Read Microsoft PowerPoint - LTE 2007-12-04 text version

LTE ­ Long-Term Evolution

Stefan Parkvall

3G Evolution

R99 Rel4 Rel5 Rel6 Rel7 Rel8




HSPA evolution


LTE LTE Advanced

HSPA evolution

­ gradually improved performance at a low additional cost in 5MHz spectrum allocation


­ ­

© Ericsson AB 2008

significantly improved performance in a wide range of spectrum allocations further evolved into IMT-Advanced

2 2007-12-04

LTE Key Features

Bandwidth flexibility

LTE physical-layer specification supports any bandwidth in the range 6 RBs to 110 RBs in steps of one RB (1 RB=12×15 kHz)

6 RB (1.1 MHz) 110 RB (20 MHz)

Dow nl ink ( DL)

Support for paired and unpaired spectrum allocations


fDL fUL Paired spectrum

© Ericsson AB 2008

Upli n

k (U L)

Half duplex FDD

fDL fUL Reduced UE complexity



fDL/UL Unpaired spectrum


Transmission Schemes

Downlink ­ OFDM

­ ­ ­ Broadcast, MIMO, ... Robustness, especially at high bandwidths Access to frequency domain

f1 f2 Terminal A fM

Uplink ­ SC-FDMA

­ Single-carrier small PA back-off improved coverage Scheduled TDMA/FDMA uplink intra-cell orthogonality



DFT (M1) 0


CP insertion

M1 > M 2

f = 15 kHz

Terminal B

0 DFT (M2) IDFT CP insertion

20 MHz (example)

© Ericsson AB 2008 5 2007-12-04

Channel-Dependent Scheduling

Shared channel transmission Select user and data rate based on instantaneous channel quality

­ Time-domain adaptation used already in HSPA

Scheduling in time and frequency domain

­ Link adaptation in time domain only

Time-frequency fading, user #1

Time-frequency fading, user #2

data1 data2 data3 data4

User #1 scheduled User #2 scheduled

1m s

Tim e

cy Frequen

180 kHz

© Ericsson AB 2008




Who said you were tired of abbreviations?

Multi-antenna support

­ ­ Integral part of LTE All terminals support 2 Rx antennas

TX Multi-layer transmission ("MIMO")

Hybrid ARQ

­ ­ Rapid retransmission, soft combining 8 ms HARQ RTT

Fast Retransmissions with Soft Combining


­ Multicast-Broadcast Single-Frequency Network

© Ericsson AB 2008



L1 Overview

IP packet

IP packet

User #i

User #j

SAE bearers PDCP


PDCP Header Compr. Header Compr.

Ciphering Radio Bearers MAC

Payload selection




RLC Segmentation, ARQ Logical Channels Concatenation, ARQ

Priority handling, payload selection Retransmission control

MAC MAC multiplexing Hybrid ARQ Hybrid ARQ Transport Channel PHY Coding + RM Coding PHY Coding + RM Decoding Data modulation Demodulation

Antenna and Antenna and resrouce mapping resource demapping

MAC demultiplexing Hybrid ARQ Hybrid ARQ

Redundanc y version

MAC scheduler

Modulation scheme Antenna and resource assignment

Data modulation Modulation

Antenna and Antenna and resrouce mapping resource mapping


© Ericsson AB 2008 9



Time-domain Structure

Frame structure type 1 for FDD (full and half duplex)

One radio frame (10 ms) = 10 subframes #0 #1 One subframe (1 ms) = two slots #9

Frame structure type 2 for TDD

­ Similar to FS1...but with a special subframe for DL-to-UL switch

One radio frame (10 ms) = 10 subframes #0 #1 Special subframe DwPTS GP Configurable

© Ericsson AB 2008 10 2007-12-04



Physical Resources

One frame (10 ms) One resource element One subframe (1 ms)

12 sub-carriers

One slot (0.5 ms) TCP Tu

Time domain structure:

­ ­ ­ 10 ms frame consisting of 10 Subframes of length 1 ms Each subframe consisting of 2 Slots of length 0.5 ms Each slot consisting of 7 OFDM symbols (6 symbols in case of extended CP)

© Ericsson AB 2008



Downlink Processing

CRC insertion (16 bit for BCH, 24 bit for DL-SCH)


1 or 2 transport transport blocksper TTI block per TTI


DL-SCH: Turbo w. QPP, extra CRC per code block BCH: tail-biting conv. code Rate matching, redundancy version generation per code block, circular buffer Transport-channel-specific scrambling using length-33 Gold sequences Modulation (QPSK, 16QAM, 64QAM)

Coding Coding HARQ HARQ Scrambling Scrambling


Modulation Modulation

er ay p. L a m

Mapping to transmission layers (for multi-layer transmission)

Precoding (for multi-rank transmission)

ePr ode c

Resource block mapping

Resource block mapping Resource block mapping

One subf ram e

© Ericsson AB 2008



Cell-specific reference signals

Single-antenna transmission

Time-domain position: In OFDM symbol #0 and #4 of each slots

­ ­ Symbol #0 and #3 in case of extended CP 3 subcarriers staggering between symbols

