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`vy.
`IEEE personal communications
`no.
`» a publication of the IEEE
`Com
`a ee eha elDD _
`
`\r
`June 2000
`ttELS MCQUIONS
`
`THE MAGAZINE OF WIRELESS COMMUNICATIONS AND NETWORKING IBM EX. 1016
`
`|
`
`Vol. 7 No. 3
`
`aaa
`
`IBM EX. 1016
`
`1 of 11
`1 of 11
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`

`

`
`
`aiv issue ofJEEE Personal Com-
`
`EDITOR’S NOTE
`
`MAHMOUD
`
`NAGHSHINEH
`
`Our secondarticle isa tutorialon GSM short
`munications contains several articles in the
`message services (SMS). This article is
`areas of mobile and wireless services, wire-
`authored by G. Peersman, 8. Cvetkovic,P. Grif-
`fiths, and H.Spaer, and presents a discussion
`less systems and standards, and issuesrelat-
`ed to wireless links and channel models.
`on SMS integration with existing messaging
`services and its relation to TCP/IP. This
`Thefirst article, by Y. Lin, H. Rao, and
`tutorial starts with a brief overview of GSM net-
`M. Chang,offers an overview of mobile pre-
`workbuilding blocks, and then puts empha-
`paidservices and how suchservices can be pro-
`vided in a wireless network. It covers a
`sis on the SMS network and protocol
`architecture within the GSM framework. Next,
`number of example scenarios as well as
`an overview of the most widely used messag-
`issues such as billing and subscriber call
`ing protocols is provided, andfinally, a sum-
`management with respect to prepaid ser-
`vices. Moreover, this article discusses the
`mary of current and future issues in this
`area Is presented.
`network elements and architectural compo-
`Our nextarticle is authored by D. Koulaki-
`nents for prepaid services. Finally, the
`otis and A. Aghvami, and reviews data detection tech-
`authors provide a comparison between different prepaid
`ystem manage-
`niques for direct sequence code-division multiple access
`solutions based on scalability, fraud risk, s
`mentissues, and service features.
`(DS-CDMA) mobile systems. The authors start by provid-
`
`
`Director of Magazines
`MarkJ. Karol, Lucent Technologies, USA
`Editor-in-Chief
`Mahmoud Naghshineh, JBM Research, USA
`Senior Advisors
`Hamid Ahmadi, AT&T Labs, USA
`ThomasF, La Porta, Lucent Technologies, USA
`Advisory Board
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`(EEE Vehicular Technology Liaison
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`Andrea Goldsmith, Stanford University, USA
`Paul Gough, Philips Research, UK
`Davide Grillo, Fondazione Ugo Bordoni,Italy
`Jaap Haartsen, Ericsson, Sweden
`Takeshi Hattori,NTT, Japan
`Ravi Jain, Bellcore, USA
`Joseph Kabn, UC Berkeley, USA
`Parviz Kermani, IBM Research, USA
`Richard LaMaire, IBM Research, USA
`Yi-Bing Lin, Nationa! Chiao Tung Univ., Tafwan
`Murray Mazer, Open Group ResearchInst., USA
`Sergio Palazzo, University of Catania, Italy
`Ramachandran Ramjee, Lucent Technologies,
`Bell Labs, USA
`Bill Schilit, FX Palo Alto Lab,Inc., USA
`Thomas Y. C. Woo, Lucent Technologies, USA
`Yacov Yacobi, Microsoft Corp., USA
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`Department Editors
`0
`eviews
`Seshadri Mohan, Bellcore, USA
`Conference Review
`.
`Thomas Y. C, Woo, Lucent Technologies, USA
`Scanning the Literature
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`2000 Communications Society
`Board of Governors
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`Officers
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`TEEE Personal Communications * June 2000
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`

`

`Abstract
`This tutorial presents an overview of the Global System for Mobile Communications Short Message Service from the viewpoint of implementing
`new telematic services. SMS offers the users of GSM networksthe ability to exchange alphanumeric messages up to the limit of 160 characters.
