SMS

Short Message Service (SMS) is a communication service standardized in the GSM mobile communication system, using standardized communications protocols allowing the interchange of short text messages between mobile telephone devices. SMS text messaging is the most widely used data application on the planet, with 2.4 billion active users, or 74% of all mobile phone subscribers sending and receiving text messages on their phones.[ The SMS technology has facilitated the development and growth of text messaging. The connection between the phenomenon of text messaging and the underlying technology is so great that in parts of the world the term "SMS" is used as a synonym for a text message or the act of sending a text message, even when a different protocol is being used.

SMS as used on modern handsets was originally defined as part of the GSM series of standards in 1985 as a means of sending messages of up to 160 characters (including spaces), to and from GSM mobile handsets Since then, support for the service has expanded to include alternative mobile standards such as ANSI CDMA networks and Digital AMPS, as well as satellite and landline networks.[] Most SMS messages are mobile-to-mobile text messages, though the standard supports other types of broadcast messaging as well.

The idea of adding text messaging to the services of mobile users was latent in many communities of mobile communication services at the beginning of the 1980s. The first action plan of the CEPT Group GSM approved in December 1982 requested "The services and facilities offered in the public switched telephone networks and public data networks ...should be available in the mobile system". This target includes the exchange of text messages either directly between mobile stations or the transmission via Message Handling Systems widely in use since the beginning of the 1980s

The innovation in SMS is indicated by the word Short in Short Message Service. The GSM system is optimized for telephony, since this was identified as its main application. The key idea for SMS was to use this telephony-optimized system and to transport messages on the signaling paths needed to control the telephony traffic during time periods when no signaling traffic existed. In this way unused resources in the system could be used to transport messages without additional cost. However, it was necessary to limit the length of the messages to 128 bytes (later improved to 140 octets, or 160 7-bit characters), so that the messages could fit into the existing signaling formats. Therefore the service was named “Short Message Service”.This concept allowed implementing the SMS in every mobile station just by an additional software routine without incremental cost per unit. Also the implementation in the networks required just software without incremental cost. The only new network element was a specialised Short Message Service Centre for a whole countrywide network. It needed capacity expansions of course with growing SMS traffic.