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  1. 1. General Packet Radio Service: An In-Depth Introduction Damien Dennis EE583WS Spring 2003 5/2/03 1
  2. 2. Table of Contents Abstract 4 Introduction 5 Basics 6 Roots of GPRS 9 Problems/Solutions 12 Architecture 15 Network/Industry Features 19 Summary 22 Appendix 23 References 30 2
  3. 3. List of Figures Roadmap of Data Services for GSM 9 Comparison of Data Transfer Speeds 10 GPRS History 11 GPRS Protocol Stack 16 GSM System Architecture 16 GPRS System Architecture 17 GPRS Contracts Awarded 21 Technical Feature Listing 24 Standard Library Functions 26 Glossary 27 3
  4. 4. Abstract GPRS (General Packet Radio Service) is a step between GSM and 3G cellular networks. GPRS offers faster data transmission via a GSM network within a range 9.6Kbits to 115Kbits. This new technology makes it possible for users to make telephone calls and transmit data at the same time. (For example, if you have a mobile phone using GPRS, you will be able to simultaneously make calls and receive e-mail massages.) This paper will entail an intermediate language and serves to introduce this technology to both the developer and end-user alike. I discuss the underlying architecture and basic functionality of GPRS followed by its many applications. 4
  5. 5. Introduction The introduction of wireless communication has allowed many people around the world to live their lives and conduct business in ways that were never before possible. Millions of cellular subscribers have become accustomed to always having a telephone with them wherever they go. Now, businesses are wanting to be able to connect to the office when they are out of the office so they can check their email, search on the Internet, access company files, send faxes and data whenever and wherever it is needed. Currently, there are numerous wireless data services available, but a new technology, General Packet Radio Service, offers much excitement to consumers. Primitive (2G) cellular data services do not fulfill the needs of users add providers. From the user's point of view, data rates are too slow and the connection setup takes too long and is rather complicated. Moreover, the service is too expensive for most users. From the technical point of view, the drawback results from the fact that current wireless data services are based on circuit switched radio transmission. Before introduction of GPRS, the radio capacity was used for calls and data transmission within the GSM (Global System Mobile) network in a rather inefficient way. For data transmission the entire channel was occupied and was thus insufficiently used. With the GPRS technology, the channel is used more efficiently owing to the possibility of more than one user sharing the same channel. GPRS telephones user several channels for data transfer thus facilitating greater transfer speeds. The GPRS infrastructure and mobile phones support a data transmission speed of up to 13.4Kbits per channel. I will treat GPRS from the point of view of GSM because GPRS is a new bearer service for GSM that serves to improve and simplify wireless access to packet data networks, e.g., to the Internet. It applies a packet radio principle to transfer user data packets in an efficient way between GSM mobile stations and external packet data networks. Packets can be directly routed from the GPRS mobile stations to packet switched networks. Networks based on the Internet Protocol (IP) (e.g. private/corporate intranets) and X.25 networks are supported in the current version of GPRS. Users of GPRS benefit from shorter access times and higher data rates. In conventional GSM, the connection setup takes several seconds and rates for data transmission are restricted to 9.6 kbit/s. Ideally, GPRS in practice offers session setup times below one second In addition, GPRS packet transmission offers a more user-friendly billing than that offered by circuit switched services. In circuit switched services, billing is based on the duration of the connection. This is unsuitable for applications with bursty traffic (e.g. Internet traffic). The user must pay for the entire airtime, even for idle periods when no packets are sent (e.g., while the user reads a Web page or email). In contrast to this, with packet 5
