The Powerful Alamouti Code in MIMO -OFDM Improvement for the Next Generation of Terrestrial...

International Journal of Engineering & Technology IJET-IJENS Vol:14 No:01 33

140801-7575-IJET-IJENS © February 2014 IJENS I J E N S

The Powerful Alamouti Code in MIMO -OFDM

Improvement for the Next Generation of Terrestrial

Television Broadcasting Systems El Miloud Ar reyouchi

1 ,Kamal Ghoumid

1,2, Koutaiba

Ameziane

1 and Otman El Mrabet

1

1 Department of physique, faculty of Science, Abdelmalek Essaadi University, Tetouan, Morroco.

[email protected] 2 Department of Electronics, Informatics and Telecommunications, ENSAO, Mohammed I University, Oujda, Morocco.

[email protected]

Abstract— This paper proposes and analyses an efficient

wireless telecommunication system with multiple antennas to the

emission and reception MIMO (multiple input multiple output)

with space diversity in an OFDM (Orthogonal Frequency Di

vision Multiplex). The proposed system consists to add modified

Alamouti encoder to the system OFDM to improve the

performance of the destination by intimately collaborating with

the antennas system. We analyse the performance of a DTT

(Digital Terrestrial Television) broadcasting system that

includes MIMO encoder, associate with OFDM techniques,

which can improve the appreciation of the quality of

transmission bit error rate (BER) in terms of (C/N) carrier-to-

noise ratio. Different propagation channel models and

configurations are considered for each diversity scheme. This

study has been carried out in the context of MIMO -OFDM

improvement for the next generation of Digital Terrestrial

Television broadcasting systems.

Index Term-- MIMO, Next generation DVB, Alamouti Code.

1. INTRODUCTION

The multi-antenna systems in the broadcast (emission) and

in the reception (Multi-input Multi-output MIMO) is a key

technique For the wireless cellular communications of the

generation (WRAN, WIMAX .., as well as the broadcasting

(DVB) [1] allow in theory to increase the capacity of the links

for wireless communications, with regard to the systems

consisted of a single antenna in the emission and in the

reception (Single input Single output SISO). By making the

hypothesis, where the routes between every antenna emission

and reception are independent. Foshini [2] and Telatar [3]

demonstrated that the theoretical capacity of the channel

MIMO with Nt antennas in the emission and the Nr antennas

in the reception believes linearly with min (Nt,Nr).

The MIMO systems are one of the main axes of development

to increase the bit rate of data transmission of the wireless

communications.

The MIMO systems are proposed for example for the

future standard of wireless local area network

The MIMO systems [4] present two major advantages with

regard to the systems SISO

1- Thanks to the contribution of the spatial diversity, they

allow to improve the quality of the link by franking from

faints, fading of channels.

2- By spatial multiplexing, they allow to increase the bit rate

of information, without increasing the bandwidth or the

power transmitted.

The basic principle of MIMO systems is to combine the

signals appropriately on transmission and reception, therefore

to exploit space diversity and thus reduce the effects of fading

or to increase the bit rate of transmission.

Since DVB-T system [5] was designed, modulation

techniques and error coding methods have suffered from an

important development [6]. Moreover, it is now possible to

add much more sophisticated technology in receivers

maintaining costs.

These facts together with a larger capacity requirement for

HDTV (High Definition Television) have led to the necessity

of the next generation DVB-T called DVB-T2 [7].

The inclusion of MIMO techniques in DVB-T2 seems to be

a fact. At the moment, in the first draft specification of

DVBT2 [7] MISO techniques are considered, which could be

the beginning for a complete diversity support by a further

inclusion of MIMO techniques.

In OFDM systems the most used techniques to include

MIMO support are the space-time and space-frequency

coding techniques [8]. The proposed codification technique

for MISO in the DVB-T2 draft [7] is based on the Alamouti's

code [9] and the proposed method is a space-frequency code,

derived from a modified coding matrix of the original

Alamouti space-time code.

The modifications to Alamouti‟s code proposed in this

paper are the necessary ones to allow the expansion of the

MISO scheme to a full MIMO diversity scheme. This will

allow, with the help of polarization diversity, backward

compatibility with SISO receivers that have no MIMO

decoding logic.

mailto:[email protected]



Fig. 1. Wireless Transmission system MIMO

In order to use MISO techniques it is necessary to increase

the number of transmit antennas, modify the transmission and

reception equipment. Additionally, in the case of MIMO, it

is also necessary to add antennas to the receivers. All this

means an important investment in infrastructure. So, a study

must be carried to see if the improvement in the system

performance justifies it.

