A Tucker-2 Model Based Channel Estimation Technique in
AF MIMO Relay Systems
Chentao Wang; Jianhe Du; Qiaoqian Hu; Yijun Wu
Communication University of China
School of Information and Engineering, Communication University of China, Beijing 100024
E-Mail: dujianhe1@gmail.com
ABSTRACT
For multiple-input multiple-output (MIMO) relay systems, we
present a Tucker-2 model based scheme for channel estimation.
The channel training sequences at the source node are transmitted
to the relay node for three-way space-time coding. Then the
received signals at the destination node are formulated as a
Tucker-2 model, and the source-relay and relay-destination
channel matrixes can be estimated by alternating least squares
(ALS) algorithm to fit this mode. At the same time, the feasibility
of the proposed approach is analyzed in detail. The proposed
scheme can preferably estimate the source-relay and relay-
destination channel matrixes. Moreover, the estimation accuracies
of source-relay and relay-destination channel are not interacted.
Simulation results indicate the effectiveness of the proposed
scheme.
Keywords
Tucker-2 model; channel estimation; relay; ALS algorithm
1. INTRODUCTION
Due to its broader coverage, higher transmission rates and
reliability in wireless channels, relay node has recently been
regarded as a promising technique [1]. In another aspect, MIMO
systems in improving transmission rates and reliability have
widely applied to research and practice. When we associate the
concept of relaying systems with that of MIMO technology [2],
the system’s performance can be further improved by exploiting
the spatial dimension. To maximize the received signal-to-noise
ratio (SNR) or some other performance parameters, we present
several designs for the optimal relay amplifying factors [3-4]. In
any case, the advantages of a MIMO relay network can be
obtained by providing accurate channel state information (CSI)
for all links.
Relay strategies are classified into amplify-and-forward (AF) and
decode-and-forward (DF) schemes. In AF scheme, the received
signals at the relay nodes are linearly transformed, by using
simple AF processing operations, then transmit amplified signals
to the destination nodes. When relay nodes have a limited
capability of signal processing, AF scheme can reduce costs of
operation compared with DF schemes. As in the AF scheme, the
reliability of signal detection deeply relays on the accuracy of CSI
available at the receiver node. Some research works assume the
perfect CSI knowledge at the destination node for convenience.
Other channel estimation schemes are dedicated to the estimation
of the source - relay - destination (compound) channel, while it is
well-known that the CSI estimation of both source to relay and
relay to destination channels is necessary to optimize the whole
communication system.
From the wireless signal processing point of view, combining two
or more domains is one of the most common technologies. Some
algebraic models of matrix manipulation can be used at
transmitter node and/or receiver node. This technology grows
quickly because it can preserve the multidimensional nature of the
symbol data and the symbol data statistics through using of the
multilinear algebra. Compared with conventional matrix-based
technologies, the practical motivation for Multi-way signal
processing technology of communication systems comes from the
fact that it can simultaneously benefit from more than two forms
of diversity to perform channel estimation and signals separation
under model identifiability with more relaxed conditions.
New wireless communication systems based on Multi-way signal
processing technology have been studied over the past ten years
[5-6]. The tensor algebra or multilinear favors the appropriate
integration of Multi-way signal processing to those domains
whose processing strategies use the presence of redundancy of
information symbol in unsupervised and/or blind (or semi-blind)
signal estimation systems. Multi-way signal processing
technology, relying on signal special structure in code-spatial-
temporal dimension and uniqueness of decomposition, is capable
of completing signal detection and channel estimation with none
or a small amount of CSI and coding matrix through fitting multi-
way matrix model. Researches have shown that, multi-way signal
processing technology, applying to MIMO system, can further
improve communication systems’ spectral efficiency and
reliability [7-11].
There are several papers on the joint signal and channel estimation.
Sidiropoulos [7] exploited Khatri-Rao space-time codes and
proposed a joint receiver based on Parallel Factor (PARAFAC)
model. Using time-varying linear constellation precoding, De [8]
proposed a semi-blind receiver. On the basis of [7-8], De [9]
designed a semi-blind receiver, relying on space-time-frequency
codes. Du [10] proposed a semi-blind receiver in MIMO relaying
system for joint information symbols, source-relay channel and
relay-destination channel matrixes. On the basis of [10] and relay
encoding, Ximenes [11] proposed a nested PARAFAC model
based joint receiver. Above methods referring to PARAFAC
model are capable of achieving joint signal and channel
estimation effectively, but demand that data stream is equal to the
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ICCIS 2017, November 7-9, 2017, Wuhan, China
© 2017 Association for Computing Machinery.
ACM ISBN 978-1-4503-5348-9/17/11…$15.00
DOI: https://doi.org/10.1145/ 3158233.3159330