الفهرس 
CHAPTER 1 INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 141 |  |  |
| | | from | 141 | | |
Abstract
Future wireless communications are concerned to high-quality multimedia transmission, high
spectral efficiency, and high data rate transmission. The Orthogonal Frequency Division
Multiplexing (OFDM) system can be accomplished the high data rate transmission task using
orthogonal sub-carriers. The high-quality multimedia transmission can be achieved using a
Frequency Domain Equalizer (FDE). In fact, the OFDM system offers major benefits of spectral
efficiency, good treatment to the equalization problem in frequency-domain, and good treatment to
the Inter-Symbol-Interference (ISI) problem. Unfortunately, it has Carrier Frequency Offset (CFO)
problem at the receiver side.
This thesis addresses different non-linear equalization and CFO compensation processes for
Multiple-Input-Multiple Output (MIMO)-OFDM communication system. The OFDM system
performs the modulation/demodulation aspects using different orthogonal transforms. These
transforms like Inverse Discrete Fourier Transform (IDFT)/DFT, Inverse Discrete Sine Transform
(IDST)/DST, Inverse Discrete Cosine Transform (IDCT)/DCT, and Inverse Discrete Wavelet
Transform (IDWT)/DWT. The high computational complexity of the non-linear equalization, and the
CFO problem are analyzed and mitigated using different proposed equalizers. The proposed equalizers
jointly perform the equalization and CFO compensation processes using the banded-matrix approximation
concept.
The work in this thesis can be divided into three main parts. The first part presents the main
concepts of the OFDM system. Then the CFO problem and its effect are addressed. Then, a
different estimation algorithms for CFO are presented. At the end of this part, we propose a blind
CFO estimation algorithm for OFDM system. This proposed scheme improves the Mean Square
Error (MSE) of the CFO estimation than that of the conventional estimation scheme based on
Cyclic Prefix (CP).The second part presents the main aspects of the linear, and non-linear equalization and CFO
compensation processes through the OFDM system. This is followed by a proposal of different
joint non-linear FDE and CFO compensation for MIMO-OFDM system. The proposed non-linear
equalizers are based on Fast Fourier Transform (FFT), DST, DCT, and DWT. Moreover, the proposed
non-linear equalizers take the effect of the co-channel interference, the CFO, as well as the noise.
The proposed non-linear equalizers are implemented with lower-complexity using the concept of
the banded-matrix approximation. The proposed non-linear equalizer based on FFT provides a
reduction in the simulation time of about 26.96% compared to the corresponding conventional one,
but a degradation in the Signal-to-Noise Ratio (SNR) of about 0.24 dB at Bit-Error-Rate (BER)=10-
3, and τ=10. The proposed non-linear equalizer based on DST provides a reduction in the simulation
time of about 5.91% compared to the corresponding conventional one based on DST. Also, it
provides an SNR improvement of about 4.84, 2.77 dB compared to the corresponding conventional
one based on FFT, and DST, respectively at BER=10-3, and τ=10. The proposed non-linear
equalizer based on DCT provides a reduction in the simulation time of about 12.64% compared to
the corresponding conventional one based on DCT. Also, it provides an SNR improvement of about
4.92, 2.7 dB compared to the corresponding conventional one based on FFT, and DCT, respectively
at BER=10-3, and τ=10. The proposed non-linear equalizer based on DWT provides a reduction in
the simulation time of about 22.15% compared to the corresponding conventional one based on
DWT. Also, it provides an SNR improvement of about 0.18, 1.3 dB compared to the corresponding
conventional one based on DWT, at BER=6×10-4, and 2×10-4, respectively, and τ=5.
The third part presents a proposal of three modified schemes for MIMO-OFDM system. The
1st and 2nd algorithms are based on the Binary Phase Shift Keying (BPSK) mapping, while the 3rd
algorithm is based on Quadrature Phase Shift Keying (QPSK) mapping. In fact, the 1st proposed
OFDM based BPSK can reduce the computational complexity compared to the conventional
OFDM configuration based on the banded-matrix approximation concept. The trade-off is the BER
performance compared to the conventional OFDM configuration. The 2nd proposed OFDM based
BPSK gives an SNR improvement of 7.05 dB compared to the corresponding conventional OFDM
configuration at BER=10-3. The trade-off is that the proposed scheme need an extra simulation
time, that is about 5.7% in case of τ=15, and 3.5% in case of τ=128 compared to the conventionalOFDM configuration. The proposed OFDM based QPSK gives an SNR improvement of 4.51 dB
compared to the corresponding conventional OFDM configuration at BER=10-3.