module 1 - lte basic principle
DESCRIPTION
Module 1 - Lte Basic PrincipleTRANSCRIPT
PowerPoint Presentation
LTE BASIC PRINCIPLE (1)
PT Nexwave Indonesia
Introduce about the background and network architecture of LTE
Introduce the basic principle of LTE Physical Layer and Layer 2
Introduce the key technology of LTE air interface
TARGET
Chapter 1:
LTE Protocol and Network Architecture Introduction
Chapter 2:
OFDM & SCFDM Introduction
Chapter 3:
LTE Physical Layer Introduction
Chapter 4:
LTE Layer 2 Structure Introduction
Chapter 5:
LTE Key Technology Introduction
CONTENT
Mobile Communication Evolution
1G: analog, 2G forward: digital
Communication improved in data rate, because bandwidth needed for voice communication is fixed
4
What is LTE?
LTE (Long Term Evolution) is known as a evolution of radio access technology conducted by 3GPP
What is main LTE Requirements?
High Data Peak Rate (with 20MHz bandwidth): 100Mbps (DL) and 50Mbps (UL)
Reduced latency: short time delay < 100ms (control plane), < 5ms (user plane)
Mobility and Security (2): optimized for low speed user (0-15 km/h) but also provide data rate 100kbps for high speed mobile user (up to 350 km/h)
Flexible bandwidth (1): 1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz, and 20MHz.
Improved Spectrum Efficiency: Capacity 2-4 times higher than HSPA rel.6
Packet Switched Optimized, no more CS domain, CS service is implemented in PS domain (VoIP)
Operation in FDD and TDD modes
Inter-working System Support with other existing network: GSM/HSPA/CDMA
LTE BACKGROUND
[2Note: 3GPP TS36.104 specifies values of 1.4, 3, 5, 10, 15 and 20 MHz. Probably early numbers in TS25.913 based on WCDMA (5MHz multiples)]
[1Note: Low mobile speed: 0-15km/h; high performance for mobile speeds between 15-120km/h. Support of mobility up to 350km/h (or 500km/h depending on the frequency band)]
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New radio transmission schemes:
OFDMA in downlink
SC-FDMA in uplink
MIMO, Multiple Antenna Technology
New radio protocol architecture:
Complexity reduction
Focus on shared channel operation, no dedicated channels anymore
New network architecture: Flat architecture (no RNC)
More functionality in the base station (eNodeB)
Focus on packet switched domain
Important for Radio Planning:
Frequency Reuse = 1
No need for Frequency Planning
Importance of interference control
No need to define neighbor lists in LTE
LTE requires Physical Layer Cell Identity planning (504 physical layer cell IDs organized into 168 groups of 3)
Additional areas need to be planned like PRACH parameters, PUCCH and PDCCH capacity and UL Demodulation Reference Signal
What is new in LTE?
LTE Release
LTE System Architecture
SAE: System Architecture Evolution (old naming), EPS: Evolved Packet System (new naming), LTE: E-UTRAN
HSS: Home subscriber server (part of IMS)
IMS: (IP multimedia system): architectural framework for delivering IP multimedia services. It was originally designed by 3GPP, as a part of the vision for evolving mobile networks beyond GSM.
Flexi NS: Flexi Network Server: MME, Flexi NG: Flexi Network Gateway: SGW + PDN GW
S5: It provides user plane tunnelling and tunnel management between Serving GW and PDN GW. It is used for Serving GW relocation due to UE mobility and if the Serving GW needs to connect to a non-collocated PDN GW for the required PDN connectivity.
S8: Inter-PLMN reference point providing user and control plane between the Serving GW in the VPLMN (V: visiting->roaming) and the PDN GW in the HPLMN. S8 is the inter PLMN variant of S5.
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LTE System Architecture
Main Network Element of LTE
The e-UTRAN consist of e-NodeBs, providing the user plane and control plane
The EPC consist of MME, S-GW, and P-GW
Network Interface of LTE
The e-NodeBs are interconnected with each other by means of the X2 interface, which enabling direct transmission data and signaling
S1 is interface between e-NodeBs and EPC, more specifically to the MME via the S1 MME and S-GW via the S1-U
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LTE eNodeB Functions
LTE EPC Network Elements
LTE EPC Network Elements
LTE Radio Interface & X2 Interface
UDP: User Datagram Protocol (L4 Transport Layer). Similar to TCP but only provides connectionless service.
