Short Message Service (SMS) is a service available on most digital mobile phones (and other mobile devices, e.g. a Pocket PC, or occasionally even desktop computers) that permits the sending of short messages (also known as text messages, or more colloquially SMSes, texts or even txts) between mobile phones, other handheld devices and even landline telephones. The term text messaging and its variants are more commonly used in North America, the UK, and the Philippines, while most other countries prefer the term SMS. Text messages are often used to interact with automated systems, such as ordering products and services for mobile phones, or participating in contests.


History

As with most other services and modules of functionality of the GSM system, no individual can claim the parenthood of SMS. It might be worth while to note this, since such attempts may still be seen - also from people that never took part in the GSM work on SMS. 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 a means to alert the individual mobile user, e.g. on incoming voice mail, whereas others had more sophisticated applications in their minds, e.g. telemetry. However, few believed that SMS would be used as a means for sending text messages from one mobile user to another.

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

Initial growth was slow, with customers in 1995 sending on average only 0.4 messages per GSM customer per month. 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. An example of a company that innovate in this subject is OsinetS.A.. By the end of 2000, the average number of messages per user reached 35.

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.


Technical details

GSM recommendation 03.41 is used to send "welcome" messages to mobile phones roaming between countries. Here, T-Mobile welcomes a Proximus subscriber to the UK and BASE welcomes an Orange UK customer to Belgium.

The Short Message Service - Point to Point (SMS-PP) is defined in GSM recommendation 03.40. GSM 03.41 defines the Short Message Service - Cell Broadcast (SMS-CB) which allows messages (advertising, public information, etc.) to be broadcast to all mobile users in a specified geographical area.
Messages are sent to a Short Message Service Centre (SMSC) which provides a store-and-forward mechanism. It attempts to send messages to their recipients. If a recipient is not reachable, the SMSC queues the message for later retry. Some SMSCs also provide a "forward and forget" option where transmission is tried only once. Both Mobile Terminated (MT), for messages sent to a mobile handset, and Mobile Originating (MO), for those that are sent from the mobile handset, operations are supported. Message delivery is best effort, so there are no guarantees that a message will actually be delivered to its recipient and delay or complete loss of a message is not uncommon, particularly when sending between networks. Users may choose to request delivery reports, which can provide positive confirmation that the message has reached the intended recipient, but notifications for failed deliveries are unreliable at best.

Transmission of the short messages between SMSC and phone can be done through different protocols such as SS7 within the standard GSM MAP framework or TCP/IP within the same standard. Messages are sent with the additional MAP operation forward_short_message, whose payload length is limited by the constraints of the signalling protocol to precisely 140 bytes (140 bytes = 140 * 8 bits = 1120 bits). In practice, this translates to either 160 7-bit characters, 140 8-bit characters, or 70 16-bit characters. Characters in languages such as Arabic, Chinese, Korean, Japanese or Slavic languages (e.g. Russian) must be encoded using the 16-bit UCS-2 character encoding (see Unicode). Routing data and other metadata is additional to the payload size.

Larger content (known as long SMS or concatenated SMS) can be sent segmented over multiple messages, in which case each message will start with a user data header (UDH) containing segmentation information. Since UDH is inside the payload, the number of characters per segment is lower: 153 for 7-bit encoding, 134 for 8-bit encoding and 67 for 16-bit encoding. The receiving phone is then responsible for reassembling the message and presenting it to the user as one long message. While the standard theoretically permits up to 255 segments, 6 to 8 segment messages are the practical maximum, and long messages are billed as equivalent to multiple SMS messages.

Short messages can also be used to send binary content such as ringtones or logos, as well as OTA programming or configuration data. Such uses are a vendor-specific extension of the GSM specification and there are multiple competing standards, although Nokia's Smart Messaging is by far the most common.

The SMS specification has defined a way for an external Terminal Equipment, such as a PC or Pocket PC, to control the SMS functions of a mobile phone. The connection between the Terminal Equipment and the mobile phone can be realized with a serial cable, a Bluetooth link, an infrared link, etc. The interface protocol is based on AT commands. Common AT commands include AT+CMGS (send message), AT+CMSS (send message from storage), AT+CMGL (list messages) and AT+CMGR (read message).

Some service providers offer the ability to send messages to land line telephones regardless of their capability of receiving text messages by automatically phoning the recipient and reading the message aloud using a speech synthesizer along with the number of the sender.

Today, SMS is also used for machine to machine communication. For instance, there is a LED display machine controlled by SMS, and some vehicle tracking companies like ESITrack use SMS for their data transport or telemetry needs.


Premium content

SMS is widely used for delivering premium content such as news alerts, financial information, logos and ringtones. Such messages are also known as premium-rated short messages (PSMS). The subscribers are charged extra for receiving this premium content, and the amount is typically divided between the mobile network operator and the content provider (VASP) either through revenue share or a fixed transport fee.

Premium short messages are also increasingly being used for "real-world" services. For example, some vending machines now allow payment by sending a premium-rated short message, so that the cost of the item bought is added to the user's phone bill or subtracted from the user's prepaid credits.
A new type of 'free premium' or 'hybrid premium' content has emerged with the launch of text-service websites. These sites allow registered users to receive free text messages when items they are interested go on sale, or when new items are introduced.


Popularity

Short message services are developing very rapidly throughout the world. In 2000, just 17 billion SMS messages were sent; in 2001, the number was up to 250 billion, and by mid-2004, SMS messages were being sent at a rate of 500 billion messages per annum. At an average cost of USD 0.10 per message, this generates revenues in excess of $50 billion for mobile telephone operators and represents close to 100 text messages for every person in the world.

