WWW.IJITECH.ORG
ISSN 2321-8665
Vol.03,Issue.03,
July-2015,
Pages:0338-0342
Estimation of MIMI-OFDM Channels Based On Different Modulation
Techniques using Conventional and Wavelets
B. NAGARJUN SINGH1, E. SURESH2
1
Associate Professor, Sarada Institute Technology and Science, TS, India, E-mail: [email protected].
2
PG Scholar, Sarada Institute Technology and Science, TS, India, E-mail: [email protected].
Abstract: Upcoming of the 4th generation LTE (Long Term
Evolution) which is a standard of the wireless communications that are engaged with the two techniques that are
namely Orthogonal Frequency Division Multiplexing
(OFDM) and Multiple Input and Multiple Output (MIMO).
Comparing with Frequency Division Multiplexing (FDM),
we are providing a higher level of spectral efficiency by using
the OFDM Multiple Carriers. To overcome the problems of
the Inter carrier interference (ICI) and inter symbol
interference (ISI), using of the cyclic prefix which uses the
available bandwidth of 20% for the loss of the orthogonality
between the sub carriers in OFDM. Providing of better
orthogonality which is based on the wavelet of OFDM and
improving of BER (Bit Error Rate) is also used in it.
Increasing of the spectral efficiency we don’t require the
cyclic prefix which is based on the wavelet system. In the
upcoming of the 4th generation LTE, using of wavelets in
place of Discrete Fourier Transform (DFT) based OFDM is
proposed. Using of the wavelets and DFT based OFDM
Systems we have compared the performance of the BER.
Keywords: LTE, OFDM, DFT, Wavelet, BER.
I. INTRODUCTION
The requirement for higher data speed is exponentially
increasing, main reason being the availability of smart
phones, at low cost and social networking websites. Constant
improvement in wireless data rate is in demand. Long Term
Evolution-Advanced (LTE-A) is the solution for wireless
broadband services. LTE-Advanced also known as 4G
wireless networks and it is an evolution of LTE Rel-8. IMTAdvanced (International Mobile TelecommunicationAdvanced) refer to a family of mobile wireless technologies,
which is also known as 4G. In 2010, LTE- Advanced/4G is
ratified as IMT-Advanced technology. It will allow the
cellular provider to complement their 3G services by offering
higher data rates, lower latency and packet –based network.
The standard for LTE was first published in 2005 as Rel-6 by
3GPP (third generation partnership project) since then LTEAdvanced standard been in development and finally in March
2009 it was finalized by 3GPP. Provides an overview of LTEAdvanced items and its requirements there are significant
amount of improvement that were made to be qualified as
LTE Advanced. To improve the user experience 3GPP is
considering various aspects which include higher order
MIMO, carrier aggregation, and a deployment strategy called
heterogeneous network. Het Net combines macro-cell,
microcell, relays, Pico-cell, and Fem to-cell deployment in a
single cell to increase spectral efficiency per unit area. It will
also provide better broadband experience in a cost effective
manner to users. The 4G technology can also significantly
increase the spectral efficiency by adapting carrier
aggregation that supports the bandwidth from 1.4MHz to
20MHz. In carrier aggregation multiple component carriers
can be jointly used for transmission to/from user equipment.
It is done such a way that it will be compatible with the
previous releases of LTE.
The fourth generation (4G) of wireless cellular systems has
been a topic of interest for quite a long time, probably since
the formal definition of third generation (3G) systems was
officially completed by the International Telecommunications
Union Radio communication Sector (ITU-R) in 1997. A set
of requirements was specified by the ITU-R regarding
minimum peak user data rates in different environments
through what is known as the International Mobile
Telecommunications 2000 project (IMT-2000). The
requirements included 2048 kbps for an indoor office, 384
kbps for outdoor to indoor pedestrian environments, 144 kbps
for vehicular connections, and 9.6 kbps for satellite
connections. With the target of creating a collaboration entity
among different telecommunications associations, the 3 rd
Generation Partnership Project (3GPP) was established in
1998. It started working on the radio, core network, and
service architecture of a globally applicable 3G technology
specification. Even though 3G data rates were already real in
theory,
initial
systems
like
Universal
Mobile
Telecommunications System (UMTS) did not immediately
meet the IMT- 2000 requirements in their practical
deployments. The combination of High Speed Downlink
Packet Access (HSDPA) and the subsequent addition of an
Enhanced Dedicated Channel, also known as High Speed
Uplink Packet Access (HSUPA), led to the development of
the technology referred to as High Speed Packet Access
(HSPA) or, more informally, 3.5G.
