in OMCR, you define which TRX will be set in inner zone, and which will serve the outer zone.
One TRX can’t serve the two zones.
In case of multiband cells, the inner is one band (usually DCS1800) and the outer zone is another band (GSM900)
The distinction is based on the UL and DL RXLEV, not the distance. There is also a condition about the load, optionally.
If RXLEV UL AND DL > threshold + Hyst –> TCH is allocated in inner, or if there is already an ongoing call there is a HO outer > inner (cause 13).
If RXLEV UL OR DL < threshold --> TCH allocated in outer zone, or there is HO from inner to outer (cause 10 for low UL, cause 11 for low DL).