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mate deteriorates for the fusion schemes. In this case the DKF-GP and DKF-RE
perform the best as they are designed to operate at arbitrary communications rates.
The CKF however, which is optimal under full communication, performs worse
due to the fact that the fusion equations (24) and (25) for a central T2TF assumes
that all sensors had a successful transmission of parameters at this time step. This
can further be seen as the probability of successful transmission is reduced to 30%,
which is shown in Figure 5 (c). When the communication is most severely constrained,
to 10% in Figure 5 (d), it can be seen that although DKF-GP and DKF-RE
still perform the best, there is no longer a significant improvement over just using
a single Kalman filter. This confirms what may be intuitive, that information fusion
cannot be achieved when communication is severely constrained.
It can be seen in Figures 5 (a) – (d) that DKF-GP and DKF-RE have equivalent
performance, and so the DKF-RE is suitable as an approximation to DKF-GP, but
with lower computation. However, this equivalence in performance will not hold
when the sensor exhibits geometry dependent measurement characteristics which
is not considered in these simulations.
VI. Conclusions and future work
In this paper, an overview of state-of-the-art algorithms for object tracking
in communication constrained scenarios is given. For the challenge of delayed
measurements, which arises because of unsynchronized sensors or varying communication
delays, the Accumulated State Density (ASD) filter gives the optimal
solution with respect to the mean squared error. If communication links offer
only small bandwidths, local tracking should be performed. If multiple sensors
send their preprocessed tracks to a fusion node, the problem of track-to-track
fusion (T2TF) arises due to cross-correlations between the local tracks. Through
simulation it has been shown that when communication is constrained, distributed,
decorrelated tracking outperforms a central Kalman filter, which is optimal under
full communication.
References
[1] Y. Bar-Shalom, X. Li, and T. Kirubarajan, Estimation with Applications to Tracking
and Navigation. Wiley-Interscience, 2001.
[2] W. Koch, F. Govaers, “On Accumulated State Densities with Applications to Out-of-
-Sequence Measurement Processing,” IEEE Transactions on Aerospace and Electronic
Systems, vol. 47, no. 4, pp. 2766-2778, October 2011.
[3] W. Koch, J. Koller, and M. Ulmke, “Ground target tracking and road map extraction,”
ISPRS Journal of Photogrammetry and Remote Sensing, vol. 61, no. 3-4, pp. 197-208,
2006, theme Issue: Airborne and Spaceborne Traffic Monitoring. [Online]. Available: