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Computer Network: GPRS

Besar Dika 105088 Dashmir Istrefi 104827 Blerim Emruli 105571

CONTENT

ABSTRACT 2
INTRODUCTION 3
CHAPTER ONE (Overview) 5 First Generation System 5 Second Generation System 6 Third Generation System 7
CHAPTER TWO (GPRS Usage) 9 Ways To use GPRS 9
CHAPTER THREE (GPRS Network Protocols) 13
CHAPTER FOUR (Requirements, Functionality) 16 LIMITED RADIO RESOURCES 18 SPEEDS LOWER IN REALITY 18 NO SUPPORT OF MOBILE TERMINATED CALLS 18 SUBOPTIMAL MODULATION 18 TRANSIT DELAYS 18 NO STORE AND FORWARD 18 REQUIREMENTS USING GPRS 19 PACKET SWITCHING 20 SPECTRUM EFFICIENCY 20 INTERNET AWARE 20 SUPPORTS TDMA AND GSM 22 INDUSTRY PARTICIPATION 22
CHAPTER FIVE (SECURITY ISSUES) 25 EXPECTATIONS 25 Security & Vulnerabilities 26 Spam 29 Phishing 30 Viruses 30 Solving/Mitigating the Problem 31 Separation of Voice and Data 31 Rate Limitation 31 Significance 32
CHAPTER SIX (FEELING GPRS) 33 GPRS IN MACEDONIA 34
CONCLUSION 36
APPENDIXES 37
GLOSSARY 38

ABSTRACT

GPRS (general packet radio service) is a new nonvoice service that is being added to existing IS-136 TDMA (time division multiple access) networks.
How does it bring Internet to the mobile phone? This could be one good question if the reader of this project has no idea how GPRS works.
Well a short answer just for introduction is that it provides transmission of IP packets over cellular networks. So, Web browsing, chat and e-mail, all offered by Internet will be available from GSM and TDMA service providers via GPRS.
It is an upgrade of existing cellular network, without requiring the dedication of new channels, but actually it grabs a short time slots allocated from channels dedicated to voice traffic. In other words channels used for voice can be used for sending IP packets. So basically this is the idea used for bringing internet to your mobile phones.
It is a 2.5G technology. We will explain about the generations of mobile technology later but very shortly because that is not our topic.
INTRODUCTION

Figure 1.
Channel Division
And how they are used

So how actually it manages with the channels?
Channels are divided into slots, exactly in 8 slots. The maximum data transmission of each one of them is 13.4Kbps[1].
One of this slots is reserved for control. So it means that other seven can be used for GPRS traffic but in normal allocation 2 slots are reserved for voice traffic. Then we have 8-1-2=5 slots available. One of this slots is used for upload, because the user spends most of the time downloading rather than uploading data. It receives more than it transmits. So the remaining 5 slots are used in 4+1 proportion. 4 for download and 1 for upload.
If this is so, and according to the fact that each slot has a maximum of 13.4Kbps transmission then a GPRS maximum data rate expected from service operator is 4x13.4=53.6Kbps so this is pretty much compared with a 56K modem dial-up connection. So users that are used to dial-up speeds will be pleased using their cell phone as modem while traveling. Others that are used with high speed internet, GPRS won’t fulfill their expectations. They’d better try 3G or sooner wait for 4G tech.

|Type |Upload (Sending) |Download (Receiving) |
|GPRS |14 Kbps |28-54 Kbps |
|GSM CSD |9.6-14 Kbps |9.6-14 Kbps |
|HSCSD |28 Kbps |28 Kbps |
|Dial-UP |56 Kbps |56 Kbps |
|ISDN Standard |64 Kbps |64 Kbps |
|ADSL |256 Kbps |512 Kbps |
|Broadband |2 Mbps |2 Mbps |

Figure.
A comparison table[2]

Important notice
Download in GPRS it varies from 28-54Kbps because it depends from the number of channels it uses, 2, 3 or 4 of channels.

There is a debate from different brands for the data speed rate that GPRS could reach. Theoretically if all slots are used it could reach speed up to 171.2Kbps but network operators won’t allow the user to use all slots. How the slots are used we described them earlier in this project.
Nokia thinks that GPRS can reach up to 43Kbps while SonyEricsson thinks that even 56Kbps is achievable.

Also, the GPRS devices have a classification related to their ability to handle GSM voice calls and GPRS connections: [3]
|Class |Meaning |
|A |devices are capable of simultaneous voice and data transmission |
|B |devices support one type at a time, and switch automatically between data and voice |
|C |devices support one type at a time, and require user intervention to switch between data and voice |
CHAPTER ONE
OVERVIEW

HISTORY
We will go through the history of mobile generation’s briefly, just for a small comparison between them.

First Generation Systems

The global communication village has been evolving since the birth of the first generation analog cellular system.
Various standard systems were developed worldwide all of them different from each other: in the United States advanced mobile phones service (AMPS) was developed, Nordic mobile telephones (NMT) in Europe, total access communication systems (TACS) in the United Kingdom, Nippon Telephone and Telegraph (NTT) in Japan. All the first generation systems used frequency modulation (FM) for speech and frequency shift keying (FSK) for signaling, and the access technique used was frequency division multiple access (FDMA).[4]
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Second Generation Systems
Advancements in digital technology gave birth to Pan-European digital cellular mobile systems, with general mobile systems (GSM) taking the acronym from the French word.
We observe that time division multiple access (TDMA) is used as the access technique, except for IS-95, which is based in code division multiple access (CDMA). The second generation systems provide digital speech and short message services. GSM has become deeply rooted in Europe and in more than 70 countries worldwide. DCS-1800 is also spreading outside Europe to East Asia and some South American countries. The development of new digital cordless technologies gave birth to the second-supplement generation systems—namely, cell phones have been introduced to provide cost-effective wireless connection in local loops (WLL).[5]

The term local loop stands for the medium that connects the equipment in the user’s premises with telephone switching equipment. There are psychological and technical challenges that WLL faces in becoming acceptable to users. Because it replaces copper cable for connecting the user with the local exchange, the user may be apprehensive about reliability, privacy, and interference with wireless appliances like radio and television (manmade noise) and other WLL users. WLL must prove itself at least as good, if not better, than the services provided by physical cable. It should be able to carry and deliver voice, data, state-of-the-art multimedia services, and other modern services as efficiently as plain old telephone service (POTS) does.
Although the second generation services and their supplements have covered local, national, and international areas, they still have one major drawback in terms of a universal service facility. In addition to the system discussed in this section, wireless data systems and WLANs are also very important in the field of wireless communications. Cellular digital packet data (CDPD) is a new wide area packet data network. The general packet radio service (GPRS) standard was developed to provide packet data service over the GSM infrastructure.

Third Generation Systems
The third generation systems are being employed via universal wireless personal communications (UWPC) systems, which will provide universal speech services and local multimedia services. The third generation personal communication systems are in the process of implementation worldwide by the International Telecommunications Union (ITU) within the framework of the future public land mobile telecommunications systems (FPLMTS)/international mobile telecommunications-2000 (IMT-2000) activities and along the evolution path.
A lot of research and development activity is taking place worldwide in order to come to a common agreement on issues such as frequency bands, multiple access protocols, interfacing, internetworking, and integration (asynchronous transfer mode [ATM], fiber, air, fixed, macrocells, microcells, picocells, and hypercells), system development (baseband, terminals, and antennas), multimedia communications, satellite (frequency allocation, channel characterization, radio access), and technology (low power, size, and cost).

