## 6 Results  
Based on the validity of the model, we now apply this model to show some insights into the typical behaviour of self-interference in BDS B1-I signals. Firstly, we try to find when the equivalent noise introduced by the self-interference approaches its maximum value. The SSC predicted from Equation (23) is illustrated in Figures 10 and 11. Here the differential time delay between the desired and undesired signals is an integer multiple of spreading code periods. Since the SSC values for \(K>10\) is equal to SSC values with \(20-K\), only cases with \(K\leq 10\) are shown here. To facilitate viewing, the results are shown separately when \(K\) is odd or even. From Figures 10 and 11 we can conclude that when the differential Doppler between desired and undesired signals is bounded by 50 Hz, self-interference will introduce the most serious noise into receiver processing chain. Secondly, in order to analyze the self-interference effects in current BDS configuration, a simulation case is setup. The orbit propagation, receiver acquisition and tracking are performed by the Spinet SimGEN simulator software suite. SimGEN is capable of full and versatile case generation. Users are allowed to control multiple GNSS and regional satellite constellations including BDS, signal  
Figure 11: SSC\({}_{\text{B1-I}}\) variation as a function of differential Doppler (between desired and undesired signals) and differential time delay. \(K\) is odd. Figure 10: SSC\({}_{\text{B1-I}}\) variation as a function of differential Doppler (between desired and undesired signals) and differential time delay. \(K\) is even. propagation, multipath and obstruction effects, antenna patterns, vehicle trajectory and various error models, thus vastly facilitating our simulation. For the current simulation, three inputs are needed from SimGEN, namely true range, received power, and carrier Doppler shift. However, due to the version of SimGEN, it is not able to simulate BDS constellation. The problem is bypassed by using Two Line Element (TLE) file retrieved from NORAD [23] and feeding it to the Motion control panel for GPS in SimGEN. The simulation length is 20 minutes, starting from UTCG1927, 26 April 2015, with a measurement rate of 1 Pulse Per Second (PPS). The receiver is placed in Shanghai, China. The result is shown in Figure 12. The constellation information is shown in Appendix C.  
As illustrated in Figure 12, we can obtain such observations:  
1. Within most of the simulation interval, the individual equivalent noise and aggregate noise is below \(-215\) dBW\(/\)Hz, which is much lower than a typical receiver noise floor of about \(-201.5\) dBW\(/\)Hz, and therefore would not cause much trouble for most applications. Here trouble means worsening of such receiver capabilities as acquisition sensitivity and tracking jitter. 2. During 200 and 240 s, the equivalent noise of PRN 8 and the aggregate noise reaches \(-200\) dBW\(/\)Hz. For a typical value of receiver noise floor (\(-201.5\) dBW\(/\)Hz), this noise floor will be transferred to \(-197.67\) dBW\(/\)Hz. In this case, PRN 6's effective carrier to noise density ratio \((C_{s}/N_{0})_{\mathit{eff}}\) is 3.83 dB lower than the original carrier to noise density ratio, should the self-interference caused by PRN 8 be absent. This could pose a serious problem to high-sensitivity processing during acquisition, tracking or navigation bit modulation. The potential hazard caused by this \((C/N_{0})_{\mathit{eff}}\) decrease could be best exemplified by Figure 13, which shows the code tracking standard deviation versus \((C_{s}/N_{0})_{\mathit{eff}}\), using established analytical method by [PERSON] and [PERSON] [19]. The B1-I receiver used in Figure 13 is assumed to have a precorrelation bandwidth of 4 MHz, a sampling frequency of 16 MHz, and 2-bit quantization. The coherent integration interval is 20 ms and a Dot Product discriminator is used.