International Journal of Engineering Trends and Technology (IJETT)-Volume 4 Issue 7-July 2013
FPGA Implementation of Wavelet based SCFDMA System
1
Ramya.S, 2C.B. Vinutha, 3 Mr. M. Z Kurian
1 th
4 sem, M.Tech (VLSI&ES), SSIT, Tumkur
2
3
Lecturer, Dept. of E&C, SSIT, Tumkur, Karnataka
Dean & HOD, Dept. of E&C, SSIT, Tumkur, Karnataka
ABSTRACT-Orthogonal Frequency Division Multiple
Access (OFDMA) has recently been applied widely in
wireless communication systems due to its high data
rate transmission capability with high bandwidth
efficiency and its robustness to multi-path fading. But it
has several inherent disadvantages such as the large
PAPR and the sensitivity to Carrier Frequency Offset
(CFO).Hence much attention has been focused on
Single Carrier systems with Frequency-Domain
Equalization (SC-FDE) and SCFDMA systems. Recent
research has shown that the Single Carrier Frequency
Division Multiple Access (SC-FDMA) is an attractive
technology
for
uplink
broadband
wireless
communications, because it does not have the problems
such as the large Peak-to-Average Power Ratio (PAPR)
that is more significant OFDMA. In this paper, an
efficient transceiver scheme for the SC-FDMA systems,
using the discrete wavelet transform is proposed.
Wavelet analysis at the transmitter and the receiver has
the ability to reduce distortion in the reconstructed
signals.
Keywords:
Transform.
SC-FDMA,
I.
OFDMA
and
Wavelet
INTRODUCTION
Single-carrier FDMA (SC-FDMA) is a frequencydivision multiple access scheme (FDMA). Like other
multiple access schemes (TDMA, FDMA, CDMA,
OFDMA), it deals with the assignment of multiple users to
a shared communication resource. The distinguishing
ISSN: 2231-5381
feature of SC-FDMA is that it leads to a single-carrier
transmit signal, in contrast to OFDMA which is a multicarrier transmission scheme. Owing to its inherent single
carrier structure, a prominent advantage of SC-FDMA is
that it’s transmit signal has a lower PAPR resulting in
relaxed design parameters in the transmit path of a
subscriber unit. OFDMA has been applied widely in
wireless communication systems due to its high data rate
transmission capability with high bandwidth efficiency,
and its robustness to multi-path fading. But it has several
inherent disadvantages such as the large PAPR and the
sensitivity to Carrier Frequency Offset (CFO).Hence much
attention has been focused on Single Carrier systems with
Frequency-Domain Equalization (SC-FDE) and SCFDMA
systems. Recent research has shown that the SC-FDMA is
an attractive technology for uplink broadband wireless
communications, because it does not have the problems
such as the large Peak-to-Average Power Ratio (PAPR)
that is found in OFDMA [2].
II. SYSTEM DISCRIPTION
A. BLOCK DIAGRAM
Figure 1 shows a block diagram of SC-FDMA system
using discrete wavelet transform (DWT). The input signal
is modulated and for the real and imaginary outputs
symbols are generated and they are padded with zeros on
both the sides. The resulting signal is transformed by the
wavelet transform via the DWT. The DWT outputs are
mapped by localized sub-carrier mode. After that, add the
cyclic prefix in order to reduce ISI (Inter Symbol
Interference).
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International Journal of Engineering Trends and Technology (IJETT)-Volume 4 Issue 7-July 2013
decomposed signal into its original transmitted form
without deterioration. The DWT (Discrete Wavelet
Transform) is computed by successive lowpass and
highpass filtering of the discrete time-domain signal. The
Haar wavelet is the simplest type of wavelet transforms. In
discrete form, Haar wavelets are related to a mathematical
operation called the Haar transform . Like all wavelet
transforms, the Haar transform decomposes a discrete
signal into two levels of half its length. At each level, the
highpass filter produces detail information denoted by
d(m), while the lowpass filter associated with a scaling
function produces coarse approximations denoted by a(m) .
The filtering and decimation process is continued until the
desired level is reached. The maximum number of levels
depends on the length of the signal. The DWT of the
original signal is then obtained by concatenating all the
coefficients, a (m) and d (m), starting from the last level of
decomposition [2].
Figure1: Block diagram of SC-FDMA System using DWT.
A. Quadrature amplitude modulation (QAM)
Quadrature amplitude modulation (QAM) is both an
analog and a digital modulation scheme. It conveys two
analog message signals, or two digital bit streams, by
changing (modulating) the amplitudes of two carrier
waves, using the amplitude-shift keying (ASK) digital
modulation scheme or amplitude modulation (AM) analog
modulation scheme. A 16-bit QAM is designed and it
comprises of serial-to-parallel conversion and mapping.
