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Building on the success of the first edition, Mobile Messaging Technologies and Services offers extensive new and revised material based upon the latest research and industry developments. While early implementations targeted person-to-person messaging, MMS has now evolved to facilitate such requirements as the mass delivery of time-sensitive messages for content-to-person messaging. This Second Edition exploits the technical maturity of MMS as it is poised to generate a wealth of new business opportunities across the mobile communications sector. The author provides the fundamental technical background required for SMS, EMS and MMS, and supports this with industry cutting-edge developments.
● Contains a revised section on the fundamentals of MMS, including an updated section on GPRS to explain current commercial implementations such as GRX applications.
● Presents the latest developments in MMS standardization, including the design of synchronized multimedia integration language (SMIL) presentations, Digital Rights Management (DRM), transcoding techniques, postcard service and support of advanced multimedia formats.
● Describes the processes for standardizing telecommunications services and technologies (3GPP, OMA, GSM Association, IETF and W3C).
● Provides updated sections on SMS, EMS and heavily revised coverage of the developments in MMS, including MMS interworking and the forthcoming MMS version 1.3.
This resource will be invaluable for application developers, manufacturers, operators and content providers involved in the design and deployment of messaging services. It will also be of interest to practitioners involved in the process of standardizing telecommunications services and technologies. Postgraduate students and researchers will benefit from having access to state-of-the-art findings backed by numerous illustrative real-world examples.
Includes a companion website featuring information on relevant standards, available phones and developers’ resources.
This chapter outlines the basic concepts of mobile communications systems and presents the required background information necessary for a clear understanding of this book. First, an overview of the evolution of mobile communications systems is provided. This encompasses the introduction of first generation analog systems supporting only voice communications to the recent deployment of third generation systems supporting voice and multimedia services. The Global System for Mobile Communication, commonly known as GSM, has been a major breakthrough in the domain of mobile communications. Elements composing a typical GSM network are presented. Another important milestone is the introduction of the General Packet Radio Service (GPRS) allowing the support of packet-based communications in evolved GSM networks. The architecture of a GPRS network is presented. Recently deployed are Universal Mobile Telecommunications Systems (UMTS). These systems support advanced multimedia services requiring high data rates. UMTS services and supporting technologies are also introduced in this chapter. Additionally, the Wireless Application Protocol (WAP) is described. WAP is an enabling technology for developing services such as browsing and multimedia messaging. An overview of latest digital rights management methods is also provided. The last section of this chapter provides pointers to books and reference articles for anybody wishing to further explore the topics covered in this chapter.
1.1 Generations of Mobile Communications Networks
In France, in 1956, a very basic mobile telephony network was implemented with vacuum electronic tubes and electron-mechanical logic circuitry. These devices used for wireless communications had to be carried in car boots. In these early days of mobile telephony, service access was far from being ubiquitous and was reserved for a very limited portion of the population. Since the introduction of this experimental network, mobile communications technologies benefited from major breakthroughs commonly categorized in three generations. In the 1980s, first generation (1G) mobile systems arrived in Nordic countries. These first generation systems were characterized by analog wireless communications and limited support for user mobility.
Digital communications technology was introduced with second generation (2G) mobile systems in the 1990s. Second generation systems are characterized by the provision of better quality voice services available to the mass market. Second generation systems benefited from the cellular concept in which scarce radio resources are used simultaneously by several mobile users without interference. The best known 2G system is the Global System for Mobile Communication (GSM) with the billionth GSM user connected in the first quarter of 2004. Other major 2G systems include cdmaOne (based on CDMA technology), with users in the Americas and Asia, and Japanese Personal Data Cellular (PDC) with the iMode technology for mobile Internet.
Early 2004, first third generation (3G) mobile systems have been deployed in several European countries. With 3G systems, various wireless technologies converge with Internet technologies. Third generation services encompass a wide range of multimedia and cost-effective services with support for worldwide user mobility. The migration to 3G systems is facilitated by the introduction of intermediary evolved 2G systems, also known as 2.5G systems.
