4G Long Term Evolution Introduction_18-Jan-2014

where LTE will lead, we know not; but we can be sure that it will not be the last development in wireless telegraphy Guglielmo Marconi

[1] LTE/SAE INTRODUCTION

EVOLUTION OF MOBILE COMMUNICATION NETWORKS

3GPP RELEASES & LTE TERMINOLOGY

LTE DRIVERS

FREQUENCY BANDS

LTE-ADVANCED (LTE-A)

[2] EVOLVED PACKET SYSTEM (EPS) ARCHITECTURE & PROTOCOLS

OVERVIEW EPS ARCHITECTURE

EPS FUNCTIONALITY

LTE PROTOCOL STACK

LTE UE STATES AND AREA CONCEPTS

[3] LTE AIR INTERFACE

OFDMA/SC-FDMA BASICS

LTE FRAME & CHANNEL STRUCTURE

LTE DOWNLINK & UPLINK PHYSICAL CHANNEL

[4] LTE KEY TECHNOLOGY INTRODUCTION

MULTIPLE INPUT MULTIPLE OUTPUT (MIMO)

CSFB (CIRCUIT SWITCHED FALLBACK )

SON (SELF ORGANIZING NETWORKS)

18-Jan-2014 2 Free Print and Non-Commercial Publishing

Contents

[1] LTE/SAE INTRODUCTION



1st Generation or 1G 2nd Generation or 2G , 2nd Generation Transitional or 2.5G,2.75G 3rd Generation or 3G , 3rd Generation Transitional or 3.5G,3.75G,3.9G 4th Generation or 4G

Evolution of Mobile Communication Networks


LTE Parallel Evolution Path to HSPA+


3GPP RELEASES & LTE TERMINOLOGY

Long Term Evolution (LTE) and System Architecture

Evolution (SAE) are specified by the Third Generation

Partnership Project (3GPP) in Release 8 specifications.

The standard development in 3GPP is grouped into two

work items, where LTE targets the radio network evolution

and System Architecture Evolution (SAE) targets the

evolution of the packet core network.

Long Term Evolution (LTE) : Evolution of 3GPP UMTS Terrestrail Radion Access (E-UTRA) Technology.

Evolved Packet System (EPS) : Evolution of the complete 3GPP UMTS Radio Access, Packet Core and its integration

into legacy 3GPP/non-3GPP network.

EPS includes:

Evolved UTRAN (eUTRAN) Radio Access Network Evolved Packet Core (EPC) System Architecture.

A detailed description of SAE/LTE Specifications are available at

the 3GPP website: http://www.3gpp.org/ftp/Specs/archive/


E-UTRA Design Performance Targets

Scalable transmission bandwidth(up to 20 MHz) Improved Spectrum Efficiency

Downlink (DL) spectrum efficiency should be 2-4 times Release 6 HSDPA. Downlink target assumes 2x2 MIMO for E-UTRA and single Txantenna with Type 1 receiver HSDPA. Uplink (UL) spectrum efficiency should be 2-3 times Release 6 HSUPA. Uplink target assumes 1 Tx antenna and 2 Rx antennas for both E-UTRA and Release 6 HSUPA.

Coverage Good performance up to 5 km Slight degradation from 5 km to 30 km (up to 100 km not precluded)

Mobility Optimized for low mobile speed (< 15 km/h) Maintained mobility support up to 350 km/h (possibly up to 500 km/h)

Advanced transmission schemes, multiple-antenna technologies Inter-working with existing 3G and non-3GPP systems

Interruption time of real-time or non-real-time service handover between E-UTRAN and UTRAN/GERAN shall be less than 300 or 500 ms.


E-UTRA Air Interface Capabilities

Bandwidth support Flexible from 1.4 MHz to 20 MHz

Waveform OFDM in Downlink SC-FDM in Uplink

Duplexingmode FDD: full-duplex (FD) and half-duplex (HD) TDD

Modulation orders for data channels Downlink: QPSK, 16-QAM, 64-QAM Uplink: QPSK, 16-QAM, 64-QAM

MIMO support Downlink: SU-MIMO and MU-MIMO (SDMA) Uplink: SDMA

Single & same link of communication for DL & UL

DL serving cell = UL serving cell No UL or DL macro-diversity

UEs Active Set size = 1

Hard-HO based mobility UE assisted (based on measurement reports) and network controlled (handover decision at specific

time) by default.

During a handover, UE uses a RACH based mobility procedure to access the target cell

Handover is UE initiated if it detects a RL failure condition.

Load indicator for inter-cell load control (interference management)

Transmitted over X2 interface

UE e-NB Communication Link E-UTRA Air Interface Capabilities


LTE DRIVERS

Branding

Marketing

Technical

For branding image

For competition

For better data service

For SME & Industry user

For frequency issue

For network quality


LTE DRIVERS

Ericsson Mobility Report November 2013


LTE DRIVERS


LTE DRIVERS

LTE operation benefits

Enhanced

experience for

E2E quality

Spectrum

flexibility

Lower cost

Higher speed (x10)

Lower latency (1/4 )

Lager capacity (x3)

New or re-farmed spectrum

Varity channel bandwidth

IP based flat network architecture

Low OPEX: SON

High re-use of asset

Flat Overall Architecture

2-nodes architechture IP routable transport architechture Lower cost.

