GPRS Core Network Architecture and Implementation

The GPRS core network architecture is a complex system, but it's built around three main components: the Serving GPRS Support Node (SGSN), the Gateway GPRS Support Node (GGSN), and the Home Location Register (HLR).

The SGSN is responsible for managing the GPRS connection between the mobile device and the core network.

It acts as an interface between the mobile device and the GGSN, ensuring that data is routed correctly.

In terms of implementation, the SGSN uses a protocol called GTP (GPRS Tunneling Protocol) to establish and manage the GPRS connection.

The GGSN is the entry point for GPRS traffic from the mobile network to the external packet data network.

It's responsible for routing GPRS traffic to the correct destination on the internet.

The GGSN also performs functions such as packet screening, charging, and accounting.

The HLR is a database that stores information about the mobile subscriber, including their subscription details and location.

It's used by the SGSN to determine the subscriber's location and to authenticate the subscriber's identity.

The GPRS core network architecture relies on these three components working together seamlessly to provide a reliable and efficient service.

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The GPRS Core Network Architecture is made up of several key components, including the SGSN, GGSN, and PCU. These entities work together to provide the necessary support for packet data services.

The SGSN, or Serving GPRS Support Node, forms a gateway to the services within the network. It's essentially the bridge between the GPRS network and the rest of the GSM network.

The GGSN, or Gateway GPRS Support Node, forms the gateway to the outside world. This is where data is sent out to the internet or other external networks.

The PCU, or Packet Control Unit, detects whether data is to be routed to the packet switched or circuit switched networks. This is a critical function that ensures data is delivered to the right destination.

Here are the main network architecture entities needed for GPRS:

These entities work together to provide the necessary support for packet data services, including mobility management, session management, and transport for internet packets.

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The SGSN (Serving GPRS Support Node) plays a crucial role in the GPRS core network, handling various tasks such as packet routing and transfer, mobility management, and authentication.

It's the node that carries out the same function as the Local Agent in Mobile IP, but with added complexity due to its interworking with the connected radio network.

The SGSN has a location register that stores location information, such as the current cell and VLR, as well as user profiles, including IMSI and packet addresses used.

This information is crucial for mobility management, allowing the SGSN to keep track of users as they move between cells.

Here are some key SGSN functions:

In UMTS networks, the SGSN has additional functions, including carrying up to about 300 kbit/s traffic per subscriber and tunneling/detunneling downlink/uplink packets toward the RNC.

The GGSN, or Gateway GPRS Support Node, is a crucial entity in the GPRS network architecture. It's responsible for interworking between the GPRS network and external packet-switched networks, such as the Internet and X.25 networks.

The GGSN acts as a combination of a gateway, router, and firewall, hiding the internal network from the outside. This means it checks if a user is active before forwarding data to them, and it routes packet data from the mobile to the right destination network.

In operation, the GGSN receives data addressed to a specific user, checks if the user is active, and then forwards the data. This ensures that only authorized users receive the intended data.

Here are some key functions of the GGSN:

The PCU, or Packet Control Unit, is a hardware router that's added to the BSC. It's responsible for differentiating data destined for the standard GSM network and data destined for the GPRS network.

The PCU itself may be a separate physical entity, but more often it's incorporated into the base station controller, BSC, which saves additional hardware costs.

Network upgrades are a crucial aspect of implementing a GPRS core network. They allow network operators to add packet data capabilities to their existing GSM networks without having to start from scratch.

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The GPRS network architecture adds new elements to the existing network, including the SGSN, GGSN, and PCU. These entities form the gateway to services within the network, the gateway to the outside world, and detect whether data is to be routed to the packet switched or circuit switched networks.

The cost of these upgrades is a significant consideration for network operators. They endeavour to avoid the high capital expenditure (capex) costs associated with buying and establishing a new network.

The main new entities required within the network are the SGSN and GGSN. These entities are required as the starting point for the GPRS network.

The base station subsystems require some updates, including the addition of the PCU. This can often be achieved with a software upgrade, which may be done remotely.

