Lt e Overview

8/9/2019 Lt e Overview

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3GPP R8 LTE Overview

조봉열, Bong Youl (Brian) Cho

[email protected]

Intel Corporation

mailto:[email protected]:[email protected]


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LTE/MIMO표준기술 2

Books on LTE


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Books on LTE – cont’d


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Contents

LTE Overview LTE Radio Interface Architecture

LTE Downlink Transmission

LTE Uplink Transmission Summary


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LTE Overview


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Terminology

LTE (Long Term Evolution)Evolution of 3GPP Radio Access Technology

E-UTRA

SAE (System Architecture Evolution)

Evolution of 3GPP Core Network Technology

EPC (Evolved Packet Core)

EPS (Evolved Packet System)

Evolution of the complete 3GPP UMTS Radio Access, Packet

Core and its integration into legacy 3GPP/non-3GPP networks

E-UTRAN + EPC


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3GPP LTE

LTE focus is on:

enhancement of the Universal Terrestrial Radio Access (UTRA) optimisation of the UTRAN architecture

With HSPA (downlink and uplink), UTRA will remain highly competitive forseveral years

LTE project aims to ensure the continued competitiveness of the 3GPP

technologies for the future (started at Nov. 2004) Motivations

Need for PS optimized system Evolve UMTS towards packet only system

Need for higher data rates Can be achieved with HSDPA/HSUPA and/or new air interface defined by 3GPP LTE

Need for high quality of services Use of licensed frequencies to guarantee quality of services Always-on experience (reduce control plane latency significantly)

Reduce round trip delay

Need for cheaper infrastructure Simplify architecture, reduce number of network elements

Most data users are less mobile


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Detailed Requirements* Peak data rate

Instantaneous downlink peak data rate of 100 Mb/s within a 20 MHz downlinkspectrum allocation (5 bps/Hz)

Instantaneous uplink peak data rate of 50 Mb/s within a 20MHz uplink spectrum

allocation(2.5 bps/Hz)

Control-plane latency

Transition time of less than 100 ms from a camped state, such as Release 6Idle Mode, to an active state such as Release 6 CELL_DCH

Transition time of less than 50 ms between a dormant state such as Release 6

CELL_PCH and an active state such as Release 6 CELL_DCH

Control-plane capacity

At least 200 users per cell should be supported in the active state for spectrum

allocations up to 5 MHz User-plane latency

Less than 5 ms in unload condition (ie single user with single data stream) for

small IP packet

* 3GPP TR 25.913, Technical Specification Group RAN: Requirements for EvolvedUTRA (E-UTRA) and Evolved UTRAN (E-UTRAN), Release 8, Version 8.0.0, Dec. 2008


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Detailed Requirements Average user throughput

Downlink: average user throughput per MHz, 3 to 4 times Release 6 HSDPA Uplink: average user throughput per MHz, 2 to 3 times Release 6 Enhanced Uplink

Cell edge user throughput

Downlink: user throughput per MHz at 5% of CDF, 2 to 3 times Release 6 HSDPA

Uplink: user throughput per MHz at 5% of CDF, 2 to 3 times Release 6 Enhanced Uplink

Spectrum efficiency

Downlink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 3 to 4times Release 6 HSDPA )

Uplink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 2 to 3 timesRelease 6 Enhanced Uplink

Mobility

E-UTRAN should be optimized for low mobile speed from 0 to 15 km/h

Higher mobile speed between 15 and 120 km/h should be supported with highperformance

Mobility across the cellular network shall be maintained at speeds from 120 km/h to 350km/h (or even up to 500 km/h depending on the frequency band)

Coverage

Throughput, spectrum efficiency and mobility targets above should be met up to 5 kmcells, and with a slight degradation up to 30 km cells. Cells range up to 100 km shouldnot be precluded.


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Detailed Requirements Spectrum flexibility

E-UTRA shall operate in spectrum allocations of different sizes, including 1.25 MHz, 2.5MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz in both the uplink and downlink. Operation

in paired and unpaired spectrum shall be supported

Co-existence and Inter-working with 3GPP RAT (UTRAN, GERAN)

Architecture and migration

Single E-UTRAN architecture

The E-UTRAN architecture shall be packet based, although provision should be madeto support systems supporting real-time and conversational class traffic

E-UTRAN architecture shall support an end-to-end QoS

Backhaul communication protocols should be optimized

Radio Resource Management requirements

Enhanced support for end to end QoS

Support of load sharing and policy management across different Radio AccessTechnologies

Complexity

Minimize the number of options

No redundant mandatory features


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LTE System Performance

Peak Data Rate

150.8

302.8

51.0

75.4

1) ~14% reference signal overhead (4 Tx antennas in DL)

~10% common channel overhead (1 UE/subframe)

~7% waveform overhead (CP)

~10% guard band

~(1/1) code rate2) ~14% reference signal overhead (1 Tx antenna in UL)

~0.6% random access overhead

~7% waveform overhead (CP)

~10% guard band

~(1/1) code rate

1)

2)


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LTE System Performance – cont’d

Downlink Spectral Efficiency

Uplink Spectral Efficiency


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LTE Key Features Downlink: OFDMA (Orthogonal Frequency Division Multiple Access)

Less critical AMP efficiency in BS side Concerns on high RX complexity in terminal side

Uplink: SC-FDMA (Single Carrier-FDMA)

Less critical RX complexity in BS side

Critical AMP complexity in terminal side (Cost, power Consumption, UL coverage)

Single node RAN (eNB)

