LTE_Technical_Principles

LTE Technical Principles

Agenda

1. LTE/LTE-A Requirements

2. E-UTRAN Architecture

3. LTE Physical Layer functionalities

4. LTE Higher Layer protocol stacks

5. LTE A Technologies

3 | Titre de la présentation | Mois 2008 © Alcatel-Lucent 2008, d.r., XXXXX

LTE/LTE-A Requirements1


LTE Design Objective

Provide significantly improved power, bandwidth efficiencies, and delay in e-UTRA

User-plane latency: < 5 ms one way (UE to Core Network)

Control-plane latency: < 100ms (camped to active), < 50ms (dormant to active)

Facilitate the convergence with other networks/technologies

Reduce transport network cost – packet switching system

Downlink

100 Mbps peak data rate in 20 MHz

– 2x2 MIMO

User throughput– 3-4x HSDPA (average)– 2-3x HSDPA (5% CDF)

Spectral Efficiency– 3-4x HSDPA

Uplink

50 Mbps peak data rate in 20 MHz– Assumes one Tx antenna

User throughput– 2-3x E-DCH (average)– 2-3x E-DCH (5% CDF)

Spectral Efficiency– 2-3x E-DCH


LTE/LTE-A Target Performance

Item LTE

Requirement

LTE Results LTE-A

Requirement

Peak Data Rate

DL > 100Mbps

(5 bps/Hz)

326.4Mbps(4

layer)

172.8 Mbps(2

layer)

1 Gbps

(30 bps/Hz)

UL > 50Mbps

(2.5 bps/Hz)

86.4 Mbps

(64QAM)

57.6 Mbps

(16QAM)

500 Mbps

(15 bps/Hz)

Latency

C-plane Idle Active < 100msec 51.25 ms + 3 *

S1 delay

< 50 ms

Dormant (DRX)

Active

< 50msec Much shorter

than 51.25 ms

< 10 ms

U-

plane

< 5msec 4 ms < 5 msec (better

than LTE)


Delay Budget to achieve 5 ms in UTRA

Ts1u ms

UE eNB aGW

1 ms 0.5 ms

1 ms 0.5 ms

HARQ RTT 2.5 ms

1 ms

1 ms

S1-U TTI + frame alignment

0.75 ms

0.75 ms

Ts1u ms

U-plane latency components in LTE


Items LTE

Requirement

Evaluation

results

LTE-A Requirements

Average

Spectrum

Efficiency

DL 3-4 UTRA (0.53

bps/Hz )

1.56 – 2.67

bps/Hz

3.5 bps/Hz

UL 3-4 UTRA

(0.332 bps/Hz)

0.68 – 1.03

bps/Hz

1.7 bps/Hz

Cell Edge

Spectrum

Efficiency

DL 2-3 UTRA (0.02

bps/Hz)

0.04 – 0.08

bps/Hz

0.06-0.1 bps/Hz

UL 2-3 UTRA

(0.009 bps/Hz)

0.01-0.052

bps/Hz

0.035-0.6 bps/Hz

VoIP 300 per 5 MHz

Average Throughput/Edge Throughput/VoIP Capacity


Coverage

LTE

Target/Requirement

Evaluation results LTE-A Requirments

User throughput and

spectrum efficiency

should be met the target

in up to 5 km cell range

Same or somewhat

lower than that in ISD of

1732 m

Same as LTE

Support of very large cell Support for an

adjustable random-

access-burst length for

large cell

Same as LTE


Enhanced MBMS and Network Synchronization

Item LTE Requirement Evaluation

results

LTE-A

Requirements

Enhanced

MBMS

1 bps/Hz in an

urban or suburban

environment

D1 3.13 bps/Hz (1619

ISD)

D2 3.02 bps/Hz (2310

ISD)

D3 0.99 bps/Hz (1619

ISD)

D4 3.18 bps/Hz (4375

ISD)

Better than LTE

Network

Synchronizatio

n

Inter-site time

synchronization

should be

supported

provided these

bring sufficient

benefits

The benefits of

synchronised

system is clarified

Same as R-8 LTE


E-UTRAN Architecture2


E-UTRA Architecture

Objectives for the architecture evolution - Develop a System Tailored to deliver broadband and real time Packet Switched services Reduced latency compared with the current UMTS system.

Fast state transition between dormant and connected mode

Reduce signalling and call set up time

Simplify system deployment and operation & maintenance – plug & play

Competitive with other emerging technologies

Flat-IP Architecture for e-UTRA

Scalability to support the high data rates required for LTE

No single point of failure and load sharing and redistribution capabilities

Reduced number of nodes for lower transport delay

Backhaul costs should be minimized

Simplicity in supporting system plug & play


Outlook of E-UTRA Architecture Evolution

UMTS NodeB

GGSN

S1

GSN, MM, SM?HSS interface,

UE temp IDSecurity keys

Encryption

Header compress

ion

RRC, Cell control,Scheduling,

HARQ

aGW

LTE eNB

SGSN

MM, SM, HSS interface, UE temp ID, Security keys

RNC

RRC, Encryption,Header Compression,

Cell control

Scheduling, HARQ

CN

RAN

Iu

LTE ArchitectureUMTS Architecture

Principal decisions:- No geographical association of upper nodes (removes single point of failure)- Security termination is in the upper Node


LTE Network architecture

IASA

S5b

Evolved Packet Core

Evolved RAN S1 SGi

Op. IP

Serv. (IMS, PSS, etc…)

Rx+

S2

GERAN

UTRAN

Gb

Iu

S3

MME UPE

S4

non 3GPP IP Access

HSS

PCRF

S2

S7

S6

WLAN 3GPP IP Access

* Color coding: red indicates new functional element / interface

3GPP Anchor

SGSN

SAE Anchor

GPRS Core

S5a


Evolved Packet System (EPS) Architecture: Goals

The goal of the System Architecture Evolution (SAE) effort in 3GPP is to develop a framework for the evolution and migration of current systems to a system which supports the following:

high data rates low latency packet-optimized (all IP network) provides service continuity across heterogeneous access networks

Must allow co-existence with UMTS/HSPA and GSM/EDGE should be possible to maintain a packet session in a way that is seamless to the user of a multi-mode device

Allows operators to gradually roll out LTE in the areas of highest demand first

Currently being extended to also support EV-DO, and WiMAX

LTE coverage

UMTS/HSPA

coverage

GSM/EDGE coverage


Evolved Packet System Architecture Overview

EPS is based upon an end-to-end all-IP architecture Every services are delivered over IP

Clearly delineated control plane & data plane

Simplified network architecture: from 2 to 1 core

MME

PCRF

SGW PDN GW

PDSN HA


Evolution to EPS –

A Unified IP-based Always-on, QoS-enabled Network

Legacy Infrastructure

RNCHA

Evolved Packet System

Radio Mobility Intelligence placed

in the eNB

BE to QoS/HAnon-blocking

1 2 4

BTS Internet

Multi-Media

Services

PDSN

Backhaul

(TDM/ATM)

RNC Bearer mobility

collapse into the SGW

3Backhaul transition

To IP/Ethernet

Backhaul

(IP/Ethernet)