`Thetutorial is motivated by an acute absence of research publications in this field. The information gathered in the tutorial was required
`considering the increasing potential SMSoffers for integration with existing messaging services andits ability to offer a successful replacement
`for the Transmission Control and Internet Protocols as far as low-bandwidth-demanding applications are concerned.Initially, the tutorial gives a
`brief overview of the building blocks of GSM networks — the mobile station, base station, and network subsystem — and then emphasizes the
`SMSnetwork and protocol architecture. The most widely used protocols for message submission are then introduced (text-based, SMS2000,
`ETSI 0705, TAP) and compared in termsof features provided andflexibility to handle extended alphabets or two-way messaging. Finally the
`tutorial outlines a summary of current and future issues for further development and researchin the light of novel features for submission
`protocols and telematic services.
`
`The Global System for
`Mobile Communications
`Short Message Service
`
`
`
`GUILLAUME PEERSMAN AND SRBA CVETKOVIC,
`
`THE UNIVERSITY OF SHEFFIELD
`
`PAUL GRIFFITHS AND HUGH SPEAR, DIALOGUE COMMUNICATIONS LTD.
`
`to send and/or receive alphanumeric messages. The short
`since the first Global System
`messages can be up to 140 bytes in length, and are delivered
`for Mobile Communications (GSM) network started opera-
`within a few seconds where GSM coverageis available. More
`tion in 1991, more than 100 countries have adopted the stan-
`dard. Over 20 million subscribers of GSM networks are now
`than a commonpagingservice, the delivery of the message is
`guaranteed even whenthe cellular terminal is unavailable
`offered worldwide coverage, outstanding voice quality over a
`whole range of operating conditions, and a variety of value-
`(e.g., when it is switched off or outside. the coverage area).
`added services. These services include voice mail, call han-
`The network will hold the message and deliver it shortly after
`the cellular terminal announces its presence on the network.
`dling facilities, call line identification, and Short Message
`The fact that SMS (through GSM) supports international
`Service (SMS).
`roaming with very low latency makesit particularly suitable
`With SMS,users are able to exchange alphanumeric mes-
`for applications such as paging, e-mail, and voice mail notifi-
`sages (up to 160 characters) with other users of digital cellular
`cation, and messaging services for multiple users. However,
`networks, almost anywhere in the world, within seconds of
`the facilities offered to users and the charges for these facili-
`submission. Even if the service was originally conceived as a
`ties still mainly depend onthelevel of service provided by the
`paging mechanism for notifying the users of voicemail mes-
`sages, SMS is now increasingly used as a messaging service.
`network operator.
`There are two types of SMS available: cell broadcast [1]
`The messagesare typically created on mobile phone keypads,
`and point-to-point [2]. In cell broadcast, a message is trans-
`which is somewhat awkward. Fortunately, there are other
`mitted to all the active handsets or mobile stations (MSs) pre-
`ways to access the message centers, as discussed in this article.
`sent in a cell that have the capability of receiving short
`Numerousapplications are already available and make short
`message reception and submission possible using a computer.
`messages and have subscribed to this particular information
`service. This service is only one-way, and no confirmation of
`Gatewayarchitectures are also being widely implemented and
`receipt will be sent. It can send up to 93 7-bit character or 82
`connect company’s e-mail or voicemail systems to the SMS.
`8-bit characters, typically used to transmit messages about
`The practical implementation of SMS and the different
`traffic conditions, weather forecast, stock market, and so on.
`protocols for message submission ate addressedin thisarticle.
`In point-to-point service, messages can be sent from one
`The future of SMS anda brief review of the fields currently
`mobile to another or from a PC to a mobile and vice versa.
`being studied will concludethis article.
`These messages are maintained and transmitted by an SMS
`The Short Message Service
`Center (SMSC). The SMSC is an electronic form of ordinary
`mail postal service that stores and then forwards the messages
`whenthey can be delivered. Each GSM network must support
`Developed as part of the GSM Phase 2 specification, the
`one or more SMSCsto sort and route the messages. Each
`Short Message Service, or SMS as it is more commonly
`SMSCchecks, organizes, and sends the message to the opera-
`known,is based on the capability of a digital cellular terminal
`
`
`
`IEEE Personal Communications * June 2000
`
`1070-9916/00/$10.00 © 2000 IEEE
`3 of 11
`3 of 11
`
`—
`
`15
`
`
`

`

`‘'‘t''''''’'1’1’',’'t1
`
`
` Operation and
`maintenance center
`
`
`?
