Local Services in a Fourth Generation Mobile Network

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LAPPEENRANTA UNIVERSITY OF TECHNOLOGY DEPARTMENT OF INFORMATION TECHNOLOGY

MASTER’S THESIS

LOCAL SERVICES IN A

FOURTH GENERATION MOBILE NETWORK

The council of the Department of Information Technology approved the subject of the thesis on May 20, 2001.

Supervisor and instructor: Professor Olli Martikainen

Lappeenranta, July 9, 2001

Kalle Ikkelä

Korpimaankatu 3 C FIN-53850 Lappeenranta Finland

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ABSTRACT

Author: Ikkelä, Kalle

Subject: Local Services in a Fourth Generation Mobile Network Department: Information technology

Year: 2001

Place: Lappeenranta

Master’s thesis. Lappeenranta University of Technology. 62 pages and 14 figures.

Supervisor: Professor Olli Martikainen

Keywords: 4G, Bluetooth, WLAN, Internet, Local Services

Fourth generation mobile networks gather all telecommunication networks and services under one network: the Internet. This revolution will change the old vertical network model where only a fixed set of services were available to certain terminals into a horizontal model where all terminals use their specific access network to access Internet based services.

This thesis presents the concept of local services in a fourth generation mobile network.

Fourth generation mobile networks combine traditional telecom services with Internet based services and enables new types of services to be created. The evolution of the TCP/IP protocol suite and the Internet is presented. Short-range, broadband wireless access technologies which are used to access the Internet are introduced. The evolution towards a fourth generation mobile network is explained by describing previous, current, and future mobile networks and services. Forecasts about future service development and market predictions are presented.

The architecture of fourth generation mobile networks enable local services available only in one local network. Local services can be customized for each user separately based on user profiles and location. The usability and possibilities of local services are considered using the results of a service pilot realized in Lappeenranta University of Technology’s 4G project.

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TIIVISTELMÄ

Tekijä: Ikkelä, Kalle

Nimi: Paikalliset palvelut neljännen sukupolven mobiiliverkossa Osasto: Tietotekniikan osasto

Vuosi: 2001

Paikka: Lappeenranta

Diplomityö. Lappeenrannan teknillinen korkeakoulu. 62 sivua ja 14 kuvaa.

Tarkastaja: Professori Olli Martikainen

Hakusanat: 4G, Bluetooth, WLAN, Internet, paikalliset palvelut

Neljännen sukupolven mobiiliverkot kokoaa kaikki tietoliikenneverkot ja palvelut Inter- netin ympärille. Tämä mullistus muuttaa vanhat vertikaaliset tietoliikenneverkot joissa yhden tietoliikenneverkon palvelut ovat saatavissa vain kyseisen verkon päätelaitteille ho- risontaaliseksi malliksi jossa päätelaitteet käyttävät omaa verkkoansa pääsynä Internetin palveluihin.

Tämä diplomityö esittelee idean paikallisista palveluista neljännen sukupolven mobiiliverkossa. Neljännen sukupolven mobiiliverkko yhdistää perinteiset televerkkojen palvelut ja Internet palvelut sekä mahdollistaa uuden tyyppisten palveluiden luonnin. TCP/IP protokollien ja Internetin evoluutio on esitelty. Laajakaistaiset, lyhyen kantaman ra- diotekniikat joita käytetään langattomana yhteytenä Internetiin on käsitelty. Evoluutio kohti neljännen sukupolven mobiiliverkkoja on kuvattu esittelemällä vanhat, nykyiset ja tulevat mobiiliverkot sekä niiden palvelut. Ennustukset palveluiden ja markkinoiden tule- vaisuuden kehityksestä on käsitelty.

Neljännen sukupolven mobiiliverkon arkkitehtuuri mahdollistaa paikalliset palvelut jotka ovat saatavilla vain yhdessä paikallisessa 4G verkossa. Paikalliset palvelut voidaan muun- nella jokaiselle käyttäjälle erikseen käyttäen profiili-informaatiota ja paikkatietoa. Työssä on pohdittu paikallisten palveluiden käyttökelpoisuutta ja mahdollisuuksia käyttäen Lap- peenrannan teknillisen korkeakoulun 4G projektin palvelupilotin tuloksia.

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PREFACE

This thesis was written in the 4G project realized in the Laboratory of Telecommunica- tions, Department of Information Technology of Lappeenranta University of Technology.

This thesis represents the research results accomplished in the project.

I would like to thank my colleagues Marko Myllynen, Olli Suihkonen, Sami Lindström, Mika Yrjölä, Jari Kellokoski, and Ossi Kauranen for creating an enjoyable working environment. I would also like to thank my supervisor Professor Olli Martikainen for his incredible future visions, advices, delightful stories of good old times in telecommunication research, and unlimited patience for waiting for me to finish my thesis.

A big thank you goes to my mother and to my girlfriend for their love and support.

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LIST OF FIGURES

1 Transmitted petabits per day in Europe . . . 12

2 OSI reference model versus TCP/IP model . . . 19

3 Bluetooth protocol stack . . . 27

4 GSM network architecture overview . . . 34

5 3G network architecture . . . 36

6 Vertical services versus horizontal services . . . 37

7 New terminal functionalities . . . 38

8 The shift from telecom networks to IP networks . . . 40

9 Mobile IP operation . . . 41

10 4G network architecture . . . 43

11 Internet applications in Europe . . . 46

12 User roles in 4G . . . 47

13 Local services in 4G . . . 49

14 WWW-page with advertisement frame . . . 55

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LIST OF TABLES

1 Anonymous profile . . . 54

2 Private profile . . . 54

3 Advertisement criterias . . . 56

4 Advertisement matrix for three users . . . 57

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ABBREVIATIONS

1G First Generation

2G Second Generation

3G Third Generation

4G Fourth Generation

AM_ADDR Active Member Address

AMPS Advanced Mobile Phone Service

AP Access Point

AR_ADDR Access Request Address ARP Address Resolution Protocol

ARPANET Advanced Research Projects Agency Network ASP Application Service Provider

AuC Authentication Center BD_ADDR Bluetooth Device Address BSC Base Station Controller BSS Base Station System BTS Base Transceiver Station

CCIRN Coordinating Committee for Intercontinental Networks CCK Complementary Code Keying

CGI Common Gateway Interface

CN Correspondent Node

CREN Corporation for Research and Educational Networking CSMA/CA Carrier Sense Multiple Access with Collision Avoidance

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DARPA Defense Advanced Research Projects Agency DECT Digital Enhanced Cordless Telecommunications DHCP Dynamic Host Configuration Protocol

DNS Domain Name System

DSL Digital Subscriber Line

DSSS Direct Sequence Spread Spectrum EDGE Enhanced Data rates for GSM Evolution EIR Equipment Identification Register ESS Extended Service Set

