Introduction for SMS in GSM system

  • A mechanism of delivery of short messages over the mobile networks
  • A store and forward way of transmitting
  • Text or binary Non-Text message
  • Return receipts
  • Use signaling channel
  • Support national and international roaming
  • Many operators offer e-mail service over SMS
  • Information services like news, weather, entertainment and stock prices etc
  • Mobile chatting
  • used to notify users
  • an alternative to alphanumeric paging services
  • Downloading new ring tones

SMS architecture

Type of SMS

  • Cell Broadcast: one way and no confirmation of receipt will be sent. It can send up to 93 7-bit characters or 82 8-bit characters
  • Point-to-Point: messages sent from one MS or a PC to a MS

SMS Architecture

  • Short Message Center(SMC)
    • the job of store and forward of messages to and from the MS
  • Short Message Entity(SME)
    • PC or MS ,send or receive messages
  • SMS GWMS (SMS gateway MSC)
    • receive short messages
    • interrogate the current position of the MS form the HLR
  • Home Location Register(HLR)
    • main database in a mobile network
    • holds information of the subscription profile of the mobile and also about the routing information for the subscriber
  • Mobile Switching Center(MSC)
    • the job of switching connections
  • Visitor Location Register(VLR)
    • temporary information about the mobile
  • Base Station System(BSS)
    • BSC+BTSs
    • transmits the short message to the mobile

Submit & Receive messages

Protocol Architecture

Limitations of SMS

  • You can only send simple text messages
  • The messages are limited by size
    • Max:160 chars
  • The limitation of easy input mechanisms in mobile devices makes it very uncomfortable sending messages larger than even 5-6 words
  • SMS protocol data units as defined in GSM 03.40 are also not very efficient
  • Data rate and latency
  • The store and forward nature of SMS, though useful in many applications makes SMS not very suitable for WAP

EMS (Enhanced Messaging Service)

  • technical specification: 3G TS 23.040
  • richer message that are combination of text, simple melodies, pictures and animations
  • needs no upgrade to the network infrastructure
  • handsets need to be EMS compliant


  • MMS is a new service
  • changes in the network infrastructure
  • allows a combination of text, sounds, images and video to be transferred
  • MMS may run on any bearer service
  • MMS needs a dedicated channel

General View of MMS



  • MMS Relay/Server
  • MMS User Databases
  • MMS User Agent
  • MMS VAS Applications

Services offered

  • Submission of a Multimedia Message
  • Reception of a Multimedia Message
  • Retrieval of a Multimedia Message
  • Forwarding of a Multimedia Message without prior Retrieval
  • Delivery Report
  • Read-Reply Report
  • Support for Streaming
  • Address Hiding
  • Support for Reply-Charging

In conclusion, SMSC and MMS provide a very convenient method of exchanging small bits of information between mobile users. Sending and receiving messages not only saves time but costs less as well. SMS should no longer be treated as a value added service in mobile networks.