MIXes in Mobile Communication Systems: Location Management with Privacy

This paper introduces a new technique for location management in cellular networks. It avoids the recording of moving tracks of mobile subscribers. The described procedures are derived from the well known untraceable MIX network and the distributed storage of location information according to GSM networks. 1 Terminology The served area of a cellular radio network is usually divided into location areas. Location areas are comprised of one or several radio cells. The mark (address) of a location area is the Location Area Identification (LAI). To address a Mobile Station (MS) in the case of an incoming call, the mobile network needs to know the current location area in order to broadcast the connection request. 1 The location management is comprised of the procedures location update and handover. The location update consists of all procedures for location management in the stand-by state of an MS, whereas the handover handles an MS moving during a call. To register the location of an MS, the network operator can maintain a Home Location Register (HLR) at a central place in the network. The HLR keeps track of the actual LAI of the MS. In the case of a (mobile terminated) call the subscriber A calls the Mobile Subscriber Integrated Services Digital Network Number (MSISDN) of the mobile subscriber B. The mobile network reads the current LAI and routes the call to the responsible Base Transceiver Station (BTS). Then the BTS broadcasts a connection request in all cells of the location area (see Fig. 1). 1 The technique " broadcast over the whole served area " is not discussed in this paper! In 3rd generation mobile networks (Universal Mobile Telecommunication System, UMTS and Future Public Land Mobile Telecommunication Network, FPLMTN) the globally covered area does not allow broadcast. However, broadcasts in some parts of the globe require location management again.