From GSM to LTE-Advanced (eBook)

An Introduction to Mobile Networks and Mobile Broadband

Martin Sauter (Autor)

eBook Download: EPUB

2014 | 1. Auflage
456 Seiten
Wiley (Verlag)
978-1-118-86192-9 (ISBN)

Infos

This revised edition contains not only a technical description of the different wireless systems available today, but also explains the rationale behind the different mechanisms and implementations; not only the 'how' but also the 'why'. Therefore the advantages and also limitations of each technology become apparent.  Offering a solid introduction to major global wireless standards and comparisons of the different wireless technologies and their applications, this edition has been updated to provide the latest directions and activities in 3GPP standardization up to Release 12, and importantly includes a new chapter on Voice over LTE (VoLTE).   There are new sections on Building Blocks Of A Voice Centric Device, Building Blocks Of A Smart Phone, Fast Dormancy, IMS and High-Speed Downlink Packet Access, and Wi-Fi Protected Setup. Other sections have been considerably updated in places reflecting the current state of the technology.

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This revised edition of Communication Systems from GSM to LTE: An Introduction to Mobile Networks and Mobile Broadband Second Edition (Wiley 2010) contains not only a technical description of the different wireless systems available today, but also explains the rationale behind the different mechanisms and implementations; not only the how but also the why . In this way, the advantages and also limitations of each technology become apparent. Offering a solid introduction to major global wireless standards and comparisons of the different wireless technologies and their applications, this edition has been updated to provide the latest directions and activities in 3GPP standardization up to Release 12, and importantly includes a new chapter on Voice over LTE (VoLTE). There are new sections on Building Blocks of a Voice Centric Device, Building Blocks of a Smart Phone, Fast Dormancy, IMS and High-Speed Downlink Packet Access, and Wi-Fi-Protected Setup. Other sections have been considerably updated in places reflecting the current state of the technology. Describes the different systems based on the standards, their practical implementation and design assumptions, and the performance and capacity of each system in practice is analyzed and explained Questions at the end of each chapter and answers on the accompanying website make this book ideal for self-study or as course material

Autor

Martin Sauter works in the telecommunication industry as a thought leader, researcher, book author and blogger and is based in Cologne. His interests are focused on mobile communication networks, multimedia applications and especially the wireless Internet. http://www.wirelessmoves.com

Textauszug

Chapter 1
Global System for Mobile Communications (GSM)

At the beginning of the 1990s, GSM, the Global System for Mobile Communications triggered an unprecedented change in the way people communicate with each other. While earlier analog wireless systems were used by only a few people, GSM is used by over 5 billion subscribers worldwide in 2014. This has mostly been achieved by the steady improvements in all areas of telecommunication technology and the resulting steady price reductions for both infrastructure equipment and mobile devices. This chapter discusses the architecture of this system, which also forms the basis for the packet-switched extension called General Packet Radio Service (GPRS), discussed in Chapter 2, for the Universal Mobile Telecommunications System (UMTS), which is described in Chapter 3 and Long-Term Evolution (LTE), which is discussed in Chapter 4. While the first designs of GSM date back to the middle of the 1980s, GSM is still the most widely used wireless technology worldwide and it is not expected to change any time soon. Despite its age and the evolution toward UMTS and LTE, GSM itself continues to be developed. As shown in this chapter, GSM has been enhanced with many new features in recent years. Therefore, many operators continue to invest in their GSM networks in addition to their UMTS and LTE activities to introduce new functionality and to lower their operational cost.

In addition, it should be mentioned at this point that the industry has standardized on a new solution for voice telephony for LTE that has only little in common with GSM anymore. Although standardization is complete, efforts to roll out the new system are significant, and at the time of writing, there were only few voice-over LTE systems to be found in practice. Current LTE-capable devices thus continue using GSM and UMTS networks for voice telephony with a fallback mechanism.

1.1 Circuit-Switched Data Transmission

Initially, GSM was designed as a circuit-switched system that establishes a direct and exclusive connection between two users on every interface between all network nodes of the system. Section 1.1.1 gives a first overview of this traditional architecture. Over time, this physical circuit switching has been virtualized and many network nodes are connected over IP-based broadband connections today. The reasons for this and further details on virtual circuit switching can be found in Section 1.1.2.

1.1.1 Classic Circuit Switching

The GSM mobile telecommunication network has been designed as a circuit-switched network in a similar way to fixed-line phone networks. At the beginning of a call, the network establishes a direct connection between two parties, which is then used exclusively for this conversation. As shown in Figure 1.1, the switching center uses a switching matrix to connect any originating party to any destination party. Once the connection has been established, the conversation is then transparently transmitted via the switching matrix between the two parties. The switching center only becomes active again to clear the connection in the switching matrix if one of the parties wants to end the call. This approach is identical in both mobile and fixed-line networks. Early fixed-line telecommunication networks were designed only for voice communication, for which an analog connection between the parties was established. In the mid-1980s, analog technology was superseded by digital technology in the switching center. This meant that calls were no longer sent over an analog line from the originator to the terminator. Instead, the switching center digitized the analog signal that it received from the subscribers, which were directly attached to it, and forwarded the digitized signal to the terminating switching center. There, the digital signal was again converted back to an analog signal, which was then sent over the copper cable to the terminating party. In some countries, ISDN (Integrated Services Digital Network) lines were quite popular. With this system, the transmission became fully digital and the conversion back into an analog audio signal was done directly in the phone.

