Abstract:
Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation
(MCM) technique that plays a significant role in digital wireless communication. This
is due to its ability to provide a high data rate for new multimedia applications. One of
the major drawbacks of OFDM is the high peak-to-average power ratio (PAPR) which
is characteristic of signals with multiple sub-carriers. The high PAPR requires
additional back-off power to achieve linear amplification at the transmitter end which
results in inefficient power consumption. This inefficient power consumption is the
major problem in implementing OFDM in a portable device. Nevertheless, several
PAPR reduction techniques have been proposed in the past to address this problem.
However, all techniques previously used to reduce PAPR suffer due to various
deficiencies such as data rate loss, high signal distortion, increase in bandwidth, high
computational complexity, increase in transmit power and memory requirements.
Therefore, this research aimed at reducing the peak to average power in the OFDM
system by hybridizing Zadoff-Chu Transform (ZCT) precoding and Partial Transmit
Sequence (PTS) techniques. The methodology employed to reduce high PAPR in this
work is based on developing an OFDM model with Additive White Gaussian Noise
(AWGN) and implementing the hybridized PAPR reduction technique combining ZCT
precoding and PTS. The performance evaluation of the hybrid model is carried out using
the Complementary Cumulative Distribution Function (CCDF), Bit Error Rate (BER),
and Power Spectral Density (PSD). The results obtained show that each technique can
efficiently reduce PAPR with ZCT having 4.8 dB PAPR which is about 6 dB reduction
from Original OFDM PAPR while PTS with a larger number of subblocks (V = 8) has
about 6.44 dB reduction from Original OFDM with about 4.4dB PAPR. The new hybrid
technique achieved a better PAPR of 4.2 dB and better overall system performance
when compared with the individual performance of ZCT and PTS. The hybrid ZCTPTS
method has a low PSD of -58 dB/MHz using subblocks 4 at N = 64 as compared
with the original OFDM which has a PSD of -53dB/MHz. The result shows that the new
hybrid technique is efficient and the problem of high PAPR in the OFDM system that
causes power deficiency is mitigated. Finally, the technique can be adopted as a PAPR
reduction method in mobile communication as mobile communication requires a low
PAPR technique with low computational complexity.