SCTP: Transport Layer Protocol serving in a similar role as the popular protocols TCP and UDP. It provides some of the same service features of both, ensuring reliable, in-sequence transport of messages with congestion control.
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S1-MME & S1-U Interfaces
SCTP: Stream Control Transmission Protocol. For IP signalling. Ensures reliable, in-sequence transport of messages with congestion control Similar to TCP but with advantages:
- Multi-homing support, where one (or both) endpoints of a connection can consist of more than one IP address, enabling transparent fail-over between redundant network paths.
- Transaction-oriented, it transports data in one or more messages instead of in byte streams (TCP)
GTP: GPRS Tunnelling Protocol (same as for UMTS Rel 99): user plane traffic
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LTE Architecture with other system
LTE provide new high-speed data service, up to _Mbps in DL and _Mbps in UL
100Mbps DL and 50Mbps UL
LTE provides Spectrum Refarming thanks to?
Thanks to LTE Bandwidth scalability
LTE bandwidth scalability from _MHz, _MHz, _MHz, _MHz, _MHz and _MHz
1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz, 20MHz
New modulation scheme in LTE, which is ___ in DL and ___in UL
OFDMA in DL and SC-FDMA in UL
LTE using new Flat Architecture, what the meaning of this?
Without controller (RNC)
What is the frequency reuse pattern that LTE using?
Frequency Reuse of 1
LTE base station called eNodeB, what are it main functions?
Radio Resource Management (RRM), Dynamic Resource Allocation (Scheduler), Radio Admission Control, Radio Bearer Control, Connection Mgt. Control, etc
Interface between eNodeBs is called
X2
Interface between eNodeB and MME is called
S1-MME
Interface between eNodeB and S-GW is called
S1-U
Overview Wrap-Up
Chapter 1:
LTE Protocol and Network Architecture Introduction
Chapter 2:
OFDM & SCFDM Introduction
Chapter 3:
LTE Physical Layer Introduction
Chapter 4:
LTE Layer 2 Structure Introduction
Chapter 5:
LTE Key Technology Introduction
CONTENT
Time
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3
3
1
4
5
2
3
5
4
3
Power
Frequency
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2
3
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5
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2
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1
TDMA
-Time Division
Multiple Access-
2G e.g. GSM, PDC
FDMA
-Frequency Division
Multiple Access-
1G e.g. AMPS,
NMT, TACS
CDMA
-Code Division
Multiple Access-
3G e.g. UMTS, CDMA2000
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2
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UE 1
UE 2
UE 3
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UE 4
UE 5
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4
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OFDMA
-Orthogonal Frequency Division
Multiple Access-
e.g. LTE
FDMA, TDMA, CDMA, OFDMA
multiple access methodallows severalusersconnected to the same multi-pointtransmission mediumto transmit over it and to share its capacity
OFDM: Orthogonal Frequency Division Multiplexing, is a modulation multiplexing technology, divides system bandwidth into orthogonal subcarriers. CP (cyclic prefix) is inserted between OFDM symbols to avoid ISI (Inter Symbol Interference)
OFDMA is the combination of TDMA and FDMA essentially
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Transmits hundreds or even thousands of separately modulated radio signals using orthogonal subcarriers spread across a wideband channel
OFDMA BASIC
Data is sent in parallel across the set of subcarriers, each subcarrier only transports a part of the whole transmission
The throughput is the sum of the data rates of each individual (or used) subcarriers while the power is distributed to all subcarriers
FFT (Fast Fourier Transform) is used to create the orthogonal subcarriers. The number of subcarriers is determined by the FFT size (by the bandwidth)
In LTE, these subcarriers are separated 15kHZ
OFDMA BASIC
OFDM and Multipath