Copyright @ 2015 IJIT. All rights reserved.
B. NAGARJUN SINGH, E. SURESH
Motivated by the increasing demand for mobile broadband
DFT-based channel evaluation methods allow a declining
services with higher data rates and Quality of Service (QoS),
of the distortion component owing to operations in the
3GPP started working on two parallel projects, Long Term
different domains, to achieve higher evaluation accuracy. In
Evolution (LTE) and System Architecture Evolution (SAE),
fact, after removing the unused subcarriers, the LS estimates
which are intended to define both the radio access network
are first converted into the time domain by the IDFT (inverse
(RAN) and the network core of the system, and are included
discrete Fourier transform) algorithm. A smoothing filter is
in 3GPP Release 8. LTE/SAE, also known as the Evolved
then applied in the time domain assuming that the utmost
Packet System (EPS), represents a radical step forward for
multi-path delay is kept within the cyclic prefix (CP) of the
the wireless industry that aims to provide a highly efficient,
symbol. Because of this consequence, the distortion power is
low-latency, packet optimized, and more secure service. The
compact in the time domain. Lastly the DFT is applied to
main radio access design parameters of this new system
return to the frequency domain. In a realistic context, only a
include OFDM (Orthogonal Frequency Division Multiplexsubset of M subcarriers is modulated among the N due to the
ing) waveforms in order to avoid the inter-symbol
insertion of null subcarriers at the spectrum’s extremities for
interference that typically limits the performance of highRF mask requirements. The application of the smoothing
speed systems, and MIMO (Multiple-Input Multiple-Output)
filter in the time domain will lead to a loss of channel power
techniques to boost the data rates. At the network layer, an
when these non-modulated subcarriers are present at the
all-IP flat architecture supporting QoS has been defined. In
border of the spectrum. That can be confirmed by calculating
this paper we have compared the performance of wavelets
the time domain channel response. The time domain channel
based OFDM system with performance of conventional
response of the LS estimated channel. In OFDM methods,
OFDM system for different LTE modulation techniques. For
when null carriers are inserted at the spectrum extremities,
wavelet based system we have used daubechies2 and haar
the concert of the DFT based channel evaluation is degraded
wavelets. Additive White Gaussian Noise (AWGN) channel
especially at the borders of the modulated subcarriers. This
is used for transmission. The paper is organized as first of all
phenomenon is called the “border effect”. This effect is also
the conventional OFDM system and wavelet based OFDM
observed in MIMO context. In order to evaluate the DFT
system. The proposed wavelet based OFDM design is
based channel evaluation, the mean square error (MSE)
presented and then the performance evaluation and the results
concert for the different modulated subcarriers.
obtained from the simulation are discussed and Conclusion is
summarized.
III. PROPOSED METHOD
Wavelet Transform is a significant mathematical function,
because as a tool for multi resolution dissolution of
continuous time signal by different times and frequencies. In
wavelet transform, higher frequencies are sophisticated
decided in time, as well as lesser frequencies are better
decided in frequency. Happening this intellect, the signal
remains reproduced through an orthogonal wavelet intention,
in growth the transform is calculated alone changed parts of
the time domain signal. The wavelet transform can be
classified as two categories, continuous ripple transform and
discrete ripple transform. The Discrete Ripple Transform
could be observed by way of sub-band coding. The signal is
analyzed and it accepted over a filter bank succession. A subband coding method is defined as full-band source signal is
Fig.1. DFT based OFDM transmitter and receiver
spitted into distorted frequency bands as well as encrypt
every band separately established on their spectrum energy.
II. EXISTING METHOD
The sub-band coding methodology learning starts from the
The DFT-based channel evaluation technique has been
digital filter bank method; it can be defined as a set of filters
derived to improve the concert of LS or MMSE channel
with has distorted centre frequencies. Double channel filter
evaluation by eliminating the effect of distortion outside the
bank is mostly used in growth the effective way to tool the
utmost channel delay. The estimate of channel gain at the k th
discrete ripple transform. Generally, the filter bank plan has
subcarrier, obtained by moreover LS or MMSE channel
double steps which are used in signal transmission scheme.