The following figure (Fig. 2) shows a real and practical area

of region northern of MOROCCO in which we perform

measurements of MIMO systems and are consequently used

in this article. Over the figure illustrious the presence of

several central transmitters broadcast TV (DTT).

Fig. 2. Part of the region where measurements are made.

In the following of this paper we are interested in MIMO–

OFDM Encoder system of the next generation DVB-T/H for

the proposed system (Fig 2) but may also be applicable for

the future standard WRAN which operates also in TV bands

[10] where in MIMO-OFDM Encoder: will improve

performance of BER as well as reduce feedback information

and Improve spectral efficiency of CR system.

This paper is organized into six sections including

introduction. Section 2 gives a main of objectives of our

experiment. Section 3 describes an overview of general

scheme for MIMO system conventional and system proposed

with (encoder MIMO) for a next generation DVB-T. Section

4 we show the experimentation used in this application. For

the section five it will presents the results of measurements.

Conclusion is given in Section 6.

2. OBJECTIVES

The main objective is to compare the reception quality in

the most current configuration of antenna system SISO,

MISO and MIMO of DVB-T broadcasting scheme (Fig: 3) ,

without MIMO Encoder, with the new proposed MISO and

MIMO diversity , with MIMO Encoder, in OFDM technique

schemes (Fig:6)

It should be noted that the system of figure (3) is the most

currently used method, without encoder MIMO, in all

countries of the worlds

As one of the proposed modified Alamouti‟s code

characteristic is the fact that it allows backward compatibility,

when we using polarization diversity,

It is also important to study if the proposed modification to

the Alamouti‟s code for the MIMO configuration affects the

system efficiency, comparing it to the one of the original

Alamouti‟s coding matrix.

The results in this paper are shown as bit error rate (BER)

plotted in terms of Carrier/Noise (C/N).

2.1. Principle of the Antenna diversity for MIMO system.

The spatial diversity is becoming more and more popular

today. It is also called antenna diversity and it‟s represent an

effective method for combating multipath fading. In this

scheme, replicas of the same transmitted signal are provided

across different antennas of the receiver. We can apply it in

cases where antenna spacing is larger than the coherent

distance to ensure independent fades across different

antennas. The traditional types of spatial diversity are

selective combining, maximum ratio combining, and equal

gain combining [11].

Spatial diversity [12] [9] can also be classified according

to whether diversity is applied to the transmitter or to the

receiver. With regard to receive diversity, it often employs

maximum ratio combining to improve signal quality. But in a

mobile receiver, such as cell phones, it becomes costly and

cumbersome to deploy this scheme. This is one main reason

that transmit diversity becomes popular, since it is easier to

implement at the base station side. With transmit diversity,

controlled redundancies are introduced at the transmitter, and

then exploited by appropriate signal processing techniques at

the receiver. Particularly, with space-time coding schemes

like Alamouti‟s scheme [9], it becomes Possible to implement

transmit diversity without knowledge of the channel.

2.2. Diversity Coding for MIMO-OFDM. Diversity Coding

is the spatial coding techniques for a MIMO system in

wireless channels. Wireless channels suffer a lot from fading

phenomena, which causes unreliability in data decoding.

Fundamentally, diversity coding sends multiple copies

through multiple transmit antennas, so as to improve the

reliability of the data reception. If one of them fails to receive,

the others are used for data decoding.

http://en.wikipedia.org/wiki/MIMO



The powerful attractive combination of MIMO and

OFDM techniques, or MIMO-OFDM, will impact the

evolution of wireless LANs, and is a leading candidate for

future fourth generation (4G), DVB-T2 and WRAN wireless

communications systems. The MIMO-OFDM advantage is

very high capacity and spectral efficiency achieved by

simultaneously employing the time, space and frequency

domains. A key component of a practical MIMO-OFDM

system [13] is improved communications reliability, i.e.,

reduced bit error rate (BER) [14], achieved at reasonable

computational complexity.

No multi-antenna technology is implemented in the DVB-

T standard [15].

3. SYSTEM

3.1. Common and ordinary System. The standard of

broadcasting DVB.T most common and ordinary in several

countries is represented by the following figure (3).

Fig. 3. MIMO system without encoder MIMO: Block diagram of a COFDM

Transceiver: It is the synoptic plan of a TV broadcasting station (Digital Terrestrial Television DTT).

