Migration from GSM network to GPRS seminar or presentation report
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01-10-2010, 04:48 PM
The aim of this paper is to understand the architecture of the GPRS and focus primarily on the issue come up while migrating from existing GSM network to that of GPRS.The migration path from GSM to GPRS requires additional packet switching nodes, software upgrades in the base station subsystem. The existing GSM nodes to upgrade with GPRS functionally, command data service to provide for this GPRS operation need to deploy other elements access serves and firewalls
The general packet radio system is a new non-voice value added service allows information to be sent and received across mobile telephone networks .it supplements today’s circuit switched data and short message service.
With the growing data traffic internet world today, the need often look better methodologies to meet the upcoming demand of internet user has become inevitable GPRS has evolved the mobile user by enabling them to access the internet would incessantly.
It would a GPRS uses a packet-mode technique to transfer high-speed and low-speed data and signaling in an efficient manner over GSM radio networks. GPRS optimizes the use of network resources and radio resources. Strict separation between the radio subsystem and network subsystem is maintained, allowing the network subsystem to be reused with other radio access technologies. GPRS does not mandate changes to an installed MSC base also provide a massive boost to the mobile data communication.
The General Packet Radio System (GPRS) is a new service that provides actual packet radio access for mobile Global System for Mobile Communications (GSM) and Time-Division Multiple Access (TDMA) users. The main benefits of GPRS are that it reserves radio resources only when there is data to send and it reduces reliance on traditional circuit-switched network elements. The increased functionality of GPRS will decrease the incremental cost to provide data services, an occurrence that will, in turn, increase the penetration of data services among consumer and business users. In addition, GPRS will allow improved quality of data services as measured in terms of reliability, response time, and features supported. The unique applications that will be developed with GPRS will appeal to a broad base of mobile subscribers and allow operators to differentiate their services. These new services will increase capacity requirements on the radio and base-station subsystem resources. One method GPRS uses to alleviate the capacity impacts is sharing the same radio resource among all mobile stations in a cell, providing effective use of the scarce resources. In addition, new core network elements will be deployed to support the high burst ness of data services more efficiently.
The General Packet Radio Service (GPRS) is a new non voice 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 Positioning System), a similar acronym that is often used in mobile contexts.
In addition to providing new services for today's mobile user, GPRS is important as a migration step toward third-generation (3G) networks. GPRS will allow network operators to implement a IP-based core architecture for data applications, which will continue to be used and expanded upon for 3G services for integrated voice and data applications. In addition, GPRS will prove a testing
and development area for new services and applications, which will also be used in the development of 3G services.
In addition to the GPRS timeline, it is necessary to investigate the 3G deployment timeline. Because many GPRS operators are either planning to deploy or are investigating 3G, GPRS can be seen as a migration step toward 3G. Several proof-of-concept type trials are currently under way, and these trials will lead to more technical- and application-oriented trials in early 2001. As with GPRS, terminal and infrastructure availability are driving factors. In addition, completion of the licensing process is a necessary step for commercial deployment.
2. GLOBAL SYSTEM FOR MOBILE COMMUNICATION (GSM)
Global system for mobile(GSM) is a second generation cellular system standard that was developed to solve the fragmentation problems of the first cellular systems in Europe’s is the world’s first cellular system to specify the digital modulation and network level architecture and services. Before GSM, European countries used different cellular standards throughout the continent, and it was not possible for customer to use a single subscriber unit throughout Europe. GSM’s success has exceeded the expectations of virtually everyone, and it is now the world’s most popular standard for new cellular radio and personal communication equipment throughout the world.
A variety of data service is offered by GSM. GSM users can send and receive data, at rates up to 9600 bps. A unique feature of GSM is short message services (SMS). SMS is bidirectional service for alphanumeric (up to 160 bytes) messages. The access method chosen by GSM is combination of time and frequency division multiple access (TDMA/FDMA).The FDMA part involves the division by frequency of the (maximum) 25 MHz bandwidth of 124 carrier frequencies spaced 200KHz apart. One or more carrier assigned to each base station .each of this frequency is then divided in time, using a TDMA scheme. Eight burst periods are grouped into TDMA frames, which form the basic unit for definition of logical channels. The type of switching used in GSM network is circuit switching.
