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Project on GPRS Project on GPRS Document Transcript

  • 2 | P a g e ABOUT THE INSTITUTE Advanced Level Telecom Training Centre (ALTTC), Ghaziabad is the apex training institute of BSNL. An ISO 9001: 2008 accredited institute, ALTTC was set up as a joint venture of InternationalTelecommunication Union, Geneva, UNDP and the Governmentof India in 1975. ALTTCfunctions on the frontiers of telecom technology, finance and management and imparts training to the leaders in the business. Thestrength of ALTTC lies in the state of art labs, massiveinfrastructureand trained, talented and qualified human resourcepool. The Centre's Mission statement is "To Deliver Excellence Through Training". The training areas cover vastspectrumof topics such as Digital Switching and IN, Mobile Communication: GSM, 3G CDMA Data communication: Broadband and Networking, Optical Networks: SDH, DWDM, NGN, Access Networks, Management, Telecom Finance, Information Technology, Building Science (Civil and Electrical) and Telecom Network Planning.
  • 3 | P a g e PREFACE The difficulties the international industry standard bodies have had in approving all of the necessary standards has led to a delay in the deployment of 3G wireless systems. To lessen the impact of these delays, General Packet Radio Service is being introduced as an intermediate step to efficiently transport high-speed data over the current GSM wireless network infrastructures. GPRS is a packet-based data bearer service for GSM and TDMA networks. It is being rolled out by operators around the world as the first vital step towards 3G. GPRS gives mobile users faster data speeds and is particularly suitable for bursty Internet and intranet traffic. It makes mobile data faster, cheaper and more user-friendly than ever before. With GPRS-enabled mobile devices, users can be always on the Mobile Internet, so that, for example, emails arrive instantaneously. It also permits users to receive calls simultaneously when sending and receiving data calls. GPRS provides end-to-end IP connectivity that can be used to connect corporate LANs, ISPs and operators’ own service LANs via interfaces to TCP/IP and X.25. GPRS gives almost instantaneous connection set-up, and allows charging on the basis of data transmitted rather than connection time. As a packet data technology, GPRS only uses network resources and bandwidth when data is actually transmitted. This makes extremely efficient use of available radio bandwidth. Supported data rates range from 14.4 Kbps using just one TDMA slot, up to 115 Kbps and higher using all eight. GPRS can be implemented by simply adding new packet data nodes in GSM/TDMA networks, and upgrading existing nodes to provide a routing path for packet data between the mobile terminal and a gateway node. The gateway node provides interworking with external packet data networks for access to the Internet and intranets, for example, and requires few or no hardware upgrades to existing GSM/TDMA nodes. Between 2000 and 2002, upgrades to existing GSM, GPRS and TDMA networks are planned that will allow single-slot rates of 38.4 Kbit/s for HSCSD and 60 Kbit/s for GPRS – allowing rates as high as 384 Kbit/s by joining multiple time slots. Known as Enhanced Data for GSM Evolution (EDGE) these upgrades represent the final evolution of data communications within the GSM standard and will enable operators with existing 2G networks to evolve to 3G services on existing network frequencies, using current network infrastructure. Consequently, EDGE services are sometimes referred to as 2.5 Generation services. GPRS is ideal for Wireless Application Protocol (WAP) services. WAP over GPRS brings cost savings to both mobile operators and consumers, because GPRS radio resources are only needed while transferring the message. For the end user, that means you only pay for the time it takes to download. WAP content is optimised for thin-client devices, such as mobile phones and is also future proof, enabling it to be deployed on 2.5G, 3G and other networks. While GPRS features efficient use of resources, instant access, fast delivery of information and innovative charging models.
  • 4 | P a g e ACKNOWLEDGEMENT I would like to thank the teachers of Advanced Level Telecom Training Centre for providing me the golden opportunity to train in such a nice campus of Ghaziabad . I am vey grateful to Mr. Manoj Kumar Mishra and Mr. Mukesh Kumar Arya for their valuable support and guidance. I am very grateful and thankful to all those who helped me in my entire training program especially the teachers. I am indebted to my college training and placement department for providing me the opportunity of training in ALTTC.
  • 5 | P a g e INTRODUCTION The name, General Packet Radio Service (GPRS) doesn't convey much information to the non-technical user. Describing it as providing a direct link into the Internet from a GSM phone, is much clearer. GPRS is to mobile networks what ADSL (Asymmetric Digital Subscriber Line) is to fixed telephone networks - the favoured solution for providing fast and inexpensive Internet links. GPRS will undoubtedly speed up a handset's Internet connection - but it remains to be seen exactly how much speed can be wrung out of the system. GPRS works by amalgamating (aggregating) a number of separate data channels. This is feasible because data is being broken down into small 'packets' which are re-assembled by the receiving handset back into their original format. The catch is that the number of receiving channels does not necessarily have to match the number of sending channels. On the Internet, it is assumed that you want to view more information (such as a complicated Web page) than you want to send (such as a simple Yes or No response). So GPRS is an asymmetric technology because the number of ‘down’ channels used to receive data doesn’t match the number of ‘up’ channels used to send data. The task of defining GPRS has been the responsibility of the Special Mobile Group (SMG) - part of the 3GPP initiative (3rd Generation Partnership Project). Rather than wait for the final version of the SMG standard some manufacturers decided to go with GPRS handsets which conformed to an earlier version of the specifications known as SMG29. This basically offers two 'down' channels and a single 'up' channel. In practice each channel is offering around 12-13 Kbit/s so the top speeds works out to be around 26 Kbit/s. Most experts agree, however that full interoperability between products will come with SMG 31. This is capable of offering four 'down' channels which equates to a top speed of around 52 Kbit/s - the same as a high speed (V.90) landline modem. GPRS is classified as a 2.5G (or 2G Plus) technology because it builds upon existing network infrastructurewhereas with 3G networks it
  • 6 | P a g e normally requires building an entirely new network. In order to compete against 3G networks, therefore, North- American operators have been looking to GPRS to provide high speed data links. Hence, manufacturers have been working on a related technology known as EDGE (Enhanced Data for Global Evolution). In order to compete with 3G, EDGE must offer links running at 384 Kbit/s and originally this equated to running GPRS three times faster. However, because GPRS has proved much slower than expected, it now needs to be seven times faster. WHATIS GPRS? GPRS stands for General Packet Radio Service , and is a relatively low cost technology that offers packet-based radio service and allows data or information to be sent and received across mobile telephone networks.Designed to supplement the existing mobile technologies, like GSM, CDMA, TDMA etc. WHATDOES GPRS DO? GPRS provides a permanent connection where information can be sent or received immediately as the need arises, subject to radio coverage. No dial-up modem connection is necessary. This is why GPRS users are sometimes referred to be as being anytime-anywhere "always connected".The GPRS tariff structure is based on a fixed cost, dependent on the quantity of data required. In other words customers will be able to fix their operating costs without the concerns of variable billing. WHY GPRS? At present circuit switching technique like your telephone line, in order to send or receive emails, transfer files or browse WAP/Web is first necessary to make a 'data' call. The call is answered by a modem or an ISDN adapter owned either by the network operator itself (such as BT Cellnet) or by an Internet Service Provider (ISP). Next the caller is 'authenticated' by giving a user ID and password and then assigned an Internet address by the ISP or operator. The whole process can take up to sixty seconds or more and even at the end of this procedure the connection is slow - normally a mere 9.6 Kbit/s.
