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CHAPTER – 1 INTRODUCTION TO THE STUDY

1.1 INTRODUCTION TO THE PROBLEM

This report specifies the wireless secured communication in an enterprise when there is increasing demand of ubiquitous multimedia data services, future wireless networks are expected to provide services with wider coverage area, reliable and higher data throughput with security. To acheive these goals, wider bandwith at higher carrier frequency above 2GHz is forseen to be needed. Since the radio propogation in these frequency band is more velnurable to non line of sight conditions and today's wireless radio communication uses lot of bandwith, these applications tend to be very bursty, so simply provisioning bigger circuit is not adequate. Therefore a new approach towards the latest technology is need to be proposed. The IP-Based transport that can take advantage of statistical multiplexing to more efficiently exploit the available bandwidth, coupled with strong quality of service enforcement to ensure that the high-priority traffic gets through during the usage peak.Ubiquitous data transmission is necessary in todays world that means availability of resources anywhere, anytime.To provide All – IP service, maintaining reliability and avoiding low call blocking and dropping probability, high data rates for multimedia and data applications a standard Quality of Service (QoS) scheme is considered necessary. The advantages of wireless LAN are tremendous but the security is a major concern. Effective security solutions should be implimented in the corporation to investigate and roll – out any vulnerablity. Without physical security that can be used to protect wired networks, wireless users need to protect their networks with other tools that can provide the same level of security as wired networks. These solutions can be layered to provide the level of security required for any user or organization. Therefore a structured security infrastructure model is desired to prevent the compromise of wireless networks.

1.2 WHY SECURITY AND RELIABILITY IMPORTANT IN WIRELESS COMMUNICATIONS.

The most important fact in wireless communications is that the data is transmitted over the air and because of this security and reliability becomes an important issue.First generation (1G) and second generation (2G) mobile communication was significantly stressed on voice transmission, and during evolution the impact of internet has lead to a drammatic growth of data traffic since the desireable change in the cellular network architecture looked-for in accordance to the need of subscribers but the technology came with lots of vulnerability, keeping the doors for intruders wide opened.The reliability indicates the transmission characteristics required by an application.There are reliability classes defined, which guarantee certain maximum values for the probability of loss, duplication, mis-sequencing, and corruption of packets.

1.3 RATIONALE.

4G is a relatively new technology and it is still undergoing development whereas standards in 4G evolved from 3G such as Wimax as an extension from CDMA and LTE (Long Term Evolution) from UMTS.So most of the study is around 3G, majority of research has been conducted with the help of papers and articles from IEEE explore, techrepublic articles, 3GPP2 org., ITU and cdg.org etc.

A number of studies investigated the technological and engineering aspects, including Layered security, WAN management functions, WAN assurance and reliability (explained by Craig Mathias, Principal and cheif director of 'Far Point Group')

The massive, bursty growth in the wireless data transmission and in an industry as a cost-effective means of resolving, managing and at the same time to provide real-time application, quality of service (QoS) under given security policies is far more difficult task.That is why this study is guided by rationale of exploring these determinants.

1.4 AIMS AND OBJECTIVES OF THE STUDY:

AIM:

To study a Reliable data transmission over wireless network by using industry standards (IEEE 802.11) and to analyse and evaluate reliability of Broadcast and multicast for a secure enterprise.

OBJECTIVES:

Objective Number

Objective Description

1

To study the evolution of mobile communication system and illustrating the problems.

2

To study and analyse security in mobile comunication in an enterprise.

3

Comparing the network and protocol architecture of two principle 3G cellular based standards: UMTS and CDMA 2000

1) Studying QoS architecture to ensure reliability.

2) Analyse and evaluate different protocols and algorithms used for reliable communication over the wireless networks.

2 CHAPTER – II METHODOLOGY

The approach of this report is to address two isuues reliablity, the efficiency of the data in wireless environment and how the data security is managed in cellular systems.After thorough research,collecting information about varoius techniques from the evolutionary cellular systems to the latest 4G standards and resources available from IEEE xplore, papaers, journals, technical articles and reviewing blogs and also resouces from library books,whitepapers available on internet specially Vodafone UK and Motorola Inc. led to drive and explore more information about the subject.With help of evolutionary history of the subject an studying different technologies it is evident why there is a transition to new generation technologies – Limitation of 1G,2G and now 3G are being optimised specifically to enhance today's networks, deliver unprecedented functionality for 3G, and successfully drive the Fourth Generation (4G) of wireless, thus delivering immediate and long-term benefits to carriers.Evaluating the problems in todays wireless security architecture and vulnerability could be an achievement toward future cellular networks.In addition to this a comparison of two 3G based wireless, standards UMTS (Universal Mobile Telecommunication system) and CDMA 2000 (Code Divison Multiple Access) architectural study is provided to illustrate network and protocol architecture defining major protocols which increases system throughput and security.Demostration of Packet Core Network in case of UMTS (WCDMA) and CDMA2000 which provides support to network features and telecommunication services.The massive, bursty growth in the wireless data transmission and in an industry as a cost-effective means of resolving, managing and at the same time to provide real-time application, quality of service (QoS) under given security policies is far more difficult task.The optimisation of core network including QoS support, Authentication, mobility and availibilty (roaming) on overall performance is supplied by utilizing core network protocols like MAP (Mobile application part) and GTP (GPRS Tunneling protocol) Interference is a major concern in reliable data tranmission most of the wireless standard uses 2.4 GHz band and it is crowded by large number of devices due to which the cell system have to suffer from co-channel interference from other cells.in order to avoid this, a thorugh study of QoS schemes are provided to ensure efficient usage of spectrum when availability is limited.A method of communicatoin information presenting reliable broadband over channel including quality of service (QoS) by studying end to end services in UMTS and CDMA 2000 network architecture.

Methodology PROcedure iMPLEMENTED IN THE PROJECT

CHAPTER – III REVIEW OF LITERATURE

research in the area of secure and reliable wireless network has increased exponentially and also lots of new techniques are evolving day by day.Reaserchers are focused o addressing the myriad of challenges that have brought fourth from limited resource capabilities.In terms of technical approach much of the research is being conducted in the following areas:

* Studying the evolution of wireless communication system.

* Improving the reliability of data transfer.

* Finding techniques that will enforce reliable and secure network implementation.

The literature review for this report is an attempt to present and evaluate the work that has been done on the subject of security and reliability of wireless communication system.The main approach of study is to argue that many researchers insist that security and reliability are two far difficult acronyms to be combine with wireless technology.However, a strategical method has been implemented to cover most of techniques and technologies.

BACKGROUND HISTORY

In 1897, for the first time in europe a more pratical means of sending and recieving signals was done by italian inventor Guglielmo Marchese Marconi by his system apparatus which can send signals to a point few kilometers away with the help of directional antenna.After that for the first time communication across English channel between England and France was established using his transatlantic system. The earliest system for radio services was made in 1919 that provided two-way communication which meanns a radio can both transmit and recieve (a transciever), unlike broadcasting which only recieve contents.(Harley.S 1999) For the next 12 years or so, considerable improvement was made to radio communication technology to provide an effective high-seas mobile radio service. For the land based users however the earliest mobile phone service was started in 1933.There were only 10 channels in the system with 40 KHz spacing. Because the mobile could not receive and transmit information simultaneously, the user had to "push to talk" these cellular calls are half duplex communication. There was no roaming feature available.(Schwartz 2005)

Subsequently, in 1946 Federal communication commision (FCC) an independent agency of United States granted some spectrum on the 150 MHz band for improved mobile telephone service; this was the time when first commercial service was introduced following this frequency spectrum allocation. The earlier systems were manual in that all calls were handled by a telephone operator. Because of the heavy demand for the service, the FCC allocated six more channels around 150 MHz and 12 new channels around 450 MHz in 1956. In 1964 an improved version of mobile telephone service was introduced known as "MJ", this system operated at 150 MHz and 11 channels. Initially, the channel spacing was 120 but with the advancement of radio frequency (RF) circuit technology, this spacing was reduced to 30 KHz with a peak frequency deviation of 5 KHz. Roaming feature were now provided; however, because the complete routing information was not available to the local switch, a land-originated call to a roaming mobile had to be completed manually by telephone operators. The mobile unit could scan all available channels, lock onto an idle one, and then start dialing. Signaling was done using low-frequency audio tones. The maximum range between a serving transmitter and a mobile unit was about 25 miles. To provide satisfactory operation, frequency could be reuse only at a distance of 75 miles and more.(Kasera & Narang, 2004)

To meet the growing demand from customer, the FCC opened up another spectrum in 450 MHz band. This system which was introduced in 1969, was known as the MK system and had 12 channels with a frequency spacing of 25 KHz. Like its predecessors, it supported automatic dialing and operator-assisted roaming.

These early systems provided by three types of mobile telephone service:

§ Complete Mobile Telephone Service (MTS) for voice communication to land-mobile user assisted with mobile telephone operators where necessary.

§ Automatic Dispatch Service was used between one or more dispatchers and fleet mobile units. This service supported only two-way conversation at a time between a dispatcher and a mobile unit. Conference calls between a dispatcher and multiple mobile units were not possible.

§ One-way paging

The spectrum allocated by the FCC for these early systems was usually quite small as compared to the relatively large number of contending users. Thus, naturally, as the demand grew, users experience high probability of call blockage. To overcome this fundamental problem, FCC set aside a bandwidth of 75 MHz in the 850 MHz range and asked common carriers to submit their proposals for a High Capacity Mobile Telecommunication system (HCMTS). In response, the Bell System submitted comprehensive detail of one such system based on "Cellular Concepts" that had been under development in Bell Laboratories since 1947. Finally in 1974, the FCC ruled that 40 MHz of the original 75 MHz spectrum could be used by common carriers to provide advanced mobile telephone service, and the remaining 30 MHz was reserved for private services.