`
`Network subsystem
`
`Auc: Authentication centre
`EIR:
`Equipmentidentity register
`HLR:
`Homelocation register
`VLR:
`Visitor location register
`
`
`
`
`
`
`
`Basestation subsystem
`
`U
`
`Other base station subsystem1
`v
`'
`'
`'
`‘
`
`\
`
`i'
`
`'
`'
`1
`'
`1
`1
`1
`
`
`SIM
`
`Mobile ©
`Station
`
`
`
`'1'''
`
`
`Data communication
`
`
`network
`
`
`
`
`
`BTS:
`Base transceiver station
`BSC:
`Base station controller
`SIM:
`Subscriber identity module
`ME:
`Mobile equipment
`Figure 1. The basic GSM networkarchitecture.
`
`tor. It also receives and passes on any confirmation messages to
`any GSM mobile on any network. However, in practice, there
`are no agreements to allow SMSto travel between networks.
`There are several ways in which a short message can be
`submitted, depending on the interfaces supported by the GSM
`network SMSC. Users can call a central paging bureau (i.e.,
`an operator), or directly create the message on the keypad of
`their handset. Typing the messages is made easier when using
`a personal digital assistant (PDA) or a laptop connected to
`the handset. A few SMSC equipment manufacturers and com-
`panies have also developed their own protocols for short mes-
`sage submission. Consequently, more and more GSM
`networks now offer access to their SMSC using these proto-
`cols over a variety of hardware interfaces: modem dialup,
`X25, and even the Internet.
`
`GSM Network Architecture
`
`SIM. Because the IMEI and IMSI are independent, personal
`mobility is possible. The SIM can be protected against unau-
`thorized use by a personal identity number (PIN).
`The Base Station Subsystem
`The base station subsystem is composed of two parts, the
`base transceiver station (BTS) and base station controller
`(BSC). They communicate across the specified Abis inter-
`face, thus allowing network operators to use components
`made by different suppliers. The BTS houses the radio
`transceivers that define a cell and handle the radio link pro-
`tocols with the MS. Depending on the density of the area,
`more or fewer BTSs are needed to provide the appropriate
`capacity to the cell. Digital communications system (DCS)
`networks working at 1800 MHz need twice the number of
`BTSs to cover the same area as GSM networks, but provide
`twice the capacity.
`The BSC manages the radio resources for one or more
`BTSs via the standardized Abis interface. It handles radio
`channel setup, frequency hopping, and handovers. The BSCis
`the connection between the MS and the mobile switching cen-
`ter (MSC). The BSC also takes care of converting the 13 kb/s
`voice channel used over the radio link (Um interface) to the
`standardized 64 kb/s channel used by the public switched tele-
`phone network (PSTN).
`The Network Subsystem
`The Mobile Station
`The MSC is the main component of the network subsystem.
`Its provides the same functionality as a switching node in a
`The MS and base station subsystem communicate across the
`Um interface, also known as the air interface or radio link.
`PSTNor integrated services digital network (ISDN), but also
`takes care of all the functionality needed to handle a mobile
`The base station subsystem communicates with the network
`subscriber such as registration, authentication, location updat-
`subsystem across the A interface. The MS consists of the
`ing, handovers, and routing to a roaming subscriber. The
`physical terminal and contains the radio transceiver, the dis-
`MSC also acts as a gateway to the PSTN or ISDN, and pro-
`play and digital signal processors, and the Subscriber Identity
`vides the interface to the SMSC.
`Module (SIM). The SIM provides the user with the ability to
`access their subscribed services regardless of the location and
`The international roaming and call routing capabilities of
`the terminal used. The insertion of the SIM in any GSM cel-
`GSM networks are provided by the home location register
`(HLR)andvisitor location register (VLR) together with the
`lular phone allows the user to access a network, make and
`MSC. The HLR database contains all the administrative infor-
`receive phone calls, and use all the subscribed services.
`mation about each registered user of a GSM network along
`The International Mobile Equipment Identity (IMEI)
`with the current location of the MS. The current location of
`uniquely identifies the mobile terminal according to the Inter-
`an MSis in the form of a Mobile Station Roaming Number
`national Mobile Subscriber Identity (IMSI) contained in the
`
`The layout of a generic GSM network with its several func-
`tional entities is shown in Fig. 1 [3]. The architecture can be
`divided in three main components:
`* The subscriber holds the MS, namely the GSM terminal
`* The base station subsystem controls the radio link with the
`MS
`* The network subsystem performs the switching of calls and
`other management tasks such as authentication.
