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`113712—9916
`Received on: me—eewammo
`IEEE personal communication
`V_
`a publication of the IEEE
`3
`no.
`Jun ammo ommunlcations Society in
`
`IBM EX. 1016
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`IBM EX. 1016
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`EDITOR’S NOTE
`
`-his issue ofIEEE Personal Com-
`munications contains several articles in the
`areas of mobile and wireless services, wire—
`less systems and standards, and issues relat-
`ed to wireless links and channel models.
`
`The first article, by Y. Lin, H. Rao, and
`M. Chang, offers an overview of mobile pre-
`paid services and how such services can be pro-
`vided in a wireless network. It covers a
`
`
`
`number of example scenarios as well as
`issues such as billing and subscriber call
`management with respect to prepaid ser—
`vices. Moreover, this article discusses the
`network elements and architectural compo-
`nents for prepaid services. Finally, the
`authors provide a comparison between different prepaid
`solutions based on scalability, fraud risk, system manage-
`ment issues, and service features.
`
`MAHMOUD
`
`NAGHSHINEH
`
`work building blocks, and then puts empha-
`sis on the SMS network and protocol
`architecturewithin the GSM framework. Next,
`an overview of the most widely used messag—
`ing protocols is provided, and finally, a sum—
`mary of current and future issues in this
`area is presented.
`Our next article is authored by D. Koulaki—
`otis and A. Aghvami, and reviews data detection tech-
`niques for direct sequence code-division multiple access
`(DS-CDMA) mobile systems. The authors start by provid-
`
`Director of Ma alines
`
`Mark J, Karol, Lucent Tec nologies, USA
`Editorrin~Chief
`Mahmoud Naghshineh, IBM Research, USA
`Senior Advisors
`Hamid Ahmadi, AT&T Labs, USA
`Thomas F. La Porta, Lucent Technologies, USA
`Advisory Board
`Donald Cox, Stanford University, USA
`David Goodman, Rutgers University, USA
`Jorma Lilleberg, Nokia, Finland
`Kaveh Pahlavan, Worcester Polytechnic
`Institute, USA
`Mahadev Satyanarayanan, CMU, USA
`IEEE Vehicular Technology Liaison
`Theodore Rappaport, Virginia Tech, USA
`
`
`
`
`Our second article is a tutorial on GSM short
`
`message services (SMS). This article is
`authored by G. Peersman, S. OIetkovic, P. Grif-
`fiths, and H.Spaer, and presents a discussion
`on SMS integration with existing messaging
`services and its relation to TCP/IP. This
`tutorial startswith a brief overview of GSM net-
`
`IEEE Personal Communications — The Maga—
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`
`IlPersonal
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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 networks the ability to exchange alphanumeric messages up to the limit of 160 characters.
`The tutorial is motivated by an acute absence of research publications in this field. The information gathered in the tutorial was required
`considering the increasing potential SMS offers for integration with existing messaging services and its 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 7 the mobile station, base station, and network subsystem — and then emphasizes the
`SMS network and protocol architecture. The most widely used protocols for message submission are then introduced (text-based, SMSZOOO,
`ETSI 0705, TAP) and compared in terms of features provided and flexibility to handle extended alphabets or two-way messaging. Finally the
`tutorial outlines a summary of current and future issues for further development and research in 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.
`
`since the first Global System
`for Mobile Communications (GSM) network started opera-
`tion in 1991, more than 100 countries have adopted the stan—
`dard. Over 20 million subscribers of GSM networks are now
`offered worldwide coverage, outstanding voice quality over a
`whole range of operating conditions, and a variety of value-
`added services. These services include voice mail, call han-
`dling facilities, call line identification, and Short Message
`Service (SMS).
`With SMS, users are able to exchange alphanumeric mes—
`sages (up to 160 characters) with other users of digital cellular
`networks, almost anywhere in the world, within seconds of
`submission. Even if the service was originally conceived as a
`paging mechanism for notifying the users of voicemail mes-
`sages, SMS is now increasingly used as a messaging service.
`The messages are typically created on mobile phone keypads,
`which is somewhat awkward. Fortunately, there are other
`ways to access the message centers, as discussed in this article.
`Numerous applications are already available and make short
`message reception and submission possible using a computer.
`Gateway architectures are also being widely implemented and
`connect company’s e-mail or voicemail systems to the SMS.
`The practical implementation of SMS and the different
`protocols for message submission are addressed in this article.
`The future of SMS and a brief review of the fields currently
`being studied will conclude this article.
`
`to send and/or receive alphanumeric messages. The short
`messages can be up to 140 bytes in length, and are delivered
`within a few seconds where GSM coverage is available. More
`than a common paging service, the delivery of the message is
`guaranteed even when the cellular terminal is unavailable
`(e.g., when it is switched off or outside. the coverage area).
`The network will hold the message and deliver it shortly after
`the cellular terminal announces its presence on the network.
`The fact that SMS (through GSM) supports international
`roaming with very low latency makes it particularly suitable
`for applications such as paging, e-mail, and voice mail notifi-
`cation, and messaging services for multiple users. However,
`the facilities offered to users and the charges for these facili-
`ties still mainly depend on the level of service provided by the
`network operator.