At the transmitter, the system is defined as functional

block of equipment performing the adaptation of TV signals

in the baseband at the output of the multiplexer of MPEG-2

transport, to the terrestrial channel characteristics.

The following treatment is applied to the data stream:

Mux Adaptation Energy Dispersal.

Outer coder, Code Reed-Solomon (204,188, T= 8).

Outer interleaver.

Inner coder (Convolutional Encoder).

Inner interleaver.

Mapping and modulation.

Transmission OFDM

The figure (3) represents the block diagram of transmitter

of DTT with multiple antennas to the emission with space

diversity in an OFDM, but without MIMO encoder.

The RF splitter is used to distribute the power output from

the different broadcasting antennas.

From the model above (figure 3) we will make practical

measurements in Non-Line-of-Sight (NLOS) propagation

condition, Rayleigh channel [16] (see figure 4) and then we

will represent them in section 5.

Fig. 4. MIMO System Rayleigh Channel: Transmitter without MIMO

encoder.

The (Figure 5) shows the relation between BER and quality

of service (QoS).

Fig. 5. relation between BER and quality of service

To carry a fast and precise BER measurement, it is

preferable to place before the Reed Solomon decoder, where

errors are more numerous.

3.2. System proposed. A simulator of the proposed system

has been developed in Matlab to carry out all the studies. This

simulator includes a transmission and reception DVB-T



chain, to which MIMO coding and decoding blocks are added

(Fig. 6).

Fig. 6. MIMO system proposed with (encoder MIMO) for a next generation

DVB-T.

At the transmitter side, after the coding and modulation

process – including: MUX adaptation & energy dispersal,

outer coder, outer interleaver, inner coder, inner interleaver

and mapping data in the constellation – the MIMO coding

process are performed. The outputs of this process are

handled as two independent fluxes to which pilot insertion;

frequency to time translation and guard interval insertion

must be applied. The receiver consists of the complementary

blocks, so it recovers the transmitted information.

For the MISO case only the receiver has to be modified.

The receiver has only one reception antenna from the

received information, it estimates the channel response and

decodes the information.

The SISO case corresponds to the usual DVB-T

transmission and reception scheme [17], [18].

The results of the proposed system are represented by

simulation in Section 5.

3.3. Coding. Alamouti‟s space-time code [9] is represented

by the following matrix (1):

*12

*21

xx

xxx (1)

Where *ix represents the conjugation of ix .

Each row represents the transmitting antenna and each

column represents a time interval. Thus, in the first time

interval 1x symbol will be transmitted from the first antenna

and 2x from the second one, while in the second time

interval *2x will be transmitted from the first antenna

and *1x from the second one.

Taking this code as the base and moving the time technique

to the frequency domain, the frequency-time code results into

the one in (2).

*)12()2(

*)2()12(

nn

nn

XX

XXX (2)

Where )2( nX represents the conjugation of )2( nX .

Each row represents, as before, the transmitting antenna but

now the column represents the data carrier. Thus from the

first antenna, in the first carrier the first data carrier of the

OFDM symbol is transmitted. In the second one the carrier of

the symbol in the same position but conjugated and inverted

is transmitted. From the second antenna, in the first carrier the

second data carrier is sent. In the second carrier the first data

carrier in OFDM symbol conjugated is transmitted. This code

is applied to every pair of data carrier in each OFDM symbol.

The modified code proposed to allow backward

compatibility, is the transposed matrix of (2).

*)12(

*)2(

)2()12(

nn

nn

XX

XXX (3)

The first row represents the data carriers transmitted by the

first antenna. Data carriers transmitted from this antenna

maintain the position and value of the original OFDM

symbol.

This means that from the first antenna, the same signal as

the one that would be broadcast in a SISO scheme is

transmitted, which eases backward compatibility.

By using orthogonal polarization in the transmitter

antennas, both transmissions can be received separately.

The first antenna will be horizontally polarized, as the case

of current DVB-T receivers, and the second antenna will have

vertical polarization. Hence current receivers will receive

mainly the data transmitted by the first antenna. On the other

hand, new receivers including MIMO decoding will be

provided of two antennas, one with horizontal polarization,

the other one with vertical polarization, so they can receive

information from both paths, benefiting from spatial diversity.

It must not be ignored that a small amount of signal level

that can be received by the antenna, with the opposite

polarization. This will also be considered in the simulations

(Fig. 7).