`
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`
`
`
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`
`
`Um air interface
`A interface
`Msc
`
`
`|
`
`Ms
`
`cM
`
`MM
`
`td
`RM
`Laem
`
`!
`
`|
`
`BSS
`:
`MM
`
`BSSAP
`BSSAP
`|
`
`sccP
`ScCP
`|
`SccP
`MTP
`MTPlevel 3
`at
`eee=
`
`cM
`
`MAP
`
`ISDN
`TUP
`
`MTP
`
`:
`
`rom
`
`=
`
`Datalink layer
`
`;
`
`:
`TDMA/FDMA
`TDMA/FDMA
`
`[| Messagelayer
`[ie]
`M@ Figure 2. The GSMprotocolarchitecture.
`
`TUP
`
`ISUP
`
`MAP
`
`TCAP
`
`
`sccp
`
`MTP level 3
`
`
`(MSRN), typically the $S7 number of
`the visited MSC, and used to route a
`call to the MSC where the mobile is
`actually located.
`The VLR is usually located within
`the MSC to speed up access to the
`information required during a call and
`simplify the signaling. The content of
`the VLRis a selection of the informa-
`tion from the HLR,basically all neces-
`sary information for call control and
`provision of the subscribed services,
`for each single mobile currently locat-
`ed in the geographical area controlled
`by the VLR.
`The network subsystem uses two
`other databases for authentication and
`security purposes, The Equipment
`Identity Register (EIR) containsa list
`of each MS IMEIallowed on the network. The authentication
`center (AuC) database contains each single PIN stored in the
`MSSIM.
`
`tion over the radio link to transmit
`call-related signaling information such
`as the establishment of the signaling
`and traffic channel between the MS
`and the BSS.
`On the MSCside, the message layer
`is divided into four sublayers. The
`Base System Substation Application
`Part (BSSAP) of the MSC provides
`the channel switching functions, radio
`resources management, and internet-
`working functions. The Message
`Transfer Part (MTP) and Signaling
`Connection Control Part (SCCP) pro-
`tocols are used to implement the data
`link layer and layer 3 transport func-
`tions.for carrying the call control and
`mobility management signaling mes-
`sages across the A interface. SCCP
`packets are also used to carry the messages for SMS.
`Signaling between the different entity uses the Internation-
`al Telecommunication Union (ITU) SS7, widely used in ISDN
`and current public networks. SS7 is currently the only element
`The GSM Signaling Protocol
`of the GSM infrastructure capable of packet switching as well
`as circuit switching. It is used to transport control signals and
`The exchange of signaling messages regarding mobility, radio
`resources, and connection management between the different
`short message packets for SMS. The protocol consists of the
`Mobile Application Part (MAP), Transaction Capability
`entities of a GSM networkis handled through the protocol
`Application Part (TCAP), SCCP, MTP, and ISDN-User Part
`architecture, as shown on Fig.2.
`(ISUP) or Telephone User Part (TUP). Figure 3 depicts the
`The architecture consists of three layers: physical, data
`link, and message. The physical layer and channel structure
`SS7 protocolstack.
`The ISUP provides the signaling functions needed to sup-
`are described in detail by M. Mouly and M. Pautet [4]. Layer
`port switched voice and data applications in the ISDN envi-
`2 implements the data link layer using a modified flavor of the
`ronment. The TUP provides the basic functionality for call
`Link Access Protocol (LAPD) to operate within the con-
`control functions for ordinary national and internationaltele-
`straints set by the radio path. On the MS side, the message
`phone calls. The TCAPis an application layer protocol. It
`layer consists of three sublayers: connection management
`(CM), mobility management (MM), and resource manage-
`allows an application at one node to invoke an execution of a
`procedure at another node and exchange the results of such
`ment (RR). The CM sublayer managescall-related supple-
`invocation. It isolates the user application from the complexity
`mentary services, SMS, and call-independent supplementary _
`of the transaction layer by automatically handling transaction
`services support. The MM sublayer provides functions to
`establish, maintain, and release a connection between the MS
`and invocation state changes, and generating the abort or
`reject messages in full accordance with ITU and American
`and the MSC,over which an instance of the CM sublayer can
`National Standards Institute (ANSI) standards. The MAP
`exchange information with its peer. It also performs location
`uses the TCAPservices to provide the signaling capabilities
`updating, IMSI management, and Temporary Mobile Sub-
`scriber Identity (TMSI) identification, authentication, and
`required to support the mobile capabilities.
