rxqual represents the BIT ERROR RATE, not the lost TCH frames.
all the combinations are possible :
good rxqual / good SQI : good situation (normal)
bad rxqual / good SQI : the bit error rate is high (radio conditions are poor), but the encoding of radio allows to rebuild a good speech frame. This is further increased with hopping = ON.
bad rxqual / bad SQI : the protection of the radio is not enough to recompose a good speech frame
good rxqual / bad SQI : several possibilities :
1. the initial speech frame was poorly encoded (problem of TRX hardware, or MS hardware)
2. the received signal is poorly decoded (same as above : hardware problem)
3. too many handovers : handovers affect the SQI (I think ? it affects QVoice) but it for sure doesn’t affect the rxqual. A handover is a blank in the voice, not taken into account at bit level, but it has an impact on the voice (no speech frames are transmitted).
4. half rate : yes, that sounds like a possible case as well. the half rate “quality” is not great, even though all bits are correctly decoded. I suppose the same will happen with AMR.
Actually, do you know how the SQI is calculated ? i think it is explained in the TEMS’s Help.