Support FDD (frame type 1) & TDD (frame type 2 for TD-SCDMA evolution) H-FDD MS

User data rates

DL (baseline): 150.8 Mbps @ 20 MHz BW w/ 2x2 SU-MIMO

UL (baseline): 75.4 Mbps @ 20 MHz BW w/ non-MIMO or 1x2 MU-MIMO

Radio frame: 10 ms (= 20 slots), Sub-frame: 1 ms (= 2 slots), Slot: 0.5 ms

TTI: 1 ms

HARQ

Incremental redundancy is used as the soft combining strategy

Retransmission time: 8 ms

Modulation

DL/UL data channel = QPSK/16QAM/64QAM

Hard handover-based mobility

Making MS cheap asmuch as possible bymoving all the burdens

from MS to BS


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LTE Key Features – cont’d MIMO SM (Spatial Multiplexing), Beamforming, Antenna Diversity

Min requirement: 2 eNB antennas & 2 UE rx antennas

DL: Single-User MIMO up to 4x4 supportable, MU-MIMO

UL: MU-MIMO

Resource block

12 subcarriers with subcarrier BW of 15kHz “180kHz”

24 subcarriers with subcarrier BW of 7.5kHz (only for MBMS)

Subcarrier operation

Frequency selective by localized subcarrier

Frequency diversity by distributed subcarrier & frequency hopping

Frequency hopping

Intra-TTI: UL (once per 0.5ms slot), DL (once per 66us symbol)

Inter-TTI: across retransmissions

Bearer services

Packet only – no circuit switched voice or data services are supported

Voice must use VoIP or CS-Fallback

MBSFN

Multicast/Broadcast over a Single Frequency Network

To support a Multimedia Broadcast and Multicast System (MBMS)

Time-synchronized common waveform is transmitted from multiple cells for a given duration

The signal at MS will appear exactly as a signal transmitted from a single cell site and subject to multi-path

Not only “improve the received signal strength” but also “eliminate inter-cell interference”


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Resource & Channel Estimation in OFDM

Time-frequency grid

Time-frequency grid with known reference symbols


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E-UTRAN Architecture*

eNB

MME / S-GW MME / S-GW

eNB

eNB

S 1

S 1

S 1

S 1

X2

X 2X 2

E-UTRAN


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Functional Split b/w E-UTRAN and EPC*

internet

eNB

RB Control

Connection Mobility Cont.

eNB Measurement

Configuration & Provision

Dynamic Resource

Allocation (Scheduler)

PDCP

PHY

MME

S-GW

S1

MAC

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 addressallocation

Packet Filtering


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Security KeyReceiver

AuthenticationRelay

Base StationHandoverFunction

Service FlowManagement

RRC

BSPMIP Client

AAA Client

Authenticator

Location Register

Idle-Mode & Paging Control

DHCPProxy/Relay

Service FlowAuthenticator

Security KeyDistributor

ASN GW

WiMAX R3

WiMAX R6

Data Path Function/FA

WiMAX

Control Functions(Similar to 3GPP MME)

WiMAXData-Path Functions

(Similar to 3GPP S-GW)

WiMAX R4

CSN

ASN

Compare with WiMAX ASN-GW


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EPS is all PS (IP) based

* Qualcomm

2G initial

architecture

(GSM)

(1991)

2G+3G

architecture

(GPRS/EDGE/UMTS)

(2000)

IMS

Introduction

(2004)

EPS

architecture

(2008)

3GPP A hit t E l ti


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3GPP Architecture EvolutionTowards Flat Architecture

* NSN


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Duplexing

FDD

TDD


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LTE Modulation Schemes


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UE-eNB Communication Link

“Single and same link of communication for DL and UL”

DL serving cell = UL serving cell

No UL nor DL macro-diversity

Hard handover-based mobility

- UE assisted (based on measurement reports) and network controlled

(explicit handover command) by default

- During handover, UE uses a RACH-based mobility procedure to access

the target cell

- Handover is initiated by the UE when it detects a Radio Link failure

condition

Load indicator for inter-cell load control and interference coordination- Transmitted over X2 interface


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OFDMA: Interference Coordination

Cell-A

Cell-B

Cell-C

A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3 C4 A5

B5 C5

A1 A2 A3 A4 B3 B4 C1 C2 C3 C4 A5 B5 C5

C2 C3 C4 C5

P o w e r

B2

C1

A5 A4 B5B4 A3 A2 A1 B3B2B1

good users weak users

good user weak user

weak users good users

B1


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ICIC* in LTE Standards Inter-cell interference coordination (ICIC)

To aid downlink ICIC Relative narrowband transmission-power indicator

A cell can provide this information to neighboring cells, indicating the part of the

bandwidth where it intends to limit the transmission power. A cell receiving the indication

can schedule its downlink transmissions within this band, reducing the output power or

completely freeing the resources on complementary parts of the spectrum

To aid uplink ICIC

High interference indicator

The high-interference indicator provides information to neighboring cells about the part of

the cell bandwidth upon which the cell intends to schedule its cell-edge users. Because

cell-edge users are susceptible to inter-cell interference, upon receiving the high-

interference indicator, a cell might want to avoid scheduling certain subsets of its own

users on this part of the bandwidth.

Overload indicator

The overload indicator provides information on the uplink interference level experienced

in each part of the cell bandwidth. A cell receiving the overload indicator may reduce the

interference generated on some of these resource blocks by adjusting its scheduling

strategy


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OFDMA: Frequency Selective Gain

Loading gain by “frequency selective scheduling”

Localized subcarrier assignment Distributed subcarrier assignment


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Multi-cell Broadcast in OFDM System

Broadcast vs. Unicast transmission

Equivalence between simulcast transmission and multi-path propagation


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E-UTRA Frequency Band*

* 3GPP TS 36.101, E-UTRA: UE radio transmissionand reception, Release 9, V9.0.0, June 2009

Korea?

Korea?

Japan, Korea?

Europe?

China?

US?

China?