  6. 6. switched services, billing can be based on the amount of transmitted data. The advantage for the user is that he or she can be "online" over a long period of time but will be billed based on the transmitted data volume. On this positive note let me present the General Packet Radio Service and its significance in leading us to the modern 3G technologies. 1 Basics GPRS makes sending and receiving small bursts of data, such as email and web browsing, as well as large volumes of data over a mobile telephone network possible. A simple way to understand packet switching is to relate it to a jigsaw puzzle. Image how you buy a complete image or picture that has been divided up into many pieces and then placed in a box. You purchase the puzzle and reassemble it to form the original image. Before the information is sent, it is split up into separate packets and it is then reassembled at the receivers end. Some of the basic/prerequisite knowledge of GPRS follows. GPRS Telephones -Due to the fact that more than one channel is used for downlink, the GPRS mobile phones make possible greater data transmission speeds. There are several types of phones with regard to the number of channels they use for data transmission... • Type 2+1 – two downlink channels and one uplink data transmission channel • Type 3+1 – three downlink channels and one uplink data transmission channel • Type 4+1 – four downlink channels and one uplink data transmission channel -The GPRS mobile phones can be classified into the following three classes in terms of the possibility of simultaneous calls (via GSM) and data transmission (via GPRS)... 6
  7. 7. • Class A – Simultaneous calls (via GSM) and data transmission (via GPRS) • Class B – Automatic switching between the GSM and the GPRS mode is possible according to telephone settings. • Class C – Hand operated switching between the GSM and the GPRS mode Data Transmission Speeds -The supported data transmission speed per channel is 13.4Kbits. Depending on the type of phone, the following data transmission speeds are theoretically possible: • Type 2+1: Receive 26.8Kbits and send 13.4Kbits. • Type 3+1: Receive 40.2Kbits and send 13.4Kbits. • Type 4+1: Receive 53.6Kbits and send 13.4Kbits. The Network In the core network, the existing MSCs (Mobile Services Switching Centers) are based upon circuit-switched technology, and they cannot handle the GPRS style packet traffic. Thus two new and very important 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. GGSNs are used as interfaces to external IP networks such as the public Internet, other mobile service providers' GPRS services. 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, as well as authentication and charging functions. 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. 7
  8. 8. Security I would like to briefly mention GPRS security in order to “qualify” its integrity. Its security functionality is equivalent to the existing GSM security. The SGSN performs authentication and cipher setting procedures based on the same algorithms, keys, and criteria as in existing GSM. GPRS uses a ciphering algorithm optimized for packet data transmission. -For more details on GSM security visit http://www.sans.org/rr/telephone/GSM_standard.php 8
  9. 9. 2 Roots of GPRS As I stated GPRS will complement rather than replace the current data services available through today’s GSM digital cellular networks, such as Circuit Switched Data and Short Message Service. It also provides the type of data capabilities planned for “third generation” cellular networks, but years ahead of them. Figure 1 below is a timeframe of GSM data services and their availability. Figure 1: Roadmap of Data Services for GSM Timeframe Capabilities Notes 9.6 kbps service Available today Circuit-switched data Service available from and fax most GSM operators today. 14.4 kbps service Available today Higher speed circuit- Works identically to switched data and fax 9.6 kbps service only at higher speed Direct IP Access Available through Circuit-switched Reduces call set-up some carriers today connection directly to time and provides a Internet stepping-stone to packet data. High-speed circuit- Available today High speed rates to 56 A software-only switched data service kbps upgrade for carriers (HSCSD) not requiring expensive infrastructure. GPRS Available today High speed packet Extremely capable and data with transmission flexible mobile speeds over 100 kbps, communications. with most user devices offering about 56 kbps EDGE Available within three High speed packet Final high-speed data years data which will triple technology for the rates available existing networks. with GPRS Third generation Available within three High speed packet Completely new cellular to five years data to 2 Mbps airlink. Source: Paper: General Packet Radio Service (GPRS), September 30, 1998 9
