GPRS: GSM Packet Radio Service



              GPRS
                                                       Internet




 ...
GPRS: GSM Packet Radio Service

• Packet-switched data over GSM
• Interconnects to Internet
• Strict separation between ra...
GPRS Raw Data Rates (kbps)


Coding 1 slot    2 slots 3 slots 4 slots 5 slots 6 slots 7 slots 8 slots
scheme

CS-1      9....
GPRS MSs

      • Three classes of MS
      • Class A MS can operate GPRS and other GSM
        services simultaneously
  ...
GPSR Architecture (data view)

                            SGSN

                                     Gn




             ...
Gateway GPRS Support Node (GGSN)

• used as interface to external packet-switched
  networks
• connected to SGSN via an IP...
GPRS Network Operations

• For GPRS user, network is connectionless
• HOWEVER, a network connection must be
  established ...
Network Access...
   User Registration associates the MS ID with the user
   address
      In home area, HLR is enhanced t...
Mobility Management

• Mobility Management used to track the MS
• SGSNs communicate to update the user location
• Logical ...
GPRS Network Protocols

• Sub-Network Dependent Convergence Protocol
  (SNDCP):
   – maps a network-level protocol, such a...
GPRS Network Protocols...

• GPRS Mobility Management (GMM):
   – handles mobility issues such as roaming, authentication,...
EDGE
(Enhanced Data rate for GSM Evolution)
   • Uses GSM/GPRS, but with higher-level modulation
     (8-PSK instead of GM...
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GPRS: GSM Packet Radio Service

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GPRS: GSM Packet Radio Service

