JOURNAL OF TELECOMMUNICATIONS, VOLUME 3, ISSUE 1, JUNE 2010 115

Capacity enhancement of 4G- MIMO using Hybrid Blast STBC Systems Nirmalendu Bikas Sinha1, Sourav Chakraborty2 , And R.Bera3 Abstract— In this paper, we examine a novel signal scheme called “Hybrid BLAST STBC approach” this combines MIMO and STBC to generate a system functionally superior to MIMO and STBC systems. We examine the capacity of high data rate open loop MIMO architectures and their performances. The first part of the study shows how the multilayered space time block code (MLSTBC) compares to other MIMO systems, such as V-BLAST and STBC. We focus on the information capacity comparison in order to evaluate the optimal performance of the systems. We show the tradeoffs of these systems and what the advantages of MLSTBC are. The results show that when the number of transmit and receive antennas are equal, MLSTBC is more power efficient than VBLAST, since it provides more diversity. Furthermore, at low SNR and low outage probabilities, MLSTBC is more spectrally efficient. Thus, it is more suitable for low power wireless data applications.Finally we evaluates and investigates the capacity of high data rate wireless local area network systems using MIMO techniques. The focus of the study is to compare the information capacity of hybrid systems with V-BLAST and STBCs. Hybrid BLAST STBC can balance transmit diversity gain and spatial multiplexing gain. All three techniques are compared using both theoretical Shannon capacity analysis and by simulation results for the capacity performance of the three methods. The result of this study shows that hybrid method attains superior diversity gain performance to V-BLAST and can out form V-blast at spectral efficiencies of practical interest. The capacity expression and evaluation for “Hybrid BLAST STBC approach” are a unique contribution of this work. This study gives useful insight into the optimal performance of these algorithms and into the spatial multiplexing-diversity tradeoffs of these systems. Index Terms— MLSTBC,MIMO, VBLAST,HYBRID BLAST STBC.

——————————  ——————————

1. INTRODUCTION significantly increase channel capacity: the use of Wireless systems continue to strive for ever higher data rates. This goal is particularly challenging for systems that are power, bandwidth, and complexity limited. However, another domain can be exploited to

multiple transmit and receive antennas. Pioneering work by Winters [1], Foschini [ 2], and Telatar [ 3] ignited much interest in this area by predicting remarkable spectral efficiencies for wireless systems with multiple antennas when the channel exhibits rich scattering

————————————————

• 1Prof. Nirmalendu Bikas Sinha, corresponding author is with the Department of ECE and EIE , College of Engineering & Management, Kolaghat, K.T.P.P Township, Purba- Medinipur, 721171, W.B., India. • 2SouravChakraborty is with the Department of ECE, College of Engineering & Management, Kolaghat, K.T.P.P Township, PurbaMedinipur, 721171, W.B., India. • 3Dr. R. Bera is with the S.M.I.T, SikkimManipal University, Majitar, Rangpo, East Sikkim, 73713.

and its

variations can be accurately tracked. This initial promise of exceptional spectral efficiency almost “for free” resulted

in an explosion of

characterize

the

theoretical

research activity and

practical

to

issues

associated with MIMO wireless channels and to extend these concepts to multiuser systems. The keen interest in

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JOURNAL OF TELECOMMUNICATIONS, VOLUME 3, ISSUE 1, JUNE 2010 116

MIMO communications was triggered by the results in

SNRs and at low outage probabilities. The idea of this

capacity

The

scheme is to demultiplex a single user’s data into parallel

battlefield of MIMO is the radio communication channel

layers of information. Then, each layer is encoded by a

which is a very hostile and harsh environment for the

STBC. Each code is called a group, because the total

transmission of information. Within this new MIMO

number of transmit antennas are divided into groups and

perspective,

multi-path

each group is assigned a STBC. This architecture was first

considered

as

improvement

a

for

MIMO

propagation

noxious

channels.

is

no

the

considered in [5] where they used space time trellis codes

communication process. Instead, it can be said that the

(STTC) as the component codes. In a multi-user

multi-path is a sort of a blessing for MIMO technology, as

environment, a multi-user STBC system with minimum

it takes advantage of the randomness of fading.

mean-squared error (MMSE) detection was studied in [6].