estimation method. Taking the IDFT of the channel estimate,
Application of DFT on LS, MMSE channel evaluation can
The first step is named as analysis stage which agrees
improve the concert of estimators by eliminating the
toward the decomposition procedure by using down sampling
distortion effects. In this OFDM method, the period of the
the signal samples remains condensed. Synthesis interval is
channel impulse response is usually less than the period of
the next step which agrees to the exclamation procedure in
the cyclic prefix L. DFT-based algorithm uses this aspect to
which the signal samples are improved by two (up sampling).
increase the concert of the MMSE and LS algorithms. It will
The analysis interval involves of sub-band filter inspective by
transformed into the frequency channel evaluation into time
down sampler while the synthesis interval involves of subchannel evaluation using IDFT, considers the part which is
band filter up sampler positioned. The sub-band interval used
superior than L as distortion, and then treats that part as zero
through the channel filter exists perfect restoration.
in order to eliminate the impact of the distortion.
Consequently there are high pass filter as well as low pass
International Journal of Innovative Technologies
Volume.03, IssueNo.03, July-2015, Pages: 0338-0342
Estimation of MIMI-OFDM Channels Based On Different Modulation Techniques using Conventional and Wavelets
filters at each stage, the interval analyses takes double output
as compared to the traditional Fourier based methods.
coachable also they are named as estimate coachable which
COIFLET Wavelets are small waveforms with a set
contain the small frequency information of the signal then
oscillatory structure that is non-zero for a limited interval of
detail coachable which comprise the high frequency data of
time (or space). By using wavelet bases, wavelet filters are
the signal. The analysis interval of the multi-level double
characterized. These signal transmission techniques allow for
channels impeccable restoration filter bank scheme is charity
significant increase in wireless technique without increase in
for formative the DWT coachable. The procedure of
bandwidth. DFT based OFDM is a Multi-Carrier Modulation
restoration the basis signal as of the DWT coachable is so(MCM) scheme where the sub carriers are orthogonal. The
called the inverse discrete Ripple transform (IDRT). Aimed at
rectangular window used in its implementation creates high
each level of restoration filter bank the calculation then
side lobes. Whereas, DWT-OFDM has longer basis functions
details coachable are up sampled in growth to pass over low
and hence can offer higher degree of side lobe suppression.
pass filter and high pass synthesis filter. Discrete Wavelet
The transmitted signal x[k] is composed of modulated
Transform is designed as high presentation digital signal
symbols successively, as the sum of M waveforms are
processing method for procedure in applying multicarrier
constructed individually. In DWT-OFDM, the discrete
modulation.
functions si (k) is the complex exponential basis functions.
The transmitted symbol is built by performing inverse DWT
The block diagram plan of multicarrier transceiver
while the forward DWT is used to retrieve the data symbol.
arithmetical method constructed on DWT the method project
The carrier waveforms are obtained by iteratively filtering the
include of an inverse discrete wave-let transform (IDWT) as
signal into high and low frequency components. The
modulator at the transmitter as well as a discrete ripple
affiliation between the number of iterations J and the number
transform (DWT) as demodulator at the side of receiver. The
of carrier waveforms M is given by M 2J. In literature survey
leading plus the vital adaptation among the conventional
hardly they concentrate on any wavelets that are renowned by
OFDM as well as DWT multicarrier scheme is the removal of
many authors. Some distinctive characteristics of every
the cyclic prefix blocks in the transmitter otherwise in the
wavelet make it more suitable for one application than other.
receiver parts. The assets of wavelets in growth to varieties it
While designing a method the alert consideration of different
by way of a ethical outstanding for numerous applications
wavelet properties should be made with respect to the method
identical separation in image, nuclear, biomedical, magnetic
necessities. The selection of wavelets is generally made on
resonance imaging, music, fractals, turbulence, pure
the following wavelet properties:
mathematics, data compression, computer graphics also
animation, human vision, radar and an deep description for
Support: Compact support is defined by the span (L) of the
growth applications remained offered There are several
filter. Shorter filters have decreased computational
advantages of using COIFLET wavelets for wireless
complexity.
communication methods. The hardly any desirable features of
wavelets are the following:
Orthogonality: It is one of the most vital wavelet properties
1. Wavelet transform can generate subcarriers of different
as it ensures perfect renovation. For communication purposes
bandwidth and symbol span.
we absolutely require orthogonal wavelets.
2. The capability of wavelets to display the time frequency
tiling in a manner that minimizes the channel
Symmetry: Symmetrical wavelets have a feature that
disturbances minimizes the effect of distortion and
transform of the mirror of an image is the same to the mirror
intrusion on the signal.
of the wavelet transform. None of the orthogonal wavelets
3. Wavelets give a new aspect, signal diversity which could
except COIFLET wavelet is symmetric.
be exploited in a cellular communication method, where
adjacent cells can be designated different wavelets in
K-Regularity/Vanishing Moments: K-regularity is also an
order to minimize inter-cell intrusion.
significant measure for wavelets because it helps to reduce
4. Wavelet-based algorithms have long been used for data
non-zero coachable in the high pass sub-bands and it is one of
compression. By compressing the data, a compact
the easiest ways to resolve if a scaling function is fractal or
volume of data is transmitted so that the communication
not.
power needed for transmission is compact.
5. Mitigation of Intrusion ISI and ICI: ISI (Inter symbol
The same modulator is used in QPSK, however binary
intrusion) and ICI (Inter Carrier Intrusion) are inclined
information in both I and Q channels, as described above.
by shape of the basic pulse. Time dispersion contributes
Each message has two levels i.e., ±V volt respectively. The
intrusion due to multipath effect and frequency
amplitude of the output DSBSC does not vary for a non-band
dispersion due to non-linear effects of radio channel. In
limited message. When the message changes polarization is
wireless scenario the channel effects cannot be
interpreted as a 1800 phase shift, given to the DSBSC. Thus
controlled. But the pulse shape can be alertly designed to
the signal in each arm is said to be undergoing a phase shift
have minimum distortion for a given delay spread. The
keying, or 1800 phase shift. Since there are two PSK signals
wavelet transform allows more flexibility in the design of
mixed, in quadrature, the two-channel modulator gives rise to
the pulse shape.
a quadrature phase shift keyed - QPSK signal. 16QAM as
well as full-rate 16QAM and the criterion used for adapting
Many researchers proved that the wavelet based
the modem modes was based on the instantaneous channel
multicarrier schemes are advanced in suppressing ICI and ISI
delay spread and received signal to distortion ratio. For
International Journal of Innovative Technologies
Volume.03, IssueNo.03, July-2015, Pages: 0338-0342
B. NAGARJUN SINGH, E. SURESH
gradually varying channel quality of the uplink (UL) and
and Fig. 5 that the BER performance of wavelet based OFDM
downlink (DL) was rendered similar by utilizing short frame
is better than the DFT based OFDM. Fig. 3 indicates that db2
duration Time Division Duplex (TDD) and the utmost
performs better when QPSK is used. Fig. 4 shows that when
normalized delay spread simulated was 0:1. A variable
16-QAM is used db2 and haar have similar performance but
channel coding rate was then introduced by Matsuoka et al. in
far better than DFT. Fig. 5, where 64-QAM is used haar and
combination with adaptive modulation. In reference,
db2 performs better than DFT
wherever the transmitted burst incorporated an outer Reed
Solomon code and an inner convolution code in order to
achieve high-quality information transmission and coding
rate can changed according to the prevalent channel quality
using the same method, as in adaptive modulation in order to
achieve a certain target BER concert. A so-called channel
margin was introduced in this contribution, which effectively
increased the switching thresholds for the sake of preempting
the effects of channel quality evaluation errors, although this
inevitably compact the achievable BPS throughput. For
domestic broadcast applications for example, 64 QAM and
256 QAM are frequently used in digital cable television and
cable modem applications.
IV. BER PERFORMANCE EVALUATION
By using MATLAB performance characteristic of DFT
based OFDM and wavelet based OFDM are obtained for
different modulations that are used for the LTE, as shown in
Figs 3-5. Modulations that could be used for LTE are QPSK,
16 QAM and 64 QAM (Uplink and downlink). QPSK does
not carry data at very high speed. When signal to noise ratio
is of good quality then only higher modulation techniques can
be used.
Fig.3. BER performance of wavelets and DFT based
OFDM system using QPSK modulation.
Fig.4. BER performance of wavelets and DFT based
OFDM system using 16-QAM modulation.
Fig.2. Wavelet based proposed OFDM system design.
Lower forms of modulation (QPSK) does not require high
signal to noise ratio. For the purpose of simulation, signal to
noise ratio (SNR) of different values are introduced through
AWGN channel. Data of 9600 bits is sent in the form of 100
symbols, so one symbol is of 96 bits. Averaging for a
particular value of SNR for all the symbols is done and BER
is obtained and same process is repeated for all the values of
SNR and final BERs are obtained. Firstly the performance of
DFT based OFDM and wavelet based OFDM are obtained for
different modulation techniques. Different wavelet types
daubechies2 and haar is used in wavelet based OFDM for
QPSK, 16-QAM, 64-QAM. It is clear from the Fig. 3, Fig. 4
Fig.5. BER performance of wavelets and DFT based
OFDM system using 64-QAM modulation.
International Journal of Innovative Technologies
Volume.03, IssueNo.03, July-2015, Pages: 0338-0342
Estimation of MIMI-OFDM Channels Based On Different Modulation Techniques using Conventional and Wavelets
V. CONCLUSION
Author’s Profile:
In this paper we have a tendency to analyze the performance
of rippling primarily {based} OFDM system and compared it
B. NAGARJUN SINGH, Associate
with the performance of DFT based OFDM system. From
Professor, Sarada Institute Technology
system under different channel conditions”, the performance
and Science, TS, India, E-mail:
curve we've determined that the BER curves obtained from
[email protected].
rippling primarily {based} OFDM area unit higher than that
of DFT based OFDM. We have a tendency to used 3
modulation techniques for implementation that area unit
QPSK, 16QAM and 64QAM, that area unit utilized in LTE.
In rippling based mostly OFDM differing kinds of filters are
often used with the assistance of various wavelets offered.
We’ve used daubechies2 and haar wavelets, each offer their
E. SURESH, PG Scholar, Sarada Institute
best performances at totally different intervals of SNR.
Technology and Science, TS, India,
E-mail: [email protected].
VI. REFERENCES
[1] Anuradha, Naresh Kumar, “BER analysis of conventional
and wavelet based OFDM in LTE using different modulation
Techniques”, March, 2014.
[2] A. Ian F., G. David M., R. Elias Chavarria, “The
evolution to 4G cellular systems: LTE-advanced”, Physical
communication, Elsevier, vol. 3, no. 4, pp. 217-244, Dec.
2010.
[3] B. John A. C., “Multicarrier modulation for data
transmission: an idea whose time has come”, IEEE
Communications magazine, vol. 28, no. 5, pp. 5-14, May
1990.
[4] L. Jun, T. Tjeng Thiang, F. Adachi, H. Cheng Li, “BER
performance of OFDM-MDPSK system in frequency
selective Rician fading and diversity reception” IEEE
Transactions on Vehicular Technology, vol. 49, no. 4, pp.
1216-1225, July 2000.
[5] K. Abbas Hasan, M. Waleed A., N. Saad, “The
performance of multi-wavelets based OFDM system under
different channel conditions”, Digital signal processing,
Elsevier, vol. 20, no. 2, pp. 472-482, March 2010.
[6] K. Volkan, K. Oguz, “Alamouti coded wavelet based
OFDM for multipath fading channels”, IEEE Wireless
telecommunications symposium, pp.1-5, April 2009.
[7] G. Mahesh Kumar, S. Tiwari, “Performance evaluation of
conventional and wavelet based OFDM system”,
International journal of electronics and communications,
Elsevier, vol. 67, no. 4, pp. 348-354, April 2013.
[8] J. Antony, M. Petri, “Wavelet packet modulation for
wireless communication”, Wireless communication & mobile
computing journal, vol. 5, no. 2, pp. 1-18, March 2005.
[9] L. Madan Kumar, N. Homayoun, “A review of wavelets
for digital wireless communication”, Wireless personal
communications, Kluwer academic publishers- Plenum
publishers, vol. 37, no. 3-4, pp. 387-420, May 2006.
[10] L. Alan, “Wavelet packet modulation for orthogonally
multiplexed communication”, IEEE transaction on signal
processing, vol. 45, no. 5, pp. 1336-1339, May 1997.
[11] K. Werner, P. Gotz, U. Jorn, Z Georg, “A comparison of
various MCM schemes”, 5th International OFDM-workshop,
Hamburg, Germany, pp. 20-1 – 20-5, July 2000.
[12] IEEE std., IEEE proposal for 802.16.3, RM wavelet
based (WOFDM), PHY proposal for 802.16.3, Rainmaker
technologies, 2001.
International Journal of Innovative Technologies
Volume.03, IssueNo.03, July-2015, Pages: 0338-0342