Learn how SMS works for text messages and how it moves through cell towers, aggregators, and wireless networks to reach your recipients.
When you send a letter in the mail, it flows through an intricate network of post offices, sorting facilities, and distribution centers.
Then, almost like magic, it appears in your recipient’s mailbox a few days later.
SMS messages follow a similar process, but digitized. Instead of transporting directly to your recipient’s phone, the text bounces between a series of checkpoints instantly.
Not only do those checkpoints move your text’s data from one device to the other, but they also help protect people from spam and fraudulent messages.
Let’s dive into how SMS messaging technology works for texting friends, family, and customers.
SMS, which stands for Short Message Service, is a way to send concise text messages between mobile phones.
When SMS was first introduced in 1992, mobile networks had limited capacity to transmit data, so the messages needed to be short (160 characters or fewer) to conserve network resources. Thanks to advancements in texting technology, we can now use extended SMS messages to send more than 160 characters into one text.
If you want to send even longer text messages to your customers, you can use MMS messaging, which allows up to 1,600 characters and media (like images, videos, audio, GIFs, and PDFs).
There are two ways to send SMS messages: peer-to-peer (P2P) messaging and application-to-person (A2P) messaging. Both deliver text messages to mobile devices, but they take different routes to get there.
Let’s say you want to text a friend that you’re running late for dinner. You type up the message, “Hello! Sorry, I’m running late. Be there in 10.”
Here’s how your message reaches your friend:
First, your phone converts your message into the GSM 7-bit alphabet, which breaks your text up into the tiniest bits of data that can be transmitted to a cell tower.
This includes your message and some basic information about it, like its timestamp and the recipient’s phone number.
Your phone sends the tiny message to a nearby cell tower. Once the cell tower receives your message, it sends it to a system called the Short Message Service Center (SMSC).
The SMSC checks who your friend — the recipient — is and then checks if they are in range. If they are, the message is then sent to the tower nearest to them and then, finally, their mobile phone.
Your friend’s phone then turns the messages back from the GSM 7-bit alphabet into standard English characters by using the same code, but in reverse.
If the SMSC can’t find the phone, the message will just bounce around in its system until the moment the phone reconnects, at which point it sends it immediately.
If you’re sending SMS messages from an SMS marketing platform (like SimpleTexting), your text takes a different path to get to your customers’ phones.
Use an A2P messaging provider to compose the text message you want to send. You can send the message right away or schedule it for later. Your A2P provider also monitors messages for prohibited content.
Next, your A2P messaging provider sends the message to an aggregator (also known as an SMS gateway). The aggregator acts as a middleman between the A2P provider and the wireless carriers and helps prevent spam messages from reaching the carriers’ networks.
The aggregator receives the text message from the A2P provider and forwards it to the wireless carriers that are associated with the recipients’ mobile phone numbers.
After receiving the text message from the aggregator, the wireless carriers responsible for the recipients’ phone numbers deliver the message to their respective devices. The message then appears as a regular SMS on the recipients’ phones, allowing them to read and respond to it.