`There are two types of SMS available: cell broadcast [1]
`and point—to-point [2]. In cell broadcast, a message is trans-
`mitted to all the active handsets or mobile stations (MSs) pre-
`sent in a cell that have the capability of receiving short
`messages and have subscribed to this particular information
`service. This service is only one-way, and no confirmation of
`receipt will be sent. It can send up to 93 7-bit character or 82
`8-bit characters, typically used to transmit messages about
`traffic conditions, weather forecast, stock market, and so on.
`In point-to-point service, messages can be sent from one
`mobile to another or from a PC to a mobile and vice versa.
`These messages are maintained and transmitted by an SMS
`Center (SMSC). The SMSC is an electronic form of ordinary
`The Short Message Service
`mail postal service that stores and then forwards the messages
`when they can be delivered. Each GSM network must support
`Developed as part of the GSM Phase 2 specification, the
`one or more SMSCs to sort and route the messages. Each
`Short Message Service, or SMS as it is more commonly
`SMSC checks, organizes, and sends the message to the opera-
`known, is based on the capability of a digital cellular terminal
`
`
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`Mobile equipment
`
`Base transceiver station
`Base station controller
`Subscriber identity module
`
`lxrllllll
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` Igure e aszc c nerwor arc ttecture.
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`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 SMS to 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
`
`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.
`
`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 BSC is
`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.
`PSTN or 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
`lular phone allows the user to access a network, make and
`(HLR) and visitor location register (VLR) together with the
`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 MS is in the form of a Mobile Station Roaming Number
`national Mobile Subscriber Identity (IMSI) contained in the
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`protocol architecture.
`
`
` tion over the radio link to transmit
`
`
`
`(MSRN), typically the SS7 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 VLR is 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) contains a list
`of each MS IMEI allowed on the network. The authentication
`center (AuC) database contains each single PIN stored in the
`MS SIM.
`
`Figure 3. The SS 7 protocol stack.
`
`call-related signaling information such
`as the establishment of the signaling
`and traffic channel between the MS
`and the B88.
`On the MSC side, 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
`entities of a GSM network is handled through the protocol
`Mobile Application Part (MAP), Transaction Capability
`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 protocol stack.
`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 international tele-
`straints set by the radio path. On the MS side, the message
`phone calls. The TCAP is an application layer protocol. It
`layer consists of three sublayers: connection management
`allows an application at one node to invoke an execution of a
`(CM), mobility management (MM), and resource manage-
`ment (RR). The CM sublayer manages call-related supple-
`procedure at another node and exchange the results of such
`invocation. It isolates the user application from the complexity
`mentary services, SMS, and call-independent supplementary I
`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
`updating, IMSI management, and Temporary Mobile Sub-
`uses the TCAP services to provide the signaling capabilities
`required to support the mobile capabilities.
`scriber Identity (TMSI) identification, authentication, and
`The MTP and SCCP (Fig. 4) correspond to the lower three
`reallocation. The RR sublayer establishes the physical connec-
`
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`TCAP/lSUP/TUP
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`mation will always be returned to the SMSC
`indicating whether the MS has received the short
`message or not. A confirmation will also be
`returned to the MS from an SMSC indicating
`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 3" SMSC Messages can
`also be stored on the SIM, which can be
`retrieved at a later time. When the 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.
`
`
`
`The 5M5 Basic Network Architecture
`The main components of the SMS network archi-
`tecture are shown in 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 SMSC identifies each short message unique-
`ly by adding a time stamp in the SMS-DELIVER
`TP-SCTS field. The short message arrival at the
`SMSC is accurate to the second. It is the SMSC’s
`responsibility to assure that if two or more short
`message arrive within the same second their time-stamps will 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.
`
`I Figure 4. The SC‘CF and MTP sublayersii
`
`
`SMSC
`
`
`
`SMS—GMSC/
`SMS-IWMSC
`
`<—>
`
`MSC
`
`
`
`
`
`
`M5
`
`HLR
`
`VLR
`
`
`
`. Figure 5. The SMS network architecture.
`
`
`
`layers of the open system interconnection (051) model (Fig. 4).
`The SCCP sublayer supports connectionless and connection-
`oriented services to transfer data and Global Title Translation
`(GT'T) above MTP level 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:
`' MTP level 1 defines the characteristics of the digital signal-
`ing link and is equivalent to the OSI physical layer.
`0 MTP level 2 is equivalent to the 051 data link layer and
`provides a reliable sequenced delivery of data packets
`across MTP level 1.
`° MTP level 3 provides congestion control, signaling manage-
`ment, and message discrimination, distribution,
`and routing in a similar way as the OSI network
`layer.
`
`Protocol Architecture
`The protocol layer for SMS is 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.
