Abstract:
Orthogonal Frequency Division Multiplexing (OFDM) has gained enormous
popularity in the recent years due to its inherent ability to counter multipath effects
and support high data rates. Its implementation has been made simpler through the
efficient calculation of Discrete Fourier Transform (DFT) via the Fast Fourier
Transform (FFT) algorithm. However, timing and frequency synchronization issues in
OFDM affect its performance severely. Carrier Frequency Offset (CFO) in particular
presents a huge problem as a minor offset disturbs the orthogonality of the carriers. In
addition, it suffers from high Peak to Average Power ratio (PAPR) at the transmitter
and requires the transmitter to operate with a large linear range.
To alleviate these problems, a Single Carrier with Frequency Domain Equalization
(SC-FDE) is considered which gives performance comparable to OFDM. CFO does
not pose that big a problem in SC-FDE. Various frequency domain equalizers have
been implemented which include Linear Equalizer, Decision Feedback Equalizer
(DFE) and Iterative Block DFE. Inorder to avoid the error propagation phenomenon
of the DFEs and to increase the robustness of the Equalizer, we propose the use of a
training sequence to optimize the feedforward and feedback filter coefficients. The
new technique Data Aided Decision Feedback Equalizer (DAB-DFE), assumes that
the transmission takes place within the duration of coherence time and hence, the
channel remains constant for the subsequent blocks in the frame. A number of
different channels are considered for performance evaluation. The results confirm that
DAB-DFE outperforms the contemporary equalizers.
