A Novel Frequency Domain Equalization Algorithm for SC-FDE System
lijun Sun
College of Electrical Engineering
Henan University of Technology
Zhengzhou, China
E-mail: sunlijunzz@163.com
Xiangli Wang,Shouyong Zhang
College of Information Science and Technology
Henan University of Technology
Zhengzhou, China
E-mail: xiangli0706@gmail.com
Abstract—Single carrier frequency domain equalization
technology is an important component of physical layer
technology for broadband wireless access system , which can
effectively avoid the lack of great complexity for single-carrier
time domain equalization, as well as the high PAPR for
orthogonal frequency division multiplexing In this paper, the
MMSE decision feedback frequency domain equalization
(MMSE-DFE) algorithm and the LMS frequency domain
adaptive equalization algorithm are researched comparably.
On this basis, a new LMS decision feedback frequency domain
adaptive equalization (LMS-DFE) algorithm using non-linear
structure is proposed. The computer Simulation results show
that the proposed algorithm can effectively update the
equalizer tap coefficients by tracking the channel changes, and
then lower BER are obtained.
Keywords-single carrier frequency domain equalization
(SC-FDE), minimum mean-square-error decision feedback
equalization (MMSE-DFE), LMS criterion, adaptive equalization
I. INTRODUCTION
At the same time of achieving high-speed, high-capacity
telecommunications transmission, the way to effectively
fight against channel frequency selective fading caused by
inter-symbol interference (ISI) is always a focus in wireless
communications.
Currently the time-domain equalization technology is
adopted to overcome the ISI in mobile communication
systems. But with the increasing of transfer rate, the
complexity of time-domain equalizer is growing rapidly. So
that the single carrier time domain equalization technique
(SC-TDE) can not meet the needs of next-generation mobile
communications and it will be replaced by orthogonal
frequency division multiplexing (OFDM), which can
effectively fight against multipath interference and
frequency selective fading. It also easily combines with
many technologies such as space-time coding, diversity,
interference suppression, and smart antennas and so on,
which has been received extensive attention.
However, OFDM technology itself also has its
disadvantages, such as relatively larger PAPR, and
sensitivity to the carrier frequency offset and phase noise. In
1994, Sari Karam and Jean Claude proposed a single
carrier frequency domain equalization (SC-FDE)
technology [2].This technology has almost identical with
the OFDM technical performance, and effectively
integrated the advantages of traditional single carrier and
OFDM technology, overcame the shortcoming of OFDM.
II. SYSTEM
MODEL
As shows in Figure 1, each data block consists of
N− symbols, and we append
cyclic prefix before
them, hence there are N symbols which will be transmitted
across each transmit antennas. As can be seen, it is an
OFDM system, but in this system IFFT operation is not
needed. In order to mitigate the multiparty impact, the
length of UW should be less than channel impulse response.
In mathematics description, there were the following
two hypotheses:
• Ideal to send and receive simultaneously, all the
frequency offset and timing errors are estimated
accurately.
• Fading is slow enough so that channel can be
regarded as constant in a symbol interval.
Figure1. Principle diagram of SC-FDE system
2009 Pacific-Asia Conference on Knowledge Engineering and Software Engineering
978-0-7695-3916-4/09 $26.00 © 2009 IEEE
DOI 10.1109/KESE.2009.42
132
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