Implementation of Space-time Block Coding Using 2 Transmitter

7/23/2019 Implementation of Space-time Block Coding Using 2 Transmitter

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Implementation of space-timeblock coding using 2

transmitter and 2 receiverantennas

Project guideDeepthi Rapur, M.E

Presented by:

B.Snigdha

T.Neha

S.Arutha


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Contents

!. "ntroduction#. Di$ersity: %re&uency, tie and space

'. Space di$ersity and M"M( channe)s

*. Ma+iu )ie)ihood se&uence detection %or ST codes

-. Syste b)oc diagra

. /onc)usions

0. Re%erences

#


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INTRODUCTION Migration to '1 standards

high data rate communications required

high quality transmission and bandwidth efficient

communications

low decoding complexity

Major obstac)es to be so)$ed:

Multipath fading: signal is scattered among several paths,

each path has a different time delay.

Interference: + ISI in case of channels with memory

2 u)ti3user inter%erence

2 Mbps indoors

144 kbps

outdoors

'


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Space time codeSTC!"

S!" It is a method employed to improve the reliability ofdata transmission in wireless communication systems using

multiple transitantennas. S!"s rely on transmitting

multiple, redundant copies of a data stream to the receiver in

the hope that at least some of them may survive the physical

path between transmission and reception in a good enough

state to allow reliable decoding. Space time codes may be split into two main types:

Space#time trellis codes$S!!"s%distribute a trellis code over

multiple antennas and multiple time&slots and provide both

coding gain and diversity gain .

Space#time bloc' codes$S!("s% act on a bloc' of data atonce $similarly to bloc' codes% and also provide diversity

gain but doesn)t provide coding gain.

*
https://en.wikipedia.org/wiki/Space%E2%80%93time_trellis_codehttps://en.wikipedia.org/wiki/Space%E2%80%93time_block_codehttps://en.wikipedia.org/wiki/Space%E2%80%93time_block_codehttps://en.wikipedia.org/wiki/Space%E2%80%93time_trellis_code


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Diversit#

Solution of the multipath fading problem, by transmission ofseveral redundant replicas that undergo different multipath

profiles.

!ypes:

*requency diversity: same information is transmitted on

different frequency carriers, which will face differentmultipath fading.

!ime diversity: replicas of the signal are provided in the form

of redundancy in the time domain by the use of an error

control code together with a proper interleavers s s- s time

redundant of -

f1

f2

f [Hz]

S(f)


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Space diversity: redundancy is provided by employing an

array of antennas, with a minimum separation of /0

between neighbouring antennas. 1ifferently polari2ed

antennas can also be used.

2/

2/


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c!4!5c!4#5

c#4!5c#4#5

0

=

+=n

i

ii ttcthtr

1

1 )(1)()()(1

=

+=n

i

ii ttcthtr1

2 )(2)()()(2


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where:

ci$l% is the modulation symbol transmitted by antenna i at

the time instant l. It is generated by a space&time encoder.

hi3is the path gain from !x antenna i to 4x antenna 3.

53$t% is an independent 6aussian random variable $768

channel%.

6


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!a'ing the equation : the signals at thereceiving antennas can be expressed in matrix form:

!herefore we can create the MIM9 channel matrix as

7

= +=n

imiimm ttctgtr

1)()()()(

+

=

)(

|)(

)(

)(

)(

|)(

)(

)(

)(...)()()(

|||||)(...)()()(

)(...)()()(

)(...)()()(

)(

|)(

)(

)(

3

2

1

3

2

1

321

3332313

2322212

1312111

3

2

1

t

t

t

t

tc

tc

tc

tc

tgtgtgtg

tgtgtgtg

tgtgtgtg

tgtgtgtg

tr

tr

tr

tr

mmnmmmm

n

n

n

m

mxnnmmmm

n

n

n

tgtgtgtg

tgtgtgtg

tgtgtgtgtgtgtgtg

tG

=

)(...)()()(

|||||

)(...)()()(

)(...)()()()(...)()()(

)(

321

3332313

2322212

1312111


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S#stem block diagram

$ncoder"

Sn(t)

S2(t)

Inf

MapSpace-Time in!

"ncoder

b0binary

x

Inter#ea$er%rame

&ui#din! Modu#ator

c22

'c

S1(t)

Inter#ea$er

%rame

&ui#din! Modu#ator

c11

'c

1'c%&

nc'%n

Inter#ea$er%rame

&ui#din! Modu#ator

cnnc

'

I. "ncoder

!8


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Decoder"

Space-Time

iterbi ecoder

(Se*uenceetection)

etection +

emodu#ation

,anne#

"stimation

einter#ea$er

etection +

emodu#ation

einter#ea$er

In$

Map

r

binar

output

r1(k)

r2(k)etection +emodu#ation

rm(k)

jig 0'

r&t!

r2t!

rmt!

4 Zx

b

In case of iterati$e canne# estimation

!!


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Conclusion

!he use of space&time diversity techniques for transmissionover fading channels offers a promising increase in the capacity.

!he capacity of MIM9 channels can even increase linearly with

the number of transmit antennas.

In particular, space&time codes provide a significantly better

performance than single antenna systems.

!he design criteria for space&time codes has been presented.

!hese ta'es into account two factors: the diversity advantage

and the coding gain.

Maximum&li'elihood detection techniques can be applied in the

decoding process without an increase on the decoder

complexity. "omputer simulations avail these statements by showing a

smaller (4 at a fixed S84.

!#


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References

ST/39iipedia , the %ree encyc)opedia A.Mo)isch , 9ire)ess /ounications. 9i)ey3"EEE Press, #88-

S)ide share : https:;;;.sta%%.nc).ac.ur...Space


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!*

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Implementation of Space-time Block Coding Using 2 Transmitter