Improved Radio Aspects

Peak data rates [Mbps] DL=300,UL=75 Scalable Bandwidth:1.4,3,5,10,15,20 MHz Short latency:


Achievable & Supported Peak Data Rates

Achievable LTE Peak Data Rate

Peak Data rate scale with the bandwidth

2x2 MIMO supported for the initial LTE deployment.

UE Supported Peak Data Rate (Mbps)

Similar peak data rates defined for FDD & TDD. All categories support 20 MHz, 64QAM downlink and receive antenna diversity.

Category 2,3 ,4 expected in the first phase with bit rates up to 150 Mbps.


Frequency Band of LTE

TDD Frequency Band

FDD Frequency Band From LTE Protocol:

Duplex mode: FDD and TDD

Support frequency band form 700MHz to 2.6GHz

Support various bandwidth: 1.4MHz, 3MHz,

5MHz, 10MHz, 15MHz, 20MHz.

E-UTRA

Band

Uplink (UL) Downlink (DL) Duplex

ModeFUL_low FUL_high FDL_low FDL_high

1 1920 MHz 1980 MHz 2110 MHz 2170 MHz FDD




5 824 MHz 849 MHz 869 MHz 894MHz FDD




9 1749.9 MHz

1784.9 MHz 1844.9 MHz

1879.9 MHzFDD


111427.9 MHz 1452.9 MHz 1475.9 MHz 1500.9 MHz FDD





...

E-UTRA

Band

Uplink (UL) Downlink (DL) Duplex

ModeFUL_low FUL_high FDL_low FDL_high

33 1900 MHz 1920 MHz 1900 MHz 1920 MHz TDD









Frequency Band of LTE Release 8


FREQUENCY BANDS


EARFCN (E-Absolute Radio Frequency Channel Numnber)

eNB

UE

FDL = FDL_low + 0.1(NDL - NOffs-DL)

FUL = FUL_low + 0.1(NUL - NOffs-UL)

Frequency

Uplink Downlink

100kHz Raster

2127.4MHz1937.4MHz

FDL = FDL_low + 0.1(NDL - NOffs-DL)

(FDL - FDL_low)

0.1+ NOffs-DL

(2127.4 - 2110)

0.1+ 0

NDL =

NDL = = 174


LTE EVOLUTION (LTE-Advanced)

LTE-Advanced (LTE-A) is introduced in 3GPP release10 and its the Global 4G solution. Improves spectrum efficiency, delivers increases in capacity and coverage, and the ability to support more customers /devices more efficiently, to maintain and improve the user experience of mobile broadband.

Increased data rates and lower latencies for all users in the cell. Data rates scale with bandwidthUp to 1 Gbps peak data rate.

Aggregating 40 MHz to 100 MHz provide peak data rates of 300 Mbps to 750 Mbps1(2x2 MIMO) and over 1 Gbps(4x4 MIMO)

Multicarrier Enables Flexible Spectrum Deployments [Key features] Carrier Aggregation Higher order MIMO SON/Hetnets Interference management Relays


LTE EVOLUTION (LTE-A)

LTE-A introduces higher order MIMO 8x8 DL MIMO, 4x4 UL MIMO and UL Beamforming

More Antennas to

Leverage Diversity

[2] EVOLVED PACKET SYSTEM (EPS)

ARCHITECTURE & PROTOCOLS



System Architecture Evolution (SAE)

EPS is all PS (IP based no CS domain )

[Main drivers] All-IP based Reduce network cost Reduce data latency & signalling load

Better network topology scalability & reliability

Inter-working & seamless mobility among heterogeneous

access networks(3GPP & non-

3GPP).

Better always-on user experience

Simpler and more flexible Qos Suppport

Higher level of security


PS Domain Architecture Evolution

EPS flat architecture, with User Plane direct tunneling between SAE-GW and eNode B is similar to the super flat architecture option for HSPA+, where GGSN connects directly to a collapsed RNC+Node B entity or to an evolved Node B. As the color legend

shows, the location of the migrated network functions in EPS are as follows:

RNC functions are in eNB & MME

SGSN functions are in the MME

GGSN functions are in SGW & PGW


Overall EPS Architecture

Main Network Element of EPS (Evolved Packet System)

E-UTRAN (Evolved UTRAN ) consists of e-NodeBs, providing the user plane and control plane.

EPC (Evolved Packet Core ) consists of MME, S-GW and P-GW.

Network Interface of EPC (Evolved Packet System)

e-NodeBs are interconnected with each other by means of the X2 interface, enabling direct transmission of data and signaling.

S1 is the interface between e-NodeBs and the EPC, to the MME via the S1-MME and to S-GW via the S1-U.

EPC includes; MME (Mobility Management Entity) handling Control Plane.

S-GW (Serving Gateway) & P-GW (PDN Gateway) handling User Plane

Note:

HSS (Home Subscriber Server) is formally out of the EPC, and will need to be updated with new EPS

subscription data and functions.

PCRF and Gx/Rx provide QoS Policy and Charging control (PCC),

similarly to the UMTS PS domain.