Moreover, this advantage comes at expense of hardware

In [7], different decoding algorithms for “Hybrid BLAST

and complexity but not from extra spectrum, so it is a

STBC” were compared over flat fading MIMO channels.

very interesting spectral efficient technology achieved

One advantage of using STBC over STTC is that the

through the deployment of extra spatial ports at both

orthogonal structure and the short code length can be

ends of the transmission link. VBLAST [4] is a spatial

exploited at the receiver to reduce the minimum required

multiplexing scheme that transmits independent layers of

number of receive antennas [6]. For multilayer Space time

information through a MIMO channel. In general, all

trellis codes MLSTTC [5], [8], the number of receive

these gains cannot be achieved simultaneously, as they

antennas should be at least equal to the total number of

are dependent on antenna configuration and scattering

transmit antennas. However, for Hybrid BLAST STBC, it

environment.

is equal to the number of layers.

Hence,

good

phenomenon

longer

knowledge

in

of

the

characteristics of the propagation environment is crucial for maximizing the achievable MIMO gains. In fact, the

2. MIMO SYSTEM CHANNEL CAPACITY

very demanding performance targets set for nextgeneration systems are virtually impossible to reach

Multipath propagation has long been regarded as

without an efficient utilization of multiple antennas both

“impairment” because it causes signal fading. To mitigate

at transmitter and receiver side. However, it has poor

this problem, diversity techniques were developed.

energy performance and doesn’t fully exploit the

Antenna diversity is a widespread form of diversity.

available diversity. The V-BLAST algorithm aims to

Information theory has shown that with multipath

maximise the capacity by using combination of spatial

propagation, multiple antennas at both transmitter and

processing and subtractive cancellation to remove co-

receiver can establish essentially multiple parallel

channel interference, provided that the number of

channels that operate simultaneously, on the same

antennas at the receiver is greater or equal to that of the

frequency band at the same total radiated power.

transmitter. Conversersely, the STBC[5] or Alamouti

Antenna correlation varies drastically as a function of the

scheme exploits the diversity against fading that is

scattering environment, the distance between transmitter

available from employing multiple antennas at the

and receiver, the antenna configurations, and the

transmitter and possible at the receiver but with a

Doppler spread. Recent research has shown that

maximum code rate of one which is achieved at two

multipath propagation can in fact “contribute” to

transmit antennas.

capacity.

Combining V-BLAST and STBC results in a layered

Channel capacity is the maximum information rate that

architecture with transmit diversity in each layer. This

can be transmitted and received with arbitrarily low

can be called a “Hybrid BLAST STBC approach” to try to

probability of error at the receiver. A common

exploit the advantages of both higher data rates and

representation of the channel capacity is within a unit

increased diversity gain of the MIMO system at low

bandwidth of the channel and can be expressed in

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JOURNAL OF TELECOMMUNICATIONS, VOLUME 3, ISSUE 1, JUNE 2010

(bandwidth) efficiency. MIMO channel capacity depends

Where E .. 0 is the expectation operator with respect to

heavily on the statistical properties and antenna element

random variable with zero mean and a variance of 0.5 per

correlations of the channel. Representing the input and

dimension. When M is large, by the law of large numbers

117

bps/Hz. This representation is also known as spectral

output of a memory less channel with the random variables X and Y respectively, the channel capacity is defined as the maximum of the mutual information

C  max IX; Y … … 1

between X and Y :

the channel coefficient, which is a complex Gaussian 1



HH  2 I!

C34567 8  N . log  1 " SNR … … . 3

.Thus

As

A channel is said to memory less if the probability px is the probability

is

reduced

to

(3):

Thus, the capacity increases linearly with the number of N 2: ,

receive antennas.

distribution of the output depends only on the input at

(2)

C34567 8 2:.

Case-2: Increase M and fixed N

that time and is conditionally independent of previous channel inputs or outputs.

Since the Eigen values of HHH and HHH are the same, (2)

distribution function (pdf) of the input symbols X.

can be written as:

2.1 SIMULATED RESULTS

MIMO flat fading channel capacity can be expressed as: SNR  BPS H H () … … … 4

C  E log  det I " M H,

When NR is large, by the law of large numbers !

Case-1: Increase N and fixed M MIMO flat fading channel capacity can be expressed as: C

SNR BPS  E log  det I! " HH  () … … … 2

M H,



I

,

Therefore,

the

C34567 =  M . log  >1 "

!



MIMO

1



HH  2

capacity

SNR? … … . 5

M . However, it has an upper bound that

The above capacity increases logarithmically with depends on the value of N.

increasing When

M 2:, C34567 = 2

! A!B CDE

.