  10. 10. According to the specifications provided by the European Telecommunications Standards Institute (ETSI), the highest speed for a single user session (or time slot) is the coding scheme CS4, which allows 21.4 kbps per time slot. Thus, theoretically, a GPRS connection can provide a data transmission speed of up to 171.2 Kbps (approximately three times that of a fixed-line 56K dial-up) if all eight slots are used. GPRS’s rival, HSCSD, can achieve up to 57.6 kbps. However, it is unlikely that network operators will let a single user use up all the time slots. Even Nokia admitted that realistically GPRS could achieve only about 43 Kbps while Ericsson thinks 56 Kbps is achievable. Currently, GSM systems are running at 9.6 kilobits. A comparison of Data Transfer Speeds (in kbps) follows in Figure 2. Figure 2: A Comparison of Data Transfer Speeds (in Kbps) 56 K GSM HSCSD GPRS GPRS Dial-Up (maximum speed) (maximum speed) (realistic speed) 56 9.6 57.6 171.2 43 to 56 Source: A CNET tutorial, July 2001. GPRS could possibly be the technology that will allow consumers to really begin to pursue the mobile Internet. GPRS is considered one step ahead of HSCSD (High Speed Circuit Switched Data) and a step towards 3G (Third- generation) networks. It is the step to 2.5G for GSM and TDMA (Time Division Multiple Access) service providers. GPRS is ideal for Wireless Application Protocol (WAP) services because of the cost saving WAP over GPRS bring to mobile operators and cellular consumers. Costs are reduced because GPRS radio resources are only needed while the message is being transferred. For the end user, that means you only pay for the time it takes to download the data and information that you need. For the GSM operator, that means that you will be able to provide high speed Internet access to consumers at a reasonable cost, because you will bill mobile phone users for only the amount of data that they transfer rather than billing them for the length of them that they are connected to the network. With GPRS-enabled mobile phones, services are received faster than with traditional GSM phones. GPRS offers an increase in data throughput rates, so information retrieval and database access is faster, more usable and more convenient. At its best, GPRS is transparent, allowing the user to concentrate on the task in hand rather than on the technology. 10
  11. 11. History Like the GSM standard itself, GPRS will be introduced in phases. Phase 1 became available commercially in the year 2000/2001. Point to Point GPRS, which is sending information to a single GPRS user, was supported, but not Point to Multipoint which is sending the same information to several GPRS users at the same time. GPRS Phase 2 supports higher data rates through the possible incorporation of techniques such as EDGE (Enhanced Data rates for GSM Evolution), in addition to Point-to-Multipoint support. See Figure 3 below for a timeline history of GPRS. Figure 3: GPRS History DATE MILESTONE Throughout Network operators place trial and commercial contracts for GPRS 1999-2000 infrastructure. Incorporation of GPRS infrastructure into GSM networks. Summer of 2000 First trial GPRS services become available. Typical single user throughput is likely to be 28 kbps. For example, T-Mobil is planning a GPRS trial at Expo2000 in Hanover in the Summer of 2000. Start of 2001 Basic GPRS capable terminals begin to be available in commercial quantities. Throughout 2001 Network operators launch GPRS services commercially an roll out GPRS. Vertical market and executive GPRS early adopters begin using it regularly for nonvoice mobile communications. 2001/2002 Typical single user throughput is likely to be 56 kbps. New GPRS specific applications, higher bitrates, greater network capacity solutions, more capable terminals become available, fueling GPRS usage. 2002 Typical single user throughput is likely to be 112 kbps. GPRS Phase 2/EDGE begins to emerge in practice. 2002 GPRS is routinely incorporated into GSM mobile phones and has reached critical mass in terms of usage. (This is the equivalent to the status of SMS in 1999) 2002/2003 3GSM arrives commercially. Source: An Introduction to the General Packet Radio Service, January 2000 11
  12. 12. 3 Problems/Solutions --Note: As we now get to a more technical portion it may be of value to check the appendix for Technical features listings, as well as a Glossary of terms/acronyms SHORTCOMINGS LIMITED RADIO RESOURCES There are only limited radio resources that can be deployed for different uses – use for one purpose precludes simultaneous use for another. For example, voice and GPRS calls both use the same network resources. SPEEDS MUCH LOWER IN REALITY Attaining the highest GPRS data transmission speed of 171.2 kbps would require a single user taking over all eight timeslots; therefore, maximum GPRS speeds should be compared against constraints in the GPRS terminals and networks. It is highly unlikely that a GSM network operator would allow all timeslots to be used by a single GPRS user. The initial GPRS terminals are expected to only support one to three timeslots, which will be severely limiting to users. The reality is that mobile networks are always likely to have lower data transmission speeds than fixed networks. Mobile cellular subscribers often like to jump on the fact that a certain technology has high data transmission speeds, when the figure in all reality could be a theoretical number that is based on the perfect situation. Consumers should, therefore, compare all available mobile services and use the