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LTE Spectrum Fragmentation


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E-UTRA Channel Bandwidth*

1RB = 180kHz 6RBs = 1.08MHz, 100RBs = 18MHz

6RBs (72 subcarriers) with 128 FFT, 100RBs (1200 subcarriers) with 2048 FFT

* 3GPP TS 36.101, E-UTRA: UE radio transmissionand reception, Release 9, V9.0.0, June 2009


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OFDM Parameters


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LTE Radio Interface Architecture


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LTE Protocol Architecture (DL)


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PDCP and RLC

PDCP

Header compression and corresponding decompression

Ciphering and deciphering

Integrity protection and verification

RLC

Transferring PDUs from higher layers, i.e. from RRC or PDCP

Error correction with ARQ, concatenation/segmentation, in-sequence

delivery and duplicate detection

Protocol error handling (e.g. signalling error)


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EPS Bearer Service Architecture


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EPS Bearer Terminology

Quality of service

GBR bearer: Guaranteed bit rate

Non-GBR bearer: No guaranteed bit rate

Establishment time

Default bearer

Established when UE connects to PDN

Provides always-on connectivity Always non-GBR

Dedicated bearer established later

Can be GBR or non-GBR

Every EPS bearer

QoS class identifier (QCI): This is a number which describes the error rate and

delay that are associated with the service.

Allocation and retention priority (ARP): This determines whether a bearer can be

dropped if the network gets congested, or whether it can cause other bearers to be

dropped. Emergency calls might be associated with a high ARP, for example.


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QCI (QoS Class Identifier)


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Logical Channels: “type of information it carries”

Control Channels

Broadcast Control Channel (BCCH)used for transmission of system information from the network to all UEs in a cell

Paging Control Channel (PCCH)

used for paging of UEs whose location on cell level is not known to the network

Common Control Channel (CCCH)

used for transmission of control information in conjunction with random access, i.e.,

used for UEs having no RRC connection Dedicated Control Channel (DCCH)

used for transmission of control information to/from a UE, i.e., used for UEs havingRRC connection (e.g. handover messages)

Multicast Control Channel (MCCH)

used for transmission of control information required for reception of MTCH

Traffic Channels

Dedicated Traffic Channel (DTCH)

used for transmission of user data to/from a UE

Multicast Traffic Channel (MTCH)

used for transmission of MBMS services


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Transport Channels: “how”, “with what characteristics”

Downlink

Broadcast Channel (BCH) A fixed TF

Used for transmission of parts of BCCH, so called MIB

Paging Channel (PCH)

Used for transmission of paging information from PCCH

Supports discontinuous reception (DRX)

Downlink Shared Channel (DL-SCH)

Main transport channel used for transmission of downlink data in LTE

Used also for transmission of parts of BCCH, so called SIB

Supports discontinuous reception (DRX)

Multicast Channel (MCH) Used to support MBMS

Uplink

Uplink Shared Channel (UL-SCH) Uplink counterpart to the DL-SCH

Random Access Channel(s) (RACH)

Transport channel which doesn’ t carry transport blocks

Collision risk


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DL Physical Channels Physical Downlink Shared Channel (PDSCH)

실제 downlink user data를전송하기위한 transport channel인 DL-SCH와 paging정보를전송

하기위한 transport channel인 PCH가매핑 동적방송정보인 SI (System Information)값들도 RRC메시지형태로 DL-SCH를통해전송되므로이역시 PDSCH로매핑이경우는전체셀영역으로도달될수있는능력이요구되기도함

Physical Broadcast Channel (PBCH)

UE가 cell search과정을마친후에최초로검출하는채널로서,다른물리계층채널들을수신하기위하여반드시필요한기본적인시스템정보들인 MIB (Master Information Block)를전송하

기위한 transport channel인 BCH가매핑 Physical Multicast Channel (PMCH)

방송형데이터를전송하기위한 transport channel인 MCH가매핑

Physical Control Format Indicator Channel (PCFICH)

매 subframe마다전송, only one PCFICH in each cell

Informs UE about CFI which indicates the number of OFDM symbols used for PDCCHstransmission

Physical Downlink Control Channel (PDCCH) Informs UE about resource allocation of PCH and DL-SCH

HARQ information related to DL-SCH

UL scheduling grant

Physical HARQ Indicator Channel (PHICH)

Carries HARQ ACK/NACKs in response to UL transmission


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UL Physical Channels

Physical Uplink Shared Channel (PUSCH)

Uplink counterpart of PDSCH

Carries UL-SCH

Physical Uplink Control Channel (PUCCH)

Carries HARQ ACK/NAKs in response to DL transmission

Carries Scheduling Request (SR)

Carries channel status reports such as CQI, PMI and RI At most one PUCCH per UE

Physical Random Access Channel (PRACH)

Carries the random access preamble


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LTE Channel Mapping

Downlink

Uplink


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WCDMA DL Channel Mapping

BCCH PCCH CCCH DCCH CTCH DTCH

BCH(DL)

PCH(DL)

RACH(UL)

FACH(DL)

DSCH(DL)

CPCH(UL)

DCH(UL&DL)

P- CCPCH S- CCPCH PRACH PDSCH PCPCH DPDCHSCH,CPICH,AICH,

PICH,DPCCH

Logical Ch

Transport Ch

Physical Ch

Control Plane User Plane


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BCCH and PCH on PDSCH

* Qualcomm


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LTE Downlink Transmission


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Frame Structure: Type 1 for FDD

where, Ts = 1/(15000 x 2048) seconds “the smallest time unit in LTE ”

Tf = 307200 x Ts = 10 ms

#0 #1 #2 #3 #19

One slot, T slot = 15360T s = 0.5 ms

One radio frame, T f = 307200T s=10 ms

#18

One subframe


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Frame Structure: Type 2 for TDD

One slot,T slot=15360T s

GP UpPTSDwPTS

One radio frame, T f = 307200T s = 10 ms

One half-frame, 153600T s = 5 ms

30720T s

One subframe,

30720T s

GP UpPTSDwPTS

Subframe #2 Subframe #3 Subframe #4Subframe #0 Subframe #5 Subframe #7 Subframe #8 Subframe #9