CAPACITY Vs.NO. OF ANTENNA PLOT

CHANNEL CAPACITY (bits/sec/Hz)

600

500

FIXED M,SNR=10dB FIXED N,SNR=10dB FIXED M,SNR=1dB FIXED N,SNR=1dB

400

300

200

100

0 0

is:

50

100

150

NO OF ANTENNAS

Fig. 1(a) Capacity comparison between case 6 and case 7 for SNR 10dB and 1dB. The number of fixed receives antennas for case 7 is 50 antennas.

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JOURNAL OF TELECOMMUNICATIONS, VOLUME 3, ISSUE 1, JUNE 2010

Also, the rate of increase depends on the value of N

M . As shown in Fig.1 (a) and 1(b),

when N F M, the increase in capacity with increasing M

compared to

is more than the linear relation in case 1. However, the

118

logarithmic increase) whenN G M . Therefore, to achieve

rate of increase gets much slower (similar to a channels with increasing number of antennas, N F M .

at least a linear increase in the capacity of MIMO

CAPACITY Vs.NO. OF ANTENNA PLOT CHANNEL CAPACITY (bits/sec/Hz)

150 FIXED M,SNR= -5dB FIXED N,SNR= -5dB FIXED M,SNR= -1dB FIXED N,SNR= -1dB 100

50

0 0

50

100

150

NO OF ANTENNAS

Fig. 1(b) Capacity comparison between case 1 and case 2 for SNR -5dB and -1dB. The number of fixed receives antennas for case 2is 50 antennas.

The average MIMO capacity is shown in Fig. 2 for

transmit antennas on the capacity of MIMO channels. It is

different comparisons. The mean capacity is estimated

apparent from Fig. 2(c) and 2(d) that increasing the

over a range of SNR in Fig. 2(a) and (b). The plot in Fig.

number of receiving antennas has a more significant

2(a) compares three antenna configurations. It is apparent

that when N H M , the mean capacity is greater than the

impact on MIMO capacity than increasing the number of

case for whichN G M. This is mainly due to the constraint

transmitting antennas. Another useful tool used for

on transmitted power which is fixed regardless of the

the capacity over fading channels is random, some

number of transmit antennas. Fig. 2(b) compares the

realizations fall below a capacity threshold (the outage

mean capacity between four flat fading channels. It

capacity) for which reliable decoding of a block of

shows the huge capacity increase of MIMO channels over

information is impossible. The probability that the

SIMO, MISO and SISO channels. Fig. 2(c) and Fig.2 (d)

channel capacity falls below the outage capacity is called

outage probablity  PNC O CPQRSTU V  q , Where XYZ[\]^ is

the

transmitted signal with arbitrarily low number of errors

the outage capacity.

is impossible. The complement of the outage probability

For example, assume that 6 bps/Hz is transmitted over a

is the probability that the capacity is greater than the

fading channel. If the instantaneous capacity of the

outage capacity. In other words, the percentage of good

channel falls below 6 bps/Hz, the transmission will

channels over which reliable communication is possible

violate Shannon’s capacity theorem and decoding the

at a given outage capacity.

illustrate the effect of changing the number of receive and

evaluating MIMO capacity is the outage capacity. Since

outage

probability.

© 2010 JOT http://sites.google.com/site/journaloftelecommunications/

Mathematically

speaking,

JOURNAL OF TELECOMMUNICATIONS, VOLUME 3, ISSUE 1, JUNE 2010 119 MEAN CAPACITY Vs. SNR PLOT

25

20

15

10

5

0 -10

-5

0

5

10

15 SNR(dB)

20

25

30

35

MEAN CAPACITY Vs. SNR

30

MIMO(5 X 5) MISO(6 X 1) SIMO(1 X 6) SISO(1 X 1)

MEAN CAPACITY (bits/sec/Hz)

MEAN CAPACITY (bits/sec/Hz)

30

MIMO(2 X 2) MIMO(4 X 4) MIMO(3 X 3) MIMO(6 X 6)

25 20 15 10 5 0 -10

40

-5

0

5

10

15 SNR(dB)

(a)

20

25

30

35

8

9

40

(b)

Fig.2 (a) and (b) Mean capacity comparisons for MIMO channels. MEAN CAPACITY Vs. TRANSMIT ANTENNA

MEAN CAPACITY Vs. RECEIVER ANTENNA

40 CHANNEL CAPACITY (bits/sec/Hz)

CHANNEL CAPACITY (bits/sec/Hz)