Cyclic Prefix (CP) and Guard Time
Subcarrier types
OFDMA Parameters
OFDMA Parameters
Fixed 15kHz: reduces the complexity of a system supporting multiple channel bandwidths
MBMS: Multimedia Broadcast Multicast system
To ensure that all signals are received correctly, the receiver sampling rate must be slightly higher than the bandwidth of the signal used to carry it (i.e. for a channel bandwidth of 1.75MHz the sampling rate should be 2 MHz)
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Peak-to-Average Power Ratio in OFDMA
SC-FDMA in UL
SC-FDMA and OFDMA Comparison (1/2)
SC-FDMA and OFDMA Comparison (2/2)
OFDMA and SC-FDMA vs. CDMA
Chapter 1:
LTE Protocol and Network Architecture Introduction
Chapter 2:
OFDM & SCFDM Introduction
Chapter 3:
LTE Physical Layer Introduction
Chapter 4:
LTE Layer 2 Structure Introduction
Chapter 5:
LTE Key Technology Introduction
CONTENT
It provides the basic bit transmission functionality over air
LTE physical layer based on OFDMA downlink and SC-FDMA in uplink direction
This is the same for both FDD and TDD mode of operation
No need of RNC like functional element
Everything radio related can be terminated in the eNodeB
System is reuse 1, single frequency network operation is feasible
No frequency planning required
There are no dedicated physical channels anymore, as all resource mapping is dynamically driven by the scheduler
Introduction
Frequency Band of LTE
LTE Physical Layer Domain
Frequency Domain
Time Domain
Resource Block
RB: Resource Blocks, consist of 7 OFDM symbols (15 KHz) and 12 subcarriers
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Type 1, applicable for FDD mode
Divided into 20 x 0.5ms slots
Frame duration = 10ms (same as UMTS)
FDD = 10ms radio frame for UL and 10ms radio frame for DL
Radio frame includes 10 subframes
1 Subframe represents a Transmission Time Interval (TTI)
Each subframes includes two slots
1 slot = 7 (normal CP) or 6 symbols (extended CP)
Radio Frame Structure (FDD)
Type 2, applicable for TDD mode
Applies OFDM, same subcarriers spacing and time unit with FDD
Similar with FDD, radio frames divided into 20 x 0.5ms slots = 10ms
The Uplink-Downlink configuration shown at table.
Radio Frame Structure (2)
Special SubFrame Structure
Normal and Extended Cyclic Prefix
LTE consist of time domain and frequency domain resources. The minimum unit for schedule is RB (Resource Block), which compose of RE (Resource Element)
One RB is consist of 1 slot period in time domain (0.5ms) and 12 subcarriers in frequency domain (180KHz)
Resource Block
Capacity allocation is based on Resource Blocks
Note:
Although 3GPP definition of RB refers to 0.5ms, in some cases it is possible to found that RB refers to 12 subcarriers in frequency domain and 1ms in time domain. In particular, since the scheduler in the eNodeB works on TTI basis (1ms) RBs are considered to last 1ms in time domain. They can also be known as scheduling resource blocks
Resource Element
Downlink Physical Signals and Channels
DL Physical Channels
MIB sent approx. every 40ms
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Uplink Physical Signals and Channels
UL Physical Channels
LTE allows orthogonal subcarrier in its transmission, what the meaning of this?
The peak (center of frequency) of one of subcarrier not intercepts with another peak of subcarrier (the peak only intercepts with the null part)
For overcome ISI (Inter Symbol Interference) effect, what method LTE used??
CP (Cyclic Prefix) / Guard Period that consist in copying the last signal shape of the message on duration of Guard Period
Why theres a differences in DL and UL multiple access scheme of LTE?
Due to large number of subscribers, OFDMA (DL) have a large range of PAPR and this requires a large range of power levels. So, it's not suitable for battery-powered devices (mobile phones). While SC-FDMA (UL) can reduce PAPR between 6-9dB compared to OFDMA.
What is the duration of these LTE parameters: one slot, one TTI, one sub-frame, one radio frame?
One slot = 0.5ms, TTI = sub-frame = 1ms, one radio frame = 10ms
One Resource Block (RB) LTE consist of?
