load or for the reason that the local sensors only out-
put the track information. The distributed track-to-
track fusion approach focus on fusing the local sensor
tracks with the global tracks at the fusion center. The
performance of this approach is usually worse com-
pared to centralized fusion method. However, the dis-
tributed track-to-track fusion approach requires only
a fraction of the computation time needed for the cen-
tralized fusion since the number of local tracks trans-
mitted to the fusion center is much less compared to
the number of local sensor measurements (Musicki
et al., 2015; Lee et al., 2014).
In this paper, both track-to-track fusion and cen-
tralized fusion are considered under the multiple de-
tection situation. The MD-LM-IPDA is implemented
in these two fusion structures. The probability of tar-
get existence is used as the track quality measure for
local tracks and global tracks and only the confirmed
local sensor tracks are sent to the fusion center for
track-to-track fusion. In both these two fusion struc-
tures, the fusion center generates global tracks and
uses local sensor output, tracks for track-to-track fu-
sion and measurements for centralized fusion, to up-
date global track states and probabilities of target ex-
istence.
In the track-to-track fusion structure, local sen-
sors use the original measurements to update the local
track states and the confirmed tracks (both true tracks
or false tracks) are transmitted to the fusion center.
Then, these confirmed tracks come form the local sen-
sors assume the role of measurements to update the
global track states at the fusion center. The probabil-
ity of target existence of the local tracks are used in
calculating the fusion probabilities. The fusion pro-
cess improves both FTD and tracking accuracy com-
pared to local sensor performance.
In the centralized fusion structure, all local sen-
sors send the measurements to the fusion center and
the global tracks are updated using these measure-
ments. Usually the measurements used by the global
tracks in centralized fusion is different from that of
the distributed fusion. This different is due to that
in the distributed fusion structure, each local sensor
processes the tracking algorithm to generate tracks
and confirmed local tracks are considered as measure-
ments at the fusion center. Usually the centralized fu-
sion obtains better performances than distributed fu-
sion but plagued by the high communication burden.
Section 2 depicts the target and measurement
models. Section 3 demonstrates the centralized fu-
sion structure. The distributed fusion process is given
in Section 4. In Section 5, the performances of the
two fusion structures are compared followed by the
conclusion in Section 6.
2 PROBLEM STATEMENT
The dynamic state for target τ propagates according
to a constant velocity model, given by
x
τ
k+1
= Fx
τ
k
+ v
k
(1)
where x
τ
k
stands for the target state at scan k, F is the
state propagation matrix. v
k
is the zero-mean Gaus-
sian process noise with covariance Q.
The target measurement detected by sensor “s” is
generated by
z
s
k
= H
s
x
τ
k
+ w
s
k
(2)
where H
s
is the measurement matrix and w
s
k
is the
zero-mean Gaussian measurement noise with covari-
ance R
s
. The process noise and measurement noise
are assumed independent. Since the multiple detec-
tion problem is considered, each target can generate
more than one measurements.
The clutter measurement follows the Pois-
son/uniform distribution which means that the num-
ber of clutter measurements at each scan followsPois-
son distribution and the spatial distribution of a clutter
measurement follows the uniform distribution in the
surveillance area.
Let Z
s
k
stand for the measurements obtained by
sensor “s” and z
s
k, j
is the j-th measurement of Z
s
k
. The
measurements gathered by sensor “s” from initial to
scan k is denoted by
Z
k,s
= {Z
s
1
,Z
s
2
,.. . ,Z
s
k
} (3)
so that all the measurement obtained by all the sensors
from initial to current scan k is given as
Z
k
=
n
Z
k,1
,Z
k,2
,.. . ,Z
k,L
o
(4)
where L is the number of sensors.
The probability of target existence event χ
k
and
not exist event
¯
χ
τ
k
satisfies
P
χ
τ
k
|Z
k
+ P
¯
χ
τ
k
|Z
k
= 1 (5)
For reasons of clarity, here we define that
ˆ
ψ
τ
k
= P
χ
τ
k
|Z
k,s
;
¯
ψ
τ
k
= P
χ
τ
k
|Z
k−1,s
(6)
and the prediction relation between these two param-
eters is given by
¯
ψ
τ
k
= p
11
ˆ
ψ
τ
k−1
(7)
where p
11
is the propagation probability that a target
exists at scan k− 1 and keeps existence at scan k.