Modul 7 Konsep Dasar Multiple Antena

Wireless Communication System

Modul 7 Konsep Dasar Multiple Antena

Faculty of Electrical Engineering Bandung – 2015 Modul 7 Multiple Antenna

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Subject

a. Macam-macam Multiple Antenna (Diversitas dan MIMO) b. Model Sistem SISO, SIMO, MISO, MIMO

Modul 7 Multiple Antenna

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Text Book


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Multiple Antenna vs Fading

Rina P. Astuti

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Diversity & MIMO


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Multiple Antenna Technique: Four Basic Model


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SISO

Radio transmissions traditionally use one antenna at the transmitter and one antenna at the receiver. This system is termed Single Input Single Output (SISO). Both the transmitter and the receiver

Picture. Single Input Single Output (SISO) One antenna at both the transmitter and the receiver. Employs no diversity technique. Modul 7 Multiple Antenna

have one RF chain (that's coder and modulator). SISO is relatively simple and cheap to implement and it has been used age long since the birth of radio technology. It is used in radio and TV broadcast and our personal wireless technologies (e.g. Wi-Fi and Bluetooth).

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SIMO

To improve performance, a multiple antenna technique has been developed. A system which uses a single antenna at the transmitter and multiple antennas at the receiver is named Single Input Multiple Output (SIMO). The receiver can either choose the best antenna to receive a stronger signal or combine signals from all antennas in such a way that maximizes SNR (Signal to Noise Ratio). The first technique is known as switched diversity or selection diversity. The latter is known as maximal ratio combining (MRC).

Picture. Single Input Multiple Output (SIMO), 1x2 One antenna at the transmitter, two antennas the receiver. Employs a receive diversity technique. Modul 7 Multiple Antenna

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MISO

A system which uses multiple antennas at the transmitter and a single antenna at the receiver is named Multiple Input Single Output (MISO). A technique known as Alamouti STC (Space Time Coding) is employed at the transmitter with two antennas. STC allows the transmitter to transmit signals (information) both in time and space, meaning the information is transmitted by two antennas at two different times consecutively.

Picture. Multiple Input Single Output (MISO), 2x1 Two antennas at the transmitter, one antenna at the receiver. Employs a transmit diversity technique. Modul 7 Multiple Antenna

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MIMO

To multiply throughput of a radio link, multiple antennas (and multiple RF chains accordingly) are put at both the transmitter and the receiver. This system is referred to as Multiple Input Multiple Output (MIMO). A MIMO system with similar count of antennas at both the transmitter and the receiver in a point-to-point (PTP) link is able to multiply the system throughput linearly with every additional antenna. For example, a 2x2 MIMO will double the throughput.

Picture. Multiple Input Multiple Output (MIMO), 2x2 Two antennas at both the transmitter and the receiver. Modul 7 Multiple Antenna

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18 

Objective : to support private and public access – – –

high data rate transmission high mobility High signal performance

Selective fading Costly to estimate the channel accurately Performance degradation Multi users

Problems

New transmission techniques

Multiple antennas & multi-carrier techniques Non coherent transmission scheme Coding techniques Multiple access

Examples : OFDM, Coded OFDM, OFCDM, MC-CDMA

Differential modulation outer & inner coding FDMA, TDMA, CDMA

19 Rina P. Astuti

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Modern Wireless Transceiver


20 c 1 ,

b1, .... , b t  Data Source

.... , c t

 Signal

Channel Encoder

Modulator

Fading Channel



ˆ ˆ b 1 ,...., b t

cˆ 1 ,...., cˆ t 



Estimated Data

AWGN Noise

Channel Decoder

Demodulator

Signal

CHANNEL CHANNEL

s1,1, .... , s t,1

Modulator

b1, .... , b t  Data Source

c 1 , .... , c t 

Constellation/Mapper

C M Symbols T

C symbols Space Time Encoder

TX Antenna 1

Channel Encoder TX Antenna 2

s1,2 , .... , s t,2 

Outer Coding Inner Coding

bˆ 1 ,...., bˆ t  Estimated Data

cˆ 1,...., cˆ t 

Demapper

Space Time Decoder

Rina Pudji Astuti

sˆ 1,1 ,...., sˆ t,1 Channel & Noise Covariance Estimator

C symbols

RX Antenna 1 h12 RX Antenna 2 h21 h22

C M Symbols T

Channel Decoder

Outer Decoding

h11

sˆ 1,2 ,...., sˆ t,2 

AWGN Noise Localized Noise

r1,2

,...., r t,2

r1,1 ,....,

r t,1

 

Inner Decoding

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AWGN Noise

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Innovation of Wireless Systems


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What is MIMO ?