`The MTP and SCCP(Fig. 4) correspond to the lower three
`reallocation. The RR sublayer establishes the physical connec-
`
`
`
`
`MTPlevel 2
`
`MTPlevel 1
`
`
`
`a Figure 3. ‘The SS7protocolstack,
`
`TEEE Personal Communications * June 2000
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`TCAP/ISUP/TUP
`
`Tt
`===
`
`
`SCCP
`management
`
`|
`:
`
`
`
`Signaling message
`handling
`
`Signaling network
`handling
`Soa) See eae tae ae ghee Sl
`
`mation will always be returned to the SMSC
`indicating whether the MS has received the short
`message or not. A confirmation will also be
`SCCP connection-
`SCCP connectionless||;
`}
`returned to the MS from an SMSC indicating
`.!
`oriented control
`ee ee ey
`control
`iy!
`'
`whether the TPDU has been received successful-
`ly. The software within the MS must be able to
`decode and store the messages.
`SMS Mobile Terminated (SMS-MT) is the
`ability to receive an SMS message from an
`SMSC and is more ubiquitous, while SMS
`Mobile Originated (SMS-MO) is the ability to
`send short messages to an SMSC. Messages can
`also be stored on the SIM, which can be
`retrieved at a later time. Whenthe phone is not
`within coverage or the SIM is full, the SMSC
`will hold the message and deliver it shortly after
`the phone comes back into range or there is
`space in memory.
`
`'
`:
`:
`
`agneing fink
`unctions
`
`}
`
`MTP
`
`| Signaling data link
`functions
`
`
`
`
`Ms
`
`The SMS Basic Network Architecture
`The main components of the SMS network archi-
`tecture are shownin Fig.5.
`When routing a mobile originated short mes-
`sage, the SMSC forwards the short message to
`the SMS-GMSC. The SMS-GMSC interrogates
`the HLR for routing information and sends the
`short message to the appropriate MSC. The
`MSC delivers the short message to the MS. On
`the other hand, when routing a mobile terminat-
`ed short message, the MS addresses the required
`SMSC according to its global title. If roaming
`abroad the visited public limited mobile network
`(PLMN) will route the short message to the
`appropriate SMS-IWMSC.
`The SMSCidentifies each short message unique-
`ly by adding a time stamp in the SMS-DELIVER
`TP-SCTSfield. The short message arrival at the
`SMSCis accurate to the second. It is the SMSC’s
`responsibility to assure that if two or more short
`message arrive within the same secondtheir time-stampswill be
`different.
`The MS has to be able to receive/submit a short message
`TPDU, and then return a delivery report upon successful
`reception. It is also responsible for notifying the network
`when it has memory capacity available to receive one or more
`messages, if it had previously rejected a short message because
`its memory capacity was exceeded.
`
`SMSC
`
`
`
`SMS-GMSC/
`SMS-IWMSC
`
`ge}
`
`MSC
`
`
`
`
`
`
`HLR
`
`VLR
`
`
`
`@ Figure 5. The SMS network architecture.
`
`layers of the open system interconnection (OSI) model(Fig. 4).
`The SCCP sublayer supports connectionless and connection-
`oriented services to transfer data and Global Title Translation
`(GTT) above MTPlevel 3 for voice, data, ISDN, and GSM ser-
`vices. The data transfer is reliable, independent of the underly-
`ing hardware, and transparent to users. The protocol employs
`logical signaling connections within the SS7 network to ensure
`reliability and integrity of the ongoing data transfer. The MTP
`is divided into three levels:
`* MTPlevel 1 defines the characteristics of the digital signal-
`ing link and is equivalent to the OSI physicallayer.
`* MTPlevel 2 is equivalent to the OSI data link layer and
`provides a reliable sequenced delivery of data packets
`across MTPlevel1.
