Date of Original Version
The upper L-Band will be the only frequency band with two different GPS civil signals available to users at the same carrier frequency with the legacy L1 C/Afcode signal and the new L1C signal. The null-to-null 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 efficient, techniques are proposed and their performance evaluated by comparing the detection probabilities at a fixed false alarm rate.
Seals, Kelly C. et al. "Using both GPS L1 C/A and L1C: strategies to improve acquisition sensitivity," Proc. ION GNSS+ 2013, Nashville TN, Sept. 2013.