Hi Kassem, as you know in Siemens BSS Handover and Power Control algorithm are implemented in BTS instead of in BSC. So MS capabilities sent from MS to BSC (transparent to BTS) are then forwarded from BSC to BTS by an Abis message (RF MS Power Capability Indication).
If BTS doesn’t receive this message (from BSC) in a time of 20 sec from Channel Activation a Connection failure with cause T_MSRFPCI expired is generated.