02-07-2013, 12:38 PM
Short Message Service ( SMS )
Short Message.ppt (Size: 304.5 KB / Downloads: 19)
Definition
Short message service (SMS) is a globally accepted wireless service that enables the transmission of alphanumeric messages between mobile subscribers and external systems such as electronic mail, paging, and voice-mail systems.
Introduction
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.
In North America, SMS was made available initially on digital wireless networks built by early pioneers such as BellSouth Mobility, PrimeCo, and Nextel, among others. These digital wireless networks are based on GSM, code division multiple access (CDMA), and time division multiple access (TDMA) standards.
How it works?
Messages in Short Message Service (SMS) must be no longer than 160 alpha-numeric characters and contain no images or graphics.
Once a message is sent, it is received by a Short Message Service Center (SMSC), which must then get it to the appropriate mobile device.
To do this, the SMSC sends a SMS Request to the home location register (HLR) to find the roaming customer. Once the HLR receives the request, it will respond to the SMSC with the subscriber's status: 1) inactive or active 2) where subscriber is roaming.
If the response is "inactive", then the SMSC will hold onto the message for a period of time. When the subscriber accesses his device, the HLR sends a SMS Notification to the SMSC, and the SMSC will attempt delivery.
The SMSC transfers the message in a Short Message Delivery Point to Point format to the serving system. The system pages the device, and if it responds, the message gets delivered.
The SMSC receives verification that the message was received by the end user, then categorizes the message as "sent" and will not attempt to send again.
The number of mobile-phone users expects to reach 500 million worldwide by 2003, and with the help of SMS, 75 percent of all cellular phones will be Internet-enabled.
External Short Messaging Entities
An ESME is a device that may receive or send short messages. The short message entity (SME) may be located in the fixed network, a mobile device, or another service center.
VMS—The VMS is responsible for receiving, storing, and playing voice messages intended for a subscriber that was busy or not available to take a voice call. It is also responsible for sending voice-mail notifications for those subscribers to the SMSC.
Web—The growth of the Internet has also affected the world of SMS. Therefore, it is almost mandatory to support interconnections to the World Wide Web for the submission of messages and notifications. The increasing number of Internet users has a positive impact on the SMS traffic increment experienced in the last few years.
SMSC
SMSC is a combination of hardware and software responsible for the relaying and storing and forwarding of a short message between an SME and mobile device.
The SMSC must have high reliability, subscriber capacity, and message throughput. In addition, the system should be easily scalable to accommodate growing demand for SMS in the network.
Normally, an IN–based solution will allow for a lower entry cost compared to point solutions because it can support other applications on a single hardware platform and share resources, thereby spreading the deployment cost over several services and applications.
Another factor to be considered is the ease of operation and maintenance of the application, as well as the flexibility to activate new services and upgrade to new software releases.
MT–SM Scenario (GSM)
The short message is submitted from the ESME to the SMSC.
After completing its internal processing, the SMSC interrogates the HLR and receives the routing information for the mobile subscriber.
The SMSC sends the short message to the MSC using the forward short message operation.
The MSC retrieves the subscriber information from the VLR. This operation may include an authentication procedure.
The MSC transfers the short message to the MS.
The MSC returns to the SMSC the outcome of the forwardShortMessage operation.
If requested by the ESME, the SMSC returns a status report indicating delivery of the short message.