1.2 Telecommunications Context: Standardization and Regulation
In the telecommunications environment, Standard Development Organizations (SDOs) provide the necessary framework for the development of standards. These standards are technical documents defining or identifying the technologies enabling the realization of telecommunication network technologies and services. The prime objective of SDOs is to develop and maintain widely accepted standards allowing the introduction of attractive services over interoperable networks. The actors that are involved in the standardization process are network operators, manufacturers, and third party organizations such as content providers, equipment testers, and regulatory authorities. One of the main objectives of telecommunications regulation authorities is to ensure that the telecommunications environment is organized in a sufficiently competitive environment and that the quality of service offered to subscribers is satisfactory.
In the early days of mobile communications, various regional SDOs developed specifications for network technologies and services independently. This led to the development of heterogeneous networks where interoperability was seldom ensured. The lack of interoperability of first generation mobile systems prevented the expansion of a global international mobile network that would have certainly greatly improved user experience. With second and third generations systems, major SDOs decided to gather their efforts in order to ensure that mobile communication networks will appropriately interoperate in various regions of the world. In 1998, such an effort was initiated by several SDOs including ARIB (Japan), ETSI (Europe), TTA (Korea), TTC (Japan), and T1 (USA). The initiative was named the Third Generation Partnership Project (3GPP). The 3GPP standardization process is presented in Chapter 2.
1.3 Global System for Mobile Communication
Before the introduction of the Global System for Mobile Communication (GSM), mobile networks implemented in different countries were usually incompatible. This incompatibility made impracticable the roaming of mobile users across international borders. In order to get around this system incompatibility, the Conference Europeenne des Postes et Telecommunications (CEPT) created the Groupe Special Mobile1 committee in 1982. The main task of the committee was to standardize a pan-European cellular public communication network in the 900 MHz radio band. In 1989, the European Telecommunications Standard Institute (ETSI) took over the responsibility for the maintenance and evolution of GSM specifications. In 2000, this responsibility was transferred to 3GPP. The initiative was so successful that networks compliant with the GSM standard have now been developed worldwide. Variations of the GSM specification have been standardized for the 1800 and 1900 MHz bands and are known as DCS 1800 and PCS 1900, respectively. In March 2004, the GSM association2 reported a total number of 1046.8 million subscribers distributed over 207 countries.
A GSM network is characterized by digital voice communications and support of low-rate data services. The GSM air interface is based on Time Division Multiple Access (TDMA). With TDMA, a radio band is shared by multiple subscribers by allocating one or more timeslots on given radio carriers to each subscriber. With GSM, the transfer of data can be carried out over circuit-switched connections. For these data communications, bit rates up to 14.4 Kbps can be achieved on single-slot connections. The single-slot configuration is called Circuit Switched Data (CSD). Higher bit rates up to 57.6 Kbps can be attained by allocating more than one slot for a data connection. This multi-slot configuration is called High Speed CSD (HSCSD).
One of the most popular GSM services is the Short Message Service (SMS). This service allows SMS subscribers to exchange short text messages. An in-depth description of this service is provided in Chapter 3. An application-level extension of SMS in the form of the Enhanced Messaging Service (EMS) is presented in Chapter 4.
1.3.1 Cellular Concept
Radio bands available for wireless communications in mobile networks represent very scarce resources. In order to efficiently use these resources, GSM networks are based on the cellular concept. With this concept, the same radio resources (characterized by a frequency band and a timeslot) can be utilized simultaneously by several subscribers without interference if they are separated by a minimum distance. The minimum distance between two subscribers depends on the way radio waves propagate in the environment where the two subscribers are located (e.g., presence of buildings, etc.). In a GSM network, the smaller the cells, the higher is the frequency reuse factor, as shown in Figure 1.1.
In a GSM network, a fixed base station transceiver manages the radio communications for all mobile stations located in a cell. Each geometrical cell in Figure 1.1 represents the radio coverage of one single base station.
