10 Slides to SMS
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Transcript of 10 Slides to SMS
SMS
The Telecom Source10 Slide Technology Series
SMS Overview
SMS stands for Short Message Service
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 (Global System for Mobile communications) GPRS (General Packet Radio Service) CDMA (Carrier Division Multiplex Access)
SMS supports the sending and receiving of text, images, animation and sound
SMS messages are originated and received by Short Messaging Entities (SME). Examples of SMEs are: mobile phones; servers; personal computers
Basic Network Architecture
SMS-GMSC/SMS-IWMSC
HLR
SME MSSMSC MSC/SGSN
VLR
Outside the scope of GSM specifications
1. Short Message Entity (SME) – sends or receives short messages2. Short Message Service Centre (SC) – stores-and-forwards messages between the SME and the MS3. Gateway 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• Home Location Register (HLR) - a database used for permanent storage and management
of user/subscriber profiles4. Inter-Working MSC For Short Message Service (SMS-IWMSC) - receives messages from the MSC or
SGSN and forwards them to the SC5. Mobile Service Centre (MSC) – performs switching functions for mobile stations in a geographical area
• Visitor Location Register (VLR) - a database that contains temporary information about roaming subscribers. The MSC and the VLR are always on the same platform.
6. Serving GPRS Support Node (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.
7. Mobile Station (MS) – a device on the mobile network capable of receiving and sending short messages
SMS Protocol Services and Features SMS is a point-to-point store and forward technology with 2 basic
services: Short Message Mobile Terminated (SM-MT) - to transmit a message from the short
message service centre to the mobile station. – SMS-DELIVER PDU (Protocol Data Unit) Short Message Mobile Originated (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 (Signaling System 7
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
SM-MT Service - SMS-DELIVER TPDU Structure
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
PDU Type:
Bits7 6 5 4 3 2 1 0
RP UDHI SRI MMS MTI
MTI bit 1 = 0 bit 0 = 0
Parameter Description
SCA Service Centre Address - Telephone number of the Service Centre
PDU Type Protocol Data Unit Type
RP Reply Path - Parameter indicating that Reply Path exists
UDHI User Data Header Indicator - Parameter indicating that UD field contains a header
SRI Status Report Indication - Parameter indicating if the SME has requested a status report
MMS More Messages to Send - Parameter indicating whether or not there are more messages to send
MTI Message Type Indicator - Parameter describing the message type 00 means SMS-Deliver
OA Originator Address - Address of the originating SME
PID Protocol Identifier - Parameter indicating the SMSC how to process the Short Message (e.g. Fax)
DCS Data Coding Scheme - Parameter identifying the coding scheme within the User Data (UD)
SCTS Service Centre Time Stamp - Parameter identifying the time when the SMSC received the message
UDL User Data Length - Parameter indicating the length of the UD-field
UD User Data - Data Field of the Short Message
SM-MO Service - SMS-SUBMIT TPDU Structure
Bits
PDU Type:
MTI bit 1 = 0 bit 0 = 1
Parameter Description
SCA Service Centre Address - Telephone number of the Service Centre
PDU Type Protocol Data Unit Type
RP Reply Path - Parameter indicating that Reply Path exists
UDHI User Data Header Indicator - Parameter indicating that UD field contains a header
SRR Status Report Request - Parameter indicating if the MS has requested a status report
VPF Validity Period Format - Parameter indicating whether or not the VP field is present
RD Reject Duplicates – parameter indicating if SMSC will accept a message with same MR and DA from the same OA
MTI Message Type Indicator - Parameter describing the message type 01 means SMS-Submit
MR Message Reference - Successive numbers (0…255) of all SMS-SUBMIT frames sent by the MS.
DA Destination Address - Address of the destination SME
PID Protocol Identifier - Parameter indicating the SMSC how to process the Short Message (e.g. Fax)
DCS Data Coding Scheme - Parameter identifying the coding scheme within the User Data (UD)
SCTS Service Centre Time Stamp - Parameter identifying the time when the SMSC received the message
UDL User Data Length - Parameter indicating the length of the UD-field
UD User Data - Data Field of the Short Message
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
7 4 3 2
RP UDHI SRR RD MTI
Message Flow SM-MT
MessageTransfer
sendRoutingInfo-
Delivery
ForShortMsg
forwardShortMessage
sendInfoFor-
MT-SMS
Message TransferDeliver Report
SM-DeliveryReportStatus
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)
Message Flow SM-MO
MessageTransferDelivery
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
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 (External Machine Interface) – CMG, now LogicaCMG UCP (Universal Computer Protocol) – Logica, now LogicaCMG CIMD (Computer Interface to Message Distribution) – Nokia OIS (Open Interface Specification) – SEMA Group, now Airwide Solutions Computer Access Service and Protocol – Ericsson
SMS Forum is an industry initiative to create a common standard “SMPP” (Short Message Peer-to-Peer) 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
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 (Subscriber Interface Module) card