Cannot fix the integer ambiguity for zero-baseline RTK with BDS B1I measurements

[pwang0112]

Hi,

I used GNSS-SDR to process the BDS data collected by the Spirent GSS6450 signal record system. I then used RTKLib to obtain a zero-baseline RTK solution with BDS B1I measurements only. The reference station data was outputted from the survey-grade Trimble Alloy receiver. However, the integer ambiguity in the RTK solution cannot be solved.

Below are two plots showing the positioning error results and measurement residuals, respectively:

Does anyone have some insights on this?
Thanks in advance!