  • 7 | P a g e With packet switching technique GPRS, there is no call. Once the handset is powered on, by pressing a button the user is connected directly to the Internet. The link is only broken when the handset is turned off - hence GPRS is known as an 'always on' connection. The fact that the link is continuous has one major benefit. It enables the ISP/operator to know a handset's Internet address. So messages can be passed directly over the Internet from a PC, for example, down to your handset. Crucially this facility enables the Internet Service Provider to 'push'messages down to your handset - rather like an SMS message. The difference is that with GPRS the link is interactive. That means if you want to respond directly - such as instruct your broker to sell 500 shares - you can. One of the major criticisms aimed at WAP is that it lacked support for 'push' technologies. This failing has effectively been rectified via an update to the WAP standards (version 1.2) and the introduction of GPRS enabled WAP handsets. TIMESCALES FOR GPRS : When a new service is introduced, there are a number of stages before it becomes established. GPRS service developments will include standardization, infrastructure development, network trials, contracts placed, network roll out, availability of terminals, application development, and so on. These stages for GPRS are: Date Milestone Throughout1999 –2000 Network operators place trial and commercial contracts for GPRS infrastructure. Incorporation of GPRS infrastructureinto GSMnetworks Summer of 2000 Firsttrial GPRS services become available. Typical single user throughputis likely to be 28 kbps. For example, T-Mobil is planning a GPRS trial at Expo2000 in Hanover in the Summer of 2000
  • 8 | P a g e Start of 2001 Basic GPRS capable terminals begin to be available in commercial quantities Throughout2001 Network operators launch GPRS services commercially and roll out GPRS. Vertical market and executive GPRS early adopters begin using it regularly for nonvoice mobile communications 2001/2 Typical single user throughputis likely to be 56 kbps. New GPRS specific applications, higher bitrates, greater network capacity solutions, morecapable terminals become available, fuelling GPRS usage 2002 Typical single user throughputis likely to be 112 kbps. GPRS Phase 2/EDGE begins to emerge in practice 2002/3 3GSMarrives commercially Like the GSM standard itself, GPRS will be introduced in phases. Phase 1 is expected to be available commercially in the year 2000/1. Point to Point GPRS (sending information to a single GPRS user) will be supported, but not Point to Multipoint (sending the same information to several GPRS users at the same time). GPRS Phase 2 is not yet fully defined, but is expected to support higher data rates through the possibleincorporation of techniques such as EDGE (Enhanced Data rates for GSM Evolution), in addition to Point-to-Multipoint support. 2. FEATURES OF GPRS 2.1 KEY USER FEATURES OF GPRS : The General Packet Radio Service (GPRS) is a new nonvoice value added service that allows information to be sent and received across a mobile telephone network. It supplements today's Circuit Switched Data and Short Message Service. GPRS is NOT related to GPS (the Global
  • 9 | P a g e Positioning System), a similar acronym that is often used in mobile contexts. GPRS has several unique features which can be summarized as: SPEED: Theoretical maximum speeds of up to 171.2 kilobits per second (kbps) are achievable with GPRS using all eight timeslots at the same time. This is about three times as fast as the data transmission speeds possible over today's fixed telecommunications networks and ten times as fast as current Circuit Switched Data services on GSM networks. By allowing information to be transmitted more quickly, immediately and efficiently across the mobile network, GPRS may well be a relatively less costly mobile data service compared to SMS and Circuit Switched Data. IMMEDIACY: GPRS facilitates instant connections whereby information can be sent or received immediately as the need arises, subject to radio coverage. No dial-up modem connection is necessary. This is why GPRS users are sometimes referred to be as being "always connected". Immediacy is one of the advantages of GPRS (and SMS) when compared to Circuit Switched Data. High immediacy is a very important feature for time critical applications such as remote credit card authorization where it would be unacceptable to keep the customer waiting for even thirty extra seconds. NEW APPLICATIONS, BETTER APPLICATIONS: GPRS facilitates several new applications that have not previously been available over GSM networks due to the limitations in speed of Circuit Switched Data (9.6 kbps) and message length of the Short Message Service (160 characters). GPRS will fully enable the Internet applications you are used to on your desktop from web browsing to chat over the mobile network. Other new applications for GPRS, profiled later, include file transfer and home automation- the ability to remotely access and control in-house appliances and machines. SERVICE ACCESS : To use GPRS, users specifically need:
  • 10 | P a g e  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  Knowledgeof 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. From day one, GPRS users can access any web page or other Internet applications- providing an immediate critical mass of uses. 2.2 KEY NETWORKFEATURES OF GPRS : PACKET SWITCHING : GPRS involves overlaying a packet based air interface on the existing circuit switched GSM network. This gives the user an option to use a packet-based data service. To supplement a circuit switched network architecture with packet switching is quite a major upgrade. However, as we shall see later, 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. With GPRS, the information is split into separate but related "packets" before being transmitted and reassembled at the receiving end. Packet switching is similar to a jigsaw puzzle- the image that the puzzlerepresents is divided into pieces at the manufacturing factory and put into a plastic bag. During transportation of the now boxed jigsaw from the factory to the end user, the pieces get jumbled up. When the recipient empties the bag with all the pieces, they are reassembled to form the original image. All the pieces are all related and fit together, but the way they are transported and assembled varies. The Internet
  • 11 | P a g e itself is another example of a packet data network, the most famous of many such network types. 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 numbers 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 immigrates traffic that was previously sent using Circuit Switched Data to GPRS instead, and 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. INTERNETAWARE: 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. 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
  • 12 | P a g e and suppliers. These are all derivatives of the World Wide Web aimed at connecting different communities of interest. There is a trend away from storing information locally in specific software packages on PCs to remotely on the Internet. When you want to check your schedule or contacts, instead of using something like "Act!", you go onto the Internet site such as a portal. Hence, 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. SUPPORTS TDMA AND GSM : It should be noted right 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 mobile phone standard. 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. 3 GPRS TERMINALS :- A complete understanding of the application availability and GPRS timeline requires understanding of terminal types and availability. The term "terminal equipment" is generally used to refer to the variety of mobile phones and mobile stations that can be used in a GPRS environment; the equipment is defined by terminal classes and types. Cisco Gateway GPRS Serving Node (GGSN) and data network components interoperate with GPRS terminals that follow the GPRS standards. GPRS TERMINAL CLASSES : A GPRS terminal can be one of three classes: A, B, or C. A Class A terminal supports GPRS and other GSM services (such as SMS and voice) simultaneously. This support includes simultaneous attach, activation,