2G to 3G
The explosion of Internet usage has had a tremendous impact on the demand for advanced wireless communication services. However, the effectively rate of 2G mobile systems is too slow for many Internet services. As a result, in a race for higher speeds, GSM and other TDMA-based technologies from 2G developed so-called 2G+ mobile systems. In this group we classify the following systems: High Speed Circuit Switched Data (HSCSD) and GPRS. One may also classify in the 2G+ group Enhanced Data Rates for Digital Evolution (EDGE), but it is somewhere referred to as 3G technology.

HSCSD
HSCSD is a software upgrade to the GSM networks. No extra hardware is required. In the GSM network, single time slots are allocated to each user for voice or data (via modem) connection. Standard data transfer rate in GSM is 9,600 bps, although by reducing the redundancy in the channel coding it may go up to 14,400 bps. HSCSD gives a single user simultaneous access to multiple channels (time slots), up to four of eight in a single TDMA frame.
Assuming a standard transmission rate of 14.4 Kbps and using four time slots with HSCSD allows a theoretical data rate of 57.6 Kbps similar as GPRS but they have some distinctions. This enables Internet access at the same speed of many dial-up modem (56K) services across the fixed access network with 64-Kbps digital transmission lines. Although HSCSD is easy to be implemented in 2G networks, the drawback is the lack of statistical multiplexing (i.e., four time slots are occupied all the time during the connection). A potential problem in HSCSD is handover, which is complicated unless the same time slots are available end-to-end throughout the duration of the call.
While HSCSD is still circuit-switched technology, GPRS is complementary for communication with other packet-based networks such as the Internet.

GPRS TIMELINE
|Throughout |Network operators place trial and commercial contracts for GPRS infrastructure. |
|1999-2000 |Incorporation of GPRS infrastructure into GSM networks. |
|Summer of 2000 |First trial GPRS services become available. |
| |Typical single user throughput is likely to be 28 kbps. |
|Start of 2001 |Basic GPRS capable terminals begin to be available in commercial quantities. |
|Throughout 2001 |Network operators launch GPRS services commercially an roll out GPRS. |
| |Vertical market and executive GPRS early adopters begin using it regularly for nonvoice mobile |
| |communications. |
|2001/2002 |Typical single user throughput is likely to be 56 kbps. |
| |New GPRS specific applications, higher bitrates, greater network capacity solutions, more capable |
| |terminals become available, fueling GPRS usage. |
|2002 |Typical single user throughput is likely to be 112 kbps. |
| |GPRS Phase 2/EDGE begins to emerge in practice. |
|2002 |GPRS is routinely incorporated into GSM mobile phones and has reached critical mass in terms of usage. |
| |(This is the equivalent to the status of SMS in 1999) |
|2002/2003 |3GSM arrives commercially. |
CHAPTER TWO
GPRS USAGE

WAYS TO USE GPRS

There are two distinct ways that GPRS can be used for.
One of them is to use a GPRS device as a modem that will connect your lap-top to internet, thus allow searching web pages same as using a desktop modem connection. So this pretty much is a good purpose of using GPRS, because it enables you mobility and especially if you have ha mobile device that has a small screen or has an older version of WAP, like WAP 1.2 that won’t display pages as they exactly are.
The question is how does the process of connecting the lap-top with GPRS device?
One possibility is cell phone (used as GPRS modem) connecting with lap-top, and another one is using PCMCIA as GPRS modem.
A cell phone could be connected either via Bluetooth technology, Infrared with IrDA (Infrared Device Adapter) installed at the lap-top, or even connect the mobile phone with the lap-top via data cable.
We will draw an image to demonstrate this how it looks like.

Figure.
Ways to connect notebook with GPRS

Another way of using GPRS is to connect your mobile GPRS device directly to the internet using WAP (wireless application protocol) which requires far less bandwidth to load because it is restricted to text, while the newer version of WAP, that is WAP 2.0, has fewer restrictions.[6]

What is the problem?
Many data applications are very bursty in its traffic pattern: http, smtp, pop, telnet, ...
GPRS '' General Packet Radio Service
Does dynamic and flexible allocation of traffic channels.[7]
Allocation of more than one timeslot in a frame to allow for temporary high capacity.

Figure.
View of GPRS network

SGSN '' serving GPRS support node does mobility management, session control, authentication, encryption, charging

GGSN '' gateway GPRS support node the point of presence on the Internet, located in your home PLMN, functions as a router on the internet

CGSN '' combined GPRS support node the two nodes in one cabinet

Figure.
Connection to internet through SGSN and GGSN

So how can the process of connection be described. Or actually what kind of conditions do we have:[8]

Idle
Means that the mobile is not registered with the SGSN.
What an SGSN does?
Allocates a packet of temporary mobile subscriber identity P-TMSI to hide the identity of the subscriber.

Ready
'' informs SGSN of every cell change
'' it activates PDP context to establish a connection with the Internet

Standby
It reports for a change in Routing Area.
The current routing area is known by the SGSN
'' Though it still has a PDP context

Figure.
Processes for establishing a connection to the internet
IDLE-READY-STAND BY

CHAPTER THREE
GPRS NETWORK PROTOCOLS

Network Protocols Used
O.K so we do have a set of protocols and we’ll try to explain their usage:
There are several protocols used in the network equipment. These protocols operate in both the data and signaling planes. The following is a brief description of each protocol layer:[9]
Base Station System GPRS Protocol (BSSGP): BSSGP processes routing and quality of service (QoS) information for the BSS. BSSGP uses the Frame Relay Q.922 core protocol as its transport mechanism.
GPRS Mobility Management (GMM): protocol that operates in the signaling plane of GPRS and handles mobility issues such as roaming, authentication, and selection of encryption algorithms.
Network Service: protocol that manages the convergence sub-layer that operates between BSSGP and the Frame Relay Q.922 Core by mapping BSSGP’s service requests to the appropriate Frame Relay services.
BSSAP+: protocol that manages paging for voice and data connections and optimizes paging for mobile subscribers. BSSAP+ is also responsible for location and routing updates as well as mobile station alerting.

Figure.
GPRS Transport protocol stack

SNDCP which stands for sub-network dependent convergence protocol and mainly his function is for segmentation and reassembly.
Multiplexing of several PDP contexts into one LLC connection (segmentation and multiplexing of network-layer messages to a single virtual connection). Uses NSAPI to address PDP context.
Other than this it compresses data using V.42bis, then compresses TCP/IP headers.

Another important protocol is the LLC protocol (Logic Link Control)
Logical Link Control (LLC): is a data link layer protocol for GPRS which functions similar to Link Access Protocol - D (LAPD). This layer assures the reliable transfer of user data across a wireless network.
Links MS with SGSN. It retransmits any lost or error frame, if the acknowledge mode is used. Otherwise if the unacknowledged mode is used then than the erroneous frames are discarded.
It also provides an encryption '' GEA '' GPRS Encryption Algorithm.

