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SMS FAQ

What is SMS?

Short Message Service (SMS) is the ability to send and receive short alphanumeric messages to and from mobile telephones. SMS can also be used as a transport for binary payloads and to implement the WAP stack on top of the SMSC bear. SMS was created as part of the GSM Phase 1 standard.

Why use SMS?

SMS allows users to directly transmit messages to each other without the use of an operator (it is, however, necessary to have the underlying operator controlled wireless service). The first user can send a message to a mobile unit, via a direct connect computer. The SMS protocol of messaging is also "smarter" then standard paging. SMS is a store and forward method therefore, if the end user is not available, the mobile unit is powered off, or the unit is outside a service area, when the unit comes back on line the message will appear. A SMS message can also be sent "certified," where it will notify the message originator of the end user's receipt of the message.

How would you send an SMS Message over the Internet?

The front-end would simply be a section for the message (limit) and a destination address (mobile number). Then, based on your architecture, a lower layer would have to create the correct message based on the request or the message is generate server side. In the case of an end-user sending a message to a mobile unit, it would be a SMS-DELIVER message. Then entire message would then be "encapsulated" in a TCP/IP message and send to the appropriate Short Message Service Centre (SMSC). The MSC would then remove the TCP/IP layer from the message and process the message as if it were generated locally by an operator.

What are some other uses for SMS?


Voice/Fax Notifications

Delivery of Replacement Ringtones, Operator Logos and Group Graphics
Mobile users will select features or options for their phone (ideally from a web site). They enter their mobile number and the feature is sent to their phone via SMS message in a matter of seconds. The user then has the option to select and save or to delete.

Unified Messaging
Using a single interface, unified messaging users are able to access all forms of messages (voice mail, email, fax) from a single point.

Direct communication
End users can send and receive SMS messages without the use of an operator.

Does SMS support all languages?

SMS is able to support any language, but that language is dependent more on how the handset is configured than anything else. Every region supports different languages and each software build for every phone is different. In the Americas, phones typically support English, Spanish, and Portuguese. In Europe it is vastly different.

What are the two types of SMS?

Point-to-Point and Point-to-Omnipoint (cell broadcast)

What is Point-to-Point?

Point-to-Point uses a dedicated link between the network and the mobile station allowing bidirectional messaging without operator interaction.

What is the maximum length of a Point-to-Point short message?

Two-way data transport = 140 Octet Data Payload Supports Either: 140 bytes for binary data transport (PDU format) 160 characters for text messaging transport (7-bit ASCII).

What are the two types of Point-to-Point messages?

Mobile originated (MO) and Mobile terminated (MT).

What is SM-MT (short message - mobile terminated)?
SM-MT denotes the capability of the GSM system to send a message from the SC to an MS 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 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, e.g. speech, telex, or facsimile.

What is SM-MO (short message - mobile originated)?

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 MS about the delivery or failure of that message. These messages may be destined for other mobile users, or for subscribers on a fixed network.

What are the specific types of Point-to-Point messages?

SMS-DELIVER: sending a short message from the SC to the MS.
SMS-DELIVER-REPORT: replying with an error cause.
SMS-SUBMIT: sending a short message from the MS to the SC.
SMS-SUBMIT-REPORT: reply with an error cause.
SMS-STATUS-REPORT: sending a status report from the SC to the MS.
SMS-COMMAND: sending a command from the MS to the SC.

What is Point-to-Omnipoint?

Point-to-Omnipoint, or Cell Broadcast, sends messages to predetermined cell broadcast areas. Unlike Point-to-Point messaging, Cell Broadcast does not use a dedicated link. The network operator is where all messages originate and the recipients include all users within a given cell, area, or network. Also unlike Point-to-Point, CB messages do not provide any assurance that the message was recieved.

What is the maximum length of a Point-to-Omnipoint short message?

A Point-to-Omnipoint short message is a maximum of 93 charaters (82 octets) in length.

Where is it determined which MSs will receive which CB messages?

At the origination and termination points. At the origination point, the sender (or network operator) broadcasts messages on certain "channels". The sender indicates the frequency and duration of transmission. At the termination point, the user selects which "channels" will be displayed on his mobile station. If the MS is switched on and idle, it is able to identify and ignore re-broadcasts of messages that have already been received.

How do mobiles know to display only those messages desired by the MS user?

CB messages are assigned message classes that categorize the type of information contained in the message.

What are the error conditions that can return to an SC from an MS?

Unknown subscriber: message is rejected because there is no directory number for the mobile subscriber (GSM 09.02).
Teleservice not provisioned: message is rejected because the recipient MS has no SMS subscription (GSM 09.02).
Call barred: message is rejected due to barring of the MS (see GSM 09.02, description of the Barring supplementary service, GSM 02.04 and 03.11, and description of Operator Determined Barring, GSM 02.41 and 03.15).
Facility not supported: the message is rejected due to no provision of the SMS in the VPLMN (GSM 09.02).
Absent subscriber: The message is rejected because there was no paging response (GSM 04.08), the IMSI record is marked detached (GSM 09.02), or the MS is subject to roaming restrictions (GSM 09.02).
MS busy for MT SMS: The message is rejected because of congestion encountered at the visited MSC.
SMS lower layers capabilities not provisioned: message rejected due to MS not being able to support the SMS. The short message transfer attempt is rejected either due to information contained in the class-mark, or the MSC not being able to establish connection at SAPI (GSM 04.08 and 09.02).
Error in MS: message rejected due to an error occurring within the MS at reception of a short message (lack of memory or protocol error).
Illegal subscriber: message rejected because of failed authentication.
Illegal equipment: message rejected because the MS was black-listed.
System failure: message rejected due to network or protocol failure.
Memory capacity exceeded: message rejected because the MS doesn't have enough memory.
How can SMS be used to program phones?

Nokia has created a new protocol called Smart Messages which sends configuration messages to mobile phone units with header definitions stating that the message is a configuration message. These Smart Messages make use of the SMS protocol.

What are the classes of SM-MT (mobile terminated) messages?

Classes identify the message's importance as well as the location where it should be stored. There are 4 message classes.
Class 0: Indicates that this message is to be displayed on the MS immediately and a message delivery report is to be sent back to the SC. The message does not have to be saved in the MS or on the SIM card (unless selected to do so by the mobile user).
Class 1: Indicates that this message is to be stored in the MS memory or the SIM card (depending on memory availability).
Class 2: This message class is Phase 2 specific and carries SIM card data. The SIM card data must be successfully transferred prior to sending acknowledgement to the SC. An error message will be sent to the SC if this transmission is not possible.
Class 3: Indicates that this message will be forwarded from the receiving entity to an external device. The delivery acknowledgement will be sent to the SC regardless of whether or not the message was forwarded to the external device.