Basic LTE overview - LTE for indonesia

Ekstensi TelkomTelekomunikasi Unjani

Basic LTE OverviewLTE For Indonesia

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Jaringan Mobile & Ad-HOCProgram Studi Strata I Telekomunikasi

Jurusan Teknik Elektro

Disusun oleh :

M. Toenof Abdulghani 2212132073

Ekstensi TelkomTelekomunikasi Unjani 2

IntroductionsNetwork ArchitectureLTE TechnologyThroughput Calculation


Introductions

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2G & 3G Radio Technology Evolution

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Wireless Broadband Technology Evolution

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Towards to 4G

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NETWORK ARCHITECTURE

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4G Architecture

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EPC : Evolved Packet Core MME : Mobility Management Entity S-GW : Serving Gateway P-GW : PDN Gateway PDN : Packet Data Network eNB : E-UTRAN Node B / Evolved Node B E-UTRAN : Evolved-UTRAN


Logical High Level Architecture for The Evolved System

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LTE Technology

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FDMA TDMA CDMA and OFDMA

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OFDM

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OFDM

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Introduction

OFDM （Orthogonal Frequency Division Multiplexing） is a

modulation multiplexing scheme. The system bandwidth is divided

into a plurality of orthogonal.

Orthogonality of different subcarriers is achieved by the baseband

IFFT.

Available bandwidth is divided into several subchannels

Symbols are transmitted on different subcarriers

OFDM

OFDM has many advantages that can meet the needs of

E-UTRAN, which is one of B3G and 4G key technology.

OFDM is a modulation multiplexing scheme, and the

corresponding multi-access techniques is OFDMA.

OFDMA are used in LTE downlink.

For LTE uplink the multiple access scheme is SC-FDMA .

…

Sub-carriersFFT

Time

Symbols

System Bandwidth

Guard

Intervals

…

Frequency

…

Sub-carriersFFT

Time

Symbols

System Bandwidth

Guard

Intervals

…

Frequency


OFDM & OFDMA

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OFDM

• Semua subcarrier dialokasikan untuk satu user

OFDMA

• Subcarrier dialokasikan secara fleksibel untuk banyak user tergantung pada kondisi radio.


OFDM Concept: Mengapa OFDM

• Sinyal OFDM (Orthogonal Frequency Division Multiplexing) dapat mendukung kondisi NLOS (Non Line of Sight) dengan mempertahankan efisiensi spektral yang tinggi dan memaksimalkan spektrum yang tersedia.

• Mendukung lingkungan propagasi multi-path.

• Scalable bandwidth : menyediakan fleksibilitas dan potensial mengurangi CAPEX (capital expense).

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OFDMA time-frequency multiplexing

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OFDMA & SC-FDMA

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OFDM & OFDMA

OFDM (Orthogonal Frequency Division Multiplexing) is a modulation

multiplexing technology, divides the system bandwidth into orthogonal

subcarriers. CP is inserted between the OFDM symbols to avoid the ISI.

OFDMA is the multi-access technology related with OFDM, is used in the

LTE downlink. OFDMA is the combination of TDMA and FDMA essentially.

Advantage: High spectrum utilization efficiency due to orthogonal

subcarriers need no protect bandwidth. Support frequency link auto

adaptation and scheduling. Easy to combine with MIMO.

Disadvantage: Strict requirement of time-frequency domain

synchronization. High PAPR.

DFT-S-OFDM & SC-FDMA

DFT-S-OFDM (Discrete Fourier Transform Spread OFDM) is the

modulation multiplexing technology used in the LTE uplink,

which is similar with OFDM but can release the UE PA limitation

caused by high PAPR. Each user is assigned part of the system

bandwidth.

SC-FDMA（Single Carrier Frequency Division Multiple

Accessing）is the multi-access technology related with DFT-S-

OFDM.

Advantage: High spectrum utilization efficiency due to

orthogonal user bandwidth need no protect bandwidth. Low

PAPR.