ESSID Extented Segment Set ID

ETSI European Telecommunications Standards Institute

FA Foreign Agent

FHSS Frequency Hopping Spread Spectrum FNC Federal Networking Council

FTP File Transfer Protocol GAP Generic Access Profile

GFSK Gaussiang Frequency Shift Keying GGSN Gateway GPRS Support Node

GMSC Gateway MSC

GPRS General Packet Radio Service

GSM Global System for Mobile communications

HA Home Agent

HCI Host Control Interface

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HIPERLAN High Performance Radio Local Area Network HLR Home Location Register

HomeRF Home Radio Frequency

HR High Rate

HSCSD High-Speed Circuit-Switched Data HTML HyperText Markup Language HTTP HyperText Transfer Protocol IAB Internet Activities Board

IANA Internet Assigned Numbers Authority IBSS Independent Basic Service Set

IEEE Institute of Electrical and Electronics Engineers IETF Internet Engineering Task Force

IP Internet Protocol IPSec IP Security

IPv4 Internet Protocol version 4 IPv6 Internet Protocol version 6 IR Internet Registry

ISDN Integrated Services Digital Network ISM Industrial, Scientific, and Medical

ISO International Organization for Standardization ISP Internet Service Provider

IWU Inter Working Unit Kbps kilobits per second

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L2CAP Logical Link Control and Adaptation Protocol

LAN Local Area Network

LAP Lower Address Part

LDAP Lightweight Directory Access Protocol LLC Logical Link Control

LMP Link Management Protocol LMSC LAN/MAN Standards Committee MAC Medium Access Control

MAN Metropolitan Area Network

MHz megahertz

MIB Management Information Base

MIP Mobile IP

MN Mobile Node

MS Mobile Station

MSC Mobile services Switching Center Mbps megabits per second

NAP Non-significant Address Part

NASA National Aeronautics and Space Administration NCP Network Control Protocol

NIC Network Information Center NIC Network Interface Card NMT Nordic Mobile Telephone NSF National Science Foundation

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NSS Network Subsystem OBEX Object Exchange

OMC Operations and Maintenance Center OSI Open Systems Interconnection PAN Personal Area Network

PAR Project Authorization Request PDA Personal Digital Assistant PM_ADDR Parked Member Address PPP Point-to-Point Protocol

PRNG Pseudo Random Number Generation PSK Phase-Shift Keying

PSTN Public Switched Telephone Network

RADIUS Remote Authentication Dial-in User Service RARE Reseaux Associates pour la Recherche Europeenne

RFC Request For Comments

RM Reference Model

RSCS Remote Spooling Communications Subsystem SCTP Stream Control Transmission Protocol

SDAP Service Discovery Application Profile SDP Session Description Protocol

SDP Service Discovery Protocol SEC Sponsor Executive Committee SQL Structured Query Language

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SGSN Service GPRS Support Node SIG Special Interest Group SIM Subscriber Identity Module SIP Session Initiation Protocol SLP Service Location Protocol SMTP Simple Mail Transfer Protocol SMS Short Message Service

SNMP Simple Network Management Protocol TAG Technical Advisory Group

TCS Telephony Control protocol Specification TCP Transmission Control Protocol

UAP Upper Address Part

UART Universal Asynchronous Receiver/Transmitter UDP User Datagram Protocol

UMTS Universal Mobile Telecommunications System URL Uniform Resource Locator

USB Universal Serial Bus

UTRAN UMTS Terrestrial Radio Access Network VLR Visitor Location Register

VoIP Voice over IP

WAE Wireless Application Environment WAP Wireless Application Protocol WEP Wire Equivalent Privacy

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WG Working Group

WLAN Wireless Local Area Network

WWW World Wide Web

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1 INTRODUCTION

The 1990’s was an interesting decade in the history of telecommunication. Two telecommunication networks became very popular, namely the Global System for Mobile communications (GSM) and the Internet. Today about 70% of Finnish people own a GSM mobile phone and around 30% have an Internet connection. These figures are roughly the same for all Nordic European countries. The growth of GSM users has already slowed down in Finland. Everyone who wants a GSM phone already has one. Internet access sales are however still growing. There is also a strong shift from narrowband Internet connections to broadband connections, which have lately become more affordable to con- sumers. The adoption of broadband Internet is increasing the amount of transmitted data in TCP/IP networks multiple times greater compared to data transmitted in Integrated Services Digital Networks (ISDN) (see Figure 1). [Mar00b]

Figure 1: Transmitted petabits per day in Europe

The next big step in mobile networks is to enable wireless data traffic at reasonable rates using new technologies which are merged with the GSM standard. The Wireless Appli- cation Protocol (WAP) was developed as a stripped-down Internet for cellular phones, but the adoption of WAP is nowhere near industry expectations because of technical prob-

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lems and high cost. The effort to enable true Internet usage from mobile terminals has not produced good results so far.

Instead of enabling Internet services over traditional mobile networks, the alternative is to enable traditional telecom services on the Internet using short range broadband wireless access technologies. Building short range mobile networks requires substantially smaller investments compared to for example Universal Mobile Telecommunication Sys- tem (UMTS) networks. Short range wireless access technologies typically operate in license free frequency bands. To become an operator one only needs to have a broadband Internet connection and a few wireless local area network (WLAN) access points.

Short range wireless access technologies are capable of transmitting data at 11 Mbps today. Third generation mobile network technologies will be able to transmit data at 2 Mbps in the year 2005. At that time, short range wireless technologies will be able to transmit data at several tens of megabits per second. The disadvantage is the short range which ultimately leads to a hybrid network where only buildings or special outdoor areas are covered using short range wireless technologies while the outside environment is GSM/UMTS based. This hybrid network is called the fourth generation (4G).

In addition to Internet services and traditional telecom services, short range wireless access technologies enable new kinds of services: local services. These services are available only in one local 4G wireless network. This thesis presents the idea of local services in a fourth generation mobile network.

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2 INTERNET

2.1 The History of the Internet

The U.S. Defense Advanced Research Projects Agency (DARPA) initiated a research program called the Internetting project in 1973 to research technologies for linking together various kinds of packet networks. The objective was to develop communication protocols which would allow networked computers to communicate transparently across multiple, linked packet networks. The result from the research is a system of networks known as the “Internet”. After two protocols were developed, the Transmission Control Protocol (TCP) and Internet Protocol (IP), the protocol stack became know as the TCP/IP Protocol Suite. [Cer01]

The U.S. National Science Foundation (NSF) launched the development of NSFNET, which is a major backbone of the Internet these days. NSFNET carries some 12 billion packets per month between different networks using 45 Mbps links. The National Aero- nautics and Space Administration (NASA) set up an additional backbone known as the NSINET and the United States Department of Energy contributed the ESNET backbone.

NORDUNET and other major international backbones in Europe provide connectivity to over one hundred thousand computers on a large number of networks. In the U.S.

and Europe, commercial network providers are also beginning to offer Internet backbone services and access support to any interested parties.

Various consortium networks provide “Regional” support for the Internet. Research and educational institutions are providing “local” support. In the U.S, industry has made a considerable contribution, but the major part of this support has come from the federal and state governments. The situation in Europe and elsewhere is different, national research organizations and cooperative international efforts provide the support. During the course of its evolution, particularly after 1989, the Internet system began to integrate support for other protocol suites into its basic networking fabric. Currently the focus of the Internet system is providing multiprotocol interworking and integration of Open Systems Interconnection (OSI) protocols.