  • 13 | P a g e monitor, and traffic. As such, a Class A terminal can make or receive calls on two services simultaneously. In the presence of circuit-switched services, GPRS virtual circuits will be held or placed on busy rather than being cleared. A Class B terminal can monitor GSM and GPRS channels simultaneously, but can support only one of these services at a time. Therefore, a Class B terminal can support simultaneous attach, activation, and monitor, but not simultaneous traffic. As with Class A, the GPRS virtual circuits will not be closed down when circuit-switched traffic is present. Instead, they will be switched to busy or held mode. Thus, users can make or receive calls on either a packet or a switched call type sequentially, but not simultaneously. A Class C terminal supports only nonsimultaneous attach. The user must select which service to connect to. Therefore, a Class C terminal can make or receive calls from only the manually (or default) selected service. The service that is not selected is not reachable. Finally, the GPRS specifications state that support of SMS is optional for Class C terminals. DEVICE TYPES : In addition to the three variables, each handset will have a unique form factor. Some of the form factors will be similar to current mobile wireless devices, while others will evolve to use the enhanced data capabilities of GPRS. The earliest available type will be closely related to the current mobile phone. These will be available in the standard form factor with a numeric keypad and a relatively small display. PC Cards are credit card-sized hardware devices that connect via a serial cable to the bottom of a mobile phone. Data cards for GPRS phones will enable laptops and other devices with PC Card slots to be connected to mobile GPRS-capable phones. Card phones provide functionality similar to that offered by PC Cards, without needing a separate phone. These devices may need an earpiece and microphone to support voice services. Smart phones are mobile phones with built-in voice, nonvoice, and Web-browsing services. Smart phones integrate mobile computing
  • 14 | P a g e and mobile communications into a single terminal. They come in various form factors, which may include a keyboard or an icon drive screen. The Nokia 9000 series is a popular example of this form factor. The increase in machine-to-machine communications has led to the adoption of application-specific devices. These "black-box" devices lack a display, keypad, and voice accessories of a standard phone. Communication is accomplished through a serial cable. Applications such as meter reading utilize such black-box devices. Personal digital assistants (PDAs) such as the Palm Pilot series or Handspring Visor are data-centric devices that are adding mobile wireless access. These devices can either connect with a GPRS-capable mobile phone via a serial cable or have GPRS capability built in. 4 GPRS ARCHITECTURE : - From a high level, GPRS can be thought of as an overlay network onto a second-generation GSM network. This data overlay network provides packet data transport at rates from 9.6 to 171 kbps. Additionally, multiple users can share the same air-interface resources. GPRS attempts to reuse the existing GSM network elements as much as possible, but in order to effectively build a packet-based mobile cellular network, somenew network elements, interfaces, and protocols that handle packet traffic are required. Therefore, GPRS requires modifications to numerous network elements, as summarized in following Table and illustrated in following Figure. MODIFICATIONS REQUIRED FOR GPRS : GSM Network Element Modification or UpgradeRequired for GPRS
  • 15 | P a g e Subscriber Terminal (TE) A totally new subscriber terminal is required to access GPRS services. These new terminals will be backward compatible with GSMfor voice calls. BTS A softwareupgradeis required in the existing base transceiver site (BTS). BSC The base station controller (BSC) will also require a softwareupgrade, as well as the installation of a new piece of hardwarecalled a packet controlunit (PCU). The PCU directs the data traffic to the GPRS network and can be a separate hardwareelement associated with the BSC. Core Network The deployment of GPRS requires the installation of new corenetwork elements called the Serving GPRS SupportNode (SGSN) and Gateway GPRS SupportNode (GGSN). Databases (VLR, HLR, and so on) All the databases involved in the network will require softwareupgrades to handle the new call models and functions introduced by GPRS. GPRS REFERENCEARCHITECTURE: Generic GPRS Network Architecture
  • 16 | P a g e GPRS SUBSCRIBER TERMINALS : New terminals (TEs) are required because existing GSM phones do not handle the enhanced air interface, nor do they have the ability to packetize traffic directly. A variety of terminals will exist, as described in a previous section, including a high-speed version of current phones to support high-speed data access, a new kind of PDA device with an embedded GSM phone, and PC Cards for laptop computers. All these TEs will be backward compatiblewith GSM for making voice calls using GSM. GPRS BSS : Each BSC will require the installation of one or more PCUs and a softwareupgrade. The PCU provides a physical and logical data interface out of the base station system (BSS) for packet data traffic. The BTS may also require a software upgrade, but typically will not require hardware enhancements. When either voice or data traffic is originated at the subscriber terminal, it is transported over the air interface to the BTS, and 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 NETWORKS NODE: In the core network, the existing MSCs are based upon circuit- switched central-office technology, and they cannot handle packet traffic. Thus two new components, called GPRS Support Nodes, are added:  Serving GPRS Support Node (SGSN)  Gateway GPRS Support Node (GGSN) The SGSN can be viewed as a "packet-switched MSC;" it delivers packets to mobile stations (MSs) within its service area. SGSNs send queries to home location registers (HLRs) to obtain profile data of GPRS subscribers. SGSNsdetectnew GPRS MSs in a given servicearea, process registration of new mobile subscribers, and keep a record of their location inside a given area. Therefore, the SGSN performs mobility management functions such as mobile subscriber attach/detach and
  • 17 | P a g e location management. The SGSN is connected to the base-station subsystem via a Frame Relay connection to the PCU in the BSC. GGSNs are used as interfaces to external IP networks such as the public Internet, other mobile service providers' GPRS services, or enterprise intranets. GGSNs maintain routing information that is necessary to tunnel the protocol data units (PDUs) to the SGSNs that service particular MSs. Other functions include network and subscriber screening and address mapping. One (or more) GGSNs may be provided to support multiple SGSNs. More detailed technical descriptions of the SGSN and GGSN are provided in a later section. Enabling GPRS on a GSM network requires the addition of two core modules, the Gateway GPRS Service Node (GGSN) and the Serving GPRS Service Node (SGSN). As the word Gateway in its name suggests, the GGSN acts as a gateway between the GPRS network and Public Data Networks such as IP and X.25. GGSNs also connect to other GPRS networks to facilitate GPRS roaming. The Serving GPRS Support Node (SGSN) provides packet routing to and from the SGSN service area for all users in that service area. In addition to adding multiple GPRS nodes and a GPRS backbone, some other technical changes that need to be added to a GSM network to implement a GPRS service. These include the addition of Packet Control Units; often hosted in the Base Station Subsystems, mobility management to locate the GPRS Mobile Station, a new air interface for packet traffic, new security features such as ciphering and new GPRS specific signalling. GPRS MOBILITY MANAGEMENT: Mobility management within GPRS builds on the mechanisms used in GSM networks; as a MS moves from one area to another, mobility management functions areused to track its location within each mobile network. The SGSNs communicate with each other and update the user location. The MS profiles are preserved in the visitor location registers (VLRs) that are accessible by the SGSNs via the local GSM MSC. A logical link is established and maintained between the MS and the SGSN in each mobile network. At the end of transmission or when a MS moves out of the area of a specific SGSN, the logical link is released and the resources associated with it can be reallocated.
