended mobility option
Handover in case of no X2 interface between eNode B,
e.g. multi-vendor scenarios
eNode Bs connected to different CN
elements, e.g. MME relocation Same measurements and triggers as for X2
based handover
DL Data forwarding via S1S1
S1MMESAE-GW
UE Identifications
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IMSI International Mobile Subscriber Identity
GUTI Global Unique Temporary Identity
C-RNTI Cell Radio Network Temporary Identity
S-TMSI S Temporary mobile subscriber IdentityRA-RNTI
Random Access Radio Network Temporary IdentitySI-RNTI
System Information Network Temporary IdentityP-RNTI
Paging Radio Network Temporary Identity
Contents
Day 1
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y LTE Overview LTE Architecture LTE Interfaces and Protocols LTE Air Interface
OFDMA and SC- FDMA Frame Structure MIMO
Air Interface Channels and Protocols LTE EPS Session Management LTE Mobility Aspects LTE Network Planning
Radio Planning Process Overview
DIMENSIONING C t ti f b f it t
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DIMENSIONING: Computation of number of sites to servecertain area to fulfil customer requirements (Dim Tool)
NOMINAL PLANNING: Creation of a nominal Plan Coverage planning with planning tool (i.e. Atoll, NetAct
Planner)Based on coverage thresholds
Capacity analysis Site surveys and site pre-validation
DETAILED PLANNING: Capacity analysis with planning tool Site validation eNodeB Parameter planning (i.e. frequency, paging groups,
site data built with default parameters)
PRE-LAUNCH OPTIMISATION: Cluster acceptance Drive test measurements, analysis and changes
implementation Data build assessment/ consistency
DIMENSIONING
NominalPlanning
DetailedPlanning
Pre-launchOptimisation
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Link Budget Example
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DL ULOperating Band (MHz) 2300
Channel Bandwidth (MHz) 20Tx Power per Antenna (dBm) 40.0 23.0
Antenna Gain (dBi) 18.0 0.0Feeder Loss (dB) 2.0 -Body Loss (dB) - 1.0
Total Tx Power Increase (dB) 3.0 -User EIRP (dBm) 59.0 22.0Feeder Loss (dB) - 2.0
Antenna Gain (dBi) 0.0 18.0Noise Figure (dB) 8.0 3.0
Body Loss (dB) 1.0 -
Total Number of PRBs per TTI 100Cyclic Prefix Normal Normal
Number of OFDM Symbols per Subframe 14 14DL-to-UL configuration DL-to-UL Conf 2
Special Subframe Format "S" Subframe Format 7Number of Regural DL/UL Subframes 6.0 2.0
Number of Special Subframes 2.0DwPTS/UpPTS Length (OFDM symbols) 10.0 2.0
GP Length (OFDM symbols) 2.0
DL/UL Ratio 74.29% 20.00%
Modulation and Coding Scheme 5-QPSK 4-QPSKService Type Data
Cell Edge User Throughput (kbps 1024 512Number of PRBs per User 87 40
Channel ModelEnhanced Pedestrian A 5 Hz Antenna Configuration 4Tx-4Rx 1Tx-4Rx
Required SINR at Cell Edge (dB) -0.89 -5.29Maximum SINR at Cell Edge (dB) -0.03 -
Cell Load (%) 30% 30%Interference Margin [Formula/Simulation] (dB) 1.23 1.00
Number of Received Subcarriers (dB) 30.8 26.8Thermal Noise Density (dBm/Hz) -174
Subcarrier Bandwidth (kHz) 15Noise Power per Subcarrier (dBm) -132.17
Receiver Sensitivity (dBm) -94.27 -107.65
Maximum Allowable Path Loss (dB)(c lu t ter not considered)
154.05 144.65
Link Budget Example
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Clutter Type High Dense Urban Dense Urban Urban Suburban Rural (open)Maximum Allowable Path Loss (dB)
(clutter not considered) 144.65
BTS Antenna Height (m) 20.0 20.0 20.0 22.0 24.0MS Antenna Height (m) 1.0 1.0 1.0 1.0 1.0
Average Penetration Loss (dB) 27.0 24.0 20.0 18.0 12.0Standard Deviation Outdoor (dB) 10.0 10.0 8.0 8.0 8.0