In the 80’s, both public domain and commercial versions of the about 100 protocols of

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TCP/IP protocol suite became available. OSI protocol implementations became available during the 1990’s. By the end of 1991, the Internet consisted of some 5000 networks in more than 60 countries, 700 000 interconnected computers, and over 4 million users.

The U.S. Federal Government has provided major support for the Internet community, since the Internet was originally part of a federally-funded research program and, sub- sequently, has become a major part of the U.S. research infrastructure. The population of Internet users and networks expanded during the 80’s internationally and commercial aspects began to appear. Nowadays, the major part of the system is made up of private networking facilities in educational and research institutions, businesses, and in government organizations across the globe.

The Coordinating Committee for Intercontinental Networks (CCIRN) plays an important role in the coordination of plans for government -sponsored research networking. CCIRN is organized by the United States Federal Networking Council (FNC) and the European Reseaux Associates pour la Recherche Europeenne (RARE). The efforts of CCIRN have been encouraging the support of international cooperation in the Internet environment.

2.2 The Technical Evolution of the Internet

The Internet has been a team work of cooperating parties over its twenty year history.

Certain key tasks have been critical for Internets operation, one of the most important is the specification of the protocols which enables interoperable computing across packet- networks. As mentioned above, the DARPA research program originally developed the protocols, but over the years the work has been done by government agencies in many countries, industry, and the academic community. To guide the evolution of TCP/IP protocols, the Internet Activities Board (IAB) was created in 1983. IAB also provides research advice to the Internet community.

IAB has gone through several reorganizations during its lifetime. It now has two main components: the Internet Engineering Task Force and the Internet Research Task Force.

The IETF is responsible for the further evolution of TCP/IP protocols, standardization of protocols and integration of other protocols to the Internet system. The Internet Research Task Force continues to organize and explore advanced concepts in networking under

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the guidance of the Internet Activities Board and with support from various government agencies.

A secretariat has been created to manage the day-to-day function of the Internet Activi- ties Board and Internet Engineering Task Force. The IETF holds meetings three times a year. Approximately 50 IETF working groups communicate using electronic mail, tele- conferencing, and face-to-face meetings at intermediate times. The IAB meets quarterly face-to-face or by videoconference and at intervening times by telephone, electronic mail, and computer-mediated conferences.

The IAB has two other functions which are critical to its operation: publication of documents describing the Internet and the assignment and recording of various identifiers needed for protocol operation. Protocols and other aspects of the Internet’s operation have been recorded in a record of documents called Internet Experiment Notes and later in a record of documents called Request for Comments (RFCs). Beginning in 1969, RFCs were used to document the protocols used by the ARPANET, which was the first packet switching network developed by DARPA. Later on, RFCs have become the main archive of information about the Internet. At present, the publication function is provided by an RFC editor.

The Internet Assigned Numbers Authority (IANA) is responsible for the recording of identifiers. IANA has delegated one part of this responsibility to an Internet Registry which acts as a central repository for Internet information. The Internet Registry (IR) provides central allocation of autonomous system and network identifiers. It also provides central maintenance of the Domain Name System (DNS) root database which points to subsidiary distributed DNS servers replicated throughout the Internet. The distributed DNS database is used to associate host and domain names to Internet addresses. The DNS system is critical to the operation of the higher level TCP/IP protocols including the World Wide Web (WWW) and electronic mail.

Several Network Information Centers (NICs) are located on the Internet. NICs provide documentation, guidance, advice, and assistance to users. The need for high quality NIC functions increase as the Internet continues to grow. Although the first users of the Internet were from the field of computer engineering and programming, nowadays users represent a wide variety of disciplines.

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2.3 Related Networks

Two other networking projects, BITNET and CSNET, were also initiated. BITNET used the IBM Remote Spooling Communications Subsystem (RSCS) protocol suite and direct leased line connections between participating sites. Most of the original BITNET connections were used to link up IBM mainframes in universities. This situation changed quickly when protocol implementations became available for other machines. BITNET has been used by people from all academic areas. BITNET has also provided a number of unique services to its users, for example LISTSERV. Nowadays, BITNET and its parallel networks have several thousand participating sites. Today, BITNET uses a TCP/IP protocol based backbone where RSCS-based applications run on top of TCP. CSNET used the Phonenet Multi-channel Memo Distribution Facility (MMDF) protocol for telephone- based electronic mail relaying and, in addition, pioneered the first use of TCP/IP over X.25 using commercial public data networks. An early example of a white pages directory service was provided by a CSNET name server. This software is still used by many sites. CSNET, at its peak, had approximately 200 participating sites and international connections to approximately fifteen countries.

BITNET and CSNET joined to form the Corporation for Research and Educational Net- working (CREN) in 1987. The CSNET service was discontinued in the fall of 1991, having fulfilled its significant role in academic networking service. All operational costs of CREN are paid by participating member organizations.

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3 THE TCP/IP PROTOCOL STACK

3.1 Open Systems Interconnection

OSI (Open Systems Interconnection) is a standard description or "reference model" for how messages should be transmitted between any two points in a telecommunication network. The purpose is to give implementators guidelines on how to create interoperable products. The OSI model defines seven layers to present the functions which need to be done on each end of a communication. Although the OSI model is not widely used, every other model in telecommunications is described by how it relates to the OSI model. The value of the OSI model is important to education because it provides a single reference view of communications.

The development of OSI began in 1983 by major computer and telecommunication companies. The original intention was to give a detailed specification of interfaces. The out- come was a reference model for which others could develop interfaces that in turn could become standards. The International Organization of standards (ISO) officially adopted OSI as an international standard.

OSI divides the communication process into layers, in which each layer handles its own set of functions. The flow of data between communicating parties travel through these layers. Starting at the topmost layer and down the stack to the lowest layer, then to the other party and up through the layers ultimately to the user or program. The components which implement these layers are operating systems, hardware, TCP/IP or alternative transport and network protocols, and applications such as a web browser.

The seven layers of the OSI reference model are in two groups (see Figure 2). The upper four layers handle the message to or from a user, while the lower three layers are used when a message travels through the host computer. A message intented for this computer travels through all seven layers. A message coming from another host and destined elsewhere is forwarded using the lower three layers. The seven layers are:

Layer 7: The application layer. The application layer handles the identification of par- ties, quality of service, authentication and privacy considerations. This layer is not the

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NETWORK APPLICATION TCP/IP MODEL OSI REFERENCE MODEL

7 6 5 4 3 2 1

APPLICATION PRESENTATION

NETWORK

PHYSICAL PHYSICAL

DATA LINK DATA LINK

TRANSPORT SESSION

TRANSPORT

Figure 2: OSI reference model versus TCP/IP model

application, but applications can perform the functions of the application layer.

Layer 6: The presentation layer. This layer is usually part of the operating system. The layer’s functions are converting incoming and outgoing data from one presentation format to another. Another name for the presentation layer is the syntax layer.