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Frame Structure: FDD/TDD


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DL Slot Structure

: Downlink bandwidth configuration,

expressed in units of

: Resource block size in the

frequency domain, expressed as a

number of subcarriers

: Number of OFDM symbols in andownlink slot

RBsc N

RBsc N

DLRB N

DLsymb N

DLsymb N OFDM symbols

One downlink slot slotT

0l 1DLsymb N l

R B

s c

D L R B

N

N

s u b c a r r i e r s

R B

s c

N


RBsc

DLsymb N N

Resource block

resource elements

Resource element ),( l k

0k

1RBscDLRB N N k

The minimum RB the eNB uses for LTEscheduling is “1ms (1subframe) x 180kHz(12subcarriers @ 15kHz spacing)”


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Definitions Resource Grid

Defined as subcarriers in frequency domain and OFDM symbols in time domain The quantity depends on the DL transmission BW configured in the cell and shall fulfill

The set of allowed values for is given by TS 36.101, TS 36.104

Resource Block (1 RB = 180 kHz)

Defined as “consecutive” subcarriers in frequency domain and “consecutive” OFDMsymbols in time domain

Corresponding to one slot in the time domain and 180 kHz in the frequency domain

Resource Element

Uniquely defined by the index pair in a slot where and

are the indices in the frequency and time domain, respectively

1106 DLRB N

RB

sc

DL

RB N N

DL

symb N

RB

sc N

l k ,

DL

RB N

DL

RB N

DL

symb N

1,...,0 DLsymb N l 1,...,0RB

sc

DL

RB N N k


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Normal CP & Extended CP


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Resource Blocks Allocation

* Award Solutions

( G)


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Resource-element groups (REG)

Basic unit for mapping of PCFICH,

PHICH, and PDCCH

Resource-element groups are used

for defining the mapping of control

channels to resource elements.

Mapping of a symbol-quadruplet

onto a resource

-element group is defined such that

elements are mapped to resource

elements of the resource-element

group not used for cell-specific

reference signals in increasing orderof l and k

)3(),2(),1(),( i z i z i z i z

)(i z

),( l k

n + 0

n + 1

n + 2

n + 3

n + 4

n

+ 5

n

+ 6

n

+ 7

n + 0

n + 1

n + 2

n + 3

n + 4

n + 5

n + 6

C


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DL Physical Channel Processing

scrambling of coded bits in each of the code words to be transmitted on aphysical channel

modulation of scrambled bits to generate complex-valued modulation symbols

mapping of the complex-valued modulation symbols onto one or severaltransmission layers

precoding of the complex-valued modulation symbols on each layer for

transmission on the antenna ports mapping of complex-valued modulation symbols for each antenna port to

resource elements

generation of complex-valued time-domain OFDM signal for each antenna port

OFDM signal

generationLayer

Mapper

Scrambling

Precoding

Modulation

Mapper

Modulation

Mapper

Resource

element mapper OFDM signal

generationScrambling

code words layers antenna ports

Resource

element mapper

Ch l C di


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Channel Coding

Turbo code

PCCC (exactly the same as in WCDMA/HSPA)

QPP (quadratic polynomial permutation) interleaver

M d l ti


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0 0 0

0 0 1

0 1 1

0 1 0

1 1 0

1 1 1

1 0 1

1 1 1

000 001 011 010 110 111 101 111

64-QAM

0 1

0

1

QPSK

00 01 11 10

00

01

11

10

16-QAM

Modulation

PDSCH, PMCH: QPSK, 16QAM, 64QAM

PBCH, PCFICH, PDCCH: QPSK

PHICH: BPSK on I/Q

DL L M i d P di


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DL Layer Mapping and Precoding

Explained in MIMO session

DL OFDM Si l G ti


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DL OFDM Signal Generation

OFDM Parameters

N = 2048 for

f=15kHzN = 4096 for f=7.5kHz

Check with resource block parameters

(160+2048) x Ts = 71.88us

(144+2048) x Ts = 71.35us

71.88us + 71.35us x 6 = 0.5ms

Normal Cyclic Prefix = 160 Ts = 5.2 usNormal Cyclic Prefix = 144 Ts = 4.7 usExtended Cyclic Prefix = 512 Ts = 16.7 usExtended Cyclic Prefix for MBMS = 1024 Ts = 33.3 us

s,CP0 T N N t l


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DL Physical Channels & Signals

Physical channels

Physical Downlink Shared Channel (PDSCH) Physical Broadcast Channel (PBCH)

Physical Multicast Channel (PMCH)

Physical Control Format Indicator Channel (PCFICH)

Physical Downlink Control Channel (PDCCH)

Physical HARQ Indicator Channel (PHICH)

Physical signals

Reference Signals

Cell-specific RS, associated with non-MBSFN transmission

Aid coherent detection (pilot)

Reference channel for CQI from UE to eNB

MBSFN RS, associated with MBSFN transmission

UE-specific RS

Synchronization Signals

Carries frequency and symbol timing synchronization

PSS (Primary SS) and SSS (Secondary SS)

Equivalent Channel/Signal Mapping


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q g pp g

Across Different Systems

LTE WCDMA/HSPA WiMAX

PDSCH HS-PDSCH, SCCPCH DL Data Burst

PBCH PCCPCH DCD, Preamble

PMCH DL Data Burst

PCFICH FCH

PDCCH HS-SCCH, E-AGCH,

E-RGCH

DL-MAP, UL-MAP

PHICH E-HICH DL Data Burst

Cell-specific

Reference Signal

CPICH Pilot Signal (common)

UE-specific Reference

Signal

With secondary

scrambling code

Pilot Signal (dedicated)

Sync Signal SCH Preamble

DL R f Si l


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DL Reference Signals

Cell-specific reference signals

Are transmitted in every downlink subframe, and span entire cell BW Used for coherent demodulation of any downlink transmission “except” when so-

called non-codebook-based beamforming is used

Used for initial cell search

Used for downlink signal strength measurements for scheduling and handover

Using antenna ports {0, 1, 2, 3}

MBSFN reference signals

Used for channel estimation for coherent demodulation of signals being transmitted

by means of MBSFN

Using antenna port 4

UE-specific reference signals

Is specifically intended for channel estimation for coherent demodulation of DL-SCHwhen non-codebook-based beamforming is used.