MCS voice and SGSN

packet mobility collapse into

the SGW RNC control

distributed into the MME/eNB

SGSN control collapse into

the MME

CS Core

PS Core

5CS and PS

Collapse into aUnified IP backbone

Service aware and

mobile aware IP network

6

MME

SGW PDN GWeNB

PCRF


Functional Implication of the New Mobile Core Architecture

3GPP Access Non-3GPP Access

PDSNRNCRNC SGSN/GGSN

MME

PCRF

SGW PDN GW

User Plane has Many Common Attributes with Fixed Broadband

Broadband capacity QoS for multi-service delivery Per-user and per-application policies Highly available network elements

Control Plane gained new Mobile-Specific Attributes

Mobility across networks & operators Distributed mobility management Massive increase in scalability Dynamic policy management


internet

eNB

RB Control

Connection Mobility Cont.

eNB MeasurementConfiguration & Provision

Dynamic Resource Allocation (Scheduler)

PDCP

PHY

MME

S-GW

S1MAC

Inter Cell RRM

Radio Admission Control

RLC

E-UTRAN EPC

RRC

Mobility Anchoring

EPS Bearer Control

Idle State Mobility Handling

NAS Security

P-GW

UE IP address allocation

Packet Filtering

EPS Architecture: Functional Description of Nodes

eNB- contains all radio access functions

Radio admission control Scheduling of UL and DL

data Scheduling and

transmission of paging and system broadcast

IP header compression (PDCP)

Outer-ARQ (RLC)

Mobility Management Entity Authentication Tracking area list management Idle mode UE reachability S-GW/PDN-GW selection Inter core network node signaling for

mobility between 2G/3G and LTE Bearer management functions

Serving Gateway Local mobility anchor for inter-eNB

handovers Mobility anchoring for inter-3GPP handovers Idle mode DL packet buffering Lawful interception Packet routing and forwarding

PDN Gateway IP anchor point for bearers UE IP address allocation Per-user based packet filtering Connectivity to packet data network

Policy

PCRF

Policy Decisions

Policy & Charging Rules Function

Network control of Service Data Flow (SDF) detection, gating, QoS & flow based charging

Dynamic policy decision on service data flow treatment in the PCEF (xGW)

Authorizes QoS resources


S7c

Big Picture View of the EPS

SGi

GERAN

UTRAN

S11

S3

S5

eUTRAN

HSS

S4

S1-U

S1-MME

S6a

SGSN

IP Network

Gx

X2

AFPCRF

ServingGateway

S101

S12

PDNGateway

CDMA/EVDOeRNC

HSGW

S2a

Standards based interfaces for inter-working with other 3GPP & non-3GPP networks

MME

MME, S-GW & PDN-GW are logically defined functions !

New interface / direct connectivity now exists between eNBs

eNB

eNB


LTE Physical Layer functionalities3


Fundamentals


LTE Air Interface Technologies and System design

Air Interface physical and multiple access technologies: DL: OFDMA

UL: SC-FDMA

Frequency- and time-domain link adaptation – frequency and time selective scheduling

Hybrid ARQ: Incremental Redundancy (Chase combining as a special case)

Modulation schemes: QPSK, 16QAM. 64QAM for both DL and UL.

Frequency reuse: universal reuse and interference mitigation scheme

Macro diversity for intra-NodeB DL transmission and e-MBMS in SFN

MIMO Technologies – Single-user MIMO, Multi-user MIMO, SDMA, beamforming, and Transmit Diversity

Radio Resource Allocation – distributed (DL only) and localized


OFDMA/SC-FDMA Characteristics

OFDMA/SC-FDMA allows spectrum scalability of LTE system operation

Up to 20 MHz to enable very high data rates –

UEs with Lower bandwidth (low cost) can be operated in the same system

OFDMA/SC-FDMA characteristic – ISI removal with Cyclic Prefix

CP Useful OFDM symbol time

OFDM symbol


Downlink


LTE Downlink: Scalable OFDMA

The LTE downlink uses scalable OFDMA

Fixed subcarrier spacing of 15 kHz for unicast– symbol time fixed at T = 1/15kHz = 66.67 s

Different UEs are assigned different sets of subcarriers so that they remain orthogonal to each other (except MU-MIMO)

Serial to Parallel

IFFT

bit strea

m user 1 . . .

Parallel to

Serial

add CP

Encoding + Interleaving

+ Modulation

20 MHz: 2048 pt IFFT

10 MHz: 1024 pt IFFT

5 MHz: 512 pt IFFT

Serial to Parallel

bit strea

m user 2


+ Modulation No in-cell interference -

different users use different subcarriers


Physical Channels to Support the LTE Downlink (Unicast)

eNode-BPhysical Downlink Shared Channel (PDSCH)

Physical Downlink Control Channel (PDCCH)

Physical Uplink Control Channel (PUCCH)

Carries DL traffic

DL scheduling grant

HARQ feedback for DL

CQI reporting

Physical Broadcast Channel (PBCH)Carries basic system broadcast information Synchronization Channel (SCH)

Allows mobile to get timing and frequency sync with the

cell

Physical Control Format Indicator Channel (PCFICH)

Time span of PDCCH

Physical HARQ Indicator Channel (PHICH)

HARQ feedback for

UL

UE


LTE Downlink: Mapping of Logical, Transport, Physical Channels

BCCHPCCH CCCH DCCH DTCH MCCH MTCH

BCHPCH DL-SCH MCH

DownlinkLogical channels

DownlinkTransport channels

DownlinkPhysical Channels

PDSCH PDCCHPBCH PHICHPCFICHSCHDL-RS PMCH

LTE makes heavy use of shared channels common control, paging, and part of broadcast information carried on PDSCHPCCH: paging control channel

BCCH: broadcast control channel

CCCH: common control channel

DCCH: dedicated control channel

DTCH: dedicated traffic channel

PCH: paging channel

BCH: broadcast channel

DL-SCH: DL shared channel


LTE Downlink: Channel Structure and Terminology

t

f

Physical Resource Block (PRB)

= 14 OFDM Symbols x 12 Subcarrier

This is the minimum unit of allocation in LTE

first 1..3 OFDM symbols* reserved for L1/L2 control signaling (PCFICH, PDCCH, PHICH)

one OFDM symbol

Subcarrier

Resource Element is a single subcarrier in an OFDM symbol

Slot (0.5 ms)

Subframe (1 ms)

Slot (0.5 ms)

15 kHz

PRB

subframe

* 2..4 symbols for 1.4 MHz bandwidth only


LTE Downlink: Maximum Number of Resource Blocks

frequency

1.4 MHz

3 MHz

5 MHz

10 MHz

20 MHz

100 PRBs

50 PRBs

25 PRBs

15 PRBs

6 PRBs

15 MHz

75 PRBs

All bandwidth options are

applicable to both FDD and

TDD


LTE Downlink Numerology (FDD)

FFT Size

Sampling Frequency

Number of Usable

Subcarriers*

Occupied BW

1.4 MHz 128 1.92 MHz 72 1.08 MHz

3 MHz 256 3.84 MHz 180 2.7 MHz

5 MHz 512 7.68 MHz 300 4.5 MHz

10 MHz 1024 15.36 MHz 600 9 MHz

15 MHz 1536 23.04 MHz 900 13.5 MHz

20 MHz 2048 30.72 MHz 1200 18 MHz

FFT sizes chosen such that sampling

rates are a multiple of the UMTS chip rate

(3.84 MHz)