Layer 5: The session layer. The session layer handles the set up, coordination, and termination of conversations, exchanges, and dialogs between the applications of each end.

Layer 4: The transport layer. The function of the transport layer is to ensure complete data transfer by managing end-to-end control, e.g. determining whether all packets have arrived and error-checking.

Layer 3: The network layer. This layer does routing and forwarding at the packet level.

This includes forwarding data towards the right destination.

Layer 2: The data-link layer. The data-link layer handles synchronization for the phys- ical layer.

Layer 1: The physical layer. The physical layer transfers the bit stream through the network at the electrical and mechanical level.

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3.2 TCP/IP

The Transmission Control Protocol/Internet Protocol (TCP/IP) is the protocol used in the Internet. TCP/IP protocols can also be used in private networks (intranet or extranet).

Every computer connected to the Internet must have a TCP/IP protocol implementation to be able to communicate with others.

Figure 2 illustrates the comparison of TCP/IP and the OSI reference model. The layers in the TCP/IP model are:

Layers 1 and 2: The data-link and physical layers. These layers are equivalent to layers 1 and 2 in OSI reference model. Actual technologies which are commonly used include Ethernet, ISDN, ADSL, and X.25.

Layer 3: The network layer. This is the IP protocol. The functions are essentially the same as in the OSI reference model: routing of packets towards the right destination.

Layer 4: The transport layer. There exists two transport layer protocols in the Inter- net: TCP and UDP. TCP is a connection oriented protocol, meaning that a connection has to be made between two parties before the actual data transmission can occur. The connection must be terminated after the transfer. TCP handles error-checking and packet reassembling because packets can arrive in a different order than they were sent. The other transport layer protocol is the User Datagram Protocol (UDP). UDP is a connec- tionless protocol meaning that packets can be sent and received at any time and there is no connection set up or termination. An application can send a UDP packet to any other host in the Internet, although there is no guarantee that there is an application waiting for that packet. UDP does not do packet reassembly, each packet is sent and received independently.

TCP/IP uses the client/server model of communication where clients send requests to servers which respond back to clients. The communication is mostly point-to-point. In- ternet applications use directly these two transport layer protocols to send messages. TCP was developed before UDP and is more widely used, that is why the protocol stack is called TCP/IP.

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The applications which use the TCP protocol include for example the World Wide Web’s Hypertext Transfer Protocol (HTTP), the File Transfer Protocol (FTP), Telnet (for remote terminal access), and the Simple Mail Transfer Protocol (SMTP). UDP is used by different multimedia transfer protocols.

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4 SHORT RANGE WIRELESS TECHNOLOGIES

Short range wireless access technologies have lately become popular. They offer up to tens of Mbps of bandwidth using Industrial, Scientific, and Medical (ISM) frequencies which can be freely used without a license. Local area network access is the most popular way to use these technologies, however some of them can be used in almost any situation where cables are typically used to transfer data. Two such technologies are explained in more detaile: IEEE 802.11 and Bluetooth. IEEE 802.11 is a widely deployed wireless local area network access technology and Bluetooth is a low-cost communication system used to replace cables between electronic devices. Other competing and complementary techniques are introduced thereafter.

4.1 IEEE 802.11

4.1.1 IEEE 802.11 Working Group and Standards

The IEEE Computer Society "Local Network Standards committee", Project 802, was founded in February of 1980. The LAN/MAN Standards Committee (LMSC) consists of a number of Working Groups (WGs) and Technical Advisory Groups (TAGs) as well as a Sponsor Executive Committee (SEC). The Wireless LAN (WLAN) Working Group is known as 802.11. Each project approved within an existing group is assigned a letter, for example 802.11b. The 802.11 standard was published by the IEEE in 1997. In September of 1999, the 802.11b “High Rate” (802.11HR) option was added to the standard.

Three specifications [80211] exist in the Wireless LAN working group family; 802.11, 802.11a, and 802.11b. All three specifications use carrier sense multiple access with collision avoidance (CSMA/CA) as the multiple access protocol. The 802.11 and 802.11b specifications operate at frequencies in the 2.4 GHz region of the radio spectrum. These two are the standards which are associated as “Wireless ethernet LANs” or WLANs. The 802.11a standard operates in the 5 GHz range and is not yet widely used, therefore it is not discussed further, although 802.11a is one of the most promising future wireless technologies.

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The typical data speeds for 802.11 are 1 Mbps and 2 Mbps, while 802.11b is capable of 5.5 Mbps and 11 Mbps, although speeds of up to 50 Mbps could be reached in the future with 802.11a. The 802.11 specification has one important feature: it is backward compatible with the earlier 802.11 standard.

The modulation technique used in 802.11 is phase-shift keying (PSK). The modulation in 802.11b is complementary code keying (CCK), which enables higher data transfer speed and is less sensitive to multipath-propagation interference. The data link layer is split into two sub-layers: the logical link control layer (LLC) and the medium-access control layer (MAC).

4.1.2 Description of 802.11b

The objectives of the 802.11b Project Authorization Request (PAR) are to extend the performance and range of applications for existing 802.11 networks. The aim is to use the existing MAC layer, with a data rate greater than 8 Mbps and to utilize the 2.4 GHz unlicensed frequency band. As mentioned above, the modulation type is complementary code keying (CCK) and channel scheme is 22 MHz Direct Sequence Spread Spectrum (DSSS).

Any LAN application, network operating system, or protocol, including TCP/IP and Nov- ell NetWare, will run on an 802.11-compliant WLAN as easily as they run over Ether- net. The original 802.11 standard defines the basic architecture, features, and services of 802.11b. The 802.11b specification affects only the physical layer, adding higher data rates and more robust connectivity.

4.1.3 Operating Modes

The 802.11 standard defines two devices: a wireless station, which is usually a PC equipped with a wireless network interface card (NIC), and an access point (AP), which acts as a bridge between wireless and wired networks.

The 802.11 standard also defines two operating modes: infrastructure mode and ad-hoc

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mode. Infrastructure mode uses a wired network, an access point connected to the wired network, and wireless clients. This configuration is called a Basic Service Set (BSS). An Extended Service Set (ESS) includes two of more BSSs that form a single subnetwork.

Most corporate WLANs operate in infrastructure mode, because the clients usually re- quire access to a wired network which provides services such as file servers and printing.

Ad-hoc is a mode where wireless stations communicate directly with one another without using access points or any wired networks. Ad-hoc mode is also known as peer-to-peer mode or Independent Basic Service Set (IBSS). This mode is useful when a wireless network needs to be set up quickly, for example in a conference room.

4.1.4 Security

The 802.11 standard provides security mechanisms, including MAC layer access control and encryption. The encryption mechanisms is known as Wire Equivalent Privacy (WEP).

WEP is designed to provide security to wireless networks like in wired networks. The access control mechanism uses an Extended Segment Set ID (ESSID) which is programmed into every access point. All clients need to have the same ESSID as the access point in order to use the network. Access points also have an Access Control List, which is a table of MAC addresses which are granted access to the network. Some access points can be configured to use a Remote Authentication Dial-in User Service (RADIUS) authentication server. This setup allows access control to be performed at one point only (the RADIUS server), compared to a situation were each access point is configured separately.

