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10 Slides to SMS
- 1. SMS The Telecom Source 10 Slide Technology Series
- 2. SMS Overview SMS stands for S hort M essage S ervice SMS was first introduced in 1991 in Europe as a text messaging service based on European Telecommunications Standards Institute (ETSI) standards for mobile networks SMS is being used in a wide range of social and business applications such as electronic voting, delivery of stock quotations, delivery of e-mail notification SMS is currently supported on the major mobile network technologies including: GSM ( G lobal S ystem for M obile communications) GPRS ( G eneral P acket R adio S ervice) CDMA ( C arrier D ivision M ultiplex A ccess) SMS supports the sending and receiving of text, images, animation and sound SMS messages are originated and received by S hort M essaging E ntities (SME). Examples of SMEs are: mobile phones; servers; personal computers
- 3. Basic Network Architecture SMS-GMSC/ SMS-IWMSC HLR SME MS SMSC MSC/SGSN VLR Outside the scope of GSM specifications S hort M essage E ntity (SME) – sends or receives short messages S hort M essage S ervice C entre (SC) – stores-and-forwards messages between the SME and the MS G ateway MSC For Short Message Service (SMS-GMSC) - receives messages from the SC, interrogates the HLR for routing information and forward the messages to the MSC or SGSN H ome L ocation R egister (HLR) - a database used for permanent storage and management of user/subscriber profiles I nter- W orking MSC For Short Message Service (SMS-IWMSC) - receives messages from the MSC or SGSN and forwards them to the SC M obile S ervice C entre (MSC) – performs switching functions for mobile stations in a geographical area V isitor L ocation R egister (VLR) - a database that contains temporary information about roaming subscribers. The MSC and the VLR are always on the same platform. S erving G PRS S upport N ode (SGSN) – performs packet switching functions for mobile stations in a geographical area. The SGSN is used instead of the MSC when SMS info is transferred over GPRS. M obile S tation (MS) – a device on the mobile network capable of receiving and sending short messages
- 4. SMS Protocol Services and Features SMS is a point-to-point store and forward technology with 2 basic services: S hort M essage M obile T erminated (SM-MT) - to transmit a message from the short message service centre to the mobile station. – SMS-DELIVER PDU ( P rotocol D ata U nit) S hort M essage M obile O riginated (SM-MO) to transmit a message from mobile station to service centre – SMS-SUBMIT PDU SMS allows message delivery to handsets either active/in-use or powered off Mobile stations receive transport data protocol units (TPDU) denoted as SMS-Deliver Mobile stations send transport data protocol units (TPDU) denoted as SMS-Submit Note: the TPDU contains the user data (the short message) SMS protocol permits request of message delivery confirmation report SMS messages contain up to 140 octets which is equivalent to: 160 Latin characters (7 Bit Coding) – Text Mode 70 Unicode characters (double byte) e.g. Arabic Characters, Chinese Characters SMS messages can also contain up to 140 octets of binary information SMS messages are transported in the core network using SS7 ( S ignaling S ystem 7
- 5. SMS Service Elements Validity Period is the service element that indicates the time period for which the SMSC will guarantee the existence of the short message when attempting to deliver it Service Centre Time Stamp is the service element that indicates the time stamp of message arrival at the SMSC Protocol Identifier is the service element in to indicate higher layer protocol or indicates inter-working with certain types of telemetic services (e.g. paging, email) More Messages to Send is the service element by which a SMSC informs the MS that there is one or more messages waiting in the SC to be sent to the MS Priority is the service element indicating that delivery of the message will be attempted regardless of the MS being temporarily absent or having no free memory Message Waiting is the service element that enables the mobile network to provide the HLR, SGSN and VLR with the information that there is a message waiting in the originating SMSC for a MS Alert Service Centre is the service element used by mobile networks to inform an SMSC that a previously unreachable MS (temporarily absent or no memory) is ready to receive messages
- 6. SM-MT Service - SMS-DELIVER TPDU Structure PDU Type: Bits MTI bit 1 = 0 bit 0 = 0 1-10 Octets 1 Octet 2-12 Octets 1 Octet 1 Octets 7 Octets 1 Octet 0-140 Octets SCA PDU- Type OA PID DCS SCTS UDL UD 7 6 5 4 3 2 1 0 RP UDHI SRI MMS MTI User Data - Data Field of the Short Message UD User Data Length - Parameter indicating the length of the UD-field UDL Service Centre Time Stamp - Parameter identifying the time when the SMSC received the message SCTS Data Coding Scheme - Parameter identifying the coding scheme within the User Data (UD) DCS Protocol Identifier - Parameter indicating the SMSC how to process the Short Message (e.g. Fax) PID Originator Address - Address of the originating SME OA Message Type Indicator - Parameter describing the message type 00 means SMS-Deliver MTI More Messages to Send - Parameter indicating whether or not there are more messages to send MMS Status Report Indication - Parameter indicating if the SME has requested a status report SRI User Data Header Indicator - Parameter indicating that UD field contains a header UDHI Reply Path - Parameter indicating that Reply Path exists RP Protocol Data Unit Type PDU Type Service Centre Address - Telephone number of the Service Centre SCA Description Parameter
