OtoU & UtoO HO Received Level Thresholds

Dears,

What's the meaning of both parameters as I'm confused about it
OtoU HO Received Level Threshold
UtoO HO Received Level Threshold

Dears,
Could you help please
what to do to puch traffic from OverLaid to Underlaid using above mentioned parameter??

you can by these two parameters control levels in underlaid and overlaid layers for example GSM(underlaid) and DCS(overlaid)
to push traffic to GSM (underlaid)
* Set OtoU to Lower Level for example -90 dBm (20)
* Set OPTILAYER to sysopt
* Set OPTILEVTHRES wich control target layer at handover to higher levels 30 for example
If levels is lower than 30(-80dbm) it will go to underlaid

Parameter description
Preferentially assigns channels on the overlay when the uplink receivelevel on the SDCCH is no smaller thanAssign-optimum-level Threshold and the TA is smaller than TA Threshold of Assignment Pref; otherwise, assigns channels on the underlay to ensure successful channel assignment.

You can use also Traffic Load switch/Quality Switch between Overlaid and Underlaid
But just take care that if all switches are on the will work as the following
OR condition from OtoU
And conditon from UtoO