The data encryption of 802.11 uses a 40-bit shared-key RC4 Pseudo Random Number Generation (PRNG) algorithm from RSA Data Security. All data sent between the access point and clients can be encrypted using this key. Access points also issue an encrypted challenge packet to every client who tries to associate itself with the access point. The client must encrypt the correct response in order to authenticate itself and gain network access.

Recent studies have shown that the security features of 802.11b are not enough to protect the network from outsiders [Arb01]. IEEE has acknowledged the problem and the 802.11e working group is developing better security mechanisms for future wireless net-

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work standards. The security parts of 802.11e have moved to the 802.11i working group as of the May 2001 meeting. Before new security features are available, current network administrators should change the encryption key often enough to protect networks.

802.11 standards support the same security as other 802 LANs for access control and encryption. These higher layer security technologies should be used to create a secure network environment.

4.1.5 Future of IEEE 802.11

The IEEE has set up a new working group for higher data rate (over 20 Mbps) wireless LAN in the 2.4 GHz frequency band in October 2000. The group is called 802.11g. The goal is to extend the 802.11b standard and to recommend a solution with a higher data rate.

4.1.6 Reliability of IEEE 802.11 in a Bluetooth Environment

Bluetooth and IEEE 802.11 share the same spectrum in the 2.4 GHz ISM band. Situations in a business environment where Bluetooth and IEEE 802.11 devices operate close to each other are probable. The performance issues are studied in [Zyr99]. The conclusion is that IEEE 802.11 WLANs show good reliability even in fairly dense Bluetooth piconet environments.

4.2 Bluetooth

4.2.1 Introduction to Bluetooth

Bluetooth is a wireless communication solution for small form factor, low-cost radio devices providing wireless connectivity between different devices and to the Internet. Blue- tooth enables us to synchronize information between a notebook or a desktop computer with pagers, personal digital assistants (PDAs), and other end-user devices. Users can

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initiate the sending or receiving of a fax, initiate a print-out, and, in general have all mobile and fixed computer devices be totally connected. Bluetooth requires that a low-cost Bluetooth chip is included in each device.

The Bluetooth Special Interest Group (SIG) is a group of companies which are interested in Bluetooth technology. The SIG includes promoter companies, 3Com, Ericsson, IBM, Intel, Lucent, Microsoft, Motorola, Nokia, and Toshiba. There are also more than 2000 Adopter/Associate member companies [Blu01c]. The Bluetooth SIG has 12 Workgroups.

The Working groups further develop special areas of Bluetooth technology.

4.2.2 Specification of the Bluetooth System

The Bluetooth Specification contains information required to ensure that all different Bluetooth technology enabled devices can communicate with each other worldwide.

All products using Bluetooth technology must be qualified. The Bluetooth SIG conducts interoperability tests prior to product release. The Bluetooth 1.0 specification is divided into two documents: the Core [Blu01a], which contains design specifications, and the Profile [Blu01b], which provides interoperability guidelines. The core part specifies the components, such as radio, baseband, and link manager as well as the service discovery protocol, transport layer, and interoperability with different communication protocols.

Protocols and procedures required for different types of Bluetooth applications are specified in the profiles document.

The main goal of Bluetooth technology is to be a short-range radio link replacing the cables connecting portable and/or fixed electronic devices. Bluetooth’s main features are robustness, low complexity, low power, and low cost.

4.2.3 Core

The Bluetooth system includes two units: a radio unit (radio specification), and link control unit (baseband specification). There is also a support unit for link management (link management protocol) and host terminal interface functions.

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Figure 3 illustrates the Bluetooth protocol stack, which can be divided into four groups:

Bluetooth Core Protocols (Baseband, LMP, L2CAP, SDP) Cable Replacement Protocol (RFCOMM)

Telephony Control Protocol (TCS Binary, AT-commands)

Adopted Protocols (PPP, UDP/TCP/IP, OBEX, WAP, WAE, vCard, vCalendar)

WAP OBEX

WAE

TCS BIN SDP

IP

PPP

RFCOMM

L2CAP

Baseband / Radio

Audio commands

AT−

UCP TCP vCard /

vCal

Figure 3: Bluetooth protocol stack

The Bluetooth specification also defines a Host Controller Interface (HCI) in addition to the protocol layers mentioned above. The HCI provides a command interface to the baseband controller, link manager, and access to hardware status and control registers.

The position of HCI is usually below the Logical Link Control and Adaptation Protocol (L2CAP), although this positioning is not mandatory.

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The Cable Replacement layer, Telephony Control layer, and Adopted protocol layer enable application-oriented protocols to run over the Bluetooth Core protocols. The specification of Bluetooth is open and can be downloaded from the Bluetooth web-site [Blu01c].

Additional protocols (e.g. HTTP, FTP) can be added in an interoperable fashion on top of the Bluetooth-specific transport protocols or application-oriented protocols.

4.2.4 Radio Specification

Bluetooth uses the 2.4 GHz ISM frequency band. Channel spacing is 1 MHz. The modulation technique used is Gaussiang Frequency Shift Keying (GFSK). The radio specification regulations of Bluetooth are similar to 802.11. The frequencies cover the whole 2.4 GHz ISM band.

4.2.5 Baseband Specification

The baseband specification includes the following functions: the physical channel, physical links, packets, error correction, logical channels, data whitening, transmit and receive routines and timing, channel control, hop selection, Bluetooth audio, addressing, and security.

When Bluetooth operates in point-to-multipoint connection mode the channel is shared among several Bluetooth units. Two or more units sharing the same channel form a piconet. In a piconet, one Bluetooth device is the master of the piconet and the others are slaves. One piconet can contain seven active slaves and one master. Many more slaves can be in a so-called parked state where they remain locked to the master. The parked slaves remain synchronized to the master but cannot be active. The master controls channel access for active and parked slaves. A scatternet is a name for multiple piconets with overlapping coverage areas. Each piconet has its own hopping channel.

A combination of circuit and packet switching is used in the Bluetooth protocol. Slots can be reserved for synchronous packets. Bluetooth supports one asynchronous data channel, or up to three simultaneous voice channels in each direction. The asynchronous channel can provide 723.2 kilobits per second asymmetric data transfer and up to 57.6 Kbps in the

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return direction. The symmetric data transfer rate is 433.8 Kbps.

4.2.6 Addressing

A unique 48-bit Bluetooth device address (BD_ADDR) is allocated for each Bluetooth transceiver. This address is derived from the IEEE 802 standard. This 48-bit Bluetooth device address is divided into three fields: the LAP field (lower address part consisting of 24 bits), the UAP field (upper address part consisting of 8 bits), and the NAP field (non-significant address part consisting of 16 bits).

A 3-bit active member address (AM_ADDR) is assigned to each active slave in a piconet.