Figure.
GPRS Transport protocol stack

GGSN addresses a specific PDP through GPRS Tunnel Protocol '' GTP.
GTP-U for user data and GTP-C for signaling, are the two versions of GTP, which is an IP over UDP tunnel.[10]
GPRS Tunnel Protocol (GTP): protocol that tunnels the protocol data units through the IP backbone by adding routing information. GTP operates on top of TCP/UDP over IP.

Session Management
Creating and handling of PDP context, it holds the IP address, information about QoS (Quality of Service), etc.

Figure.
GPRS signal protocol stack
CHAPTER FOUR
REQUIREMENTS, FUNCTIONALITY

HOW DOES GPRS WORK
So far we talked about the usage of GPRS, how it uses the channels to transmit data, connection etc…
In this part we will explain broadly how GPRS works.
With GPRS the information is divided into packets, sent independently across network and then gathered again at the recipient.
In Computer Networks course we were told that this process is know as Packed Switched, so this means that GPRS is Packed Switched.

The capacity of network is used more efficiently and sending information faster. (These comparisons are made with previous mobile generations, not comparing with newer ones)
With Circuit Switched a separate channel is reserved for every call and it is open during all conversation.[11]

GPRS is ideal for Wireless Application Protocol (WAP) services because of the cost saving WAP over GPRS bring to mobile operators and cellular consumers. Costs are reduced because GPRS radio resources are only needed while the message is being transferred. For the end user, that means you only pay for the time it takes to download the data and information that you need. For the GSM operator, that means that you will be able to provide high speed Internet access to consumers at a reasonable cost, because you will bill mobile phone users for only the amount of data that they transfer rather than billing them for the length of them that they are connected to the network.
The operator will charge you for packets received and not for the time using the GPRS service. The price is different from different operators and varies.
We will compare later in the project for the charges in Macedonia.

PDA’s and most mobile phones are GPRS compatible. It is easy to use laptop for mobile Internet access via GPRS with a special GPRS card.[12]

Figure.
GPRS core network architecture

LIMITED RADIO RESOURCES
There are only limited radio resources that can be deployed for different uses '' use for one purpose precludes simultaneous use for another. For example, voice and GPRS calls both use the same network resources.
SPEEDS LOWER IN REALITY
Attaining the highest GPRS data transmission speed of 171.2 kbps would require a single user taking over all eight timeslots; therefore, maximum GPRS speeds should be compared against constraints in the GPRS terminals and networks. It is highly unlikely that a GSM network operator would allow all timeslots to be used by a single GPRS user. The initial GPRS terminals are expected to only support one to three timeslots, which will be severely limiting to users. The reality is that mobile networks are always likely to have lower data transmission speeds than fixed networks. Mobile cellular subscribers often like to jump on the fact that a certain technology has high data transmission speeds, when the figure in all reality could be a theoretical number that is based on the perfect situation. Consumers should, therefore, compare all available mobile services and use the one that bests suits their needs.
NO SUPPORT OF MOBILE TERMINATED CALLS
There has been no confirmation by any mobile phone provider that initial GPRS terminals will support mobile terminated GPRS calls (receipt of GPRS calls on the mobile phone).When a mobile phone user initiates a GPRS session, they are agreeing to pay for the content to be delivered by the GPRS service. A worse case scenario would be that a mobile user would then be made responsible for paying for the unsolicited junk content that they received. This is one main reason why mobile vendors are not willing to support mobile terminated GPRS calls in their terminals.
SUBOPTIMAL MODULATION
GPRS is based on a modulation technique known as Gaussian minimum-shift keying (GMSK). EDGE is based on a new modulation scheme that allows a much higher bit rate across the air interface '' that is called eight-phase-shift keying (8 PSK) modulation. Since 8 PSK will also be used for 3GSM, network operators will need to incorporate it at some stage to make the transition to third generation mobile phone systems.
TRANSIT DELAYS
GPRS packets are sent in many different directions to reach the same destination. This makes room for the possibility for some of the packets to get lost or damaged during the transmission over the radio link. The GPRS standards are aware of this issue regarding wireless packet technologies and have worked to integrate data integrity and retransmission approaches to solving these problems. The result of this leads to possible transit delays.
NO STORE AND FORWARD
Currently, there is not a storage mechanism integrated into the GPRS standard.
REQUIREMENTS USING GPRS
• A mobile phone or terminal that supports GPRS (existing GSM phones do not support GPRS)
• A subscription to a mobile telephone network that supports GPRS '' use of GPRS must be enabled for that user. Automatic access to the GPRS may be allowed by some mobile network operators, others will require a specific opt-in
• Knowledge of how to send and/or receive GPRS information using their specific model of mobile phone, including software and hardware configuration (this creates a customer service requirement)
• A destination to send or receive information through GPRS.(Whereas with SMS this was often another mobile phone, in the case of GPRS, it is likely to be an Internet address, since GPRS is designed to make the Internet fully available to mobile users for the first time.

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PACKET SWITCHING
From a network operator perspective, GPRS involves overlaying packet based air interference on the existing circuit switched GSM network. This gives the user an option to use a packet-based data service. To supplement circuit switched network architecture with packet switching is quite a major upgrade. The GPRS standard is delivered in a very elegant manner '' with network operators needing only to add a couple of new infrastructure nodes and making a software upgrade to some existing network elements.
SPECTRUM EFFICIENCY
Packet switching means that GPRS radio resources are used only when users are actually sending or receiving data. Rather than dedicating a radio channel to a mobile data user for a fixed period of time, the available radio resource can be concurrently shared between several users. This efficient use of scarce radio resources means that large number of GPRS users can potentially share the same bandwidth and be served from a single cell.
The actual number of users supported depends on the application being used and how much data is being transferred. Because of the spectrum efficiency of GPRS, there is less need to build in idle capacity that is only used in peak hours. GPRS therefore lets network operators maximize the use of their network resources in a dynamic and flexible way, along with user access to resources and revenues.
GPRS should improve the peak time capacity of a GSM network since it simultaneously:
• Allocates scarce radio resources more efficiently by supporting virtual connectivity
• Migrates traffic that was previously sent using Circuit Switch Data to GPRS instead
• Reduces SMS Center and signaling channel loading by migrating some traffic that previously was sent using SMS to GPRS instead using the GPRS/SMS interconnect that is supported by the GPRS standards.
INTERNET AWARE
For the first time, GPRS fully enables Mobile Internet functionality by allowing interworking between the existing Internet and the new GPRS network.
Any service that is used over the fixed Internet today '' File Transfer Protocol (FTP), web browsing, chat, email, telnet '' will be as available over the mobile network because of GPRS. In fact, many network operators are considering the opportunity to use GPRS to help become wireless Internet Service Providers in their own right.
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The World Wide Web is becoming the primary communications interface '' people access the Internet for entertainment and information collection, the intranet for accessing company information and connecting with colleagues and the extranet for accessing customers and suppliers. Web browsing is a very important application for GPRS.
Because it uses the same protocols, the GPRS network can be viewed as a sub-network of the Internet with GPRS capable mobile phones being viewed as mobile hosts. This means that each GPRS terminal can potentially have its own IP address and will be addressable as such.
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SUPPORTS TDMA AND GSM
It should be noted that the General Packet Radio Service is not only a service designed to be deployed on mobile networks that are based on the GSM digital phone standard.

