What Is SMS?

Date First Published: 13th May 2022

Topic: Computer Networking

Subtopic: Internet Protocols

Computer Terms & Definitions

Difficulty Level: 3/10

Learn more about what SMS is in this article.

SMS stands for Short Message Service and it is one of the oldest technologies used for exchanging short text messages of up to 140 bytes, which is equal to 160 characters between phones through a mobile phone network that was defined in the 1985 GSM (Global System for Mobile) standard. SMS has become very popular. By the end of 2010, it was believed that there were 3.5 billion SMS users.

Note:

SMS can be used for more than sending text messages over a mobile phone network. Other services, such as news and weather can be sent to user’s phones.

How Does SMS Work?

All sent messages are received by an SMSC (Short Message Service Centre). This is the part of the mobile phone network that handles SMS functions, such as sending, storing, receiving, and routing. It then sends it to the correct mobile device. An SMS request is sent to the HLC (home location register), which is a database that contains subscriber data for a mobile phone network. It sends this request for the purpose of finding the roaming user. Then, once the request has been received by HLR, it will respond to the SMSC with the status of the user. It can return with three statuses:

• Inactive
• Active
• Roaming

Inactive SMS Messages

In order for the text message to be successfully sent, SMS does not require the recipient’s phone to be on. When an SMS message is sent, but the recipient’s phone is turned off, the SMS service will hold onto the message until the recipient turns on their phone. Verification for sent messages is performed by SMSC and once the recipient has successfully received the message, it will categorise the message as ‘sent’ and it will not attempt to resend the message.

Does SMS Require An Internet Connection?

SMS does not require an internet connection, since it connects to a mobile phone network and uses a cellular signal. This is useful for sending messages when no internet connection is available. However, most mobile phone providers put a limit on the number of text messages that can be sent per month. Exceeding this limit can result in extra charges by the mobile phone provider. In addition, the use of data roaming (using the provider’s mobile phone network when outside of their coverage area) can result in huge charges, especially when sending images. Most providers will automatically send a text message when outside of their coverage area that informs the user of how much it costs to send a text message.

History

In the early 1980s, the addition of text messaging functionality to mobile phones began. In December 1982, the first action plan of the CEPT Group GSM was approved. Their request was that ‘The services and facilities offered in the public switched telephone networks should be available in the mobile system’. In 1984, the SMS concept was developed by the Franco-German GSM cooperation by Friedhelm Hillebrand and Bernard Ghillebaert.

The first SMS message was sent on 3rd December 1992 when Neil Papworth, a test engineer that worked at the Sema Group used a PC to send a message containing ‘Merry Christmas’ to their colleague, Richard Javis.