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Required Knowledge


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MIMO Operation


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Macam-2 Teknik Space Time Teknik Space Time (MIMO)

Memaksimalkan Diversitas

Space Time Block Codes

Space Time Trellis Codes

Memaksimalkan Laju Data

Other Inner code

Layered ST architecture

 performance-rate complexity tradeoffs Rina Pudji Astuti

Threaded ST architecture

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Multiple Antenna Technique

Two popular techniques in MIMO wireless systems:

Spatial Diversity: Increased SNR

Spatial Multiplexing: Increased rate

•

•

Receive and transmit diversity mitigates

fading and improves link quality


Spatial multiplexing yields substantial increase spectral efficiency

31 

Spatial Diversity and Spatial Multiplexing Spatial Diversity – –



Signal copies are transferred from multiple antennas or received at more than one antenna redundancy is provided by employing an array of antennas, with a minimum separation of λ/2 between neighbouring antennas

Spatial Multiplexing –

the system is able to carry more than one data stream over one frequency, simultaneously

Spatial Multiplexing

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Maximize Data Rate (rate oriented)

• MIMO dengan Skema Vertical Encoding q

bits

Temporal Code + C symbols Interleaving + Symbol Mapper

C M Symbols T



1 : MT Demultiplex

MT

C MT

C M Symbols T

• MIMO dengan Skema Horizontal Encoding Code / mod

Primitive data Stream

Code / mod

4:1 Demux

Code / mod Code / mod

2 3 4



1



2



3

S2 t S3 t S4 t

4 Antennas

Space ( Antenna ) 1



S1 t

   

 LAYER 1 

 LAYER 2   LAYER 3   LAYER 4 

   

 4-D vector symbols duration

Time

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• MIMO dengan Skema Diagonal Encoding Code / mod layer A

Primitive data Stream

1

Code / mod layer B

4:1 Demux

2

Code / mod layer C

3

Code / mod layer D

4

Space ( Antenna )

Antennas  LAYER 1 

1 Layer A Layer D Layer C Layer B Layer A 2 Layer A Layer D Layer C Layer B

 LAYER 2 

3

Layer A Layer D

 LAYER 3 

4

Layer A

  Layer C  Layer D 

 LAYER 4 

 Layer B  Layer C  Layer D  Layer A

Layer A Layer B Layer A Layer C Layer B Layer A Layer D Layer C Layer B Layer A

 Time

4-D vector symbols duration

Rina Pudji Astuti

34

34 

Spatial Multiplexing MIMO channels can be decomposed into a number of R parallel independent channels → Multiplexing Gain –

Principle: Transmit independent data signals from different antennas to increase the throughput, capacity.

Source: An Overview of MIMO Systems in Wireless Communications www.iet.ntnu.no/projects/beats/Documents/mimo.pdf

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Spatial multiplexing bertujuan untuk meningkatkan kapasitas dengan cara mengirimkan beberapa aliran data secara paralel pada waktu yang bersamaan.

Prinsip kerja dari spatial multiplexing adalah mengirim sinyal dari dua atau lebih antenna yang berbeda dengan beberapa aliran data dan aliran data dipisahkan dipenerima dengan proses signal processing, oleh karena itu peningkatan bit rate berdasarkan konfigurasi antenna mimo ( 2 untuk antenna mimo 2 by 2 and 4 untuk antena mimo 4 by 4)


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MIMO Multiplexing  Data is not redundant – less diversity but less repetition  Provides multiplexing gain to increase data-rate  Low (no) diversity compared with STC


Maximize Diversity Transmission Scheme

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(performance oriented) in MIMO Wireless Systems Channel State Information with channel estimation scheme Coherent Ch. Scheme

e.g. Space time block code, STTC Unitary code, etc Traditional Inner Coding

Transceiver System Differential Modulation Transmission Scheme

Non Coherent Ch Scheme

With or Non Channel State Information with differential modulation

Rina Pudji Astuti

Differential Inner Coding

Multicarrier Techniques OFDM Coded OFDM

e.g. D-STBC, D-Unitary code, DUSTF code, MC-CDMA Multilevel Coding etc

MC CDMA

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38 



Spatial Diversity Improves the signal quality and achieves a higher SNR at the receiverside Principle of diversity relies on the transmission of structured redundancy

xi

yi

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Spatial Diversity

Beberapa replika sinyal informasi dikirim dari beberapa antenna yang berbeda (data informasi yang dikirim yaitu data info asli dan replika). Tujuan spatial diversity yaitu untuk meningkatkan SNR dengan cara mengurangi fading dan meningkatkan kualitas link antara pengirim dengan penerima.