Fig. 7. Broadcasting scheme when coexisting MIMO and SISO receivers

In order to simulate this effect, a cross-polar factor (XPD)

has been defined to attenuate hij i≠j, paths. The minimum and

maximum values are 9 dB and 25 dB respectively.

In [7] it is proposed an optional MISO inclusion in DTT

broadcasts with the codification shown in (3). There is no

mention to the use of polarization diversity, so that solution

would create the necessity of using new frequencies.

3.4. Channels. To obtain useful results, it is a crucial

point to simulate suitable propagation channels. For that

reason F1, P1 and TU6 have been selected as the propagation

channels.

These three channel types (figure 9) are the most

commonly used for this kind of simulations. F1 and P1 are

the ones considered in the DVB-T specification [17], and

TU6 is a typical channel for mobile reception [19].

These channels have also been used in other studies related

to DVB-T2 [20].

In the case of our results, the Rayleigh channel propagation

F1 is selected as propagation figure (4) Rayleigh fading [21]

is a reasonable model (our type of propagation in this paper)

when there are many objects in the environment that scatter

the radio signal before it arrives at the receiver.

Channels in MIMO form a matrix (4), which shows all the

possibilities of paths between each transmitter and receiver

antenna.

2221

1211

HH

HHH (4)

In MISO the matrix reduces to the array (5):

1211 HHH (5)

where Hij represents the path between the „i‟ receiver and

the „j‟ transmitter.

3.5. Estimation of the channels of transmission. Compared

to SISO channels, estimation of frequency selective MIMO

channels is more difficult, because there are more parameters

to estimate and less power per transmitter [22].

The channel estimation generally requires pilot symbols,

which reduce the power useful transmitted and spectral

efficiency.

As MIMO systems are more parameters to estimate, the

number of pilot symbols can be important.

For MIMO-OFDM systems, the most common approach is

to use pilot symbols, to estimate the channel in the sense of

least squares criterion and then use an interpolation technique

[23] and [24].

In addition to the distribution of pilots on the time axis and

the frequency , which depends on the properties of the

transmission channel, in MIMO systems, the training

sequence must be optimized (orthogonally, ...) [25] .

For these systems, it is also possible to use adaptive

algorithms [26]. In most architecture, the data are not used to

improve the estimation of the transmission channels.

However in practice it is difficult to estimate the transmission

channels, a joint approach seems a promising line to improve

system robustness and potentially reduce the number of pilots

necessary for transmission.

4. EXPERIMENTATION

From the model ordinary (figure 3), we will make practical

measurements witch are taken in the Rayleigh channel in

Non-Line-of-Sight (NLOS) (figure 4) while the proposed

system (figure 6) are simulate in Matlab.

4.1. Technical values. The selected values for modulation

and coding parameters during the practical measures are used

for Moroccan DVB-T transmissions. These values are the

following ones.

- Channel Width: 8.00 MHZ.

- Measurement filter: 230KHz

- Transmission mode: 8K

- Non-hierarchical mapping.

- Constellation: 64-QAM.

- Code rate: 3/4.

- Guard interval: 1/16.

The QEF (Quasi Error Free) reception quality criteria have

been used to analyze the reception quality. The QEF means

one uncorrected event per hour; it corresponds to a BER of

10-11

after Reed-Solomon decoder and a BER of 2x10-4

after

soft Viterbi decoder. BER after Viterbi decoder is the

parameter that will be analyzed.

The practical measurements are taken on different urban

places (NLOS) see LOS in [27] to value practically the

performances of the systems MIMO.

The practical measurements were performed using

transmitter NEC, EGATEL unit as the transmitter and

Promax HD RANGER+ (Level meter- Analyzer) test

receiver. Finally, obtained results are discussed compared to

the results of the laboratory measurement



4.2. Equipment used:

4.2.1. Broadcasting side

- Two transmitters DVB brand NEC UHF channel 24

(498 MHz) power from 0 to Watts 1000Watts..

- A transmitter DVB brand EGATEL UHF Channel:

31 (554 MHz) power from 0 to Watts 1000Watts.

- Three panel antennas of horizontal polarization.

- Three antennas/Power Distribution System, 470-

952 MHz UHF (a input- a output) (input-two output)

(input-three outputs)

4.2.2. Receiving case.

- HD RANGER+ (The HD RANGER+ is a universal

analyser that covers a comprehensive mix of broadcast

standards around the globe. The latest developments in

broadcast technology such as DVB-T2/C2/S2 (DVB-

T/C/S also included) with MPEG-2 as well as MPEG-4

video are managed effortlessly within the product).

