Sorry Paul, I’m a bit rusty with the UL PC formula.
Here is the formula:
PCH = min(GAMMA0 – GAMMA_Tnx – ALPHA*(C+48),Pmax)
• GAMMA0 = 39 dBm if the BCCH carrier is in the GSM850 or GSM900 frequency band, and or
36 dBm if the BCCH carrier is in the DCS1800 or DCS1900 frequency band,
• GAMMA_Tnx is an uplink power control parameter sent in RLC control messages,
• ALPHA is the alpha power control parameter,
• C is the normalised received signal level at the MS. It is the mean of the received signal level
plus the power reduction Pb used by the BTS on PBCCH blocks relatively to the output power
used on BCCH,
• Pmax is the maximum transmitted power, and is equal to GPRS_MS_TXPWR_MAX_CCH if
there is a PBCCH, or to MS_TXPWR_MAX_CCH otherwise.
Conslusion : to disable UL PC GPRS : ALPHA and GAMMA should be 0 ! So that PCH = GAMMA0.
Sorry for my mistake.