What is SMS?

In today’s world, many of us use apps like WhatsApp for messaging and even voice and video calls, but SMS is still one of the most widely used services available through mobile operators. SMS stands for Short Message Service however many of us know SMS as “texts” or “text messages”. It allows us to instantly and securely communicate with other mobile users as well as computer/laptop users. Due to its superior security compliance, SMS is still used by many mobile operators for sending confidential information to their customers. Many businesses use SMS for sending their marketing messages also.

SMS stands for Short Message Service and it allows a mobile phone user to send text messages to other users. SMS is a text-only service with a limit of 160 characters (for Latin characters) including alphabets, numbers and symbols. This limit varies for other languages. The SMS service on mobile phones was introduced in the early 1990s and now it is one of the most widely used services within the mobile industry.

In a slightly technical context, when a mobile phone is not engaged in a call, it still communicates with the mobile network regularly. It means that the signalling (sending and receiving signals) continues through a communication channel called ‘control channel’. This control channel is the communication channel used for sending and receiving SMS. There is also a network entity called SMSC (Short Message Service Centre) that is responsible for storing and forwarding the SMS to the desired destination. When we send an SMS, our mobile phone communicates with the SMSC through a mobile base station closest to us. The SMSC then forwards the SMS to the destination number through the mobile base station closest to the destination mobile phone.


There is another inter-related service called MMS or Multimedia Messaging Service which is an extension of the SMS service. While SMS is all about text-only messages, MMS is a service used for sending messages that include media such as photos. Many people still use the MMS service even though, with smartphones nowadays, it is possible to send any media including photos, video, etc. to other users through any free messaging or social media apps. MMS is not always included in all mobile plans (or tariffs) so it is a good idea to check directly with your mobile service provider to avoid any unexpected charges.

As you can imagine, even with the free messaging or social media apps, you will still consume mobile data when using data through the mobile network i.e. when your mobile shows symbols like G, E, H, H+, 3G, 3G+, LTE, 4G, 4G+, etc. instead of the WiFi symbol. In order for the MMS service to work, you need an MMS capable device, which may be more of a challenge for feature phones. In all cases, when a user sends MMS to another user e.g. for sending a photo, the sender’s mobile phone establishes a data connection. The message is first sent to the MMS Centre so that the MMS Centre can check if the recipient’s mobile device is MMS capable or not. If the recipients’ device is MMS capable, the recipient receives an MMS notification message which contains a web link (URL) pointing to the MMS content. The recipient’s phone then establishes a data connection to retrieve the MMS content.

Usually, the MMS is displayed to the recipient as a photograph followed by any text from the sender just below the photograph. If the recipient’s device does not support MMS, the recipient receives a link which he/she can view in a web browser on any other device.

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