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by edfgtrfgh
6197 days ago
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The over the air part of SMS can be zero cost. The SMS message is in a spare 128byte segment of a standard phone-base status message (it can send a new packet specificaly to transmit the SMS but it doesn't have to if you don't mind a few mins latency). If the receiver is on the same base station -like kids texting each other across the classroom it doesn't use any of the phone companies network bandwidth. It takes more bandwidth to send a message back to HQ to
bill for the text message than it does to transmit the SMS. |
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