`
` SMS~Deliver
`Conveying-a short message-"from the SMSC'to the MS 1
`
`SMS-Deliver-Report
`Conveying a failure cause
`: Conveying a short messagefrom theMS to the SMSC
`
`SMS-Su bmit—Report
`Conveying a failure cause
`
`
`
`SMS-Statusv-Report
`I,Conveying.a statth repel-Ureth SMSC to the MS:
`SMS-Command
`Conveying a command from the MS to the SMSC
`
`
`
`
`
`
`sM‘si'Submit
`
`Practical Implementation
`SMS uses the SS7 signaling channel to transmit the
`data packet [5], thus allowing a text message to be
`received when the user is making a voice or data
`call. An active MS should be able to send and
`receive a short message Transport Protocol Data
`Unit (TPDU) at any time regardless of whether
`there is a speech or data call in progress. A confir-
`I Table I. TPDU types.
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`SMS-GMSC/
`SMS-IWMSC
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` element data (IED) that follows. Each of
`
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`these fields is 1 octet long.
`In the user data, the message can be 7 bits,
`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
`header can still display the message properly.
`Using the IE1 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
`0 Second octet: specifies the maximum number of 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 message is 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.
`
`I Figure 6. The protocol layerfor SMS point-to-point.
`
`The SM-TL exchanges PDUs with its peer entity. The
`short message relay layer (SM-RL) conveys the PDUs via the
`short message link layer (SM-LL). Refer to GSM 03.40 [2] for
`further details.
`
`5M5 Protocol 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 scheme field (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
`message it 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—To-Send
`, The SMSC uses the TP—MMS field to inform the MS that
`one or more short messages are waiting to be delivered.
`
`TP—User—Data—Header-Indicator
`The 1-bit TP-UDHI field indicates whether the TP-UD
`includes an additional header as well as the short message.
`
`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.)
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`TP-message—type-indicator
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`TP—message-type—indicator
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`TP-reject—duplicate
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`TP—more-message—to—send
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`TP-validity-period format
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`
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`TP—reply-path TP—reply-path
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`TP-user-data-header—indicator
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`TP—user-data-header-indicator
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`TP-status-report
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`TP—message reference
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`TP-originating-address
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`TP-destination-address
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`TP~protocol-ID
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`TP-protocoI-ID
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`TP-data-coding-scheme
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`TP—data-coding-scheme
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`TP~se Nice-center-time—sta mp
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`TP-validity-period
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`TP—user-data
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`TP-User—Dato (TP—UD)
`The TP-UD field 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-UDHI field. The amount of space taken by the header
`reduces the amount of data the PDU can carry. Figure 8
`shows a representation of the layout of the TP—UD for 7—
`and 8—bit data schemes.
`The header has at least three fields. The first field,
`the information element identifier, is used to identify
`concatenated short messages. Information data length
`(IDL) is used to indicate the length of the information
`IFigure 7.An SMS TL-PDU.
`
`TP-user—data-length
`
`TP-user-data—Iength
`
`TP-user-data
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`of octets
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`Septet boundary
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`Total number of septets
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`
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`Octet boundary
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`Total number of octets
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`I Figure 8. SMS-TPDUformats for 7-bit and 8-bit data content.
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`Short Message Routing Considerations
`
`'
`
`hort message to
`In Fig. 9, user A in network A '
`v.1 . User A is using
`user B in network (9:?
`min
`the SMSC in network
`to submit his short message [8].
`The local cellular exchange routes the short message in an
`SCCP packet according to the SMSC global title as defined by
`the E.164 numbering plan [9]. The SCCP packet is forwarded
`from exch
`exchange until it reaches the destination
`SMSC (1).
`ting has to be set up in all the SCCP switches
`along the r
`the message to successfully reach the SMSC
`in network .V .
`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, the SMSC has to
`access the HLR database of his home network. A location
`request SCCP packet, based on user B’s mobile number, is
`sent by the SMSC (3).
`This international SCCP network then routes the location
`request SCCP packet to the appropriate HLR. When the
`HLR receives the request, it will return the location informa-
`tion in another SCCP packet to the SMSC (4).
`The SMSC then sends the message to the VMSC of user
`B, based on the information received from the HLR (5).
`Finally, this VMSC interrogates the VLR (6, 7), and delivers
`the message to user B (8). Upon successful delivery a confir—
`mation SCCP packet is sent back to the SMSC (9).
`Throughout these routing procedures, the SCCP packets
`Block Mode
`can get lost if one of the cellular exchanges along the route
`does not know where to forward the SCCP packet. SCCP
`The block mode is a binary protocol which encapsulates the
`SMS PDU used for short message transfer between an MS
`routing is based on the global title used for switches and the
`SMSC. The routing information has to be in place in the
`and the SMSC defined in GSM 03.40 [2]. This protocol
`includes error detection and is suitable for use where the
`international SCCP transit Switches for the messages to suc-
`cessfully reach their destination. Some international switches
`link between the application and the phone is subject to
`errors. It will be of particular use where control of remote
`only check the country code prefix (e.g., 44 for the United
`Kingdom) and forward the packet to the next exchange, while
`devices is required. The application has to construct a bina-
`others also check for the network prefix (e.g., 447976 for
`ry string including a header and the short message PDU
`Orange). If the exchange routing table does not include all
`(SMS-TPDU).
`the prefixes allocated to the subscribers, some messages will
`Once the application has requested the phone to enter
`
`block mod