Figure.
TDMA frame structure

The IS-136 Time Division Multiple Access (TDMA) standard, popular in North and South America, will also support GPRS.This follows an agreement to follow the same evolution path towards third generation mobile phone networks concluded in early 1999 by the industry associations that support these two network types.

INDUSTRY PARTICIPATION
The first version of the GPRS standard is complete. The next version of the standard, which is expected to add advanced features, such as point-to-multipoint communications is in development. Cellular service providers currently cover almost 90 percent of the population in the United States.
GPRS Contracts Awarded
|Country |Carrier |GPRS Vendor |Core Infrastructure Vendor |Contract Value |Date |
|Austria |Mobilkom |Nortel (TRIAL) |Motorola/Nokia BSS an Nortel |NA |7/99 |
| | | |NSS | | |
|Austria |TELE.RING |Alcatel |Alcatel BSS + NSS + Microwave |NA |5/20/99 |
|Belgium |Belgacom |Motorola |Siemens switches, Motorola, |NA |3/15/99 |
| | | |Alcatel and Nokia base stations| | |
|Denmark |Sonofon |Nokia |Nokia | |6/2/99 |
|Finland |Radiolinja |Nokia |Nokia |NA |NA |
|Finland |Sonera |Nokia |Nokia |NA |2/23/99 |
|Finland |Sonera |Ericsson |Nokia |NA |6/99 |
|France |France Telecom |Alcatel (TRIAL) |Alcatel and Ericsson Mobile |NA |4/2/99 |
| | | |Switches, Alcatel, Nortel and | | |
| | | |Motorola Base Stations | | |
|France |France Telecom |Motorola (TRIAL)|As above |NA |3/99 |
|France |SFR/Cegetel |Alcatel |Alcatel and Ericsson mobile |NA |10/21/98 |
| | | |switches, Alcatel, Motorola, | | |
| | | |Nokia base stations | | |
|France |Bouygues Telecom |Nortel (TRIAL) |Nortel and Nokia BSS, Ericsson |NA |7/99 |
| | | |NSS | | |
|Germany |T-Mobil |Ericsson |Alcatel and Siemens switches. |NA |1/26/99 |
| | | |Alcatel, Motorola and Lucent | | |
| | | |base stations | | |
|Germany |T-Mobil |Alcatel |As above |NA |2/23/99 |
|Germany |Mannesmann D2 |Siemens |Siemens |NA |6/99 |
|Netherlands |Telfort |Ericsson |Ericsson |NA |2/23/99 |
|Poland |PTC/Era |Siemens |Siemens |NA |6/99 |
|Poland |Polkomtel |Nokia |Nokia |NA |NA |
|Scandinavia | |Siemens | | |2/9/99 |
|UK |BT Cellnet |Motorola |Motorola |$50 mil |3/18/99 |
|UK |One2One |Ericsson |Ericsson |$45 mil |5/12/99 |
|Australia |C&W Optus |Nortel |Nokia BSS, Nortel NSS |$33 mil |7/99 |
|Hong Kong |Sunday |Nortel |Nortel NSS, Nortel BSS |NA |5/99 |
|Hong Kong |Hongkong Telecom |Nokia | |HK$40-50m |7/6/99 |
|Hong Kong |Smartone |Ericsson |Ericsson |NA |NA |
|Singapore |Mobile One |Nokia | |NA |2/8/99 |
|Taiwan |KGTelecom |Nokia | |$100 mil | |
|USA |Omnipoint |Ericsson (TRIAL)|Ericsson |NA | |

The GPRS standard supports both X.25 and IP, the two top Internet protocols, but it is more likely that GPRS vendors and operators will put emphasis on the IP service. It is also likely that GPRS will first roll out in European countries. All new GSM phones will support GPRS.
This source is used from internet.

[pic]

When packet-switched data leaves the GPRS/GSM network, it is transferred to TCP-IP networks such as the Internet or X.25.Thus, GPRS includes new transmission and signaling procedures as well as new protocols for interworking with the IP world and other standard packet networks. The industry’s mobile phone vendors have working on new phones that will support both GSM and packet switching. Nowadays the industry has been working on PDA’s that have GPRS phone integrated in them.

CHAPTER FIVE
SECURITY ISSUES

EXPECTATIONS

Well basically you can do anything that you do when you are connected to internet, but the real question is what is most worth for it?
Web browsing, messengers (MSN, AOL, Yahoo, ICQ), VPN connections etc.

Figure.
Message Network

Message Flow

Security & Vulnerabilities
GPRS security functionality is equivalent to the existing GSM security. The SGSN performs authentication and cipher setting procedures based on the same algorithms, keys, and criteria as in existing GSM. GPRS uses a ciphering algorithm optimized for packet data transmission.
The majority of mobile phone subscribers are able to receive both voice and alphanumeric text via Short Messaging Service (SMS) transmissions. Text messaging allows users to interact with each other in situations where voice calls are not appropriate or possible.
Text messaging services are also extremely popular with the telecommunications industry. Cellular providers have opened their networks to a number of additional services designed to increase SMS messaging volume. Through service provider website interfaces, email, and a wide variety of applications including instant messaging, users across the Internet can contact mobile subscribers without the use of a cell phone. Such open functionality, however, has serious negative consequences for these networks.
Our research evaluates the security impact of Internet-originated text messages on cellular voice and SMS services. The connections between the Internet and phone networks introduce open functionality that detrimentally affects the fidelity of a cellular provider's service. Through the generation and use of large, highly accurate phone hit-lists, we demonstrate the ability to deny voice service to large metropolitan areas with little more than a cable modem. Moreover, attacks targeting the entire United States are feasible with resources available to medium-sized zombie networks. Even with small number of targets, we show that these cyberwarfare attacks are sustainable for tens of minutes. These attacks are especially threatening when compared to traditional signal jamming in that they can be invoked from anywhere in the world, often without physical involvement of the adversary.
There are many dangers of connecting digital and physical domains. For example, a wide array of systems with varying degrees of connectivity to the Internet were indirectly affected by the Slammer worm. The traffic generated by this worm was enough to render systems including Pro Credit Bank ATMs and emergency 93 services (I guess is the fire station).
There is nothing fundamentally different about the ways in which these victimized systems and cellular networks are connected to the Internet; all of the above systems were at one time both logically and physically isolated from external networks, but have now attached themselves to the largest open system on the planet. Accordingly, we show that mobile phone networks are equally as vulnerable to the influence of the Internet.
Identifying Vulnerabilities
In this project, we analyze GSM so as to quantify the necessary bandwidth to perform such attacks. This particular technology was selected because, with almost 2 billion GSM subscribers (some sources tell as that today there are 1.85billion, and expected to grow up to 3.3 by the year of 2010), these networks are by far the most widespread on the planet.
Cellular networks can be broken into two chief components - the radio, or "air interface" and the wired backbone. We are chiefly interested in how traffic injected from the Internet can be used to congest the air interface as it is the more constrained of the two.
We divide the air interface into two general components - Control Channels and Traffic Channels. It helps to think of control channels as a very small portion of radio frequency that allow cellular towers to send information pertaining to call setup, SMS delivery and network conditions (such as the availability of traffic channels) to mobile phones. Traffic channels are instead used to carry actual voice conversations after they have been established via the control channels. Figure 1, below, gives an intuitive representation of this setup.