In the evolutionary system voice was the major topic to consider as cellphones uses analog transmission technique for transmitting data between a mobile station and base station.It is very important to understand the cellular evolution system because during the evolution all the technologies are inter-related as the newer technologies upgraded from the older ones.Many wireless networks are based on radio waves , which makes the network medium inherently open to interception.Properly protecting radio transmission in any network is always a matter of concern.(Gast, 2005)

2.0 EVOLUTION OF MOBILE RADIO COMMUNICATIONS

2.1 First Generation Cellular networks.

Since the early 1980s, when the first-generation mobile systems were introduced, mobile communications has experienced enormous growth. The world's first cellular systems such as the Advanced Mobile Phone System (AMPS), Total Access Communications System (TACS), and Nordic Mobile Telephony (NMT) were pretty basic using radio analog transmission and allowing the transmission of speech and only speech. The limited amount of available radio spectrum, however, could not accommodate the ever growing needs of customers and, as a consequence, dropped calls and network busy signals became common in many areas.(www.springerlink.com) The first generation of mobile telephony (1G) operated using analogue communications and portable devices that were relatively large.

AMPS: In early 1980's Bell labs invented AMPS and was initially deployed in U.S.Bell operating companies (ROBOCs) owned the local cellular operation service from AT & T at the time when it was privatised in January 1984 (www.leapforum.org)

The frequencies allocated by the FCC to AMPS channels in reverse range between 824 to 849 MHz (mobile to base) and in forward cahnnel 869 to 894 MHz (base to mobile).When the service's popularity became evident, allocation by FCC was extended from 40 MHz to 50 MHZ because of uncontiguous blocks . There are now a total of 416 channels available in each direction, numbered from 1 to 1024 with gaps in the numbering. (www.leapforum.org).

When a mobile station is in the current cell a physical channel at 30 KHz is dedicated to it for that instance of duration of time.each and every call is provided with a forward channel which is further paired with dedicated reverse channel with an offset of 45 MHz.Voice conversations are conveyed by analog frquency modulation (FM) with traffic channel deviation (8 KHz) and for signaling purpose binary frequency shift keying is used (FSK) at 10 kbps.(Taylor, 1996)

Any mediator with a channel scanner can listen to insecure AMPS channel and also these channel suffer from interference with different environmental phenomenon, analog signals error cannot be corrected such as signal suffered from multipath fading.(Taylor,Waung & Banan, 1996)

Roaming

Roaming is the process, where a user can receive service while in another service providers domain. Roaming functionality in AMPS was provided by IS-41 standard, implemented by different equipment manufacturers.Before IS-41, the roaming capabilities had to be manualy administered and it was proprietary in nature to send signals between the systems.

AMPS Cellular Operation

AMPS is supported by mobility management functions and radio resource management functions which consist of procedures like call origination and termination.It greatly impact that the processes handled as AMPS was designed for voice only systems.There was 21 predefined control channels which non-physically differ from AMPS traffic channels except the way they are used for control puposes.For the registration, the Mobile station needs continuous broadcast information utilized by forward control channel in each cell.To know roaming capabilities mobile station uses this information including SID (Subscriber Identity) of the MSC.AMPS Mobile station registers itself to a serving network by finding a best forward control channel it can recieve and announces itself via matching reverse control channel.When channel quality degrades or the mobile crosses boundary between location areas a call event occurs and mobile starts sending signals to the network.

Total Access Communications System

Total Access Communication System (TACS) is the European version of AMPS developed by Motorola. TACS uses 1320 channels with 25 KHz channel spacing which allows and the superior signaling and operates using a 900 MHz frequency band.(www.birdseye.net).In 1985, TACS was used for the first time in United Kingdom and similar to AMPS it was designed for highly dense urban areas having spectral allocation between 800-900 MHz.

In 1989 Motorola deployed first TACS system in Japan for DDI's kansai Cellular Telephone Co.and after that NTACS (narroeband TACS) introduced by Motorola in 1991.

There was number of flaws in security architecture of 1G mobile communication, beacuse each phone transmitted its own frequency due to this fact mobile station were almost vulnerable to security risks.(Riezenman 2000).

2.2 Second Generation (2G) Cellular Networks.

Second Generation (2G) a Mobile cellular system was first developed at the end of the 1980s.These system was developed for voice communication Digital system. The digital modulation used was TDMA / FDD and CDMA / FDD multiple access therefore, providing data rates of the order of ~ 9.6 kbps.The new system provided better quality and higher capacity at lower cost to consumers.GSM (Global system for mobile communication) was the first commercially operated digital cellular system which is based on TDMA (Time Divison Multiple Access) and FDMA (Frequency Divison Multiple Access).

FDMA - Frequency Division Multiple Access

FDMA is the Multiple access scheme which means Individual user have their own frequency.This scheme was used by secong generation analog systems.The network allocates a frequency or channel to each one and switch one cell to another as a subscriber moves into the system,In this way different slot are allocated to the subscriber and user get access to the network. As different frequencies are used, the system is naturally termed Frequency Division Multiple Access.(www.radio-electronics.com)

TDMA - Time Division Multiple Access

In Time Divison Multiple Access each user can communicate in their own time slot.This scheme was transition to digital cellular technology, where data was divided in time and sent as bursts when required. As digitised speech message sent in short data bursts, and there was very small delay when data was sent into burst making it unnoticeable for the subscriber.. In this way it became possible to organise the system so that a given number of slots were available on a give transmission.Users are allocated with their own different time slots to recieve and transmit data.but because of subscribers using different time slots for system access the number of users are limited to an extent which created a problem of availability.

CDMA - Code Division Multiple Access

CDMA uses one of the aspects associated with the use of direct sequence spread spectrum. CDMA uses codes to convert between analog voice signals and digital signals.CDMA also uses codes to separate voice and control data into streams called channels.These digital streams channel should not be confused with frequency channels.If a data is need to extract from a DSSS (Direct sequence- spread spectrum) signal it was necessary to have the correct spreading or chip code, and all other data from sources using different orthogonal chip codes would be rejected. It is therefore possible to allocate different users different codes, and use this as the means by which different users are given access to the system.

In this way the base station allocates different codes to different users and when it receives the signal it will use one code to receive the signal from one mobile, and another spreading code to receive the signal from a second mobile. In this way the same frequency channel can be used to serve a number of different mobiles.(www.radio-electronics.com)

Generating a CDMA signal

There are five steps in generating a CDMA signal.

* analog to digital conversion

* vocoding

* encoding and interleaving

* channelizing the signals

* conversion of the digital signal to a Radio Frequency (RF) signal.

CDMA was accepted worldwide because of its several advantageous featuers.The most important reason is, more users can use a given amount of spectrum.This multiple access scheme allows different base stations to operate on the same channel providing easier handover and efficient use of spectrum.

Digital Enhanced Cordless Telecommunications (DECT)

The phase of Second Generation (2G) Mobile System calibrated with digital enhanced cordless telecommunication (DECT), this standard proposed by CEPT (the Council of European PPTs), was initially conceived in the mid – 1980s as a pan – European standard for domestic cordless phones. The objective of the new standard was to use digital radio technology to improve the performance of cordless phones in three important areas – speech quality, security against eavesdropping, and immunity from radio interference between nearby cordless phones.

By the time the DECT standard was finalisedin 1992 and published by ETSI (the Successor to CEPT), the scope of the standard had broadened beyond domestic cordless phones include two additional application area – one being the business cordless telephones (the so called cordless PBX or wireless PBX) and other being a cordless access system for subscribers to public telecom networks.

Characteristics: DECT is a digital radio access standard for single- and multicell cordless communications.It is based on multicarrier time divison multiple access (TDMA) technology.The stardard specifies four layers of connectivity, plus other important functioond.The four layers correspond approximately to layer 1 to 3 of the ISO open system interconnection (OSI) model, as follows:

Physical layers. Radio parameters such as frequency, Timing and power values, bit and slot synchronisation, and transmitter and reciever performance.

Medium access control layer. The establishment and release of connections between portable and fixed parts of the DECT system.

Data link control layer. Provides very reliable data link to the network layer signaling, speech transmission, and circuit and packet-swithching data transmission.

Network layer .The main signaling layer specifying message exchange required for the establishment, maintenance and release of calls between portable and fixed element of the network.

The DECT radio interface. The DECT radio interface standard is based on the multicarrier, time divison multiple access; time division duplex (MC/TDMA/TDD) radio access methodology.Basic DECT frequency allocation uses 10 carrier frequencies (MS) in the 1880 to 1900 MHz range. The time spectrum for DECT is subdivided into time-frames repeating every 10 ms.Each frame consists of 24 time slots each of which may be used for either transmission or reception. For the basic DECT speech service, two time slots are paired with 5 ms separation to provide bearer capacity of typically 32 kbit/s (ADPCM G.726 coded speech) full duplex connections.

Global System for Mobile Communication (GSM)

Global System for mobile Communication (GSM) is the name of the European digital mobile telephone network. In 1980, in France the architecture for the GSM was created and first steps were taken in 1982 when CEPT founded the Groupe Special Mobile which initially gave GSM its name.

GSM Architecture: GSM networks are structured heirarchially.It consist of one administrator region, which is assigned to a MSC (Mobile Services switching Center).

Each administrative region is made up of atleast one Location Area(LA).LA is also called the Visited area, a Location Area consist of several cell groups and each cell group is assigned to a base station controller (BSC).Cells of one BSC may belong to different LA.

GSM distinguishes explicitly between user and equipment and deals with them separately.The user identifier is associated with a Mobile Station (MS) by means of a personal chip card, the SIM (Subscriber Identity Module) which is portable and therefore transferable between different Mobile Stations.GSM can also distinguishes between the subscriber identity and the telephone number. Besides a subscriber, phone numbers and equipment identifiers, several other identifiers have been defined; they are needed for the management of subscriber mobility and for addressing of all the remaining network elements. The most important addresses and identifiers are presented in the following:

* International Mobile Station Equipment Identity:

* International Mobile Subscriber Identity

* Mobile Subscriber ISDN Number

* Mobile Station Roaming Number:

* Location Area Identity:

* Temporary Mobile Subscriber Identity (TMSI)

* Local Mobile Subscriber Identity (LMSI)

* Cell Identifier (CI):

THE GSM NETWORK:

The GSM technical specification defines the different entities that form the GSM network by defining its functions and interface requirements.

The GSM Network can be divided into 4 parts:

* The Mobile Station (MS)

* The Base Station Subsystem (BSS)

* The Network and Switching Subsystem (NSS)

* The operation and Support Subsystem (OSS)

Ref: www.kemt.fei.tuke.sk/.../OVERVIEW/overview.htm

Mobile Station:

The mobile station comprise of two main elements:

* The Mobile Equipment or Terminal.

