Mobile Phone Technology

Unified Database Management

UDM with 5G

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In a mobile phone system there is a necessity to store data regarding each subscriber. In a 2G system this is the Home Location Register (HLR); in a 4G system this is the Home Subscriber System (HSS); and in 5G the data is part of the Unified Database Management system (UDM).

The UDM is the main database that holds subscriber information. The key to the data is the International Subscriber Identity which is the 'internationised' version of the SIM card number. The database contains user profiles, authentication data, location details, authentication and authorisation details.

When a client device tries to connect to the network the network connects to the UDM to retrieve the users authentication credentials and profile. This allows the network to make sure that the SIM is valid and to identify which services the client is authorised to use. This will also set up and manage the session for the SIM across the network.

In 2G there is separate Visitor Location Register, that contains details of all clients connected to a particular mobile switching centre. This is a cache of the HLR for those on their home network, plus details of others who have roamed onto the network. In 5G the home user's details are held in the AMF with the session details in the SMF part of the UDM. These functions are implemented in the cloud and accessible quickly using edge computing. For a roaming device their details are required for them to access the netwwork and details are stored in the AMF and DSMF parts of the UDM.

  • User Authentication The UDM verifies that the client device can connect to the network and allows or denies access as appropriate meaning only authorised clients can connect to a network
  • Subscriber Profile Management Storage of all user data and in particular which services the client is able to use.
  • Location Information This the location of the client device in order to enable the management of the mobility (handover) of the device and ensures the correct services are delivered
  • Authorization the process of authorisation and the 'keys' are managed in the UDM. This was initially held seperate in a 2G system but is unified in 4G / 5G