Eases implementation of dual mode

UMTS/LTE terminals

*DC subcarrier is not used in the LTE DL. Reason: direct conversion receivers (zero IF) in UE can introduce significant distortion on baseband signal

components near 0 Hz


LTE Downlink: Common Reference Signal (RS) Structure


f

Subframe (1 ms)

Reference Symbol

Reference signal is staggered in the time-frequency plane; mobile interpolates to obtain a 2-D picture of the channel


LTE Downlink: Common RS Structure for 1, 2, and 4 Antenna Ports

R0

R0

R0

R0

R0

R0

R0

R0

0l 6l 0l 6l

R0

R0

R0

R0

R0

R0

R0

R0

0l 6l 0l 6l

R1

R1

R1

R1

R1

R1

R1

R1

0l 6l 0l 6l

even-numbered slots odd-numbered slots

R3

R3

R3

R3

0l 6l 0l 6l

R0

R0

R0

R0


R0

R0

R0

R0

0l 6l 0l 6l

R1

R1

R1

R1


R1

R1

R1

R1

0l 6l 0l 6l


R2

R2

R2

R2

0l 6l 0l 6l

One

ant

enna

por

tT

wo

ante

nna

port

sF

our

ante

nna

port

s

Antenna port 0 Antenna port 1 Antenna port 2 Antenna port 3

Not used for transmission on this antenna port

Reference symbols on this antenna port

lk,element Resource

Physical Resource Block

f

Resource Element (k,l)

Reference Symbols for this antenna port

not used for transmission

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

One

Ant

enna

Por

tT

wo

Ant

enna

Por

tsF

our

Ant

enna

Por

ts

RS overhead

4.8% for 1 Tx 9.5% for 2 Tx 14.3% for 4 Tx

In the multi-antenna case, there is a need for a RS power boost to overcome interference from neighbor cell data transmission

Cell-specific frequency shift of RS position to avoid RS overlap


LTE Downlink: Dedicated Signal (RS) Structure in Support of Beamforming


f

Subframe (1 ms)

Common Reference Symbol (Antenna Port 1)

UE can be configured to use a dedicated RS for data demodulation

sent only within those PRBs in which data is scheduled for the UE

beamforming weights applied to dedicated RS

Dedicated Reference Symbol

Common Reference Symbol (Antenna Port 0)


1 ms subframe

LTE Downlink: PBCH, SCH Location in Time & Frequency

10ms radio frame contains 10 subframes (20 slots)

P-SCH PBCH

0 1 2 3 4 5 6 7 8 9

innermost 6 PRBs (72 subcarriers = 1.08 MHz) same structure used for all system bandwidths

f

slot (0.5 ms)

subframe (1 ms)

slot (0.5 ms)

0 1 2 3 4 5 6 0 1 2 3 4 5 6

S-SCHPrimary sync channel (P-SCH) and secondary

sync channel (S-SCH) for cell search

1.4 MHz

3 MHz

5 MHz

10 MHz

20 MHz1.08

MHz


LTE Downlink: Basics of Cell Search

1. Mobile searches for P-SCH location in time and frequency; gives OFDM symbol boundaries

• 5ms period in time, center 72 subcarriers of system bandwidth; 3 possible sequences

2. Once P-SCH is acquired, the S-SCH location is known, and S-SCH is scrambled based on P-SCH sequence; S-SCH indicates the 10ms radio frame boundaries, and allows the mobile to obtain the group ID (168 group IDs); P-SCH + S-SCH acquisition gives physical layer cell ID

3. Knowledge of the transmission timing and physical layer cell ID allows the mobile to find the position of the downlink reference symbols (6 possible frequency shifts) as well as the pseudo-random sequence used

4. Once the downlink reference signal is obtained, the mobile can decode the broadcast channel (PBCH)

5 ms

10 ms

10 ms

1.08 MHz

There are 504 unique physical layer cell IDs, organized in 168 groups of 3


LTE Downlink: Broadcast of System Information

The Broadcast Control Channel (BCCH) is used to broadcast system information

needs to be heard over entire cell coverage area

The BCCH conveys RRC messages called SystemInformation (SI) A particular SI carries a number of System Information Blocks (SIBs) that

have the same scheduling period (i.e. RACH info, power control info, etc.)

SI-M is a special SI that carries a single SIB the Master Information Block (MIB)

The dimensioning of broadcast information is critical; hence in LTE, the BCCH is split into a primary and dynamic componentMaster Broadcast

carries SI-M; provides fast access to the minimum required

amount of information for efficient

discovery/mobility procedures

Mapped to BCH PBCH

SI Broadcast

delivers SIs with semi-static information valid for a longer time period; access is not as

time critical

Mapped to DL-SCH PDSCH


LTE Downlink: Downlink Shared Channel (DL-SCH)

DL-SCH transport channel carries scheduled packet data and is mapped onto the physical downlink shared channel (PDSCH)

Transport block CRC attachment

Code block segmentation and code block CRC attachment

Channel coding

Rate matching

Code block concatenation

Bit-level scrambling

24 bit CRC

Per-code-block CRC allows power savings in decoder with early termination, also allows parallel processing of code words in a MIMO SIC receiver

Modulation

R=1/3 turbo code from UMTS but with improved turbo interleaver (QPP) which allows efficient parallelization to reduce latencySimplified circular buffer rate matching with sub-block interleaving; rate matching is per code block to allow parallel processing of multiple code blocks

Per-user bit level scrambling introduced for interference randomization

PDSCH supports QPSK, 16-QAM, and 64-QAM

Enhancements introduced to allow efficient processing for very high data

rates


rates


LTE Downlink: Summary of Channels

Transport Channel Coding scheme Physical Channel Modulation

DL-SCH Turbo R=1/3 PDSCH QPSK, 16-QAM, 64-QAM

BCH Convolutional R=1/3 PBCH QPSK

PCH Turbo R=1/3 PDSCH QPSK

MCH Turbo R=1/3 PMCH QPSK, 16-QAM, 64-QAM

Control Information Coding Scheme Physical Channel Modulation

CFI Block code R=1/16 PCFICH QPSK

HI Repetition R=1/3 PHICH BPSK

DCIConvolutional R=1/3

with repetition/puncturing depending on CCE aggregation level

PDCCH QPSK


Uplink


Physical Channels to Support LTE Uplink

eNode-B

Random access for initial access and UL

timing alignment

Physical Downlink Control Channel (PDCCH)

Physical Random Access Channel (PRACH)

Physical Uplink Shared Channel (PUSCH)

Physical Uplink Control Channel (PUCCH)

UL scheduling grant

Traffic and channel

sounding reference

signal

UL scheduling request for time synchronized UEs

Physical HARQ Indicator Channel (PHICH)

HARQ feedbackUE


LTE Uplink: Mapping of Logical, Transport, Physical Channels

CCCH DCCH DTCH

RACH UL-SCH

UplinkLogical channels

UplinkTransport channels

UplinkPhysical Channels

PUSCH PUCCHPRACH

CCCH: common control channel

DCCH: dedicated control channel

DTCH: dedicated traffic channel

RACH: random access channel

UL-SCH: UL shared channel

PUSCH: physical UL shared channel

PUCCH: physical UL control channel

PRACH: physical random access channel


LTE Uplink: Multiple Access Scheme

To facilitate efficient power amplifier design in the UE, 3GPP chose single carrier frequency domain multiple access (SC-FDMA) in favor of OFDMA for uplink multiple access