  • 18 | P a g e A final category of GPRS terminals is handheld communications. Again, these are primarily data-centric devices that are adding mobile wireless access. Access can be gained via a PC Card or via a serial cable to a GPRS-capable phone. 5 HOW GPRS WORKS : - The General Packet Radio Service is Mobile Data upgrade to a GSM mobile phone network. This provides users with packet data services (similar to the Internet) using the GSM digital radio network. Each voice circuit in GSM transmits the speech on a secure14kbps digital radio link between the mobile phone and a nearby GSM transceiver station. The GPRS service joins together multiple speech channels to provide higher bandwidth data connections for GPRS data users. The radio bandwidth remains the same, it is just shared between the voice users and the data users. The network operator has the choice of prioritizing one or the other. GPRS users will also benefit frombeing able to useGPRS while traveling as the GSMsystemshould transparently hand over the GPRS connection fromone base station to another. RADIO INTERFACE: Each GSM radio transceiver uses Time Division Multiplexing to deliver eight voice circuits on one radio channel. Each radio site may have one or more transceivers to provide sufficient channels to end users (maximum numbers are limited by many factors including - operators radio license, interference with other nearby GSM cells, cost of equipment, capacity of radio site infrastructure etc.) A GPRS user may theoretically use all voice channels on one transceiver - (8 * 14 kbps) but radios to support this are not available and the operators will probably reserve at least some channels for voice circuits. Each 14kbps channel may be shared by multiple 'connected' GPRS users (many users will be connected to the network but transmitting very little data). As a user's data requirements grow, they will use more of the available capacity within that timeslot, and then more available
  • 19 | P a g e timeslots up to the maximum available or the maximum supported by their device. In general the higher the data rate, the more power the mobile device will use and the shorter the battery life and the higher the transmitted RF power. If you areusing GPRS with a mobile phone, do not keep it near your ear for long periods while data transfers are taking place. GPRS MOBILEDEVICES : The key use for GPRS is to send and receive data to a computer application such as Email, web browsing or even telemetry (telemetry refers to devices not being controlled by humans such as cash point machines or traffic monitoring cameras etc.). To use GPRS the service is 'dialed' in a similar manner to a standard data call (though there is no phone no.) at which point the user is 'attached' and an IP address is allocated. From then on data can flow to and from the Internet until either the network unattaches you (maybe because of a time-out, fault or congestion) or you manually unattach. Mobile workers usually havea mobile phone, when this includes GPRS then it can also be used to transfer data to an connected computer. Some of the key issues are:  Using GPRS will not stop you making or receiving voice calls.  Currentphones will usually suspend the data session while a voice call takes place.  Battery life will be reduced when using GPRS.
  • 20 | P a g e  The data needs to be connected with your computer. The three standardmethods toconnect your computer to GPRS mobile phone are:  Infrared - available on most business mobile phones - just align the IR. port on the phone with the IR. port on the Laptop  Data-cable - reliable and doesn't require the careful alignment of IR. which may be difficult when traveling  Bluetooth - My preferred solution - often difficult to set up but once its configured Bluetooth provides a very convenient connection. Bluetooth is available for connecting to Laptops via USB, PC-cards or CF-cards in addition to cards for PDAs such as those offered by PALM. Older Compaq IPAQs will require an expansion jacket but newer Pocket PC devices usually include a suitable expansion port (check at the time of purchase). One very important point is that Bluetooth devices are very low powered so do not drain your computer battery or phone battery too much. Many people will be tempted by the all- in-one phone/PDA, but consider will you be happy with the relatively short battery life, large size and weight and unreliability of many PocketPC devices. GPRS data cards are also available, the issues here are:  Fully integrated solution  Best in Laptops with PC card expansion slots  GPRS will drain your battery so expect reduced life  You can subscribe to a different network than your GSM voice supplier  GPRS data cards will havetheir own SIM card and hence will need another subscription to your mobile network
  • 21 | P a g e GPRS ROAMING : In the short term don't expect to be able to roam to many countries with GPRS, many networks are still negotiating to set up roaming agreements. Technically there are two type of GPRS Roaming  Home Network Roaming - Here all data is transmitted from wherever you connect to a GPRS network to your home GPRS network where it is connected to the Internet or your company LAN as if you were indeed in your home country.  Local Network Roaming - Data is just connected to a local Internet connection point and will be subject to local conditions for security and performance. GPRS users would be advised to ensure they also are able to use either GSM or High Speed GSM data (HSCSD) to retrieve their data when traveling because of the changing state of GPRS roaming agreements. They can either phone their ISP or RAS server on their home network or subscribe to an ISP which provides local access points in each country visited. GPRS SECURITY : The radio interface is considered to be relatively secure being controlled by the GSM network's security - (SIM card + HLR). Security issues arise when data needs to leave the GPRS network to be delivered to either the Internet or a company LAN. Internetconnectivity is the cheapest and mostcommon - and here you can take charge of security by encrypting sensitive data. If your GPRS network supplier allows it you can set up encrypted VPN connections to your company systems - though there could be a performance hit. Treat the connection as a standard dial-up Internet connection to an ISP and take similar security precautions. NETWORKCONNECTIVITY : As a business GPRS user you will have a choice of methods to connect to the GPRS network - by far the most common method will be via the Internet. For larger users you may connect your company LAN to the GPRS networks using leased lines or Frame Relay virtual circuits.