* The Subscriber identity Module (SIM)

The Base Station SubSystem:

The BSS connects the Mobile Station and the NSS. It is in charge of the transmission and reception. The Base Station Subsystem is composed of two parts:

* The Base Transceiver Station (BTS)

* The Base Station Controller (BSC).

These communicate across the standardized Abis interface, allowing (as in the rest of the system) operation between components made by different suppliers. The radio components of a BSS may consist of four to seven or nine cells. A BSS may have one or more base stations. The BSS uses the Abis interface between the BTS and the BSC. A separate high-speed line (T1 or E1) is then connected from the BSS to the Mobile MSC.

The Network switching system (NSS), the main part of which is the Mobile Switching Center (MSC), performs the switching of calls between the mobile and other fixed or mobile network users, as well as the management of mobile services such as authentication.

Network Switching system architecture Figure 1.2

Opeartion and Support Subsystem:The element of GSM network architecture which connects with NSS and BSC is called as operation support subsystem.The overall GSM network is monitored and controlled by NSS subsystem and also controls the traffic on BSS.

2.3 Enhanced Second Generation Digital Cellular and PCS/PCN(2.5G)

2.5 G System – This generation is divided into two parts : Low two-and-a-half generation (L 2.5G) and High two-and-a-half generation (H 2.5G). The Low and High relate to the air interface.The effort to remove the impediments of 2G systems resulted in 2.5G cellular communication system. It was also a digital system with low voice and data-rates but having better modulation techniques. The major impetus for 2.5G is the "always-on" capability. Being packet based, 2.5G technologies allow for the use of infrastructure and facilities only when a transaction is required, rather than maintaining facilities in a session like manner. This provides a tremendous infrastructure efficiency and service delivery improvements.

* CDMA 2000's 1xRTT is the first technology for the evolution of CDMA one 2G network to 2.5G networks.

* During the evolution process from 2g GSM network to 2.5G networks GPRS (General Packet Radio Service) represent the first packet-based technology in cellular system.

* There are another two GSM 2.5G packet technologies,first Enhanced Data Rates for GSM evolution (EDGE) and for technology that is circuit based, High speed circuit switched data(HSCSD).

The 2.5 G system uses packet technology in thier core network and the ability to support wider range of data.The cellular system using these technologies based on the same the same infrastructure and the same frequencies as the 2G systems and usually coexist using the same core network.In these common systems, the 2G usually carries the voice service and the 2.5G system carries the data as an overlay system.Examples of these kinds of overlay systems are: GPRS and EDGE.

Main technologies of this generation:

* Low 2.5 G: GPRS, HSCSD, IS136+, IS95+;

* High 2.5 G: EDGE, 1xRTT (where 1xRTT stands for 1x (single carrier) radio Tranmission).

HIGH SPEED CIRCUIT_SWITCHED DATA (HSCSD):

High Speed Circuit-Switched Data (HSCSD) was developed to overcome the limited maximum user data transfer rate of 9.6 kbps in the original GSM system.The higher data transfer rate can be achieved by combining more than one traffic channel (TCH/F) for data services.The maximum HSCSD data transfer rate on the GSM system is 64 kbps but it is possible to increase it by 2—4 through the added use of GSM data compression technology (using the V.42 bis GSM algorithm).(Harte.,et.al, 2002)

The HSCSD network primarily involves an upgrade to the network software and an addition of gateways that allows conection to data networks (such as the internet).The required upgrade include enhancement to mobile telephone's software, and an interworking function (IWF) between the MSC and the data network.

Book-3G wireless demystified

By Lawrence Harte, Roman Kikta, Richard Levine

General Packet Radio Service (GPRS):

GPRS is a new feature of GSM that provides the capability of the packet mode transmission of user data and signaling information using the existing GSM network and radio resources.In this service it is available with GSM phase 2+ that enables multiple users to transmit packet data over a single slot.Each physical channel is shared by multiple users.The channel access mechanism has been optimised for intermittent, short burst as well as large volumes of data to be transfered within about 0.5 to 1.0 seconds for reservation request.It supports both IP and X.25 protocols and real-time as well as non real-time data.Both point to point and point to multipoint communications are possible.There is no restrictoin on the transfer of SMS message over GPRS channels.(Karim.,et.al, 2002).

In packet switching it is neccesary to use a set of data comunication protocols so that the transmission is efficient and error free.Usrs are allowed to request a desired quality of service (Qos) from the network. However only limited number of Qos profiles is supported.Different modes od operation are possible.In another mode it can only recieve a GPRS service.In the third mode, mobile station monitors control channels of both GSM and GPRS, but can recieve services only from only one of them at a time(i.e either a voice or packet mode data).

GPRS Network Architecture:

GPRS is a data network that evolved from second-generation GSM data overlay network which provides packet data transport at rates from 9.6 to 171 kbps. Additionally, the resources of air interface can be shared by multiple users simultaneously.

Following is the GPRS Architecture :

GPRS architecture figure 1.4

Ref:http://www.tutorialspoint.com/gprs/gprs_architecture.htm

GPRS built on same existing GSM network architecture so it attempts to reuse the existing GSM network elements,but to provide better handling of network elements, protocols and interfaces effective packet-based mobile cellular network is required therefore, GPRS requires modifications to numerous GSM network elements as summarized below:

GSM Network Element

Modification or Upgrade Required for GPRS.

Mobile Station (MS)

New Mobile Station is required to access GPRS services. These new terminals will be backward compatible with GSM for voice calls.

BTS

A software upgrade is required in the existing base transceiver site.

BSC

The base station controller (BSC) requires a software upgrade and the installation of new hardware called the packet control unit (PCU). The PCU directs the data traffic to the GPRS network and can be a separate hardware element associated with the BSC.

GPRS Support Nodes (GSNs)

The deployment of GPRS requires the installation of new core network elements called the serving GPRS support node (SGSN) and gateway GPRS support node (GGSN).

Databases (HLR, VLR, etc.)

All the databases involved in the network will require software upgrades to handle the new call models and functions introduced by GPRS.

GPRS Mobile Stations:

Previous GSM mobile phones cannot handle GPRS air interface data so new mobile station required with enhanced capabilities.For example PDA devices embedded with GSM phone, and backward compatible phones for making voice calls using GSM.

GPRS Base Station Subsystem:

A Packet Control Unit (PCU) is required in BSC with some software upgrades for packet data traffic which provides logical and physical interface to the base station subsystem.The BTS can also require a software upgrade but typically does not require hardware improvements.

voice or data traffic it is transported over the air interface to the BTS which is either originated at subscriber mobile or any other device, and transmitted from the BTS to the BSC in the same way as a standard GSM call. However, at the output of the BSC, the traffic is separated; voice is sent to the mobile switching center (MSC) per standard GSM, and data is sent to a new device called the SGSN via the PCU over a Frame Relay interface.

GPRS Support Nodes: Following two new components, called GPRS support nodes (GSNs), are added:

Gateway GPRS support node (GGSN): It acts as an interface and a router to external networks consists routing in sequence for GPRS mobiles, used to tunnel packets through the IP based internal backbone to the correct Serving GPRS Support Node.

Serving GPRS support node (SGSN): Mobile authentication registration collecting information for charging for the use of air interface and for mobility management functions Serving GPRS support node is used.(www.tutorialspoint.com).

Internal Backbone: The internal backbone helps sending information, carrying packets across different GSNs.Their is no need of any information about domain outside the GPRS network because tunneling is used between SGSNs and GGSNs.Signaling from a GSN to a MSC, HLR or EIR is done using SS7.

GPRS Protocol Stack: Following diagram shows the GPRS protocol stack and end-to-end message flows from the MS to the GGSN. The protocol between the SGSN and GGSN using the Gn interface is GTP. This is a Layer 3 tunneling protocol.

In this like a normal sub-network application communicates using standard IP, the data pass out through the gateway GPRS and recieve through GPRS network.

GPRS tunneling protocol is used for data transmission between GGSN and SGSN so the internal backbone network is limited to its perimeter area and nothing to do with IP addresses outside the GPRS. This GTP is run over UDP and IP.

A combination of SubNetwork Logical Link Control Dependent Convergence Protocol and is used Between the SGSN and the MS. Data compresses to decrease the load on the radio channel is done with the help of SNDCP on the other hand for the encryption of packets, safe logical link is provided by LLC. When the mobile moves to a routing area that lies under a different SGSN the LLC link is removed and a new link is established with the new Serving GSN X.25 services are provided by running X.25 on top of TCP/IP in the internal backbone.

GPRS Quality of Service

The Quality of Service QoS is very important characterstic in GPRS because necessities of typical mobile packet data applications are very dissimilar. For example diiferent GPRS applications such as e-mail transfer, Web browsing and realtime multimedia need a different QoS support. GPRS defines QoS by using following parameters are described below:

Service Precedence: The service precedence is the precedence of a service in relation to another service. There exist three levels of priority: high, normal, and low.

Reliability: The reliability indicates the transmission characteristics required by an application. Three reliability classes are defined, which guarantee certain maximum values for the probability of loss, duplication, mis-sequencing, and corruption of packets.

Delay: The delay is defined as the end-toend transfer time between two communicating mobile stations or between a mobile station and the Gi interface to an external packet data network.

This includes all delays within the GPRS network, e.g., the delay for request and assignment of radio resources and the transit delay in the GPRS backbone network. Transfer delays outside the GPRS network, e.g., in external transit networks, are not taken into account.(www.tutorialspoint.com)

Enhanced Data Rates for GlobalEvolution - GSM EDGE

Enhanced data for GSM evolution is a medium speed packet data communication system that is integrated with global system for mobile (GSM) radio system. The EDGE system modifies the GSM radio channel by adding new phase modulation and channel coding processes. EDGE uses several 8 level phase shift keying (8PSK) to increase the radio channel data transmission rate to 604.8 kbps (474 kbps user rate).

This diagram shows how a standard GSM radio channel is modified to use a new, more efficient modulation technology to create an a high-speed packet data EDGE system. The EDGE system users either 8 level quadrature phase shift keying (QPSK) modulation or the standard GMSK modulation (used by 2nd generation GSM systems.) This allows EDGE technology to be merged on to existing GSM systems as standard GSM mobile telephones will ignore the EDGE modulated time slots that they cannot demodulate and decode.