E-UTRAN Entities/Interfaces Evolved Node B (eNB) provides the E-UTRA User Plane (PDCP/RLC/MAC/PHY) and Control Plane (RRC) protocol terminations toward

the UE. An eNB can support FDD mode, TDD mode, or dual mode operation. eNBs can optionally be interconnected with each

other by means of the X2 interface or connected by means of the S1 interface to the Evolved Packet Core (EPC).

e-Node hosts the following functions:

Radio Resource Management: Radio Bearer Control,

Radio Admission Control, Connection Mobility Control,

Dynamic allocation of resources to UEs in both uplink and

downlink (scheduling)

IP header compression

Encryption /Integrity protection of user data

MME selection (among MME pool)

Routing of User Plane data towards S-GW

Scheduling and transmission of paging and broadcast

messages (originated from the MME)

Measurement and measurement reporting configuration

for mobility and scheduling

S1 interface

Can be split S1-U (S-GW) & S1-C(MME).

X2 interface

Used for inter-eNB handover, load balacing and

interference cancellation.


EPC Entities/Interfaces

S-GW (Serving Gateway) main functions:

Packet routing and forwarding

E-UTRAN and inter-3GPP mobility anchoring

E-UTRAN Idle mode DL packet buffering

UL and DL charging per UE, PDN, and QCI

Transport level QoS mapping

P-GW (PDN Gateway) main functions:

Per-user based packet filtering UE IP address allocation UL and DL service level charging User Plane anchoring for 3GPP and non-3GPP mobility

MME (Mobility Management Entity) main functions:

NAS signaling and security

AS Security control

Idle state mobility handling

P-GW and S-GW selection

EPS (Evolved Packet System) bearer control;

Support paging, handover, roaming and authentication

S10 interface

Support mobility between MMEs

S11 interface

Support EPS Bearer management between MME & S-GW

S6a interface

Used for subscription & security control between MME&HSS

S5 interface

Between S-GW and P-GW

Called S8 for Inter-PLMN connection (roaming)


LTE Radio Protocol Stack

Two Planes in LTE Radio Protocol: (1) User-plane: For user data transfer (2) Control-plane: For system signaling transfer

Over LTE-Uu radio interface, protocols are split in: (AS) Access Stratum: RRC/PDCP/RLC/MAC/PHY. (NAS) Non Access Stratum: EMM (Mobility Management) and ESM (Session Management)

Control plane

Over S1 and X2 interfaces, two RNL application protocols (S1-AP and X2-

AP), using a new transport protocol called SCTP (Stream Control

Transmission Protocol).

S1-AP: Supports all necessary EMM-eNB signaling and procedures, including RAB management, mobility, paging, NAS transport, and many

other S1 related functions.

X2-AP: Supports Intra LTE-Access-System Mobility, Uplink Load Management, and X2 error handling functions.

Main Functions of Control-plane:

RLC and MAC layers perform the same functions as for the user plane

PDCP layer performs ciphering and integrity protection

RRC layer performs broadcast, paging, connection management, RB control, mobility functions, UE measurement reporting and control

NAS layer performs EPS bearer management, authentication, security control


LTE Radio Protocol Stack

User plane on the S1-U uses GTP-U for

tunneling. The same protocol stack

would apply to the X2 interface, for

data packet forwarding during handover

between eNBs.

The concatenation of LTE RB + S1 Bearer

+ S5 Bearer makes the EPS Bearer,

which can be shared by multiple Service

Flows with the same level of QoS.

EPS Bearer (similar to a PDP context of

previous 3GPP releases) is defined between

the User Equipment (UE) and the P-GW

node in the EPC (which provide the end

users IP point of presence towards

external networks).

User-plane


LTE Radio Interface structure

The radio interface is structured in a layered

model, similar to WCDMA, with a layer 2

bearer (here called EPS Bearer Service),

which corresponds to a PDP-context in Rel. 6,

carrying layer 3 data and the end-to-end

service.

The EPS bearer is carried by the E-UTRA

Radio Bearer Service in the radio interface. The

E-UTRA radio bearer is carried by the radio

channels.

The radio channel structure is divided into

logical, transport and physical channels.


LTE UE STATES AND AREA CONCEPTS

LTE is developed to have a simpler

architecture (fewer nodes) and

less signaling (fewer messages) than

the UTRAN. The number of states

which the UE can be in (corresponding

to RRC states) are reduced from five in

the UTRAN (DETACHED, IDLE,

URA_PCH, CELL_FACH, CELL_DCH)

to only three in the eUTRAN

(DETACHED, IDLE and CONNECTED)

In LTE only one area for idle mode

mobility is defined; the Tracking Area

(TA). In UTRAN, Routing Area (RA) and

UTRAN Registration Area (URA) is

defined for PS traffic and

Location Area (LA) for CS traffic.

In ECM-IDLE (EPS Connection

Management IDLE) the UE position is

only known by the network on TA level,

whereas in ECM-CONNECTED, the UE

location is known on cell level by the

eNodeB.

[3] LTE AIR INTERFACE



Duplex Techology

Frequency Division Duplex (FDD):

Distinguish uplink and downlink according to frequencies.

Time division duplex (TDD):

Distinguish uplink and downlink according to timeslots.


Multiple Access Technology


OFDM Basics

LTE radio interface is based on OFDM (Orthogonal Frequency Division Multiplex) and OFDMA (Orthogonal Frequency Division

Multiple Access) in DL and SC-FDMA (Single Carrier Frequency Division Multiple Access) in UL.