N = 20 35 N =10 30 25

N=5

20 15 N=1

10 5 0 0

1

2

3

4 5 6 7 TRANSMITTING ANTENNAS

8

9

M = 20

45 40 35

M = 10 30 25 M=5

20 15 10

10

(c)

M=1

5 0 0

1

2

3

4 5 6 RECEIVER ANTENNA

7

(d)

Fig.2 (c) and (d) Mean capacity vs. Transmit antennas and Receive antennas at SNR 10dB. 3. SYSTEM MODEL FOR MULTICARRIER SYSTEMS: Consider a single user wireless channel employs M transmits and N receive antennas. It consists of MN elements that represent the MIMO channel coefficients. The multiple transmit and receive antennas could belong to a single user modem or it could be distributed among different users. The M transmit antennas transmit M synchronous data streams at the same radio frequency carrier frequency. The channel is assumed to be frequency flat Rayleigh fading. A block diagram of the system under consideration can be seen in Fig.3. Assuming ideal demodulation to baseband, the receiver signal can be expressed as:

P rk  ` abM Hsk " ηk … . . 6

Where, Pa is the power at the transmitter and k denotes the time index. The vector rk is the size N received signal vector..r1 k , r k … . r! k 0a , Where rD k denotes the received signal at receiving antenna N. sk is the quadrature amplitude modulation (QAM) transmission vector .s1 k , s k … . s k 0a of size M, Where sf k

denotes the transmitted QAM symbol at antenna M . The matrix H is the M x N channel matrix where the element at row n and column m, hmn denotes the channel response at receiver n due to transmitter m. The NM channels are statistically independent, identically distributed random variables. The vector ηk , which equals .η1 k , η k … . η! k 0a , represents additive white Gaussian noise at the receiver with Zero mean and variance g  where ηD is the noise received at the n-th antenna.

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JOURNAL OF TELECOMMUNICATIONS, VOLUME 3, ISSUE 1, JUNE 2010

M Transmitter

decoder

Rayleigh Fading Channel

coder

Data

spatial processing

120

Data

N Receiver

Fig.3 A diagram of a single user MIMO wireless system using M transmitter antennas and N receiver antennas.

3.1 NOVEL FULL-DIVERSITY FULL- MULTIPLEXING SYSTEMS

In this section the three main algorithms will be introduced and explained in turn. These are V-BLAST algorithms, STBC scheme and hybrid BLAST STBC (multilayer STBC) scheme. This paper focuses on bandwidth efficient advances for MIMO systems, covering three major areas. The first area considers a layered architecture that has transmit diversity at each layer [9], termed a multi-layered space time code. This architecture combines spatial multiplexing and transmits diversity and it bridges the gap between these two MIMO systems. The focus in this part is to how the multilayered system compares to other MIMO systems, such as V-BLAST and space time block codes. Furthermore, we propose and compare hybrid BLAST STBC detection algorithms which are based on multi-user detection theory.

received matrix over T time slots, where T is the STBC length, is given by:

Y  HS " n, … … . . 7

S1 S Y  j H1, H, … … … Hk l m o " n … 8

n Sk

Where Y is the N.T× 1 received vector, H is the N.T× NG 1transmitted symbols from the ith group, and n is the

orthogonal channels matrix for the ith group, Xi is the NG ×

N.T× 1 AWGN vector.

In the previous section on the Alamouti scheme, it is seen that for 2 transmitter antennas to achieve full diversity, the spectral efficiency of the system is the same as that of a single transmitter antenna. In order to improve the spectral efficiency of the system, a 4 transmitter structure is now considered, where the Alamouti scheme is applied separately to two pairs of antennas. This means that two

3.2 Hybrid BLAST STBC

data streams are spatially multiplexed on two different

The Hybrid BLAST STBC transmitter consists of K parallel space time block encoders which are independent and synchronized (Fig. 4). Each encoder transmits through NG antennas and the receiver has N receive antennas. The total number of transmit antennas is M = K. NG. The MIMO channel is assumed to be an independent Rayleigh flat fading MIMO channel where each coefficient is a complex Gaussian random variable with mean zero and variance of 0.5 per dimension. The

pairs of antennas. The received signal for this transmitter configuration may be written as

Pa r q  r HsAast s1 " ηq … 9 , 4

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Hv,1 r1q Pa Hv, rq m or m n n 4 Hv,! r!q