SMS is particularly popular in Europe, Asia (excluding Japan; see below), Australia and New Zealand. Popularity has grown to a sufficient extent that the term texting (used as a verb meaning the act of mobile phone users sending short messages back and forth) has entered the common lexicon. In China, SMS is very popular, and has brought service providers significant profit (18 billion short messages were sent in 2001). SMS is hugely popular in India, where youngsters often send lots of text messages, and the companies provide alerts, infontainment, news, cricket scores update, railway / airline booking, mobile billing as well as banking services on SMS.

SMS was an accidental success that took nearly everyone in the mobile industry by surprise. Few people predicted that this hard of use service would take off. There was hardly any promotion for or mention of SMS by network operators until after SMS started to be a success. SMS advertising went from showing business people in suits entering text messages to bright pink and yellow advertisements aimed at the youth markets that adopted SMS.

SMS was the triumph of the consumer - every generation needs a technology that it can adopt as its own to communicate with - and the text generation took up SMS. Paradoxically, it was because SMS was so very difficult to use that the young people said that they were going to overcome the man machine interface and other issues and use the service anyway. The fact that the entry barriers to learning the service were so high were an advantage because it meant that parents and teachers and other adult authority figures were unlikely, unable and unwilling to use the service.

A whole new alphabet emerged because SMS messages took a long time to enter and were quite abrupt as people attempted to say as much as possible with as few keystrokes. Abbreviations such as 'C U L8er' for 'See you later' sprung up for timesaving and coolness. The use of smileys to reduce the bruptness of the medium and to help indicate the mood of the person in a way that was difficult with just text became popular.

The introduction of prepay mobile tariffs in which people could pay for their airtime in advance and thereby control their mobile phone expenditure was the catalyst that accelerated the take up of SMS. The network operators were unable technically to bill prepay customers for the SMS they were using because the links between the prepay platform and the billing system and the SMS Centers were not in place. The network operators responded with silence- the prepay literature did not mention SMS at all even though the prepay phones supported the service. One thing that is certain is that in these days with the Internet revolution to spread information, the young people will identify loopholes like this. And they did. Suddenly, millions more SMS essages were being sent- with some individual mobile phone subscriptions accounting for thousands of SMS per month alone as they set up automated message generators. Network operators worked with their platform suppliers to try and sort this out and implement charging for SMS for prepay customers. Meanwhile SMS incubated and spread and people were using it because it cost nothing whereas carrying out the same transaction using voice clearly did cost. Eventually after a few months the network operators finally got their act together and managed to implement SMS charging for prepay users- such that they could decrement the prepay credit by the cost of an SMS message.

A mass SMS message distribution campaign was then typically sent out- such that everyone that had used SMS received a text message informing them that from a certain date, SMS would be charged for. This led to an immediate and protracted decline in SMS usage to between 25% and 40% of the pre-charging levels as people suddenly stopped using SMS or using it as much. Then something interesting happened- the volume of SMS messages started gradually increasing again and soon reached its pre-charging levels. SMS volume growth has continued its upward growth ever since, fueled by simple erson to person messaging as people told each other how they were feeling and what they were doing- information services and other operator led initiatives failed to interest the user community to any degree and never have done. Whilst it was free, SMS had become an important part of the way that young people communicated with each other in their daily life. SMS would have taken off without this prepay factor because it was already being used before that time- but it would never have taken off as quickly.

SMS continued its astonishing growth during the year 2000 in Europe, a period of time when the mobile industry was trying to dictate the deployment of WAP. Despite doing nearly nothing else of any benefit, WAP did at least increase the attention that the mobile Internet received as people tried to work out services that would appeal to the mobile phone users. Those companies that survived the WAP debacle started to realize that it was SMS and not WAP that had the addressable audience of users and the clearer business case. Advertising and other services based on SMS started to be trialed as companies realized that people who could use SMS for person to person messaging would also be able to access SMS based commercial messages. The next great success for SMS based services was ringtones. Nokia had started its smart messaging protocol that was built on binary SMS rather than the standard text SMS. Nokia had expected this technology to be used for information services and over the air service profiling and it had languished for years, until suddenly in the year 2000, it found its application- ringtones that allow users to change the way their mobile phone rang. Because the network operators were woefully inadequate and unable to offer the ringtone suppliers fair and flexible revenue sharing, the service providers started using premium rate Interactive Voice Response (IVR) voice platforms to trigger the transmission of ringtones. The ringtones market soon became a billion dollar market- and few of the network operators even offered services- this category was dominated by independent service providers who advertised in newspapers and magazines.

SMS was the triumph of the consumer- a grassroots revolution that the mobile industry had next to nothing to do with and repeatedly reacted to. This is in stark contrast to the top down technology and industry led approaches to other nonvoice services such as WAP. The industry can learn a lot from SMS as it tries to create other nonvoice services- it is no surprise that the only other nonvoice success- i-mode in Japan was also an unprecedented and nexpected success. The mobile industry would do well to realize that success for nonvoice involves setting the right environment to allow services to succeed- ensuring everyone implements the same open standards in the same ways, putting the right payment and microbilling technologies in place and recognizing that it takes a while to build a critical mass of usage. The mobile industry needs to realize that it can either delay the mobile Internet revolution by refusing to cede control to the end user and application and service development communities- or this will be taken away from it by the markets by force. Either way, the nonvoice revolution will arrive- it is not a question of whether, just when.