Figure.
The air interface of a cellular network, divided into control and traffic channels. Control channels (CCHs) are used for call setup and SMS delivery. Traffic channels (TCHs) are used for the duration of voice calls.

Because text messages and mobile-phone call setups rely on the same limited resource, namely control channels, it is possible to attack this system. If enough text messages are sent so that no more control channels are available, calls will begin blocking (i.e. will not be connected).

[pic]

Figure. On the left, a request to set up a voice call is sent to the control channels. Because a number of unused control channels are available, the call will be connected. On the right, the control channels have been filled by SMS messages. If the attacker sends enough SMS messages to this particular tower, they can ensure that voice calls will always be blocked with a very high probability.

Before continuing, it is important to establish that such an attack is actually possible. If an attacker were to flood the control channels with enough SMS messages to reach capacity, they could create the same Denial of Service (DoS) to a given area.
In order to quantify the bandwidth necessary to launch such an attack, we put provide three possible scenarios for control channel allocation. The first, referred to as Urban, represents the typical number of control channels in a standard urban/metropolitan setting. Super-Urban represents an extremely densely populated city. 2x Super-Urban represents a theoretically possible, super over-provisioned network.
How difficult is such an attack to launch if its effects are observed naturally?
From the standards documentation, the table below shows just how much bandwidth would be required to deny voice service to cities the size of Washington D.C. and Manhattan. Notice that these values are attainable by high end cable-modem connections (Numerous providers offer cable modem/DSL connections with upload speeds up to 768Kbps.). A small collection of so-called "zombie" machines could also easily accomplish the same task.
|Required upload bandwidth to saturate an empty network |
|Area |# Sectors |# Control Channels |Capacity/Sector |Required Bandwidth* |Multi-Recipient Bandwidth*|
|Washington D.C. |120 |Urban |240 msgs/sec |2812.5 kbps |281.25 kbps |
| | |Super-Urban |360 msgs/sec |4218.8 kbps |421.88 kbps |
| | |2x Super-Urban |720 msgs/sec |8437.5 kbps |843.75 kbps |
|Manhattan |55 |Urban |110 msgs/sec |1289.1 kbps |128.91 kbps |
| | |Super-Urban |165 msgs/sec |1933.6 kbps |193.66 kbps |
| | |2x Super-Urban |330 msgs/sec |3867.2 kbps |386.72 kbps |
|* assuming 1500 bytes per message |

Are larger attacks possible? It would be theoretically possible to knock out cellular service for the continent with a data rate of approximately 370 Mbps. Such bandwidth could be harnessed from a moderately sized "zombie" network. Much larger Distributed Denial of Service (DDoS) attacks have already been seen, making this attack plausible.

So why have we not seen widescale attacks on the cellular network?
The answer is that simply sending SMS messages to every possible number is not effective. A successful adversary would have to collect data on the phones available in a given area. Suffice it to say that all of the necessary data can be collected through a variety of means via the Internet.
The fundamental issue at hand is that a connection exists between the Internet and cellular networks that allows adversaries to flood the phone network. In so doing, an attacker can use the Internet to attack cellular voice networks and prevent phone calls from connecting.
Even if SMS is run over its own dedicated channel so as not to interfere with voice traffic, an attacker can still prevent or delay legitimate SMS messages from being delivered by injecting enough messages to fill these channels to capacity.
Are there other potential threats?

It is possible for an attacker to fill a targeted phone with enough bogus SMS messages so that future, legitimate messages are either blocked, lost or significantly delayed. Additionally, like email, mobile phones are subject to threats including spam, viruses and phishing.
In many ways, SMS messages are similar to email. If used correctly, they both provide a powerful means of communication. Unfortunately, SMS inherits many of the same problems. Spam, phishing, and viruses have all been seen with email, and should therefore be expected with Internet originated SMS. Furthermore, due to SMS’s resource constrained model, these problems potentially worsen.

Spam
Spam has plagued the Internet for a number of years. Its realization is due to anonymity, automation, and the asymmetry between the cost of creating and processing a message. This allows a spammer to profit, even if only a small percentage of recipients actively respond. Unfortunately, spam has congested email, reducing its usefulness.
With email seemingly saturated, spammers are constantly looking for a new frontier. SMS is a logical progression; endowed with personal qualities, it resembles the early days of email.
Users often carry their mobile phone on their body, and the receipt of an SMS may even make one feel important. As spammers exploit this new medium, this characteristic will change, and users will begin to disregard SMS messages. This transition has already begun. In the past few years, both Europe and Asia have 10An SMS weather notification is useless if you are already stuck in the rain.

Phishing
Phishing is an often more dangerous abuse of email. Common forms include the investment emails and various forged update requests for bank and financial institution accounts.
Phishing need not be limited to account information. A user with a mobile phone implicitly has an account with a wireless service provider. Many users trust any message claiming to be from their provider. Any text message from the service provider should be avoided, including innocent service notifications. Once users become comfortable receiving information over a medium, they are more likely to give up sensitive information over that medium. Unfortunately, providers have begun to prompt for user information using this mechanism.
The space limitations of SMS play important role in phishing via text message. Figure 6 shows the ease in which a message can be spoofed. Furthermore, once multimedia messaging service (MMS) becomes more common, logos can be included to make messages even more believable.
Phishing for account information is not the only way adversaries can exploit uninformed users. Phones, in general, have been the subject of scams for many years. The ever growing popularity of SMS makes it a target for premium rate phone scams. An example of this is to advertise free content (ringtones, wallpaper, etc) via SMS, but use a high premium SMS number to distribute the content.

Viruses
As embedded systems such as mobile phones become general purpose computing platforms, they are subject to new vulnerabilities.
SMS has already seen its own “Ping of Death”, and viruses targeted at mobile platforms, including Cabir and Skulls (both transmitted via Bluetooth), have already been observed in the wild. This onslaught has prompted anti-virus companies such as F-Secure to expand their market to mobile phones.
F-Secure uses SMS and MMS to distribute virus definition updates. Unfortunately, this conduit can also be used for virus propagation. In fact, Mabir, a variant of Cabir, has already done this. By listening to incoming SMS and MMS messages, the Mabir worm’s propagation is not restricted by the physical limitations of Bluetooth. Users should expect the effects of viruses and worms to worsen as phones become more advanced.

Solving/Mitigating the Problem
Many of the mechanisms currently in place are not adequate to protect these networks. The proven practicality of address spoofing or distributed attacks via zombie networks makes the use of authentication based upon source IP addresses an ineffective solution. Limiting the maximum number of message received by an individual over a time period is also ineffective. Solutions must therefore take all of these matters into consideration. The mechanisms below offer both long term and temporary options for securing cellular networks.