one that bests suits their needs. NO SUPPORT OF MOBILE TERMINATED CALLS There has been no confirmation by any mobile phone provider that initial GPRS terminals will support mobile terminated GPRS calls (receipt of GPRS calls on the mobile phone). When a mobile phone user initiates a GPRS session, they are agreeing to pay for the content to be delivered by the GPRS service. Internet sources originating unsolicited content may not be chargeable. A worse case scenario would be that a mobile user would then be made responsible for paying for the unsolicited junk content that they received. This is one main reason why mobile vendors are not willing to support mobile terminated GPRS calls in their terminals. SUBOPTIMAL MODULATION GPRS is based on a modulation technique known as Gaussian minimum- shift keying (GMSK). EDGE is based on a new modulation scheme that allows a much higher bit rate across the air interface – that is called eight-phase-shift keying (8 PSK) modulation. Since 8 PSK will also be used for 3GSM, network 12
  13. 13. operators will need to incorporate it at some stage to make the transition to third generation mobile phone systems. TRANSIT DELAYS GPRS packets are sent in many different directions to reach the same destination. This makes room for the possibility for some of the packets to get lost or damaged during the transmission over the radio link. The GPRS standards are aware of this issue regarding wireless packet technologies and have worked to integrate data integrity and retransmission approaches to solving these problems. The result of this leads to possible transit delays. NO STORE AND FORWARD Currently, there is not a storage mechanism integrated into the GPRS standard. PROPOSED SOLUTION General Packet Radio Service comes to the market after High-speed circuit-switched data service (HSCSD) is already in use as an update to the services that it already offers. GPRS is a step in front of HSCSD and a step closer to 3G. Not only will it increase data transmission speeds, but GPRS will also offer the following user features and network features. USER FEATURES 3 TO 10 TIMES THE SPEED The maximum speed of 171.2 kbps, available through GPRS, is nearly three times as fast as the data transmission speeds of fixed telecommunications networks and ten times as fast as the current GSM network services. INSTANT CONNECTIONS – IMMEDIATE TRANSFER OF DATA GPRS allows for instant, continuous connections that will allow information and data to be sent whenever and wherever it is needed. GPRS users are considered to be always connected, with no dial-up needed. 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 AND BETTER APPLICATIONS General Packet Radio Service offers many new applications that were never before available to users because of the restrictions in speed and messaged length. Some of the new applications that GPRS offers is the ability to 13
  14. 14. perform web browsing and to transfer files from the office or home and home automation, which is the ability to use and control in-home appliances. SERVICE ACCESS To use GPRS, the user will need: • A subscription to a mobile telephone network that supports GPRS – use of GPRS must be enabled for that user. Automatic access to the GPRS may be allowed by some mobile network operators, others will require a specific opt-in • Knowledge of how to send and/or receive GPRS information using their specific model of mobile phone, including software and hardware configuration (this creates a customer service requirement) • A destination to send or receive information through GPRS. (Whereas with SMS this was often another mobile phone, in the case of GPRS, it is likely to be an Internet address, since GPRS is designed to make the Internet fully available to mobile users for the first time. Tremendously widening the limits and uses of mobile connections, GPRS users can access any web page or other Internet applications. 14
  15. 15. 4 Architecture Network Protocols Used There are several protocols used in the network equipment. These protocols operate in both the data and signalling planes. The following is a brief description of each protocol layer shown in Figure 4 on the next page. • Sub-Network Dependent Convergence Protocol (SNDCP): the protocol that maps a network-level protocol, such as IP or X.25, to the underlying logical link control. SNDCP also provides other functions such as compression, segmentation and multiplexing of network-layer messages to a single virtual connection. • Logical Link Control (LLC): a data link layer protocol for GPRS which functions similar to Link Access Protocol - D (LAPD). This layer assures the reliable transfer of user data across a wireless network. • Base Station System GPRS Protocol (BSSGP): BSSGP processes routing and quality of service (QoS) information for the BSS. BSSGP uses the Frame Relay Q.922 core protocol as its transport mechanism. • GPRS