AOA and TDOA Sensor Comparison
Sep 9, 2014
Using our models to assess the errors for an angle-of-arrival (AOA) system and a time-difference of arrival (TDOA) system we created this view to dynamically display the two systems against a mobile emitter.
To compare the two systems, a notional signal-to-noise ratio and processing time is defined for the TDOA system and a notional variance for AOA system. The AOA system uses the scenario along with the same sensor arrangement shown in LOB Error Method Comparison based on [Zamora].The TDOA implementation follows [Hu] and creates two sensor pairs using S1 as the central reference with the other two sensors.
The accuracy for each pair is found using [Stein]:
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Where
- β = rms radian frequency of the received signal
- B = noise bandwidth at the receivers
- T = processing time
- γ = effective signal-to-noise ratio (SNR) (a function of range)
A rectangular spectrum is assumed so the RMS radian frequency,
 |
Where Bs is the signal bandwidth.
As in LOB Error Method Comparison the diagram on the top left shows an emitter and its track as it passes by the three-sensor network. When the emitter is in line-of-sight of the sensor the LOB and range circle are displayed. If a fix can be computed, its error ellipse is shown. The ellipses are also shown in the zoomed perspective display on the top right.
The bottom plot shows the relative sizes of the Area of Uncertainty (AOU), in nm2 for the two systems over the track of the emitter.
The range of the TDOA system is more constrained then the AOA system as it needs all three sensors to be in line-of-sight of the emitter to produce a fix. Geometry is more of a consideration with the TDOA system with this minimal number of sensors. This result is consistent with [Kaune], which shows a significant decrease in accuracy outside the bounds of the sensor network and at positions in line with the sensor pairs.
References
Pages-Zamora, A., Vidal, J, and Brooks, d., "Closed-form solution for positioning based on angle of arrivel measurements," Personal, Indoor and Mobile radio Communications, 2002. The 13th IEEE International Symposium on, Vol. 4, Sept 2002, pp. 1522-1526 vol.4.
Hu, X. and Fowler, M., "Sensor Selection for Multiple Sensor Emitter Location Systems,"Aerospace Conference, 2008 IEEE,, March 2008, pp. 1-10.
Stein, S., "Algorithms for ambiguity function processing,"Acoustics, Speech and Signal Processing, IEEE Transactions on, Vol. 29, No. 3, Jun 1981, pp. 588-599.
Kaune, R., Horst, J., and Koch, W., "Accuracy analysis for TDOA localization in sensor networks," Information Fusion (FUSION), 2011 Proceedings of the 14th International Conference on Jul 2011, pp. 1-8.