How SMS Works Just when we're finally used to seeing everybody constantly talking on their cell phones,
it suddenly seems like no one is talking at all. Instead, they're
typing away on tiny numerical pads, using their cell phones to send
quick messages. SMS, or text messaging, has replaced talking on the phone for a new "thumb generation" of texters. In
this article, we'll find out how text messaging works, explore its uses
and learn why it sometimes takes a while for your text message to get
to its recipient. What is SMS?SMS Attacks
Recently
it has been suggested that SMS messages could be used to attack a cell
phone system. The basic idea is very simple. If a large number of SMS
messages were sent by computers to phones in a small geographical area (like a city),
these messages would overwhelm the control channels and make it
impossible for the cell phone system to set up calls. Now that cell
phone providers know about the possibility of this threat, they can
design systems to throttle messages coming from the SMSC onto the
network. |
SMS stands for short
message service. Simply put, it is a method of communication that sends
text between cell phones, or from a PC or handheld to a cell phone. The "short" part refers to the maximum size of the text messages: 160 characters (letters, numbers or symbols in the Latin alphabet). For other alphabets, such as Chinese, the maximum SMS size is 70 characters. But how do SMS messages actually get to your phone? If you have read How Cell Phones Work, you can actually see what is happening. Even
if you are not talking on your cell phone, your phone is constantly
sending and receiving information. It is talking to its cell phone
tower over a pathway called a control channel. The
reason for this chatter is so that the cell phone system knows which
cell your phone is in, and so that your phone can change cells as you
move around. Every so often, your phone and the tower will exchange a
packet of data that lets both of them know that everything is OK. Your
phone also uses the control channel for call setup. When someone tries
to call you, the tower sends your phone a message over the control
channel that tells your phone to play its ring tone. The tower also
gives your phone a pair of voice channel frequencies to use for the
call. The control channel also provides the pathway for SMS
messages. When a friend sends you an SMS message, the message flows
through the SMSC, then to the tower, and the tower sends the message to
your phone as a little packet of data on the control channel. In the
same way, when you send a message, your phone sends it to the tower on
the control channel and it goes from the tower to the SMSC and from
there to its destination. | |
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