- 3 Antennas (AMC / 1) UHF (470 MHz to 860 MHz)

at a height of 2m from the ground.

- Two power couplers (one has two inputs and one

output while the other has three inputs and a one

output.

In this practical work we have taken the following steps:

- MER (Modulation Error Ratio), which represents all

the problems affecting the constellation diagram

- C / N

- BER after Viterbi VBER (Bit Error Rate) for

appreciation the quality of transmission

The measurements obtained are verified in the laboratory,

TV/FM broadcasting center, with the following:

- Agilent E4402B (3 GHz). Spectrum Analyzer.

- Generator Rohde and Schwarz DVB SFQ.

- Demodulator measurement DVB EFA-T Rohde and

Schwarz.

- HF generator Hewlett-Packard 8656 B.

- 3 dB coupler measuring Radiall 500-1000 MHz.

- Load of 50 ohm load.

The signals used are supplied by a generator DVB Rohde

and Schwarz SFQ. This ensures a perfect control of various

parameters characterizing a DVB-T signal and simulates

various defects that may occur in transmission. Signal

measurement is performed with a spectrum analyzer and

Agilent E4402B with a demodulator measures Rohde and

Schwarz EFA-T.

Fig. 8. HD RANGER+ TV & Satellite analyser –PROMAX

5. Results

5.1. Channel. In order to validate the performance of the

practical measurements, we started with the measurements

that show the effect of all the propagation channels

considered in the case of a SISO transmission (Fig. 9).

Required C/N value to achieve a BER of 2·10-4

after Viterbi

decoder can be compared in Gaussian, F1 and P1 channels,

with the C/N thresholds in [17].

The C/N thresholds obtained are approximately 2 dB

higher, which is due to the linear channel estimation used

instead of using the optimal 2-D Wiener estimation in the

equalizer. This is not a significant difference for the

comparative study as all the techniques considered use the

same equalizer.

10 15 20 25 30 3510

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

BE

R

C/N (dB)

Practice : BER after Viterbi for different simulation channels

Gaussian channel

Ricean channel(F1)

Rayleigh channel (P1)

TU6

Fig. 9. Measurement results BER after Viterbi for different channels

We see that the measured values satisfy the theoretical four

types of the channels.

5.2. Simulated bit-error rate Diagrams. Below are bit-error

rate diagrams for the various modulations, using both short

and long FEC codes.



The measures taken have been shown as curves in each

case see Fig. 11, Fig.12 and Fig.13.

The data in the DVB-T specification which relates to the

efficiency of the system are based on practical measurement

results using a Rayleigh channel model (no line-of-sight

path).

The practical values are taken in urban areas and then they

check in the SNRT laboratory, by the measuring apparatus.

Fig. 10. Model of measurement +parameters taken for guard interval=1/4

and FEC= 2/3(during testing measurement)

5 10 15 20 25 30 3510

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

Practice :SISO Rayleigh Channel - Modulation 64QAM

BE

R

C/N (dB)

Code rate:1/2

Code rate:2/3

Code rate:3/4

Code rate:5/6

Code rate:7/8

Fig. 11. Measurement results of the BER performance of the 64QAM

modulation, Rayleigh Channel con with different values of FEC code in

SISO (Nt=1, Nr=1) transmission.

We note that the different values of FEC, show the change

of the measurement that coincides well with the theory and

simulation figure11.

The FEC most used in countries are 2/3 and 3/4. Fig 12

6 8 10 12 14 16 18 20 22 24 2610

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

Practice :SISO Rayleigh Channel - Modulation 64QAM

C/N (dB)

BE

R

Code rate:2/3

Code rate:3/4

Fig. 12. Measurement results of the BER performance of the 64QAM

modulation, Rayleigh Channel con FEC:2/3 , 3/4 in SISO (Nt=1, Nr=1) transmission.

We will work with FEC= 3/4 used in Morocco Fig .13

10 15 20 2510

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

Practice : SISO Rayleigh Channel - Modulation 64QAM

C/N (dB)

BE

R

Code rate:3/4

Fig. 13. Measurement results of the BER performance of the 64QAM modulation, Rayleigh Channel con FEC: 3/4 in SISO (Nt=1, Nr=1)

transmission.

