Signal Processing - September 2017 - 58

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research interests include system architecture design, small satellite systems, and navigation satellite signal processing.
Craig R. Benson (c.benson@adfa.edu.au) is a senior lecturer
at the University of New South Wales, Canberra, Australia. His
research interests include guided weapons, electronic warfare,
radar, global navigation satellite systems, space debris tracking,
and small satellite missions.

0.5

References

Local Carrier Doppler (Hz)

× 104
2

250

1.5
200

150

[1] E. D. Kaplan and C. J. Hegarty, Understanding GPS: Principles and
Applications. Norwood, MA: Artech House, 2005.

80
90
100 110 120 130
Relative Code Delay (Samples)
(a)

[2] B. W. Parkinson and J. J. Spilker, Global Positioning System: Theory and
Applications, vol. 1, Plymouth, MA: AIAA, 1996.

Local Carrier Doppler (Hz)

× 104
2.5

250
200
150

50

[5] D. Akopian, "Fast FFT based GPS satellite acquisition methods," IEE Radar
Sonar Navigat., vol. 152, no. 4, pp. 277-286, 2005.

1.5

[6] D. V. Nee and A. Coenen, "New fast GPS code-acquisition technique using
FFT," Electron. Lett., vol. 27, no. 2, pp. 158-160, 1991.

0.5
5

10
15
20
Relative Code Delay (Chips)
(b)

25

FIGURE 10. The acquisition results of a real GPS L2C signal. (a) Processing
rate 128 Msps. (b) Processing rate 1.023 Msps.

in Figure 10 based on the real signal record specified in the
section "Satellite Signal Experiments." Results in Figure 10
verify that the level of correlation energy (indicated by color
bar) and its sensitivity to offset in both the Doppler and code
delay dimensions are equivalent for the processing rates of
1.023 Msps and 128 Msps. Note the higher resolution of
results in Figure 10(a) for processing at 128 Msps.

Concluding remarks
In this article, we provided an insight to the cost of signal
processing for a Doppler search in GNSS signal acquisition.
Reducing this processing cost enables users to access a GNSS
signal for real-time applications in devices with low-power
processors at an affordable cost. Considering GPS L2C signal
acquisition, a new low-rate processing technique is presented.
The signal processing concerns, in terms of correlation architecture, Doppler offset, acquisition sensitivity, and processing
complexity are explained through theoretical analysis and
experiments on real signals.

Authors
Sana U. Qaisar (s.qaisar@msn.com) received his master's and
Ph.D. degrees in 2003 and 2010 respectively, from the
University of New South Wales, Australia, where he is currently a research associate. He has also worked as a space systems
engineer in a number of communication satellite programs. His
58

[4] J. B. Y. Tsui, Fundamentals of Global Positioning System Receivers: A
Software Approach. New York: Wiley-Interscience, 2000.

2

1

100

[3] D. Borio, "A statistical theory for GNSS signal acquisition," Ph.D. Thesis,
Politecnico di Torino, Dept. Geomatic Eng., Turin, Italy, 2008.

[7] Jason Y. K. (2006, 25 Sept.). Economic benefits of the second civilian GPS signal (L2C), Civil GPS Service Interface Committee, Fort Worth, TX. [Online].
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[9] M. Tran, "Performance evaluations of the new GPS L5 and L2 Civil (L2C) signals," Navigation, vol. 51, no. 3, pp. 199-212, 2004.
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[11] S. U. Qaisar and A. G. Dempster, "Crosscorrelation performance assessment
of GPS L1 and L2 Civil codes for signal acquisition," IET Radar Sonar Navig. J.,
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[12] "Global positioning system interface specification NAVSTAR," IS GPS 200
200H, Sept. 24, 2013. [Online]. Available: www.gps.gov/technical/icwg/IS-GPS200H.pdf
[13] M. L.Psiaki, "FFT-based acquisition of GPS L2 Civilian CM and CL signals,"
in Proc. 17th Int. Tech. Meeting Satellite Division, Long Beach, CA, 2004,
pp. 646-653.
[14] C. Yang, "Joint acquisition of CM and CL codes for GPS L2 civil (L2C)
signals," in Proc. ION 61st Annu. Meeting, MA, 2005, pp. 553-562.
[15] N. I. Ziedan, "Acquisition and fine acquisition of weak GPS L2C and L5 signals
under high dynamic conditions for limited-resource applications," in Proc. ION GNSS
18th Int. Tech. Meeting Satellite Division, Long Beach, CA, 2005, pp. 1577-1588.
[16] T. H. Ta, S. U. Qaisar, A. G. Dempster, and F. Dovis, "Partial differential postcorrelation processing for GPS L2C signal acquisition," IEEE Trans. Aerospace
Electron. Syst., vol. 48, no. 2, pp. 1287-1305, 2012.
[17] A. R. Moghadda m, R. Watson, G. Lachapelle, a nd J. Nielsen,
"Exploiting the orthogonality of L2C code delays for a fast acquisition," in
Proc. ION GNSS 19th Int. Tech. Meeting Satellite Division, Fort Worth, TX,
2006, pp. 1233-1241.
[18] S. U. Qaisar and A. G. Dempster, "Assessment of the GPS L2C code structure
for efficient signal acquisition," IEEE Trans. Aerospace Electron. Syst., vol. 48, no. 3,
pp. 1889-1902, 2012.
[19] H. Li and M. Lu, "Double-chipwise correlation technique for efficient L2C
signal acquisition," IEEE Trans. Aerospace Electron. Syst., vol. 51, no. 2, pp. 1575-
1582, 2015.
[20] C.R. Benson and S. U. Qaisar, "Open-loop tracking of GNSS signals at audio
processing rates," in Proc. ION GNSS+ Int. Tech. Meeting Satellite Division,
Portland, OR, Sept. 2016, pp. 103-106.
[21] M.S. Mahmud, S. U. Qaisar, and C. Benson, "Tracking low earth orbit small
debris with GPS satellites as bistatic radar," in Proc. Advanced Maui Optical and
Space Surveillance Technologies Conf., Sept. 2016.
[22] M.S. Mahmud, S. U. Qaisar, and C. Benson, "Weak GPS signal detection in
the presence of strong signals with varying relative Doppler and long integration
gain," in Proc. IEEE/ION Position, Location and Navigation Symp., 2016,
pp. 1015-1020.
[23] E. D. Kaplan and C. J. Hegarty, Understanding GPS: Principles and
Applications. Norwood, MA: Artech House, 2006, Ch. 5, p. 219.

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