SC-FDMA improves the peak-to-average power ratio (PAPR) compared to OFDM

~4 dB improvement for QPSK, ~2 dB improvement for 16-QAM

Reduced power amplifier cost for mobile

Reduced power amplifier back-off improved coverage

N o d e BU E C

U E B

U E A

U E A T ran sm it T im in g

U E B T ran sm it T im in g

U E C T ran sm it T im in g

a

b

g

SC-FDMA is still an orthogonal multiple access scheme

UEs are orthogonal in frequency

Synchronous in the time domain through the use of timing advance (TA) signaling

– Only need to be synchronous within a fraction of the CP length

– TA command sent as a MAC control element with 0.52 s timing resolution


LTE Uplink: DFT-SOFDMA-1

DFT spreading of modulation symbols reduces PAPR, but also leads to the possibility of inter-symbol interference (ISI)

In OFDM, each modulation symbols “sees” a single 15 kHz subcarrier (flat channel)

In DFT-SOFDM, each modulation symbol “sees” a wider bandwidth (i.e. m x 180 KHz) if channel is frequency selective within allocated bandwidth the we get ISI

– Equalization is required in the SC-FDMA receiver– Simple one-tap frequency domain equalization facilitated by use of CP

f = 15 kHz

OFDMA

+1 -1 -1 +1 -1 -1 +1 -1 +1 +1 +1 -1

SC-FDMA

+1 -1 -1 +1 -1 -1 +1 -1 +1 +1 +1 -1

DFT spreading


LTE Uplink: DFT-SOFDM Transmitter and Receiver Chain

SP . . .

IFFT

bit strea

m

. . . PS D/A

A/DSP

. . .

FFT. . .

PS

add CP

RF Tx

RF Rx

remove CP


+ Modulation

Demod + de-

interleave + decode

. . . DFT

IDFT

. . .

Equalizer

. . .

Subcarrier mapping

Subcarrier demapping


LTE Uplink Numerology

Same numerology between uplink and

downlink

FFT Size Sampling Frequency

Number of Usable

Subcarriers

Occupied BW

1.4

MHz128 1.92 MHz 72 1.08 MHz

3 MHz 256 3.84 MHz 180 2.7 MHz

5 MHz 512 7.68 MHz 300 4.5 MHz

10 MHz 1024 15.36 MHz 600 9 MHz

15 MHz 1536 23.04 MHz 900 13.5 MHz

20 MHz 2048 30.72 MHz 1200 18 MHz


1. Data demodulation reference signal (DM-RS)

Sent with each packet transmission in order to demodulate data

Occupies center SC-FDMA symbol of the slot

Possibility to signal different sequences (cyclic shift of base CAZAC sequence) for use with MU-MIMO

2. Sounding reference signal (SRS)

Used to sound uplink channel to support frequency selective scheduling

– Channel sensitive scheduling in both time and frequency

SRS parameters are UE specific and configured semi-statically– SC-FDMA symbol position (one symbol in subframe used for SRS)– Periodicity: {2, 5, 10, 20, 40, 80, 160, 320} ms– Bandwidth: narrowband or wideband (does not include PUCCH region)– Frequency hopping

SRS is not sent when there is a scheduling request (SR) or CQI to be sent on PUCCH (to avoid multi-carrier transmission)

LTE Uplink: Reference Signals-1


LTE Uplink: Reference Signals-2

DM-RS transmitted only over bandwidth allocated to UE

SRS can be transmitted over a wide bandwidth to allow channel quality estimation by the eNB uplink scheduler

Cyclic shift orthogonal sequences used to separate out different UEs SRS (8 possible shifts)

Repetition factor (RPF) = 2 creates two frequency combs for increased multiplexing capability

UE 1

UE 2

UE 3

Slot = 0.5ms

Slot = 0.5ms

SRS

DM-RS UE 1

DM-RS UE 2

DM-RS UE 3

Rules for SRS transmission

SRS only spans PUSCH bandwidth

SRS is not transmitted at the same time as CQI or Scheduling Request (SR) on PUCCH

Shortened ACK/NACK format is used on PUCCH to allow transmission of SRS while maintaining single-carrier transmission


LTE Uplink: Uplink Shared Channel (UL-SCH)

UL-SCH transport channel carries scheduled packet data and is mapped onto the physical uplink shared channel (PUSCH)

Transport block CRC attachment

Code block segmentation and code block CRC attachment

Channel coding

Rate matching

Code block concatenation

Bit-level scrambling

24 bit CRC

Per-code-block CRC allows power savings in decoder with early termination

Modulation

R=1/3 turbo code with improved turbo interleaver (QPP) which allows efficient parallelization to reduce latency

sub-block interleaving; rate matching is per code block to allow parallel processing of multiple code blocks

Per-user bit level scrambling introduced for interference randomizationPUSCH supports QPSK and 16-QAM; 64-QAM is optional


rates


rates

control MUXACK/NACK

CQI/PMI Mux control when needed; data is rate matched around CQI/PMI, but ACK/NACK punctures out data (kept indep. from RM to maintain turn-around)


LTE Uplink: Physical Uplink Control Channel (PUCCH)

PUCCH carries ACK/NACK and CQI to support the downlink, as well as scheduling requests (SR) for the uplink PRBs targets on two extreme ends of the frequency band are configured by RRC

Number of PUCCH PRBs reserved semi-statically based on required amount of control

PUCCH is never transmitted simultaneously with PUSCH, in order to maintain single-carrier transmission If ACK/NACK or CQI needs to be sent when there is PUSCH transmission, it must be

multiplexed together with PUSCH

resource 1

resource 0

0.5ms slot

resource 0

resource 1

0.5ms slot

Syste

m B

W

resource 2 resource 3

resource 2resource 3

PUCCHPUSCH


LTE Uplink: PUCCH Format 1a/1b for ACK/NACK 1 bit for SIMO (format 1a: BPSK), 2 bits for MIMO (format 1b: QPSK)

ACK/NACK is repeated 8 times and spread with length 12 CAZAC sequence in frequency CDM of ACK/NACK from different UEs by using different cyclic shifts of CAZAC sequence To further increase multiplexing capability, block-wise spreading via wi is added over each slot

– Example: Use 6 cyclic shifts and 3 orthogonal RS covers gives 18 multiplexed UEs per resource

PUCCH resource index for ACK/NACK Tx lowest CCE for PDCCH in DL scheduling grant

If SRS is transmitted in the same subframe, a shortened ACK/NACK format is used where the ACK/NACK symbol corresponding to the SRS location is punctured

CAZAC ACK/NACK

w1w0 w2 w3

IFFT IFFT IFFT IFFT

Reference symbolsOrthogonal cover

0.5ms slot

resource 1

resource 0

resource 0

resource 1

0.5ms slot



PUSCH

0.5ms slot

copy


LTE Uplink: PUCCH Format 1 for Scheduling Request

On/Off keying based on ACK/NACK design

Two sequences: length 4 + length 3

Compatibility with ACK/NACK transmission from different UE

SR resource on PUCCH is configured via RRC (time multiplexing and sequence #)