5.3. Diversity. The effect of diversity on quality reception,

has been studied by comparing the SISO, MISO and MIMO

techniques proposed (Fig: 4) with different diversity

configurations (Fig: 3). This is depicted in Fig. 14, Fig. 15,

Fig. 16 and Fig.17, and the results for other combinations are

summarized in Table I .and Table II.



10 15 20 2510

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

C/N (dB)

BE

R

Performance of Diversity Technique(Rayleigh Channel)

Practice SISO (1Tx,1Rx) 64 QAM

Practice MISO (2Tx, 1Rx) 64 QAM

Fig. 14. Measurement results of diversity technique of the 64 QAM

modulations, FEC=3/4,(Rayleigh channel) for SISO, MISO .

10 15 20 2510

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

C/N (dB)

BE

R

Performance of Diversity Technique(Rayleigh Channel)

Practice SISO, 64 QAM

Practice MISO (2Tx, 1Rx) 64 QAM

Practice MIMO (2Tx, 2Rx) 64QAM

Fig. 15. Measurement results of diversity technique of the 64 QAM

modulations , FEC=3/4,(Rayleigh channel) for SISO,MISO and MIMO.

From Fig. 15 it is seen that channel performance is

improved with Alamouti code in Rayleigh channel for 2×1 or

2×2 MIMO configuration. When the number of transmitting

and receiving antenna is increased like Alamouti (2Tx, 2Rx).

10 15 20 2510

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

C/N (dB)

BE

R

Simulation results of MIMO Encoder Alamouti system .

sim SISO

sim MISO (2x1) modified Alamouti

sim MIMO(2x2) modified Alamouti

Fig. 16. Simulation results of SISO No diversity (1Tx, 1Rx) and MISO

(Alamouti (2Tx, 1Rx)) and MIMO (Alamouti (2Tx,2Rx))system.

The result is shown in Fig. 17 which makes the comparison

between the results of practical measurement and the results

simulation with Alamouti encoder

10 15 20 2510

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

BE

R

C/N (dB)

The performance of MIMO-OFDM using both measurement results and simulation results

sim SISO

Practice SISO

Practice MISO(2x1)

Practice MIMO(2x2)

sim MISO (2x1) Alamouti

sim MIMO(2x2) Alamouti

Fig. 17. Comparison of simulation results, with the MIMO Alamouti Encoder

Scheme, and practical measurement results for 64QAM transmissionn

FEC=3/4(without encoder MIMO)



The Following Tables gives the comparison of the

performance of MIMO-OFDM using the measurement

results(without MIMO Encoder) and the simulation

results(with MIMO Encoder) for a particular (BER) bit error

rate (Table1) and (C/N) carrier-to-noise ratio( table II )

respectively.

Table I

Required C/N (dB) for BER = 2*10-4 after Viterbi.

Bit Error Rate

(BER)

Diversity Technique C/N in

dB

2•10-4 After

Viterbi

No diversity 21.5

Practice MISO(2x1) Practice MIMO(2x2)

20.41

19.31

sim Alamouti(2Tx,1Rx)

sim Alamouti(2Tx,2Rx)

19.01

18.28

Table II Required BER for C/N = 20dB.

C/N in dB Diversity Technique Bit Error Rate(BER)

20

No diversity 0.0025

Practice MISO(2x1)

Practice MIMO(2x2)

0.000475

0.0000512

Sim Alamouti(2Tx,1Rx)

Sim Alamouti(2Tx,2Rx)

0.0000111

0.00000213

6. CONCLUSION

The performance of MIMO with Alamouti scheme

modified coding and polarization diversity, compared to the

system MIMO without encoding are evaluated under the

assumption of 64QAM signals, FEC=3/4 and channel

Rayleigh, affected by reflection, detraction and scattering

environment.

The comparison (of the final results) between the

measurement results (of ordinary DTT system without

MIMO Encoder) and the simulation results ( of the proposed

system with MIMO Encoder) provided by the curve in Figure

17 and the numerical values in Table 1 and 2, showed that the

model of the system proposed of the MIMO Encoder using

OFDM technologies, can better improve the appreciation of

the quality of transmission and provide good quality of

reception as the system without encoding.

Therefore, the Simulation results confirm that the proposed

system outperforms the measurements results of conventional

system.

ACKNOWLEDGMENTS

We would like to thank to the direction of the broadcasting

of SNRT for we implement provision central laboratory

measuring devices. The authors would like to thank the

reviewers for their valuable comments.

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