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Radio systems, LTH2007-03-01 1

3G and Beyond: HSPA Evolution and LTE

Fredrik Florén

(?)

2007-03-01 Radio systems, LTH 2

Overview

• What is the 3GPP?

• 3GPP Timeline

• HSPA Evolution

– Receive Diversity and Equalizers

– HSDPA/HSUPA

– MIMO for HSDPA

– Higher-Order Modulation

– Continuous Packet Connectivity

• LTE

– Targets

– Technology

– Deployment?

• Summary


What is the 3GPP?

• The 3rd Generation Partnership Program is a collaboration of a number of national/regional standardization bodies

– ARIB (Japan)

– CCSA (China)

– ETSI (Europe)

– ATIS (USA)

– TTA (Korea)

– TTC (Japan)

• The 3GPP maintains and evolves

– GSM (GPRS, EDGE, GERAN Evolution)

– WCDMA

– LTE

– and their corresponding core networks


3GPP Timeline

• New versions of 3GPP standards are called releases

• Below only the main physical layer features are shown

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

Release ’99

3G

Release 4

Release 5

HSDPA

Release 6

HSUPA

Rx Div., Equaliz.

Release 7

MIMO

CPC

HoM

Rx Div. + Equaliz.

Release 8

LTE

MIMO+64QAM?


High Speed Packet Access Evolution


HSDPA

• High Speed Downlink Packet Access

– Adaptive modulation and coding

– Node-B scheduling

– Short transmission time interval

– Fast Hybrid ARQ

– No power control

– 16-QAM

– Peak rate: 14.4 Mbps

L1 retrans-

missions

Higher-

layer

trans-

mission

Rel ‘99 HSDPAt

SNR

R3

R2

R1


HSUPA

• High Speed Uplink Packet Access

– Fast Node-B uplink scheduling

– Fast Hybrid ARQ

– Optional short transmission time interval

– Long TTI needed for coverage

– Adaptive spreading factor

– Power control and soft handover retained


Scheduling

HARQ

Power control

Reordering


Receive Diversity and Equalizers

• Performance requirements defined for

– Two-antenna receive diversity (Type 1)

– Equalizer (Type 2)

– LMMSE chip-level

– GRake

– Receive diversity + equalizer (Type 3)

Receive diversity works

well in whole cellEqualizer only works well close to Node-B

t

h(t)

h(t)

h(t) g(t)

h(t)*g(t)

Tx Rx

Tx Rx

ISI

Intra-cell int.


MIMO for HSDPA

• Extension of the existing beamforming mode

• Dual-Stream Transmit Antenna Array (D-TxAA)

• Doubles peak rate to 28 Mbps

• For micro cell, 3 km/h, and 50% power to HSDPA (ref: 1x2 LMMSE)

– 20% gain in cell capacity

– 35%-50% gain in peak user throughput

– Non-linear receivers shown to give additional gain

De-

mux

EncodeChannel

Interlv

Modulator:

QPSK

16-QAM

…

EncodeChannel

Interlv

Modulator:

QPSK

16-QAM

…

v11

v21

v12

v22

To spreading

and first

antenna

To spreading

and second

antenna

High-rate

data stream

• Complexity

– Approximately 100% - 170% for 2x2 LMMSE compared to 1x2 LMMSE

– Non-linear receivers (SIC) require re-encoding

• Sectorization?

• Is it worth it?


Higher-Order Modulation

• HSDPA

– 16 QAM => 64 QAM

– Peak rate: 14.4 Mbps => 21.6 Mbps

– Simulations show ~15% peak user throughput gain

– In Release 8: MIMO + 64 QAM


• HSUPA

– QPSK => 16 QAM


• 64-QAM requires good accuracy when modulating

• Similarly to MIMO, good channels needed

• Marketing figures?


Continuous Packet Connectivity

• Bursty traffic is common

• Large delays occur when switching between active and idle mode

• In active mode, control channels required

• High control channel overhead for small packets, e.g., VoIP

• Goal

– Increase number of users in active mode

– Increase time spent in active mode

– Increase battery time

• Solution

– New control channel formats requiring less transmit power

– Discontinuous transmission and reception of control channels at UE

HS-SCCH,

F-DPCH

DPCCH,

CQI


Long Term Evolution


LTE High-Level Requirements [1]

• Ensure competitiveness in long-term, 10 years and beyond

• Low-latency

• High data rate

• Packet optimized

• Flexibe bandwidth support

• Possibility to use both existing and new frequency bands

• Reduced production cost

• Simplified architecture

• Reasonable system and terminal complexity, cost, and power consumption

• Optimized for low mobile speed but also support high mobile speed

– Optimized: 0-15 km/h

– High performance: 15-120 km/h

• Focus on cell radii up to 5 km[1] 3GPP TR 25.913, “Requirements for Evolved UTRA (E-UTRA)

and Evolved UTRAN (E-UTRAN)”


LTE Detailed Requirements

• Peak data rates (UE has 2 RX and 1 TX

antenna(s) )

– downlink: 100 Mbps

– uplink: 50 Mbps

• Spectrum allocations: 1.25 MHz, 1.6

MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz

and 20 MHz

• FDD (also half duplex) and TDD

t

f

t

f

t

f

f


Downlink

• Orthogonal Frequency Division Multiplexing (OFDM)

– Parallel Low-Rate Carriers (Sub-Carriers)

