Sorry, I thought I said it before:
the decision is based on RXLEV(900) only.
For instance, if DL RXLEV(900) > -70dBm and UL RXLEV(900) > -80dBm, then the TCH is allocated in INNER zone.
Once the MS is in inner zone, the DL RXLEV(1800) will probably be equal to -70 – 10dB = -80dBm. The UL RXLEV(1800) will probably be = -90dBm.
Now it’s your job to fine tune the thresholds, so that the MS doesn’t enter the inner zone if the “expected” 1800 level is going to be too low.
RXLEV DL ZONE = -80dBm
RXLEV UL ZONE = -90dBm
ZONE HO HYST DL = 15dBm
ZONE HO HYST UL = 12dBm
With this parameters:
if DL RXLEV(900) > -65dBm (-80 +15) and UL RXLEV(900) > -75dBm (-90 +12 +3), then the TCH is allocated in INNER zone.
For the -75dBm in UL, the additional 3dB comes from the difference in the MS TXPWR MAX and MS TXPWR MAX INNER.
You should also set EN_LOAD_BALANCE = DISABLE, in order to load the inner zone as much as possible.
Finally, set EN_LOAD_OUTER = ENABLE, this works better with GPRS.
Ok, I gave you all settings to get a great multiband cell…