An Improved Algorithm for PAPR Reduction of OFDM Systems - Advanced Research on Computer Education, Simulation and Modeling - page 373

reduction of OFDM signal. Secondly, via LCT algorithm, the PAPR of OFDM signal is
reduced again. After two lower PAPR implementing, the PAPR of the OFDM signal
has been substantially improved. In the receiver, through the anti-compression and
expansion transform, the transmit signal is restored, and then through the auxiliary
information received, the original signal is obtained.
By means of DET time-domain circular convolution theorem, using the special
phase sequence designed, TCM only use an IFFT algorithm to achieve the PAPR re-
duction of the OFDM signal, and then can effectively reduce the system PAPR. The
different amplitudes of signals are reduced by the LCT algorithm with compression and
expansion of two inflexion points [8]. By combining the two above methods, the sys-
tem has a good balance between the PAPR reduction and BER performance. Therefore,
in this paper, the novel algorithm based on the DFT property of TCM and LCT algo-
rithms can reduce PAPR of the OFDM signal.

3 Simulation Analysis

We can use MATLAB as simulation software, for the random number generator, se-
rial-parallel switching and IFFT transform can be completed by the function of com-
plex matrix operation in the simulation system. In addition, MATLAB has powerful
graphics generation capabilities, and data processing capabilities for simulation results
of the system. The experiments prove that the proposed algorithm can reduce PAPR of
the OFDM signal effectively. Now description of details involved in the simulation are
as follows:
In this paper, the study is to reduce peak average power ratio of the OFDM signal,
and mainly on study of the novel algorithm, by combining the DFT property of the time
domain circular convolution (TCM) and the linear companding transform with two
inflexion points (LCT). Some experiments are presented. Because of the processing is
done at the transmitter, whether the PAPR of the signal is reduced is known after
OFDM modulation. We can observe the effect of various PAPR reduction methods at
the transmitter. Considering the AWGN channel the BER performance of OFDM
modulation is shown in this paper.
The signal modulation uses 4 kinds of modulation, namely BPSK, QPSK, QAM,
16QAM. There are 4 choices 64, 256, 512, and 1024 for the number of subcarriers,
respectively. The oversampling technique is used, and the oversampling factor is 4. In
the TCM algorithm, the random phase sequence P of length L can be arbitrary [9],
[ { }

] ()

.The PAPR reduction performance is evaluated by using
the complementary cumulative distribution function (CCDF) of the PAPR, which
indicates the probability that the PAPR of an OFDM sequence may exceed the
threshold level PAPR 0 .
For the focus of this paper is to reduce the signal peak average power ratio, all the
presented algorithms are based on the equivalent complex baseband OFDM signal. So
the simulations are carried out in the digital domain and the transmitter and the receiver
of the signal processing module are involved.

P = p20: 12 j π L − L