– Cyclic prefix

– Ensures orthogonality

– Avoids ISI

– OFDM efficiently realized with FFT

OFDM symbol

CP

IDF

T

P/S CP Channel CPD/AA/D

S/P

DF

T

Inpu

t D

ata

Sym

bols

Outp

ut D

ata

Sym

bols


Downlink, cont’d

• Three modes

– Short CP (4.7 us), 15 kHz subcarrier spacing

– Long CP (16.7 us), 15 kHz subcarrier spacing

– Very long CP (33 us), 7.5 kHz subcarrier spacing

• Small subcarrier spacing

– Long symbol => Channel changes

• Large subcarrier spacing

– Short symbol => Large overhead


• Time-frequency interpretation

• Subframe is delay-overhead trade-

off

• Reference signals

– MIMO

• Control channels

– Resource indication

– Transport format

– HARQ info

– Uplink grant

– Uplink ACK/NACK

• Synchronization & Broadcastsubframe = 1 ms

t

f

Downlink, cont’d

Control

Pilot

Data for

user #1

Data for

user #2


Downlink, cont’d

• Turbo decoding

– Contention-free quadratic polynomial

permutation (QPP) turbo code

internal interleaver

• HARQ

• Adaptive modulation

– QPSK, 16-QAM, 64-QAM

• Scheduler

Transport block (L2 PDU)

CRC attachment

Channel coding

HARQ functionality

including adaptive coding rate

Physical channel segmentation

(resource block mapping)

Adaptive modulation(common modulation is selected)

To assigned resource blocks

Number of assigned resource blocks

Resource

Block

Subframe

1 ms

180 kHz


MBMS

• Multimedia Broadcast Multicast Service

– Provides multimedia content to a number of subscribers

– Audio

– Video

– Stock quotes

– Etc…

• Same content in many cells

tt

t

• OFDM offers soft combining

– Transparent to UE

– Synchronization

• Greatly improves MBMS cell-edge

performance

• Multiplexing of unicast/MBMS


Uplink

• Single-Carrier Frequency Division Multiplexing (SC-FDMA)

– Low Peak to Average Power Ratio (PAPR)

– “Easy” to equalize channel due to CP

– Time-domain generation:

– Frequency-domain generation (DFT-Spread OFDM):

CPInput Data

SymbolsPulse

Shaping f

Input Data

Symbols

DFT

Mapping IFFT CP

DFT

User 1

User 2

Pulse

Shaping f


Uplink, cont’d

• CP: 4.7 us and 16.7 us

• Orthogonal multiple access

• Shared channel

• Time and frequency alignment

• Random access

t

f

subframe = 1 ms

• Data/Control multiplexing

• Slow power control

• Sounding pilot will also be needed

• QPSK, 16-QAM, 64-QAM (optional)

Data & control

User #1

Data & control

User #2

Control for users

not transmitting

data (CDM)

Pilots


MIMO

• Downlink

– Two or four transmit antennas and two or four receive antennas

– Spatial Multiplexing (SM)

– Up to four streams

– Codebook-based pre-coding

– Transmit Diversity (CDD/SFBC)

– Multiuser MIMO also supported

• Uplink

– Only multiuser MIMO supported

– Closed-loop transmit antenna selection (optional)

• Scheduler will be busy…

TX RX

TX/RX

TX/RX

TX/RX

Single-user MIMO

Multi-user MIMO


Interference Coordination

• Reuse one will work, but…

• Some claim interference coordination will be needed

– Fractional reuse

– Partial reuse

– Inverted reuse

– “Conventional” reuse

• Adaptive?

• Cancellation?


PSD

fF1 F2 F3

PSD

f

F1 F2 F3Fr


Persistent Scheduling

• LTE is packet switched

• How support VoIP?

• “Persistent scheduling”

– Statically allocate resources in pre-determined pattern

– Fixed delay

– No control overhead

– Fixed modulation and coding

Transmission instants according to persistent scheduling pattern

Transmission according to SCCH schedulingData

SCCH overhead

Data

SCCH overhead

time

fre

qu

ency

Transmission instants according to persistent scheduling pattern

Transmission according to SCCH schedulingData

SCCH overhead

Data

SCCH overhead

time

fre

qu

ency

• Circuit switched to packet switched to cirucuit switched?

• Circuit switched has its merits



LTE Detailed Requirements, cont’d

• Delay: <5 ms

• Throughputs (ref: Rel-6, Type 1)

– Downlink

– Mean user throughput: 3-4x

– Cell-edge througput: 2-3x

– Cell capacity: 3-4x

– Uplink

– User throughput: 2-3x

– Cell-edge throughput 2-3x

– Cell capacity: 2-3x

• Targets fulfilled?

– Fair comparison?

TX RX

Base Mobile

Rake

TXRX

3G/HSPA

RX

TXRX

LTE

TX


LTE Deployment

• Is a do-it-all, low-complexity system realistic?

• Applications

– Sit & work

– Stroll & surf

– Ride & surf

– Walk & talk

• Other radio accesses

– WLAN

– GSM/EDGE/GERAN Evolution

– 3G/HSPA

– DVB-h

– WiMAX

• Services requiring high bitrates in mobile systems?

– Terminals!

• How much are customers willing to pay?

– Flat rate


LTE Deployment, cont’d

• Few 3G/HSPA vendors

• Large interest in LTE among vendors

• Not all operators have investmented in 3G/HSPA

• LTE possibly suitable replacement/complement for

– 3G/HSPA

– GSM

• Simpler and cheaper

– Multi-mode terminals easier?

• Flexible spectrum allocation

• Migration paths

• Timing

– Typically 5 years stable core spec to prototype, another 2 years to certified mass market

– Terminal availability?

• Prioritization needed

• Core (SAE) and radio access network architecture must not be forgotten


Summary

• HSPA Evolution

– Enhancement of packet-data services

– MIMO

– Higher-order modulation

• LTE

– High peak data rates

– Low latency

– Flexible bandwidth operation

– OFDM-based

– MIMO

Radio systems, LTH2007-03-01 29

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