The two carrier waves, usually sinusoids, are out of phase
with each other by 90° and are thus called quadrature
carrier. QAM is a form of modulation which is widely used
for modulating data signals onto a carrier. It is widely used
because it offers advantages over other forms of data
modulation .QAM is a signal in which two carriers shifted
in phase by 90 degrees are modulated and the resultant
output consists of both amplitude and phase variations. In
view of the fact that both amplitude and phase variations
are present it may also be considered as a mixture of
amplitude and phase modulation.
Figure.2: Single-level wavelet decomposition and reconstruction [2]
C Subcarrier Mapping:
A. Discrete Wavelet Transform(DWT)
Wavelet analysis is simply the process of decomposing
a signal into shifted and scaled versions of a particular
wavelet. Wavelet filters have finite length and due to this
property, wavelet filter banks can perform local analysis.
An important property of wavelet analysis is perfect
reconstruction, which is the process of rebuilding a
ISSN: 2231-5381
Figure 3: Subcarrier allocation method for multiple users (3 users, 12
subcarriers and 4 subcarriers allocated per user [1].
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International Journal of Engineering Trends and Technology (IJETT)-Volume 4 Issue 7-July 2013
There are two methods to choose the subcarriers for
transmission: distributed subcarrier mapping and localized
subcarrier mapping as shown in Figure 3.
In the distributed subcarrier mapping mode, DFT
outputs of the input data are allocated over the entire
bandwidth with zeros occupying the unused subcarriers.
Consecutive sub-carriers are occupied by the DFT outputs
of the input data in the localized subcarrier mapping mode
resulting in a continuous spectrum that occupies a fraction
of the total available band width. The localized subcarrier
mapping mode of SC-FDMA is referred as localized
FDMA (LFDMA) and distributed subcarrier mapping
mode of SC-FDMA as distributed FDMA (DFDMA).
each symbol are padded with zeros on both the sides. Then
DWT is performed and mapped using the sub-carrier
mapping. Further IDWT is performed on the mapping
output, lastly cyclic prefixed and transmitted. Figure 6
shows the RTL schematic of the transmitter.
Figure 4 shows an example of SC-FDMA transmit symbols
in frequency domain for N=4 subcarriers per user, Q=3
users and M= 12 subcarriers in the system. After subcarrier
mapping, the frequency data is transformed back to the
time domain by applying M-point inverse DFT (IDFT) [1].
Figure.5: Result of the transmitter
Figure 4: An example of SC-FDMA transmits symbols in frequency
domain.
III SIMULATION RESULTS AND ANALYSIS.
A.TRANSMITTER
Figure 5 shows the simulation result of
the transmitter. The input signal is modulated using the
QAM modulation technique. For the modulated signal the
symbols are generated by the symbol generator and then
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Figure.6: RTL schematic of the transmitter
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International Journal of Engineering Trends and Technology (IJETT)-Volume 4 Issue 7-July 2013
B .RECEIVER
IV HARDWARE RESOURCE UTILIZATION
Figure 7 shows the simulation result of
the receiver. The received input is inverse cyclic prefixed.
Further DWT is performed. The resulting data is demapped
then IDWT is performed. The original signal is obtained by
demapping. Figure 8 shows the RTL schematic of the
receiver.
Table I shows the RAM resource utilization both the
transmitter and the receiver
Table 1
Mapping
type
No.
of
Slic
es
Use
d
out
of
547
2
No.
of 4
inpu
t
LUT
s out
of
109
44
No.
of
slice
Flip
flop
s out
of
109
44
Maxim
um
Maxim
um
Frequen
cy
Power
Transmit
ter
95
82
120
188
198
Receiver
560
593
727
188
178
(mw)
(MHz)
Figure.7: Result of the receiver.
V
CONCLUSION
The Single Carrier Frequency Division Multiple
Access (SC-FDMA) is an attractive technology for uplink
broadband wireless communications, because it does not
have the problems such as the large Peak-to-Average
Power Ratio (PAPR) that is more significant in Orthogonal
Frequency Division Multiple Access (OFDMA).An
effective transceiver scheme for the SC-FDMA system
using Discrete Wavelet Transform has been presented. The
modulation and DWT technique is analyzed. The simulated
code is physically dumped on the FPGA and tested using
the chip scope pro.
REFERENCES
[1] Moray Rumney, “3GPP LTE: Introducing Single-Carrier FDMA”,
January 2008.
Figure.8: RTL schematic of the receiver
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International Journal of Engineering Trends and Technology (IJETT)-Volume 4 Issue 7-July 2013
[2] M. A. Abd El-Hamed1, M. I. Dessouky2, F. Shawki2, Mohammad K.
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