Frequency-domain position: Every 6th subcarriers

Reference symbol One slot (0.5 ms)

504 different Reference Signal Sequences

­ ­ Normal CP: 168 Pseudo-random sequences × 3 Orthogonal Sequences Extended CP: 504 Pseudo-random sequences

PDSCH-to-RS EPRE different (but known) in RS and non-RS OFDM symbols

© Ericsson AB 2008 13 2007-12-04

Downlink L1/L2 control signaling

To support DL-SCH and UL-SCH transmission Mapped to first NPDCCH OFDM symbols of each subframe

­ ­ NPDCCH=1, 2, 3 OFDM symbols TDM of data and control micro-sleep possible


(up to 3)

PCFICH ­ Physical Control Format Indicator Channel

­ Value of NPDCCH ACK/NAK of uplink transmission

PHICH ­ Physical Hybrid ARQ Indicator Channel


PDCCH ­ Physical Downlink Control Channel

­ Scheduling assignments, scheduling grants, ...

© Ericsson AB 2008



UL-SCH Processing

UL-SCH processing similar to DL-SCH

CRC Coding HARQ Scrambling Modulation

CRC insertion (24 bits) Rel 6 Turbo coding (with QPP interleaver) Rate matching, redundancy version generation UE-specific scrambling for interference randomization Modulation (QPSK, 16QAM, 64QAM)

To DFTS-OFDM modulation, including mapping to assigned frequency resource

© Ericsson AB 2008 15 2007-12-04


One subframe

One slot

One resource block (12 subcarriers)

One reference-signal symbol per slot (two per subframe)

­ In DFTS-OFDM symbol #3

RS bandwidth equals uplink resource-allocation size

­ NRB = 3 in example above

© Ericsson AB 2008



Uplink Control Signaling

Control on PUSCH (simultaneous data and control)

User #1

On es lot ( 0.5 m

User #2


On es ubfram e (1




Reference signal


Control on PUCCH (control only)

Total available uplink bandwidth

Slot #0 Slot #1

One subfram e (1


12 "sub-carriers" Uplink resources assigned for L1/L2 control signaling

© Ericsson AB 2008 17 2007-12-04

Uplink Scheduling

Uplink transport format controlled by eNodeB

­ No TFC selection in the UE


Buffer Scheduler Multiplexing Modulation, coding TF selection Buffer Scheduler Uplink channel quality



Downlink channel quality


Priority handling



Modulation, coding Multiplexing Buffer Buffer


© Ericsson AB 2008 18



UE Categories

Category DL peak rate UL peak rate Max DL mod Max UL mod Layers for spatial mux. 16QAM 1 ? 2 1 10 5 2 50 25 3 100 50 64QAM ? ? ? 64QAM 4 4 150 50 5 300 75

All UEs support 4 Tx antennas at eNodeB Soft buffer sizes under discussion MBMS is a separate capability FDD, HD-FDD and TDD are independent capabilities

© Ericsson AB 2008 19 2007-12-04

Work in 3GPP


RAN1 meetings held ~8 times a year

­ ­ Meetings run from Monday to Friday Held in various countries in Europe, North America, and Asia

Meeting schedule 2007

­ ­ ­ ­ ­ ­ ­ ­ ­ January 15-19, February 12-16, March 26-30, April 17-20, May 7-11, June 25-29, August 20-24, October 8-12, November 5-9, Sorrento, St Louis, St Juliens, Beijing, Kobe, Orlando, Athens, Shanghai Seoul Italy USA Malta China Japan USA Greece China Korea

© Ericsson AB 2008



© Ericsson AB 2008

100 120 20 40 60 80 0

Approval of the agenda Approval of the minutes from previous meetings Liaison statement handling Maintenance of Release 99 ­ Release 7 Evolved UTRA and UTRAN TDD Frame Structure Finalization of TS 36.211 Downlink reference signals Uplink reference signals Downlink Control Signalling Uplink Control Signalling

Typical RAN1 Meeting

Number of Contributions per Agenda Item

Approx 200 delegates attending and ~550 documents submitted...


Mapping of virtual resource blocks to physical resource blocks Bit scrambling sequences for UL/DL transmissions RACH Finalization of TS 36.212 Finalization of TS 36.213 Timing synchronization UL/DL Power Control Inter-cell Interference Coordination RACH timing and preamble sequence selection UE Procedures for downlink shared channel UE Procedures for uplink shared channel Finalization of TS 36.214 Finalization of TS 36.201 UE Categories Combination of Higher Order Modulation and MIMO in HSDPA (FDD) Enhanced Uplink for Cell_FACH State in FDD Study Item on Synchronized E-DCH


3GPP Status

LTE (Rel-8) almost completed L1 specifications frozen and under change control

­ Only "bug fixes" possible

Higher layers will mostly be frozen in March 2008 Around 3 years in 3GPP to complete LTE Core Specifications

­ ­ ­ Study item approved late 2004 Study item completed September 2006 Detailed specifcations (work item) ready late 2007/early 2008

© Ericsson AB 2008



Taking You Forward...

© Ericsson AB 2008




Microsoft PowerPoint - LTE 2007-12-04

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