Here are the main new entities required within the GPRS network:

The GPRS network architecture can be viewed as an evolution of the GSM network, carrying both circuit switched and packet data. This makes it an attractive option for network operators looking to upgrade their existing networks.

In a GPRS core network, interfaces play a crucial role in connecting different systems and allowing data to flow between them.

The GPRS network has several interfaces, including the air interface between the Mobile Station (MS) and the Base Station Controller (BSC), which uses the BSSAP protocol.

The BSSAP protocol handles tasks such as Handover, Authentication, Authorization, and Location Update.

The Gb interface is a Frame Relay interface between the Base Station Subsystem and the Serving GPRS Support Node (SGSN).

The Gn interface is an IP-based interface between SGSN and other SGSNs and internal GGSNs, using the GTP Protocol.

The Gp interface is also IP-based, connecting internal SGSN to external GGSNs, and uses the GTP Protocol with a Border Gateway acting as a firewall.

The Ga interface serves CDRs (Accounting records) from the SGSN to the Charging Gateway, using the GTP Protocol with extensions for CDRs.

The Gr interface connects the SGSN to the Home Location Register (HLR), using the MAP3 Protocol.

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The Gd interface connects the SGSN to the SMS Gateway, which can use MAP1, MAP2, or MAP3.

The Gs interface connects the SGSN to the Mobile Switching Center (MSC) and uses the BSSAP+ Protocol for tasks such as paging and station availability.

The Gi interface connects the network to external networks like the Internet or WAP.

Here's a summary of the main interfaces in a GPRS network:

In a GPRS core network, Support Nodes (SN) play a crucial role in enabling data communication. A GSN is a network node that supports the use of GPRS in the GSM core network.

GSNs come in two key variants: the GGSN and the SGSN. The GGSN is the node that carries out the role in GPRS equivalent to the Home Agent in Mobile IP. It's a router that detunnels user data from GPRS Tunnel Protocol and sends out normal user data IP packets.

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The GGSN performs several key functions, including detunneling GTP packets from the GGSN (downlink), tunneling IP packets toward the GGSN (uplink), and carrying out mobility management as Idle mode mobile moves from Routing Area to Routing Area.

The SGSN, on the other hand, is the node that carries out the same function as the Local Agent in Mobile IP. However, it's actually considerably more complex since it also does the full set of interworking with the connected radio network.

Here are the key functions of the GGSN and SGSN:

SGSN:

The GPRS core network is built on a robust set of specifications that ensure high availability and quality. This includes support for SIGTRAN, SCTP with CRC checksum, and ITU MTP, SCCP, TCAP protocols.

The network's architecture is designed to meet the strict GSM-R requirements for high availability, redundancy, and quality. This is achieved through the implementation of SGSN and GGSN nodes that provide a reliable career-grade solution.

Here are some key specifications of the GPRS core network:

The network's operating system is based on Linux, which provides a stable and secure foundation for the GPRS core network.

The specifications of this system are quite impressive. They support SIGTRAN, SCTP with CRC checksum, and various other protocols like M2UA, M3UA, and ITU MTP.

The system also supports E.212 (ANSI) and E.214 (ITU) translation tables, as well as E.164. This ensures compatibility with different networks and standards.

SGSN/MME support is also built-in, with features like ETSCI MAP v3 and S1AP r11.

Here's a breakdown of the supported standards and protocols:

This system is designed to be flexible and customizable, with features like automatic file rotation and customizable table headers.

The team's solution was a reliable career-grade system, designed to meet the strict GSM-R requirements for high availability, redundancy, quality, data rate, and packet loss. This system was compliant with the 3GPP specifications and the customer's needs.

To achieve this, the team implemented a set of protocols and signaling procedures for network interfaces. These protocols and procedures were specifically designed to satisfy the 3GPP specifications.

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Over a period of 5 years, the engineers implemented several major functions. These functions included GPRS Core compliance with 3GPP V11, high availability and local/geo redundancy, applications self-healing, overload protection, and OAM for GPRS Core nodes management.

Here's a breakdown of the major functions implemented: