Uimid

UIMID

A UIMID (user identity module identifier) is a 32-bit Electronic Serial Number (ESN) stored in a R-UIM or CSIM ('smart card') used for TDMA or CDMA2000 phones (mainly the latter). It is given a different name to avoid confusion with the hardware ESN stored in the phone. In all known systems the UIMID displaces the ESN in signaling (based on setting bit 1 of the 'UsgInd' field to '1' in the card). Because the UIMID is allocated from the same numbering space as ESN its existence is transparent to the network. The reason the UIMID is transmitted instead of the ESN is because the card contains the MIN or IMSI and devices such as the HLR running the ANSI-41 mobility management protocol insist on a static association between these identifiers for subscription validation. The HLR will store the MIN or IMSI alongside the ESN in each record, and if an ANSI-41 message is received containing a different pair it will be rejected as invalid.