Tunnel Protocol (GTP): protocol that tunnels the protocol data units through the IP backbone by adding routing information. GTP operates on top of TCP/UDP over IP. • GPRS Mobility Management (GMM): protocol that operates in the signalling plane of GPRS and handles mobility issues such as roaming, authentication, and selection of encryption algorithms. • Network Service: protocol that manages the convergence sub-layer that operates between BSSGP and the Frame Relay Q.922 Core by mapping BSSGP's service requests to the appropriate Frame Relay services. • BSSAP+: protocol that manages paging for voice and data connections and optimizes paging for mobile subscribers. BSSAP+ is also responsible for location and routing updates as well as mobile station alerting. The efficiency and language of these briefs comes from the editing of architectural descriptions by: H. Granbohm and J. Wiklund, GPRS: General Packet Radio Service, Ericsson Review, vol. 76, no. 2, pp. 19-21, 2000. 15
  16. 16. -Figure 4 shows the GPRS protocol stack, Figures 5 and 6 show the GMS system architecture and GPRS architecture respectively. I will discuss Figures 5 next. Figure 4 --In order to fully understand the building blocks of our topic, GPRS, it suffices to first look at the make-up of the GMS system. Figure 5 – GMS System Architecture (Source: Betterstetter et. al.) 16
  17. 17. GMS Architecture Figure 5 shows the basic architecture of the public land mobile network (PLMN) inherent to GSM technology. Other essential components are listed and convenient legends exist at the bottom (thanks to Bettstetter et.al). The cell is defined by the radio coverage of a base transceiver station (BTS). The BSC (base station controller) controls several of these BTSs together, and these two components together form the base station subsystem (BSS). The mobile switching center routes the traffic of all of the mobile stations in the respective cells. In the event of a connection originating from or terminating in the fixed network, a specific gateway mobile switching center (GMSC) handles the connection. The hierarchy of the GSM network is as follows • 1 MSC assigned to at least one administrative region • Each administrative region is made up of at least one location area (LA) • Several cell groups make up an LA • Each cell group is designated to a BSC Permanent data (e.g. user’s profile) and temporary data (e.g. current user location) are stored in the HLR (home location register – a database). When a call to a user is initiated the HLR is always the first to be contacted, to determine the user’s location. A visited location register (VLR) stores the data of those users who are currently in its area of responsibility (a group of location areas [LAs]). The AUC serves security purposes and stores data such as keys for encryption and authentication. Finally, the EIR – equipment identity register – keeps track of equipment data rather than subscriber data. Figure 6 – GPRS System Architecture (Source: Betterstetter et. al.) 17
  18. 18. GPRS Architecture (Figure 6, above) If you’ll recall, in Chapter 1 (basics) we talked of two groundbreaking nodes that make GPRS possible. • Serving GPRS Support Node (SGSN) • Gateway GPRS Support Node (GGSN) These support nodes are necessary to integrate GPRS into the previously established architecture of GSM. The support nodes (GSN) take on the task of delivering and routing data packets between the mobile stations and the PDNs (packet data network). Figure 6 shows the interfaces between these new nodes and the GSM network. Notice how the signaling data is manipulated The blue Gb interface connects the dinosaur component (BSC) with the SGSN. Using two other, unique interfaces – Gn and Gp – user and signaling data are both transmitted between the GSNs. The Gp interface is only used if the two GSNs are in different PLMNs. Otherwise, the Gn interface is used (GSNs are in the same PLMN). A backbone IP-based GPRS network is used to connect all GSNs. Here the GSNs package the PDN packets and tunnel (transmit) them using the GTP (GPRS tunneling protocol). The type of backbone depends upon whether or not the GSNs exist within the same PLMN. Figure 6 shows two “intra-PLMN” backbones within an “inter-PLMN” network. Intra-PLMN backbones have GSNs within the same PLMN, inter-PLMN networks have GSNs in differing PLMN. 18