Enhanced Data Rates for GSM Evolution - GSM EDGE Figure 1.6

Refhttp://www.wirelessdictionary.com/wireless_dictionary_GSM_EDGE_definition.html

Beyond GPRS, EDGE takes the cellular community one step closer to UMTS. It provides higher data rates than GPRS and introduces a new modulation scheme called 8-PSK. EDGE is also being adopte by theTDMA community for their migration to

EDGE protocol stack figure – 1.7

2.4 Third Generation 3G/IMT-2000 Standards

In 1992 (ITU) International Telecommuniucation Union a leading agency, deals with communication and technology issues started working on standard IMT-2000 International Mobile Telecommunication with 16 different protocols. IMT-2000 was the first step toward 3G cellular systems and this was the first time that full interoperability and internetworking of mobile system could be achieved.IMT-2000 came up with lots of texture for example mobile, voice, data, and internet and multimedia services.but one of its key vision is it facilitates the user to move across the borders while using the same number and handset; i.e seamless global roaming and delivery of services.IMT-200 is a CDMA based standard which encompasses three different modes of operation: W-CDMA, CDMA-2000, and Time Divison Duplex and with some optional components of W-CDMA. The two technologies always remain pitted against each other while W-CDMA was dominant and gained most of the attention from corporate world beacuse of its emphasis on global roaming and promising economies of scaleTiming and cost of the technology remain as drawbacks. Below, in the table, is a summary of the family of five sets of 3G IMT-2000 wireless standards approved and published by ITU on May 2000.

Wireless evolution UMTS Figure 1.8

http://www.telenor.com/telektronikk/volumes/

Three IMT-2000 modes are based on Code Division Multiple Access, a system that enables many users to share the same frequency band at the same time. CDMA codes are chosen so that they cancel each other out. For exact cancellation, signals must be perfectly timed; base stations need to make very precise measurements of their time and location. They do this by using signals from Global Positioning System (GPS) satellites, which can pinpoint anywhere on Earth to within four meters and measure time more accurately than the Earth's own rotation. The only CDMA system in use so far is cdmaOne developed by Qualcomm but now supervised by an independent organization called the CDMA Development Group (CDG). It has been standardized by the Telecommunica-tions Industry Association (TIA) as IS-95A, and is popular among cellular operators in America and Asia. Because it already uses CDMA, it is easier to upgrade to 3G compared to rival systems based on Time Division Multiple Access (TDMA).

2.5 Fourth Generation

As technology is growing ures started demanding more integration the use of wifi directly from there cell phone slowly the cellular network would become data network which on which cellular phones could operate as well as any other data device Sending data overthe cell phone network is a lucrative business. In the information age, access to data is the "killer app" that drives the market.

Almost all of the major cell phone networks already providing data services beyond that offered in standard cell phones but the current cellular network does not have the available bandwidth necessary to handle data services well.The reason for the transition from 3G network to 4G is because not only the data transfer is slow at the speed of the analog modem but the bandwidth that is allocated is not allocated efficiently for data. An important reason is 3G systems are made as an improvement on the protocol that was originally designed for voice system not for data transmission and because of the inefficency of the available spectrum bandwidth a data centered protocol is needed.

Worldwide Interoperability for Microwave access (Wimax)

Worldwide Interoperability for Microwave Access (WiMAX), and it is also called as IEEEname 802.16.WiMAX has the potential to do to broadband Internet access what cell phones have done to phone access.WiMAX could replace cable and DSL services, providing universal Internet access just about anywhere you go. WiMAX will as painless as Wi-Fi i.e. turning the computer on will automatically connects to the closest available WiMAX antenna

In practical terms, WiMAX would operate similar to WiFi but at higher speeds, over greater distances and for a greater number of users. WiMAX could potentially erase the suburban and rural blackout areas that currently have no broadband Internet access because phone and cable companies have not yet run the necessary wires to the remote locations.

A WiMAX system consists of two parts:

A WiMAX tower, similar in concept to a cell-phone tower - A single WiMAX tower can provide coverage to a very large area -- as big as 3,000 square miles (~8,000 square km).

A WiMAX receiver - The receiver and antenna could be a small box or PCMCIA card, or they could be built into a laptop the way WiFi access is today.

A WiMAX tower station can connect directly to the Internet using a high-bandwidth, wired connection (for example, a T3 line). It can also connect to another WiMAX tower using a line-of-sight, microwave link. This connection to a second tower (often referred to as a backhaul), along with the ability of a single tower to cover up to 3,000 square miles, is what allows WiMAX to provide coverage to remote rural areas.

WiFi-style access will be limited to a 4-to-6 mile radius (perhaps 25 square miles or 65 square km of coverage, which is similar in range to a cell-phone zone). Through the stronger line-of-sight antennas, the WiMAX transmitting station would send data to WiMAX-enabled computers or routers set up within the transmitter's 30-mile radius (2,800 square miles or 9,300 square km of coverage). This is what allows WiMAX to achieve its maximum range.

WiMax Figure 2.1

http://communication23.blogspot.com/2008/08/global-positioning-system-technology.html

Ultra Wide Band (UWB)

Ultra Wide Band technology is loosely defined as any wireless scheme that occpies a bandwidth of more than 25 percent of a cemter frequency, or more than 1.5 GHz.The first UWB should be able to deliver bandwidth in the 40 to 60 Mbps range with expectation of very high transmission speed from 100 to 500 Mbps across a distance of 5 to 10 meters.UWB devices send and recieve relatively short range, high speed transmissions.UWB devices can be used to provide connectivity in home and office WLAN and provide short distance connection among mobile devices.

In addition to communications, UWB technology has other significant applications.It relies on razort thin, precisely time pulse similar to those used in radar applications.UWB precision pulse can be used to determine position of the emitters indoors acting as a local version of Global Positioning System (GPS)

CHAPTER 4 SECURITY OVERVIEW

In the world of modern technology the mobile operators, just not have to provide callular voice services but also they have to provide high-speed internet IP-based data services.As a result 3G networks are not only exposed to all the dangers from outside world but also mobile specific viruses and trojans, as well as direct attacks such as Denial of service (DoS) on thier network from hackers and criminal organisation.

3G network architecture is more IP-based so as to provide better connectivity and different services such as voice over IP (VoIP) intergration is much needed, moreover it is significantly faster than 2.5 G network(CDMA EV-DO) which provides 700 kbps downloading rate and peak speed up 2mbps where 3G is much more higher.But for IP-based services there is more traffic on celular networks when the users with more varied data-capable devices accessing and communicating with each other simultaneously across different networks.As majority of 3G devices are open to outside world such as MMS, internet, e-messaging, browsing, network based games etc. And because of this there are more element of vulnerability.Mobile data networks can be divided into 2 parts:-

Interconnected networks – mobile operator network, public internet, private networks content servers etc;

Multidevice type networks – windows mobile based phones, symbian smartphones, PDA, Laptops and data-capable featured phones.

In the recent times most of the mobile operators are leaning towards IP-Multimedia Subsystem (IMS) architecture.IMS is an architectural framework that use to deliver ip-multimedia services.It uses open standard IP-protocols to create communication link between variety of users for example between two users on internet; betwen internet user and IMS user or multimedia session between two IMS users.IMS is another reason that can create security loop-hole in a 3G network environment.

Since the transition occured from 2G to 3G the technological advent is far more essential but it is not possible to deploy entire new network but instead leveraging the existing 2.5g network infrastructure (GSM/GPRS/EDGE or CDMA 1x) equipment and backbone network for example, UMTS cell sites can be collocated in GSM cell sites much of the GSM/GPRS network can be re-used .The service GPRS support node needs to be upgraded, but the Mobile Switching Center(MSC) only requires a minor upgrade and the Gateway GPRS support node (GGSN) can remain the same.

Types of Attacks

Denial of service (DoS):-

Denial of service Currently one of the most prevalent threat is a distributed denial of service(DDoS) attack.It actually uses a brute force(a trial and error method in order to find legitimate authemtication credentials) to compromise target sysem sensitive information.For this kind of damage it requires enough traffic that often referred to as botnets, botnet are the group of computers that have been compromised by the attackers, generally with the help of malware disguised or embedded with softwares which can controlled by the attacker.

Overbilling attack:-

When an intended malicious user hijack a subscriber's IP address and then use that connection for its oen purpose.In either case, the bill will be filed in the name of subscriber for the unauthorised activity which was not conducted by the user.

Spoofed PDP-Context:-

This type of attacks exlpoit weakness in GTP (GPRS Tunneling Protocol).

* GTP packet flooding, which is a kind of DoS (Denial of Service) attack.

* Spoofed deleted PDP context could end user's service interruption or service loss.

* Spoofed create PDP context could provide illegal or unauthorised access to the internet or customer data networks.

Signaling-level attacks:-

The session initiation protocol (SIP) is used to provide Voice over IP services(VoIP) in IMS networks, SIP-based VoIP systens could consist of several well-known vulnerabilities for example the vulnerability in the Call Manager function that handles call routing and call signaling in VoIP systems and this can attract or allow attarckers to:-

* Gain access to individual user's account information by reconfiguring VoIP settings.

* Eavesdrop in VoIP communications.

* Hijacks end user's subsequent communications or voIP subscription.

6.1 PROVIDING SECURITY TO THE ENTERPRISE

Security is very important issue because of the fact that all the data passes over the air and can be easily captured or viewed by any legitimate anauthorised user with the right kind of software.Secondly,in a wireless environment an open access point is a perfect way for an attacker to gain access of unprotected wireless network without findind passage though the firewall.The impact of succesful attack on an organisation could result in multiple dangerous outcomes.Weak encryption protocols and ineffective security offerings have forced corporations to investigate add-on solution to roll out loop-holes in secure environment, while 802.11i standard(i.e) ,Wii-Fii protected access (WPA) as well as propreitary solution appear to finally include security in the configuration of WLAN, but still all these are not enough because the vulnerability can be easily appeared.For this reason it is important to improve and provide a well structured secure model environment which include – layered security, auditing , policy management, vulnerability assesment and enforced practise to prevent the compromising wireless network.

