International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 7 - May 2014
VLSI Implementation of Orthogonal Space
Time Block Coding (OSTBC) Based High
Throughput Multiple Modes MIMO
Deepa A and Mrs. Shally S P
PG Scholar, Department of ECE, DMI College of Engineering,
Palanchur, Chennai.
Assistant Professor, DMI College of Engineering, Palanchur, Chennai.
Abstract: Space Time Block Coding, in a wireless
communication system transferring of data over
Long Term Evolution downlink channel using
multiple antennas at the transmitter and
receiver ends which improve reliability of data
transfer. In data transferring, data are first
encoded using a space–time block coding and
encoded data is split into n streams which are
transmitted using transmit antennas. The received
signals from the receiver antenna are disturbed by
noises which are linear superposition of n
transmitted signals. In decoding side we use a
maximum likelihood method instead of joint
detection method to decoupling of the signals
transmitted from different antennas. In addition
to reduce computational cost of solving convex
problem, we use approximate semi-analytical
method. Numerically the results of approximation
are accurate in which the proposed design OSTBC
performs without MIMO modes. Fast fading
channels prefers block-wise decoder whose
coherence time may be short as one OSTBC-LTE
block. Here, in this paper to find frame error rate
(FER), we use MIMO orthogonal space time block
code for 2 Tx and 1 Rx antenna with M-ary psk
trellis coded modulated signal for M-ary PSK
signal over Rayleigh fading channel and Rician
fading channel to without line of sight (LOS)
faded channel and direct line of sight (LOS) faded
channel respectively. Definitively the FER and
gain for OSTBC with TCM and to compare their
performances over Rayleigh fading channel and
Rician fading channel are examined using these
results.
I. INTRODUCTION
In wireless communication, due to analytical
tractability its performance analysis for combining
techniques are identically distributed diversity
branches which leads to shadowing effects and,
consequently, unequal path loss on different
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branches. The transmitter transmits the signal wave
through different paths are interacting with one
another received by the receiver which are in phase
and also sometimes out of phase.
Due to this effect the received signal amplitude
and power increases and decreases respectively
which cause changes in time? Multiple transmit and
receive antennas are used in Space-time coding.
Serially Input data are entering space time encoder,
which are distributed to parallel sub-streams. In the
sub-stream each bits are mapped to signal
waveforms, after that they are emitted from the
antenna to the corresponding sub-stream. In wireless
channel signals are transmitted simultaneously over
each antenna interfere with each other as they
propagate. The fading channel also changes the
signal waveforms. In receiver side, the distorted and
superimposed waveforms detected by each receive
antenna are used to estimate the original data bits.
II. PROPOSED SYSTEM
Traditionally, multipath propagation affects the
wireless communication system. However MIMO
multipath effect is exploited to benefit the user.
Efficient multipath methods are used to separate
parallel streams of data. The effect will be apparent
as per the system model explained as follows.
III. ORTHOGONAL SPACE-TIME BLOCK
CODING
A communication system consists of a transmitter,
receiver and channel. Multiple transmitter and
receiver antennas are used in Space-time coding as
shown in the figure below. . Bits entering the spacetime encoder serially are distributed to parallel substreams. Bits are mapped to signal waveforms in each
sub-stream, then it will emit from the antenna
corresponding to that sub-stream. They propagate
through the wireless channel; Signals transmitted
simultaneously over each antenna interfere with each
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 7 - May 2014
other. The signal waveforms are distorted the fading
channel. To estimate the original data bits, in receiver
antenna side the superimposed and distorted
waveforms are detected by receiver antenna.
A. Notation









j = √−1
x ∗ is the complex conjugate of x.
R(x) is the real part of x.
∠x is the phase of x.
E[X]is the expected value of random
variable X.
XT is the transpose of matrix X.
XH is the conjugate transpose of matrix
X.
I is the n × n identity matrix.
o is the n × n zero matrix.
B. Channel Model
In a space-time system, N intimates the number
of receive antennas and N be the number of transmit
antennas. Assume that we use a block coded system
in which L2M bits enter into the encoder every block
epoch. These bits are mapped to L symbols, and
transmitted over a block of T time intervals with an
M-ary sized constellation. This is said to be an
(N , N ) block coded system with rate R = L=T. A
mathematical model for any space-time block coded
system is given by
R = S. H + N;
Where,
R is a T × N matrix representing the received data.
S is a T × N
symbols.
matrix representing the transmitted
H is a N × N matrix representing quasi-static flat
Gaussian fading.
N is a T × N matrix representing AWGN.
In the channel model (1.1), we only consider AWGN
distortion and fading. AWGN matrix N, its element
are modeled as independent circularly symmetric
(i.e., independent real and imaginary parts) complex
Gaussian random variables with zero variance and
mean, that defines the system signal-to-noise ratio
(SNR).
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The fading matrix, H, is modeled in the same
statistical manner as AWGN with normalized unit
variance. A quasi-static channel is constant, but
changes independently from one block to another
over the duration of a code block. Flat fading implies
a constant power spectral density (PSD) over the
frequency band used by the transmitted symbols. We
assume all antennas in the system are placed
sufficiently far apart for independent fading over
each channel.
C. The Code Matrix
Code matrix S, elements are typically complex
baseband symbols from a PSK or QAM constellation.
A given row represents the information sent in a
single time interval and a given column of S
represents the stream of data sent by a specific
transmit antenna. So that only it is named as “spacetime coding”. In each space-time code block transmit
the average energy which satisfies E[trace(SS )] =
TN E, where E is the average complex baseband
symbol energy.
IV. MIMO
The multiple antennas allow MIMO systems to
perform diversity coding (space-time coding), precoding (multi-layer beam-forming) and spatial
multiplexing. Spatial multiplexing increases network
capacity by splitting a high rate signal into multiple
lower rate streams and transmitting them through the
different antennas. Diversity consists of transmitting
a single space-time coded stream through the all
antennas. Beamforming consists of transmitting the
same signal with different gain and phase over all
transmit antennas such that the receiver signal is
maximized. The receiver can successfully decode
each stream given that the received signals have
sufficient spatial signatures and that the receiver has
enough antennas to separate the streams using spatial
multiplexing. As a result of using MIMO techniques
without any transmit power or bandwidths, long
transmit range or data rate are achieved. In this paper
we are using Orthogonal Space Time Block Code
(OSTBC) with trellis coded modulation (TCM) over
Rayleigh fading channel and Rician fading channel to
improve the data throughput rate, reducing the area
and power to increase its efficiency. Finally, these
STBC techniques are implemented in MATLAB and
analyzed for performance according to their frameerror rates using QPSK, BPSK, 64-QAM, and 16QAM modulation schemes.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 7 - May 2014
Fig.1. MIMO System
The receivers receiving power and consequently
sound to noise ratio can be achieved by
beamforming, a transmitter and receiver pair can
perform beamforming and direct their main beams at
each other. Spatial diversity, to reduce the outage
probability a signal can be coded through the transmit
antennas, creating redundancy. Spatial multiplexing
by using different transmit antenna element, a set of
streams can be transmitted in parallel. To separate the
signals the receiver can perform the appropriate
signal processing.
A. Trellis Coded Modulation (TCM)
In communication field, modulation scheme
which allows highly efficient transmission of
information over band limited channels is said to be
trellis coded modulation. Without compromising
bandwidth efficiency, it allows the achievement of
significant gains over conventional uncoded
multilevel modulation. To generate coded signal
sequence redundant non binary modulation in
combination with a finite state encoder which
governs the selection of modulation signals using
TCM schemes. By using soft decision maximumlikelihood sequence decoder, the noisy signals are
decoded in the receiver. Comparing to conventional
uncoded modulation, Simple four-state TCM
schemes used to improve the robustness of digital
transmission against additive noise by 3 dB. There
are many types of trellis method which can even
reach 6dB of the coding gain. These gains are
obtained without
reduction of the effective
information rate or bandwidth expansion as needed
by old traditional error correction schemes. A
multiple trellis encoder has m binary input bits and u
binary output bits that are mapped into k M-ary
symbols in each transmission symbol.
