GPRS Architecture Ayan Ganguly Bishakha Roy Akash Dutta

DISCUSSION TOPICS Introduction System Architecture GPRS Network Elements GPRS Logical Architecture GPRS Routing

INTRODUCTION GPRS (General Packet Radio Service) is an enhancement over the GSM and adds some nodes in the network to provide the packet switched services. These network nodes are called GSNs (GPRS Support Nodes) and are responsible for the routing and delivery of the data packets to and from the MS and external packet data networks (PDN).

INTRODUCTION contd. The GPRS network acts in parallel with the GSM network, providing packet switched connections to the external networks. The requirements of a GPRS network are the following: The GPRS network must use as much of the existing GSM infrastructure with the smallest number of modifications to it. The GPRS network architecture has to be compatible with future 3rd and 4th generation mobile communication systems. It should be able to support both point-to-point and point-to-multipoint data connections. It should provide secure access to external networks. To understand GPRS system architecture it is helpful to first understand the architecture of GSM system.

INTRODUCTION contd. GSM Architecture

GPRS System Architecture

GPRS System Architecture contd. GPRS Interfaces Gb– Connects BSC with SGSN Gn– SGSN – SGSN/GGSN (in the same network) Gp– SGSN –GGSN (in different networks) Gf– Connects EIR with SGSN for equipment querying at registering time Gi– Connects PLMN with external Packet Data Networks (PDNs) Gr– To exchange User profile between HLR & SGSN Gs– To exchange Database between SGSN & MSC Gd– Interface between SMS & GPRS Gc– Between GGSN and HLR

GPRS System Architecture contd. GPRS Subscriber Terminals Only GPRS terminals can access GPRS Servers. These terminals are backward compatible with GSM for voice calls. It cannot packetize data directly. It cannot handle the enhanced air interface.

GPRS System Architecture contd. GPRS BSS (Base Station Subsystem) A software upgrade is required in the existing Base Transceiver site. The Base Station Controller (BSC) also requires a software upgrade, and the installation of a new piece of hardware called a Packet Control Unit (PCU). The PCU directs the data traffic to the GPRS network. The PCU provides a logical and physical data interface out of BSS packet data traffic.

GPRS System Architecture contd. DATABASES All the databases involved in the network requires software upgrades to handle the new call models and functions introduced by GPRS. The Home Location Register (HLR) and Visitor Location Register especially requires upgrades to functionally service GPRS.

GPRS System Architecture contd. Home Location Registers (HLR) - contains administrative information of each subscriber - current location of the mobile Visitor Location Registers (VLR) - contains selected administrative information from the HLR -authenticates the user -tracks which customers have the phone on and ready to receive a call -periodically updates the database on which phones are turned on and ready to receive calls

GPRS Mobile Station Terminal for the use of GSM services. A Mobile Station (MS) comprises several functional groups  MT (Mobile Terminal):  offers common functions used by all services the MS offers.  Corresponds to the network termination (NT) of an ISDN access.  End point of the radio interface (Um)  TE (Terminal Equipment):  Peripheral device of the MS, offers services to a user.  Does not contain GSM specific functions.

GPRS Network Elements  SGSN – Serving GPRS Support Node Delivers data packets to mobile stations & vice-versa Detect and Register new GPRS MS in its serving area Packet Routing, Transfer & Mobility Management Authentication, Maintaining user profiles Its location register stores location info. & user profiles

GPRS Network Elements contd.  GGSN – Gateway GPRS Support Node Interfaces GPRS backbone network & external packet data networks (PDN). Converts the GPRS packets from SGSN to the PDP format Converts PDP addresses change to GSM addresses of the destination user Stores the current SGSN address and profile of the user in its location register Performs authentication

GPRS Logical Architecture

Data Routing A main issue I the GPRS network is the routing of data packets to and from a mobile user; which is divided into two part. Data Packet Routing. Mobility Management.

GPRS Routing

Data Packet Routing GPRS operator will allow roaming through an interoperate backbone network. GPRS operators connect to the interoperator network by a Border Gateway (BG). The GPRS network encapsulates all data network protocols into its own encapsulation protocol called GPRS Tunneling Protocol (GTP).

Different Backbone used in GPRS GSNs are connected through IP based backbone Two Backbones: Intra PLMN backbone networks that connects GSNs of the same PLMN & are private IP networks Inter PLMN backbone networks that connects GSNs of the different PLMN. Roaming agreement is necessary

Mobility Management

Mobility Management cont. SNDCP: This is used to transfer data packets between SGSN and MS. LLC: This layer assures transfer of user data across a wireless network. BSSGP: It delivers routing and QoS related information between BSS and SGSN. NETWORK SERVICE: Manages the convergence sub layer (BSSGP & Frame Relay). DATA LINK LAYER: It is divided into three sub layers- LLC, RLC and MAC. LLC: Responsible for sequence control, in-order delivery, flow control, detection of transmission errors. RLC: Establish a reliable link between the MS and the BSS. MAC: It controls the access attempts of an MS on the radio channel shared by several MSs. PHYSICAL LAYER: It is divided into PLL and RFL. PLL: Responsible for information transfer over a physical channel between the MS and the network. RFL: Performs modulation of the physical waveforms.

Mobility Management cont. The MM states specify the MM activities of an MS: The state is IDLE if the MS is not attached to the GPRS mobility management. In this state the MS does not have a logical GPRS context activated or any packet switched public data network (PSPDN) allocated. The MS can receive only those multicast messages that can be received by any GPRS MS. The state is STANDBY if the MS is attached to GPRS mobility management but has not obtained detailed location information. The state is READY or ACTIVE if the location information for the MS has been identified by SGSN. In this data is transmitted between the MS and GPRS network.

Applications of GPRS Web browsing Corporate & Internet Vehicle Positioning Remote LAN Access Home Automation Document Sharing/Collaborative working

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