Broadcast messages use the all-zero AM_ADDR address. The master does not have an AM_ADDR. It is distinguished from the slaves from relative timing. A slave recognizes packets destined to it from the AM_ADDR. Slaves also accept broadcast messages. The AM_ADDR is placed in each packet header. The slave’s AM_ADDR is valid as long as the slave is active on the channel. As soon as the slave is disconnected or parked, the slave loses the AM_ADDR assigned to it. The master assigns the AM_ADDR to the slave when it is activated. This can happen when a connection is made to a slave or when a slave is unparked.

Slaves in park mode can be identified by a BD_ADDR or dedicated parked member address (PM_ADDR). The PM_ADDR is a 8-bit member address that separates the parked slaves. The PM_ADDR is valid as long as the slave is parked. When the slave is activated it loses its PM_ADDR and is assigned an AM_ADDR by the master. The PM_ADDR is assigned to the slave when the slave is parked.

A parked slave is allowed to send access request messages using the access request address (AR_ADDR). The AR_ADDR is not necessarily unique. Different parked slaves may have the same AR_ADDR.

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4.2.7 Service Discovery Protocol (SDP)

The Service Discovery Protocol (SDP) is a protocol for locating services in the network.

The objectives are to enable higher-level services to users and applications. SDP is also used to provide plug and play information. SDP is used only in the discovery of services.

SDP does not provide any service access or usage mechanisms.

4.2.8 Host Controller Interface (HCI)

The HCI provides a standard interface to Link Manager services and independence from hardware implementations. It also provides access to the capabilities of the Bluetooth module. The Host Control Interface is specified for USB, RS232, and UART.

4.2.9 Profiles

Profiles handle general interoperability. Interoperability exists on three different levels.

To ensure Bluetooth devices can get in contact with each other interoperability must exist on the radio level, protocol level, and application level. A profile is the main tool for ensuring interoperability. This is accomplished by reducing options, setting parame- ter ranges in protocols, specifying the order in which procedures are combined, and by defining a common user experience. Profiles can be divided into four types: transport profiles, relay (internetworking) profiles, application profiles, and interchange format and representation profiles.

4.2.10 Generic Access Profile (GAP)

The Generic Access Profile defines common modes and procedures used in all other profiles. The objective is to ensure contact between Bluetooth devices. GAP unifies termi- nology for the basic parameters and procedures for example where names, values, and numerical representation are used.

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4.2.11 Service Discovery Application Profile (SDAP)

The Service Discovery Application Profile (SDAP) is used when Bluetooth devices are searching for known and specific services as well as when they are searching for general services.

4.2.12 Other Profiles

Bluetooth has other profiles also, which are: intercom, serial port, headset, dial-up networking, fax, LAN access, Generic Object Exchange (OBEX), Object Push, File Transfer, and Synchronization profile. More profiles are defined in The Bluetooth 2.0 specification.

Some of these are: instant postcard, brief case trick, smart kiosks, and local positioning profile.

4.3 Other Technologies

There are other wireless technologies besides Bluetooth and IEEE 802.11. They offer mostly the same kind of functionality, but maybe with higher data rate or with other extra features. Nevertheless, they are having difficulties fighting against Bluetooth and 802.11 in the market. IEEE 802.11 is nowadays widely used and Bluetooth is designed for small devices.

4.3.1 HiperLAN

The European Telecommunications Standards Institute (ETSI) has adopted HiperLAN which is a set of wireless local area network communication standards. HiperLAN is primarily used in European countries. There are two specifications: HiperLAN/1 and HiperLAN/2.

HiperLAN is quite similar to IEEE 802.11 wireless local are network standards. Hiper- LAN/1 operates in the 5 GHz frequency spectrum with communication speeds of up to 20

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Mbps. HiperLAN/2 operates in the same frequency spectrum but provides data transfer rates up to 54 Mbps.

4.3.2 HomeRF

HomeRF stands for home radio frequency. HomeRF is developed by Proxim Inc. The goal of HomeRF is to combine the 802.11b and DECT portable phone standards into a single system. The range of HomeRF is about 45 meters which is too short for business applications, but enough for home usage. HomeRF uses frequency hopping and is capable of a 1.6 Mbps data transfer rate. HomeRF is mainly competing with the 802.11b standard in the home market.

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5 EVOLUTION TOWARDS 4G

5.1 The First Generation (1G)

Nordic Mobile Telephone (NMT) and Advanced Mobile Phone System (AMPS) are considered to be the first generation of mobile phone networks. They were adopted in the 1980’s, NMT in Europe and AMPS in United States.

Both of these networks used analog technologies. The data rate was very low. NMT uses 450MHz and 900MHz frequencies. NMT network operation is nowadays partly closed due to the success of the Global System for Mobile communications (GSM). Services offered by NMT were basically the same as in a fixed telephone network.

5.2 The Second Generation (2G)

The second generation of mobile phone networks (GSM) were developed to overcome the limitations of the first generation. Its mass adoption started in the middle 1990’s. Today 70% of Finnish people have a GSM phone.

GSM technology is fully digital and offers data rates of 9.6 Kbps and 14.4 Kbps. These transfer rates are quite low, however further evolution of GSM standards introduce new techniques which enable faster data rates.

A GSM network is composed of several entities, whose functions and interfaces are defined (Figure 4). The GSM can be divided into three parts. The Mobile Station (MS) is carried by the subscriber. The radio link is controlled by the Base Station Subsystem (BSS) with the mobile station. The main part of the Network Subsystem, the Mobile services Switching Center (MSC), performs the switching of calls and management of mobile services, for example authentication. The operation and setup of the network is managed by the Operations and Maintenance Center (OMC). Each component dealing with mobility is described next in more detaile.

Mobile Station (MS): The mobile station is a user terminal, which consists of a radio

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BSC

BSC MSC

BTS

VLR MS

BSS

MSC AuC

EIR

VLR HLR

NSS

Figure 4: GSM network architecture overview

transceiver, signal processors, display, and a Subscriber Identity Module (SIM card). The SIM card enables the usage of services and personal mobility.

Base Station Subsystem (BSS): The Base Station Subsystem consists of two compo- nents, the Base Transceiver Station (BTS) and the Base Station Controller (BSC). The radio transceivers are located in BSCs. The BSC also manages the radio-link with the MS. The Base Station Controller manages one or more BTSs and handles radio resources, such as radio channel setup, frequency hopping, and handovers.

The Mobile services Switching Center (MSC): The Mobile services Switching Center is the central component of the Network Subsystem. An MSC is like a normal switch in PSTN or ISDN. It also handles all the functions needed to manage mobile subscribers, including registration, authentication, location updating, handovers, and call routing. The roaming functionality of GSM is provided by the the Home Location Register (HLR) and Visitor Location Register (VLR) together with the MSC. The MSC has no information about particular mobile stations, this information is stored in VLRs and HLRs.

The Home Location Register (HLR): This functional entity is a data base in charge of

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the management of mobile subscribers. A Public Land Mobile Network (PLMN) may contain one or several HLRs. The number of HLRs depends on the number of mobile subscribers, on the capacity of the equipment, and organization of the network. The HLR contains two kinds of information: subscription information and some location information enabling the charging and routing of calls toward the MSC where the MS is located (e.g., MS roaming number, and MSC address).

