# Method for Estimating the Optimal Coefficient of L1C/B1C Signal Correlator Joint Receiving
## 1 Introduction  
The growing demand for location, navigation and positioning services is boosting the development of high-utilization ratio signals, which have been developed by a new generation of global navigation satellite system (GNSS). Compared with traditional navigation signals, pilot channels appear in modernized navigation signals, such as GPS-L2C, GPS-L5C, Galileo satellite navigation system (Galileo)-E1, Galileo-E5, Galileo-E6 OS, BDS3 -B2, Global Navigation Satellite System (GLONASS)-G3 OC signal [1; 2; 3]. The navigation message is loaded on the data channel, and the pilot channel is only loaded with thespreading code. Such a signal structure not only improves the receiving performance, but also promotes improvements in the receiving method. Following this trend, many works have emerged on research and development toward the reception of GNSS signals with pilots; the typical algorithms currently include pilot-assisted data and the joint reception of pilots and data. To maximize the positioning accuracy of navigation signals, high-precision user receivers consider the advantages of data and pilot components for positioning. The pilot component with a better tracking performance and higher power is used for ranging, and then the loop tracking result is used to assist the data component in calculating the navigation message information. This algorithm has low complexity but fails to make full use of the design performance of the Multiplexed Binary Offset Carrier (MBOC) signal [4; 5]. Therefore, some scholars combine data and pilot components to achieve the best positioning performance. For example, there are non-coherent combination algorithms, differential combination algorithms and coherent combination algorithms for the joint acquisition of data/pilot [6; 7; 8; 9; 10]. There are also many scholars who have studied the joint tracking method of data/pilot. In 2005, [PERSON] proposed the joint tracking method of the future data/pilot signal carrier loop of GNSS, adopted a combination of discriminators, and provided the calculation method for the coefficients [11]. References [12; 13] studied the performance of carrier frequency combination tracking for GPS L2C. Existing methods that discriminators combine for the data and pilot are analyzed in detail. Reference [14] analyzes and proposes a new method based on the joint tracking of data and pilot instead of discriminators; the proposed method removes the navigation data of the data channel through a newly designed navigation data prediction module, and then the correlator integration results of the data and the pilot are coherently combined using an equal weight ratio. The coherent integration result contains the energy of both the data and pilot. Compared with previous methods, this method has no power consumption and does not require additional computational resources. Ref. [15] proposed a tracking method using a data and pilot combination of the GPS L5 signal after a code tracking loop discriminator and filter. [PERSON] from Tsinghua University discussed the tracking threshold and tracking accuracy of the GPS-L5 signal in correlator joint tracking, discriminator joint tracking, and filter joint tracking. The results show that the correlator joint tracking has the highest tracking accuracy for the carrier loop; the filter joint has a slightly better tracking accuracy for the code loop only when the signal-to-noise ratio is low. However, the correlator joint has the lowest complexity, since only one set of discriminators and filters are needed in the loop. Refs. [16; 17; 18] achieved a linear union at the output of the discriminator for the acquisition and tracking of GalileoE1 signals. Reference [17] coherently combines the integration results of the E1B and the E1C in a 1:1 ratio, which simplifies the receiver, and the simulation validates its outstanding performance. The above references are all studies on the data/pilot with equal power allocation.