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LTE (Long Term Evolution)

Prof. Adel A. Ali

Abdurrahman A. Ashahrani

Hammod Al-Olyani

King Saud University

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Outline

Introduction & Background

What OFDM?

LTE

Conclusion

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First Generation MS

with its large size &

2G with its small size

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Introduction & Background

Analog Mobile Systems (first Generation)

Few users , expensive , large size

Second Generation (GSM)Digital system, more user, almost

voice, improved to supply data (EDGE , GPRS).

Third Generation (UMTS) Voice & data but, cell breathing (CDMA),

improved to increase the speed 7Mbps(HSPDA).

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Cell Breathing

20 Users 10 Users

-10 < C/I < -5 dB

-15 < C/I < -10 dB

-50 < C/I < -15 dB

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What OFDM ?

Subcarriers used.

The subcarriers are orthogonal to eachother and can be overlapped.

Suitable for multipath fading channels

and high data rates

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Ch.1

Ch.2 Ch.3 Ch.4 Ch.5 Ch.6 Ch.7 Ch.8 Ch.9 Ch.10

Ch.3 Ch.5 Ch.7 Ch.9

Ch.2 Ch.4 Ch.6 Ch.8 Ch.10

Ch.1

Conventional multicarrier techniques

Orthogonal multicarrier techniques OFDM

50% bandwidth saving

frequency

frequency

A

B

Traditional FDM Signal and OFDM

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All Sub carrier need to Orthogonal

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OFDM

Sub-carrier

CDMA

Signal

Channel Transfer Function

Frequency

S(f)

CDMA & OFDM in

Frequency-selective Channel

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LTE (Long Term Evaluation)

Supply Bandwidths from 1.25-20 MHz

Subcarriers spacing 15kHz.

Bit rate up to 100Mbps, and by using MIMO the

speed should reach 350Mbps !

SC-FDMA for U.L. & OFDM for D.L.

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20 MHz15 MHz10 MHz5 MHz2.5 MHz1.25 MHzTransmissionBW

0.5 msSub-frame

duration

15 kHzSub-carrier

spacing30.72

MHz

8 3.84

MHz

23.04 MHz

6 3.84

MHz

15.36 MHz

4 3.84

MHz

7.68

MHz

2 3.84

MHz

3.84

MHz

1.92 MHz

1/2 3.84

MHz

Sampling

frequency

204815361024512256128FFT size

4.694.694.694.694.694.69Sho

rtCP

Length

(s)

16.6716.6716.6716.6716.6716.67

Lo

ng

LTE modulation Specification

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LTE Time Line

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Thank you

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