¹⁶. With the increasing miniaturization of the CDPD modems, it is unclear if removable SIM cards will ever be produced. Indeed, for the removable SIM concept to gain acceptance, manufacturers need to produce CDPD devices with the proper interfaces to accept SIM cards. One possible use for SIM card devices is in fleet operations. In this case, it may be beneficial to deploy mobile units with SIM slots into each fleet vehicle, while the drivers are assigned individual SIM cards. This way, each driver is uniquely identified by his or her network address.