The subcarrier assignment scheme includes Localized mode

and Distributed mode.

User 1

User 2

User 3

Sub-carriers

TTI: 1ms

Frequency

System Bandwidth

Sub-band：12Sub-carriers

Time

User 1

User 2

User 3

User 1

User 2

User 3

Sub-carriers

TTI: 1ms

Frequency

System Bandwidth


Time

Sub-carriers

TTI: 1ms

Frequency

Time

System Bandwidth


User 1

User 2

User 3

Sub-carriers

TTI: 1ms

Frequency

Time

System Bandwidth


User 1

User 2

User 3

User 1

User 2

User 3


LTE Uplink Transmission Scheme: SC-FDMA

• Pemilihan OFDMA dianggap optimum untuk memenuhi persyaratan LTE pada arah downlink, tetapi OFDMA memiliki properti yang kurang menguntungkan pada arah Uplink.

• Hal tsb terutama disebabkan oleh lemahnya peak-to-average power ratio (PAPR) dari sinyal OFDMA, yang mengakibatkan buruknya coverage uplink.

• Oleh karena itu, skema transmisi Uplink LTE untuk mode FDD maupun TDD didasarkan pada SC-FDMA, yang mempunyai properti PAPR lebih baik.

• Pemrosesan sinyal SC-FDMA memiliki beberapa kesamaan dengan pemrosesan sinyal OFDMA, sehingga parameter-parameter DL dan UL dapat diharmonisasi.

• Untuk membangkitkan sinyal SC-FDMA, E-UTRA telah memilih DFT-spread-OFDM (DFT-s-OFDM).

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Resource Block

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Adaptive Modulation and Coding

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2 bits per symbol in

each carrier.


each carrier.


each carrier.


MIMO ANTENNA• MIMO: Multiple input – multiple output

• Given an arbitrary wireless communication system:

”A link for which the transmitting end as well as the receiving end is equipped with multiple antenna elements”

• The signals on the transmit antennas and receive antennas are ”combined” to improve the quality of the communication (ber and/or bps)

• MIMO systems use space-time processing techniques

Time dimension is completed with the spatial dimension

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Multiple antenna fundamentals

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Throughput Calculation

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LTE UL/DL Throughput (MAC Layer) Calculation

• DL Throughput (MAC Layer) = (168-36-12)x (Code bits) x (Code rate) x Nrb x C x 1000 - CRC

• UL Throughput (MAC Layer) = (168-12) x (Code bits) x (Code rate) x Nrb x C x 1000 - CRC

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168 = Number of Resource Elemen (RE) in 1 ms.36 = Number of Control Channel RE in 1 ms.12 = Number of Refference Signal RE in 1 ms.CRC = 24 (fixed).Code Bits = number of bit per symbol, below :

QPSK = 216QAM = 464QAM = 6

Code Rate= ½, ¾, 5/6, etc. C = Refers to MIMO configuration

NO MIMO = 1MIMO 2x2 = 2

Nrb (Number of Resource Block) = Based on Bandwidth, can be seen from table below.20 Mhz, Nrb = 10015 Mhz, Nrb = 50


For Example• BW = 10 MHz

• Modulation & Coding Scheme = 64QAM5/6

• NO MIMO

DL Throughput (MAC Layer) = (168-36-12) x (Code bits) x (Code rate) x Nrb x C x 1000 – CRC

= (168-36-12) x 6 x 5/6 x 50 x 1 x 1000 – 24

= 29,999976 Mbps = 30 Mbps

• BW = 20 MHz


• NO MIMO


= (168-36-12) x 6 x 5/6 x 100 x 1 x 1000 – 24

= 59,999976 Mbps = 60 Mbps

• BW = 20 MHz


• MIMO 2*2


= (168-36-12) x 6 x 5/6 x 100 x 2 x 1000 – 24

= 119,999976 Mbps = 120 Mbps

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Reference

• LTE Internal Document by Huawei

• LTE Training material 4G RF Planning & Optimizationby Float Way Systems

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