The Visitor Location Register (VLR): A mobile station roaming in an MSC area is controlled by the Visitor Location Register in charge of that area. When a mobile station enters a new location area it starts its registration procedure. The MSC in charge of that area notices this registration and transfers to the Visitor Location Register the identity of the location area where the MS is situated. If this MS is not yet registered, the VLR and HLR exchange information to allow the proper handling of calls involving the MS.

[Ikk01]

5.2.1 2.5G

New technologies added to the GSM standard add faster transfer rates and a packet switching feature. These additions to GSM are often called 2.5G. The additions are:

High-Speed Circuit-Switched Data (HSCSD): HSCSD uses circuit-switched wireless data transmission for mobile users at data rates up to 38.4 Kbps, four times faster than the standard data rates of the GSM communication standard in 1999. HSCSD uses several time slots compared to the one time slot used by normal GSM.

General Packet Radio System (GPRS): GPRS is a packet-based wireless communica- tion service that promises data rates from 56 up to 114 Kbps and a continuous connection to the Internet for mobile phone and computer users. GPRS is based on GSM communication and will complement existing services such as circuit-switched cellular phone connections and the Short Message Service (SMS).

Enhanced Data GSM Environment (EDGE): EDGE is a faster version of the GSM wireless service, designed to deliver data at rates of up to 384 Kbps and enable the delivery of multimedia and other broadband applications to mobile phone and computer users.

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5.3 The Third Generation (3G)

3G is a short term for third generation wireless networks (UMTS), and refers to near- future developments in personal and business wireless technology, especially mobile communications. This phase is expected to reach maturity between the years 2003 and 2005.

GSM

IWU

GGSN

IWU

HLR

SGSN

UMTS CN

MSC GMSC

Internet PSTN

UTRAN BSS

Figure 5: 3G network architecture

The Universal Mobile Telecommunications System (UMTS) offers broadband, packet- based transmission of text, digitized voice, video, and multimedia at data rates of up to and possibly higher than 2 megabits per second (Mbps), offering a consistent set of services to mobile computer and phone users no matter where they are located in the world. Based on the Global System for Mobile (GSM) communication standard, UMTS, endorsed by major standards bodies and manufacturers, is the planned standard for mobile users around the world by 2002. Once UMTS is fully implemented, computer and phone users can be constantly attached to the Internet as they travel having the same set of capabilities no matter where they go to. Users will have access through a combination of terrestrial wireless and satellite transmissions. Until UMTS is fully implemented, users can have multi-mode devices that switch to a currently available technology (such as GSM 900 and 1800) where UMTS is not yet available.

The architecture of UMTS is presented in Figure 5 [Mar98]. The Service GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN) are components added to the

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GSM architecture by GPRS. The UMTS Core Network (CN), UMTS Terrestial Radio Access Network (UTRAN), and two Inter Working Units (IWU) are added to the GSM architecture to enable GSM, GPRS, and UMTS to operate with each other.

5.4 The Fourth Generation (4G)

The fourth generation is not a strict specification of protocols or technologies, but instead a hybrid network based on standard TCP/IP protocols where users are able to access Internet services using their mobile or fixed network. The following chapters present the visions and reasons for 4G and a network architecture overview.

5.4.1 Introduction to 4G visions

Traditional telecom and content services are vertically integrated. Each service depends on a dedicated network and corresponding terminals. Examples of such vertical services are fixed telephone services, traditional data services, and GSM services. The Internet changes this vertical structure to a horizontal one: all terminals and services will be In- ternet compatible. Instead of vertical service "pipes" there will be a horizontal structure of services, network, and access, see Figure 6. The horizontal structure will change ter-

Data TV

HORIZONTAL INTERNET BASED SERVICES VERTICAL SERVICE "PIPES"

HORIZONTAL ACCESS

TCP/IP BASED NETWORK

HORIZONTAL SERVICES ACCESS TECHNOLOGIES

NETWORK TECHNOLOGIES

NETWORK BASED SERVICES Telephone

Figure 6: Vertical services versus horizontal services

minals, services, and the way services are managed, allowing different combinations of

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service functionalities in the terminal equipment as depicted in Figure 7. The ovals de- scribe possible combinations of services in single terminals.

Games

eBooks PC TV PDA

Devices Mobile

Audio

HORIZONTAL ACCESS

IP BASED NETWORK

HORIZONTAL SERVICES

Figure 7: New terminal functionalities

Horizontal networks will not only make existing services easier and more widely applica- ble, but also create a platform for the integration of various new services and applications into the same terminals.

New terminal applications in horizontal networks can be divided into simple fixed-purpose terminals and intelligent terminals. Possible fixed-purpose terminals can be wearables (watches, eyeglasses, clothes) or appliances (light switches, doors, micro-ovens). In- telligent terminals include Personal Digital Assistants (PDA), Smart Phones, or Media Terminals. Simple terminals will connect to a Personal Area Network (PAN) or Domestic Area Network, whereas intelligent terminals use Local Area Networks (LAN) or public access networks. They will have software and content-defined functionalities, which allow various applications within one device.

Intelligent terminals will be software and content driven. Possible features of intelligent terminals include multimedia capabilities such as web content, audio, video and stream media, communication capabilities such as Voice over IP (VoIP) and mobility, and pro- grammability so that new applications and content can be uploaded and applied. The

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operating system and storage units of the terminal become key questions. Any existing services will become TCP/IP based. These horizontal services can be grouped into the following basic classes (Figure 7): original Internet Services operated by Internet Ser- vice Providers (ISP), Application Services operated by Application Service Providers (ASP) e.g. in banking and commerce, Communication Services such as unified mes- saging or VoIP by Communication Providers, and Media Services by Content Providers.

The service environment in 4G is discussed more in section 6.

Fourth Generation Mobile (4G) means broadband mobile wireless services, which are based on IEEE 802.11 Wireless LAN or Bluetooth access, IP mobility, and Web type services. Radio access can be provided by private corporate LANs, public administration LANs, mobile WLANs installed in trains, airplanes, buses or cars and single DSL connections. Corporate offices, shopping centers, hotels, airports, home networks, and personal area networks (PAN) will be the leading adopters of these technologies. Client devices for 4G applications can be categorized as follows:

Laptop PC with WLAN or Bluetooth PDA with WLAN or Bluetooth

Dual-mode wireless phone with GSM and WLAN or Bluetooth Other specialized Bluetooth devices. [Ikk01]

Traffic is shifting from telecom networks (ISDN) to IP and mobile networks (GSM, UMTS) (see Figure 8) [Mar00b]. The size of IP based networks will be equal to telecom networks by year 2005 and by the year 2010 IP and mobile networks will be the most important.

5.4.2 Mobility Management in 4G

The general requirements for mobility in 4G networks are basically the same as in 2G and 3G networks: a user can be reached from one global address without the knowledge about them or their terminal’s location. The following two sections present two solutions for mobility: Mobile IP (MIP) and the Session Initiation Protocol (SIP).