SR and ACK/NACK from same user can be multiplexed

If SR needs to be sent, then ACK/NACK is transmitted using the assigned SR PUCCH resource

SR and CQI from same user cannot be multiplexed

SR and SRS is cannot be sent in the same subframe (SRS is dropped)

Sequence 1

Sequence 2

resource 1

resource 0

resource 0

resource 1

0.5ms slot



PUSCH

0.5ms slot

copy


LTE Uplink: PUCCH Format 2 for CQI/PMI/RI 20 coded bits per subframe (10 symbols) with QPSK modulation

CDM of UEs by spreading each symbol with a length 12 CAZAC sequence in frequency CQI/PMI/RI PUCCH resources assigned via RRC ACK/NACK can be multiplexed with CQI (format 2a/2b); drop CQI when SR is transmitted SRS not sent in same subframe as CQI (SRS dropped): higher layer config should try to avoid

resource 1

resource 0

resource 0

resource 1



PUSCH

•CAZAC

•IFFT•IFFT •IFFT•IFFT•IFFT•IFFT •IFFT•IFFT •IFFT•IFFT

•CQI

0.5ms slot

RS

•IFFT•IFFT •IFFT•IFFT•IFFT•IFFT •IFFT•IFFT •IFFT•IFFT

0.5ms slot


LTE Uplink: Random Access Channel-1

The random access channel (RACH) is used during initial access, handoff, or when uplink synchronization is lost

UE sends a RACH preamble on physical random access preamble (PRACH)

UE first obtains downlink timing from SCH, then sends RACH preamble (non-synchronized) eNB detects timing preamble and sends a timing advance command to time synchronize UE

Gap time reflects the timing uncertainty due to round trip propagation delay

CP is used to allow frequency domain processing, and must cover the round trip propagation delay as well as the delay spread

Formats #2 and #3 offer a 2 x 0.8ms preamble repetition to improve detection performance in poor channel conditions

fRA = 1/0.8ms = 1.25 kHz sensitivity to

doppler shift from high speed UEs (greater than ~120 km/hr)

Root sequence length = 839; different signatures are generated by first using different cyclic shifts of a single root sequence (orthogonal), and then using additional root sequences as needed (low cross-correlation)

CP Zadoff-Chu (ZC) Sequence

Tcp Tseq Tgap

RA slot

Format

RA slot

Tcp Tseq TgapMax cell

size#0 1 ms ~0.1 ms 0.8 ms ~0.1 ms ~15 km

#1 2 ms~0.68

ms0.8 ms ~0.5 ms ~75km

#2 2 ms ~0.2 ms 1.6 ms ~0.2 ms ~30 km

#3 3 ms~0.68

ms1.6 ms ~0.7 ms ~100 km

Max cell size (m) = 3E8 * Tgap/2


LTE Uplink: Random Access Channel-2

PRACH sent in reserved time-frequency zone; configured semi-statically PRACH resource = 6 PRBs (1.08 MHz); at most one PRACH resource per subframe PRACH resource contains 64 preamble sequences (6 bits)

– preambles can all be orthogonal for small cell sizes (different cyclic shifts of root ZC seq.)– not orthogonal for larger cell sizes (need to use different root ZC sequences)

PRACH access slots can occur every 1, 2, 5, 10, or 20ms– 20ms option can only be used in synchronized networks– 10ms max for non-synchronized networks so that UE does not need to obtain the SFN from

the target cell BCH in handover scenario (radio frame timing provided by the SCH)

freqSch

eduled Data

1 ms

6 PRBs = 1.08 MHz

PRACH opportunitie

s

PRACH cycle


LTE Uplink: Contention Based Random Access Procedure

1. PRACH preamble: 6 bits (64 signatures) consisting of 5 bits random ID + 1 bit info

2. RA response generated by MAC on DL-SCH using RA-RNTI on associated PDCCH

RA-RNTI tied to time/freq resource of PRACH

Semi-synchronous, no HARQ

Contains RA preamble identifier, timing alignment info, initial uplink grant

3. First scheduled UL transmission on UL-SCH

Uses HARQ

For initial access, contains RRC connection request carried on CCCH, NAS UE identifier but no NAS message

4. Contention resolution on DL-SCH

Generated by RRC and carried on CCCH

UE eNB

Random Access Preamble1

Random Access Response 2

Scheduled Transmission3

Contention Resolution 4


LTE Uplink: Non-Contention Based Random Access Procedure

0. eNB assigns non-contention RA

preamble to UE. Signaled by:

HO command generated by target eNB via source eNB for handover

MAC signaling for DL data arrival

1. RA preamble transmission by UE on

assigned non-contention preamble

2. RA response on DL-SCH

Non-contention based random

access improves access time


LTE Uplink: Power Control-1

Open-loop power control is the baseline uplink power control method in LTE (compensation for path loss and fading)

Open-loop PC is needed to constrain the dynamic range between signals received from different UEs

Unlike CDMA, there is no in-cell interference to combat; rather, fading is exploited by rate control

In classic open-loop PC:

1. eNB broadcasts the total uplink interference level (Itot) and the SINR target (nominal) together as Ponominal (dBm) = nominal (dB) + Itot (dBm)

2. UE estimates path loss + shadowing (PL) on the downlink by measuring downlink reference signal

3. UE sets its transmit PSD (power per PRB) in order to achieve the broadcast SINR target. In dB scale:

TxPSD(dBm) = PL(dB) + Ponominal (dBm)

DL Reference Signal

BCH: Po_nominal

In classic open-loop PC, all UEs achieve the same target SINR

UEs near interior of cell transmit at reduced PSD poor spectral efficiency



Fractional power control is introduced to allow a more flexible trade-off between spectral efficiency and cell edge rates

TxPSD(dBm) = aPL(dB) + Ponominal (dB)

Fractional compensation factor a < 1 is introduced so that only a fraction of the path loss is compensated

Target SINR is now a function of the UE’s path loss target SINR increases with decreasing path loss. In dB scale, we have

TargetSINR(dBm) = nominal (dB) + (1-aPL(dB)

With a=1, we have classic open-loop PC

As we reduce a the range of target SINRs increases between UEs, and we can achieve higher spectral efficiency at the expense of cell edge rate

DL Reference Signal

BCH: Po_nominal, a

Target SINR



Additional user-specific power offsets can be sent via RRC signaling; can be used to correct open-loop errors (i.e. PA errors), or to allow proprietary methods to create a power profile

TxPSD(dBm) = aPL(dB) + Ponominal (dB) + Pouser (dB)

DL Reference Signal

BCH: Po_nominal, a

RRC: Po_user

Aperiodic fast power control is made possible by additionally allowing a dynamic adjustment of the UE transmit PSD with 1 or 2 bit power control commands, can either be accumulated adjustment or absolute. PC command sent via:

UL scheduling grant (DCI Format 0): 2 bit TPC command– Absolute: {-4, -1, +1, +4} dB– Accumulated: {-1, 0, +1, +3} dB

On separate power control channel (DCI Format 3/3A)– Format 3: 2 bits representing {-1, 0, +1, +3} dB– Format 3A: 1 bit representing {-1, +1} dB

TxPSD(dBm) = aPL(dB) + Ponominal (dB) + Pouser (dB) + f()



DL Reference Signal

BCH: Po_nominal,

a_TF

RRC: Po_user

The UE transmit PSD can optionally be made dependent on the MCS level assigned, through use of TF which specifies power offsets as a function of the MCS level assigned by the scheduler