Are transmitted only within the RB assigned for DL-SCH to that specific UE

Using antenna port 5

* Antenna port is different from physical antenna. One designated RS per antenna port.


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Cell-Specific Reference Signals

When estimating the channel for a certain RB, UE may not only use the

reference symbols within that RB but also, in frequency domain, neighbor

RBs, as well as reference symbols of previously received slots/subframes

Pseudo-random sequence generation

is the slot number within a radio frame.

is the OFDM symbol number within the slot.

The pseudo-random sequence c(i) is a length-31 Gold sequence.

The complex values of cell-specific reference symbols is based on length-31

Gold pseudo-random sequence. The length-31 Gold psuedo-randomsequence is generated with the seed, based on the slot number, symbol

number, cell identity, and cyclic prefix type.

12,...,1,0 ,)12(212

1)2(21

2

1)( DLmax,RB, s N mmc jmcmr nl


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Cell-Specific Reference Signals – cont’d

While the sequence itself if 231-1

bits in length, the number of bits

from the sequence selected for

transmission is based on the largest

channel bandwidth, which is

currently 20 MHz.

* Qualcomm

C


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Relationship with Cell Identity

504 unique Cell ID:

168(N1) Cell ID groups, 3 (N2) Cell ID within each group

Cell ID = 3xN1+N2 = 0 ~ 503 index

504 pseudo-random sequences

One to one mapping between the Cell ID and Pseudo-random sequences

Cell-specific Frequency Shift (N1 mod 6)

1 RE shift from current RS position in case of next Cell ID index

Each shift corresponds to 84 different cell identities, that is 6 shifts jointly cover all

504 cell identities.

Effective with RS boosting to enhance reference signal SIR by avoiding the collision

of boosted RSs from neighboring cells (assuming time synchronization)


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MBSFN RS Mapping


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MBSFN RS Mapping

MBSFN RS Mapping


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MBSFN RS Mapping

UE ifi RS t f C ll ifi RS


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UE-specific RS on top of Cell-specific RS

UE-specific RS (antenna port 5)

12 symbols per RB pair DL CQI estimation is always based on cell-specific RS (common RS)

Cell ID with PSS & SSS


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Cell ID with PSS & SSS

504 unique physical-layer cell identities

168 unique physical-layer cell-identity groups (0~167)

3 physical-layer identity within physical-layer cell-identity group (0~2)

Primary SS (PSS) and Secondary SS (SSS)

SSS (Cell ID Group)

PSS (Cell ID index

within a Group)

Physical Layer Cell ID

• • •

0 1 2• • •

0 1 2

0 1 2 3 … 167• • • • •

• • •

0 1 2

• • • • • • • • •

0 1 2 3 4 5 501 502 503



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SS is using single antenna port

However, SS can be with UE-transparent transmit antenna scheme (e.g.PVS, TSTD, CDD)

Primary SS (PSS) and Secondary SS (SSS)

0.5ms slot

Primary Synchronization Signal


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Primary Synchronization Signal The sequence used for the primary synchronization signal is generated from a frequency-

domain Zadoff-Chu sequence (Length-62)

For frame structure type 1, PSS is mapped to the last OFDM symbol in slots 0 and 10

No need to know CP length

The sequence is mapped to REs (6 RBs) according to

Cell ID detection within a cell ID group (3 hypotheses)

Half-frame timing detection (Repeat the same sequence twice)

61,...,32,31

30,...,1,0)(

63

)2)(1(

63

)1(

ne

nend

nnu j

nun j

u

61,...,0 ,1 ,2

31 , DLsymb

RBsc

DLRB

, n N l N N

nk nd a l k

Secondary Synchronization Signal


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Secondary Synchronization Signal The sequence used for the second synchronization signal is an interleaved concatenation

of two length-31 binary sequences (X and Y)

The concatenated sequence is scrambled with a scrambling sequence given by PSS

The combination of two length-31 sequences defining SSS differs between slot 0 (SSS1)

and slot 10 (SSS2) according to

where

Blind detection of CP-length (2 FFT operations are needed)

The same antenna port as for the primary sync signal

Mapped to 6 RBs

5subframein)(

0subframein)()12(

5subframein)(

0subframein)()2(

)(11

)(0

)(11)(1

0)(

1

0)(

0

10

01

1

0

n z ncn s

n z ncn snd

ncn s

ncn snd

mm

mm

m

m

300 n

Synchronization Signals cont’d


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Synchronization Signals – cont d Cell ID group detection (the set of valid combination of X and Y for SSS are 168)

Frame boundary detection (the m-sequences X and Y are swapped b/w SSS1 and SSS2)

Structure of SSS


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Structure of SSS

LTE Cell Search


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LTE Cell SearchPrimary SSSymbol timing acquisition

Frequency synchronizationCell ID detection within a cell group ID (3hypotheses)Half-frame boundary detection

Secondary SSCell group ID detection (168 hypotheses)

Frame boundary detection (2 hypotheses)CP-length detection (2 hypotheses)

BCH40ms BCH period timing detection

eNB # of tx antenna detectionMIB acquisition (Operation BW, SFN, etc…)

PCFICH PDCCH reception

SIB acquisition within PDSCH

Map Cell ID to cell-specific RS

Random access with PRACH

PCFICH


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PCFICH

The number of OFDM symbols used for control channel can be varying per TTI

CFI (Control Format Indication) Information about the number of OFDM symbols (1~4) used for transmission of PDCCHs in a

subframe

PCFICH carries CFI

2 bits 32 bits (block coding) 32 bits (cell specific scrambling) 16 symbols (QPSK) Mapping to resource elements: 4 REG (16 RE excluding RS) in the 1st OFDM symbol

