Abstract—Subband adaptive filter algorithms are able to improve
the convergence behavior by performing the pre-whitening procedure
on the input signals. In this paper, we propose a new variable step size
improved multiband-structured subband adaptive filter algorithm
which dynamically selects subband filters (VSS-DS-IMASF) in order
to reduce the computational complexity. The subbband selection
scheme which is designed to select the meaningful subbands is based
on comparing the steady state subband mean square error (SMSE) with
the subband error power throughout the algorithm execution, checking
whether the subband filters converge to the steady state. In addition,
the step size is controlled by the estimated mean square deviation
(MSD) in order to achieve better steady state performance. Simulation
results show that the proposed algorithm has lower steady state MSD
and less computational complexities compared with the existing
subband algorithms.
Keywords—
Normalized subband adaptive filter, Improved
multiband-structured adaptive subband filter, Variable step size (VSS),
Dynamic selection
I. I
NTRODUCTION
ubband adaptive filtering has been received much attention
in recent years, due to its capability of improved
convergence performance for highly correlated input signals.
For the conventional subband adaptive filters(SAFs), the
adaptive subfilter coefficients are updated independently in
each subband, and thus the convergence performance is
degraded by the band-edge and aliasing effects [1]. To
overcome this drawback, several subband structures have been
presented [2-6]. Pradhan-Peddy subband model [2] is designed
by use of the polyphase decomposition and noble identity.
Furthermore, combining the characteristics of the affine
projection (AP) algorithm [7] with Pradhan-Peddy subband
model, a subband AP (SAP) algorithm has been reported in [3],
which improves the convergence rate and reduce the
computational complexity of the AP algorithm. Lee and Gan [4]
presented a normalized subband adaptive filter (NSAF)
algorithm which made use of all the subband signals,
This work was supported in part by the National Natural Science
Foundation of China under Grant 61501119.
Chang Liu, Zhi Zhang are with School of Electronic Engineering,
Dongguan University of Technology, No.1, DaXue Avenue, Songshan Lake
district, Dongguan, 523808, People’s Republic of China (
chaneaaa@163.com,
ellon_zhang@sina.com
).
normalized by their respective subband input variance, to
update the full-band adaptive filter coefficients. Recently, to get
better convergence performance, an improved multiband struct
-ured subband adaptive filter (IMASF) algorithm has been
proposed [5-6]. It applies the most recent P input signal vectors
(projection orders) to participate in the full-band filter updating.
The IMSAF algorithm can be considered as a generalized form
of normalized least mean square (NLMS), AP and NSAF
algorithms. However, it encounters higher computational
complexity with the increased projection orders and long
unknown system.
For SAFs, the convergence rate, steady state performance and
computational complexity have been intensively investigated
for many years. It is known that the fixed step size in SAFs
reflects a tradeoff between fast convergence rate and low steady
state misadjustment. To address this problem, several variable
step size (VSS) subband algorithms have been proposed such as
set-member NSAF (SM-NSAF)[8], VSS matrix for NASF [9],
VSS-NASF [10-11], etc. The computational complexity is
another subject for SAFs, it is showed that the computational
complexity of SAF is depends on the number of subband [13].
Although the VSS subband algorithms mentioned above
achieve both better steady state performance and the faster
convergence simultaneously, their computational complexity
remains invariant throughout the convergence process.
Especially, they suffer from huge complexity for some
applications such as acoustic echo cancellation (AEC)
involving extremely long unknown system. Abadi and Husϕy
have presented the simplified selective partial-update subband
adaptive filter (SSPU-SAF) algorithm [12] with a lower
computational complexity compared with the NSAF algorithm.
The dynamic selective NSAF (DS-NSAF) presented in [13]
adopts the subband filters dynamically based on the maximum
mean square deviation (MSD) decrease principle, which retains
the convergence performance and reduce the computational
complexity. Song’s selective subband scheme [14] is derived
from the larger ratio of the squared error to an input power for
each subband. It has better convergence performance and lower
complexity. Yang [15] makes an analyses on the computational
complexity of the IMSAF algorithm and proposes several
simplified computation approaches to reduce its complexity.
These simplified variants for IMSAF acquire the decrease of the
complexity.
A variable step size improved
multiband-structured subband adaptive filter
algorithm with subband input selection
INTERNATIONAL JOURNAL OF CIRCUITS, SYSTEMS AND SIGNAL PROCESSING