GSM was first introduced in European market in 1991. By the end of 1993, several Non-European countries in North America, Asia and Australia had adopted GSM and the technically equivalent offshoot, DCS 1800, which supports personal communication Services (PCS) in the 1.8Ghz to 2Ghz radio bands recently created by governments throughout the world.
3. FEATURES OF GPRS
3.1 Key user features of GPRS
GPRS has several unique features which can be summarized as:
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.
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.
3.1.3 New and better application
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..
3.1.4 Service access
To use GPRS, users specifically need:
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.
Knowledge of how to send and/ or receive GPRS information using their specific model of 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.
Having looked at the key user features of GPRS, let’s look at the key features from a network operator perspective.
3.2 Key Network Features of GPRS
3.2.1 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 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 puzzle represents 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 itself is another example of a packet data network, the most famous of many such network types.
3.2.2 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.
3.2.3 Internet aware
For the first time, GPRS fully enables Mobile Internet functionality by allowing networking 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 and suppliers. These are all derivatives of the World Wide Web aimed at connecting different communities of interest.. 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.
3.2.4 Supports TDMA and GPRS
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.
4. 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.
4.1 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, 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.
5. 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, some new network elements, interfaces, and protocols that handle packet traffic are required. Therefore, GPRS requires modifications to numerous network elements, as summarized in Table 1 and illustrated in Figure 5.1.
Table 5.1: Modifications Required for GPRS
GSM Network Element Modification or Upgrade Required for GPRS
Subscriber Terminal (TE) A totally new subscriber terminal is required to access GPRS services. These new terminals will be backward compatible with GSM for voice calls.
BTS A software upgrade is required in the existing base transceiver site (BTS).
BSC The base station controller (BSC) will also require a software upgrade, as well as the installation of a new piece of hardware called a packet control unit (PCU). The PCU directs the data traffic to the GPRS network and can be a separate hardware element associated with the BSC.
Core Network The deployment of GPRS requires the installation of new core network elements called the Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN).
Databases All the databases involved in the network will require software upgrades to handle the new call models and functions introduced by GPRS.
5.1. GPRS Reference Architecture
5.1.1 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 compatible with GSM for making voice calls using GSM.
5.1.2 GPRS BSS
Each BSC will require the installation of one or more PCUs and a software upgrade. 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.
5.1.3 GPRS Network
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. SGSNs detect new GPRS MSs in a given service area, 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 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.
5.1.4 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 are used 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.
6. 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. 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
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.
6.1.1 Intranet Access
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]).
6.1.2 Internet Access
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 Internet as an environment for carrying out business, through e-commerce.
6.1.3 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.
6.1.4 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.
6.1.5 Textual and visual information
A wide range of content can be delivered to mobile phone users ranging from share prices, sports scores, weather, flight information, news headlines, prayer reminders, lottery results, jokes, horoscopes, traffic, location sensitive services and so on. This information need not necessarily be textual- it may be maps or graphs or other types of visual information.
The length of a short message of 160 characters suffices for delivering information when it is quantitative- such as a share [censored] or a sports score or temperature. When the information is of a qualitative nature however, such as a horoscope or news story, 160 characters is too short other than to tantalize or annoy the information recipient since they receive the headline or forecast but little else of substance. As such, GPRS will likely be used for qualitative information services when end users have GPRS capable devices, but SMS will continue to be used for delivering most quantitative information services. Interestingly, chat applications are a form of qualitative information that may remain delivered using SMS, in order to limit people to brevity and reduce the incidence of spurious and irrelevant posts to the mailing list that are a common occurrence on Internet chat groups.
6.1.6 Still images
Still images such as photographs, pictures, postcards, greeting cards and presentations, static web pages can be sent and received over the mobile network as they are across fixed telephone networks. It will be possible with GPRS to post images from a digital camera connected to a GPRS radio device directly to an Internet site, allowing near real-time desktop publishing.
6.1.7 Moving images
Over time, the nature and form of mobile communication is getting less textual and more visual. The wireless industry is moving from text messages to icons and picture messages to photographs and blueprints to video messages and movie previews being downloaded and on to full blown movie watching via data streaming on a mobile device.