Spread over the whole system bandwidth

To avoid the collisions in neighboring cells, the location depends on cell identity

Transmit diversity is applied which is identical to the scheme applied to BCH

PCFICH Processing


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PCFICH Processing

PHICH


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PHICH

HARQ ACK/NAK in response to UL transmission

HI codewords with length of 12 REs = 4 (Walsh spreading) x 3 (repetition) 3 groups of 4 contiguous REs (not used for RS and PCFICH)

BPSK modulation with I/Q multiplexing

SF4 x 2 (I/Q) = 8 PHICHs in normal CP

Cell-specific scrambling

Tx diversity, the same antenna ports as PBCH

Typically, PHICH is transmitted in the first OFDM symbol only

For FDD, an uplink transport block received in subframe n should be acknowledged on the

PHICH in subframe n+4

PHICH Processing


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PHICH Processing

PCFICH/PHICH RE Mapping

symbol


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PCFICH/PHICH RE Mapping

S u b c ar r i er

Example for 5 MHz BW LTE

PDCCH


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PDCCH PDCCH is used to carry DCI where DCI includes;

Downlink scheduling assignments, including PDSCH resource indication, transport

format, HARQ-related information, and control information related to SM (if

applicable).

Uplink scheduling grants, including PUSCH resource indication, transport format, and

HARQ-related information.

Uplink power control commands

DL assignment

Regular unicast data – RB assignment, transport block size, retransmission sequence

number

Scheduling of paging messages – acts as a “PICH”

Scheduling of SIBs

Scheduling of RA responses

UL power control commands UL grant

Regular unicast data

Request for aperiodic CQI reports

Power control command, cyclic shift of DM RS

PDCCH DCI Format


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PDCCH DCI Format

DCIFormats

Usage Details

0 UL grant For scheduling of PUSCH

1

DLassign-ment

For scheduling of one PDSCH codeword (SIMO, TxD)

1AFor compact scheduling of one PDSCH codeword (SIMO, TxD) andrandom access procedure initiated by a PDCCH order

1BFor compact scheduling of one PDSCH codeword with precoding

information (CL single-rank)1C

For very compact scheduling of one PDSCH codeword (paging, RACHresponse and dynamic BCCH scheduling)

1DFor compact scheduling of one PDSCH codeword with precoding &power offset information

2 For scheduling PDSCH to UEs configured in CL SM

2A For scheduling PDSCH to UEs configured in OL SM

3Powercontrol

For transmission of TPC commands for PUCCH/PUSCH with 2-bitpower adjustment

3AFor transmission of TPC commands for PUCCH/PUSCH with single bitpower adjustment

Downlink Assignment


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Downlink Assignment

Major contents of different DCI formats: not exhaustive

DCI format 0/1A indication [1 bit]

Distributed transmission flag [1 bit]

Resource-block allocation [variable]

For the first (or only) transport block

MCS [5 bit]

New-data indicator [1 bit]

Redundancy version [2 bit]

For the second transport block (present in DCI format 2 only) MCS [5 bit]

New-data indicator [1 bit]

Redundancy version [2 bit]

HARQ process number [3 bit for FDD]

Information related to SM (present in DCI format 2 only) Pre-coding information [3 bit for 2 antennas, 6 bit for 4 antennas in CL-SM]

Number of transmission layer

HARQ swap flag [1 bit]

Transmit power control (TPC) for PUCCH [2 bit]

Identity (RNTI) of the terminal for which the PDCCH transmission is intended [16 bit]


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System Information


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System Information Master information block (MIB) includes the following information:

Downlink cell bandwidth [4 bit]

PHICH duration [1 bit]

PHICH resource [2 bit]

System Frame Number (SFN) except two LBSs

Etc…

LTE defines different SIBs:

SIB1 includes info mainly related to whether an UE is allowed to camp on the cell. This includes info about the

operator(s) and about the cell (e.g. PLMN identity list, tracking area code, cell identity, minimum required Rx

level in the cell, etc), DL-UL subframe configuration in TDD case, and the scheduling of the remaining SIBs.

SIB1 is transmitted every 80ms.

SIB2 includes info that UEs need in order to be able to access the cell. This includes info about the UL cell

BW, random access parameters, and UL power control parameters. SIBs also includes radio resource

configuration of common channels (RACH, BCCH, PCCH, PRACH, PDSCH, PUSCH, PUCCH, and SRS).

SIB3 mainly includes info related to cell-reselection.

SIB4-8 include neighbor-cell-related info. (E-UTRAN, UTRAN, GERAN, cdma2000)

SIB9 contains a home eNB identifier

SIB10/11 contains ETWS (Earthquake and Tsunami Warning System) notification

More to be added

MIB mapped to PBCH

Other SIBs mapped to PDSCH

BCH on PBCH


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BCH on PBCH To broadcast a certain set of cell and/or system-specific information

Requirement to be broadcast in the entire coverage area of the cell

BCH transmission

The coded BCH transport block is mapped to four subframes (slot #1 in subframe #0)within a 40ms interval

40ms timing is blindly detected (no explicit signaling indicating 40ms timing)

Each subframe is assumed to be self-decodable, i.e. the BCH can be decoded from asingle reception, assuming sufficiently good channel conditions

BCH on PBCH – cont’d


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BCH on PBCH cont d Single (fixed-size) transport block per TTI (40 ms)

No HARQ

Cell-specific scrambling, QPSK with ½ tail-biting Conv. Code, Tx diversity(1,2,4)

BCH mapped to 4 OFDM symbols within a subframe in time-domain at 6 RBs

(72 subcarriers) excluding DC in freq-domain

PBCH is mapped into RE assuming RS from 4 antennas are used at eNB,

irrespective of the actual number of TX antenna

Different transmit diversity schemes per # of antennas

# of ant=2: SFBC

# of ant=4: SFBC + FSTD (Frequency Switching Transmit Diversity)

No explicit bits in the PBCH to signal the number of TX antennas at eNB

PBCH encoding chain includes CRC masking dependent on the number of

configured TX antennas at eNB Blind detection of the number of TX antenna using CRC masking by UE