`* MTPlevel 3 provides congestion control, signaling manage-
`ment, and message discrimination, distribution,
`and routing in a similar way as the OSI network
`Conveyinga short messagefrom the SMSCto the MS
` SMS-Deliver
`|
`layer.
`
`
`
`SMS-Deliver-Report
`Practical Implementation
`
`Conveying a short messagefrom theMS to the SMSC
`SMS-Submit
`SMSuses the SS7 signaling channel to transmit the
` SMS-Submit-Report
`Conveying a failure cause
`
`data packet [5], thus allowing a text message to be
`received when the user is making a voice or data
`
`SMS-Status-Report
`| Conveying a status reportfromthe SMSC to the MS.
`call. An active MS should be able to send and
`SMS-Command
`receive a short message Transport Protocol Data
`
`Conveying a command from the MS to the SMSC
`Unit (TPDU) at any time regardless of whether
`Table 1. TPDU pypes.
`there is a speech or data call in progress. A confir-
`
`
`Protocol Architecture
`The protocol layer for SMSis shown in Fig. 6. The short mes-
`sage transfer layer (SM-TL) services the short message appli-
`cation layer (SM-AL) and enables it to exchange short
`messages with a peer as well as receive confirmation of recep-
`tion reports from earlier requests.
`
`
`Conveying a failure cause
`
`18
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`SMS-GMSC/
`SMSC
`SMS-IWMSC
`
`
`
`
`
`
`
`
`
`MSC > MS
`
`
`
`
`
`
`
`
`
`y
`
`SM-TL
`
`
`SM-TL
`
`
`
`
`
`
`SM-LL
`
`SM-LL
`
`SM-RL +
`
`
`
`
`
`<«—>| SM
`
`SM-LL
`
`
`
`
`
`element data (IED) that follows. Each of
`these fields is 1 octet long.
`
`pt
`SM-AL
`SM-AL
`In the user data, the message can be7bits,
`
`8 bits, or 16 bits. If 7-bit data is used and the
`header does not end on a 7-bit boundary,
`padding bits are used. This is to ensure that
`older mobiles which do not support the TP-UD
`SM-RL
`headercanstill display the message properly.
`SM-RL SM-RL-ss[ngp———»|_— jg¢————|_
`
`Using the IE] allows sending and receiving
`of concatenated short messages. The IED field
`contains all the necessary information for the
`receiving entity to reassemble the messages in
`the correct order, and is coded as follows:
`¢ First octet: short message reference num-
`ber identifying the message within the same
`transaction
`* Second octet: specifies the maximum numberof short mes-
`sages in the concatenated short message, which will not
`exceed 255
`¢ Third octet: identifies the sequence number of the short
`message within the concatenated message
`The minimum header length for concatenated messageis 7
`octets for 8-bit and 16-bit data and 8 for 7-bit data; leaving 133
`(140 - 7), 152 (160 — 8), and 66 ((140 - 7)/2) characters for the
`short message. The maximum length of the message is then
`increased to 38,760 (255*152), 33,915 (255*133), or 16,830
`(255*66) depending on the character coding scheme used.
`
`
`Mf Figure 6. The protocollayerfor SMS point-to-point.
`
`The SM-TL exchanges PDUs with its peer entity. The
`short message relay layer (SM-RL) conveys the PDUsvia the
`short message link layer (SM-LL). Refer to GSM 03.40 [2] for
`further details.
`
`SMSProtocol Data Unit Types
`There are six types of TPDU at the SM-TL,as listed in Table
`1. The elements of the SMS-Deliver and SMS-Submit TPDU
`are shown in Fig. 7 [2]. The main fields of the TPDU are
`described in this document however for a complete descrip-
`tion of the TPDU please refer to GSM 03.40[2].
`TP-Data-Coding-Scheme
`The data coding schemefield (TP-DCS) is used to iden-
`tify the coding scheme used by the user data, which can
`be 7- or 8-bit or even Unicode [6], as defined in GSM
`03.38[7].
`
`TP-Validity-Period
`The TP-VP field contains an information element
`enabling an MS to specify a validity period for the short
`messageit is submitting. The value specifies how long an
`SMSC will guarantee the existence of a short message
`before delivery to the recipient has been carried out.
