РАЗДЕЛ VIII SHORT MESSAGE SERVICE

The Short Message Service (SMS) is the ability to send and receive text messages to and from mobile telephones. The text can comprise words or numbers or an alphanumeric combinations. The first short message is believed to have been sent in December 1992 from a personal Computer to a mobile phone on the Vodaphone GSM network in the UK.

SMS is convenient and cost effective for a number of reasons. When you compare it with the cost of airtime for voice calls or wireless web access, SMS is a real bargain. Messages can be received while making voice calls, and there are no busy signals to contend with. Plus, if you find yourself in a situation where taking a sell phone is inappropriate, SMS is silent and discreet. Messages generated by SMS are immediately delivered directly to your phone. There is no need to call an access number, as in the case with voice mail. Also, most carriers offer SMS alerts (information packets, such as stock quotes, sports scores, and news) that can be delivered to your phone regularly scheduled intervals.

The Short Message Service has several unique features. For example, a single short message can be up to 160 characters of text in length. Those 160 characters can comprise words or numbers or their alphanumeric combinations. Non-text based short messages (for example, in binary format) are also supported. These are used for ringtones and logos services.

The short message service is a store and forward service, in other words, short messages are not sent directly from the server to recipient, but always via an SMS centre instead. Each mobile telephone network that supports SMS has one or more messaging centres to handle and manage the short messages.

The short message service features confirmation of the message delivery. This means that unlike paging, users do not simply send a short message and trust and hope that it gets delivered. Instead, the sender of the short message can receive a return message back notifying them whether the short message has been delivered or not.

Short messages can be sent and received simultaneously with GSM voice, Data and Fax calls. This is possible because whereas voice, data and fax calls take over a dedicated radio channel for the duration of the call, short messages travel over and above the radio channel using the signaling path. As such, users of SMS rarely if ever get busy signal as they can do during peak network usage times.

Ways of sending multiple short messages are available. SMS concatenation (stringing several short messages together) and SMS compression (getting more than 160 characters of information within a single short message) have been defined and incorporated in the GSM standards.

To use the short message service users need the relevant subscriptions and hardware, specifically: a subscription to a mobile telephone network that supports SMS; use of SMS must be enabled for that user (automatic access to the SMS is given by some mobile network operators, others charge a monthly subscription and require a specific option to use the service); a mobile phone that supports SMS; knowledge how to send or read a short message using their specific model of mobile phone; a destination to send a message to or to receive a message from. This is usually another mobile phone but it may be a fax machine, PC or Internet address
EXERCISE EXERCISE 2