Structured and Layered Security Model:-

The objective of layered security is to effectively neutralize all incoming threats and to implement a variety of controls to maximise security inputs. All handheld devices must pass through different tests for leasing information moving in and out of the network.These layers consist of physical, administrative, and technical safeguards.The effectiveness of this model must extend to all devices, whether located on the company network, at home, or at a customer site.

Elements of Layered End-user Device Security:

Layered security.

www.securitydocs.com/library/3188

Carrier Security carrier security works on the following well defined operational security program:-

It keeps all the handheld operating system (OS) up to date in order to take advantage of improved security technology, such as firewall, code signaling etc.

Keeps on cheking and filtering unwanted activity, including known and unknown and also provide strong encryption.

Management Support Managment support is a foundation of any security program.It can be effective policies, adequate budgets, and consistent enforcement.

Security Program A security program of an organisation consist of policies and procedured as it underlines the securty objectives of the network. A security program policy consists of three elements:

* Purpose – It defines the objective of a security program that is intended to achieve and also it should reflect management commitment to secure enterprise.

* Scope – Its main purpose is to keep on checking all the activities affected by the policy and the technology in the enterprise.

* Compliance – It defines the consequences if the policy is not followed.

Procedures are the group of administrative physical and technical controls that provide security to its organisation.

User Awareness At many points end user can be a great vulnerability to the company's security policy.In order to avoid this security training program should be provided to all its members including:

Review of policies

* Procedure implementation.

* Password protection.

* How to deal with social engineering attacks.

* Ensuring the information on a handheld device is absolutely necessary.

* Ensuring the information on a handheld device is also stored on the company network where it is regularly backed up.

* How to encrypt sensitive information.

Enhancing new hire direction should begin with user awareness.Annual taining must be provided to the employees atlest once, in addition to formal training, daily reminders should be everywhere in the workplace; posters and login messages and physical security awareness.

Physical Access Controls Physical access is very strong and effective measure inorder to provide security to the organisation.weak passwords, biometrics, and other logical access methods can easily associated with the theft or loss of critical and sensitive information.So it is very inportant to secure the device when they are not in use.

Logical Access Controls Logical access controls inculde authorization, authentication, biometrics and token.To prevent the unauthorise access to unauthorise user to prevent gaining access to any infornmation which they have no permisison, logical access controls being implemented.

Finally, it is a good idea to combine password controls with another access control, such as biometrics. This is known as two factor authentication. If a password is compromised, the second control will help stop unauthorized use of system resources.

Personal Firewall A personal firewall is a software program that helps protecting internet connected system from intruder.Firewall is installed and administered on end users device. It acts as first line of defence against penetration attacks.The functions of a personal firewall program includes:-

* To filter amd block incoming suspicious traffic.

* To filter out going meassages that can effect valuable information of an organization.

* Also to prevent against penetration attacks by hiding the logical parts from unauthorised users.

Antivirus Software It is a utility for preventing and remove trojan horses these are the small programs or scripts written by legitimate unauthorise user in order to gain control access.

Host-based IPS Host-based IPS is a intrusion prevention system which attack is detect suspicious traffic, it can drop the offending packets while still allowing all other traffic to pass.host based IPS is a layer of protection that attempts to catch activities not blocked by the layers lower in the security model pyramid. These activities include, but are not limited to:

* Deleting files

* Moving files

* Copying files

* Installing executable files

* Registry modifications

* Denial of service processes

Version Management Version management is a set of policies, processes, and tools employed to ensure that all handheld devices are at proper operating system level.Fuction of version management includes:

* Checking vendor resourse for new OS release.

* Checking devices for current OS level.

* Applying OS update as appropriate.

Device Configuration:Its very important to train users to provide security awareness for handheld device used in enterprise network. However, companies must assist in this effort by locking down these devices through the use of centrally managed device policies. Device policies should be set in a system at the corporate office and automatically distributed and enforced.. Policies you should strongly consider include:

* Forcing the use of a password to access the device

* Forcing the user to enter contact information so the device can be returned

* Ensuring that all devices require end-user authentication.

* Shutting down any service not required for proper operation, including Bluetooth capabilities

* Controlling device configurations through the use of standard system settings that are locked to prevent modification.

* Using the security features included in the operating system to restrict access to information, including encryption

* Erasing all data on a handheld device when certain conditions are met

* Automatic checking of each device to ensure it meets certain criteria, such as running antivirus software, before granting it access to the network

* Requiring wireless access to the company network only through approved, secure paths (www.infosecwriters.com)

Public Wireless Access After having deployed the wireless solution within the network, it will not be long before vendors, contractors and other non-company personnel get connected to it. This type of request can be accomodated while maintaining the posture of the corporate wireless network. To accomplish this aaccess point could be located outside the network with the ability connected to the internet.This ca be done with awireless DMZ and secured basically as an internet DMZ. But it depends on the company policies, one may want to restrict the websites and the connections are allowed to go to.

Auditing Persistent auditing of all the systems in WLAN shoild be performed for forensic purposes as well as management and planning of the environment.Simply monitoring the bandwidth on the WLAN and the number of clients connecting to the WLAN may provide a warning if there is suspicious activity. Auditing the authorization server is crucial because it provides access to the internal network from the largely untrusted segment.To preserve the information in these types of log files, they should be removed from the devices on regular basis and stored in a secured place.

Policy management and enforcement Enterprise security policy has always been foundation of solid security program.Thw wireless security policies details that who is allowed to access the organisation's WLAN, and how that access. Many well planned and well designed programs fail to realize their potential beacuse of the inability to secure positive and sustained support from an organisation's employee and non employees.

Concept and principles The best practise in esablishing how to secure the enterprise are documented in the policies procedures and guidelines.This dictates how data and assets are secured, outlining from high conceptual level down to a detailed bits-and-bites level.However it is adviseable to have policies that are implemented that states the key points:

* Vendors must follow the organisation's information security policy

* The vendor must demonstrate that it has sound information security policy.This could be a check-off item during the vendor RPF pocess.

InternetProtocol security(IPSec)

What is IPSec: IPsec was developed by IETF, is a set of IP network protocol securing IP communciation by encryption and authentication of data packet moving within the network.Ipsec suite is an open standard framework for different protocols used by Ipsec to execute various functions:

Internet Key Exchange (IKE and IKEv2) its function is to generate the encryption and authentication keys and also set uo security association by nandling negotiation of and protocols.

Authentication Header: data origin identity of IP datagrams and connectionless integrity is provided by Authentication Header.

Encryption Security Payload: Its main function is to provide data confidentiality and also connectionless integrity and data origin identity

Vodafone UK case study:

Vodafone UK uses IPsec to provide secure connection to the corporate network via IPsec tunnels which helps cutomers using existing internet connection for this type of secure connection. IPSec has been deployed widely to implement Virtual Private Networks (VPN's) which allows any user to get acontrolled access to internet without purchasing a leased line.

vodafone using IPSec provides following security:

Data Confidentiality: The IPSec initiating node encrypts packets before transmitting them across the public internet.

Data Integrity: The IPSec receiving node authenticates packets sent by the IPSec sender to ensure that the data has not been altered during transmission.

Data Authentication: The IPSec receiver authenticates the source of the IPSec packets. This service is dependent upon the data integrity service.

IPSec can be terminated on CPE or on vodafone router managed by vodafone or either via the VPN tunnel itself or through the dialin ot of band analog modem connection.

www.vodafone-dataworld.co.uk

IPSAR In aconverged packet network vodafone uses IPsec aggregation router to provide reliability in the corporate network.

Vodafone implemented two physical routers one as primary other as a backup,and all the corporate traffic is managed within the network. A Public IP is provided to virtual router so in any case if router failure occur the traffic will transfer to the backup router.

www.vodafone-dataworld.co.uk

The Internet

When an Internet Service provider (ISP) provisons internet connection to the customer, it also provides a network termination device (Router) from customer site to the internet.Each ISP interconnects with other ISP's to provide internet access to the customers and gurantee a level of service.

Vodafone Data Fixed Link service

VodaFone secure data fixed link service is a circuit between Customer Premises Equipment Router and Vodafone UK dedicated service provider(Cable & Wireless).

When a cutomer require service, a secure circuit is provided whether it is directly to the customer premises or either the service managed on the data center.The solution provided by vodafone can be either single site (single link) or resilience passive fixed line.

Overview

Vodafone fixed service uses MPLS (Multiprotocol label switching) across the core network, fixed link solution is called strategic connectivity, as VPN(virtual private network) connetcivity between dedicated service provider and Converger packet netwrok.

The Scenario relies on Cisco 12000 router for IP-MPLS interconnected between cable-wireless and vodafone uk network also different types of cisco CPE's router has been used.The main attention is given on secure remote access and protection from outside world.

Doc ref: GPRS/PRO/0000

www.vodafone-dataworld.co.ukcol

QUALITATIVE ANALYSIS

SYSTEM COMPARISON - network and protocol architecture of principle 3G based wireless standards: UMTS and CDMA2000

3G systems developed in order to provide global mobility and wide range of services such as internet broadband data, telephony, messaging. International Telecommunication Union (ITU) started the process of defining the standard for third generation systems, referred to as International Mobile Telecommunications 2000 (IMT-2000)and as a standard it is developed for 3G mobile communication services being specified by 3GPP.The radio access components of UMTS are based on direct-spread wide band code divison multiple access (WCDMA), method that have been defined for 3G frequency efficiency, mobility and QoS requirements.

The network architecture defines all the parts of the network elements and its physical with the existing network elements. It describes about the functionality of each network element and their interaction with other network elements in the whole scenario.

Universal Mobile Telecommunication System (UMTS) :

UMTS uses a wideband CDMA (W-CDMA) technology for transmission, which allows UMTS to reach higher utilization, and offer higher bandwidth to end user. UMTS offers bit rates up to 2Mbps for users.Basic structure of UMTS network: A UMTS network can be divided into three basic subsystems,

User Equipment (UE) The user equipment is the physical device used by the subscriber to access servies provided by the network.It consists of UMTS Subscriber Identity module (USIM), USIM is small chip that interoperates with the Mobile equipment in order to provide 3G services to the subscriber.Uu inteface is used as a connection point between UE interface and Access network using WCDMA air interface and it uses two modes to operate: the Frequency Duplex (FDD) mode for paired spectrum and Time divison duplex(TDD) for unpaired spectrum.