Fig.2. Multiple Trellis Encoded M-PSK Transmitter
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 7 - May 2014
A multiple Trellis Encoded M PSK Transmitter
block diagram is shown in the following figure. This
system has throughput m/k bits/s/Hz and also the
same bandwidth with 2m/k-point signal constellation.
The partition in the system is carried out as follows:
output bits of u binary encoder are partitioned into k
group of m= log2 M bits each. These symbols results
in an MPSK output symbol. u= k. log2 M whose
parameters u, k, M were chosen.
Let us take sample as r = a + w where it is
real or complex valued (or one or two dimensional
modulation) here a are the discrete signals sent by
the modulator and the sample of an additive white
Gaussian noise process is
w . An optimum
sequence decoder’s decision rule is to determine,
among the set C of all coded signal sequences which
a cascaded encoder and modulator can produce the
sequence {â }with minimum squared Euclidean
distance (sum of squared errors) from {r }that is, the
sequence {â }which satisfies
d
|r − â | = {â }∈∁∑ |r − a |
= { } { }∑|a − b |;{a }, {b } ∈ ∁
the error-event probability. The error-event
probability is generally well approximated byP (e) ≅
N . Q[d /(2σ)], where signal-to-noise ratio is
high. Q (.) represents the Gaussian error integral
∞
Q(x) = ∫ exp(−y /2) dy andN denotes the
√ π
(average) number of nearest neighbor signal
sequences with distance d
that diverge at any
state from a transmitted signal sequence, and remerge
with it after one to more transitions.
V. SIMULATION
In this paper, our main goal is to analysis the
performance of OSTBC with TCM over the Rayleigh
fading channel and Rician fading channel and
compare their results using FER v/s SNR plots with
MIMO modes. So that we have proposed a model
using orthogonal space time block coding and trellis
code modulation technique over Rician fading
channel and Rician fading channel to achieve full
diversity of orthogonal space time block coding and
coding gain of trellis code modulation(TCM). A
simulink model for OSTBC and TCM shows in
following figure
Where a and b are the signal sequence. The error
can be determined in Trellis Coded Modulation by
Fig.3. simulink model for OSTBC and TCM
In above model, we use M transmit and N receive
multiple antenna system for baseband transmission
over Rayleigh fading channel. For the simulation,
again the same process is apply over the Rician
fading channel. For our simulation results, we are
using 2 transmitter and 1reciever antenna. For trellis-
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coded modulation (TCM) we are using M-PSK TCM
Encoder block, which modulates the message data
from the Bernoulli binary generator to a PSK
constellation that has unit average energy. The
Bernoulli binary generator block produces the
information source for the simulation. In MPSK
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 7 - May 2014
Fig.4. RTL Schematic
TCM decoder block, the Viterbi algorithm is uses for
TCM to decode the signals from the OSTBC
combiner. Here we are using 8-PSK constellation
with 8 trellis states.
In our paper, for simulations we use Matlab tools
to calculate the frame error rate (FER) with the
performance of the OSTBC with TCM over Rayleigh
fading channel and Rician fading channel. Here first
a random bit stream is generated through Bernoulli
binary generator. Initially we have to simulate our
model for Rayleigh fading channel and then we
simulate the model for Rician fading channel for
different line of sight (LOS) rician factor K and then
compare their FER performance through FER v/s
SNR plots. To generate the symbols encoding
scheme is used which are to be transmitted through
multipath faded channel then the signal power level
is defined. Here 2×1 fading channel subsystem-based
implementation has to be provided that we first uses
the multipath Rayleigh fading channel then we use
for the Rician fading channel with Rician factor K.
Then estimation of the symbols at the receiver is
done by using maximum likelihood detection. In our
system (Additive white Gaussian noise) AWGN is
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added which is generated using normally distributed
and generated as N (0, 1), where N stands for
normally distributed RV with variance 1 and 0 mean.
By following this process the performance of the
system is calculated at different values of SNR.