TxPSD(dBm) = aPL(dB) + Ponominal (dB) + Pouser (dB)

+ f() + TF

The UE’s total power scales with the number of assigned PRBs (M)

TxPower(dBm) = min( Pmax (dBm), TxPSD(dBm) + 10log10(M) )

SRS follows PUSCH power control with a configurable power offset

Separate power control parameters for PUSCH and PUCCH


MIMO


Multiple Antenna Techniques

Spatial Multiplexing (SM) SU-MIMO Multiple data streams sent to the same user (max 2

codewords) Significant throughput gains for UEs in high SINR conditions

Spatial Division Multiple Access (SDMA) or Beamforming Different data streams sent to different users on same

resource Improves throughput even in low SINR conditions (cell-edge) Works even for single antenna mobiles User-specific RS (dedicated RS) supported to facilitate

beamforming; used for demodulation of PDSCH

Transmit Diversity Improves reliability on a single data stream; space-frequency

block coding (SFBC), cyclic delay diversity (CDD) Fall back scheme if channel conditions do not allow SM;

useful to improve reliability on common control channels


MIMO Support is Different in Downlink and Uplink

Downlink MIMO

Supports Spatial Multiplexing, MU-MIMO, and Transmit Diversity

Uplink MIMO

Initial release of LTE will only support MU-MIMO with a single PA at the UE desire to avoid multiple PAs at UE

Cyclic-shift orthogonal pilots used in the uplink to facilitate MU-MIMO operation


DL Spatial Multiplexing Modes for Low and High Speeds

UE indicates best combo of CQI/PMI/RI for max throughput (i.e. high-rank/low-MCS vs. low-rank/high MCS)

Closed-loop SM is ideally suited for low speed scenarios when the CQI/PMI/RI feedback is accurate

Open-loop SM provides robustness in high speed scenarios when the feedback is not accurate

M Tx N Rx

VMIMO

HHH

RIHVUH

UHSelect #

code words

Modulation +

coding

PMICQI

Modulation +

coding

Demod + decode

demod + decode

precoding

Layer mappin

g

Closed-Loop SM Open-Loop SM

CQI separate CQI for each codeword fed backone value fed back applicable over all

layers

PMIPMI feedback from UE based on instantaneous

channel state

no feedback from UE, fixed precoding at eNB with large delay CDD to improve

robustness

RIbased on SINR and instantaneous channel

matrix rankRI=1 corresponds to closed loop TxDiv (CLTD)

typically based only on SINRRI=1 corresponds to open loop TxDiv

(SFBC)


Multi-codeword SM and Layer Mapping

LTE allows multi-codeword (MCW) SM in which the streams are encoded independently rather than jointly as in single codeword SM

Advantages: MCS can be adjusted on each stream independently to improve throughput, allows for SIC receiver

Disadvantages: Increased feedback as ACK/NACK as CQI are needed per codeword

A maximum of 2 codewords is supported, even when a rank-3 or rank-4 transmission is used in the case of 4x4 MIMO. Mapping of codewords to layers (e.g. streams) as below:

Precoding(2x4)

CW#1

Precoding(1x4)

CW#1

CW#2

Precoding(4x4)

CW#1

CW#2

S/P

S/P

Precoding(3x4)

CW#1

CW#2 S/P

Rank-1

Rank-3

Rank-2

Rank-4

layers

Precoding(2x4)

CW#n S/P

Rank-2

(useful for ReTx)

A single codeword can be mapped to 2 layers only in the case of 4 Tx antennas (for efficient retransmission of a codeword mapped to 2 layers in the previous transmission)


Codebook Based Precoding-1

Precoding vectors/matrices specified for 2 and 4 transmit antennas: 4 codebook entries for 2 Tx antennas, 16 codebook entries for 4 Tx antennas

Precoding vector for one codeword

Precoding matrix for two codewords

2 Tx antennas 4Tx antennasThis entry is only used for open

loop SM


Codebook Based Precoding-2

Codebook entries support a variety of antenna spacings & configurations

Network can configure the UE to only consider a subset of the codebook entries

-100 -80 -60 -40 -20 0 20 40 60 80 1000

0.5

1

1.5

2

2.5

3

3.5

4

Angle (deg)

Gai

n

4 Antennas, /2 spacing

index 0

index 1

index 3

index 4index 5

index 6

index 7

Example: 4 antennas with half-wavelength spacing

Codebook entries 0,1,3,4,5,6,7 with 1 layer form a set of fixed beams


MIMO Technologies: SU-MIMO

segmentation, coding,VRB layer multiplexing

VRB / VARB / PRBprocessing

link adaptation and resource assignment

OF

DM

Seg.

Input bitsequence of user k

Seg. : segmentationFEC : forward error coding : interleaving

: modulationP : power allocation

FECk k

FECk k

FECk k

Re

sou

rce

Ma

ppe

rsp

ace P

PP




OF

DM







OF

DM

Seg.






FECk kFECk kFECk k

FECk kFECk kFECk k

FECk kFECk kFECk k

Re

sou

rce

Ma

ppe

rR

eso

urc

e

Ma

ppe

rsp

ace

spa

cesp

ace PP

PPPP

SU-MIMO – multiple codeword, SM transmission


MIMO Technologies -MU-MIMO (beamforming, SDMA)




OF

DM

Seg.



: modulationP : power allocationV : beamforming

FECk k

FECk k

FECk k

Re

sou

rce

Ma

ppe

rsp

ace

P

V

P

V

P

V




OF

DM







OF

DM

Seg.






FECk kFECk kFECk k

FECk kFECk kFECk k

FECk kFECk kFECk k

Re

sou

rce

Ma

ppe

rR

eso

urc

e

Ma

ppe

rsp

ace

spa

cesp

ace

P

V

P

V

P

V

P

V

P

V

P

V

Notes: 1. Transmission to a single user is shown. For multiple users, add signals after beamforming.2. Generalize to SM using a precoding matrix.3. Precoding vector (or matrix) is recomputed up to once per TTI


MBMS


Inter-Cell Interference Mitigation

Principle - coordinate the transmission power and limit the inter-cell interference

Interference Mitigation coordination- Static – inter-cell coordination strategy provision in advance Semi-static – S1/X2 signaling for inter-cell dynamic coordination

Inter-cell interference Mitigation schemes Inter-cell interference-cancellation/suppression

Spatial suppression by means of multiple antennas at the UE Interference cancellation based on detection/subtraction of the inter-

cell interference Inter-cell interference mitigation/coordination by means of

Intelligent scheduling based on priority allocation of sub-frame/sub-carrier allocation, frequency scheduling, power levels coupled to sub-band priorities, soft reuse: power levels coupled to groups of sub-bands etc.

