## 6 Conclusions  
The construction of BDS-3 will be completed in an all-round way in 2020. The code bias characteristics for BDS-3 satellites contributes to knowing of the accuracy of satellite navigation signals and further realizes better application. In the paper, we characterize the satellite-induced code bias variation based on the observations of the B1I/B2b/B3I/B1C/B2a frequency bands of the fifteen BDS-3 MEO satellites collected by a 40 m dish antenna. From these validations, the following conclusions were obtained:  
1. The MP combination values of the BDS-3 satellite signals are small and concentrated in a range of about 0.1-0.2 m. The MP combination value differs from each frequency due to signal constructions. The MP combination value of the B1I and B3I frequency band has the largest and smallest RMS value, indicating the weakest and strongest anti-MP ability. In addition, the MP mitigation of the B2a and B2b frequency bands is better than that of the B1I and B1C frequency bands. 2. The satellite-induced code bias variation of BDS-3 demonstrates different performances on different frequency bands on different satellites, which was greatly reduced compared with that of the BDS-2 satellites. There is obvious elevation-dependent code bias variation for the C28 B1I/B2b/B3I/B1C/B2a frequency bands, compared with other satellites. Similarly, the MP combination of B3I has an obvious elevation-dependent variation in a range of 0.1 m for C21/C24/C27/C28/C37. The obvious elevation-dependent variation of the B2a and B2b frequency bands also exists in most satellites with a range of 0.1 m, but the MP combination values of some satellites are asymmetric with respect to elevation, which is especially obvious for the B1I and BIC frequency bands with elevation-dependent variations of 0.2 m, which indicates that the code bias variation is not uniquely related to elevation, especially for the  
Figure 9: The MP combination time series tracked by two receivers with the 40 m dish antenna and normal geodetic antenna with respect to elevation for the BDS-3 satellites C21/C27/C28/C37 for the available frequency bands. B1I/BIC frequency bands. 3. The magnitude and variation of the MP combination value of each frequency band vary with elevation but do not always increase with a decrease in elevation. The code bias variation with elevations below 30\({}^{\circ}\) is the largest and most vulnerable to the interference of MP error, which can be considered in the stochastic model of GNSS data processing. The satellite-induced code variations of two manufacturers of BDS-3 satellites have no obvious differences at elevations larger than 25\({}^{\circ}\). 4. The code bias of the B1C_data is slightly larger than that of the B1C_pilot, but the difference is small and can be neglected. What's more, the MP combination time series have similar variations in B1C_data and B1C_pilot. 5. To explore the performance of the code bias for mass users with normal geodetic antennas, the Xia1 station from iGMAS was selected. Among the frequency bands of the C21/C24/C27/C28/C37 satellites, there still exists elevation-dependent code bias in the frequency bands B1I/B1C/B3I/B2a/B2b of C21, B3I/B2a/B2b of C24 and B2b of C28 by comparing the MP combination values within the same observation arc, indicating that satellite-induced elevation-dependent code bias may also appear in different antennas or receivers. Our conclusions are based on one receiver, however, so they are also worth further verification with other receivers with different configurations. In addition, the influence of the BDS-3 satellite-induced code bias on precision positioning and ambiguity fixing is worth further study using different antennas or receivers.