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GPRS
GPRS
GPRS
GPRS
GPRS
GPRS
GPRS
GPRS
GPRS
GPRS
GPRS
GPRS
GPRS
GPRS
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GPRS

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  • 1. Overview General Packet Radio System (GPRS)
  • 2. Introduction <ul><li>General Packet Radio Service (GRPS) today </li></ul><ul><ul><li>“ Packet overlay” network on top of the existing GSM (Digital) circuit switched voice-based network </li></ul></ul><ul><ul><li>TCP/IP-based: allows data packets to be conveyed across the mobile network using packet switching </li></ul></ul><ul><ul><li>“ Always on” / “always connected” </li></ul></ul><ul><ul><ul><li>After initial “log-on”, user is permanently connected to IP services </li></ul></ul></ul><ul><ul><ul><ul><li>Instant access, no further log-on </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Flat rate (about $30/mo in the LA area) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>User perceived performance: fluctuates (as GPRS users defer to voice users) to a max of 50Kbps </li></ul></ul></ul></ul><ul><ul><ul><li>Network resources only used when information ready to be exchanged – bandwidth on demand … </li></ul></ul></ul><ul><ul><ul><ul><li>More efficient utilization of air-time </li></ul></ul></ul></ul>
  • 3. GSM - GPRS <ul><li>Provides high speed packet data access </li></ul><ul><li>uses modified GSM hardware (different phones/cards) </li></ul><ul><li>Several time slots can be (dynamically) allocated to transmit a block of data </li></ul>
  • 4. GSM/GPRS Architecture, simplified
  • 5. Uplink/downlink <ul><li>The uplink channel is shared by a number of mobiles, and its use is allocated by a BSC (Base Station Controller) </li></ul><ul><ul><li>The MS (Mobile Station) requests use of the channel in a “packet random access message”. </li></ul></ul><ul><ul><li>The BSC allocates an unused channel to the mobile and sends a “packet access grant message” in reply </li></ul></ul><ul><li>The downlink is fully controlled by the serving BSC and random access is not needed </li></ul>
  • 6. GPRS Mobility Tunnelling
  • 7. Supporting Nodes – main functions
  • 8. GPRS/GSM Protocols - Overview
  • 9. Routing in GPRS
  • 10. Mobile Address Allocation <ul><li>GGSN Address Pools </li></ul><ul><ul><li>Static, dynamic allocation at GPRS packet data activation </li></ul></ul><ul><li>HLR </li></ul><ul><ul><li>The HLR may keep a static IP address that is fetched by the SGSN at GPRS attach </li></ul></ul><ul><li>RADIUS </li></ul><ul><ul><li>The GGSN may interact with an external AAA server in order to perform AAA functions as well as dynamic IP address allocation at GPRS packet data activation </li></ul></ul><ul><li>DHCP server </li></ul><ul><ul><li>The GGSN may interact with an external DHCP server to perform dynamic IP address allocation at GPRS packet data activation </li></ul></ul><ul><li>IPv6 auto configuration </li></ul>
  • 11. GPRS initial State
  • 12. GPRS Attach <ul><li>When a MS is turned on, the first function it performs is a GPRS attach </li></ul><ul><ul><li>GSM access authentication (towards Home Network, HLR (Authentication Center)) </li></ul></ul><ul><ul><li>User profile is downloaded from HLR to the serving SGSN </li></ul></ul><ul><li>When the GPRS attach is complete, the MS is physically connected to the visited network </li></ul>
  • 13. The Packet Data Protocol (PDP) Context <ul><li>In order to be able to send and receive data, the mobile must set-up a packet data bearer </li></ul><ul><ul><li>The PDP bearer is associated with contexts in each nodes that data are traversing </li></ul></ul><ul><li>The bearer is set-up via “PDP context activation” procedures </li></ul><ul><li>PDP context describes requirements of the connection to the packet networks: Type, network address, Access Point Name (APN), QoS, etc. </li></ul><ul><ul><li>SGSN validates request against subscription information downloaded from HLR during GPRS Attach </li></ul></ul><ul><ul><li>Access point name sent to DNS, IP address(s) of suitable GGSNs returned </li></ul></ul><ul><ul><li>Logical connection using GPRS tunnels (GTP) between SGSN and GGSN </li></ul></ul><ul><ul><li>IP address allocated (GGSN pool, DHCP, RADIUS) </li></ul></ul>
  • 14. PDP Context Activation

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