1.3.2 GSM Architecture
The main elements of the GSM architecture [3GPP-23.002] are shown in Figure 1.2. The GSM network is composed of three subsystems: the Base Station Subsystem (BSS), the Network Subsystem (NSS), and the Operation Subsystem (OSS). The OSS implements functions that allow the administration of the mobile network. For the sake of clarity, elements of the OSS are not represented in the GSM architecture shown in Figure 1.2. Elements of the BSS and NSS are further described in the following sections.
1.3.3 Mobile Station
The Mobile Station (MS) is a device that transmits and receives radio signals within a cell site. A mobile station can be a basic mobile handset, as shown in Figure 1.3, or a more complex Personal Digital Assistant (PDA). Mobile handset capabilities include voice communications, messaging features, and phone book management. In addition to these basic capabilities, a PDA is usually shipped with an Internet microbrowser and an advanced Personal Information Manager (PIM) for managing contacts and calendaring/scheduling entries. When the user is moving (i.e., while driving), network control of MS connections is switched over from cell site to cell site to support MS mobility. This process is called handover.
The mobile station is composed of the Mobile Equipment (ME) and the Subscriber Identity Module (SIM). The unique International Mobile Equipment Identity (IMEI) stored in the ME identifies uniquely the device when attached to the mobile network.
The SIM is usually provided by the network operator to the subscriber in the form of a smart card. The microchip is often taken out of the smart card and directly inserted into a dedicated slot in the mobile equipment. A SIM microchip is shown in Figure 1.4.
Today's mobile stations can be connected to an external device such as a PDA or a personal computer. Such an external device is named a Terminal Equipment (TE) in the GSM architecture.
A short message is typically stored in the mobile station. Most handsets have SIM storage capacities. High-end products sometimes complement the SIM storage capacity with additional storage in the mobile equipment itself (e.g., flash memory). It is now common to find handsets shipped with a PIM. The PIM is usually implemented as an ME internal feature and enables elements such as calendar entries, memos, phonebook entries, and of course messages to be stored in the ME. These elements are managed, by the subscriber, with a suitable graphical user interface. These PIM elements remain in the PIM even when the SIM is removed from the mobile handset. Alternatively, simple elements such as short messages and phonebook entries can be directly stored in the SIM. A SIM can contain from 10 short messages to 50 short messages on high-end solutions. Storing elements in the SIM allows messages to be retrieved from any handset simply by inserting the SIM in the desired handset. The benefit of storing messages in the ME is that the ME storage capacity is often significantly larger than the SIM storage capacity.
1.3.4 Base Transceiver Station
The Base Transceiver Station (BTS) implements the air communications interface with all active MSs located under its coverage area (cell site). This includes signal modulation/ demodulation, signal equalizing, and error coding. Several BTSs are connected to a single Base Station Controller (BSC). In the United Kingdom, the number of GSM BTSs is estimated around several thousands. Cell radii range from 10 to 200 m for the smallest cells to several kilometers for the largest cells. A BTS is typically capable of handling 20-40 simultaneous communications.
1.3.5 Base Station Controller
The BSC supplies a set of functions for managing connections of BTSs under its control. Functions enable operations such as handover, cell site configuration, management of radio resources, and tuning of BTS radio frequency power levels. In addition, the BSC realizes a first concentration of circuits towards the MSC. In a typical GSM network, the BSC controls over 70 BTSs.
1.3.6 Mobile Switching Center and Visitor Location Register
The Mobile Switching Center (MSC) performs the communications switching functions of the system and is responsible for call set-up, release, and routing. It also provides functions for service billing and for interfacing other networks.
The Visitor Location Register (VLR) contains dynamic information about users who are attached to the mobile network including the user's geographical location. The VLR is usually integrated to the MSC.
Through the MSC, the mobile network communicates with other networks such as the Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN), Circuit Switched Public Data Network (CSPDN), and Packet Switched Public Data Network (PSPDN).