Sending moving images in a mobile environment has several vertical market applications including monitoring parking lots or building sites for intruders or thieves, and sending images of patients from an ambulance to a hospital. Video-conferencing applications, in travel agent to make a decision. Anywhere somebody can benefit from having and being able to comment on a visual depiction of a situation or matter, such collaborative working can be useful. By providing sufficient bandwidth, GPRS facilitates multimedia applications such as document sharing.
6.1.8 Home automation
Home automation applications combine remote security with remote control. Basically, you can monitor your home from wherever you are- on the road, on holiday, or at the office. If your burglar alarm goes off, not only do you get alerted, but you get to go live and see who are perpetrators are and perhaps even lock them in. Not only can you see things at home, but you can do things too. You can program your video, switch your oven on so that the preheating is complete by the time you arrive home (traffic jams permitting) and so on. Your GPRS capable mobile phone really does become like the remote control devices we use today for our television, video, hi-fi and so on. As the Internet Protocol (IP) will soon be everywhere- not just in mobile phones because of GPRS but all manner of household appliances and in every machine- these devices can be addressed and instructed. A key enabler for home automation applications will be Bluetoc which allows disparate devices to interwork. In addition, GPRS will prove a testing and development area for new services and applications, which will also be used in the development of 3G services.
In addition to the GPRS timeline, it is necessary to investigate the 3G deployment timeline. Because many GPRS operators are either planning to deploy or are investigating 3G, GPRS can be seen as a migration step toward 3G. Several proof-of-concept type trials are currently under way, and these trials will lead to more technical- and application-oriented trials in early 2001. As with GPRS, terminal and infrastructure availability are driving factors. In addition, completion of the licensing process is a necessary step for commercial deployment. These factors are illustrated in Figure 4.
6.1.9 Remote LAN access
When mobile workers are away from their desks, they clearly need to connect to the Local Area Network in their office. Remote LAN applications encompasses access to any applications that an employee would use when sitting at their desk, such as access to the intranet, their corporate email services such as Microsoft Exchange or Lotus Notes and to database applications running on Oracle or Sybase or whatever. The mobile terminal such as handheld or laptop computer has the same software programs as the desktop on it, or cut down client versions of the applications accessible through the corporate LAN. This application area is therefore likely to be a conglomeration of remote access to several different information types- email, intranet, and databases. This information may all be accessible through web browsing tools, or require proprietary software applications on the mobile device. The ideal bearer for Remote LAN Access depends on the amount of data being transmitted, but the speed and latency of GPRS make it ideal.
6.2 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:
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.
Several value-added services are outlined in the following sections.
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.
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.
6.2.3 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.
6.3 Location-Based Services and Telemetric
Location-based services provide the ability to link push or pull information services with a user's location. Examples include hotel and restaurant finders, roadside assistance, and city-specific news and information. This technology also has vertical applications such as workforce management and vehicle tracking.
6.3.1 Vehicle positioning
This application integrates satellite positioning systems that tell people where they are with nonvoice mobile services that let people tell others where they are. The Global Positioning System (GPS) is a free-to-use global network of 24 satellites run by the US Department of Defense. Anyone with a GPS receiver can receive their satellite position and thereby find out where they are. Vehicle positioning applications can be used to deliver several services including remote vehicle diagnostics, ad-hoc stolen vehicle tracking and new rental car fleet tariffs.
The Short Message Service is ideal for sending Global Positioning System (GPS) position information such as longitude, latitude, bearing and altitude. GPS coordinates are typically about 60 characters in length. GPRS could alternatively be used.
6.4 Vertical Applications
In the mobile environment, vertical applications apply to systems utilizing mobile architectures to support the carrying out of 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
The General Packet Radio System (GPRS) is a new service that provides actual packet radio access for mobile Global System for Mobile Communications (GSM) and time-division multiple access (TDMA) users. These new services will increase capacity requirements on the radio and base-station subsystem resources
GPRS will provide a massive boost to mobile data usage and usefulness. That much seems assured from its flexible feature set, its latency and efficiency and speed. The only question is how soon it takes off in earnest and how to ensure that the technical and commercial features do not hinder its widespread use.