  • 22 | P a g e INTERNET: Your company probable already has an Internet connection (though you may need more capacity if you add many GPRS users) and this provides a quick and easy way of connection to GPRS. The key problem is to deliver your data SECURELY to your users, using strong encryption such as with SSL (128 bit) or VPN (162 bit). For secure company Email access youhave a number of choices. These include:  VPN firewalls - this will provide secure access to everything on the company LAN from GPRS and other Internet users.  Microsoft Mobile Information Server  WAP interfaces to your Email system e.g. Peramon  POP server - set up a company POP server to provide Internet based Email, make sure to enable additional security if required. Employees (often senior managers) often bypass a companies security systems by redirecting to personal Internet Email accounts which provides them with a quick fix to mobile connectivity. LEASED LINES :
  • 23 | P a g e Leased lines provide the most secure method of connecting to GPRS but are traditionally expensive and have long contract periods. (Min 1 year) The protocol over the leased line would normally be frame relay but it is possible you could use ATM with some networks. You do not really need any CPE (Customer Premises Equipment) supplied by your GPRS network supplier, just a spare Frame relay port on an existing router. There may be economies to be made if you also use the leased line to carry standard voice and data and bulk SMS in addition to the GPRS traffic - in which case your network supplier will provide a device to route these onto your network. They may also try to sell you consultancy to design this interface - shop around to get the best solution. Keep costs down by connecting to a geographically close connection point to the chosen GPRS network. Not all networks have the same number and location of connection points (GGSNs in GPRS terms). FRAMERELAY : If you already have a frame relay connection with one of the key UK network suppliers then adding an addition PVC (Private Virtual Circuit) to one of the GPRS networks will make a cost effective solution, even if you have to increase the size of the link. Ask your network supplier about availability figures as it is important they have redundant connections to the chosen Frame supplier. 6 GPRS DATA COMMUNICATION:- Some cooperation still exists between elements of the current GSM services and GPRS. On the physical layer, resources can be reused and somecommon signaling issues exist. In the same radio carrier, there can be time slots (TSs) reserved simultaneously for circuit-switched and GPRS use. The most optimum resource utilization is obtained through dynamic sharing between circuit-switched and GPRS channels. During the establishment of a circuit-switched call, there is enough time to
  • 24 | P a g e preempt the GPRS resources for circuit-switched calls that have higher priority. GPRS SERVICE : The GPRS provides a bearer service from the edge of a data network to a GPRS MS. The GPRS protocol layering is illustrated in Figure shown below. The physical radio interface consists of a flexible number of TDMA time slots (from 1 to 8) and thus provides a theoretical raw data rate of 171 kbps. A Media Access Control (MAC) utilizes the resources of the physical radio interface and provides a service to the GPRS Logical Link Control (LLC) protocol between the MS and the serving GSN (SGSN). LLC is a modification of a High-Level Data Link Control (HDLC)-based Radio Link Protocol (RLP) with variable frame size. The two most important features offered by LLC are the support of point-to- multipoint addressing and the control of data frame retransmission. From the standpoint of the application, GPRS provides a standard interface for the network layer. Figure : GPRS Protocol Layering DATA ROUTING : One of the main issues in the GPRS network is the routing of data packets to/from a mobile user. The issue can be divided into two areas: data packet routing and mobility management. DATA PACKET ROUTING : The main functions of the GGSN involve interaction with the external data network. The GGSN updates the location directory using routing information supplied by the SGSNs about the location of a MS and routes the external data network protocol packet encapsulated over the GPRS backbone to the SGSN currently serving the MS. It also
  • 25 | P a g e decapsulates and forwards external data network packets to the appropriatedata network and collects charging data that is forwarded to a charging gateway. In following Figure, three different routing schemes are illustrated: mobile-originated message (path 1), network-initiated message when the MS is in its home network (path 2), and network- initiated message when the MS has roamed to another GPRS operator's network (path 3). In these examples, the operator's GPRS network consists of multiple GSNs (with a gateway and serving functionality) and an intra-operator backbone network. GPRS operators will allow roaming through an inter-operator backbone network. The GPRS operators connect to the inter-operator network via a boarder gateway (BG), which can provide the necessary interworking and routing protocols (for example, Border Gateway Protocol [BGP]). It is also foreseeable that GPRS operators will implement QoS mechanisms over the inter-operator network to ensure service-level agreements (SLAs). The main benefits of the architecture are its flexibility, scalablility, interoperability, and roaming. Figure : Routing of DataPackets betweenaFixedHost and a GPRS MS The GPRS network encapsulates all data network protocols into its own encapsulation protocol, called the GPRS Tunneling Protocol (GTP), as shown in above Figure. This is done to ensure security in the
  • 26 | P a g e backbone network and to simplify the routing mechanism and the delivery of data over the GPRS network. GPRS MOBILITY MANAGEMENT: The operation of the GPRS is partly independent of the GSM network. However, some procedures share the network elements with current GSM functions to increase efficiency and to make optimum use of free GSM resources (such as unallocated time slots). Figure : States of GPRS in a Mobile Station An MS has three states in the GPRS system: idle, standby, and active . The three-state model represents the nature of packet radio relative to the GSM two-state model (idle or active). Data is transmitted between a MS and the GPRS network only when the MS is in the active state. In the active state, the SGSN knows the cell location of the MS. However, in the standby state, the location of the MS is known only as to which routing area it is in. (The routing area can consist of one or more cells within a GSM location area.) When the SGSN sends a packet to a MS that is in the standby state, the MS must be paged. Because the SGSN knows the routing area in which the MS is located, a packet paging message is sent to that routing area. After receiving the packet paging message, the MS gives its cell location to the SGSN to establish the active state. Packet transmission to an active MS is initiated by packet paging to notify the MS of an incoming data packet. The data transmission proceeds immediately after packet paging through the channel indicated by the paging message. The purpose of the packet paging message is to simplify the process of receiving packets. The MS has to listen to only the packet paging messages, instead of all the data packets in the downlink channels, reducing battery use significantly.
  • 27 | P a g e When an MS has a packet to be transmitted, access to the uplink channel is needed. The uplink channel is shared by a number of MSs, and its use is allocated by a BSS. The MS requests use of the channel in a packet random access message. The transmission of the packet random access message follows Slotted Aloha procedures. The BSS allocates an unused channel to the MS and sends a packet access grant message in reply to the packet random access message. The description of the channel (one or multiple time slots) is included in the packet access grant message. The data is transmitted on the reserved channels. The main reasons for the standby state are to reduce the load in the GPRS network caused by cell-based routing update messages and to conserve the MS battery. When a MS is in the standby state, there is no need to inform the SGSN of every cell change—only of every routing area change. The operator can define the size of the routing area and, in this way, adjust the number of routing update messages. In the idle state, the MS does not have a logical GPRS context activated or any Packet-Switched Public Data Network (PSPDN) addresses allocated. In this state, the MS can receive only those multicast messages that can be received by any GPRS MS. Because the GPRS network infrastructure does not know the location of the MS, it is not possible to send messages to the MS from external data networks. A cell-based routing update procedure is invoked when an active MS enters a new cell. In this case, the MS sends a short message containing information about its move (the message contains the identity of the MS and its new location) through GPRS channels to its current SGSN. This procedure is used only when the MS is in the active state. When an MS in an active or a standby state moves from one routing area to another in the service area of one SGSN, it must again perform a routing update. The routing area information in the SGSN is updated and the success of the procedure is indicated in the response message. The inter-SGSN routing update is the most complicated of the three routing updates. In this case, the MS changes from one SGSN area to another, and it must establish a new connection to a new SGSN. This
  • 28 | P a g e means creating a new logical link context between the MS and the new SGSN, as well as informing the GGSN about the new location of the MS. 7 GPRS SOLUTION : - The GGSN network element, while the SGSN solution is available through Cisco partners. GGSN OVERVIEW : GGSN combines in one box:  GGSN features as defined by the European Telecommunication Standards Institute (ETSI)  Value-added networking functionality of Cisco routers The GGSN functionality embedded in the Cisco IOS® software is what differentiates the Cisco GGSN. The Cisco IOS software within a GGSN provides a sophisticated suite of networking capabilities that reside at the heart of internetworking devices. These capabilities provide interoperability with more standards-based physical and logical protocol interfaces than any other internetworking solutions. They connect otherwise-disparate hardware and provide security, reliability, and investment protection in the face of network growth, change, and new applications. The Cisco GGSN is compliant with ETSI's GPRS standards. Key GPRS features supported by GGSNinclude GPRS-defined routing and transfers, mobility management in conjunction with SGSN, GPRS quality-of-service (QoS) classes mapping to Internet QoS, QoS negotiation and handling, mobile authentication through Remote Authentication Dial-In User Service (RADIUS), dynamic IP addressing through Dynamic Host Configuration Protocol(DHCP), network management, and charging data collection. The Cisco GGSN supports all Cisco IOS features. A partial list of supported Cisco IOS features within GGSN includes IP routing, IP tunneling, and support of the Domain Name System (DNS), DHCP, and RADIUS. Additional technical information can be found in the Cisco GGSN data sheet.
  • 29 | P a g e GGSN APPLICATIONS : The GGSN can be deployed in a variety of network topologies and architectures. The following sections illustrate several alternatives. STANDALONEPLMN : Operators of a standalone Public Land Mobile Network (PLMN) who own the frequency may have one or more SGSNs and GGSNs. The GGSN serves as a gateway to the Internet (external packet data network). (See in following Figure.) Figure : The CiscoGPRS solutionenables GSM operators toprovide packet data service totheir mobile subscribers. WAP SERVICES IN GPRS ENVIRONMENT: The Wireless Access Protocol (WAP) empowers mobile users of wireless devices to easily access live interactive information services and applications from the screens of mobile phones. Services and applications include e-mail, customer care, call management, unified messaging, weather and traffic alerts, news, sports and information services, electronic commerce transactions and banking services, online address book and directory services, as well as corporate intranet applications. WAP utilizes HTTP 1.1 Web servers to provide content on the Internet or intranets, thereby taking advantage of existing application development methodologies and developer skill sets such as CGI, ASP,
  • 30 | P a g e NSAPI, JAVA, and Servlets. WAP defines an XML (eXtensible Markup Language) syntax called WML (Wireless Markup Language). All WML content is accessed over the Internet using standard HTTP 1.1 requests. To take advantage of today's extremely large market penetration of mobile devices, the user interface components of WML map well onto existing mobile phone user interfaces. This means end users can immediately use WAP-enabled mobile phones and services without re- education. WAP specifications enable products which employ standard Internet technology to optimize content and airlink protocols to better suit the characteristics and limitations of existing and future wireless networks and devices. Since WAP transport is based on IP, Cisco can provide all the required features and products to scale mass market WAP applications.(see in following figure) Figure : SN in a WAP enablednetwork FAXOVER GPRS : Faxes are ubiquitous—and inexpensive compared to postage. Not only are faxes fast and easy to use, they provide immediate and reliable confirmation that a remote fax machine received the message. In parts of the developing world, fax is a lifeline—the only reliable means of exchanging important business, government, and personal documents. The fax store-and-forward solution addresses each of these issues through a combination of Cisco and partner technology (see in following Figure):  Integration of fax with electronic documents converts faxes into Multipurpose Internet Mail Extension (MIME) messages with attached Tagged Image File Format (TIFF) documents that can be reconverted to fax or accessed electronically.
  • 31 | P a g e  Improved delivery controlis realized through directory services based on Simple Mail Transfer Protocol (SMTP) mail servers (provided by Netscape or plus directory services that map fax numbers to user accounts.  Messagestorage and retrieval includies software to convert PC documents into TIFF documents.  Least-cost routing, billing, management and user access via the Web is achieved through partner software that enables service providers to offer store-and-forward fax services profitably. CORPORATEVOICEAND DATA : Cisco GGSNenables offering alternative solutions whereGGSNcan be placed at the customer premises. Based on leading routing technology, Cisco IOS software, it is the ideal solution that integrates GPRS with already-deployed IP services, such as virtual private dial-up networks (VPDNs) and voice over IP (see in following Figure ). VIRTUAL PRIVATENETWORKCORPORATESOLUTIONS : High scalable SGSN nodes could be used to create a GPRS corporate solution. Scalability, interworking features, and standard protocols are the key aspects that Cisco is introducing in all its innovative and advanced projects. Distributed solutions with intelligent devices can give operators a competitive advantage, especially in the small office/home office (SOHO) business. (see in following Figure). 8 GPRS APPLICATIONS : - GPRS will enable a variety of new and unique services to the mobile wireless subscriber. These mobile applications contain several unique characteristics that enhance the value to the customers. First among them is mobility—the ability to maintain constant voice and data communications while on the move. Second is immediacy, which allows subscribers to obtain connectivity when needed, regardless of location and without a lengthy login session. Finally, localization allows subscribers to obtain information relevant to their current location. The combination of these characteristics provides a wide spectrum of possible applications that can be offered to mobile subscribers. The core
  • 32 | P a g e network components offered by Cisco enable seamless access to these applications, whether they reside in the service provider's network or the public Internet. In general, applications can be separated into two high-level categories: corporate and consumer. These include:  Communications—E-mail; fax; unified messaging; intranet/Internet access  Value-added services (VAS)—Information services; games  E-commerce—Retail; ticket purchasing; banking; financial trading  Location-based applications—Navigation; traffic conditions; airline/rail schedules; location finder  Vertical applications—Freight delivery; fleet management; sales-force automation  Advertising COMMUNICATIONS: Communications applications include all those in which it appears to the users that they are using the mobile communications network purely as a pipe to access messages or information. This differs from those applications in which users believe that they are accessing a service provided or forwarded by the network operator. INTRANETACCESS : The first stage of enabling users to maintain contact with their office is through access to e-mail, fax, and voice mail using unified messaging systems. Increasingly, files and data on corporate networks are becoming accessible through corporate intranets that can be protected through firewalls, by enabling secure tunnels (virtual private networks [VPNs]). INTERNETACCESS : As a critical mass of users is approached, more and more applications aimed at general consumers are being placed on the Internet. The Internet is becoming an invaluable tool for accessing corporate data as well as for the provision of product and service information. More recently, companies have begun using the
  • 33 | P a g e Internet as an environment for carrying out business, through e- commerce. E-MAIL AND FAX: E-mail on mobile networks may take one of two forms. It is possible for e-mail to be sent to a mobile user directly, or users can have an e-mail account maintained by their network operator or their Internet service provider (ISP). In the latter case, a notification will be forwarded to their mobile terminal; the notification will include the first few lines of the e-mail as well as details of the sender, the date/time, and the subject. Fax attachments can also accompany e-mails. UNIFIED MESSAGING : Unified messaging uses a single mailbox for all messages, including voice mail, faxes, e-mail, short message service (SMS), and pager messages. With the various mailboxes in one place, unified messaging systems then allow for a variety of access methods to recover messages of different types. Some will use text-to-voice systems to read e-mail and, less commonly, faxes over a normal phone line, while most will allow the interrogation of the contents of the various mailboxes through data access, such as the Internet. Others may be configured to alert the user on the terminal type of their choice when messages are received. VALUE-ADDED SERVICES : Value-added services refer strictly to content provided by network operators to increase the value of their service to their subscribers. Two terms that are frequently used with respect to the delivery of data applications are push and pull, as defined below.  Push refers to the transmission of data at a predetermined time, or under predetermined conditions. It could also apply to the unsolicited supply of advertising (for example, delivery of news as it occurs, or stock values when they fall below a preset value).  Pull refers to the demanding of data in real time by the user (for example, requesting stock quotes or daily news headlines). To be valuable to subscribers, this content must posses several characteristics:
  • 34 | P a g e  Personalized information is tailored to user-specific needs with relevant information. A stock ticker, focusing on key quotes and news, or an e-commerce application that knows a user's profile are two examples of personalized information.  Localized content is based on a user's current location; it can include maps, hotel finders, or restaurant reviews.  Convenience suggests that the user interface and menu screens are intuitive and easy to navigate.  Trust pertains primarily to e-commerce sites where the exchange of financial or other personal information is required. E-COMMERCE: E-commerce is defined as the carrying out of business on the Internet or data service. This would include only those applications where a contract is established over the data connection, such as for the purchase of goods, or services, as well as online banking applications because of the similar requirements of user authentication and secure transmission of sensitive data. BANKING: The popularity among banks of encouraging electronic banking comes from the comparable costs of making transactions in person in a bank to making them electronically. Specific banking functions that can be accomplished over a wireless connection include: balance checking, moving money between accounts, bill payment, and overdraft alert. FINANCIAL TRADING : The immediacy with which transactions can be made using the Internet and the requirement for up-to-the-minute information has made the purchasing of stocks a popular application. By providing push services such as those detailed in the VAS section earlier and coupling these with the ability to make secure transactions from the mobile terminal, a very valuable service unique to the mobile environment can be provided. LOCATION-BASED SERVICES AND TELEMATICS : Location-based services provide the ability to link push or pull information services with a user's location. Examples include hotel and
  • 35 | P a g e restaurant finders, roadside assistance, and city-specific news and information. This technology also has vertical applications such as workforce management and vehicle tracking. VERTICAL APPLICATIONS : In the mobile environment, vertical applications apply to systems utilizing mobile architectures to supportthe carrying outof specific tasks within the value chain of a company, as opposed to applications that are then being offered for sale to a consumer. Examples of vertical applications include:  Sales support—Provision of stock and product information for sales staff, as well as integration of their use of appointment details and the remote placing of orders  Dispatching—Communication of job details such as location and scheduling; permitting interrogation of information to support the job  Fleet management—Control of a fleet of delivery or service staff, monitoring their locations and scheduling work  Parcel delivery—Tracking the locations of packages for feedback to customers and performance monitoring ADVERTISING: Advertising services will be offered as a push type information service. Advertising may be offered to customers to subsidize the cost of voice or other information services. Finally, advertising may be location sensitive where, for example, a user entering a mall would receive advertising specific to the stores in that mall. 9 LIMITATIONS OF GPRS : - It should already be clear that GPRS is an important new enabling mobile data service which offers a major improvement in spectrum efficiency, capability and functionality compared with today's nonvoice
  • 36 | P a g e mobile services. However, it is important to note that there are some limitations with GPRS, which can be summarized as: LIMITED CELL CAPACITY FOR ALL USERS : GPRS does impact a network's existing cell capacity. 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. The extent of the impact depends upon the number of timeslots, if any, that are reserved for exclusive use of GPRS. However, GPRS does dynamically manage channel allocation and allow a reduction in peak time signalling channel loading by sending short messages over GPRS channels instead. RESULT: NEED FOR SMS as a complementary bearer that uses a different type of radio resource. SPEEDS MUCH LOWER IN REALITY : Achieving the theoretical maximum GPRS data transmission speed of 172.2 kbps would require a single user taking over all eight timeslots without any error protection. Clearly, it is unlikely that a network operator will allow all timeslots to be used by a single GPRS user. Additionally, the initial GPRS terminals are expected be severely limited- supporting only one, two or three timeslots. The bandwidth available to a GPRS user will therefore be severely limited. As such, the theoretical maximum GPRS speeds should be checked against the reality of constraints in the networks and terminals. The reality is that mobile networks are always likely to have lower data transmission speeds than fixed networks. RESULT: Relatively high mobile data speeds may not be available to individual mobile users until Enhanced Data rates for GSM Evolution (EDGE) or Universal Mobile Telephone System (3GSM) are introduced. SUPPORT OF GPRS MOBILETERMINATEBY TERMINALS IS NOT ENSURED: At the time of writing, there has been no confirmation from any handset vendors that mobile terminated GPRS calls (i.e. receipt of GPRS
  • 37 | P a g e calls on the mobile phone) will be supported by the initial GPRS terminals. Availability or not of GPRS MT is a central question with critical impact on the GPRS business case such as application migration from other nonvoice bearers. By originating the GPRS session, users confirm their agreement to pay for the delivery of content from that service. This origination may well be performed using a Wireless Application Protocol (WAP) session using the WAP microbrowser that will be built into GHPRS terminals. However, mobile terminated IP traffic might allow unsolicited information to reach the terminal. Internet sources originating such unsolicited content may not be chargeable. A possible worse case scenario would be that mobile users would have to pay for receiving unsolicited junk content. This is a potential reason for a mobile vendor NOT to support GPRS Mobile Terminate in their GPRS terminals. However, there is always the possibility of unsolicited or unwanted information being communicated through any media, but that does not mean that we would wish to preclude the possibility of any kind of communication through that means altogether. A network side solution such as GGSN or charging platform policing would be preferable rather than a non-flexible limitation built into all the GPRS handsets. When we asked Nokia about this issue, it commented: "Details of the Nokia GPRS terminals are not available at this time. It is too early to confirm whether MT will be supported in the first Nokia GPRS terminals". The company's policy is not to make details available about products before they are announced. Readers should contact the GSM Association, Mobile Lifestreams Limited and/ or the vendors directly to encourage them to incorporate support for GPRS MT in their initial terminals. RESULT: GPRS usability and therefore business caseis threatened if GPRS MT is not supported by GPRS 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- this is called eight-phase-shift keying (8 PSK) modulation. Since 8 PSK will also
  • 38 | P a g e be used for 3GSM, network operators will need to incorporate it at some stage to make the transition to third generation mobile phone systems. RESULT: NEED FOR EDGE. TRANSITDELAYS : GPRS packets are sent in all different directions to reach the same destination. This opens up the potential for one or some of those packets to be lost or corrupted during the data transmission over the radio link. The GPRS standards recognize this inherent feature of wireless packet technologies and incorporate data integrity and retransmission strategies. However, the result is that potential transit delays can occur. Because of this, applications requiring broadcastquality video may well be implemented using High Speed Circuit Switched Data (HSCSD). HSCSD is simply a Circuit Switched Data call in which a single user can take over up to four separate channels at the same time. Because of its characteristic of end to end connection between sender and recipient, transmission delays are less likely. RESULT: NEED FOR HSCSD. NO STORE AND FORWARD : Whereas the Store and Forward Engine in the Short Message Service is the heart of the SMS Center and key feature of the SMS service, there is no storage mechanism incorporated into the GPRS standard, apart from the incorporation of interconnection links between SMS and GPRS. RESULT: NEED FOR SMS.
