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 hD,{
hD,{ … … . 11
hD,z
x11
STBC s1
G1
y1
x1M
y2
yN-1
xk1
yN
STBC Sk
Gk
Hybrid BLAST STBC Detector
x1
x
xkM MIMO Fading Channel
FIG.4: Architecture of Hybrid
Blast STBC System. CsvAa 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 Cvva
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:
CsBsvAa
1 log det I{
"
Pa a H H ( … … … … … 14
4σ
The matrix HsBsvAa is defined in equation
(10).The equations for CsvAa CsBsvAa 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 Cvva CsBsvAa 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.
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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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