What is SMS – Short Message Service?

Nowadays, we frequently use apps like WhatsApp for messaging each other and even for making voice or 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 and computer/laptop users. Due to its superior security compliance, SMS is still used by many mobile operators for sending confidential information to their customers. In addition, many businesses use SMS for sending their marketing messages also.

What does SMS mean?

SMS stands for Short Message Service, and it allows a mobile phone user to send text messages to other mobile phone 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.

What is the difference between a text message and an SMS message?

A text message is a general term that means exactly what it says on the tin – a message sent in a text format from one device to another irrespective of the technology used to send the message. On the other hand, SMS – Short Message Service is a type of text message service enabled by specific parts of a mobile network to ensure a secure delivery. Sending a message from one device to another requires connectivity of some kind. For example, when you send a text message as an iMessage from one iPhone to another, the type of connectivity you use is the internet, either as WiFi or cellular data. When you send an SMS on a GSM or UMTS network, your mobile network does not use your mobile data but instead utilises an entity called SMSC – Short Message Service Centre. When you send SMS on a 4G LTE or 5G network, your SMS can be sent over the packet-switched network by using the VoLTE or Voice over WiFi capability.

How does SMS work on mobile?

When an SMS is sent over a 2G GSM or 3G UMTS network, the circuit-switched part of the network is engaged for the delivery of an SMS which is the same part of a 2G or 3G network that enables voice calls. The mobile network employs a network entity called Short Message Service Centre to store and forward text messages to the relevant destinations (i.e. relevant phone numbers). 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. A mobile network has many channels at its disposal, including control channels and traffic channels. When a mobile phone is not engaged in a call, it regularly communicates with the mobile network. It means that the signalling (sending and receiving signals) continues through a communication channel type called the ‘control channel’. This control channel is the communication channel used for sending and receiving SMS. With 4G LTE and 5G networks, the aim is to use the packet-switched part of the network for voice calls, SMS and MMS. The Voice over LTE technology allows a mobile network to send SMS and MMS, just like other media, without any dedicated circuits. This is achieved by the mobile core network that works alongside IP Multimedia Subsystem – IMS to successfully deliver all messages to the relevant destinations.

Are SMS messages free?

The SMS service utilises specific parts of a mobile network, just like voice calling or mobile data. As a result, it has an associated cost for the mobile operator. In the past, SMS was one of the key sources of revenue for the mobile operator; however, nowadays, many tariffs include very affordable rates for the delivery of SMS and MMS. As a consumer, it is much easier nowadays to live without SMS or MMS if you are comfortable making use of messaging apps that just require a WiFi or mobile data connection. That is especially useful when sending messages internationally or heavy files like recorded video messages from one phone to another. SMS is still a very useful, secure and reliable service for important messages where delivery is crucial e.g. messages from the government to people for COVID vaccinations.

What is the difference between MMS and SMS?

MMS and SMS are interrelated. MMS, short for Multimedia Messaging Service, 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. However, 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. 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 they can view in a web browser on any other device.

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. 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 to 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.

Here are some helpful downloads

Thank you for reading this post, I hope it helped you in developing a better understanding of cellular networks. But sometimes, we need some extra support especially when preparing for a new job, or studying a new topic, or maybe just buying a new phone. Whatever you are trying to do, here are some downloads that can help you:

Students & fresh graduates: If you are just starting, the complexity of the cellular industry can be a bit overwhelming. But don’t worry, I have created this FREE ebook so you can familiarise yourself with the basics like 3G, 4G etc. As a next step, check out the latest edition of the same ebook with more details on 4G & 5G networks with diagrams. You can then read Mobile Networks Made Easy which explains the network nodes e.g. BTS, MSC, GGSN etc.

Professionals: If you are an experienced professional but new to mobile communications, it may seem hard to compete with someone who has a decade of experience in the cellular industry. But not everyone who works in this industry is always up to date on the bigger picture and challenges given how quickly the industry evolves. The bigger picture comes from experience which is why I’ve carefully put together a few slides to get you started in no time. So if work in sales, marketing, product, project or any other area of business where you need a high-level view, Introduction to Mobile Communications can give you a quick start. Also, here are some templates to help you prepare your own slides on product overview and product roadmap.

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