Separation of Voice and Data
One thing as for solving the problem would be the separation of Voice and Data.
It would be difficult for the numerous connections between the Internet and cellular networks to be closed by service providers. In light of this, the most effective means of eliminating the above attacks is by separating all voice and data communications. In so doing, the insertion of data into cellular networks will no longer degrade the fidelity of voice services.
The separation of voice and data is not enough to completely ensure unaffected wireless communications. Internet-originated SMS messages can still be used to fill data channels such that legitimate text messaging and therefore all communication becomes impossible.
SMS traffic should therefore be subject to origin classification. Text messages originating outside of the network should be assigned low priority on data channels. Messages originating within the phone network should receive high priority.

Rate Limitation
Due to the time and money required to realize either of the above solutions, it is necessary to provide short term means of securing cellular networks. These techniques harness well-known rate limitation mechanisms.
On the air interface, the number of channels allowed to deliver text messages could be restricted. Given the addition of normal traffic filling control channels, this attack would still be effective in denying service to all but a few individuals. Additionally, this approach slows the rate with which legitimate text messages can be delivered, potentially elevating congestion in the core of the phone network. This approach is therefore not an adequate solution on its own.
All web interfaces should limit the number of recipients to which a single SMS submission is sent. The ability to send ten messages per submission at a number of service-provider websites is particularly dangerous as flooding the system requires one-tenth of the messages and bandwidth necessary to interfere with other networks.
Reducing the ability to automate submissions is another approach that should be considered as a temporary solution for these interfaces. Having the sender's computer calculate tractable but difficult puzzles before a submission is completed limits the frequency with which any machine can inject messages into a system. The use of CAPTCHAs, or images containing embedded text that is difficult for computers to parse, is also plausible. Because CAPTCHAs are not unbreakable and puzzles only impede the submission speed for individuals, both of these countermeasures can be circumvented if an attacker employs a large enough zombie network.
The last and certainly least popular suggestion is to close the interface between the web and cellular networks. While this solution is the most complete, it is extremely unlikely to receive serious consideration due to the potential financial consequences it would cause to both service providers and third-party companies providing goods and services through this interface. Given the size of these networks and the number of connected external entities, implementing this option may actually be impossible.

Significance
Cellular networks are a critical part of the economic and social infrastructures in which we live. These systems have traditionally experienced below 300 seconds of communication outages per year (i.e., ``five nines'' availability). However, the proliferation of external services on these networks introduces significant potential for misuse. We have shown that an adversary injecting text messages from the Internet can cause almost twice the yearly expected network down-time in a metropolitan area using hit-lists containing as few as 2500 targets. With additional resources, cyberwarfare attacks capable of denying voice and SMS service to an entire continent are also feasible. By attacking the less protected edge components of the network, we elicit the same effects as would be seen from a successful assault on the well protected network core.
Mobile voice and text messaging have become indispensable tools in the lives of billions of people across the globe.
One thing to mention in this project is the GPS system used for tracing the position of a user.

Tracking Systems has seamlessly converged wireless communications (GSM) and the Internet with global positioning (GPS/GPRS) technology enabling end-to-end mobile asset and vehicle location and monitoring solutions combining real-time GPS positioning and wireless communications systems delivering precise, time-critical mobile asset status and history information for increased security, greater loss control and telematics services.
CHAPTER SIX
FEELING GPRS

Even though this chapter might sound a bit controversial for the reader, but the idea of naming it in such way is because we tried to “feel” (means that we saw how GPRS works in Macedonia).
We tried the MMS features of GPRS but for mentioning is the fact that we used Internet through GPRS in our cell phones. As a demonstration that how that looked like in reality, we have made a short clip which demonstrates our connection through GPRS.
The clip comes together with the CD that is dedicated to the user.

GPRS IN MACEDONIA
(Cosmofon and MobiMak comparison)

As for beginning lets start with Cosmofon, not that it is our favourite but because indexing C is before M.

We searched from http://www.cosmofon.com.mk/ and the information that we got form there was:
Firstly there was a description of GPRS, what enables users to do. Then a demonstration how to connect with lap-top so the picture from that site was quite interesting.

Figure.
Connecting a notebook computer with cell phone, using it as GPRS modem through data cable.

Then the advantages of GPRS. Of course you do not expect the disadvantages to be mentioned while they are advertising it.
Charging is depending from the amount of data transmitted.
So depending from the models of post paid the price range was from 20-25 denars for 1MB, and some models such as Business packet and COSMOFON 90, and COSMOFON 180 get additional free traffic from 5 '' 10 MB per month.

Pre-paid customers on the other hand have different charging prices.
3MB for 90 denars.
5MB + 1MB free for 150denars.
15MB + 5MB free for 450denars.

The other operator Mobimak (which web site is http://www.mobimak.com.mk) informs it’s users that they upgraded their system from 9.6Kbps transfer with GPRS.

The prices though are different compared to COSMOFON.

The postpaid users will be charged 30 denars per MB with no VAT (Taxes) calculated.
Pre-Paid users though will be charget 50 denars per MB with no VAT calculated.

So customers you do the math of which one you should use.

One other thing that GPRS is used is for configuring MMS, so I (one of the authors) thought that I should try how MMS works on my i-mate K-JAM smartphone. Since I am a Mobimak customer I tried calling 6622.
But one bad thing about configuring MMS was that there was a limited number of cell phones that could be activated from the information service.
There were brands listed like NOKIA, SonyEricsson, Samsung, Alcatel, Siemens, Panasonic, Motorola, LG, and Ericsson (can’t believe those old phones were still alive), but nothing that matches with my cell phone.
Then I tried at Shop centers but yet could find help there, because the phone was not at their list. So I contacted with the Mobimak support and gave me the IP necessary to configure manually this service.

Server Name: mobimak MMS
Gateway: 62.162.155.227
Port number: 9201
Server address: http://mms.mobimak.com.mk

Despite this we got the T-Mobile MMS configuration
Server Name: T-Mobile MMS
Gateway: 216.155.165.50
Port number: 8080
Server address: http://216.155.174.84/servlets/mms

CONCLUSION

In my opinion, we (authors of this project) feel that GPRS is preety much reliable, but we must admit that we are not big fans of it. The reason is because we are used at high speed internet and though we think that overall users could be satisfied with GPRS. Hey after all your purpose is to use it in PDA’s or cell phones so what do you expect to download there other than read e-mails, chat on msn messenger.
So anyway is a good fit for the market, especially in Macedonia. We also think that the usage or the popularity of the GPRS will mostly depend from network operators. Charging will be the main indicator for their usage.
The cheaper it is, the most used will be.

APPENDIXES

This appendix lists some of the resources that are available for each information’s that we used in this project. As with any Internet resource, the URLs provided are subject to change.

Traffic Analysis and Design of Wireless IP Networks '' Toni Janevski

TDD-CDMA for Wireless Communications - Riaz Esmailzadeh, Masao Nakagawa

GSM and Network Services Johan Montelius

intel DeveloperUPDATEMagazine

GLOSSARY

AMPS
Advanced Mobile Phone System (AMPS) is the analog mobile phone system standard developed by Bell Labs, and officially introduced in the Americas in 1984. Though analog is no longer considered advanced at all, the relatively seamless cellular switching technology AMPS introduced was what made the original mobile radiotelephone practical, and was considered quite advanced at the time.

