A Robust Signal Selective TDOA Estimation
Algorithm for Cyclostationary Signals Source
Location
Yang Liu
Dalian University of Technology, Dalian, 116024, China
Inner Mongolia University, Huhhot, 010021, China
Email: yangliuimu@gmail.com
TianShuang Qiu
Dalian University of Technology, Dalian, 116024, China
Email: qiutsh@dlut.edu.cn
Abstract—For the problem of estimation time-difference-of-
arrival (TDOA) for cyclostationary signals in the presence
of interference and impulsive noise, a new robust multi-
cycle signal-selective algorithm is introduced. By fusing
second-order cyclic moments and fractional lower-order
statistics, a novel cyclic fractional lower-order statistics is
developed. The proposed algorithm combines the benefits of
cyclostationarity based method and fractional lower-order
statistics based estimator, by exploiting cyclostationarity
property of signals with cyclic fractional lower-order
statistics. Simulation results indicate that the new method is
highly tolerant to interference and impulsive noise and gives
higher estimation accuracy than conventional TDOA
estimation methods.
Index Terms—cyclostationarity, impulsive noise, fractional
lower-order statistics, time-difference-of-arrival (TDOA)
I. INTRODUCTION
The problem of locating a Mobile Station (MS) has
drawn considerable interest in recent years. A variety of
wireless location schemes have been extensively
investigated in [1], [2]. One typical method used to
estimate the mobile location is time-difference-of-arrival
(TDOA) which does not require knowledge of the
transmit time of the received signal from the transmitter
and has better accuracy than angle of arrival (AOA) [3],
[4]. Although several techniques are used to reduce the
effects of interference and noise in communication
systems [3], it is necessary to develop effective TDOA
algorithms.
Most man-made signals encountered in radar, sonar,
and communication systems are appropriately modeled as
cyclostationary time series [5]. A class of signal-selective
TDOA methods for passive location is introduced by
Gardner et al. [6], [7]. These methods that exploit
inherent cyclostationarity of signals are highly tolerant to
both interference and Gaussian noise, which are neither
cyclostationary signals, nor exhibiting the same cycle
frequency of the source signal. Since almost man-made
signals in communication systems have more than one
cycle frequency [5], some modified multi-cycle
algorithms which exploit more than one cycle frequency
are developed in [8-10]. The multi-cycle methods can
achieve better performance than single-cycle estimators
which utilize only one cycle frequency [10].
The primary single-cycle and multi-cycle methods
focus on the case where the environment noise is
assumed to follow the Gaussian distribution model.
However, many types of noises encountered in practice
such as atmospheric noise, multiuser interference and
some man-made noise in urban region are heavy tailed
non-Gaussian impulsive processes [11], [12]. Studies and
experimental measurements have shown that alpha-stable
distribution is more suitable for modeling noise of
impulsive nature than Gaussian distribution in
communication, telemetry, radar, and sonar systems [13],
[14]. The alpha-stable model is of a statistical-physical
nature, arising under very general assumptions satisfies
the stability and the Generalized Center Limit Theorem
[16], [17]. It can be described conveniently by four
parameters, in which the characteristic exponent
(0 2)
αα
<≤ determines the heaviness of its tail. A
small positive value of
α
indicates severe impulsiveness,
while a value of
α
close to 2 indicates a more Gaussian
type behavior. When
2
α
= , the stable distribution
reduced to the Gaussian distribution. So the alpha-stable
model is more suitable for modeling noise than Gaussian
distribution in real signal processing applications. Several
TDOA methods take account the impulsive noise using
fractional lower order statistics (FLOS) have been
proposed in literature [15].
As stable distribution does not have finite second-order
moments (except for
2
α
= ), conventional signal-
selective methods based on the second-order
cyclostationarity will be considerably weakened in
symmetric alpha-stable (
SS
α
) noise environments.
Although the fractional lower-order statistics (FLOS)
based methods are robust to both Gaussian and non-
JOURNAL OF COMPUTERS, VOL. 7, NO. 2, FEBRUARY 2012
doi:10.4304/jcp.7.2.393-398