Access Network(AN) AN acts as radio bearer between User Equipment and Core network. The function of the accsess mode is specific to Radio access technique i.e it perform function specific to the WCDMA air interface.Access network consist of two type of entities – Base transceiver station(BTS) and the Base station controller (BSC).

Core Network(CN) the function of core network is to provide mobility management , call control, switiching and routing, authentication and equipment identification.The core network also manages subscription information of a subscriber and provide services based on this information.The core network is divided into two parts or domains:

* Circuit switched domain (CS) the CS domain uses circuit switched connections for communication between User equipment(UE) and the destination.In circuit switched connection , network resource is allocated for the time when connection is established and terminated for when network resource is unallocated for example connection during the telephone conversation in the PSTN network.

* Packet switched domain (PS) uses packet switched connection for communication between UE and destination.Packet switched connection is defined as connection which transports the user information using bits called packets and each packet routed independently from the previous one.

Interfaces In UMTS: In UMTS standard interfaces are defined by Interoperation between different nodes of the UMTS :

* The Uu between UE and UTRAN, based on WCDMA.

* The Iu between UTRAN and the CN.

* The Gn between the 3G – SGSN and the GGSN.

UMTS PROTOCOL ARCHITECTURE – The UMTS protocol achitecture divides different protocols into two planes, user plane and control plane.UMTS protocol model can be defined as three layered model:

Transport network layer: its function as to provide transport to all the UMTS elements in the networks.

Radio network layer: Providing internetworking between core network ang mobile stationwhich also related to the radio bearer service.

System network layer: The function of system network layer is to help making connection between the tunnel and PDP context and also performs function related to mobility management data delivery and authentication.

USER PLANE: The user plane includes a group of protocols that actually initiates tramission of data.

UMTS User Plane has few changes than GPRS User Plane , the GPRS protocols in SGSN and BSS are designed in consideration of reusing the GSM infrastructure.Whereas the UMTS user plane is designed with careful layered architecture providing all the necessary control porcedures transfer along the user plane.These control procedures are flow control and error recovery. The protocol transparency towards the support of new protocols without changing existing structure of Radio network architecture is prvided by the Packet Data Control Protocol (PDCP) in RAN also the IP header compression is performed by PDCP which is then passes data packets to RLC .The Ciphering function of Logical link control(LLC) moved to Radio link control (RLC) and Media access control (MAC). For the WCDMA interface the Radio protocols are splitted into Radio network controller (RNC) and Node B.

Types of Radio Channels:

* Broadcast Channel.

* Control Channel.

* Shared Channel.

* Dedicated Channel

CONTROL PLANE: control plane manages to support and control the functions of user plane.Control plane also manages Sessions and mobility for services such as Short Messaging Service (SMS) where Session management consist of activation, deactivation and modification of PDP context.And GPRS mobility management consist of updates of data routing and scurity procedures.

GTP connections are managed by Radio Access Network Application part (RANAP), the main function of RANAP is encapsulation and to carry various protocol messages such as SMS,SM and GMM across RAN and SGSN.

RADIO RESOURCE CONTROL (RRC) – all the radio resource functions are managed by RRC protocol also provides most of the radio mobility management functions as handover, cell updates and radio link measurements.

Mobile Application Part protocol – Map protocol is the heart of the core network.It was developed specifically to gather the requirements of a mobile network environment.The function of MAP is to allow mobile service applications in the networks to communicate with each other on different nodes.Map is an application layer protocol which is used to access application center, home location register, visitor location register and serving GPRS support node.

The primary facilities provided by MAP are:

* Mobility Services: Authentication, location management (roaming managing) service subscription information, fault recovery,

* Operation and Maintenance: subscriber tracing, retrieving a subscriber's IMSI

* Call Handling: routing, managing calls whilst roaming, checking that a subscriber is available to receive calls

* Supplementary Services

* Short Message Service

* Packet Data Protocol (PDP) services for GPRS: providing routing information for GPRS connections

* Location Service Management Services: obtaining the location of subscribers

MAP layer Achitecture MAP layer acts as a TCAP-user(set of communication capabilities that provides a generic interface between application and network service layer) and uses service and component sub layer of TCAP.In the coe network each of MAP layer user application performs a specific function which require exchange of MAP messages between the nodes.

MAP layer functions:

* Mobility management procedure

* Authentication procedure

* Call handling procedure

* IMEI check

* Subscriber Tracing procedure

* Fault recovery procedure

* SMS procedure

* Supplememtary service procedure

* PDP Context Activation procedure

GPRRS Tunneling Protocol (GTP)

GTP is the IP based tunneling protocol which carries General packet radio service (GPRS) to transfer data within GSM or UMTS networks.The GPRS Support Node(GSNs) uses GPRS Tunneling Protocol (GTP) to create a tunnel when the PDP context is activated in the PS (Packet Switched) domain , the packets are encapsulated and tunneled between the PLMN and also GTP provides data exchange between the tunnel.The communication is in the way that PDP and PDUs are encapsulated with the GTP header and exchanged using the UDP/IP protocol.

http://satellits.org/

GTP protocol is divided into two different parts:

GTP-U: In the user plane it helps carry user data packets with the use of encapsulation.It is used over the Iu_PS interface between SGSN and RNS also within the GSNs on the interface Gn,Gp.

GTP-C: It is used in the control plane for the signaling functionality in GTP and also for modification, deletion and creation of tunnels, mobility management is its another function to specify the location of mobile station.

GTP encapsulates all the PDU conveyed across the Gn/Gp interface in the GPRS backbone network.When the IP PDU tunneled through the GPRS backbone network allows to perform the signaling information exchange.For the control signaling and data routing UDP/IP protocols are used.

GTP Layer Achitecture

http://etutorials.org/

GTP Header: In GTP Header first 8 bytes are meant to be mandatory and the rest of the bytes are measured as a part of payload, GTP header consist of following:

http://www.protocols.com/pbook/UMTSFamily.htm

· Version: Indicates the first version of GTP (set to 0).

· Reserved: these are the reserved bits for the use in future (set to 1).

· LFN: Stands for LLC fame number indicates that the LFN is included or not set to 0 in signaling message.

· Message Type: In each type of signaling message it is set to a unique value indicating the type of GTP message.

· Length: It determines the length of GTP message (GTP-U) in octets.

· Sequence: It is a type of identity for signaling message.

* Flow Label:It explicitly defines the flow of GTP when flow of label not in use or 0 during signaling path management messages and location management messages.

· TID: It is tunnel identifier helps in pointing out mobility managment and PDP context it is generally set to 0 in all versoin management messages.

Code Divison Multiple Access (CDMA) – 2000:-

Code divison multiple access (CDMA) – 2000 is a hybrid 2.5G / 3G technology of mobile telecommunications that use CDMA (code division multiple access) to send digital radio, voice, data, and signaling data between mobile phones and cell sites. CDMA2000 is standardized by the 3rd Generation Partnership Project 2 (3GPP2). CDMA 2000 1xRTT access technology is used it is considered as 2.5G "1xRTT" designated as "1 Time Radio Transmission Technology" and CDMA 2000 EV-DO is considered as 3G system technology where EV-DO (Evolution-Data Optimized or Evolution-Data only), the mobile stations with this broadband access tecnology can receive speed upto 2.4 Mbps with Rev.0 and 3.1 Mbps with Rev.A

The purpose technical requirements contained in CDMA 2000 from a compatibility standard for CDMD systems which means that a mobile station can obtain service in a system manufactured in accordance within the cdma2000 standards. CDMA system architecture is based on MSC based circuit switched core and the radio access network is based on CDMA 2000 1x EV-DO. CDMA network architecture comprised of Access network, Packet Switched core network, circuit switched core network

http://www.networkdictionary.com/

The core network performs as a gateway between the intenet or intranet of a prviate corporate and the access network.It serves for the services such as Authentication, authorisation and accounting (AAA) and it also manages IP addresses, provide access to network services and IP mobility further the core network divided into two parts,

* Interfacing to external networks such as the public switched telephone network and

* Interfacing to the IP based network such as internet.

Core network entities :

Packet Data Serving Node (PDSN)/Foreign Node (FN):

PDSN provides the access to intranet, internet and various other servers (ex, aplication server) for the mobile stations which utilizing radio Access Network, it acts as the gateway between core network and access network.Authentication, authorization and accounting for the access to packet services and packet billing record informations all hadled by PDSN and the Foreign agent functions to handle encryption between Home agent and Foreign agent ; and packet routing information for mobile IP subscribers.

AAA/Home Agent :-

All the authentication, authorization and accounting for data services are done by Home agent and also the access information for billing and invoice purposes is stored in AAA Server.HA provides mobile IP addresses for Mobile stations and forwarding traffic to facilitate data roaming into other carrier networks and maintains dynamic IP address database, registration information with AAA.

PDSN: it assigns a dynamic IP address for using basic Internet service by the means of the Simple IP access method,which means (the service provider must assign the user a dynamic IP address so that the user can maintain constant IP while the user continue connection with the same IP network within a wireless carrier's domain and this consistency is untill the user is roaming in the same coverage area of the same Packet Data Serving Node (PDSN).However a new IP is been provided when the user moves to new geographical area which is further attached to another IP network) mobile terminates the user's PPP link, and forwards packets directly toward the Internet via the default gateway router on the service provider backbone IP network. To ensure the mobile is using the source IP address assigned by the PDSN normal PPP timers are enforced and also the packets from the mobile are identified. (Among other filtering rules and policies, the PDSN may implement in Simple IP mode.)

CDMA 2000 Protocol Architecture:

Third generation partnership project 2 (3GPP2) defines CDMA 2000 technologies and protocols, it is also called as IMT – 2000 multicarrier or IS 2000.CDMA 2000 provides one of the best enhanced services to its subscribers also the backward and forward capabilities in terminals.

For succesful IP connection a second layer of connectivity is required between the serving PDSN and mobile stationThis connectivity is provided by Point to point protocol(PPP) and the supporting protocols such as IPCP, LCP, PAP, CHAP.Point to point protocol is launched when negotiation process starts and also when terminated by PDSN.PPP traffic is encapsulated into Radio-Packet interface between CDMA 2000 network and PDSN.

http://etutorials.org/

Important network protocols in CDMA 2000 are described as follows:

Function between BSC and MSC:

* A1:Initiates signaling process for mobility management and call control.