Cell Area Probability 95.0% 95.0% 95.0% 95.0% 95.0%Log Normal Fading Margin (dB) 11.5 11.5 8.6 8.6 8.6Gain Against Shadowing (dB) 3.3 3.3 2.4 2.4 2.4
Maximum Allowable Path Loss (dB)(clut ter con sidered)
109.41 112.41 118.46 120.48 126.46
Cell Range (km) 0.142 0.166 0.277 0.383 0.655
Cell Radius Comparison
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0.000.501.001.502.002.503.003.504.00
2600 FDD-LTE 2300 TDD - LTE 1800 FDD-LTE 750 FDD-LTE
Dense Urban Urban Sub Urban Rural
Clutter 2600 FDD-LTE 2300 TDD - LTE 1800 FDD-LTE 750 FDD-LTE Dense Urban 0.14 0.16 0.23 0.62
Urban 0.22 0.25 0.37 1.00
Sub Urban 0.40 0.43 0.58 1.88
Rural 0.82 0.89 1.33 3.49
Peak data rates LTE FDDDirectly linked to available spectrum bandwidth
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1.4 3 5 10 15 20
Peak data rate
[Mbps]
Downlink
Uplink
Bandwidth [MHz]
150
125
100
75
50
258.8 / 2.8
22.2 / 7.0
36.7 / 11.4
73.7 / 22.9
110.1 / 35.2
149.8 / 46.9100Mbpsservicerequires
2x15MHzbandwid th
Peak data ratesDriven by LTE terminal capabilities
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Class 1 Class 2 Class 5Class 3 Class 4
Peak rate DL/UL
RF bandwidth
Modulation DL
Modulation UL
Rx diversity
MIMO DL
10/5Mbps
50/25Mbps
100/50Mbps
150/50Mbps
300/75Mbps
20 MHz* 20 MHz* 20 MHz* 20 MHz* 20 MHz*
64 QAM 64 QAM 64 QAM 64 QAM 64 QAM
16 QAM 16 QAM 16 QAM 16 QAM 64 QAM
yes yes yes yes yes
optional 2 x 2 2 x 2 2 x 2 4 x 4
All LTE deviceswhich have beensold today
All 3GPP Rel.8 LTE terminals can receive 20 MHz bandwidth, but (baseband) processingpower is variable
LTE Radio Planning toolsThe recommended Radio Planning tools provided by 3rd Party are:
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Atoll from FORSK NetAct MultiRadio Planner (NAP) from AIRCOM Planet from MENTUM
Input Data for planning an LTE network
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General (technology independent) inputsDigital maps
Areas to be servedSite data if not green field case along with site limitationsPropagation model data
LTE specific partPower budgetUE and BTS Equipment details (NF, Link Adaptation etc.)Grade of Service Expected (e.g. location probability and maximum outage as% of customers)
Number of customersServices usedTraffic profiles
PCI PlanningIntroduction
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There are 504 unique Physical Cell IDs (PCI)Physical Layer Cell Identity = (3 N ID1) + N ID2
NID1: Physical Layer Cell Identity group. Range 0 to 167 Defines SSS sequence
NID2: Identity within the group. Range 0 to 2 Defines PSS sequence
Resource elementallocation to theReference Signal
PCI impacts the allocation ofresource elements to thereference signal and the setof physical channels
Allocation pattern repeats every 6 th Physical Layer Cell Identity
PCI PlanningRecommendations
Id = 6Id = 0
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In priority order (All four should be fulfilled, ideally)1. Avoid assigning the same PCI to neighbour
cells2. Avoid assigning mod 3 PCI to neighbour
cells3. Avoid assigning mod 6 PCI to neighbour
cells
4. Avoid assigning mod 30 PCI to neighbourcells
PCI is also used to calculate the PCFICH offset A term of the calculation is: 'pyhCellId
modulo {2 * (number of PRBs in DL)}
PCI of neighbour cells should have differentPCI modulo {2 * (number of PRBs in DL)} toavoid the same frequency (location) of thePCFICH
Id = 5
Id = 4
Id = 3Id =11
Id =10
Id = 9
Id = 8
Id = 7
Id = 2
Id = 1
Example 1 PCI Identity Plan
Example 2 PCI Identity Plan
Trusted solutionby top telecom
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y poperators