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Figure 8: The shift from telecom networks to IP networks Mobile IP

The Internet Protocol always assumes that a terminal with an IP address can be found from the subnet determined by the IP address and the network mask of the subnet. This assumption does not give the possibility of moving a terminal to another network and still use the same IP-address. Because IP does not support mobility, Mobile IP (MIP) was created by the IETF [RFC2002]. MIP enables terminals to move to other networks and use the same IP-address as they would in their home network.

The operation of MIP is presented in Figure 9 and described here shortly. When a mobile node (MN) is in its home network, IP routing is done normally. It discovers the presence of a home agent (HA) from the HA’s messages. When that MN moves to a foreign network, it no longer hears the HA but instead hears messages from the foreign agent (FA), otherwise the MN can search for a FA. When an FA is found, the MN registers itself with the FA. The FA can give a local address to the MN. After this, a registration message is sent to the HA. It now knows where to locate the MN. If a host (correspondent node, CN) connected to the Internet tries to contact the MN using its globally unique address as the destination IP address, its HA knows that MN is not in the home network and tunnels the packets coming from the CN inside new IP packets to the FA. When the FA receives

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INTERNET CN

FA HA

MN

Figure 9: Mobile IP operation

packets from the HA, it removes the extra IP header from the packets and delivers the packets to the MN. Applications in the MN think that the packets arrived just as they normally do in the home network. When the MN responds to the CN, it sends packets directly to the CN by placing its globally unique IP address as the source address field of the IP header. The CN thinks the packets arrived from the home network of the MN.

When the MN comes back to its home network it hears the HA’s messages and clears all registrations.

The advantage of MIP is that everything is done at the network layer (IP) with no need to modify applications. If a foreign network has several FAs, they can be arranged hierarchi- cally. When a MN moves from one FA to another inside this hierarchy, there is no need to send new registration messages to the HA. Even applications using TCP as the transport layer mechanism continue to work uninterrupted. The requirement for TCP applications is that the source and destination addresses remain the same during a session.

The disadvantage of MIP is that it requires Mobile IP software in user terminals. Even worse if the triangle routing problem between the CN, HA, and MN. Every time the CN sends packets to the MN, they go through the HA. If the connection from the HA to the Internet is not fast, the overall transmission between the MN and CN is slow. This problem is big enough to abandon MIP as a solution for 4G mobility management. The problem comes about with local services in 4G areas, which are discussed later in section 6.

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Mobile IP for IP version 6 offers a solution for triangle routing [Joh00]. Additional routing and address information is placed in every IP packet which enables direct routing and handling of Mobile IPv6 packets between communicating parties. This feature solves the triangle routing problem, making Mobile IPv6 usable as a mobility management solution in IP version 6 networks, but the solution creates new problems at the same time it solves old ones. When the size of every packet is increased with additional routing information, real-time multimedia applications could start to behave badly because of the additional overhead in every packet. The scope of this problem hasn’t been studied extensively yet, so no final judgment can be given.

Session Initiation Protocol

The Session Initiation Protocol (SIP) is an Internet Engineering Task Force (IETF) standard specified in [RFC2543]. SIP is built for initiating an interactive user session that can involve multimedia elements such as video, voice, chat, gaming, and virtual reality.

The obvious use of SIP is in VoIP signaling, but it can be used for example in instant messaging also.

Like HTTP or SMTP, SIP works at the application layer of the Open Systems Intercon- nection (OSI) communications model. SIP can establish multimedia sessions or Internet telephone calls and modify or terminate them. The protocol can also invite participants to unicast or multicast sessions that do not necessarily involve the initiator. Because SIP supports name mapping and redirection services, it makes it possible for users to initiate and receive communications and services from any location, and for networks to identify the users wherever they are.

SIP is a request-response protocol, dealing with requests from clients and responses from servers. SIP is very much like HTTP, it contains components like servers, proxies, and clients. Clients usually are also servers because they serve incoming sessions. Participants are identified by SIP URLs. Requests can be sent through any transport protocol, such as UDP, SCTP, or TCP. SIP determines the end system to be used for the session, the communication media and media parameters, and the called party’s desire to engage in the connection. Once these are assured, SIP establishes call parameters at either end of the connection, and handles call transfer and termination. Parameters and session properties

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are usually written as Session Description Protocol (SDP) messages. SDP specifies the details of the multimedia session like video encoding, voice encoding, transfer rates, and other important parameters. SDP is also an IETF standard protocol and is specified in [RFC2327].

5.4.3 The Architecture of a Fourth Generation Mobile Network

This architecture of a 4G mobile network is based on SIP. The elements of the architecture consist of SIP redirect servers, SIP proxy servers, and Dynamic Host Configuration Protocol (DHCP) servers (Figure 10).

Figure 10: 4G network architecture

Every home network has one redirect server. This server always knows where the users of the home network are. A user’s globally unique SIP address points to this redirect server. When a call is set-up, the SIP client software makes a connection to the redirect server and the server returns the current address of the party being called. Then the client

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software makes a new call to this address returned by the redirect server. A SIP proxy could also be used in a home network, but the proxy would have to handle more traffic because proxies forward calls instead of returning the correct address.

Every foreign network has at least one SIP proxy server and one DHCP server. When a user arrives to the foreign network, the DHCP server gives a local IP address to the terminal. When network level configuration is done the SIP agent software in the user’s terminal must register with the SIP proxy server if the user wants to receive calls to their current location. After this registration, a registration message is sent to the home network’s redirect server. The redirect server updates the location database and can now relay new calls to this new address received with the registration.

The architecture enables the use of Internet services, local services, and mobility. If users want to use services from their home network, an encrypted connection should be established using for example IPSec. This architecture of 4G mobile network is described in more detailed in [Myl01].

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6 SERVICE ENVIRONMENT OF 4G

Traditional voice services in 4G networks can be offered using SIP-based VoIP. Basic Internet services are available to users with broadband wireless access technologies. The most common Internet services are electronic mail, WWW, FTP, instant messaging, network file systems, music and video broadcasting such as Internet radio, peer-to-peer file sharing like Napster and Gnutella, and directory services (LDAP). Internet access with several megabits per second of bandwidth usually is enough for a pleasant experience with these services.

6.1 Players in the Telecom Market

The architecture of the Internet service market is changing in many ways. The increasing role of value added services and digital contents available through networks will introduce new players:

Network Operators are the traditional players owning public networks and sell- ing infrastructure and value added services. They may have also content services available e.g. in their Cable TV networks.

Service Providers create and sell value added services on top of existing networks.

Service providers do not usually own complete networks, but may own and operate certain network parts such as base stations.

Content Providers which sell digital content using these networks as their distri- bution channels. [Mar00b]

New service providers are based on Internet commerce (e.g. electronic banking, online entertainment, IP telephone), portals (e.g. cache and web directory, ISPs, corporate ex- tranets), audiovisual content (e.g. advertising, audio and video, radio), and published content (e.g. books, newspapers, magazines, advertising). New kinds of content will be available since published content is one of fastest growing areas of Internet services. Fig- ure 11 [Mar00b] illustrates current and future market values of commerce, audiovisual,

Local Services in a Fourth Generation Mobile Network