OFDM uses a large number of closely spaced narrowband carriers.In a conventional FDM system, the frequency spacing between

carriers is chosen with a sufficient guard band to ensure that interference is minimized and can be cost effectively filtered. In OFDM,

however, the carriers are packed much closer together.

OFDM Orthogonality

Each of the 15 kHz LTE air interface subcarriers are Orthogonal to each other , there is zero inter-carrier interference at the center frequency of each

subcarrier. Orthogonality allows simultaneous transmission on many

subcarriers in a tight frequency space without interference from each other.

The spectrums of the subcarriers are not separated, but overlap.


OFDM Basics

The transmitter combines all the subcarriers using an Inverse Fast Furrier Transform (IFFT) function where the outcome is single

signal which is basically a sum of sinusoids having an amplitude that varies depending on the number of subcarriers. The receiver

uses a Fast Fourier Transform (FFT) function to recover each subcarrier.

OFDM also shows very good performance in highly

time dispersive radio environments (i.e. many

delayed and strong multipath reflections).

That is because the data stream is distributed over

many subcarriers. Each subcarrier will thus have a

slow symbol rate and correspondingly, a long

symbol time. This means that the Inter Symbol

Interference (ISI) is reduced.

Sub-carriersFFT

Time

Symbols

System Bandwidth

Guard

Intervals

Frequency

Sub-carriersFFT

Time

Symbols

System Bandwidth

Guard

Intervals

Frequency

FFT = Fast Fourier Transform, IFFT = Inverse FFT FFT/IFFT allows to move between time and frequency domain representation


OFDM & SC-FDMA

OFDM & OFDMA

OFDM (Orthogonal Frequency Division Multiplexing) is a modulation multiplexing technology, divides the system

bandwidth into orthogonal subcarriers.

OFDMA is the multi-access technology related with OFDM, is used in the LTE downlink. OFDMA is the

combination of TDMA and FDMA essentially.

Advantage: High spectrum utilization efficiency due to orthogonal subcarriers need no protect bandwidth.

Support frequency link auto adaptation and scheduling.

Easy to combine with MIMO.

Disadvantage: Strict requirement of time-frequency domain synchronization. High Peak-to-Average Power

Ratio (PAPR).

DFT-S-OFDM & SC-FDMA

DFT-S-OFDM (Discrete Fourier Transform Spread OFDM) is the modulation multiplexing technology

used in the LTE uplink, Each user is assigned part of

the system bandwidth.

SC-FDMASingle Carrier Frequency Division Multiple Accessingis the multi-access technology related with DFT-S-OFDM.

Advantage: High spectrum utilization efficiency due to orthogonal user bandwidth need no protect

bandwidth.

Low Peak-to-Average Power Ratio (PAPR)

User 1

User 2

User 3

Sub-carriers

TTI: 1ms

Frequency

System Bandwidth

Sub-band12Sub-carriersTime

User 1

User 2

User 3

User 1

User 2

User 3

Sub-carriers

TTI: 1ms

Frequency

System Bandwidth

Sub-band12Sub-carriersTime

Sub-carriers

TTI: 1ms

Frequency

Time

System Bandwidth

Sub-band12Sub-carriers

User 1

User 2

User 3

Sub-carriers

TTI: 1ms

Frequency

Time

System Bandwidth

Sub-band12Sub-carriers

User 1

User 2

User 3

User 1

User 2

User 3

SC-FDMA : PRBs are grouped to bring down PAPR , better power efficiency at the UE


Time & Frequency Domain Organization

LTE Time Domain is organized as

Frame (10 ms) Sub-frame (1ms) Slot (0.5ms) Symbol (duration depends on configuration)

Radio Frame Structures Supported by LTE:

Type 1, applicable to FDD

Type 2, applicable to TDD

LTE Frequency Domain LTE DL/UL air interface waveforms use a number of Orthogonal subcarriers to send users & control data.

Pre-defined spacing between these subcarriers (15 KHz for regular operation and 7.5 KHZ for MBSFN operation)

.

DC subcarrier which has no energy and is located at the center of the frequency band.

Two guard bands at the edges of the OFDM/OFDMA-signal (no RF transmission in this subcarriers). This is a

guard band to avoid interference with adjacent bands.


Frequency Domain Configurations

Various channel bandwidths that may be considered for LTE deployment are shown in the table. One of the typical LTE deployment options (10 MHz) is highlighted.

Assuming 15 KHz Carrier Spacing


UL/DL Resource Grid Definitions

Resource Element (RE) One element in the time/frequency resource grid.

One subcarrier in one OFDM/LFDM symbol for DL/UL. Often used for Control channel resource assignment.

Resource Block (RB) Minimum scheduling size for DL/UL data channels Physical Resource Block (PRB) [180 kHz x 0.5 ms] Virtual Resource Block (VRB) [180 kHz x 0.5 ms in virtual frequency domain]

Localized VRB Distributed VRB

Resource Block Group (RBG) Group of Resource Blocks

Size of RBG depends


UL/DL Resource Grid Definitions

Resource Element Group (REG) Groups of Resource Elements to carry control information. 4 or 6 REs per REG depending on number of reference signals per symbol, cyclic prefix configuration.