  • 39 | P a g e 10 RELATED GPRS CHALLENGES :- BILLING: GPRS is a different kind of service from those typically available on today’s mobile networks. GPRS is essentially a packet switching overlay on a circuit switching network. The GPRS specifications stipulate the minimum charging information that must be collected in the Stage 1 service description. These include destination and source addresses, usage of radio interface, usage of external Packet Data Networks, usage of the packet data protocol addresses, usage of general GPRS resources and location of the Mobile Station. Since GPRS networks break the information to be communicated down into packets, at a minimum, a GPRS network needs to be able to count packets to charging customers for the volume of packets they send and receive. Today's billing systems have difficulties handling charging for today's nonvoice services. It is unlikely that circuit switched billing systems will be able to process a large number of new variables created by GPRS. GPRS call records are generated in the GPRS Service Nodes. The GGSN and SGSN may not be able to store charging information but this charging information needs to be processed. The incumbent billing systems are often not able to handle real time Call Detail Record flows. As such, an intermediary charging platform is a good idea to and preparing it for submission to perform billing mediation by collecting the charging information from the GPRS nodes the billing system. Packet counts are passed to a Charging Gateway that generates Call Detail Records that are sent to the billing system. However, the crucial challenge of being able to bill for GPRS and therefore earn a return on investment in GPRS is simplified by the fact that the major GPRS infrastructure vendors all support charging functions as part of their GPRS solutions. Additionally, a wide range of other existing non-GSM packet data networks such as X.25 and Cellular Digital Packet Data (CDPD) are in place along with associated billing systems. It may well be the case that the cost of measuring packets is greater than their value. The implication is that there will NOT be a per packet charge since there may be too many packets to warrant counting and charging for. For example, a single traffic monitoring application can
  • 40 | P a g e generate tens of thousands of packets per day. Thus the charging gateway function is more a policing function than a charging function since network operators are likely to tariff certain amounts of GPRS traffic at a flat rate and then need to monitor whether these allocations are far exceeded. This is not to say that we will end up with the free Internet Service Provider model that has become established on the fixed Internet in which users pay no fixed monthly charge and network operators rely on advertising sales on mobile portal sites to make money. There is a premium for mobility and there is frankly a shortage of mobile bandwidth that limits the extent to which that bandwidth is viewed as a commodity. And given the additional customer care and billing complexity associated with mobile Internet and nonvoice services, network operators would be ill advised to reduce their prices in such a way as to devalue the perceived value of mobility. TARIFFING: Decisions on charging for GPRS by packet or simply a flat monthly fee are contentious but need to be made. Charging different packets at different rates can make things complicated for the user, whilst flat rates favor heavy users more than occasional ones. We believe that the optimal GPRS pricing model will be based on two variables- time and packet. Network operators should levy a nominal per packet charge during peak times plus a flat rate, no per packet charge during non peak times. Time and packet related charging will encourage applications such as remote monitoring, meter reading and chat to use GPRS overnight when spare network capacity is available. Simultaneously, a nominal per packet charge during the day will help to allocate scarce radio resources and charge radio heavy applications such as file and image transfer more than applications with lower data intensity. It has the advantage that it will automatically adjust customer charging according to their application usage. As such the optimal charging model could well be a flat rate charge during off-peak times along with a per packet charge during peak times. CUSTOMER SERVICE :
  • 41 | P a g e Value-added network services such as mobile data, mobile Internet and unified messaging all generate certain specific customer problems and requirements, thereby requiring customer service personnel to be aware of these issues and know how to solve them. Nonvoice services are surprisingly complex- involving unique configurations of phone types, data cards, handheld computers, subscriptions, operating systems, Internet service providers and so on. Some network operators require customers to opt into certain value added services rather than including them as part of the core subscription- necessitating a customer serviceprocess. Itis even possible to write a 350 page book about the SHORT message service (it is called "YES2SMS")! In theory, the need for dedicated customer service for Circuit Switched Data, SMS and other nonvoice mobile services will decrease in the future as terminals and services become easier to use and as the services themselves are used more widely for customer service purposes. The reality in the short and medium term is that the need for customer support for value-added services will increase not decrease as awareness of services and their usage increases, and as new services and terminals come onto the marketplace. Rather than keeping everything in-house or outsourcing everything, we are a proponent of an approach that keeps first line support and customer contact in-house, whilst outsourcing the difficult specific customer service problems arising from connectivity issues and so on. In this way, the network operator is aware of and in control of the kinds of questions and problems its customers are asking. It is well worth incurring the cost to get the customer aware, educated and initially set up with data services, because, for example, once the PC data card has been successfully connected to the laptop to the Internet software and so on, the same configuration can be repeatedly used. The one-off customer requirement leads to ongoing usage. 11 GLOSSARY OF TERMS : -
  • 42 | P a g e 2G Second generation; generic name for second generation of digital mobile networks (such as GSM, and so on) 3G Third generation; generic name for next-generation mobile networks (UniversalTelecommunications System [UMTS], IMT-2000; sometimes GPRS is called 3G in North America) 3GPP 3G Partnership Project BG Border gateway BGP Border Gateway Protocol bps Bits per second BSC Base Station Controller BTS Base transceiver station CS Circuit switched DHCP Dynamic HostConfiguration Protocol DNS Domain Name System EDGE Enhanced data rates for GSMevolution; upgrade to GPRS systems that requires new basestations and claims to increasebandwidth to 384 kbps ETSI European Telecommunications Standards Institute Gb Interfacebetween a SGSNand a BSS Interfacebetween a GGSN and a HLR Gc Interfacebetween a GGSN and a HLR Gd Interfacebetween a SMS-GMSCand a SGSN, and between a SMS- IWMSCand a SGSN
  • 43 | P a g e Gf Interfacebetween a SGSNand an EIR GGSN Gateway GPRS SupportNode Gi Reference point between GPRS and an external packet data network GIWU GSM interworking unit GMSC Gateway mobile services switching center Gn Interfacebetween two GSNs within the same PLMN Gp Interfacebetween two GSNs in different PLMNs GPRS General Packet Radio Service; upgradeto existing 2G digital mobile networks to provide higher-speed data services Gr Interfacebetween a SGSNand a HLR Gs Interfacebetween a SGSNand a MSC/VLR GSM Global Systemfor Mobile Communications; most widely deployed 2G digital cellular mobile network standard GSN GPRS SupportNode (xGSN) GTP GPRS Tunneling Protocol GW Gateway HDLC High-Level Data Link Control HLR Home location register HSCSD High-speed circuit-switched data; softwareupgradefor cellular networks that gives each subscriber 56K data IP InternetProtocol
  • 44 | P a g e ISP Internetserviceprovider L2TP Layer two Tunneling Protocol LLC Logical Link Control MAC Medium Access Control MM Mobility management MS Mobile station MSC Mobile services switching center NAS Network access server OA&M Operations, administration, and management OSS Operations SupportSystem PCU Packet controlunit PDA Personaldigital assistant PDN Packet data network PDP Packet Data Protocol PLMN Public Land Mobile Network; generic name for all mobile wireless networks that useearth base stations rather than satellites; the mobile equivalent of the PSTN PSPDN Packet Switched Public Data Network PSTN Public Switched Telephone Network PVC Permanent virtualcircuit
  • 45 | P a g e QoS Quality of service RADIUS Remote Authentication Dial-In User Service RLP Radio Link Protocol SGSN Serving GPRS SupportNode SLA Service-level agreement SMS Shortmessageservice SMSC Shortmessageservice center SS7 Signaling System Number 7 TCP Transmission ControlProtocol TE Terminal equipment TDMA Narrowband digital TDMA standard; uses same frequencies as AMPS, thus is also known as D-AMPS or digital AMPS TS Time slot