1.3.7 Home Location Register
The Home Location Register (HLR) is a network element containing subscription details for each subscriber. An HLR is typically capable of managing information for hundreds of thousands of subscribers.
In a GSM network, signaling is based on the Signaling System Number 7 (SS7) protocol. The use of SS7 is complemented by the use of the Mobile Application Part (MAP) protocol for mobile specific signaling. In particular, MAP is used for the exchange of location and subscriber information between the HLR and other network elements such as the MSC. For each subscriber, the HLR maintains the mapping between the International Mobile Subscriber Identity (IMSI) and the Mobile Station ISDN Number (MSISDN).
For security reasons, the IMSI is seldom transmitted over the air interface and is only known within a given GSM network. The IMSI is constructed according to [ITU-E.212] format. Unlike the IMSI, the MSISDN identifies a subscriber outside the GSM network. The MSISDN is constructed according to [ITU-E.164] format (e.g., +33612345678 for a French mobile subscriber).
1.4 General Packet Radio Service
In its simplest form, GSM manages voice and data communications over circuit-switched connections. The General Packet Radio Service (GPRS) is an extension of GSM which allows subscribers to send and receive data over packet-switched connections. The use of GPRS is particularly appropriate for applications with the following characteristics:
bursty transmission (for which the time between successive transmissions greatly exceeds the average transfer delay);
frequent transmission of small volumes of data;
infrequent transmission of large volumes of data.
These applications do not usually need to communicate permanently. Consequently, the continuous reservation of resources for realizing a circuit-switched connection does not represent an efficient way to exploit scarce radio resources. The basic concept behind the GPRS packet-based transmission lies in its ability to allow selected applications to share radio resources by allocating radio resources for transmission only when applications have data to transmit. Once the data have been transmitted by an application, radio resources are released for use by other applications. Scarce radio resources are used more efficiently with this mechanism. GPRS allows more radio resources to be allocated to a packet-based connection than to a circuit-switched connection in GSM. Consequently, a packet-based connection usually achieves higher bit rates (up to 171.2 Kbps) by using a multislot configuration for uplinks and downlinks as shown in Table 1.1. For instance, a mobile station of multislot GPRS class 6 can have a maximum of three slots allocated to the downlink and a maximum of two slots allocated to the uplink. However, for such a mobile station, a maximum of four slots only can be active at a time for both uplink and downlink. The capacity of each slot depends on the channel encoding used. Four channel encoding schemes are available in GPRS with distinct levels of error protection and are typically selected according to the quality of the radio environment. GPRS can offer "always on" connections (sending or receiving data at any time).
Excerpted from Mobile Messaging Technologies and Services by Gwenael Le Bodic Copyright © 2005 by John Wiley & Sons, Ltd . Excerpted by permission.
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About the Author.