REs used for DL Reference Signals (RS) are not considered for the REG.

Only 4 usable REs per REG.

Control Channel Element (CCE) Group of 9 REGs form a single CCE.

1 CCE = 36 REs usable for control information. Both REG and CCE are used to specify resources for LTE DL control channels.

Antenna Port One designated reference signal per antenna port. Set of antenna ports supported depends on reference signal configuration within cell.


TDD Radio Frame Structure Applies OFDM, same subcarriers spacing and time unit with FDD.

Similar frame structure with FDD. radio frame is 10ms shown as

below, divided into 20 slots which are 0.5ms.

The uplink-downlink configuration of 10ms frame are shown in

the right table.

Uplink-downlink Configurations

Special Subrame Structure

Special Subframe consists of DwPTS, GP and UpPTS .

9 types of Special subframe configuration.

Guard Period size determines the maximal cell radius. (100km)

DwPTS consists of at least 3 OFDM symbols, carrying RS, control message and data.

UpPTS consists of at least 1 OFDM symbol, carrying sounding RS or short RACH.

DL to UL switch point in special subframe #1 and #6 only Other subframes allocated to UL or DL Sum of DwPTS, GP and UpPTS always 1 ms Subframe #0 and #5 always DL - Used for cell search signals (S-SCH)

Uplink-

downlink

configuration

Downlink-to-Uplink

Switch-point

periodicity

Subframe number

0 1 2 3 4 5 6 7 8 9

0 5 ms D S U U U D S U U U

1 5 ms D S U U D D S U U D

2 5 ms D S U D D D S U D D

3 10 ms D S U U U D D D D D

4 10 ms D S U U D D D D D D

5 10 ms D S U D D D D D D D

6 5 ms D S U U U D S U U D


Cyclic Prefix (CP) Transmission

CP Length Configuration:

Cyclic Prefix is applied to eliminate ISI (Inter-symbol Interference) of OFDM.

CP length is related with coverage radius. Normal CP can fulfill the requirement of common

scenarios. Extended CP is for wide coverage scenario.

Longer CP, higher overheading.

Configuration DL OFDM CP Length UL SC-FDMA CP

Length

Sub-carrier of

each RB

Symbol of

each slot

Normal CP f=15kHz 160 for slot #0

144 for slot #1~#6

160 for slot #0

144 for slot #1~#6 12 7

Extended CP f=15kHz 512 for slot #0~#5 512 for slot #0~#5 6

f=7.5kHz 1024 for slot #0~#2 NULL 24 (DL only) 3 (DL only)

Slot structure under Normal

CP configuration

(f=15kHz)

Slot structure under Extended

CP configuration

(f=15kHz)

Slot structure under Extended

CP configuration

(f=7.5kHz)


Cyclic Prefix (CP) Transmission

Cyclic Prefix (CP) insertion helps maintain

orthogonality Reduces efficiency (or Usable

Symbol time, Tu) .

Mitigates Inter-Symbol Interference (ISI) Reduces efficiency

Useable time per symbol is Tu/(Tu+TCP) Selection of Cyclic Prefix governed by delay spread

In OFDM, multipath causes loss of orthogonality Delayed paths cause overlap between symbols


LTE Channel Structure



Logical Channel

Control Channel Broadcast Control Channel (BCCH) DL broadcast of system control information. Paging Control Channel (PCCH) DL paging information. UE position not known on cell level Common Control Channel (CCCH) UL/DL. When no RRC connection exists. Multicast Control Channel (MCCH) DL point-to-multipoint for MBMS scheduling and control, for one or several MTCHs.

Dedicated Control Channel (DCCH) UL/DL dedicated control information. Used by UEs having an RRC connection.

Traffic Channel

Dedicated Traffic Channel (DTCH) UL/DL Dedicated Traffic to one UE, user information. Multicast Traffic Channel (MTCH) DL point-to-multipoint. MBMS user data.

Transport Channel

DL Channel Broadcast Channel (BCH) System Information broadcasted in the entire coverage area of the cell.Beamforming is not applied. Downlink Shared Channel (DL-SCH) User data, control signaling and System Info. HARQ and link adaptation.Broadcast in the entire cell or beamforming. DRX and MBMS supported. Paging Channel (PCH) Paging Info broadcasted in the entire cell. DRX Multicast Channel (MCH) MBMS traffic broadcasted in entire cell. MBSFN is supported.

UL Channel Uplink Shared channel (UL-SCH) User data and control signaling. HARQ and link adaptation. Beamforming may be applied. Random Access Channel (RACH) Random Access transmissions (asynchronous and synchronous). The transmission is typically contention based. For UEs having an RRC connection there is some limited support for contention free access.



Physical channels Physical Downlink Shared Channel (PDSCH) transmission of the DL-SCH transport channel

Physical Uplink Shared Channel (PUSCH) transmission of the UL-SCH transport channel

Physical Control Format Indicator Channel (PCFICH) indicates the PDCCH format in DL

Physical Downlink Control Channel (PDCCH) DL L1/L2 control signaling

Physical Uplink Control Channel (PUCCH) UL L1/L2 control signaling

Physical Hybrid ARQ Indicator Channel (PHICH) DL HARQ info

Physical Broadcast Channel (PBCH) DL transmission of the BCH transport channel.

