it’s difficult to answer, because you don’t provide any detail ! so here are some questions, to help me help you 🙂
could you please write down which indicators or which measurements are showing “degraded speech quality” ?
what do you mean by HO zone ?
what kind of hopping are you using ?
what is the intersite distance ?
what is the downtilt applied and the antenna height ?
how many TRX/cell ?
in terms of qos stats, do you notice anything ?