MIMO-OfDM System With Time Domain Interleaving

8/2/2019 MIMO-OfDM System With Time Domain Interleaving

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Presented ByRamakrishnan Mahadevan

Under Supervision of

Professor Bayan Sharif

School of Electrical, Electronic & Computer Engineering

MIMO-OFDM System with Time

Domain Interleaving


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Overview

MIMO

MIMO Systems

MIMO functions and applications

Orthogonal Frequency Division Multiplexing

OFDM system model

Applications of OFDM systems

MIMO-OFDM system

Block diagram of MIMO-OFDM system

Interleavers


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MIMO

Acronym for Multiple Input Multiple Output

Wireless technology using multiple antennas at both

transmitter and receiver to transfer more data.

Exploits the multipath effect to increase the

performance of the wireless system.

Smart antennas combine the data streams arriving at

the receiver from different paths.

Antennas use spatial diversity.

For better performance, both the mobile device andthe access point must support MIMO technology.


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MIMO SYSTEM

TRANSMITTER

TX

RECEIVER

RXCHANNEL


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MIMO Functions and Applications

Three main functions of MIMO Technology

Precoding

Spatial Multiplexing

Diversity Coding

Applications of MIMO Technology include :

WiMAX

Mobile radio telephony

High Speed Packet Access Plus (HSPA+)


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Orthogonal Frequency DivisionMultiplexing

A broadband multicarrier modulation scheme with superior

performance.

Different symbols are transmitted over different

subcarriers.

At the receiver there is a spectral overlap, but the signalsare still orthogonal.

Intersymbol interference is eliminated completely by

introducing guard time in each OFDM symbol.

Multipath delay spread is decreased as the symbol duration

increases with each subcarrier.


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OFDM SYSTEM MODEL

ENCODER MODULATOR IDFTCYCLIC

PREFIX

CHANNEL

REMOVE

CYCLIC

PREFIX

DFTDEMODULATORDECODER


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Applications of OFDM

Fixed /Wireline :

ADSL ( Asymmetric Digital Subcarrier Line )

Mobile/Radio :

Digital Audio Broadcasting (DAB)

Digital Video Broadcasting (DVB)

Wireless LAN

4G


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MIMO-OFDM SYSTEM System combining both MIMO and OFDM technique

to achieve greater spectral efficiency and data rate.

MIMO-OFDM systems transmits independent OFDMmodulated data from multiple antennassimultaneously.

At the receiver, the OFDM demodulation takes place.

MIMO decoder on each sub-channel extracts the datafrom all the transmit antennas on all the sub-channels.

MIMO-OFDM systems improves the three important

parameters of a wireless link : speed, range andreliability.


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Block Diagram of MIMO-OFDM

System

Transmitter section of MIMO-OFDM system

ENCODERS/ P

Converter

MODULATOR IDFT INTERLEAVER

MODULATOR

MODULATOR

IDFT

IDFT

INTERLEAVER

INTERLEAVER


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Channel and Receiver section of MIMO-OFDM System

CHANNEL

DEINTERLEAVER

DEINTERLEAVER

DEINTERLEAVER

DFT

DFT

DFT

DEMOD

DEMOD

DEMOD

P/ S DECODER


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Applications

MIMO-OFDM systems finds applications in all of

todays wireless technology :

Wi-fi

Wireless LANs

Cordless VoIP

Home entertainment systems

4G


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INTERLEAVERS

They are used to arrange data in a random fashion in

order to improve performance of the system.

Interleavers spread the noise burst over many

symbols, which is essential for decoder to perform

better error correction at the receiver. Interleavers are generally random or infinite and are

useful to de-correlate the noise samples which are

practically correlated.

De-interleavers perform the opposite function to that

of interleavers.


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Disadvantages of Interleavers

Interleaving when performed for an OFDM system has

two main impacts :

In an OFDM system, if interleaving is performed after

IDFT function, then the spectrum of the OFDM signal

is affected. The spectrum of the signal looses itssteepness.

When the samples of the OFDM symbols are changed,

the orthogonality of the subcarriers is affected.


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THANK YOU

MIMO-OfDM System With Time Domain Interleaving

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