- 7. SM-MO Service - SMS-SUBMIT TPDU Structure Bits PDU Type: MTI bit 1 = 0 bit 0 = 1 7 4 3 2 RP UDHI SRR User Data - Data Field of the Short Message UD User Data Length - Parameter indicating the length of the UD-field UDL Service Centre Time Stamp - Parameter identifying the time when the SMSC received the message SCTS Data Coding Scheme - Parameter identifying the coding scheme within the User Data (UD) DCS Protocol Identifier - Parameter indicating the SMSC how to process the Short Message (e.g. Fax) PID Destination Address - Address of the destination SME DA Message Reference - Successive numbers (0…255) of all SMS-SUBMIT frames sent by the MS. MR Message Type Indicator - Parameter describing the message type 01 means SMS-Submit MTI Reject Duplicates – parameter indicating if SMSC will accept a message with same MR and DA from the same OA RD Validity Period Format - Parameter indicating whether or not the VP field is present VPF Status Report Request - Parameter indicating if the MS has requested a status report SRR User Data Header Indicator - Parameter indicating that UD field contains a header UDHI Reply Path - Parameter indicating that Reply Path exists RP Protocol Data Unit Type PDU Type Service Centre Address - Telephone number of the Service Centre SCA Description Parameter 6 5 1 0 VPF 1-10 Octets 1 Octet 1 Octet 2-12 Octets 1 Octet 1 Octets 0, 1 or 7 Octets 1 Octet 0-140 Octets SCA PDU- Type MR DA PID DCS VP UDL UD RD MTI
- 8. Message Flow SM-MT Message Transfer sendRoutingInfo- Delivery ForShortMsg forwardShortMessage sendInfoFor- MT-SMS Message Transfer Deliver Report SM-Delivery ReportStatus Report SMSC GMSC HLR MSC VLR Page Authenticate MS Note: ETSI/GSM MAP sendRoutingInforForShortMsg equivalent in IS41 (North American standard) is SMSrequest mechanism, while forwardShortMessage is Short Message Delivery-Point-to-Point (SMD-PP)
- 9. Message Flow SM-MO Message Transfer Delivery forwardShortMessage sendInfoFor- MO-SMS Message Transfer Delivery Report Delivery Report Report SMSC SMS-IWMSC HLR MSC VLR Access Request Authenticate MS Note: ETSI/GSM MAP forwardShortMessage equivalent in IS41 (North American Standard) is Short Message Delivery-Point-to-Point (SMD-PP) mechanism
- 10. Short Message Service Centre - SMSC Short Message service Centre plays a central role in the management of SMS message origination and SMS message delivery Interestingly, detailed functionality of SMSC is outside the scope of standardization, hence several vendor specific products and protocols: EMI ( E xternal M achine I nterface) – CMG, now LogicaCMG UCP ( U niversal C omputer P rotocol) – Logica, now LogicaCMG CIMD ( C omputer I nterface to M essage D istribution) – Nokia OIS ( O pen I nterface S pecification) – SEMA Group, now Airwide Solutions Computer Access Service and Protocol – Ericsson SMS Forum is an industry initiative to create a common standard “SMPP” ( S hort M essage P eer-to- P eer) using Internet as the transport network The ETSI/GSM standard does specify minimum mandatory SMSC requirements: Each SMS-Deliver to a MS must have unique time stamp with one second accuracy Only one outstanding SMS-Deliver (i.e. message for which a report not yet received) If requested by MS or SME, initiate overwriting of previously received short messages
- 11. Additional Features and Issues SMS standard allows concatenation of messages to enable transmission of longer messages (i.e. messages longer than 140 octets) Short Messages may be compressed with algorithms described in GSM 03.42 Compression only applies to user-data and excludes user-data-header If compressed message are greater than 140 octets, then the messages can be concatenated In North America wireless subscribers can address text messages using 5-digit numbers (“short codes”) An example of the use of short codes is for SMS voting One objective of short codes is to reduce or minimize Spam Short codes are being used to price and market services (e.g charge back to application provider) Service gateway products are available that address multi-network (GSM/CDMA) and multi-protocol (e.g. EMI/OIS) inter-working Security is an emerging concern similar to that with e-mail, for example: SPAM – sending of unsolicited messages and ads via SMS (e.g. to entice users to call numbers that have a high per minute charge) Virus - resend of message to all numbers in the phone’s address book (e.g. via a Trojan Horse) Identity Theft - retrieval of personal information from a SIM ( S ubscriber I nterface M odule) card
- 12. The Telecom Source www.thetelecomsource.com [email_address]