AOL:
AOL stands for America Online, a leading online service. America Online provides Internet access plus a number of member services, such as news, special-interest areas, and virtual chat rooms.

BTS:
Base Transceiver Station. Technical term for a mobile phone base station. A BTS contains the transmit and receive technology and also the aerials to supply a radio cell. Several BTSs are administered by a BSC (Base Station Controller), which is in turn under an MSC (Mobile Switching Center). Existing BSCs and BTSs can be extended for new radio technology to allow the network operator to reuse existing aerial sites for UMTS radio networks.

CDMA
Short for Code-Division Multiple Access, a digital cellular technology that uses spread-spectrum techniques. Unlike competing systems, such as GSM, that use TDMA, CDMA does not assign a specific frequency to each user. Instead, every channel uses the full available spectrum. Individual conversations are encoded with a pseudo-random digital sequence. CDMA consistently provides better capacity for voice and data communications than other commercial mobile technologies, allowing more subscribers to connect at any given time, and it is the common platform on which 3G technologies are built.

CGSN:
It contains the functionality of a Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN) in one physical node.
With the CGSN operators can introduce GPRS mobile data service at a low initial investment. When the GPRS subscriber base is expanding and the mobile data traffic is growing the CGSN nodes can easily be migrated to SGSN nodes.

Denial of Service (DoS)
Short for denial-of-service attack, a type of attack on a network that is designed to bring the network to its knees by flooding it with useless traffic. Many DoS attacks, such as the Ping of Death and Teardrop attacks, exploit limitations in the TCP/IP protocols. For all known DoS attacks, there are software fixes that system administrators can install to limit the damage caused by the attacks. But, like viruses, new DoS attacks are constantly being dreamed up by hackers.

EDGE:
Enhanced Data rates for GSM Evolution, or EDGE, is a digital mobile phone technology which acts as a bolt-on enhancement to 2G and 2.5G General Packet Radio Service (GPRS) networks. This technology works in GSM networks. EDGE (also known as EGPRS) is a superset to GPRS and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrades.

FDMA
FDMA (frequency division multiple access) is the division of the frequency band allocated for wireless cellular telephone communication into 30 channels, each of which can carry a voice conversation or, with digital service, carry digital data. FDMA is a basic technology in the analog Advanced Mobile Phone Service (AMPS), the most widely-installed cellular phone system installed in North America. With FDMA, each channel can be assigned to only one user at a time. FDMA is also used in the Total Access Communication System (TACS).

FM
Frequency Modulation (FM): Modulation in which the instantaneous frequency of a sine wave carrier is caused to depart from the center frequency by an amount proportional to the instantaneous value of the modulating signal. (188) Note 1: In FM, the carrier frequency is called the center frequency. Note 2: FM is a form of angle modulation. Note 3: In optical communications, even if the electrical baseband signal is used to frequency-modulate an electrical carrier (an "FM" optical communications system), it is still the intensity of the lightwave that is varied (modulated) by the electrical FM carrier. In this case, the "information,"as far as the lightwave is concerned, is the electrical FM carrier. The lightwave is varied in intensity at an instantaneous rate corresponding to the instantaneous frequency of the electrical FM carrier

FSK
Requency-shift keying (FSK): Frequency modulation in which the modulating signal shifts the output frequency between predetermined values. Note 1: Usually, the instantaneous frequency is shifted between two discrete values termed the " mark " and "space" frequencies. This is a noncoherent form of FSK. Note 2: Coherent forms of FSK exist in which there is no phase discontinuity in the output signal. Synonyms frequency-shift modulation, frequency-shift signaling.

GGSN:
Gateway GPRS Support Node (GGSN) - Interface between the GPRS wireless data network and other networks such as the Internet or private networks.

GPRS:
Short for General Packet Radio Service, a standard for wireless communications which runs at speeds up to 115 kilobits per second, compared with current GSM (Global System for Mobile Communications) systems' 9.6 kilobits.
GPRS, which supports a wide range of bandwidths, is an efficient use of limited bandwidth and is particularly suited for sending and receiving small bursts of data, such as e-mail and Web browsing, as well as large volumes of data.

GSM:
The Global System for Mobile Communications (GSM) is the most popular standard for mobile phones in the world. GSM service is used by over 1.8 billion people across more than 210 countries and territories. The ubiquity of the GSM standard makes international roaming very common between mobile phone operators, enabling subscribers to use their phones in many parts of the world. GSM differs significantly from its predecessors in that both signaling and speech channels are digital, which means that it is considered a second generation (2G) mobile phone system. This fact has also meant that data communication was built into the system from very early on. GSM is an open standard which is currently developed by the 3GPP.

HSCSD:
High-Speed Circuit-Switched Data (HSCSD), is an enhancement to Circuit Switched Data, the original data transmission mechanism of the GSM mobile phone system. As with CSD, channel allocation is done in circuit switched mode. The difference comes from the ability to use different coding methods and/or multiple time slots to increase data throughput.

ICQ:
ICQ ("I Seek You") is a program you can download that will let you know when friends and contacts are also online on the Internet .An online, real-time chat program developed by Mirabilis that allows users to send and receive messages back and forth on the Internet. It can be configured to alert or notify the user when acquaintances are online.

IrDA:
Short for Infrared Data Association, a group of device manufacturers that developed a standard for transmitting data via infrared light waves. Increasingly, computers and other devices (such as printers) come with IrDA ports. This enables you to transfer data from one device to another without any cables. For example, if both your laptop computer and printer have IrDA ports, you can simply put your computer in front of the printer and output a document, without needing to connect the two with a cable.

IS-95
(Interim Standard-95) The standards name for first-generation CDMA cellphone technology. Operating in the 800MHz band and the 1.9GHz PCS band, IS-95 was trademarked as "cdmaOne" by the CDMA Development Group (CDG) and is also known as "Narrowband CDMA" (N-CDMA). IS-95B adds data capability up to 64 Kbps that is integrated with voice. See CDMA and CDG.

LLC:
LLC (Logical Link Control) A data link protocol based or HDLC, developed for LANs by the IEEE 802 Committee and consequently common to all LAN standards for Data Link OSI Layer Two transmission.

Macrocells
A macrocell provides the largest area of coverage within a mobile network. The antennas for macrocells can be mounted on ground-based masts, rooftops or other existing structures. They must be positioned at a height that is not obstructed by terrain or buildings. Macrocells provide radio coverage over varying distances depending on the frequency used, the number of calls made and the physical terrain. Macrocell base stations have a typical power output in tens of watts.

Microcells
Microcells provide infill radio coverage and additional capacity where there are high numbers of users within macrocells. The antennas for microcells are mounted at street level, typically on the external walls of existing structures, lamp posts and other street furniture. The antennas are smaller than macrocell antennas and when mounted on existing structures, can often be disguised as building features. Typically, microcells provide radio coverage across smaller distances and are placed 300-1000 metres apart. They have lower outputs than macrocells, usually a few watts.

