No one ever expected that SMS would be such a tremendous success, one that exemplifies the perfect marriage of a business model with a wireless technology. European and Asian subscribers have been using SMS for years. More than a billion SMS messages are sent each month in some countries. Finally, as of 2004, SMS began to take off in North America. SMS allows two-way transmission of 160-character alphanumeric messages between mobile subscribers and external computing systems such as e-mail systems and paging systems. Because of its increasing popularity, SMS has been extensively combined with many new types of information services in addition to traditional usage. For example, both Google and Yahoo offer Internet searching via SMS. SMS was initially designed to replace alphanumeric paging service with two-way guaranteed messaging and notification services.

Two new types of SMS components have been added to the cellular network: short message service center (SMSC) and signal transfer point (STP). An SMSC is a central controller of SMS services for the entire network. It interfaces with external message sources, such as voice-mail systems, e-mail systems, and the web. Messages sent from a mobile subscriber will also be stored and forwarded by the SMSC. An STP is a general network element connecting two separate portions of the network via SS7 signaling protocol. In the case of SMS, numerous STPs interface with the SMSC, each handling SMS transmission and delivery to and from a large number of mobile stations. No matter where the messages come from, the SMSC will guarantee delivery and inform the transmitter. For the SMSC to locate a mobile station for message delivery, it must utilize the cellular network, especially the HLR, VLR, and MSC of the mobile station.

SMS has been enhanced with new capabilities to support enhanced message service (EMS) and multimedia message service (MMS). If you consider SMS to represent very early plaintext e-mails, you might think of EMS as the fancier HTML e-mails containing pictures, animations, embedded objects such as sound clips, and formatted text. MMS is the next generation messaging service that supports rich media such as video and audio clips. The wide use of picture messages sent from a camera cell phone is merely one example of MMS in action. MMS consumes more bandwidth so it requires a high data rate for the underlying network and considerable computing capability of the mobile handset. The multimedia service center (MMSC) performs similar tasks as the SMSC for SMS. The following list outlines the necessary steps of an MMS procedure:

» The transmitter sends a message to the MMSC from a cell phone, PDA, or networked computer.

» The MMSC replies to the transmitter with a confi rmation of “ message sent. ” In fact, it is not sent to the receiver yet, as the message is stored at the MMSC.

» The MMSC locates the receiver with the help of a number of cellular network elements, such as MSCs, HLRs, and VLRs. If the mobile station of the receiver is ON, the MMSC sends a notifi cation of a new message to it, along with a URL to the new message. Otherwise, it waits and tries again later

» The receiver can choose to download the message right away or save the URL to download it later.

» The MMSC will be notifi ed by the receiver that the message has been downloaded and presumably read. Then the MMSC notifi es the transmitter that the message has been delivered.

MMS is the natural evolution of SMS, with EMS as an optional intermediate messaging service, but it is very unlikely that MMS will replace SMS completely as plain text messages are preferable in many cases. Additionally, MMS does not require 3G; it can be done in 2.5G systems such as GPRS and EDGE. Problems that may hinder the widespread use of MMS include digital rights management of content being exchanged among many mobile subscribers, development of a user-friendly interface design, and sufficiently large bandwidth for message delivery.

Source of Information : Elsevier Wireless Networking Complete 2010


Subscribe to Developer Techno ?
Enter your email address:

Delivered by FeedBurner