  1. 1. GPRS: GSM Packet Radio Service GPRS Internet School of Information Technologies GPRS-1 Data Services in GSM • Data transmission standardized with only 9.6 kbit/s – advanced coding allows 14.4 kbit/s – not enough for Internet and multimedia applications • HSCSD (High-Speed Circuit Switched Data) – mainly software update – bundling of several time-slots to get higher AIUR (Air Interface User Rate) (e.g., 57.6 kbit/s using 4 slots, 14.4 each) – advantage: ready to use, constant quality, simple – disadvantage: channels blocked for voice transmission AIUR [kbit/s] TCH/F4.8 TCH/F9.6 TCH/F14.4 4.8 1 9.6 2 1 14.4 3 1 19.2 4 2 28.8 3 2 38.4 4 43.2 3 57.6 4 School of Information Technologies GPRS-2
  2. 2. GPRS: GSM Packet Radio Service • Packet-switched data over GSM • Interconnects to Internet • Strict separation between radio subsystem and network subsystem • GPRS does not mandate changes to an installed MSC base GPRS Internet School of Information Technologies GPRS-3 GPRS Channels • 1 to 8 radio interface slots can be allocated per TDMA frame • timeslots are shared by the active users • uplink and downlink slots are allocated separately • radio resources can be shared dynamically between speech and data • 4 Coding Schemes CS1, CS2, CS3, CS4 giving – user data rates of approx. 6, 9, 10, 14 kbps per slot, – raw data rates 9.05, 13.4, 15.6, 21.4 kbps per slot School of Information Technologies GPRS-4
  3. 3. GPRS Raw Data Rates (kbps) Coding 1 slot 2 slots 3 slots 4 slots 5 slots 6 slots 7 slots 8 slots scheme CS-1 9.05 18.2 27.15 36.2 45.25 54.3 63.35 72.4 CS-2 13.4 26.8 40.2 53.6 67 80.4 93.8 107.2 CS-3 15.6 31.2 46.8 62.4 78 93.6 109.2 124.8 CS-4 21.4 42.8 64.2 85.6 107 128.4 149.8 171.2 School of Information Technologies GPRS-5 GPRS Traffic • Supports various traffic classes, from intermittent and bursty transfers, to occasional transfer of large volumes of data • Four different QoS levels • Fast reservation to begin transmission of packets, typically 0.5 to 1.0 sec School of Information Technologies GPRS-6
  4. 4. GPRS MSs • Three classes of MS • Class A MS can operate GPRS and other GSM services simultaneously • Class B MS can monitor control channels for GPRS and other GSM services simultaneously, but can operate only one set of services at a time • Class C MS can operate GPRS services only School of Information Technologies GPRS-7 GPRS Architecture (GSM view) VLR BTS BSC MSC PSTN HLR GSM SGSN GGSN Internet GTP GPRS GGSN: Gateway GPRS Support Node SGSN: Service GPRS Support Node GTP: GPRS Tunneling Protocol School of Information Technologies GPRS-8
  5. 5. GPSR Architecture (data view) SGSN Gn BSS SGSN GGSN PDN MS Um Gb Gn Gi MSC HLR/ GR VLR EIR School of Information Technologies GPRS-9 Serving GPRS Support Node (SGSN) • at same hierarchical level as MSC • delivers packets to MS within its service area • queries HLRs for profile data of GPRS subscribers • detects new GPRS mobile stations in a given service area • processes registration of new MSs and keeps a record of their location School of Information Technologies GPRS-10
  6. 6. Gateway GPRS Support Node (GGSN) • used as interface to external packet-switched networks • connected to SGSN via an IP-based GPRS backbone network • maintains routing information that is necessary to tunnel the Protocol Data Units (PDUs) to the SGSNs that service particular mobile stations • one or more GGSNs may support multiple SGSNs School of Information Technologies GPRS-11 GPRS Network Enhancements • Base Station System (BSS): – must be enhanced to recognize and send user data to the SGSN that is serving the area • Home Location Register (HLR): – must be enhanced to register GPRS user profiles and respond to queries originating from SGSNs regarding these profiles • MSC/VLR: – optionally enhanced to coordinate GPRS and non-GPRS – e.g. combined location updates, SGSN paging for GSM calls School of Information Technologies GPRS-12
  7. 7. GPRS Network Operations • For GPRS user, network is connectionless • HOWEVER, a network connection must be established for each transaction, and released once the transaction is completed School of Information Technologies GPRS-13 Network Access • GPRS attach request from MS to begin a transaction • GPRS detach request from MS to end a transaction • Attach/detach requests are infrequent e.g. daily • Location updates much more frequently School of Information Technologies GPRS-14
  8. 8. Network Access... User Registration associates the MS ID with the user address In home area, HLR is enhanced to reference GPRS data Outside home area, dynamically allocated records are references in VLRs Authentication - via GSM mobility management protocols Call Admission Control determines n/w resources for QoS School of Information Technologies GPRS-15 Routing and Data Transfer • Routing is performed by the GSNs on a hop-by-hop basis, using the destination address • Routing tables are maintained by the GSNs using the GTP layer • Data may be – Forwarded – Tunneled – Compressed – Encrypted School of Information Technologies GPRS-16
  9. 9. Mobility Management • Mobility Management used to track the MS • SGSNs communicate to update the user location • Logical link is established between the MS and the SGSN School of Information Technologies GPRS-17 GPRS Protocol Architecture MS Um BSS Gb SGSN Gn GGSN Gi apps. IP/X.25 IP/X.25 SNDCP GTP SNDCP GTP LLC LLC UDP/TCP UDP/TCP RLC BSSGP IP IP RLC BSSGP MAC MAC FR FR L1/L2 L1/L2 radio radio From http://www.trillium.com/whats-new/wp_gprs.html School of Information Technologies GPRS-18
  10. 10. GPRS Network Protocols • Sub-Network Dependent Convergence Protocol (SNDCP): – maps a network-level protocol, such as IP or X.25, to the underlying logical link control. – provides 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. School of Information Technologies GPRS-19 GPRS Network Protocols... • 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): – tunnels the protocol data units through the IP backbone by adding routing information. – GTP operates on top of TCP/UDP over IP School of Information Technologies GPRS-20
  11. 11. GPRS Network Protocols... • GPRS Mobility Management (GMM): – handles mobility issues such as roaming, authentication, and selection of encryption algorithms. • Network Service: – 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. School of Information Technologies GPRS-21 GPRS Network Protocols... • 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 School of Information Technologies GPRS-22
  12. 12. EDGE (Enhanced Data rate for GSM Evolution) • Uses GSM/GPRS, but with higher-level modulation (8-PSK instead of GMSK) • Choice of 9 modulation schemes • Allows up to 48 kbps per timeslot, 384 kbps using 8 time slots School of Information Technologies GPRS-23 References Christian Bettstetter, Hans-Jörg Vögel, and Jörg Eberspächer , GSM Phase 2+ General Packet Radio Service GPRS: Architecture, Protocols and Air Interface, IEEE Communications Surveys http://www.comsoc.org/pubs/surveys, Third Quarter 1999, vol. 2 no. 3 A. K. Salkintzis, A survey of Mobile Data Networks, IEEE Communications Surveys http://www.comsoc.org/pubs/surveys, Third Quarter 1999, vol. 2 no. 3 Trillium Digital Systems, Generalised Packet Radio Service (GPRS) White Paper, http://www.trillium.com/whats-new/wp_gprs.html Hannu H. Kari , General Packet Radio Service (GPRS), http://www.ee.oulu.fi/~fiat/gprs.html Hannu H. Kari , GPRS overview and links, http://www.cs.hut.fi/~hhk/GPRS/gprs_index.html GPRS links: http://www.topology.org/gprs.html EDGE: http://www.dataonsms.com/edge.htm School of Information Technologies GPRS-24

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