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Text messages are sent in the signaling channel, this is the channel that tells your cell phone it has a call and other stuff interesting only to telephones. Th
by jws 15y ago
Text messages are sent in the signaling channel, this is the channel that tells your cell phone it has a call and other stuff interesting only to telephones. The advantage here is your phone is always listening to that channel.
SMS is sent during idle spots in that channel, but it is a very limited channel and you couldn't run large amounts of data through it, there just isn't enough idle time.
Scarce idle time sounds oxymoronic, but it is only idle in the sense that it isn't connecting and disconnecting phone calls.
- dfox 15y agoIn many installations it was very well possible to take down entire cell by mobile terminated short message traffic, which is fact that is highly inconsistent with this "idle channel theory". The GSM signaling infrastructure is not especially suited to reordering and queuing of signaling frames. The scarce resource here is time on PCH (MT case) or RACH (MO case, which is more significant as contention there can waste resources even more), actual data transfer transaction is relatively expensive (and not-so well designed), but comparable in resource consumption to initial allocation of used SDCCH. By the way, it's interesting to note that source and destination addresses of SMS can be larger than it's payload.