Physical Multicast Channel (PMCH) DL transmission of the MCH transport channel.

Physical Random Access Channel (PRACH) UL transmission of the random access preamble as given by the RACH transport channel.

Physical signals Reference Signals (RS) support measurements and coherent demodulation in uplink and downlink. Primary and Secondary Synchronization signals (P-SCH and S-SCH)

DL only and used in the cell search procedure. Sounding Reference Signal (SRS) supports UL scheduling measurements


Synchronization Signals (PSS & SSS)

PSS and SSS Functions Frequency and Time synchronization

Carrier frequency determination OFDM symbol/subframe/frame timing determination

Physical Layer Cell ID (PCI) determination Determine 1 out of 504 possibilities

PSS and SSS resource allocation Time: subframe0 and 5 of everyFrame Frequency: middle of bandwidth (6 RBs = 1.08 MHz)

Primary Synchronization Signals (PSS) Assists subframe timing determination Provides a unique Cell ID index (0, 1, or 2) withina Cell ID group

Secondary Synchronization Signals (SSS) Assists frame timing determination Provides a unique Cell ID group number among 168 possible Cell ID groups


Cell Identity Determination from PSS and SSS

Physical Cell Identity (PCI) is uniquely defined by: A number in the range of 0 to 167, representing the Physical Cell Identity (PCI) group

A number in the range of 0 to 2, representing the physical identity within the Physical Cell Identity (PCI) group

S-SCH Provides 168 sequences, each associated to a cell ID group information

These sequences are interleaved concatenations of two length-31 binary sequences

P-SCH Three (NID=0,1,2) frequency domain Zadoff-Chu sequences of length 62


Physical Broadcast Channel (PBCH)

PBCH Function Carries the primary Broadcast Transport Channel Carries the Master Information Block (MIB), which includes:

Overall DL transmission bandwidth PHICH configuration in the cell System Frame Number Number of transmit antennas (implicit)

Transmitted in Time: subframe 0 in every frame 4 OFDM symbols in the second slot of corresponding subframe Frequency: middle 1.08 MHz (6 RBs)

TTI = 40 ms Transmitted in 4 bursts at a very low data rate Same information is repeated in 4 subframes Every 10 ms burst is self-decodable CRC check uniquely determines the 40 ms PBCH TTI boundary

Last 2 bits of SFN is not transmitted


System Information in PBCH & PDSCH

The System Information (SI) that is broadcasted in the whole cell area, is carried by the logical channel BCCH, which in turn is

carried by either of the transport channels BCH or DL-SCH. A static part of SI is called MIB (Master Information Block) is

transmitted on the BCH, which in turn is carried by the PBCH. A dynamic part of SI, called SIBs (System Information Blocks) is

mapped onto RRC System Information messages (SI-1,2,3) on DL-SCH, which in turn is carried by PDSCH.


System Information (MIB & SIB)

MIB (Master Information Block) Repeats every 4 frames (40 ms) and includes DL Tx bandwidth, PHICH configuration, and SFN. This

information is necessary to acquire (read) other channels in the cell. ***( LTERelease 8 has 11 different SIB types)


Physical Control Format Indicator Channel (PCFICH)

Carries the Control Format Indicator (CFI) Signals the number of OFDM symbols of PDCCH:

1, 2, or 3 OFDM symbols for system bandwidth > 10 RBs 2, 3, or 4 OFDM symbols for system bandwidth > 6-10 RBs Control and data do not occur in same OFDM symbol

Transmitted in: Time: 1st OFDM symbol of all subframes Frequency: spanning the entire system band

4 REGs -> 16 REs Mapping depends on Cell ID

PCFICH in Multiple Antenna configuration 1 Tx: PCFICH is transmitted as is 2Tx, 4Tx: PCFICH transmission uses Alamouti Code


Physical Downlink Control Channel (PDCCH)

Used for: DL/UL resource assignments Multi-user Transmit Power Control (TPC) commands Paging indicators

CCEs are the building blocks for transmitting PDCCH 1 CCE = 9 REGs (36 REs) = 72 bits The control region consists of a set of CCEs, numbered from 0 to N_CCE for each subframe

The control region is confined to 3 or 4 (maximum) OFDM symbols per subframe (depending on system bandwidth)

A PDCCH is an aggregation of contiguous CCEs (1,2,4,8) Necessary for different PDCCH formats and coding rate protections

Effective supported PDCCH aggregation levels need to result in code rate < 0.75


Physical Downlink Shared Channel (PDSCH)

Transmits DL packet data One Transport Block transmission per UEs code word per subframe A common MCS per code word per UE across all allocated RBs Independent MCS for two code words per UE 7 PDSCH Tx modes

Mapping to Resource Blocks (RBs) Mapping for a particular transmit antenna port shall be in increasing order of:

First the frequency index, Then the time index, starting with the first slot ina subframe.