`TP-More-Message-lo-Send
`_ The SMSC uses the TP-MMSfield to inform the MS that
`one or more short messages are waiting to be delivered.
`
`TP-User-Data-Header-Indicator
`The 1-bit TP-UDHIfield indicates whether the TP-UD
`includes an additional header as well as the short message.
`
`
`
`|
`
`
`
`
`
`
`
`TP-message-type-indicator
`
`TP-message-type-indicator
`
`TP-more-message-to-send
`
`TP-reject-duplicate
`
`TP-validity-period format
`
`
`
`TP-reply-path TP-reply-path
`
`
`
`TP-user-data-header-indicator
`
`P-status-report
`
`TP-originating-address
`
`TP-protocol-ID
`
` TP-data-coding-scheme TP-service-center-time-stamp
`
`
` TP-user-data-length
`
` TP-user-data
`
`
`
`TP-user-data-header-indicator
`
`P-message reference
`Lt
`
`TP-destination-address
`
`TP-protocol-ID
`
`TP-data-coding-scheme
`
`TP-validity-period
`
`TP-user-data-length
`
`TP-user-data
`
`$ T
`a T
`
`TP-Protocol Identifier
`The TP-PID is used by the MS or SMSC to identify the
`higher-layer protocol being used for internetworking
`with a certain type of telematic device (Telefax group 3
`or 4, Ermes,etc.)
`TP-User-Data (TP-UD)
`The TP-UDfield is used to carry the short message. It
`can store up to 140 octets of data for point-to-point SMS,
`together with a header depending on the setting of the
`TP-UDHIfield. The amountof space taken by the header
`reduces the amount of data the PDU cancarry. Figure 8
`shows a representation of the layout of the TP-UDfor7-
`and 8-bit data schemes.
`The header hasat least three fields. The first field,
`SMS-submit
`SMS-deliver
`the information element identifier, is used to identify
`
`concatenated short messages. Information data length
`(IDL) is used to indicate the length of the information
`@ Figure 7. An SMS TL-PDU.
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`Octets
`Octets
`
`|
`fey
`en
`
`
`| Total number of octets
`
`
`
`
`
`[tet | [tin|Padding |tea | pa |] eb | SM (7-bit data)
`Septet boundary i
`Length indicator
`
`
`Total numberof septets
`
`Length indicator
`UDL: User data length — 1 octet
`UDHL: User data header length — 1 octet
`IElx: information elementidentifier x — 1 octet
`IELx: Information element length x — 1 octet
`IEDx: Information element data x — 1 ton
`
` Total numberof octets
`
`
`
`
`Faas
`tela
`|
`eda | tb |...
`|
`1EIn
`SM (8-bit data).
`Octet boundary
`
`
`Total numberof octets
` Length indicator
`
`Length indicator
`Mi Figure 8. SMS-TPDUformass for 7-bit and 8-bitdata content.
`
`
`
`
`
`also lead to the short message not being understood and
`being rejected. All the above-mentioned problemscan lead to
`packets getting lost along the way with different conse-
`quences:
`° A negative acknowledgment received by the sender (phone
`displaying “message failed” or a similar message) although
`the short message reachesits destination (loss of packet ‘1)
`* Reception of duplicate short messages by user B (loss of
`packet ‘s or
`‘9)); could also be due to the timeout value
`being set too low in the SMSC
`* Or, in the worst case the message might not be delivered at
`all (loss of packet
`1,
`93), 4, >)
`Evenif Fig. 9 shows the most complicated routing scenario
`there is still much that can go wrong with short message rout-
`ing, and a lot of research is currently underway to overcome
`these.
`
`Short Message Routing Considerations
`In Fig. 9, user A in network @ is sending 2a short message to
`user B in network @ roaming in network (1). User A is using
`the SMSC in network \) to submithis shortmessage [8].
`The local cellular exchange routes the short message in an
`SCCPpacket according to the SMSCglobaltitle as defined by
`the E.164 numbering plan [9]. The SCCP packet is forwarded
`from exchange to exchange until it reaches the destination
`SMSC(1). The routing has to be set up in all the SCCP switches
`along the route for the message to successfully reach the SMSC
`in network ().
`Once the SCCP packet carrying the message arrives at the
`destination SMSC, a confirmation message is sent back to the
`handset using another SCCP packet (2).
`To deliver the short message to user B,