when a HO is failed, then the MS will try to revert to the old cell (= the serving cell), where it will simply use its previous TCH. That TCH wasn’t release yet : the BSC will only release the old TCH when the MS susccesfully seized the new TCH.
So the reversion is not a problem : it is a happy ending of a HO failure.
To reduce the number of reversions, 2 solutions :
– try to make terrible HO failures, where reversion is not possible and the call drops in agony. (joking…)
– reduce the number of HO failures due to bad radio conditions. In other words, improve your cells overlap (less interference, better coverage, more pro-active parameter settings)