Top Banner
3GPP – Long Term Evolution – A Technical Study 1 Mr. Vishal Pawar MITSOT
28
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: 3GPP – Long Term Evolution

3GPP – Long Term Evolution – A Technical Study

1

Mr. Vishal PawarMITSOT

Page 2: 3GPP – Long Term Evolution

Main Topics • Introduction to LTE• LTE Network Architecture• LTE Physical Layer • SC-FDMA• Channel Dependent Scheduling • Cognitive Radio for LTE RRM• Multiple antenna schemes in LTE • LTE-Advanced• Conclusion

2

Page 3: 3GPP – Long Term Evolution

Introduction to LTE

• 3GPP Long Term Evolution - the next generation of wireless cellular technology beyond 3G

• Initiative taken by the 3rd Generation Partnership Project in 2004

• Introduced in Release 8 of 3GPP

• Mobile systems likely to be deployed by 2010

3

Page 4: 3GPP – Long Term Evolution

Requirements to be met by LTEFast, Efficient, Cheap, Simple

• Peak Data Rates• Spectrum efficiency• Reduced Latency• Mobility• Spectrum flexibility• Coverage• Low complexity and cost• Interoperability• Simple packet-oriented E-UTRAN architecture

4

Page 5: 3GPP – Long Term Evolution

LTE Network Architecture

5

• Simple Architecture• Flat IP-Based Architecture• Reduction in latency and cost• Split between EPC and E-UTRAN• Compatibility with 3GPP and

non-3GPP technologies• eNB-radio interface-related

functions• MME-manages mobility, UE

identity and security parameters

• S-GW-node that terminates the interface towards E-UTRAN

eNB

MME / S-GW MME / S-GW

eNB

eNB

S1

S1

X2 E-UTRAN

Page 6: 3GPP – Long Term Evolution

LTE Network Architecture

6

Page 7: 3GPP – Long Term Evolution

June 26 2009 7

Page 8: 3GPP – Long Term Evolution

8

Page 9: 3GPP – Long Term Evolution

LTE Frame Structure

• LTE Frame Structure Type I (FDD)

9

Page 10: 3GPP – Long Term Evolution

LTE Frame Structure Type II (TDD)

June 26 2009 MITSOT_MCNE_LTE 10

Page 11: 3GPP – Long Term Evolution

Single-Carrier Frequency Division Multiple Access (SC-FDMA)

• Motivation for SC-FDMA

• SC-FDMA utilizes single carrier modulation at the transmitter and frequency domain equalization at the receiver.

• It has the best of both worlds - the low PAPR of single carrier systems and the multipath resistance and channel dependent subcarrier allocation features of OFDM.

• Same complexity and performance as OFDMA

11

Page 12: 3GPP – Long Term Evolution

The “SC”-”FDMA” System

DFT-Spread OFDMA – Mapping of spread symbols , not original symbols to subcarriers!!!

12

Page 13: 3GPP – Long Term Evolution

Subcarrier Mapping Schemes

• Localized (LFDMA)• Distributed (DFDMA)• Interleaved (IFDMA)

13

Page 14: 3GPP – Long Term Evolution

Frequency and Time Domain Representation

14

Frequency Time

Page 15: 3GPP – Long Term Evolution

Time domain signals of LFDMA, DFDMA and IFDMA[20]

15

Page 16: 3GPP – Long Term Evolution

PAPR characteristics of an SC-FDMA signal [20]

Comparison of the CCDF of PAPR for LFDMA, DFDMA, IFDMA and OFDMA

16

Page 17: 3GPP – Long Term Evolution

Effect of roll-off factor, alpha on the PAPR[20]

17

Page 18: 3GPP – Long Term Evolution

Why does SC-FDMA have a low PAPR?

• OFDMA • Parallel Transmission • Multi carrier structure• Increase in M => high PAPR• SC-FDMA • Serial Transmission• Each symbol represented by a wide signal – DFT spreads symbols over all subcarriers• PAPR not affected by increase in M

Both occupy the same bandwidth with same symbol durations

18

Page 19: 3GPP – Long Term Evolution

SC-FDMA in comparison with OFDMA and DS-CDMA/FDE

19

DS-CDMA/FDE

Page 20: 3GPP – Long Term Evolution

Channel Dependent Scheduling

• Channel is highly frequency selective

• Resources in deep fade for one user could be excellent for another user

• Frequency selectivity of the channel can be exploited by using CDS to maximize throughput

• LFDMA – frequency selective diversity

• IFDMA – Multi user diversity (inherently frequency diversity is obtained)

20

Page 21: 3GPP – Long Term Evolution

Cognitive RRM in LTE

• Link adaptation possible as network segments in LTE adapt to the environmental changes

• System can learn from solutions that were provided in the past

• Faster response, improved performance, intelligent system

• Decisions reg. apt BW,DSA,APA and AM

21

Page 22: 3GPP – Long Term Evolution

Cognitive Features to enhance RRM in LTE

22

Page 23: 3GPP – Long Term Evolution

Enhanced context acquisition mechanism architecture for cognitive intra-cell RRM

MITSOT_MCNE_LTE 23

Page 24: 3GPP – Long Term Evolution

Multiple Antenna Schemes in LTE

• In DL : Tx diversity, Rx diversity, Spatial multiplexing (2x2,4x2 configurations – SU-MIMO and MU-MIMO) supported

• In UL : Only 1 Transmitter (antenna selection Tx diversity ), MU-MIMO possible, Rx diversity with 2 or 4 antennas at eNB supported

24

Page 25: 3GPP – Long Term Evolution

LTE Advanced• LTE doesn’t fulfill the requirements of IMT-Advanced

• 3GPP has also started work on LTE-Advanced, an evolution of LTE, as a proposal to ITU-R for the development of IMT Advanced.

• LTE Advanced is envisioned to be the “first true 4G technology”.

25

Page 26: 3GPP – Long Term Evolution

Requirements of LTE Advanced

• Peak data rates – 1Gbps in DL and 500 Mbps in UL• Cell edge user data rates twice as high and average user throughput

thrice as high as in LTE• Peak spectrum efficiency DL: 30 bps/Hz, UL: 15 bps/Hz• Operate in flexible spectrum allocations up to 100 MHz and support

spectrum aggregation (as BW in DL >>20 MHz)• An LTE-Advanced capable network must appear as a LTE network

for the LTE UEs

26

Page 27: 3GPP – Long Term Evolution

Technological proposals for LTE Advanced

• Larger BW can be used for high date rates and more coverage at cell edges

• Advanced repeater structures• Relaying for adaptive coding

based on link quality

MITSOT_MCNE_LTE 27

Carrier aggregation and Spectrum aggregation

Page 28: 3GPP – Long Term Evolution

Thank You !

28