(2nd in the series “Superpowers and Science Fiction: How Mobile Devices Can Change the World“)
Text messages sent via SMS can reach their destination even when a cell network is too overloaded for phone calls to work. This knowledge can make the difference between life and death.
When Haiti was struck by a devastating earthquake in January 2010, buildings collapsed and trapped people in the rubble. Some had mobile phones, but were unable to call for help. Cell phone towers had power, thanks to diesel generators at the tower sites, but the phone network was overwhelmed by the number of people trying to make phone calls. Yet people were still able to send text messages, even posting to Twitter via SMS, pleading for help to free them from the rubble.
How is that possible?
Text messages are very short. SMS stands for “Short Message Service” – each message is limited to 160 characters. Compared to the amount of data sent for a voice call, this is practically nothing. Furthermore, SMS messages are sent on the same control channel that a phone uses to stay in touch with the nearest cell tower. The phone and cell tower frequently exchange packets of data to determine when the phone has moved to another cell tower’s area. Unlike a phone call, text messages do not need to be received at exactly the same time they are sent, and the receiver doesn’t even need to be in a coverage area when the message is sent. SMS uses a “store and forward” protocol that allows message delivery to be delayed until the receiver comes back into coverage. This provides an additional layer of reliability to ensure that messages reach their destination.
Almost every mobile phone has the ability to send text messages, but the same can’t be said for phone owners. If there are people in your life who have never sent a text message, encourage them to figure it out. Take the time to help them if necessary. Be the first person to exchange messages with them. It could save their lives. At the very least, it could give them peace of mind to verify that you are safe in the event of an earthquake, wildfire, or other disaster.