Hs,1 η1q Hs, ηq o s1 " m 1 o … … 10

n n Hs,! η1q

JOURNAL OF TELECOMMUNICATIONS, VOLUME 3, ISSUE 1, JUNE 2010 121

transmitted simultaneously withy1, and y .

second Alamouti- encoded data stream which is

Hs,D  }

In this equation, the vector x1  jy1, y, , yz, y{ l , where the |

quantities yz and y{ represent the QAM symbols for the

hD,z h€D,{

hD,{  … … . 11

h€D,z

x11

STBC s1

G1

y1

x1M

y2

yN-1

xk1

yN

STBC Sk

Gk

Hybrid BLAST STBC Detector

x1

xŽ

xkM MIMO Fading Channel

FIG.4: Architecture of Hybrid

Blast STBC System. Cƒ‚s„vAa  log  det >I "

…†

σE

Ha H? bits⁄sec /Hz … … 12

Unlike the two symbol pairs (s1, s, andsz, s{ ) interfere

with one another for STBC, so simple linear decoding is

In this formula det ( ) denotes the matrix determinant

no longer optimum. However, the form of equation (9)

operation. This formula assumes that the transmitter

directly to detect the data symbols s1‚ s{ .As with the

possesses no knowledge of the channel matrix H. In

means that the V-BLAST algorithm can be applied Alamouti scheme the structure of the dual Alamouti scheme means that s1 and s2 do not interfere with one dimension of r in equation (9) is 2N, which means that

another, which is also the case for s3 and s4 . The ′

the transmissions of 4Tx antenna can be successfully decoded with only 2Rx antennas. 3.3. SHANNON CAPACITY COMPARISONS

order to calculate the capacity of the Alamouti scheme, However, the vector ‹ ′ is measured over two consecutive equation (12) can also be applied to this system. symbol periods. For consistent results, the effective

bandwidth of the system must be divided by two in compensation. So, the following result is obtained Cv„vŒa 

1 log  det I 

"

Pa a Pa γ H H (  log  1 "  ( … … … … … 13

2σ v v 2σ

The RHS of this equation may be obtained from the LHS In this section, Shannon capacity results for the three algorithms under consideration will be revised. Under

product Hva Hv . Again the capacity of the Hybrid-Blast by noticing the orthogonal structure of the matrix

assumption of unit bandwidth, the Shannon capacity of

scheme may be obtained by noticing that equation (10)

the MIMO system shown in equation (6) is given by the

has the same general form as (6).As with the Alamouti

formula [10]:

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JOURNAL OF TELECOMMUNICATIONS, VOLUME 3, ISSUE 1, JUNE 2010 122

compensate for r ′ being measured over two consecutive

CHANNEL CAPACITY Vs. SNR MIMO SYSTEM

scheme ,the bandwidth must be scaled by factor of two

equation is:

CsB‚s„vAa 

1 log  det I{ 

"

Pa a H H ( … … … … … 14

4σ  

The matrix HsB‚s„vAa is defined in equation

(10).The equations for Cƒ‚s„vAa  CsB‚s„vAa may be

CHANNEL CAPACITY (bits/sec/Hz)

symbol periods. This time, the resulting capacity

25 20 15 10 5 0 0

evaluated to compare the achievable Shannon capacities

V-BLAST(2x2) STBC(2x2) HYBRID(4x2)

5

10

15

of the three systems.

30

35

40

(Alamouti) In addition, the optimal MIMO capacity is included as a reference. For Hybrid BLAST STBC, each component code is a rank two Alamouti STBC. The capacity of the different systems is estimated by Gaussian

channel

CHANNEL CAPACITY (bits/sec/Hz)

algorithms of Hybrid BLAST STBC, V-BLAST and STBC

complex

CHANNEL CAPACITY Vs. SNR MIMO SYSTEM

25

This section compares the capacities of the detection

random

25

Fig.5

3.4 SIMULATION RESULTS

generating

20 SNR(dB)

20 15 10 5 0 0

realizations from which the instantaneous capacity is

V-BLAST(2x4) STBC(2x4) HYBRID(4x4)

5

10

15

20 SNR(dB)

25

30

35

40

calculated and then the bit error ratio (BER) vs SNR performance of the different schemes is compared with

