no, TFO will not have any effect on RXQUAL, it will “only” improve the voice quality.
RXQUAL is the rate of errors on the radio link, nothing else. The only way to improve this RXQUAL is to reduce interference. The codecs, the TFO, the AMR, etc, should not have an effect on RXQUAL. On the other hand, frequency hopping, power control, dtx, vamos, frequency planning, frequency load, antenna, combiner, bts sensitivity, etc, have an effect on RXQUAL (= all “physical” features)
FR and HR should suffer both from the same RXQUAL. But FR will decode the signal into “speech frame” when rxqual is poor more succesfully than half-rate.
I don’t know why you are seeing rxqual on HR better than rxqual on FR. Probably a statistical effect ? Perhaps HR calls are established on BCCH frequencies more often ? I have no good explanation… 🙂
IMO, you should focus on:
– worst cells
– PC & HO thresholds
Sorry, i’m not very helpful, but your problem is “vast” and very specific to your network…