Short Message Service SMS Presented by Yaxiang Yang 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 alphanumeric 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 Benefits of SMS At a minimum SMS benefits include the following Delivery of notifications and alerts Guaranteed message delivery Reliable low cost communication mechanism for concise information Ability to screen messages and return calls in a selective way Increased subscriber productivity Benefits of SMS cont More sophisticated functionality provides the following enhanced subscriber benefits Delivery of messages to multiple subscribers at a time Ability to receive diverse information E mail generation Creation of user groups Integration with other data and Internet based applications Benefits of SMS cont The benefits of SMS to the service provider are as follows Ability to increment average revenue per user due to increased number of calls on wireless and wireline networks by leveraging the notification capabilities of SMS An alternative to alphanumeric paging services which may replace or complement an existing paging offer Ability to enable wireless data access for corporate users New revenue streams resulting from addition of value added services such as e mail voice mail fax and Web based application integration reminder service stock and currency quotes and airline schedules Provision of key administrative services such as advice of charge overthe air downloading and over the air service provisioning Protection of important network resources such as voice channels due to SMS sparing use of the control and traffic channels Notification mechanisms for newer services such as those utilizing wireless application protocol WAP Network Elements and Architecture The basic network structure of the SMS in an IS 41 network 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 External Short Messaging Entities cont E Mail Probably the most demanded application of SMS is the ability to deliver e mail notifications and to support two way e mail using an SMS compliant terminal The SMSC must support interconnection to email servers acting as message input output mechanisms Others There are several other mechanisms to submit short messages to the SMSC that include but are not limited to paging networks specialized software for PC based messaging and operator bureaus STP and HLR Signal Transfer Point The STP is a network element normally available on IN deployments that allows IS 41 interconnections over signaling system 7 SS7 links with multiple network elements HLR The HLR is a database used for permanent storage and management of subscriptions and service profiles Upon interrogation by the SMSC the HLR provides the routing information for the indicated subscriber Also if the destination station was not available when the message delivery was attempted the HLR informs the SMSC that the station is now recognized by the mobile network to be accessible and thus the message can be delivered VLR and MSC Visitor Location Register VLR The visitor location register is a database that contains temporary information about subscribers homed in one