  19. 19. 5 Network/Industry Features NETWORK FEATURES GPRS offers many new network features to mobile service operators. These include packet switching, spectrum efficiency, Internet aware, and the support of TDMA and GSM. PACKET SWITCHING From a network operator perspective, GPRS involves overlaying packet based air interference on the existing circuit switched GSM network. This gives the user an option to use a packet-based data service. To supplement a circuit switched network architecture with packet switching is quite a major upgrade. The GPRS standard is delivered in a very elegant manner – with network operators needing only to add a couple of new infrastructure nodes and making a software upgrade to some existing network elements. SPECTRUM EFFICIENCY Packet switching means that GPRS radio resources are used only when users are actually sending or receiving data. Rather than dedicating a radio channel to a mobile data user for a fixed period of time, the available radio resource can be concurrently shared between several users. This efficient use of scarce radio resources means that large number of GPRS users can potentially share the same bandwidth and be served from a single cell. The actual number of users supported depends on the application being used and how much data is being transferred. Because of the spectrum efficiency of GPRS, there is less need to build in idle capacity that is only used in peak hours. GPRS therefore lets network operators maximize the use of their network resources in a dynamic and flexible way, along with user access to resources and revenues. GPRS should improve the peak time capacity of a GSM network since it simultaneously: • ·Allocates scarce radio resources more efficiently by supporting virtual connectivity • ·Migrates traffic that was previously sent using Circuit Switch Data to GPRS instead • ·Reduces SMS Center and signaling channel loading by migrating some traffic that previously was sent using SMS to GPRS instead using the GPRS/SMS interconnect that is supported by the GPRS standards. 19
  20. 20. INTERNET AWARE For the first time, GPRS fully enables Mobile Internet functionality by allowing interworking between the existing Internet and the new GPRS network. Any service that is used over the fixed Internet today – File Transfer Protocol (FTP), web browsing, chat, email, telnet – will be as available over the mobile network because of GPRS. In fact, many network operators are considering the opportunity to use GPRS to help become wireless Internet Service Providers in their own right. The World Wide Web is becoming the primary communications interface – people access the Internet for entertainment and information collection, the intranet for accessing company information and connecting with colleagues and the extranet for accessing customers and suppliers. Web browsing is a very important application for GPRS. Because it uses the same protocols, the GPRS network can be viewed as a sub-network of the Internet with GPRS capable mobile phones being viewed as mobile hosts. This means that each GPRS terminal can potentially have its own IP address and will be addressable as such. SUPPORTS TDMA AND GSM It should be noted that the General Packet Radio Service is not only a service designed to be deployed on mobile networks that are based on the GSM digital phone standard. The IS-136 Time Division Multiple Access (TDMA) standard, popular in North and South America, will also support GPRS. This follows an agreement to follow the same evolution path towards third generation mobile phone networks concluded in early 1999 by the industry associations that support these two network types. INDUSTRY PARTICIPATION The first version of the GPRS standard is complete. The next version of the standard, adds advanced features, such as point-to-multipoint communications. Many GSM vendors, such as Alcatel, Ericsson, Lucent, Motorola, Nokia, Nortel, and Siemens have played an active part in the standards process. Recently, Lucent has announced a deal to bring Verizon to 3G. Cellular service providers currently cover almost 90 percent of the population in the 20
  21. 21. United States. Figure 4 shows GPRS contracts, which currently have been awarded to carriers in Europe, Asia and the United States. Figure 7: GPRS Contracts Awarded Country Carrier GPRS Core Infrastructure Vendor Contract Date Vendor Value Austria Mobilkom Nortel Motorola/Nokia BSS an Nortel NA 7/99 (TRIAL) NSS Austria TELE.RING Alcatel Alcatel BSS + NSS + Microwave NA 5/20/99 Belgium Belgacom Motorola Siemens switches, Motorola, NA 3/15/99 Alcatel and Nokia base stations Denmark Sonofon Nokia Nokia 6/2/99 Finland Radiolinja Nokia Nokia NA NA Finland Sonera Nokia Nokia NA 2/23/99 Finland Sonera Ericsson Nokia NA 6/99 France France Telecom Alcatel Alcatel and Ericsson Mobile NA 4/2/99 (TRIAL) Switches, Alcatel, Nortel and Motorola Base Stations France France Telecom Motorola As above NA 3/99 (TRIAL) France SFR/Cegetel Alcatel Alcatel and Ericsson mobile NA 10/21/98 switches, Alcatel, Motorola, Nokia base stations France Bouygues Nortel Nortel and Nokia BSS, Ericsson NA 7/99 Telecom (TRIAL) NSS Germany T-Mobil Ericsson Alcatel and Siemens NA 1/26/99 switches.Alcatel, Motorola and Lucent base stations Germany T-Mobil Alcatel As above NA 2/23/99 Germany Mannesmann Siemens Siemens NA 6/99 D2 Netherlands Telfort Ericsson Ericsson NA 2/23/99 Poland PTC/Era Siemens Siemens NA 6/99 Poland Polkomtel Nokia Nokia NA NA Scandinavia Siemens 2/9/99 UK BT Cellnet Motorola Motorola $50 mil 3/18/99 UK One2One Ericsson Ericsson $45 mil 5/12/99 Australia C&W Optus Nortel Nokia BSS, Nortel NSS $33 mil 7/99 Hong Kong Sunday Nortel Nortel NSS, Nortel BSS NA 5/99 Hong Kong Hongkong Nokia HK$40-50 7/6/99 Telecom m Hong Kong Smartone Ericsson Ericsson NA NA Singapore Mobile One Nokia NA 2/8/99 Taiwan KGTelecom Nokia $100 mil 21
