Project PDA

S

MS is a very inexpensive method of communication. 160 characters take up as much room as a one-second voice call. Messages are delivered immediately (or when the phone is turned on). Like e-mail, they can also be reviewed or stored in your phone for as long as you wish. SMS messages can also be sent out to huge groups of people with the single press of a button.

SMS was originally designed as part of GSM, but is now available on a wide range of networks, including 3G networks. However, not all text messaging systems use SMS, and some notable alternate implementations of the concept include J-Phone's SkyMail and NTT Docomo's Short Mail, both in Japan. E-mail messaging from phones, as popularized by NTT Docomo's i-mode and the RIM BlackBerry, also typically use standard mail protocols such as SMTP over TCP/IP.

SMS also allows for unified messaging. This is where SMS can take on a number of different message formats (including voice mail, e-mail and fax) and allows users to access them from their mobile device. GPRS would allow the sending of Internet information through mobile devices at a high speed.

Experts believe that GPRS will be capable of delivering information at a speed of up to 100,000 bits per second.

Currently, GSM can deliver information at a speed of 9,600 bits per second. It is also alleged that the fact that roaming customers, in the early days, rarely received bills for their SMSs after holidays abroad had a boost on text messaging as an alternative to voice calls.

Short messages can also be used to send binary content such as ringtones or logos, as well as OTA programming or configuration data. Such uses are a vendor-specific extension of the GSM specification and there are multiple competing standards, although Nokia's Smart Messaging is by far the most common.

The SMS specification has defined a way for an external Terminal Equipment, such as a PC or Pocket PC, to control the SMS functions of a mobile phone. The connection between the Terminal Equipment and the mobile phone can be realized with a serial cable, a Bluetooth link, an infrared link, etc. The interface protocol is based on AT commands. Common AT commands include AT+CMGS (send message), AT+CMSS (send message from storage), AT+CMGL (list messages) and AT+CMGR (read message).

Some service providers offer the ability to send messages to land line telephones regardless of their capability of receiving text messages by automatically phoning the recipient and reading the message aloud using a speech synthesizer along with the number of the sender.

Today, SMS is also used for machine to machine communication. For instance, there is an LED display machine controlled by SMS, and some vehicle tracking companies like ESITrack use SMS for their data transport or telemetry needs.