One time slot duration (0.5ms) in time domain and 12 sub-carriers in frequency domain
Overview Wrap-Up
Chapter 1:
LTE Protocol and Network Architecture Introduction
Chapter 2:
OFDM & SCFDM Introduction
Chapter 3:
LTE Physical Layer Introduction
Chapter 4:
LTE Layer 2 Structure Introduction
Chapter 5:
LTE Key Technology Introduction
CONTENT
LTE Layer-2 Overview
LTE MAC Layer Overview
LTE RLC Layer Overview
LTE PDCP Layer Overview
Chapter 1:
LTE Protocol and Network Architecture Introduction
Chapter 2:
OFDM & SCFDM Introduction
Chapter 3:
LTE Physical Layer Introduction
Chapter 4:
LTE Layer 2 Structure Introduction
Chapter 5:
LTE Key Technology Introduction
CONTENT
SON (Self Organizing Networks)
Main Functionalities of SON
ANR (Automatic Neighbour Relation)
ANR (Automatic Neighbour Relation)
MIMO
DL MIMO
UL MIMO
Cell Interference Control
Adaptive Modulation and Coding
Schedule & Link Auto-Adaptation
CSFB
LTE BASIC PRINCIPLE (2)
PT Nexwave Indonesia
Chapter 1: Connection States Overview
Chapter 2: LTE Radio Procedure Overview
Chapter 3: Mobility Management Overview
CONTENT
Mobility and Connection States (1/2)
Mobility and Connection States (2/2)
ECM-IDLE:
The location of the UE is known to within the accuracy of a tracking area
Mobility is managed by tracking area updates.
ECM-CONNECTED:
In this state there is a signaling connection between the UE and the MME which is provided in the form of a Radio Resource Control (RRC) connection between the UE and the E-UTRAN and an S1 connection for the UE between the E-UTRAN and the MME.
The location of the UE is known to within the accuracy of a cell.
Mobility is managed by handovers.
RRC_IDLE:
No signalling connection between the UE and the E-UTRAN.
I.e.: PLMN Selection.
UE Receives system information and listens for Paging.
Mobility based on Cell Re-selection performed by UE.
No RRC context stored in the eNB.
RACH procedure used on RRC connection establishment.
RRC_CONNECTED:
UE has an E-UTRAN RRC connection.
UE has context in E-UTRAN (C-RNTI allocated).
E-UTRAN knows the cell which the UE belongs to.
Network can transmit and/or receive data to/from UE.
Mobility based on handovers
UE reports neighbour cell measurements.
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LTE Radio Resource Control (RRC) States
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EMM & ECM States Transitions
C-RNTI: Cell Radio Network Temporary Identifier. Uniquely identifies a UE within a cell. Only exists if UE is connected. Assigned by the eNodeB.
S-TMSI: SAE- Temporary Mobile Subscriber Identifier: uniquely identifies the UE within a tracking area. Assigned by the MME.
TA Update: Tracking Area Update
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EMM & ECM States Summary
RRC States
CCO: cell change order
The LTE to GSM Network Assisted Cell Change (NACC) allows for a service continuity of data services when changing from a LTE cell to a GSM cell.
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Chapter 1: Connection States Overview
Chapter 2: LTE Radio Procedure Overview
Chapter 3: Mobility Management Overview
CONTENT
LTE Initial Procedure (1)
The initial Procedure including scanning for downlink and uplink channels and synchronization which is broadcasting from eNodeB within E-UTRAN (MIB & BCCH System Information)
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LTE Initial Procedure (2)
Cell Search (1)
Cell Search (2)
RACH Procedure
Chapter 1: Connection States Overview
Chapter 2: LTE Radio Procedure Overview
Chapter 3: Mobility Management Overview
CONTENT
LTE Handover Principles
Purpose of Handover
Handover Types
Handover Procedure (1)
Handover Procedure (2)
Handover Preparation
Handover Execution
Handover Completion
Neighbour list Generation in LTE
3GPP ANR configuration principle
Measurements Event (1)
Measurements Event (2)
Handover Procedure over X2
Handover Procedure over S1 (1)
Handover Procedure over S1 (2)
Thank You
LTE Frequency
Band