Research Journal of Applied Sciences, Engineering and Technology 4(8): 897-901, 2012
ISSN: 2040-7467
© Maxwell Scientific Organization, 2012
Submitted: October 12, 2011 Accepted: November 25, 2011 Published: April 15, 2012
Corresponding Author: Aihua Zhang, School of Information Engineering, Zhengzhou University, Zhengzhou, 450001, China
897
Compressive Channel Estimation for OFDM Cooperation Networks
1,2
Aihua Zhang,
3
Guan Gui and
1
Shouyi Yang
1
School of Information Engineering, Zhengzhou University, Zhengzhou, 450001, China
2
School of Electronic and Information Engineering, Zhongyuan University of Technology,
ZhengZhou, 450007, China
3
Department of Electrical and Communication Engineering, Graduate School of Engineering,
Tohoku University, Sendai, 980-8579, Japan
Abstract: In this study, we study compressive channel estimation for Orthogonal Frequency Division
Multiplexing (OFDM) modulated Amplify-and-Forward (AF) relay networks. Based upon the mathematical
channel model of P2P and sparseness measure function, by using Monte-Carlo runs, we show that the OFDM
cooperation convoluted channels also exhibit sparsity. In this study, we propose two compressive channel
estimation methods to exploit the inherent sparse structure in multipath fading channels of OFDM cooperation
networks with Amplify-and-Forward (AF) relays, Simulation results demonstrate that the proposed compressive
channel estimation methods provide significant improvement in mean square error (MSE) performance
compared with the conventional channel estimation methods.
Key words: Amplify-and-Forward (AF), cooperation networks, Compressive Sensing (CS), multipath fading
channel, Orthogonal Frequency Division Multiplexing (OFDM)
INTRODUCTION
Cooperative relaying has been researched intensively
for wireless networks in recent years due to its capability
of enhancing the transmission capacity and providing the
spatial diversity for single-antenna wireless transceivers
by employing the relay nodes as virtual antennas
(Laneman and Wornell, 2003; Gao et al., 2008). Multiple-
input multiple-output (MIMO) system is a well-known
technique which can boost the capacity and diversity of
wireless communications (Foschini et al., 1999).
However, it is difficult to equip multiple antennas at
mobile terminals because of cost and size limits. In order
to reckon with this problem, relay-based cooperation
communication networks have been proposed recently. It
is expected that relay protocols will be a very promising
method for future high data-rate radio communication
systems.
In cooperative communication system, terminals can
be usually divided into three parts: source, relay, and
destination, source and destination can be the base station
and mobile station, respectively, or vice versa, and the
relay receives signal from source and retransmits to
destination. Generally, there are two kinds of protocols in
cooperation networks: the Amplify-and-Forward (AF)
scheme and Decode-and-Forward (DF) scheme. In the AF
relaying, the relay amplifies and retransmits its received
noisy signal without decoding it. In the DF relaying, the
relay terminals demodulate and modulate again the
received signals and then forward them to the destination
(Laneman et al., 2004). Compared with the DF scheme,
the AF scheme is more effective since the cooperative
terminals do not need to decode their received signals.
Therefore, we focus our attention on the AF relay scheme
in this study.
Many relay studies focused on flat-fading channels,
where single-carrier systems are of interest (Seyfi et al.,
2010; Gao et al., 2008). However, the use of relays in
frequency-selective broadband channels is important as
well. It is well known that the popular solution against
frequency-selective fading is OFDM. So, cooperative
OFDM relay networks are increasingly important.
Recently, several OFDM channel estimation methods for
modulating cooperation communication have been
proposed (Gao et al., 2011; Zhang et al., 2009; Chan
et al., 2007) and these OFDM channel estimation methods
using AF protocol are based on the assumption that the
wireless channels between the terminals and the relay
nodes have rich multipath (Cotter and Rao et al., 2002).
However, recent channel measurements have demonstrate
that the wireless channels tend to exhibit a sparse or
cluster-sparse structure (Adachi et al., 2009) in delay-
spread domain. In order to take advantage of OFDM
cooperation channel sparsity, two novel compressive
channel estimation schemes are proposed in this study.
Simulation results validate the effectiveness of the
proposed methods.