NMT
(Nordic Mobile Telephone) An analog cellular phone system deployed in more than 40 countries in Europe. Launched in the Scandinavian countries in 1979, NMT was the first analog cellphone system. Both 450MHz and 900MHz versions are available. See cellular generations.

NTT
NTT Network Innovation Laboratories in Yokosuka, Japan, is affiliated with the NTT Science and Core Technology Laboratory Group, one of NTT's three laboratory groups, and was established in 1999 to bring together a wide range of optics, wireless systems, network software and imaging researchers, and to cover all aspects of networking from the physical layer to the application layer.

PDP:
The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corp. in the 1970s and 1980s. The PDP-11 was a successor to DEC's PDP-8 computer in the PDP series of computers. It had several uniquely innovative features, and was easier to program than its predecessors. While well-liked by programmers, it was eventually superseded by personal computers, including the IBM PC and Apple II. The instruction set architecture of the PDP-11 influenced the design of the C programming language.

PCMCIA:
Short for Personal Computer Memory Card International Association, and pronounced as separate letters, PCMCIA is an organization consisting of some 500 companies that has developed a standard for small, credit card-sized devices, called PC Cards. Originally designed for adding memory to portable computers, the PCMCIA standard has been expanded several times and is now suitable for many types of devices. There are in fact three types of PCMCIA cards. All three have the same rectangular size (85.6 by 54 millimeters), but different widths

PLMN:
In telecommunication, a public land mobile network (PLMN) is a network that is established and operated by an administration or by a recognized operating agency (ROA) for the specific purpose of providing land mobile telecommunications services to the public.
Access to PLMN services is achieved by means of an air interface involving radio communications between mobile phones or other wireless enabled user equipment and land based radio transmitters or radio base stations
PLMNs interconnect with other PLMNs and PSTNs for telephone communications or with internet service providers for data and internet access.

POTS
POTS is a term sometimes used in discussion of new telephone technologies in which the question of whether and how existing voice transmission for ordinary phone communication can be accommodated. For example, Asymmetric Digital Subscriber Line and Integrated Services Digital Network connections provide some part of their channels for "plain old telephone service" while providing most of their bandwidth for digital data transmission.

SGSN:
The GPRS system is used by GSM Mobile phones, as of 2004 the most common mobile phone system in the world, for transmitting IP packets. The GPRS Core Network is the centralized part of the GPRS system and also provides support for UMTS based 3G networks. The GPRS core network is an integrated part of the GSM core network.

SMS
Short for Systems Management Server, a set of tools from Microsoft that assists in managing PCs connected to a local-area network (LAN). SMS enables a network administrator to create an inventory of all the hardware and software on the network and to store it in an SMS database. Using this database, SMS can then perform software distribution and installation over the LAN. SMS also enables a network administrator to perform diagnostic tests on PCs attached to the LAN.

SNDCP:
SNDCP stands for Sub Network Dependent Convergence Protocol. This is part of layer 3 of a GPRS protocol specifications. SNDCP interfaces to Internet Protocol at the top, and GPRS specific LLC (Logical Link Control) protocol at the bottom.
In the spirit of the GPRS specifications, there can be many implementations of SNDCP, supporting protocols such as X25. However, in reality, IP (Internet Protocol) is such an overwhelming standard that X25 has become irrelevant for modern applications, so all implementations of SNDCP for GPRS only support IP as the payload type.

TDMA:
Short for Time Division Multiple Access, a technology for delivering digital wireless service using time-division multiplexing (TDM). TDMA works by dividing a radio frequency into time slots and then allocating slots to multiple calls. In this way, a single frequency can support multiple, simultaneous data channels. TDMA is used by the GSM digital cellular system.

Telemetry
Telemetry is the wireless transmission and reception of measured quantities for the purpose of remotely monitoring environmental conditions or equipment parameters. The term is also used in reference to the signals containing such data.

QoS:
Short for Quality of Service, a networking term that specifies a guaranteed throughput level. One of the biggest advantages of ATM over competing technologies such as Frame Relay and Fast Ethernet, is that it supports QoS levels. This allows ATM providers to guarantee to their customers that end-to-end latency will not exceed a specified level.

TACS
(Total Access Communication System) An analog cellular phone system deployed mostly in Europe. It was modeled after the AMPS system in the U.S. In the U.K., ETACS (Extended TACS) transmits in the 871-904/916-949MHz band. International TACS (ITACS) and International ETACS (IETACS) are versions that operate outside the U.K. Narrowband TACS (NTACS) operates in the 860-870/915-925MHz band, and by using a narrower channel spacing, delivers more channels in the same amount of spectrum. See AMPS.

UDP:
User Datagram Protocol transports data as a connectionless protocol, using packet switching.

VPN:
A virtual private network (VPN) is a private data network that makes use of the public telecommunication infrastructure, maintaining privacy through the use of a tunneling protocol and security procedures. The idea of the VPN is to give the company the same capabilities at much lower cost by using the shared public infrastructure rather than a private one.

WAP:
Short for the Wireless Application Protocol, a secure specification that allows users to access information instantly via handheld wireless devices such as mobile phones, pagers, two-way radios, smart phones and communicators.

WLAN
Acronym for wireless local-area network. Also referred to as LAWN. A type of local-area network that uses high-frequency radio waves rather than wires to communicate between nodes.

WLL
Sometimes called radio in the loop (RITL) or fixed-radio access (FRA), WLL is a system that connects subscribers to the public switched telephone network (PSTN) using radio signals as a substitute for copper for all or part of the connection between the subscriber and the switch. This includes cordless access systems, proprietary fixed radio access, and fixed cellular systems.

Zombie Networks
A computer that has been implanted with a daemon that puts it under the control of a malicious hacker without the knowledge of the computer owner. Zombies are used by malicious hackers to launch DoS attacks. The hacker sends commands to the zombie through an open port.

-----------------------
[1] intel DeveloperUPDATEMagazine October 2002
[2] Online reference from http://www.gsmworld.com
[3] This reference can be found in nearly all my used literature
[4] TDD-CDMA for Wireless Communications - Riaz Esmailzadeh, Masao Nakagawa
[5] Interference Analysis and Reduction for Wireless system - Peter Stavroulakis
[6] Wikipedia (WAP 1.2 and 2.0)
[7] Traffic analysis and design of wireless IP networks - Toni Janevski
[8] intel DeveloperUPDATEMagazine
[9] GSM and Network Services Johan Montelius
[10] Traffic analysis and design of wireless IP networks - Toni Janevski
[11] Computer Network Andrew S. Tanenmbaum
[12] Wikipedia (GPRS core network architecture)

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    International Journal of Reconfigurable and Embedded Systems (IJRES) Vol. 1, No. 2, July 2012, pp. 49~54 ISSN: 2089-4864 49 Vehicle Accident Automatic Detection and Remote Alarm Device Varsha Goud*, V.Padmaja** *Department of ECE, VNR VJIET, Hyderabad, AP, INDIA ** Department of ECE, VNR VJIET, Hyderabad, AP, INDIA Article Info Article history: Received Mar 23, 2012 Revised Jul 2, 2012 Accepted Jul 12, 2012 Keyword: accident automatic detection micro electro mechanical system remote alarm…

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