A tutorial overview of the short message service within GSM

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A tutorial overview of the short message service
within GSM

• By G. Peersman, P. Griffiths, H. Spear, S.
  Cvetkovic and C. Smythe

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Outline

• Short message service
• GSM network and protocol architecture
• Practical implementation
• Short message routing considerations
• Protocols for short message submission
• Text based protocols
• Current issues

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Short message service

• It suitable for applications such as paging,
  E-mail or voicemail notification, messaging
  services for multiple users.
• Facilities and charges depend on operator.
• Types of SMS
• Cell boardcast one way and no confirmation of
  receipt will be sent. It can send up to 93 7-bit
  characters or 82 8-bit characters, typically used
  to transmit messages about traffic conditions,
  weather forecasts, stock market price etc.
• Point to point messages sent from one MS or a PC
  to a MS and vice versa. The messages are
  maintained and transmitted by a SMSC.

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GSM network architecture

• The layout of a generic GSM network with its
  several functional entities is shown as follows

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GSM protocol architecture

• Signaling Plane

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GSM protocol architecture(cont.)

• CM managing call-related supplementary services,
  the SMS, and call independent supplementary
  services support.
• MM providing functions to establish, maintain
  and release a connection between the MS and the
  MSC. It also performs location updating, IMSI
  management, and TMSI identification,
  authentication and reallocation.
• RR establishing the physical connection over the
  radio link to transmit call-related signaling
  information such as the establishment of the
  signaling and traffic channel.

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GSM protocol architecture(cont.)

• SS7 (Signaling System Number 7) is currently the
  only element of the GSM infrastructure capable of
  packet and circuit switching.

• The SCCP sublayer supports connectionless and
  connection-oriented services to transfer data and
  global title translation.
• MTP level 1 defines the characteristics of the
  digital signaling network.
• MTP leve2 provides a reliable sequenced delivery
  of data packets.
• MTP level3 provides congestion control, signaling
  management, and message discrimination,
  distribution and routing.

• SS7 protocol stack

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Practical implementation

• The short message service uses the signaling
  channel SS7 to transmit the data packet
  regardless of whether there is a speech or data
  call in progress.
• A confirmation will always be returned to the
  SMSC. A confirmation will also be returned to the
  MS from an SMSC.
• SMS network architecture

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Practical implementation(cont.)

• Protocol architecture
• Protocol data unit types at the SM-TL

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Practical implementation(cont.)

• The elements of the SMS-deliver and SMS-submit
  TPDU

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Practical implementation(cont.)

• TP-User Data(TPUD)

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Short message routing considerations
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Protocols for short message submission

• ETSI specified a protocol for short message
  submission as part of the overall GSM standard.
• The specification defines three interface
  protocols for the transfer of SMS short message.
• Block mode binary protocol, error detection and
  functions
• Submit a short message
• Delete messages from the phone
• List messages in the phone
• Transfer all or one message from the phone to the
  application
• Set the phone so that the application is notified
  every time a new short message is received.
• Text mode character-based protocol based on the
  AT commands set modified for GSM.
• PDU mode it is similar to the text mode, except
  that it leaves to the application the
  responsibility to build the short message TPDU.

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Protocols for short message submission

• SEMA SMS2000
• The protocol has been designed to operate over a
  variety of interfaces such as X25, DECnet or SS7.
• Text based protocols are usually proprietary and
  developed as an interface to the SMSC. Key
  disadvantages with text-based protocols they
  offer limited support for extended character
  sets, and only work one way.

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Current issues

• New protocols are now being designed that will
  allow even more advanced functionality to be
  implemented in client software.
• Some of the features under development include
• Support for message concatenation to allow up to
  255 messages to e submitted as part of the same
  transaction.
• Support for distribution list creation and
  modification within SMSC, will greatly increase
  short message throughput.
• Research projects
• Using the SMS as an alternative layer to TCP/IP
• WAP over SMS

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