* A2:Initiates traffic for circuit switched voice transmission.

* A5:Interface between BSC and MSC for circuit switched IP traffic.

Function between BSC and PSDN

* A10:Transmitting IP user data between PSDN and BSC.

* A11:Signaling between BSC and PSDN

Functions between BSCs/ANs/PCFs

* A3: User data and signaling between the source BSC SDU function and target BSC

* A7:Handover control signaling between BSC's target and source.

* A13:MM/SC function signaling between AN/PCF's target and source.

* A15:Inter-AN paging control signaling between AN's target and source.

Circuit switched protocols:

* C:MSC and HLR intermediate signaling.

* E:MSC and GMSC intermediate signaling.

Mobile IP based protocols and Interfaces:

* P-H1:Signaling between AAA and HA/FA.

* P-H:Transmitting Mobile IP user data application between HA and FA.

* A12:Helps transmitting signals between AN's AAA and AN/PCF.

RELIABILITY IN WIRELESS COMMUNICATIONS

In wireless communications QoS plays very important role and it is given maximum priority because subscriber today wants reliable connection in real-time scenarios, and it is undesireable to get low quality of services for paying high amount of bills.Initially, First generation (1G) and second generation (2G) cellular system was built for voice communication, therefore QoS in the voice transmission was the only aspect to deal with.But with 3G systems voice with data (IP) came in effect and for IP-multimedia applications at high rates, throughput, delay and availability of connection functionality is necessary.Still, voice services are considered as the primary service because of their real time requirements and delay sensitivity, whereas data services expect better throughput at less or no loss rate and also they are less delay sensitive.Simultaneous use of several applications raises the demands for mechanisms which can guarantee quality of service (QoS) for each application e.g speech, data, text and audio video supporting 3G network for better data transmission.

UMTS QoS Architecture: In UMTS end to end service connectivity is expected that means from one terminal equipment to another terminal equipment.Subscriber's demand for reliability and QoS for network services provided by this end to end service.

A Bearer service is needed to substantiate certain network QoS from the source to destination with clearly defined functionality and characterstics.Bearer service provides capability of trasmission of signals between two communicating devices.UMTS bearer service provides different services such as controlling signals, user plane transport and QoS management functionality, offered by UMTS operator, thus providing QoS.UMTS Bearer service layer architecture is defined as below:

Each bearer service depends on its sub layer offering specific service from individual layer below.

UMTS Bearer service is divided into two parts:

Radio Access Bearer Service : Radio bearer service helps providing user data transmission and transport signaling between mobile terminal and core network to negotiate with UMTS bearer service with adequate or default QoS.

Core Network Bearer Service: it connects UMTS gateway and Core network edge node to external network.To provide the subscriber UMTS bearer service, Core network bearer service controls and utilizes the Backbone network efficiency.

QoS Classes: UMTS QoS classes are defined to identify delay sensitivity of the traffic flow.

There are four classes in QoS architecture:

Conversational and streaming classes: Traffic in these classes are very sensitive to delay because they serve real-time traffic flow.The applications for conversational class includes speech, telephony, voice over IP, video confrencing.Whereas the stream in streaming class characterized by time relation information and application includes listen to or watching real time video etc.

Interactive and Background classes: These classes are defined for www, email, ftp type of traffic and because these classes are less delay sensitive and also by the means of channel coding techniques they provide better error rate and retransmission i.e whenever a packet loss/error or mismatch took place packet retransmission is done automatically.

CDMA 2000 QoS ARCHITECTURE:

Code Divison Multiple Access is a third generation technology and specificied feature of 3G systems as it offer a radio interface adapted for all kinds of services and combination of services (such as data, voice, video etc) for different standards. Multiplexing these services in terms of quality of service(QoS) is a big challenge with some critical problems can be represented as BER(bit error rate), processing delay, frame error rate etc. In the wireless world resources are limited as:

* Air interface limitations such as interference and limited system capacity.

* Battery life and backhaul is another problem.

For optimal control and usage of resources in QoS from OSI layer to physical layer are implemented by different mechanism and techniques.In IP networks E2E(End to end) QoS support is provided by packet data service in QoS networks and also the radio resource allocation is on the basis of per service instance.( Chaskar and Koodli,2005)

END TO END Service layer Architecture:

E2E QoS Service:To satisfy users application requirement guarantee CDMA2000 wireless IP network attempts to reserve necessary resources that are requested for QoS requirements.Request is passed to lower QoS level in case if the necessary resource is unavailable.Following figure shows different QoS bearer services:

E2E QoS Service: Signaling protocols such as SIP/SDP helps identifying application layer QoS between the end host.Network layer session is created between application layer for mapping QoS requirements and then the recieved QoS parameters are mapped to corresponding IP layer signaling parameters.

IP QoS Service:IP QoS service is used to control QoS at remote and local networks, Diff-serv to control backbone IP network.

Link layer service- This layer does not support any QoS capability.

External Bearer service: It is the service provided by external network for e.g wireless service providers do not own the IP core network.

Core network bearer service: Core network bearer service provided between PDSN/AGW and BR.

QoS Schemes in cellular networks: (Yang 2003)

Fault Tolerant Dynamic Allocation Scheme: This scheme defines the method of reusing channels effectively between two cells, which is separated by a minimum distance so that they do not interfere with each other thereby increasing the channel utilization and also the QoS.The channel allocation is done dynamically opposed to the static allocation.The channel allocation schemes can be approached distinctively as: Centralised and Distributed.

Centralised: In this, central controller sends request to another controller for channel allocation but central control is resposible for the allocation.

Distributed: It is more reliable and scalable and thus mostly used in cellular networks.In this, each cell consist of mobile service station (MSS) taking care of that particular cell for channel allocation.

According to the above model there are many cells comprised of Mobile Host (MH) and Mobile service station (MSS) and also the cells are connected to a fixed network.Mobile host has to request a channel from MSS whenever it wants to comunicates with another MH.If a particular wireless channel used concurrently more than one communication session in the same cell the signals can readily create co-channel interference, but the allocation of channels from MSS to MH is done when there is no such interference.

In distributed dynamic approach MSS is present in the cell without any central controller; main purpose is to allocate channel ensuring no interference. Cell updates are generated for neigbouring cells for this information if any cell wants a channel allocation, a request message is sent to all and then the channel can be used if its free for allocation.

Distributed Channel Allocation Algorithm:

It is called 3- cluster model, in this each cell has six nieghbours having unique identification from 1 to 6.Channel with highest frequency has maximum order and the channel with lowest frequency has the minimum order.None of the cell is pre-allocated to any channel previously.

if (i) wants to use a channel it sends request to all its neighbouring cells.prior to this Ci sets the timer and then sends a broadcast message to all the cells and waits till the timer expires.When a burrower (Ci) itself insearch of channel it does not repond to any query fro any other requesting cell.After time expires,It again sends signals to its neighbouring cells and burrows channels based on the reply it recieves.

From the above diagram, assuming cell Ci got reply from two neighbours, (1 and 4) and channel 'r' is allocated to both cells 1 and 4.Ci burrowed channel from 1and 4 but not from (2,3,5,6) due to this channel 'r' cannot be allocated to these channels to avoid co-channel interference.

Call Admission Control (CAC) Scheme [Kovvuri 2003]

In this scheme some calls are blocked irrespective of availability of channel and new arrival rates are estimated continuously which is higher than predetermined level.The purpose of this scheme is to maintain new arrival rates of incoming calls , lesser than previously programmed level.Call admission control algorithm is provided to ensure better QoS scheme. In the CAC algorithm the acceptable load is calculated based on simulation results and this value is used for comparison purpose. The estimated load is also calculated and it is checked with the acceptable load. If the estimated load is lesser than or equal to the acceptable load, then attempts are made to allocate channels for all the incoming calls. If the estimated load is greater than the acceptable load then only a fraction of the incoming calls will be allocated channels and the remaining fraction of the calls will be discarded even if there are available channels.

RESULTS AND DISCUSSION BETWEEN UMTS AND CDMA 2000

Although, commercially UMTS(WCDMA) is much more dominant technology than CDMA2000 but the connection to Public switched telephone network and Packet data network are quite similar in accordance to the usage of radio access interfaces and network entities in both the technologies.Focusing on IP networks in cellular system CDMA2000 technology evolved with more IP friendly architecture than UMTS(WCDMA) despite of the fact that both the system was built for high speed packet data and internet services but CDMA2000 performs inherently efficient in this context.

SIMILARITIES AND DIFFERENCES IN UMTS (WCDMA) AND CDMA 2000:

"From the beginning, critics warned that the compelling theoretical potential of CDMA would never prove out in the field; dynamic power control in rapidly fading environments would be its Achilles heel; interference would vastly limit capacity; systems under heavy load would be unstable; and power balancing would make infrastructure engineering a nightmare."

(Bill Frezza 2001).

Although the UMTS(WCDMA) AND CDMA 2000 standards were accepted by different standards organizations, similaties can be pinned out as many of their fundamental technologies are shared in their later revisons also both employ key design concepts of IS-95 (CDMA one).

(Emre A. Yavuz and Dr. Victor Leung, 2003).List of shared common technologies for CDMA 2000 and WCDMA:

* Direct Sequence Spread Spectrum: Both uses the same spread spectrum to improve spectral efficiency (system capacity).

* Random Access: to efficiently share radio access resources among all users, CDMA 2000 1X also supports reserve mode with power control whereas WCDMA performs access only on preamble with fast PHY acknowledgement and subsequent message transmission without power control.

* Soft/Softer Handoff:to provide handoff between users and base station supported by both of the standards.(WCDMA and CDMA 2000).

· Fast Uplink power control: to resolve the interference and the problems of near-far field effect.(www.qualcomm.com, 2006).

¾ WCDMA technology makes very efficient use of the available radio spectrum since one cell frequency re-use is applied so their is no need of frequency planning.On the other hand CDMA2000 1x can operate under higher interference level than WCDMA because of its advanced core network capabilities.

¾ CDMA 2000 uses architectural framework of CDMA one, after enhancement in the core network architecture the spectral efficiency of CDMA2000 1x permits high traffic and can provide voice capacity of nearly three times of CDMA one.

