Short Message Service (SMS) allows mobile devices to exchange short text messages using standardized communication protocols. SMS was introduced in 1991 in Europe as part of the GSM standard and has since become widely used, with over 3.5 billion active users representing 80% of mobile subscribers. SMS messages are limited to 160 characters and can be used for personal messaging, information services, downloads, alerts, interactive applications, and marketing.

1. Short Message Service (SMS) :
It is a text messaging service component of phone, web, or mobile
communication systems. It uses standardizedcommunications
protocols to allow fixed line or mobile phone devices to exchange short
text messages.
Short message service (SMS) is a globally accepted wireless service.
SMS appeared on the wireless scene in 1991 in Europe.
The European standard for digital wireless, now known as the Global
System for Mobile Communications (GSM), included short messaging
services from the outset.
SMS is the most widely used data application, with an estimated 3.5
billion active users, or about 80% of all mobile phone subscribers. The
term "SMS" is used for all types of short text messaging and the user
activity itself in many parts of the world. SMS is also employed in direct
marketing, known as SMS marketing.
SMS as used on modern handsets originated from radio telegraphy in
radio memo pagers using standardized phone protocols. These were
defined in 1985 as part of the Global System for Mobile
Communications (GSM) series of standards as a means of sending
messages of up to 160 characters to and from GSM mobile
handsets. Though most SMS messages are mobile-to-mobile text
messages, support for the service has expanded to include other mobile
technologies, such as ANSI CDMA networks and Digital AMPS, as well
as satellite and landline networks.

2. SMS Communication :
Short Message Mobile Terminated (SM-MT) :
SM-MT denotes the capability of the GSM system to send a message
from the SC to a mobile phone where the message is either received, or,
if the recipient device is unavailable, stored for later delivery. A
delivery report or failure report is then sent back to the SC. These

3. messages may be input to the Service center by other mobile users (via
a mobile originated short message) or by a variety of other sources, for
example, speech, telex, or facsimile.
The classes of SM-MT :
Classes identify the importance of the message importance and the
location where it should be stored. There are four message classes.
Class 0 SMS: This message is displayed on the mobile phone
immediately and a message delivery report is sent back to the SC. The
message does not have to be saved in the mobile phone or on the SIM
card (unless selected to do so by the mobile user). This type is also
referred to as Flash SMS.
Class 1 SMS: This message is stored in the memory of the mobile
phone or the SIM card (depending on memory availability).
Class 2 SMS: This message class is Phase 2-specific and carries SIM
card data. The SIM card data must be successfully transferred prior to
sending acknowledgment to the SC. An error message is sent to the SC
if this transmission is not possible.
Class 3 SMS: This message is forwarded from the receiving entity to an
external device. The delivery acknowledgment is sent to the SC
regardless of whether or not the message was forwarded to the external
device.
Short Message Mobile Originated (SM-MO) :
SM-MO denotes the capability of the GSM system to send a message
from an M to an SME via an SC and to provide information to the
mobile phone about the delivery or failure of that message. These
messages may be destined for other mobile users, or for subscribers on
a fixed network.
Application :
Person-to-Person Text Messaging
Provision of Information

4. Downloading
Alerts and Notifications
Two-way Interactive Text Messaging Applications
SMS Marketing