1 Basic Concepts.
1.1 Generations of Mobile Communications Networks.
1.2 Telecommunications Context: Standardization andRegulation.
1.3 Global System for Mobile Communication.
1.4 General Packet Radio Service.
1.5 Universal Mobile Telecommunications System.
1.6 Wireless Application Protocol.
2.1 Messaging Roadmap.
2.2 MMS Standards.
2.3 Third Generation Partnership Project.
2.4 Third Generation Partnership Project 2.
2.5 GSM Association.
2.6 Internet Engineering Task Force.
2.7 World Wide Web Consortium.
2.8 WAP Forum.
2.9 Open Mobile Alliance.
2.10 Further Reading.
3 Short Message Service.
3.1 Service Description.
3.2 SMS Use Cases.
3.3 Architecture for GSM Networks.
3.4 SMS Basic Features.
3.5 Technical Specification Synopsis.
3.6 Protocol Layers.
3.7 Structure of a Message Segment.
3.8 Settings and Message Storage in the SIM.
3.9 Message Submission.9
3.10 Message Submission Report.
3.11 Message Delivery.
3.12 Message Delivery Report.
3.13 Status Report.
3.15 User Data Header and User Data.
3.16 Network Functions for Message Delivery.
3.17 SMSC Access Protocols.
3.18 SIM Application Toolkit.
3.19 SMS and AT Commands.
3.20 SMS and Email Interworking.
3.21 Index of TPDU parameters.
3.22 Pros and Cons of SMS.
3.23 Further Reading.
4 Enhanced Messaging Service.
4.1 Service Description.
4.2 EMS Compatibility with SMS.
4.3 Basic EMS.
4.4 Extended EMS.
4.5 Pros and Cons of EMS.
4.6 Further Reading.
5 Multimedia Messaging Service: Service andArchitecture.
5.1 MMS Success Enablers.
5.2 Commercial Availability of MMS.
5.3 MMS Compared with Other Messaging Services.
5.4 Value Proposition of MMS.
5.5 Billing Models.
5.6 Usage Scenarios.
5.8 Standardization Roadmap for MMS.
5.9 WAP Realizations of MMS.
5.10 Service Features.
5.11 Message Sending.
5.12 Message Retrieval.
5.13 Message Reports.
5.14 Message Forward.
5.15 Reply Charging.
5.16 Addressing Modes.
5.17 Settings of MMS-Capable Devices.
5.18 Storage of MMS Settings and Notifications in the(U)SIM.
5.19 Multimedia Message Boxes.
5.20 Value-Added Services.
5.21 Content Adaptation.
5.23 Charging and Billing.
5.24 Security Considerations.
5.25 Multimedia Message.
5.26 Multipart Structure.
5.27 Message Content Domains and Classes.
5.28 Media Types, Formats, and Codecs.
5.29 Scene Description.
5.30 Example of a Multimedia Message.
5.31 DRM Protection of Media Objects.
5.32 Postcard Service.
5.33 Message Size Measurement.
5.34 Commercial Solutions and Developer Tools.
5.35 The Future of MMS.
5.36 Further Reading.
6 Multimedia Messaging Service, Transactions Flows.
6.1 Introduction to the MMS Transaction Model.
6.2 MM1 Interface, MMS Client–MMSC.
6.3 MM2 Interface, Internal MMSC Interface.
6.4 MM3 Interface, MMSC–External Servers.
6.5 MM4 Interface, MMSC–MMSC.
6.6 MM5 Interface, MMSC–HLR.
6.7 MM6 Interface, MMSC–User Databases.
6.8 MM7 Interface, MMSC–VAS Applications.
6.9 MM8 Interface, MMSC–Post-Processing BillingSystem.
6.10 MM9 Interface, MMSC–Online Charging System.
6.11 MM10 Interface, MMSC–Messaging Service ControlFunction.
6.12 STI and MMS Transcoding.
6.13 Standard Conformance and Interoperability Testing.
6.14 Implementations of Different Versions of the MMSProtocol.
Appendix A: SMS TP-PID Value for Telematic Interworking.
Appendix B: SMS–Numeric and AlphanumericRepresentations.
B.1 Integer Representation.
B.2 Octet Representation.
B.3 Semi-Octet Representation.
Appendix C: SMS–Character Sets and TransformationFormats.
C.1 GSM 7-bit Default Alphabet.
C.3 Universal Character Set.
C.4 UCS Transformation Formats.
Appendix D: EMS–iMelody Grammar.
Appendix E: MMS–Content Types of Media Objects.
Appendix F: MM1 Interface–Response Status Codes(X-Mms-Response-Status).
Appendix G: MM1 Interface–Retrieve Status Codes(X-Mms-Retrieve-Status).
Appendix H: MM1 Interface–MMBox Store Status Codes(X-Mms-Store-Status).
Appendix I: MM4 Interface–Request Status Codes(X-Mms-Request-Status-Code).
Appendix J: MM7 Interface–Status Code and Status Text.
Acronyms and Abbreviations.