PBCH Processing


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PBCH Processing

LTE Cell Search


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LTE Cell SearchPrimary SSSymbol timing acquisition

Frequency synchronizationCell ID detection within a cell group ID (3hypotheses)Half-frame boundary detection

Secondary SSCell group ID detection (168 hypotheses)Frame boundary detection (2 hypotheses)CP-length detection (2 hypotheses)

BCH40ms BCH period timing detection

eNB # of tx antenna detectionMIB acquisition (Operation BW, SFN, etc…)





LTE Cell Search – cont’d*


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LTE Cell Search cont d

PSS/SSS, BCH, (RACH)

1.4

3


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Resource Block Allocations


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Resource Block Allocations

Localized allocation

Distributed allocation „Simple bitmap‟ whose size is equal to the number of RBs of the system

Merit: The most flexible signaling of resource block allocation

Demerit: High overhead

Not used in LTE

LTE has 3 resource allocation type Type0: grouped bitmap

Type1: grouped bitmap, enable 1 RB allocation

Type2: VRB/PRB for localized & distributed


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Resource Allocation Type2


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Resource Allocation Type2

Does not rely on a bitmap

Basically „frequency-contiguous‟ allocation Using VRB to PRB mapping, distributed allocation can be enabled

2 values

Start: a RIV (resource indication value) defines the index of the starting VRB

Length: length of virtually contiguously allocated resource blocks

5MHz LTE example


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DVRB


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Virtual resource blocks of distributed type are mapped to PRBs as follows

Consecutive VRBs are not mapped to PRBs that are consecutive in the frequency domain

Even a single VRB pair is distributed in the frequency domain

The exact size of the frequency gap depends on the overall downlink cell BW

Resource Allocation Overhead


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DL Frame Structure Type 1


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yp


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LTE Uplink Transmission

UL Slot Structure One uplink slot slotT


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U S ot St uctu e : Uplink bandwidth configuration,

expressed in units of

: Resource block size in the

frequency domain, expressed as a

number of subcarriers

: Number of SC-FDMA symbols in

an uplink slot

RB

sc N

RBsc N

ULRB N

ULsymb N

ULsymb N SC-FDMA symbols

0l 1ULsymb N l

R B

s c

U L R B

N

N


R B

s c

N


RBsc

ULsymb N N

Resource block

resource elements

Resource element ),( l k

0k

1RBscULRB N N k


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Equivalent Channel/Signal Mapping



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LTE WCDMA/HSPA WiMAX

PUSCH (E-DPDCH) UL Data Burst

PUCCH HS-DPCCH CQICH, ACKCH,

BW Request

Ranging

PRACH PRACH Initial Ranging

Demodulation RS (E-DPCCH) Pilot Signal

Sounding RS Sounding Signal


UL Reference Signals


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g

UL RS should preferably have the following properties:

Favorable auto- and cross-correlation properties

Limited power variation in freq-domain to allow for similar channel-estimation quality for allfrequencies

Limited power variation in time-domain (low cubic metric) for high PA efficiency

Sufficiently many RS sequences of the same length to avoid an unreasonable planning effort

Zadoff-Chu Sequence

Appeared in IEEE Trans. Inform. Theory in 1972

Poly-phase sequence Constant amplitude zero auto correlation (CAZAC) sequence의일종

Cyclic autocorrelations are zero for all non-zero lags, Non-zero cross-correlations

Constant power in both the frequency and the time domain

No restriction on code length N

- Sequence number p is relatively prime to N

- Sequence length: N

- Number of sequences: N -1

,

,)(

)1(2

2 2

n pn N

j

pn N

j

p

e

en g

when N is even

when N is odd

DRS


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DRS is made from Z-C sequence*, and the DRS sequence length is the same

with the number of subcarriers in an assigned RBs DRS is defined with the following parameters

Sequence group (30 options): cell specific parameter

Sequence (2 options for sequence lengths of 6PRBs or longer): cell specific

parameter

Cyclic shift (12 options): both terminal and cell specific components Sequence length: given by the UL allocation

Typically,

Cyclic shifts are used to multiplex RSs from different UEs within a cell.

Different sequence groups are used in neighboring cells.

DRS Location within a Subframe


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DRS for PUSCH

Normal CP적용시

PUSCH RS는한슬롯당중앙의

SC-FDMA심볼에위치

Extended CP적용시 PUSCH RS는한슬롯당 3번째 SC-FDMA 심볼에위치

DRS for PUCCH

Format 1x

Format 2x

SRS


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LTE/MIMO표준기술

110

기지국이각단말의상향링크채널정보를추정할수있도록단말이전송하는 RS

Reference for channel quality information

CQ measurement for frequency/time aware scheduling

CQ measurement for link adaptation

CQ measurement for power control

CQ measurement for MIMO

Timing measurement

Reference signal sequence is defined by a cyclic shift of a base sequence (ZC)

SRS전송주기/대역폭은 각단말마다고유하게할당

From as often as once in every 2ms to as infrequently as once in every 160ms (320ms)

At least 4 RBs

SRS는서브프레임의마지막

SC-FDMA심볼로전송

SRS multiplexing by

Time, Frequency, Cyclic shifts, and transmission comb (2 combs distributed SC-FDMA)

To avoid the collision b/w SRS and PUSCH transmission from other UEs, SRS

transmissions should not extend into the frequency band reserved for PUCCH.

nr nr vu)(

,SRS RSsc,

)(, 0),()( M nnr enr vu

n jvu

SRS – cont’d


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111

Non-frequency-hopping (wideband) SRS and frequency-hopping SRS

Multiplexing of SRS transmissions from different UEs


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CQI


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113

CQI Table

MCS where transport block could be received with transport block error rate 0.1

*Note that there are many more

possibilities for MCS and TBS size

values than 15 indicated by CQIfeedback.