Figure 1.1 Switching matrix in a switching center

GSM reuses much of the fixed-line technology that was already available at the time the standards were created. Thus, existing technologies such as switching centers and long-distance communication equipment were used. The main development for GSM, as shown in Figure 1.2, was the means to wirelessly connect the subscribers to the network. In fixed-line networks, subscriber connectivity is very simple as only two dedicated wires are necessary per user. In a GSM network, however, the subscribers are mobile and can change their location at any time. Thus, it is not possible to use the same input and output in the switching matrix for a user for each call as is the case in fixed-line networks.

Figure 1.2 Necessary software changes to adapt a fixed-line switching center for a wireless network

As a mobile network consists of many switching centers, with each covering a certain geographical area, it is not even possible to predict in advance which switching center a call should be forwarded to for a certain subscriber. This means that the software for subscriber management and routing of calls of fixed-line networks cannot be used for GSM. Instead of a static call-routing mechanism, a flexible mobility management architecture became necessary in the core network, which needed to be aware of the current location of the subscriber and was thus able to route calls to the subscriber at any time.

It was also necessary to be able to flexibly change the routing of an ongoing call as a subscriber can roam freely and thus might leave the coverage area of the radio transmitter of the network over which the call was established. While there was a big difference in the software of a fixed and a Mobile Switching Center (MSC), the hardware as well as the lower layers of the software which are responsible, for example, for the handling of the switching matrix were mostly identical. Therefore, most telecommunication equipment vendors like Ericsson, Nokia Solutions and Networks, Huawei and Alcatel-Lucent offered their switching center hardware both for fixed-line and mobile networks. Only the software in the switching center decided if the hardware was used in a fixed or mobile network (see Figure 1.2).

1.1.2 Virtual Circuit Switching over IP

While in the 1990s voice calls were the dominating form of communication, this has significantly changed today with the rise of the Internet. While voice calls still remain important, other forms of communication such as e-mail, instant messaging (IM), social networks (e.g. Facebook), blogs, wikis and many more play an even bigger role. All these services share the Internet Protocol (IP) as a transport protocol and globally connect people via the Internet.

While circuit switching establishes an exclusive channel between two parties, the Internet is based on transferring individual data packets. A link with a high bandwidth is used to transfer the packets of many users. By using the destination address contained in each packet, each network node that the packet traverses decides over which outgoing link to forward the packet. Further details can be found in Chapter 2.

Owing to the rise of the Internet and IP-based applications, network operators thus had to maintain two separate networks: a circuit-switched network for voice calls and a packet-switched network for Internet-based services.

As the simultaneous operation of two different networks is very inefficient and costly, most network operators have, in the meantime, replaced the switching matrix in the MSC with a device referred to as media gateway. This allows them to virtualize circuit switching and to transfer voice calls over IP packets. The physical presence of a circuit-switched infrastructure is thus no longer necessary and the network operator can concentrate on maintaining and expanding a single IP-based network. This approach has been standardized under the name ‘Bearer-Independent Core Network’ (BICN).

The basic operation of GSM is not changed by this virtualization. The main differences can be found in the lower protocol levels for call signaling and voice call transmission. This will be looked at in more detail in the remainder of this chapter.

The trend toward IP-based communication can also be observed in the GSM radio network, even though it is still dominated today by classic circuit-switched technology. This is due to the wide distribution of the network that makes it difficult to change transport technology quickly and because the datarates required for GSM are low.

The air interface between the mobile devices and the network is not affected by the transition from circuit to packet switching. For mobile devices, it is therefore completely transparent if the network uses classic or virtual circuit switching.

1.2 Standards

As many telecom companies compete globally for orders of telecommunication network operators, standardization of interfaces and procedures is necessary. Without standards, which are defined by the International Telecommunication Union (ITU), it would not be possible to make phone calls internationally and network operators would be bound to the supplier they initially select for the delivery of their network components. One of the most important ITU standards discussed in Section 1.4 is the Signaling System Number 7 (SS-7), which is used for call routing. Many ITU standards,...

Produkt-Details

• Erscheint lt. Verlag: 23.6.2014
• Sprache: englisch
• Themenwelt: Mathematik / Informatik ► Informatik ► Netzwerke
• Themenwelt: Technik ► Elektrotechnik / Energietechnik
• Themenwelt: Technik ► Nachrichtentechnik
• Schlagworte: Communication Technology - Networks • Drahtlose Kommunikation • Electrical & Electronics Engineering • Elektrotechnik u. Elektronik • Kommunikationsnetze • Mobile & Wireless Communications
• ISBN-10: 1-118-86192-2 / 1118861922
• ISBN-13: 978-1-118-86192-9 / 9781118861929