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Space Time Coding

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• Space Time Block Code (STBC) [Alamouti1998]



C1 ,  C 2

*

h Antena Pemancar (Jamak)





C1 ,  C 2

*



virtual MIMO matrix

h

 C~ 1 , C~ 2 

Combiner



* C 2 , C1

Estimate





2

c  hn hn

dual diversity Rina P. Astuti

1

 1 1

2

h

 2

g   h1 

2

c  [c1

c 2 ]T

2

2

2  h2  

c

2



 y 2

[ c~1 1

n1'



y  y1

  h c~2 ]   1  h2

 h2

 h2   h1 

y  H.c  n

 h~1 , h~2 

– At the Receivers, after demodulator :

 2   h1  h2  

 h1 H    h2

 h 2   y1     h1     y 2 

 h1 n 2  h2 n    ' n2 

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Space Time Coding

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• Space Time Block Code (STBC) [Tarokh1999] •

Alamouti Model, 2 Tx antennas and 2 Rx

•

At the Receivers, after demodulator :

c~1

  y    h  h4   y 3  h  h   1 3 2 ~c   1            2  y  y4  h h h h 2 3  1   2  4





 h1  h2  h3  h4 c1  h1 n1  h2 n 2  h3 n 3  h4 n 4  2



2

2

2



n1

 h1  h2  h3  h4 c 2  h1 n 2  h2 n1  h3 n3  h4 n 4  2

~c  g.c  n ' •

Quadruple diversity

2

2

2

n2

g   h1 

2

 h2  h3  h4   2

2

2

Rina P. Astuti 43

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Space Time Coding •

Space Time Trellis Code (STTC) [Tarokh1998] – 2 – space time code, 4 PSK, 4 – state, 2 b/s/Hz 0

00 01 02 03

1

10 11 12 13

2

20 21 22 23

3

30 31 .32 33

1

Input : 02321103 Tx1 : 00232110 Tx2 : 02321103

2

0

,

3

Deretan bit masukan d  d k , d k ,  , d k ,  d  d k , d k ,  , d k ,  Derajat memory: v 2dan v, dengan v  v1  v, 2sehingga jumlah state 1 Pasangan koefisien pengkode: g 1  g 01,1 , g 01, 2 , g 11,1 , g 11, 2 ,  g v1 ,1 , g v1 , 2  1

1

1



dimana. g  0,1,2,3 2

2

 

vj

 g j 1 i  0

Rina P. Astuti



2

2

1

1

g 2  g 02,1 , g 02, 2 , g 12,1 , g 12, 2 ,  g v21 ,1 , g v21 , 2

j i ,l

KeluaranSTTC: s l ( k ) 

2

1

j i ,l

d kj i mod 4dengan

l  1,2



2v  4

Space Time Coding

44 





Aliran bit masukan, d : d  d 0 , d 1 ,  , d k ,  merupakan masukan sebuah modulasi M-PSK yang difungsikan sebagai pemeta simbol(mapper), dimana 1 2



d k  d k , d k , , d

 



m T k

Pengkode STTC yang terdiri dari m feedforward shift register akan memetakan deretan bit masukan menjadi himpunan sinyal M-PSK. Deretan bit masukan ke k, dimasukkan ke shift register ke k dan dikalikan dengan sebuah himpunan koefisien pengkode, berupa himpunan konstelasi M-PSK. Keluaran pengkode pada saat k, v berupa sinyal-sinyal termodulasi membentuk simbol berbasis ruang-waktu (space time symbol), dapat dinyatakan sebagai berikut: k



s k  s1 ( k ), s1 ( k ),  , s M T ( k ) m

vj

sl ( k )    g d j i ,l

j 1 i  0

Rina P. Astuti

j k i

mod M



T

M T adalah jumlah antena pemancar

g ij,l

adalah elemen himpunan konstelasi M-PSK

vk

adalah derajat memori shift register ke k

Modul 7 Konsep Dasar Multiple Antena

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