Power control – open loop


Multicast/Broadcast in a Single Frequency Network (MBSFN)

Synchronized transmission from multiple cells on same set of subcarriers

Appears as extra multipath at the terminal, as long as signal components from different cells arrive within the CP length

– Extended CP lengths used in broadcast to account for propagation delay from different cells

– Signals from different cells combine coherently over the air

Macro-Diversity gains exploited in OFDMA system

Scheduler coordinates broadcast frames through RRM coordination

Data Synchronization


Evolved Multimedia Broadcast Multicast Service (MBMS)

E-MBMS can be used in synchronous or asynchronous networks, and can either be on a stand-alone E-MBMS carrier or multiplexed with unicast traffic

Subframes reserved for broadcast are reserved periodically in time

TDM of broadcast and unicast subframes (FDM is not allowed)

Unic

ast

Unic

ast

Unic

ast

Bro

adca

stU

nic

ast

Unic

ast

Unic

ast

Unic

ast

Unic

ast

Bro

adca

stU

nic

ast

Unic

ast

time1ms

subframe

With E-MBMS, multiple users receive the same information using the same radio resources much more efficient approach for delivering common content

Examples: television broadcasts, news updates, sports scores, etc. Broadcast: every user receives content Multicast: only users with a subscriptions receive content

Unic

ast

Unic

ast

Unic

ast

Unic

ast

Unic

ast


Multicast Broadcast on a Single Frequency Network (MBSFN)

MBSFN refers to a mode of E-MBMS where synchronized transmission of the same content from multiple cells on same set of subcarriers takes place Appears as extra multipath at the mobile, as long as signal components from different cells

arrive within the CP length diversity gains exploited for “free” with over the air combining

An extended CP length is used for broadcast subframes to account for propagation delay from different cells

– CP length extended from 4.7 s to 16.6 s (increased CP overhead)– 6 OFDM symbols per slot for broadcast (instead of 7 for unicast)


MBSFN for Larger Cells (7.5 kHz Subcarrier Spacing)

To handle even larger cells with additional propagation delay, a second extended CP of 33 s is defined

OFDM symbol time is doubled from 66.6 s to 133 s, so that the extended CP overhead will not be excessive

Increased symbol time means subcarrier spacing reduces from 15 kHz to 7.5 kHz

Increased sensitivity to high doppler

The 7.5 kHz mode can only be used as a stand-alone E-MBMS carrier, cannot be multiplexed with unicast traffic

ss s

s s s

Unicast subframe

(7% CP overhead)

Broadcast subframe

(25% CP overhead)


LTE Higher Layer protocol stacks4


LTE Protocol Model

Vertical Planes

User Plane

Control Plane

- RRC terminated in eNB Broadcast, Paging, RRC connection management, RB control, Mobility functions, UE measurement reporting and control

- BMC layer is not needed in E-UTRAN, since MBMS is used to broadcast- RLC/MAC layer (terminated in eNB):

•Scheduling, ARQ, HARQ …

- PDCP layer (moved now to eNB):

•Header Compression (ROHC), Ciphering, Integrity protection…

eNB

PHY

UE

PHY

MAC

RLC

MAC

SAE Gateway

PDCPPDCP

RLC

eNB

PHY

UE

PHY

MAC

RLC

MAC

MME

RLC

NAS NAS

RRC RRC


Layer 2 Structure for DL in eNB

Segm.ARQ

Multiplexing UE1

Segm.ARQ

...

HARQ

Multiplexing UEn

HARQ

BCCH PCCH

Scheduling / Priority Handling

Logical Channels

Transport Channels

MAC

RLCSegm.ARQ

Segm.ARQ

PDCPROHC ROHC ROHC ROHC

Radio Bearers

Security Security Security Security

...


LTE MAC

Mapping between logical and transport channels

BCCHPCCH CCCH DCCH DTCH MCCH MTCH

BCHPCH SCHRACH MCH

Logical channels

Transport channels

•Main differences with UTRAN Rel6 mapping:

- Absence of CTCH ( no FACH)- Dedicated transport channels are not supported - New shared channels: UL-SCH and DL-SCH

BC

HB

CC

H

PC

H

PC

CH

CC

CH

DC

CH

DT

CH

CT

CH

MB

MS

CH

s

FA

CH

DC

H

CC

CH

DC

CH

DT

CH

RA

CH

DC

H

HS

-DS

CH

E-D

CH

Rel

. 6

•MAC functionalities:- E-UTRAN MAC functions similar to UTRAN apart from the absence of functions related to dedicated transport channels-Reduction of different MAC entities (e.g. MAC-d not needed due to the absence of dedicated transport channels)


RLC Services and Functions

•AM, UM and TM transfer modes

•Error Correction through ARQ

•Segmentation/concatenation of SDUs according to the size of the TB

•When necessary, re-segmentation of PDUs that need to be retransmitted

The number of nested re-segmentations is not limited

• In-sequence delivery of upper layer PDUs except at HO in the Uplink

•Flow Control between eNB and UE (FFS)

•Other

Duplicate Detection

Protocol error detection and recovery

SDU discard

Reset


RRC States

RRC_CONNECTED(UE has an E-UTRAN-RRC connection; UE has context in E-UTRAN; E-UTRAN

knows the cell which the UE belongs to; Network can transmit and/or receive data to/from UE; Network controlled mobility (handover); Neighbour cell

measurements)

RRC_IDLE(UE specific DRX configured by NAS, Broadcast of system information, Paging, Cell re-selection mobility, The UE shall have been allocated an id which uniquely

identifies the UE in a tracking area, No RRC context stored in the eNB)

No RRC states (Cell_DCH, Cell_FACH, Cell_PCH, URA_PCH) in Connected Mode and only two macro RRC states


PDCP Services and Functions

•Header compression and decompression: ROHC only

•Transfer of user data

•In-sequence delivery of upper layer PDUs at HO in the uplink

•Security

• Ciphering termination is still under discussion in 3GPP

Integrity protection of control plane data (NAS signalling);

•PDCP header is 1 or 2 bytes

1 byte header used to optimize VoIP

PDCP

Integrity Protection

Ciphering Ciphering Ciphering

User PlaneNAS Data

Control PlaneNAS Signalling

ROHC ROHC

Ciphering

PDCP SDU (after compression)PDCP header

PDCP PDU


HARQ

N-process Stop-And-Wait HARQ is used

The HARQ is based on ACK/NACKs

In the downlink:

Asynchronous retransmissions with adaptive transmission parameters are supported

In the uplink:

HARQ is based on synchronous retransmissions

The HARQ transmits and retransmits interval 8 ms


HARQ/ARQ interactions

Multiplexing

...

HARQ

RACH

Scheduling / Priority Handling

Transport Channels

Logical Channels

MAC

RLC

PDCP

Segm.ARQ

Segm.ARQ

Logical Channels

Radio Bearers

ROHC ROHC

SAE Bearers

Ciphering Ciphering

Possible because RLC and MAC are co-located (unlike in HSPA Rel6)

In HARQ assisted ARQ operation, ARQ uses knowledge obtained from the HARQ about the transmission/reception status of a TB:

• If maximum HARQ retransmission limit is reached the ARQ is notified and retransmission can be initiated

• If the HARQ receiver is able to detect a NACK to ACK error it is FFS if the transmitting ARQ entities are notified

• If the HARQ receiver is able to detect TB transmission failure it is FFS if the receiving ARQ entities are notified


LTE A Technologies5


LTE-A Technologies

Support Wider BW – Carrier Aggregation

UL Access Scheme – SC-FDMA vs. OFDMA

MIMO extension – DL up to 8x8 and UL up to 4x4

CoMP (Coordinated Multi-Point Tx/Rx) –

Network MIMO

Coordinate MIMO

Macro Diversity Combining

Relay – L1/L2/L3 Relay

MBMS enhancement – non-SFN MBMS operation

Mobility enhancement – soft handover


Support of Wider BW – Carrier Aggregation

Support of contiguous and Non-contiguous carrier aggregation

Multiple component carriers with each component carrier up to 20 MHz BW

100 kHz channel raster as it is defined in R-8 & Asymmetrical UL/DL Alloc.

