hello akefa 🙂
the two main reasons for bad RXQUAL are : interference or bad coverage.
not only interference
in the two networks, the “perceived” quality for customers is the same. The RXQUAL gives an indication of the radio link quality. Keep in mind that between rxqual = 0 and 4, a typical subscriber cannot hear the difference. But a Radio Engineer can already detect a degradation from 0 to 4, and perform necessary corrective actions to prevent an impact on the voice.
On top of that, SQI belongs to Ericsson, and they only know how it is computed. Some networks uses the SQI to assess their network quality as perceived by the subscriber.
I hope that helps ? Let me know if you have comments on this, it is always great to hear different opinions on such matters.