Reported CQI is calculated assuming the particular RI value

CQI is a function of frequency, time, and space

CQI index Modulation Coding rate x 1024 Bits per RE

0 Out of range

1 QPSK 78 0.1523

2 QPSK 120 0.2344

3 QPSK 193 0.3770

4 QPSK 308 0.6016

5 QPSK 449 0.8770

6 QPSK 602 1.1758

7 16QAM 378 1.4766

8 16QAM 490 1.9141

9 16QAM 616 2.4063

10 64QAM 466 2.7305

11 64QAM 567 3.3223

12 64QAM 666 3.9023

13 64QAM 772 4.523414 64QAM 873 5.1151

15 64QAM 948 5.5547


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UL L1/L2 control signaling on PUCCH


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115

The reasons for locating PUCCH resources at the edges of the spectrum

To maximize frequency diversity

To retain single-carrier property Multiple UEs can share the same PUCCH resource block

Format 1: length-12 orthogonal phase rotation sequence + length-4 orthogonal cover

Format 2: length-12 orthogonal phase rotation sequence

PUCCH is never transmitted simultaneously with PUSCH from the same UE

2 consecutive PUCCH slots inTime-Frequency Hopping at the slotboundary

PUCCH Formats


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116

PUCCH

format

Modulation

scheme

Number of bits

per subframe Usage

Multiplexing

capacity(UE/RB)

1 N/A N/A SR 36, 18*, 12

1a BPSK 1 ACK/NACK 36, 18*, 12

1b QPSK 2 ACK/NACK 36, 18*, 12

2 QPSK 20 CQI 12, 6*, 4

2a QPSK+BPSK 21 CQI + ACK/NACK 12, 6*, 4

2b QPSK+QPSK 22 CQI + ACK/NACK 12, 6*, 4

* Typical value with 6 different rotations (choosing every second cyclic shift)

PUCCH Format 2/2a/2b is located at the outermost RBs of system BW

ACK/NACK for persistently scheduled PDSCH and SRI are located next

ACK/NACK for dynamically scheduled PDSCH are located innermost RBs

PUCCH Resource Mapping


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117

Format 1

4 symbols are modulated by BPSK/QPSK

BPSK/QPSK symbol is multiplied by a length-4 orthogonal cover sequence (a length-3orthogonal cover when there is SRS), and then it modulates the rotated length-12sequence.

Reference signals also employ one orthogonal cover sequence PUCCH capacity: up to 3 x 12 = 36 different UEs per each cell-specific sequence

(assuming all 12 rotations being available Practically, only 6 rotations.)

Format 2

5 symbols are modulated by QPSK after being multiplied by a phase rotated length-12cell specific sequence.

Resource consumption of one channel-status report is 3x of HARQ acknowledgement

PUCCH Format1 Processing


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118

PUCCH Format2 Processing


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119

PUSCH Processing


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120


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Hopping based on cell-specific patterns


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LTE/MIMO표준기술122

Subbands are defined

In 10 MHz BW case, the overall UL BW corresponds to 50 RBs and there are a total of 4 subbands, each consisting

of 11 RBs. The remaining 6 RBs are used for PUCCH transmission.

The resource defined by a scheduling grant (VRBs) is not the actual set of RBs for transmission.

The resource to use for transmission (PRBs) is the resource provided in the scheduling grant “shifted” a

number of subbands according to a cell-specific hopping pattern.

More on hopping w/ cell-specific patterns


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Example for predefined hopping for PUSCH with 20 RBs and M=4

(subband hopping + mirroring)


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UL SC-FDMA Signal Generation


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This section applies to all uplink physical signals and physical channels

except the physical random access channel SC-FDMA parameters

where N = 2048

Check with numbers in Table 5.2.3-1. {(160+2048) x Ts} + 6 x {(144+2048) x Ts} = 0.5 ms

6 x {(512+2048) x Ts} = 0.5 ms

s,CP0 T N N t l

PRACH


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PRACH는 RA과정에서단말이기지국으로전송하는 preamble이다

6RB를차지하며부반송파간격은 1.25kHz (format #4는 7.5kHz)

64 preamble sequences for each cell 64 random access opportunities per PRACH resource Sequence부분은길이 839의 Z-C sequence로구성 (format #4는길이 139)

Phase modulation: Due to the ideal auto-correlation property, there is no intra-cell interference from multiple

random access attempt using preambles derived from the same Z-C root sequence.

Five types of preamble formats to accommodate a wide range of scenarios

Higher layers control the preamble format

일반적환경 (~15km)

넓은반경의셀환경과같이시간지연이긴경우 (~100km)

SINR이낮은상황을고려하여 sequence repetition (~30km)

SINR이낮은상황을고려하여 sequence repetition (~100km)

TDD모드용

Different Preamble Formats


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PRACH Location


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One PRACH resource of 6 RBs per subframe (for FDD)

Multiple UEs can access same PRACH resource by using different preambles PRACH may or may not present in every subframe and every frame

PRACH-Configurat ion-Index parameter indicates frame number and subframe numbers

where the PRACH resource is available.

Starting frequency is specified by the network ( )

No frequency hopping for PRACH

LTE Cell Search & Random Access


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Primary SSSymbol timing acquisitionFrequency synchronizationCell ID detection within a cell group ID (3hypotheses)Half-frame boundary detection

Secondary SSCell group ID detection (168 hypotheses)Frame boundary detection (2 hypotheses)

CP-length detection (2 hypotheses)

BCH40ms BCH period timing detectioneNB # of tx antenna detectionMIB acquisition (Operation BW, SFN, etc…)





UL Frame Structure Type 1*


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1 RB

UL 16QAM SC-FDMA


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* Agilent


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Summary

E-UTRA UE Capabilities*


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Final Message** Signals Ahead


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Lt e Overview

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