Reduced subcarriers between the component carriers

HARQ process – one TB and one HARQ per component carrier

DL Control Signaling – one per component or one for all

UL Control Signaling – Associated with HARQ design

Guard band= 2.6925 MHz

Frequency

18.015 MHz 18.015 MHz

18.3 MHz 18.3 MHz

18.015 MHz

19 sub-carriers(285 kHz)

19 sub-carriers(285 kHz)

Total bandwidth= 60 MHz

100-kHz channel raster


LTE-Advanced: MAC function per component carrier

TB Mapping -MAC to physical layer mapping and control signaling for carrier aggregation

Single Transport Block per antenna per component carrier Minimizing control signaling overhead – Ack/Nak Backward compatible to possibly support Rel-8 UE at each component

carrier

Channel coding

Modulation

RB mapping

Component carrier 1 Component carrier 2

20MHz 20MHz

transport block

Channel coding

Modulation

RB mapping

transport block


UL Transmission Scheme

OFDMA vs N x SC-FDMA

OFDMA has the performance advantage with diversity gain with the use of MLD decoding

N x SC-FDMA – minimizing the Cubic matrix (PAPR) with comparable performance with the use of interference cancellation

Agreed UL Transmission scheme

PUSCH transmission (MIMO and non-MIMO) uses DFT-precoding

On top of Rel-8 operation:

Control-data decoupling (simultaneous PUCCH and PUSCH transmission) supported in addition to TDM type multiplexing

Non-contiguous data transmission with single DFT per component carrier (CL-DFT-S-OFDM)

FFS: Resource allocation based on Rel-8 DL schemes (allocation type 0 and/or 1)

FFS: At most one new DCI format for non-MIMO


MIMO Configurations for MIMO extension and CoMP

MIMO

Single base Multiple bases(Network MIMO)

Co-locatedantennas

Distributed antennas

(RRH)

Non-coherent(Magnitude only)

Coherent(Magnitude/phase)

MacroscopicMIMO

SU-MIMOMU-MIMO

Beamforming

CollaborativeMIMO

-SU MIMO-MU MIMO

CoherentNetwork

MIMO-SU MIMO-MU MIMO

SU-MIMO,MU-MIMO

Beamforming


Extended Precoding

Combinations of Beamforming and Diversity Transmission

Beamforming for Multi-User Transmission (SDMA), based on closely spaced antenna elements (0.5 lambda)

Optimized codebooks for CoMP and MIMO extension

Download codebooks – reduce the number of stored codebook and entry expansion

Global codebook or Coordinate local codebooks for CoMP

Antenna Configuration - For up to 8 antenna elements in a 4x2 X-pol. configuration ( compact housing)

MIMO Evolution for MIMO extension and CoMP

MIMO channelBase-

station

data stream 1 / 2

data stream 3

MS 1

MS 2


Multiuser MIMO and scheduling for enhanced feedback mechanisms

• MU-MIMO enhancement –

•Principle of MU-MIMO – beamforming to each user with minimizing cross-interference

•DL Scheduler computation of pairing•UE feedback CQI/PMI + best companion PMI/ΔCQI

A

C

B

D

Beam-forming

User data

streams

Userselection

Channel state feedback

1 Users estimate channel and its companion with quantized feedback.

2 Base combine feedback from users and calculates beam weight to maximize sum rate while addressing fairness.

3 Data is transmitted.

MU-MIMO 1

2

3

1

2

3


Collaborative/Network MIMO overview

Coordinate transmission and reception of signals among multiple bases.

Reduces intercell interference and improves cell-edge performance and overall throughput.

Collaborative MIMO: share user data and long-term noncoherent channel information.

Coherent network MIMO: share user data and short-term coherent channel information.


Key technologies in Multi-mode Adaptive MIMO

Cellular system

Collaborative/Network MIMO MU-MIMO

SU-MIMO

SU-MIMO enhancement•Closed-loop MIMO•Iterative MIMO receiver

MU-MIMO optimization•MU precoding algorithm•Trade-off design of scheduler between complexity and performance

Collaborative/Network MIMO/Beam Coordination•Implementation of multi-BS collaboration with channel information

Multi-dimension adaptation•Adaptation strategy•Multi-variable channel measurement•Low-rate feedback mechanism

Multicast Anchor


Relay Technologies

Backhauling

Relay Node

Relay Node

Relay Node

Relay Node

Relay Node eNode

B

Types of Relay – L1 Relay – repeater or Amplify-and-forwardL2 Relay – decode-and-forward L3 Relay – IP packet forwarding

Characteristic of Relay associated with eNode BTransparent Relay – same Physical cell ID as eNBNon-transparent Relay – separate Physical cell ID as eNB


Design Issues in L2/L3 Relays

L3 Relay – Type 1 Relay agreed in LTE-A

TDM backhauling – using MBSFN subframe to support Rel-8 UEs

Reducing the complexity

L2 Relay Design issues

Benefit of L2 Relay in system performance - Early termination gain

Timing of HARQ operation in DL and UL

Resource coordination

Scheduling coordination between eNB and Relay Node

PDCCH Tx between eNB and Relay Node for DL Coordinated Relay

Interference mitigation with Relay Node

Power allocation and interference management from neighboring cell and Relay

RS design and UE Channel Estimation

Channel vector from RS with/o Relay Tx at different subframe


L3 Relay Use Cases

Characteristics of L3 Relay Separate Physical Cell ID – Backhauling through LTE-A air interface Relay Node has complete eNode B functions –

cell search, RACH, broadcast, DL/UL control, RRC control signaling, mobility management etc….

Inband Backhauling – Assumption of static radio link for backhauling for performance gain Data transport/Control signaling of combination support of S1 & X2 interface.

– Possible use of Macro eNode B to Home eNode B interface Cost effective alternatives – comparing to another eNB or RRH

Use Cases for L3 Relay with inband backhauling – extended coverage Remote rural area, isolation area (costly wireline backhaul) Remote island with reachable distance (under sea backhaul) Wireless PBX for corporate or small enterprise business (no leasing trunk) Historical districts (no allowance of new wiring) Wireless home eNB (no wireline backhauling) Moving objects - Train/Bus/Airplane (No cost effective alternatives) Temporary coverage – Olympics, special events, emergency events


L2 Relay Use Cases

Characteristics of L2 Relay

Same Physical Cell ID with donor eNB - Simplified RF/Baseband functions to enhance the cell edge throughput

Transparent Backhauling – Relay Node is considered an UE to the eNB with coordination of Tx/Rx and control signaling.

Cost effective alternatives – comparing to RRH Use Cases –

Enhancement of Cell edge coverage Remove the coverage hole Extended coverage at indoor environment - overcome bad RF reception

Improving cell edge throughput Enhanced the penetration in high rise building Hot spot area Campus environments Large Corporate Bus/Train stops and Airports Meeting/conference rooms Tunnels/Bridge/stadium


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LTE_Technical_Principles

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