Fig.6

the capacity results. One main difference between Hybrid BLAST STBC and V-BLAST at the same number spatial diversity than the later while the later has more layers. For example, with a 4×4 MIMO system, Hybrid BLAST STBC has two layers and each layer has a transmit diversity of two. At the receiver, the first detected layer has a receive diversity of three. This is because the detector needs one antenna to null out one interfering layer and the rest provide diversity. On the

CHANNEL CAPACITY (bits/sec/Hz)

of transmit-receive antennas is that the earlier has more

50 40

CHANNEL CAPACITY Vs. SNR MULTI-CARRIER SYSTEMS V-BLAST(4x4) STBC(4x4) HYBRID(8x4) HYBRID(16x8)

30

HYBRID

20 10 0 0

5

10

15

20 SNR(dB)

25

30

35

40

other hand, V-BLAST has four layers and no transmits diversity. In addition, the first detected layer has no

Fig.7

receive diversity because the algorithm needs three antennas to null out three interfering layers

Fig .5 - Fig. 7 Shannon capacity for 1% outage vs. SNR performance of the three schemes under consideration for MIMO system.

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JOURNAL OF TELECOMMUNICATIONS, VOLUME 3, ISSUE 1, JUNE 2010 123

formulas for Cv„vŒa  CsB‚s„vAa in section 3.3 are In this section, the results obtained from evaluating the compared.

outage probablity

10

10

10

10

0

This is done by generating 10,000 sample H matrices and using these two evaluate the channel capacity at different SNRs.

OUTAGE CAPACITY VS SNR FOR MULTI CARRIER SYSTEMS V BLAST ML STBC MIMO STBC

-1

-2

-3

-5

0

5

10 15 SNR(dB)

20

25

30

Fig.8 Outage capacity vs. SNR for multicarrier system The results are presented as 15 outage capacity – that is,

certain number of layers, a reduction in capacity occurs

the capacity exceeded for 99% of all channel realizations.

especially when M=2N in Hybrid BLAST STBC and when

The results for two receive antennas are presented in

M=N in V-BLAST. This is a result of receive diversity

Fig.5. In this case it can be seen that the (4,2) Hybrid

reduction caused by the nulling operation in the

BLAST STBC scheme provides a distinct performance

detection algorithms of both systems. In other words, the

advantage over the (2,2) V-Blast or STBC(Alamouti)

capacity could be maximized by selecting the best

schemes at high SNRs . In part of the Fig 6 and 7 results

number of layers at a given SNR. As a heuristic rule

for four receiver antennas are presented. It can be seen

inferred from the plots, if the intended region of

that at low SNR the (4,4) V-Blast and Hybrid BLAST

operation is at high SNRs, set the number of layers (K) to

STBC schemes achieve similar capacity results. However,

N - 1. On the other hand, if the region of operation is at

at higher SNRs,(16,8) V-Blast begins to out-perform the

low and moderate SNRs, set K to be equal to N/2.

Hybrid BLAST STBC scheme. Both of these techniques perform better than (4, 4) STBC or V-Blast. Thus hybrid

CONCLUSION

method attains superior diversity gain performance to VBLAST and can out form V-blast at spectral efficiencies of

The paper has compared the unique outage capacity

practical interest. Furthermore, at low SNRs and low

performances of V-BLAST, the STBC (Alamouti) and

outage probabilities, hybrid is more spectrally efficient

Hybrid BLAST STBC scheme. The goal is to examine the

depending on the increasing order of the antennas. The

optimal performance and the spatial multiplexing and

capacities of Hybrid BLAST STBC and V-BLAST first

diversity tradeoffs and their relation with the detection

increase when adding more layers as expected but after a

algorithm. The results for the Shannon capacity of the

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JOURNAL OF TELECOMMUNICATIONS, VOLUME 3, ISSUE 1, JUNE 2010 124

three systems shows that for two receive antennas; Hybrid BLAST STBC provides the best performance. Also the results show that Hybrid BLAST STBC is more spectrally efficient at low as well as high SNR by simultaneously

transmitting

symbols

through

all

transmit-antennas without introducing any structure at the transmitter to aid detection at the receiver and at low outage probabilities than VBLAST. Furthermore, since Hybrid BLAST STBC has more transmit-receive diversity, it is more power efficient but it suffers from poor power efficiency and error propagation. Therefore, Hybrid BLAST STBC makes a good candidate in order to

