1
Preamble Optimization Based on Frequency
Domain Averaging for Channel Estimation
in OQAM-OFDM Systems
Dejin Kong
∗
, Da Chen
∗
, Daiming Qu
∗†
, and Tao Jiang
∗
∗
Wuhan National Laboratory for Optoelectronics, School of Electronics Information and Communications,
Huazhong University of Science and Technology, Wuhan, China.
†
National Mobile Communications Research Laboratory.
E-mail: kdjin@hust.edu.cn, chenda@hust.edu.cn, qudaiming@hust.edu.cn, tao.jiang@ieee.org
Abstract—In this paper, a frequency domain averaging (FDA)
method is presented to improve channel estimation in offset
quadrature amplitude modulation based orthogonal frequency-
division multiplexing (OQAM-OFDM) systems. Considering that
existing preamble structures are not optimal for the FDA method,
a preamble optimization scheme based on the FDA method is also
presented to further improve the channel estimation. Due to that
the optimization problem is non-convex, we employ the genetic
algorithm (GA) to obtain an approximate optimal preamble.
Numerical simulations have been done and simulation results
show that the channel estimation performance is effectively
improved with the optimized preamble.
Index Terms—OQAM-OFDM, channel estimation, frequency
domain averaging, genetic algorithm.
I. INTRODUCTION
As an alternative scheme to conventional orthogonal
frequency division multiplexing (OFDM) systems, offset
quadrature amplitude modulation based orthogonal frequency-
division multiplexing (OQAM-OFDM) systems have draw a
lot of attention [1]–[7]. Due to the use of the pulse shaping
filter on each subcarrier, OQAM-OFDM systems have low-
er spectral sidelobes than OFDM systems [8]. In addition,
compared to OFDM systems, OQAM-OFDM systems do not
require the insertion of cyclic prefix [9], resulting in higher
spectral efficiency. As a result, the OQAM-OFDM scheme
have been viewed as a promising physical layer technique
[10]–[13].
In practical, the channel estimation plays a significant role
on the performances of wireless communication systems.
However, in OQAM-OFDM systems, the orthogonality condi-
tion always holds in the field of real numbers [2], resulting in
the problem of the intrinsic imaginary interference that does
Copyright (c) 2015 IEEE. Personal use of this material is permitted.
However, permission to use this material for any other purposes must be
obtained from the IEEE by sending a request to p ubs-permissions@ieee.org.
This work was supported in part by the National High Technology
Development 863 Program of China under Grants 2015AA01A710 and
2014AA01A704, the National Science Foundation for Distinguished Young
Scholars of China with Grant numbers 61325004, and 61501193, and the
Key Program Research Plan of National Natural Science Foundation of
Hubei in China with Grant 2013CFA055, the National Science Foundation
of China under Grant 61571200, the open research fund of National Mobile
Communications Research Laboratory, Southeast University under Grant
2014D09.
not exist in the conventional OFDM systems [2], [11] . As
a result, the present channel estimation methods proposed for
OFDM can not be used for OQAM-OFDM systems directly.
So far, some channel estimation schemes for OQAM-
OFDM systems have been proposed, which can be mainly
divided into two categories, i.e., . the scattered-based channel
estimation methods [14]–[17] and the preamble-based channel
estimation schemes [18]–[26]. In general, the scattered-based
channel estimation schemes have smaller pilot overhead while
the preamble-based channel estimation methods can obtain
better system performance. In the following, we focus on
the preamble-based channel estimation schemes in OQAM-
OFDM systems mainly. As the well-known one of preamble-
based channel estimation schemes, interference approximation
method (IAM) [18] has draw much attention due to the
simplicity and efficiency. In this paper, we aim to improve
the performance of IAM method by exploiting the frequency
domain averaging (FDA) technique. FDA has been employed
in OFDM systems to improve the channel estimation [27].
However, due to the fact that in OQAM-OFDM systems,
the orthogonality condition always holds in the field of real
numbers, the noises on adjacent subcarriers at the receiver are
correlated [3], resulting in that the FDA for OFDM systems
is not suitable for OQAM-OFDM systems.
In this paper, a frequency domain averaging (FDA) method
based on maximum likelihood criterion is proposed to improve
channel estimation in OQAM-OFDM systems. It is found
that existing preamble structures are not optimal for the FDA
method, and a preamble optimization scheme based on the
FDA method is also presented to further improve the channel
estimation. Due to the fact that the preamble optimization
problem is non-convex, the genetic algorithm (GA) can be em-
ployed to obtain an approximate optimal preamble. Numerical
simulations have been done and simulation results show that
the channel estimation performance is effectively improved
with the optimized preamble.
The rest of the paper is organized as follows. In Section
II, the OQAM-OFDM system model is presented. Then, the
preamble optimization scheme based on the FDA method
is presented in Section III. Section IV shows performance
analysis of the proposed channel estimation scheme. In Section
V, extensive simulations are conducted and analyzed, followed
978-1-4673-7687-7/15/$31.00 ©2015 IEEE