  22. 22. USA Omnipoint Ericsson Ericsson NA (TRIAL) Source: An Introduction to General Packet Radio Service, August 1, 2001 [7] SUMMARY GPRS gives subscribers access to data communication applications such as e-mail, corporate networks, and the Internet using their mobile phones. The GPRS service uses the existing GSM network and adds new packet-switching network equipment. GPRS employs packet switching, which means that the GPRS mobile phone has no dedicated circuit assigned to it. Only when data is transferred is a physical channel created. After the data has been sent, it can be assigned to other users. This allows for the most efficient use of the network. When packet-switched data leaves the GPRS/GSM network, it is transferred to TCP-IP networks such as the Internet or X.25.Thus, GPRS includes new transmission and signaling procedures as well as new protocols for interworking with the IP world and other standard packet networks. Mobile phones currently available do not work with the new GPRS technology. The industry’s mobile phone vendors are working on both existing and new phones that will support both GSM and packet switching. It is also becoming more common for laptops and PDA’s (Personal Digital Assistants) to have a GPRS phone integrated in them. Perfectly dubbed a 2.5G system the General Packet Radio Service has bridged us to the 3G (UMTS) of today. 22
  23. 23. APPENDIX 23
  24. 24. Technical Feature Listing Data rate: Maximum of 171.2 kbps Channel coding Outer block coding Inner Convolutional coding Interleaving scheme for error bursts Modulation Gaussian Minimum Shift Keying GMSK Multiple Access Combination of TDMA & FDMA Transmit Frequency bands Mobile station Uplink Reverse ch. 890 – 915 MHz Base station Downlink Forward ch. 935 – 960 MHz Duplex seperation 45 MHz RF carrier spacing 200 kHz Total number of RF Duplex channels 124 Number of TDMA slots on each carrier 8 Channel allocation 1 to 8 time slots per TDMA One time slot (Physical channel) 0.577 ms Frame Interval: 4.615 ms Asymmetric data traffic different time slots for Uplink and downlink Frequency Hopping: 217 hops/s (slow) Equalizer: 16 µs time dispersion Connectivity: Packet switched data networks such as IP and X.25 24
  25. 25. Extra nodes: Gateway GPRS Support Node (GGSN) and Serving GPRS Support Node (SGSN) Composed of Packet data traffic channels Packet common control channels Packet dedicated control channels Packet data broadcast control channel (only for forward link) Transmission Channel coder Block encoder Precoding of Uplink Status Flag (USF) Add Tail bits Convolutional encoder Puncturing Channel coding schemes Scheme Peak Rate per slot (kbps) RLC Block size Code rate CS-1 9.05 181 .5 CS-2 13.4 268 .66 CS-3 15.6 312 .75 CS-4 21.4 428 1.0 Reception GMSK Demodulator Viterbi Equalizer Deinterleaver Viterbi decoding 25
  26. 26. Standard Library Functions The following is a list of the standard library functions to perform the various aspects of GPRS. These functions can be implemented in a DSP or the ARM RISC architecture. The channel models are used for simulating the channel operating environment and are not a function that would be implemented in a mobile handset or base station. Channel coders Block encoder Fire coder Precoding of uplink status flags Convolutional coder (1/2, 2/3 and 3/4) Puncturing Interleaver / deinterleaver Interleaver of depth 4 / deinterleaver Channel models Rayleigh distribution Rice distribution Propogation models for urban and rural areas Modulator / demodulator GMSK modulation / demodulation Channel decoder Viterbi decoder 26
  27. 27. Glossary 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 (Universal Telecommunications 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 Host Configuration Protocol DNS Domain Name System EDGE Enhanced data rates for GSM evolution; upgrade to GPRS systems that requires new base stations and claims to increase bandwidth to 384 kbps ETSI European Telecommunications Standards Institute Gb Interface between a SGSN and a BSS Gc Interface between a GGSN and a HLR Gd Interface between a SMS-GMSC and a SGSN, and between a SMS-IWMSC and a SGSN Gf Interface between a SGSN and an EIR GGSN Gateway GPRS Support Node Gi Reference point between GPRS and an external packet data network GIWU GSM interworking unit GMSC Gateway mobile services switching center Gn Interface between two GSNs within the same PLMN Gp Interface between two GSNs in different PLMNs GPRS General Packet Radio Service; upgrade to existing 2G digital mobile networks to provide higher-speed data services Gr Interface between a SGSN and a HLR Gs Interface between a SGSN and a MSC/VLR GSM Global System for Mobile Communications; most widely deployed 2G digital cellular mobile network standard GSN GPRS Support Node (xGSN) GTP GPRS Tunneling Protocol GW Gateway HDLC High-Level Data Link Control HLR Home location register HSCSD High-speed circuit-switched data; software upgrade for cellular networks that gives each subscriber 56K data IP Internet Protocol ISP Internet service provider L2TP Layer two Tunneling Protocol 27