Fig.5. FER for M-PSK modulation with OSTBC
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 7 - May 2014
Then the FER Vs SNR curves are plotted under
Rayleigh and Rician fading environment. First we see
the simulation plot of orthogonal space time block
(OSTBC) for MPSK signal over Rayleigh fading
channel and rician fading channel shown in figure 4.
From figure 6, it has been shown that the FER of the
Space time block code gives the better performance
over the Rician fading channel for Rician factor K=1
then the Rayleigh fading channel.
OSTBC with TCM with 2 transmitters and 1 receiver
antenna for MPSK modulation over Rayleigh and
Rician fading channel in figure 5 and figure 6
respectively. Thus from the above comparison, it has
been observed that the proposed scheme is known as
OSTBC with TCM result in lowest FER.
Fig.6. OSTBC with TCM over Rayleigh fading
channel
Fig.8. FER simulation results for OSTBC with TCM.
Initially at lower SNR value the FER for Rician
and Rayleigh fading has minimum difference while
the as increasing of SNR value, the difference of FER
has to be increases approximately 2dB
Fig.7. OSTBC with TCM over Rician fading channel
Now we have seen the FER v/s SNR curves of
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We compare orthogonal space time block code
and the trellis code modulation for both Rayleigh and
Rician fading channel shows that for a given value of
SNR. From the results it has been observed that
orthogonal space time block coding performs better
than trellis code modulation in terms of frame error
rate with MIMO.
Now we have to compare the simulation results of
FER performance for OSTBC with TCM over both
Rayleigh fading channel and Rician fading channel
from figure 7.
From the above the fig we have to compare the
performance of the OSTBC with TCM for Rayleigh
fading channel and Rician fading channel with
different Rician factor K, so that we can conclude
that OSTBC with TCM gives the better performance
over the Rician fading channel for direct line of sight
(LOS) Rician factor K=1and K=2.And also for
K=0,no line of sight(NLOS) in such situation the
OSTBC with TCM performance decreases as
compare to the Rayleigh fading channel where that
channel doesn’t care about the no line of sight path.
Power Dissipation - 31.48mW
Area Utilization
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 7 - May 2014
Family
- Cyclone II
Total logic elements
- 37 / 4,608 ( < 1 % )
Total combinational functions - 14 / 4,608 ( < 1 % )
Dedicated logic registers
- 37 / 4,608 ( < 1 % )
Total registers
- 37
Total pins
- 21 / 89 ( 24 % )
VI. CONCLUSION
The Orthogonal Space Time Coding Block
coding is a technique for MIMO system and produces
full diversity and as well trellis coded modulation is a
band efficient reason for the large coding gain with
low power and covers a small area for the execution.
Finally, we proposed a system to achieve full
diversity of orthogonal space time block coding and
large coding gain of trellis code modulation, a new
technique called orthogonal space time block coding
combined with trellis code modulation with MIMO
has been delivered.
VII. REFERENCE
1.
Sachin Chourasia, DR. Prabhat Pate, “A Comparative
analysis of orthogonal space time Block code with trellis
coded modulation over Rayleigh and Rician fading channel”,
International Journal of Science, Engineering and
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2.
Lori Anne Dalton, “New Orthogonal Space-Time Block
Codes With Full Diversity”, Dec 2002.
3.
V. Tarokh, N. Seshadri and A. R. Calderbank, “Space-time
codes for high data rate wireless communication:
performance criterion and code construction,” IEEE Trans.
Inform. Theory, vol. 44, pp. 744–765, Mar. 1998.Yang Sun,
“Parallel VLSI Architectures for Multi-Gbps MIMO
Communication System”, Rice University, Dec 2010.
4.
Ioannis D. Erotokritou, “space time Block coding For
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Channels”, May 2006.
5.
Luis Miguel Cort, “MIMO Space-Time Block Coding
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6.
G.Ungerboeck, “Channel coding with multilevel/phase
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January 1982.
7.
M.Oerder, “Rotationally invariant trellis codes for M-PSK
modulation,” 1985 Internet Common. Conf. Record, pp-552556, Chicago, June 23-26, 1985.
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G.D. Forney. Jr.,” The Viterbi algorithm,” Proc. of the IEEE,
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