Digital Signal Processing 62 (2017) 168–175
Contents lists available at ScienceDirect
Digital Signal Processing
www.elsevier.com/locate/dsp
A robust correntropy based subspace tracking algorithm in impulsive
noise environments
Jin-feng Zhang
a,b
, Tian-shuang Qiu
b,∗
a
Shenzhen Key Laboratory of Antennas and Propagation, Shenzhen University, Shenzhen, 518060, China
b
Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian 116024, China
a r t i c l e i n f o a b s t r a c t
Article history:
Available
online 8 December 2016
Keywords:
Impulsive
noise
Maximum
correntropy criterion
Projection
approximation subspace tracking
Variable
forgetting factor
The maximum correntropy criterion (MCC) demonstrates the inherent robustness to outliers in adaptive
filtering. By employing the MCC based cost function in projection approximation subspace tracking (PAST)
algorithm, the MCC-PAST algorithm is deduced and utilized for the subspace tracking under impulsive
noise environments. To handle the fast varying subspaces circumstances, the variable forgetting factor
(VFF) technique is developed and incorporated into the MCC-PAST algorithm. To assess the robustness
of the proposed MCC-PAST with VFF algorithm, SαS processes are employed to comprehensively model
different scenarios of impulsive noises. The simulation results show the proposed MCC-PAST algorithm
with VFF performs better than the other two PAST algorithms developed for subspace tracking in
impulsive noise environments, namely, the robust PAST algorithm and the robust Kalman filter based
algorithm with variable number of measurements (KFVNM), especially when the noise is extremely
impulsive or the GSNR (generalized signal to noise ratio) is relatively low.
© 2016 Elsevier Inc. All rights reserved.
1. Introduction
As an important branch of subspace-based methods, subspace
tracking, which aims to derive a selected subset of eigenvectors of
a Hermitian matrix, has been developed as a valuable tool in array
signal processing in the few past decades [1–3]. One very efficient
subspace tracking algorithm is the project approximation subspace
tracking (PAST) approach [3]. By employing the recursive least-
squares
(RLS) techniques, the PAST algorithm recursively estimates
the signal subspace by minimizing the least square errors between
the observation and a “projection approximation” obtained from
previously estimated subspace.
Unfortunately,
the conventional PAST method has two distinct
shortcomings. First, the RLS technique is vulnerable to impulsive
noise in nature. In fact, in some scenarios, sudden bursts or spikes,
which are either man-made or occurred naturally, are exhibited at
the array outputs. In such cases, the performance of the PAST al-
gorithm
will be degraded substantially. The second defect of the
conventional PAST algorithms is also traced back to the RLS tech-
nique.
That is, the RLS algorithm with a constant forgetting factor
(FF) is not suitable for tracking fast varying subspaces. In fact, both
*
Corresponding author.
E-mail
address: qiutsh@dlut.edu.c (T.-s. Qiu).
of the drawbacks of the conventional PAST algorithm have been
studied. In [4], Chan derived a robust subspace tracking method
by incorporating the M-estimate technique in robust statistics into
PAST algorithm to suppress the adverse effects of the impulsive
noise. As for the limitation of the tracking capability, in [5], an ex-
tension
of the Kalman filter-based algorithm with variable number
of measurements (KFVNM) is developed to handle the tracking of
the fast varying subspaces. That is, when the subspace substan-
tially
varies, a small number of measurements is employed in the
algorithm so that the estimation bias introduced by remote and
unrelated measurements will be small. On the other hand, if the
subspace is slowly varying, a large number of measurements is
used to reduce the estimation variance. In addition, to deal with
the impulsive noise, the M-estimation technique in robust statis-
tics
is also incorporated into the KFVNM algorithm. The superior
performance of the robust KFVNM algorithm for tracking fast vary-
ing
subspaces in impulsive noise environments has been showed
by the simulation results [5].
However,
as we noticed, the robust KFVNM algorithm suffers
from two limitations. First, the computation complexity may in-
crease
considerably since a relative large number of the past mea-
surements
need to be utilized for the estimation of the signal
subspace when the signal subspace varies slowly at the tth time
instant. Second, in the robust KFVNM algorithm, when one impulse
is detected at the tth time instant, the corresponding measurement
http://dx.doi.org/10.1016/j.dsp.2016.11.011
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© 2016 Elsevier Inc. All rights reserved.