Wireless Systems,” Signals, Systems & Computers,1998. Conference Record of the Thirty-Second Asilomar Conference on , Volume: 2 , Pages:1803 – 18, 1-4 Nov. 1998 . [7] M. Mohammad, S. Al-Ghadhban, B. Woerner, and W. Tranter.“Comparing Decoding Algorithms for Multi-Layer Space-Time Block Codes,” SoutheastCon, Proceedings. IEEE, pp. 147 – 152, 2004. [8] S. Al-Ghadhban and B. Woerner, “Iterative Joint and Interference Nulling/Cancellation Decoding Algorithms for Multi-Group Space Time Trellis Coded Systems,” WCNC. 2004 IEEE ,Volume: 4 ,pp.2317-2322, 21-25 March 2004 [9] V. Tarokh, A. Naguib, N. Seshadri, A.R. Calderbank, "Combined array processing and space-time coding ", Information Theory, IEEE Transactions on, vol. 45, pp.1121 -1128, May 1999.

suppress and cancel interfering signals before detecting the desired signal and for low power high data rate wireless applications.

ACKNOWLEDGEMENT Authors would like to thank to the contribution of Prosenjit Kumar Sutradhar pursuing B.Tech in the Department of Electronics & Communication Engineering at College of Engineering and Management, Kolaghat, under WBUT in 2011, W.B, India for his dedication and sincere support in completing this project.

REFERENCES [1] J. H. Winters, “Optimum combining in digital mobile radio [2]

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[5] [6]

with cochannel interference”, IEEE J. Sel. Areas Commun., Vol. SAC-2, no. 4, pp. 528–539, (Jul. 1984. G. J. Foschini, “Layered space-time architecture for wireless communication in a fading environment when using multi-element antennas”, Bell Labs. Technology. Journal, Vol. 1, No.2, PP. 41-59(1996). I.E. Telatar, “Capacity of multi-antenna Gaussian channels,” Eur. Transaction on Telecommunication ,vol. 10, No. 6, PP. 585–595(1999). P. W. Wolniansky, G. J. Foschini, G. D. Golden, and R. A. Yalenzuela, “V-BLAST: an architecture for realizing very high data rates over the rich-scattering wireless channels,” International Symposium on Signals,Systems, and Electronics, pp. 295-300, 1998. V. Tarokh, H. Jafarkhani, and A. R. Calderbank, “SpaceTime Block Codes from Orthogonal Designs”. IEEE Trans. On Information Theory, VOL. 45, NO. 5, July 1999. A. Naguib, N. Seshadri, and A.R. Calderbank, “Applications of Space-Time Block Codes and Interference Suppression for High Capacity and High Data Rate

Prof. Nirmalendu Bikas Sinha received the B.Sc (Honours in Physics), B. Tech, M. Tech degrees in Radio-Physics and Electronics from Calcutta University, Calcutta,India,in1996,1999 and 2001, respectively. He is currently working towards the Ph.D degree in Electronics and Telecommunication Engineering at BESU. Since 2003, he has been associated with the College of Engineering and Management, Kolaghat. W.B, India where he is currently an Asst.Professor is with the department of Electronics & Communication Engineering & Electronics & Instrumentation Engineering. His current research Interests are in the area of signal processing for high-speed digital communications, signal detection, MIMO, multiuser communications,Microwave /Millimeter wave based Broadband Wireless Mobile Communication ,semiconductor Devices, Remote Sensing, Digital Radar, RCS Imaging, and Wireless 4G communication. He has published large number of papers in different national and international Conference and journals.He is currently serving as a reviewer for Wireless communication and RADAR system in different international journals. .

Sourav Chakraborty is pursuing B.Tech in the Department of Electronics & Communication Engineering at College of Engineering and Management, Kolaghat, under WBUT in 2011, West Bengal, India. His areas of interest are in Microwave /Millimeter wave based Broadband Wireless Mobile Communication and digital electronics. He has published multiple publications in international journals.

Dr. Rabindranath Bera is a professor and Dean (R&D), HOD in Sikkim Manipal University and Ex-reader of Calcutta University, India. B.Tech, M.Tech and Ph.D.degrees from Institute of Radio-Physics and Electronics, Calcutta University. His research areas are in the field of Digital Radar, RCS Imaging, Wireless 4G Communications, Radiometric remote sensing. He has published large number of papers in different national and international Conference and journals.

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Capacity enhancement of 4G- MIMO using Hybrid ...

Capacity enhancement of 4G- MIMO using Hybrid Blast ..... Hybrid BLAST STBC provides the best performance. ... Wireless Mobile Communication and digital.

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