  28. 28. 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 Support System PCU Packet control unit PDA Personal digital assistant PDN Packet data network PDP Packet Data Protocol PLMN Public Land Mobile Network; generic name for all mobile wireless networks that use earth base stations rather than satellites; the mobile equivalent of the PSTN PSPDN Packet Switched Public Data Network PSTN Public Switched Telephone Network PVC Permanent virtual circuit QoS Quality of service RADIUS Remote Authentication Dial-In User Service RLP Radio Link Protocol SGSN Serving GPRS Support Node SLA Service-level agreement SMS Short message service SMSC Short message service center SS7 Signaling System Number 7 TCP Transmission Control Protocol 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 Um Interface between the MS and the GPRS fixed network part VAS Value-added services VLR Visitor location register VPN Virtual private network WAP Wireless access Protocol; important protocol stack (Layers 4 through 7 of the OSI model), used to send simplified Web pages to wireless devices; uses IP but replaces TCP and Hypertext Transfer Protocol (HTTP) with UDP and WTP, and requires pages to be written in WML rather than in HTML Much of this table comes from the Cisco White Papers REFERENCES Choi, Hahn, TechTV “The High-Speed Wireless World”, http://www.techtv.com/products/consumerelectronics/story/0,23008,3317919,00.html, March 21, 2001 Ericsson “Third Generation Mobile Systems”, http://www.ericsson.com/3g/how/gprs.shtml, August 21, 2001, 28
  29. 29. “General Packet Radio Service”, http://www.utdallas.edu/~kim97/GPRS.htm, “GPRS – General Packet Radio operator Service”, http://translate.google.com/translate_c?hl=en&sl+fr&u=http://mircolease.com/fr/helpd, GPRS, http://whatis.techtarget.com/definition/0,289893,sid9_gci213689,00.html, “GSM Phase 2+ GPRS: Architecture, Protocols, and Air Interface” http://www.comsoc.org/livepubs/surveys/public/3q99issue/bettstetter.html GSM World “An Introduction to the General Packet Radio Service”, http://www.gsmworld.com/technology/yes2gprs.html, August 1, 2001, GSM World “An Overview of GPRS”, http://www.gsmworld.com/technology/gprs.html, August 18, 2000, Khoo, Ernest. “A CNET tutorial: What is GPRS?” http://www.singapore.cnet.com/handphones/wirelesscenter/story/0,2000027283,2009793 4,00.htm, July 19, 2001 Merritt, Tom, TechTV “GPRS Phones”, http://www.techtv.com/freshgear/comdexfall2000/story/0,23008,3011391,00.html, November 13, 2000 Mobile and Wireless Overview “General Packet Radio Service (GPRS), http://www.wheatstone.net/whatwedo/Portal/Standards/gprs.html Mobile GPRS “About the General Packet Radio Service”, http://www.mobilegprs.com/ Motorola “BT Cellnet Showcases World’s First Commercial GPRS High Speed Mobile Data Service At Networks 2000”, http://www.corporate-ir.net/ireye/ir_site.zhtml? ticker=MOT&script=411&layout=-6&item_id…, June 27, 2000 Motorola “GPRS Solutions”, http://www.motorola.com/aspira/GPRS.htm Nokia “GPRS Mobile On-line”, http://www.nokia.com/gprs/, 2001 Nokia 3G Solutions “Mobility Core”, http://www.nokia.com/3g/solutions_mobility_gprs.html, 2001 PsychoSpy and The Clone “A Guide to General Packet Radio Service”, http://www.nettwerked.net/gprs.txt, September 2, 2000 Rysavy, Peter.Network Magazine “Emerging Technology: Clear Signals for General Packet Radio Service”, http://www.networkmagazine.com/article/NMG20001129S0002/3, December 5, 2000 Rysavy, Peter.Network Magazine “Emerging Technology: Clear Signals for General Packet Radio Service”, http://www.rysavy.com/Articles/GPRS2/gprs2.html, December 2000 Rysavy, Peter, “Paper: General Packet Radio Service (GPRS)”, http://www.gsmdata.com/es53060/paprysavy.htm, September 30, 1998 “USA: Simplify GPRS – new GPRS high-speed wireless modem”, http://www.mobileapplicationsinitiative.com/lopsedel/dokument.asp? ID=News7064&Fran=Si Webopedia “GPRS”, http://www.webopedia.com/TERM/G/GPRS.html, August 6, 1999 “What is GPRS?”,http://www.mobiletelecoms.net/what_is_gprs.html White Paper “Cisco - GPRS White Paper”, http://www.cisco.com/warp/public/cc/so/neso/gprs/gprs_wp.htm, July 6, 2000 Wireless Communications Solutions “General Packet Radio Service (GPRS)”, http://www.nuntius.com/solutions22.html 29
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