The Short Message Service (SMS), often called text messaging, is a means of sending short messages to and from mobile phones. SMS was originally defined as part of the GSM series of standards in 1985^[1] as a means of sending messages of up to 160 characters, to and from GSM mobile handsets.^[2] Since then, support for the service has expanded to include alternative mobile standards such as ANSI CDMA networks and AMPS, satellite and landline networks.^[3] Most SMS messages are mobile-to-mobile text messages, though the standard supports other types of broadcast messaging as well.

The term SMS is frequently used in a non-technical sense to refer to the text messages themselves, particularly in non-English-speaking European countries where the GSM system is well-established.

 Overview

The service makes use of a Service Centre, which acts as a store and forward centre for short messages. The Service Centre communicates with the Public Land Mobile Network (PLMN) or PSTN via Interworking and Gateway MSCs.

Subscriber originated messages are transported from a handset to a Service Centre, and may be destined for mobile users, subscribers on a fixed network, or Value-Added Service Providers (VASPs) also known as application terminated. Subscriber terminated messages are transported from the Service Centre to the destination handset, and may originate from mobile users, from fixed network subscribers, or from other sources such as VASPs also known as application originated.

The Short Message Service is supported on most digital mobile phones and some personal digital assistants with on board wireless telecommunications.^[4] Text enabled fixed-line handsets are required to receive messages in text format, however messages can be delivered to non-enabled phones using text-to-speech conversion.^[5]

 History

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. Experts from several of those communities contributed in the discussions on which should be the GSM services. Most thought of SMS as providing a means to alert the individual mobile user, for example, of a deposited voice mail, whereas others had more sophisticated applications in their minds, such as telemetry. However, few believed that SMS would be used as a means for sending text messages from one mobile user to another.

As early as February 1985, after having already been discussed in GSM subgroup WP3, chaired by J. Audestad, SMS was considered in the main GSM group as a possible service for the new digital cellular system. In GSM document "Services and Facilities to be provided in the GSM System "^[1], both mobile originated and mobile terminated short messages appear on the table of GSM teleservices.

The discussions on the GSM services were then concluded in the recommendation GSM 02.03 "TeleServices supported by a GSM PLMN".^[6] Here a rudimentary description of the three services was given:

1. Short message Mobile Terminated (SMS-MT)/ Point-to-Point,
2. Short message Mobile Originated (SMS-MO)/ Point-to-Point
3. Short message Cell Broadcast.

This was handed over to a new GSM body called IDEG (the Implementation of Data and Telematic Services Experts Group), which had its kickoff in May 1987 under the chairmanship of Friedhelm Hillebrand. The technical standard known today was largely created by IDEG (later WP4) as the two recommendations GSM 03.40 (the two point-to-point services merged together) and GSM 03.41 (cell broadcast).

The Mobile Application Part (MAP) of the SS7 protocol included support for the transport of Short Messages through the Core Network from its inception.^[7] MAP Phase 2 expanded support for SMS by introducing a separate operation code for Mobile Terminated Short Message transport^[8]. Since Phase 2, there have been no changes to the Short Message operation packages in MAP, although other operation packages have been enhanced to support CAMEL SMS control.

From 3GPP Releases 99 and 4 onwards, CAMEL Phase 3 introduced the ability for the Intelligent Network (IN) to control aspects of the Mobile Originated Short Message Service,^[9] while CAMEL Phase 4, as part of 3GPP Release 5 and onwards, provides the IN with the ability to control the Mobile Terminated service.^[10] CAMEL allows the gsmSCF to block the submission (MO) or delivery (MT) of Short Messages, route messages to destinations other than that specified by the user, and perform real-time billing for the use of the service. Prior to standardized CAMEL control of the Short Message Service, IN control relied on switch vendor specific extensions to the Intelligent Network Application Part (INAP) of SS7.

The first commercial SMS message was sent over the Vodafone GSM network in the United Kingdom on 3 December 1992, from Neil Papworth of Airwide Solutions^[11] (using a personal computer) to Richard Jarvis of Vodafone (using an Orbitel 901 handset). The text of the message was "Merry Christmas".^[12] The first SMS typed on a GSM phone is claimed to have been sent by Riku Pihkonen, an engineer student at Nokia, in 1993.^[13]

Initial growth was slow, with customers in 1995 sending on average only 0.4 messages per GSM customer per month.^[14] One factor in the slow takeup of SMS was that operators were slow to set up charging systems, especially for prepaid subscribers, and eliminate billing fraud which was possible by changing SMSC settings on individual handsets to use the SMSCs of other operators. Over time, this issue was eliminated by switch-billing instead of billing at the SMSC and by new features within SMSCs to allow blocking of foreign mobile users sending messages through it. By the end of 2000, the average number of messages per user reached 35.^[14]

It is also alleged that the fact that roaming customers, in the early days, rarely received bills for their SMSs after holidays abroad had a boost on text messaging as an alternative to voice calls.

SMS was originally designed as part of GSM, but is now available on a wide range of networks, including 3G networks. However, not all text messaging systems use SMS, and some notable alternate implementations of the concept include J-Phone's SkyMail and NTT Docomo's Short Mail, both in Japan. E-mail messaging from phones, as popularized by NTT Docomo's i-mode and the RIM BlackBerry, also typically use standard mail protocols such as SMTP over TCP/IP.

SMS derives its benefit from two absolute advantages compared to any other form of communication. SMS is the fastest form of communication if measured by actual communication throughput including instances such as the counterpart not being able to take a call, being out of radio coverage, listening to voicemail, put on hold etc. SMS at its worst is a few second slower than a direct voice call or Blackberry wireless e-mail etc, but in the best case is faster by hours or even days than any other form of communication. SMS messages tend to be read within 30 minutes where an email message tends to be read in 48 hours.

Commercially SMS is a massive industry in 2006 worth over 80 Billion dollars globally.^[15]. SMS has an average global price of 11 cents and maintains a near 90% profit margin.