Terms and definitions in messaging

Multichannel messaging service is based on a variety of telecommunication and Internet technologies. In the description of services, we often use abbreviations that may not always be known to you. Here we have compiled a glossary of terms and definitions used in the industry.

Home Location Register (HLR)

The ‘Home Location Register’ or HLR is a central database containing details of each mobile phone subscriber authorized to use the GSM core network.

Each mobile network has one HLR, although there may be many HLR servers creating a single virtual HLR. More precisely, the HLR stores details of every SIM card issued by the mobile phone operator. Each SIM has a unique identifier called an IMSI which is one of the primary keys to each HLR record.

An HLR also stores the following data about a mobile subscriber:

  • Current servicing MSC
  • Status of the subscriber
  • Temporary handset error code if applicable
    • Status – Valid/Invalid
    • If the subscriber is available to receive SMS
    • If there is an error code preventing SMS delivery
    • If the number has been ported to another mobile network