LTE Aida Botonjić · 5% packet call throughput 64 Kbps DL 5 Kbps UL 3-4x DL / 2-3x UL improvement...

Aida Botonjić Tieto 1

LTE

Aida Botonjić


Why LTE?

• Applications:• Interactive gaming

• DVD quality video

• Data download/upload

• Targets:• High data rates at high speed

• Low latency

• Packet optimized radio access technology

• Goals:• Improving efficiency

• Lowering costs

• Reducing complexity

• Improving services

• Making use of new spectrum opportunities and better integration with other open

standards (such as WLAN and WiMAX)


November 2004, 3GPP Rel8: Long-term Evolution (LTE)

Related specifications are formally known as the evolved UMTS terrestrial radio access (E-UTRA) and evolved UMTS terrestrial radio access network (E-UTRAN)

LTE encompasses the evolution of:

- the radio access through the E-UTRAN

- the non-radio aspects under the term System Architecture Evolution (SAE)

Entire system composed of both LTE and SAE is called the

Evolved Packet System (EPS)

Introduction


IP Transport Network

Network Architecture

Cost efficient two node

architecture

Fully meshed approach with

tunneling mechanism over IP

network

Access gateway (AGW)

Enhanced Node B (eNB)

IP Service Network

S1

X2X2

X2X2

S1S1 S1

AGWAGW

eNB

eNB

eNB

eNB

eNB


Network Elements


Protocol overview

NAS

RRC

PDCP

RLC

MAC

PHY

UE

RRC

PDCP

RLC

MAC

PHY

eNB

NAS

MME

Handovers

Ciphering

Segmentation

HARQ

Modulation,

coding

NAS

RRC

PDCP

RLC

MAC

PHY

UE

RRC

PDCP

RLC

MAC

PHY

eNB

Control Plane User Plane

Radio bearers

Logical channels

Transport channels

Physical channels


Frame structure

#0 #1 #2 #3 #19

One slot, Tslot = 15360 Ts = 0.5 ms

One radio frame, Tf = 307200 Ts=10 ms

#18

One subframe

WCDMA/HSPA:

LTE:

#0 #1 #2 #3 #14

One slot, 2/3ms

One radio frame, 10 ms

#13

One subframe, 2ms


Channel Dependent Scheduling

and Link adaptation

Frequency-domain & Time-domain adaptation

Focus transmission power to each user’s best channel portion

Adaptive modulation (QPSK, 16QAM, 64QAM)


LTE PHY –

Main Technologies

MIMO

Multiple Input Multiple

Output

OFDM

Orthogonal Frequency

Division Multiplexing

NTx Transmit

Antennas

NRxReceive

Antennas


LTE PHY - MIMO Basics

Minimum antenna requirement: 2 at eNodeB 2 Rx at UE

Transmission of several independent data streams in parallel => increased data rate

The radio channel consists of NTx x NRx paths

Theoretical maximum rate increase factor = Min(NTx x NRx)


Sub-carriers are orthogonal

All the sub-carriers allocated to a given user

are transmitted in parallel.

The carrier spacing is 15kHz

LTE PHY - OFDM Basics


Requirement comparisonRequirement HSPA (Rel 6) LTE

Peak data rate 14 Mbps DL

5.76 Mbps UL

100 Mbps DL

50 Mbps UL

5% packet call throughput 64 Kbps DL

5 Kbps UL

3-4x DL / 2-3x UL

improvement

Averaged user throughput 900 Kbps DL

150 Kbps UL

3-4x DL / 2-3x UL

improvement

Control plane capacity > 200 users per cell (for

5MHz spectrum)

User plane latency 50 ms 5 ms

Call setup time 2 sec 50 ms

Broadcast data rate 384 Kbps 6-8x improvement

Mobility Up to 250 km/h Up to 350 km/h (500 km/h

for wider bandwidths)

Bandwidth 5 MHz 1.25, 2.5, 5, 10, 15, 20 MHz


Feature comparison

Feature HSPA (Rel 6) LTE

minimum TTI size 2 ms 1 ms

Modulation DL: QPSK, 16 QAM

UL: QPSK

DL: QPSK, 16 QAM, 64

QAM

UL: 16 QAM

HARQ Async DL,

Sync UL

Async DL,

Sync UL

Fast scheduling TDS (time domain) TDS and FDS (frequency

domain)


Conclusion

Scalable bandwidth

Downlink and uplink peak data rates are 100 and 50 Mbit/s respectively for 20 MHz bandwidth.

MIMO

OFDM

At least 200 mobile terminals in the active state for 5MHz bandwidth.If bandwidth is more than 5MHz, at least 400 terminals should be supported.

PHY key technologies enable higher spectral efficiency, peak rate and lower latency

LTE Aida Botonjić · 5% packet call throughput 64 Kbps DL 5 Kbps UL 3-4x DL / 2-3x UL improvement...

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