Per Stax’s blog, USSD has been around for 24-years and has mostly been used by telcos to facilitate communication with their customers. For example, telcos have a USSD code that usually starts with * and ends with # to check airtime balance or buy data.
According to the Global System for Mobile Communications Association (GSMA), nine in 10 mobile money transactions in sub-Saharan Africa are done through USSD.
Interestingly, the technology is the product of the GSM 02.90 document created by engineers at the European Telecommunications Standards Institute (ETSI), a body formed by the European Union in 1988 to harmonise and standardise communication technology in Europe.
According to a 2018 Quartz Africa article, the document had a protocol designed to facilitate communication between telcos and their subscribers. However, telcos needed a protocol and initiated machine-to-machine communication where the subscriber’s mobile phone would simply query the network and get a response instantly.
Over the years, USSD has gone from aiding network and subscriber communication to being used for several other applications, including banking. Interestingly, the USSD protocol has not had any major upgrade since its introduction.