¾ One of the advantage of using WCDMA is that the users with this technology terminals can roam in WCDMA and GSM network without any switching delay because of its backward compatibility factor.

¾ In CDMA 2000 for higher bandwidth support two configuration options are defined:

* Direct Spread spectrum

* Multi-carrier spectrum

Although CDMA is the basis of the current 3G cellular systems use CDMA TDMA and FDMA are also used. Both the major schemes, UMTS and CDMA2000 have a limit on the number of users who are able to use a single channel. In some instances two or more channels may be allocated to a particular cell. This means that the system still uses an element of FDMA.

Additionally UMTS incorporates some timeslots, and this means that the scheme uses elements of TDMA.

While CDMA is currently the dominant technology, both the other forms of access scheme are still in evidence, not just in legacy technologies, but utilised as part of the main access scheme in the latest 3G systems. In addition to this, the new cellular technologies being developed for the 3.99G or 4G cellular systems use OFDMA, and this appears to be the technology of the future.

Summary:

In this dissertation number of methods have been imployed to demonstrate reliable transmission in secure wireless environment.Study of standard 3G technologies with examplary evaluation to provide productive results toward reliability and security with their limitations.

Chapter 1: I discussed the historical work and terminology in the field of mobile communication.Various tecnologies evolved during the evolution in wireless comunication, from 1G (AMPS, TACS), 2G(FDMA,TDMA,CDMA,GSM), 2.5G(GPRS) and 3G (UMTS,CDMA2000) to fourthcoming 4G(Wimax) are described briefly.

Chapter 2: Discussed security measures in todays wireless communiaction system, vulnerabilities and threats that can harm enterprise security architecture and providing layered security approach to eradicate risk.

Chapter 3: Analysed a comparative study between current (3G) technology UMTS and CDMA 2000, by thorough research on netwrk and protocol architecture modifications from previous technolgies and QoS specifications for both mobile standard with the results demonstrated an improved structure from past generations (2G and 2.5G).

In conclusion – The cellular network does not have available bandwidth to improve the data services and quality to transmission.Efficiency allocation for data system is needed where data transfer is very slow and sometimes the data transfer for voice tends to come in bursts rather than in constant stream.The cellular network system has been continuously growing with demand of users, different new protocols for faster access speeds and more efficient transmission being proposed day by day.However, the technology improvements are proceeding in different direction as many companies are developing standards of their own.Although similarities are evident in most of the technologies but protocol used are not same everytime.A data centered protocol acrhitecture provided by 3G, also inefficiency can be predicted in available spectrum bandwidth where mobile handset need dual or even tri-mode to operate with 3G interfaces.Although above inefficiency are prominent but technologies are still growing to provide up to mark caliberation.Dominant 3G Technologies like WCDMA and CDMA2000 makes very efficient use of available spectrum without any frquency planning.Following factors making 3G the 'Most Promising Technology':

* Data Transfer

* Multimedia Services

* Corporate Solutions

* Mobile Internet Access

* Multicasting Services

* Ubiquitous Network Coverage

Numerous opportunities are provided by wireless networking to increase productivity and cut cost, altering overall security risk in the organisation.Although it is important to eliminate all possible risk in wireless environment but some permeability is achieved by providing layered security architecture for accessing and manging risk.A study on Vodafone UK also provides a contrivance on how to mobilize enterprise security.

Future Recommendation:

Future of wireless communication would be the introduction of 4G wireless communication that is underdevelopment many countries looking forward for the latest technological adavncement.

A recommended approach to wireless security would be to use a layered approach with MAC filtering and

WPA or WPA2 at the access point. The use of IPSec and VPNs on the network and ensuring the machines on the

network are protected. Ultimately, it may be the best to follow the practice to put publicly accessible servers into

a Demilitarised Zone (DMZ) and put the wireless access point into a firewalled section of the network with rules

governing communications to the rest of the network; however until equipment for the home can support this, it

will remain a security weakness.

OFDMA - Orthogonal Frequency Division Multiple Access

OFDMA is the form of multiple access scheme that is being considered for the fourth generation cellular technologies along with the evolutions for the third generation cellular systems (LTE for UMTS / W-CDMA and UMB for CDMA2000).

As the name implies, OFDMA is based around OFDM. This is a technology that utilises a large number of close spaced carriers.

Orthogonal Frequency Division Multiplex (OFDM) is a form of transmission that uses a large number of close spaced carriers that are modulated with low rate data. Normally these signals would be expected to interfere with each other, but by making the signals orthogonal to each another there is no mutual interference. This is achieved by having the carrier spacing equal to the reciprocal of the symbol period. This means that when the signals are demodulated they will have a whole number of cycles in the symbol period and their contribution will sum to zero - in other words there is no interference contribution. The data to be transmitted is split across all the carriers and this means that by using error correction techniques, if some of the carriers are lost due to multi-path effects, then the data can be reconstructed. Additionally having data carried at a low rate across all the carriers means that the effects of reflections and inter-symbol interference can be overcome. It also means that single frequency networks, where all transmitters can transmit on the same channel can be implemented.

Heterogeneous System:

Glossary

A.1 Definition of terms and concepts

In order to understand the content of this dissertation, it is pertinent to define the most important concepts related to mobile computing and networking. With this purpose, the basic terminology is included in this appendix. The presented definitions are based on the following sources: IETF-RFC Mobility support for IPv6 [48], IEEE 802.20 Working Group documents [45], IETF Network Working Group Internet Drafts [58] and [91], and the RFC [107].

Access router

An access network router residing on the edge of an access network and connected to one or more access points. An access router offers IP connectivity to mobile hosts. The access router may include intelligence beyond a simple forwarding service offered by ordinary IP routers.

Base station

Also called access point, it is the point of attachment of a mobile node to the Internet.

Binding

The association of the home address of a mobile node with the care-of address of that mobile node, along with the remaining lifetime of that association.

Break-before-make handover

During a break-before-make handover the mobile host does not communicate simultaneously with the old and the new access router.

Care-of address

A unicast routable address associated with a mobile node visiting a foreign link; the subnet of this IP address is a foreign subnet prefix. 111

Context-aware handover

A handover that is governed by a certain specific requirement to be fulfilled while handing the connection between two access routers.

Correspondent node

A peer node with which a mobile node is communicating.

Eager cell switching

Node should switch to the new access router as early as possible, or as soon as thee mobile node receives a router advertisement from the new access router.

Fast handover

A handover that aims primarily to minimise delay, with no explicit interest inpacket loss.

Foreign network prefix

Any IP subnet prefix other than the mobile node's home subnet.

Foreign link

Any link other than the home link.

Handover

The act of changing the attachment point of a mobile node, switching the communications from one access point to another access point, also know as handoff.

Handover latency

Handover latency is the time difference between when a mobile host is last able to send and/or receive an IP packet by way of the old access router, until when the mobile host is able to send and/or receive an IP packet through the new access router.

Hard handover

A hard handover is required where a mobile host is not able to receive or send traffic to two access points simultaneously. In order to move the traffic channel from the old to the new access point the mobile host abruptly changes the frequency/time-slot/code on which it is transmitting and listening to new values associated with a new access point.

Home address

A unicast routable address assigned to a mobile node, used as the permanent address of the terminal.

Home agent

A router on the mobile node's home link with which the mobile node has registered its current care-of address.

Home link

The link on which a mobile node's home subnet prefix is defined.

Home subnet prefix

The IP subnet prefix corresponding to a mobile node's home network.

Horizontal handover

Also know as intra-technology handover, a handover between two cells (or access points) employing the same air interface technology.

Lazy cell switching

Node should stay connected to the same access router as long as possible.

Make-before-break handover

During a make-before-break handover the terminal can communicate simultaneously with the old and new access routers. This should not be confused with"soft handover" which relies on macro diversity.

Mobile node

A node that can change its point of attachment from one link to another, while still being reachable via its home address.

Movement

A change in a mobile node's point of attachment to the Internet.

Network domain

A grouping of network objects, such as computers, that simplifies the naming of

network services. Within a domain, all the names must be unique.

Policy action

It is the changing of the configuration of one or more network elements in order to achieve a desire policy state.

Policy agent

It is a software component that generates and responds to policy events, evaluates policies, and enforces policies.

Policy condition

It consists of two parts, a policy condition type and a policy condition element.

This structure is aimed at satisfying the need for a canonical representation of a policy condition.

Policy conflict

Occurs when the actions of two rules (that are both satisfied simultaneously) contradict each other. The entity implementing the policy would not be able to determine which action to perform.

Policy core information model

An information model describing the basic concepts of policy groups, rules, conditions, actions, repositories and their relationships.

Policy decision point

The component responsible for the policy decision process. Policy decision is the abstraction of activating and evaluating one or more policy rules. Each policy rule is interpreted in the context of a specific request for accessing and/or using one or more resources.

Policy enforcement point

The component responsible for the policy enforcement process. Policy enforcement is the action of placing the network (or a part of the network) in a desired policy state using a set of management commands.

Policy rule

A policy rule is comprised of a set of conditions and a corresponding set of actions.

This combination in effect defines a sequence of actions to be initiated when the corresponding set of conditions is either satisfied or not satisfied.

Policy translation

The transformation of a policy from a representation and/or level of abstraction, to another representation or level of abstraction.

Radio access technology

The radio access technology (i.e. air interface) is the radio-frequency portion of the transmission path between the wireless terminal (usually portable or mobile) and the active base station or access point.

Registration

The process during which a mobile node sends a binding update to its home agent or a correspondent node, causing a binding for the mobile node to be registered.

Return routability procedure

The return routability procedure authorises binding procedures by the use of cryptographic token exchange.

Roaming

The use of a communication device outside a specified administrative domain (home domain) defined by the service provider.

Seamless handover

A handover that is both smooth and fast, thus provides fast lossless handover between two access routers.

Smooth handover

A handover that aims primarily to minimise packet loss, with no explicit concern for additional delays in packet forwarding.

Soft handover

Support for soft handover (in a single mode terminal) is characteristic of radio interfaces which also require macro diversity (bicasting) for interference limitation but the two concepts are logically independent.

System

A collection of elements or components that are organised for a common purpose.

In the scope of this work, a communication system consists of hardware and software components that have been carefully selected so that they work well together.

Vertical handover

Also called inter-technology handover, a handover between two cells employing different air interface technologies.

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