Mobile Phone Technology

Each mobile network operator must maintain a list of equipment that can and cannot connect to their network. This ensures the network's integrity. The Equipment Identity Register (EIR) forms part of the network's core. It maintains a list of devices that have attempted to connect to a mobile phone network. Each device attempting to connect to the network has a unique IMEI (International Mobile Equipment Identity), a number allocated by the manufacturer. This is used to authenticate (or not) a device when it tries to connect.

The register maintains three lists:
• White List: The first time a valid piece of equipment tries to connect to a mobile network, it is added to the white list. All future connections will check that the device is on this list.
• Black List: The black list contains barred equipment, such as stolen devices or devices that have had a negative effect on the network when connected, i.e. they do not conform to network standards.
• Grey List: The grey list contains equipment that is classed as non-conforming. These devices are not barred, but do not conform in some way.

In 4G/5G networks, the EIR runs as a service-based architecture through a third party, allowing data to be shared between UK operators. When a device attempts to connect to a network, the mobile network uses the API for this service to allow or deny the connection. Phones that are stolen and then sold on within the UK will have their IMEI number added to the blacklist and will not be permitted to connect to any UK mobile network. Information is shared between 'friendly' countries to prevent the trafficking of stolen phones across borders.

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