Using Both GPS L1 C/A and L1C: Strategies to Improve Acquisition Sensitivity

The upper L-Band will be the only frequency band with two dierent GPS civil signals available to users at the same carrier frequency with the legacy L1 C/A code signal and the new L1C signal. The null-tonull bandwidth of the C/A code signal is 2.046 MHz. The TMBOC modulation of the L1C signal creates bandwidth of 4.092 MHz between the outer nulls of the largest spectral lobes in the split-spectrum signal. Without the need to have two separate radio-frequency chains in the front-end of a GPS receiver, using the GPS C/A and L1C signals will improve acquisition sensitivity with limited additional complexity. This paper explores various techniques for joint acquisition of GPS L1C and L1 C/A code signals. First, the nominal received power of these two signals is discussed along with the power split parameters required for optimal combining. Next, a model for the composite C/A code and L1C signal is presented. The optimal detector for joint acquisition is then derived and simulation results provided. Finally, sub-optimal, but more ecient, techniques are proposed and their performance evaluated by comparing the detection probabilities at a xed false alarm rate.

[1]  Kenneth W. Hudnut,et al.  GPS L1C: Enhanced Performance, Receiver Design Suggestions, and Key Contributions , 2010 .

[2]  Chris Hegarty,et al.  Acquisition of the GPS L5 Signal Using Coherent Combining of I5 and Q5 , 2004 .

[3]  William R. Michalson,et al.  Analysis of L1C Acquisition by Combining Pilot and Data Components over Multiple Code Periods , 2013 .

[4]  Joseph J. Rushanan,et al.  The Spreading and Overlay Codes for the L1C Signal , 2007 .

[5]  Kenneth W. Hudnut,et al.  Description of the L1C signal , 2006 .

[6]  John W. Betz,et al.  Binary Offset Carrier Modulations for Radionavigation , 2001 .

[7]  Mark G. Petovello,et al.  Combined Acquisition and Tracking Methods for GPS L1 C/A and L1C Signals , 2010 .

[8]  Philip G. Mattos.  Acquisition of the Galileo OAS L1b/c signal for the mass-market receiver , 2005 .

[9]  P.G. Mattos,et al.  Galileo L1c - Acquisition Complexity: Cross Correlation Benefits, Sensitivity Discussions on the Choice of Pure Pilot, Secondary Code, or Something Different , 2006, 2006 IEEE/ION Position, Location, And Navigation Symposium.

[10]  William R. Michalson,et al.  Analysis of Coherent Combining for GPS L1C Acquisition , 2012 .

[11]  C. J. Hegarty,et al.  Optimal and Near-optimal Detectors for Acquisition of the GPS L5 Signal , 2006 .

[12]  John G. Proakis,et al.  Digital Communications , 1983 .

[13]  D. Borio,et al.  Coherent, Noncoherent, and Differentially Coherent Combining Techniques for Acquisition of New Composite GNSS Signals , 2009, IEEE Transactions on Aerospace and Electronic Systems.