Physical Downlink Shared Channel (PDSCH)

Code Words (maximum of 2) A code word represents an output from the channel coder 1 code word for rank 1 Transmission 2 code words for rank 2/3/4 Transmissions

Layer Mapping Number of layers depends on the number of Tx antennas and Wireless Channel Rank Fixed mapping schemes of code words to layers

Tx Antennas (maximum of 4) Maximum of 4 antennas (potentially upto 4 layers)

Pre-coding used to support spatial multiplexing Code book based precoding

PDSCH Generalized Transmission Scheme


Physical HARQ Indicator Channel (PHICH)

Used for ACK/NAK of UL-SCH transmissions Transmitted in:

Time Normal duration: 1st OFDM symbol Extended duration: Over 2 or 3 OFDM symbols Frequency Spanning all system bandwidth Mapping depending on Cell ID

FDM multiplexed with other DL control channels

Support of CDM multiplexing of multiple PHICHs


DL Reference Signals (RS)

The downlink reference signals consist of so-called reference symbols which are known symbols inserted within in the OFDM

time/frequency grid.

Similar with Pilot signal of CDMA. Used for downlink physical channel demodulation and channel quality measurement (CQI)

Three types of RS in protocol. Cell-Specific Reference Signal is essential and the other two types RS (MBSFN Specific RS & UE-Specific RS)

are optional.

Characteristics:

Cell-Specific Reference Signals are generated from cell-specific RS sequence and frequency shift mapping. RS sequence also carriers one

of the 504 different Physical Cell ID.

The two-dimensional reference signal sequences are generated as the symbol-by-symbol product of a two-dimensional orthogonal sequence and a two-dimensional pseudo-random sequence:

There are 3 different two-dimensional orthogonal sequences There are 168 different two-dimensional pseudo-random sequences

The frequency interval of RS is 6 subcarriers.

RS distributes discretely in the time-frequency domain, sampling the channel situation which is the reference of DL demodulation.


DL Reference Signals (RS)

0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l

On

e an

ten

na

po

rtT

wo

an

ten

na

po

rts

Resource element (k,l)

Not used for transmission on this antenna port

Reference symbols on this antenna port

0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l 0l

1R

1R

1R

1R

6l 0l

1R

1R

1R

1R

6l

0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l 0l

1R

1R

1R

1R

6l 0l

1R

1R

1R

1R

6l

Fo

ur

ante

nn

a p

ort

s

0l 6l 0l

2R

6l 0l 6l 0l 6l

2R

2R

2R

3R

3R

3R

3R

even-numbered slots odd-numbered slots

Antenna port 0


Antenna port 1


Antenna port 2


Antenna port 3

On

e A

nte

nn

a

Po

rt

Two

An

ten

na

Po

rts

Fo

ur

An

ten

na

Po

rts

Antenna Port 0 Antenna Port 1 Antenna Port 2 Antenna Port 3

R1: RS transmitted in 1st ant port

R2: RS transmitted in 2nd ant port

R3: RS transmitted in 3rd ant port

R4: RS transmitted in 4th ant port

Downlink RS consist of know reference symbol locations Antenna ports 0 and 1

Inserted in two OFDM symbols (1st and 3rd last OFDM symbol) of each slot. 6 subcarriers spacing and 2x staggering (45kHz frequency sampling)

Antenna ports 2 and 3 Inserted in one OFDM symbol (2nd OFDM symbol) of each slot. 6 subcarriers spacing and 2x staggering across slots.


DL Reference Signals (RS) Measurement Reference

3GPP is defining following measurements:

RSRP (Reference Signal Received Power) RSRQ (Reference Signal Received Quality)

RSRP, 3GPP definition RSRP is the average received power of a single RS resource element. UE measures the power of multiple resource elements used to transfer the reference signal but then takes an average of them rather than summing them.

Reporting range -44-140 dBm



RSSI (Received Signal Strength Indicator)

RSSI not reported to eNodeB by UE Can be computed from RSRQ and RSRP that are reported by UE RSSI measures all power within the measurement bandwidth

Measured over those OFDM symbols that contain RS Measurement bandwidth RRC-signalled to UE

RSSI = wideband power= noise + serving cell power + interference power

Without noise and interference, 100% DL PRB activity: RSSI=12*N*RSRP

RSRP is the received power of 1 RE (3GPP definition) average of power levels received across all Reference Signal symbols within the considered measurement frequency bandwidth

RSSI is measured over the entire bandwidth N: number of RBs across the RSSI is measured and depends on the BW

Based on the above, under full load and high SNR:

RSRP (dBm)= RSSI (dBm) -10*log (12*N)



RSRQ ,3GPP definition

RSRQ = N x RSRP / RSSI N is the number of resource blocks over which the RSSI is measured, typically equal to system bandwidth

RSSI is pure wide band power measurement, including intracell power, interference and noise

RSRQ reporting range -3-19.5dB


Uplink RS (Reference Signal)

Uplink RS (Reference Signal):

The uplink pilot signal, used for synchronization between E-

UTRAN and UE, as well as uplink channel estimation.

Two types of UL reference signals:

[1] DM RS (Demodulation Reference Signal),

-Associated with transmission of PUSCH or PUCCH

-Purpose: Channel estimation for Uplink coherent

demodulation/detection of the Uplink control and data

channels

-Transmitted in time/frequency depending on the channel

type (PUSCH/PUCCH), format, and cyclic prefix type

[2] SRS (Sounding Reference Signal), -Not associated with transmission of PUSCH or PUCCH

-Purpose: Uplink channel quality estimation feedback to the

Uplink scheduler (for Channel Dependent Scheduling) at the

eNodeB

-Transmitted in time/frequency depending on the SRS

bandwidth and the SRS bandwidth configuration (some rules

apply if there is overlap with PUSCH and PUCCH)


Physical Random Access Channel (PRACH)

Basic Principle of Random Access :

Random access is the procedure of uplink synchronization between UE and E-UTRAN.

Prior to random access, physical layer shall receive the following information from the higher layers:

Random access channel parameters: PRACH configuration, frequency position and preamble format, etc.

Parameters for determining the preamble root sequences and their cyclic shifts in the sequence set for the cell, in order to demodulate the random access preamble.

1.Either network indicates specific PRACH resource or UE selects from

common PRACH resources.

2.UE sends random access preambles at increasing power.

3.UE receives random access response on the PDCCH which includes

assigned resources for PUSCH transmission.

Physical Resource Blocks (PRB) and Modulation and Coding Scheme (MCS)

4.UE sends signaling and user data on PUSCH.


Physical Uplink Shared & Control Channel (PUSCH & PUCCH)

Physical Uplink Control Channel (PUCCH)

Carries Hybrid ACK/NACK reponse DL transmission Always transmitted using QPSK Is punctured into UL-SCH to avoid errors due to missed DL assignments and thus different

interpretations of ACK/NACK symbols

Carries Sceduling Request (SR) Carries CQI (Channel Quality Indicator)

Physical Uplink Shared Channel (PUSCH)

Carries data from the Uplink Shared Channel (UL-SCH) transport Channel.

If data and control are transmitted simultaneously -> PUSCH control located in the same region as data (time multiplexed) required to preserve single-carrier properties

If only control is transmitted -> PUCCH control located at reserved region at band edges one RB is shared by multiple UEs through orthogonal spreading sequences


Initial Acquisition Procedure ( Cell Search) Cell search is the process of identifying and obtaining downlink synchronization to cells, so that the broadcast information from

the cell can be detected. This procedure is used both at initial access and at handover.

[4] LTE KEY TECHNOLOGY INTRODUCTION



LTE MIMO (Multiple Input Multiple Output)

LTE specifications support the use of multiple antennas at both transmitter (tx) and receiver (rx). MIMO (Multiple Input Multiple Output) uses this antenna configuration.

LTE specifications support up to 4 antennas at the tx side and up to 4 antennas at the rx side (here referred to as 4x4 MIMO configuration).

In the first release of LTE it is likely that the UE only has 1 tx antenna, even if it uses 2 rx antennas. This leads to that so called Single User MIMO (SU-MIMO) will be supported only in DL (and maximum 2x2 configuration).

OFDM works particularly well with MIMO MIMO becomes difficult when there is time dispersion OFDM sub-carriers are flat fading (no time dispersion)

3GPP supports one, two, or four transmit Antenna Ports Multiple antenna ports Multiple time-frequency grids Each antenna port defined by an associated Reference Signal

LTE DL transmission modes

Multiple layers means that the time- and frequency resources (Resource Blocks) can be reused in the different layers up to a number of times

corresponding to the channel rank. This means that the same resource allocation is made on all transmitted layers.



DL Single User MIMO with 2 antennas



DL Multi User MIMO (MU-MIMO)



UL Multi user MIMO (virtual MIMO)


LTE MIMO Evolution



LTE Voice Solution Options



LTE Voice Solution in 3GPP & GSMA



Voice Options Comparison in LTE Environment



Flash CSFB (R9 Redirection with SIB)



SON (Self Organization Network) is introduced in 3GPP release 8. This function of LTE is required by

the NGMN (Next Generation Mobile Network) operators.

From the point of view of the operators benefit and experiences, the early communication systems

had bad O&M compatibility and high cost.

New requirements of LTE are brought forward, mainly focus on FCAPSI (Fault, Configuration, Alarm,

Performance, Security, Inventory) management:

Self-planning and Self-configuration, support plug and play

Self-Optimization and Self-healing

Self-Maintenance



Three SON RRM functionalities have been standardized in Rel 8.


SON_ANR (Automatic Neighbor Relation)

The ANR function relies on cells broadcasting their identity on a global level

E-UTRAN Cell Global Identifier (ECGI) The eNB instructs UE to perform measurements on neighbor cells The eNB can decide to add this neighbor relation and can use the Physical Cell ID and ECGI to: Look up transport layer address to the new eNB Update Neighbor Relation List If needed, set up a new X2 interface toward the new eNB

Main ANR management functions:

Automatic detection of missing neighboring cells

Automatic evaluation of neighbor relations

Automatic detection of Physical Cell Identifier (PCI) collisions

Automatic detection of abnormal neighboring cell coverage

Automatic Neighbor Relation (ANR) can automatically add and

maintain neighbor relations. The initial network construction,

however, should not fully depend on ANR for the following

considerations:

ANR is closely related to traffic in the entire network

ANR is based on UE measurements but the delay is

introduced in the measurements.

After initial neighbor relations configured and the number of UEs

increasing, some neighboring relations may be missing. In this case,

ANR can be used to detect missing neighboring cells and add

neighbor relations.


SON_MLB( Mobility Load Balancing)

END OF DOCUMENT


Documents

4G Long Term Evolution Introduction_18-Jan-2014