General packet radio services (GPRS) is step to efficiently transport high-speed data over the current GSM and TDMA-based wireless network infrastructures. Deployment of GPRS networks allows a variety of new applications ranging from mobile e-commerce to mobile corporate VPN access Deployments of GPRS network has already taken place in several countries in Europe and the far east.

1. SHREE SWAMI ATMANAND SARASWATI INSTITUTE
OF TECHNOLOGY
Mobile Computing & Wireless Communication (2170710)
PREPARED BY: (Group:1)
Bhumi Aghera(130760107001)
Monika Dudhat(130760107007)
Radhika Talaviya(130760107029)
Rajvi Vaghasiya(130760107031)
General Packet Radio Service(GPRS)
GUIDED BY:
Prof. Drashti Chauhan

2. GPRS and Packet Data Network
• General packet radio services (GPRS) is step to efficiently transport high-speed data over the
current GSM and TDMA-based wireless network infrastructures.
• Deployment of GPRS networks allows a variety of new applications ranging from mobile e-
commerce to mobile corporate VPN access
• Deployments of GPRS network has already taken place in several countries in Europe and
the far east.

3. Capacity and Other End-user Aspects
• GPRS has the ability to offer data speed of 14.4 kbps to 171.2 kbps which allow for
comfortable internet access.
• It allows for short “bursty” traffic, such as e-mail and web browsing, as well as large volumes
of data.
• For GPRS no dial-up modem connection is necessary.
• It offers fast connection set-up mechanism to offer a perception of being “always on”. This is
why GPRS users are referred to as being “always connected”.
• Immediacy is one of the advantages of GPRS compared to circuit switched data.

4. Quality of Services (QoS)
• The Quality of Service (QoS) requirements of typical mobile packet data applications are
very diverse.
• GPRS allows definition of QoS profiles using the parameters of service precedence,
reliability, delay and throughput.
• Service precedence is the priority of a service in relation to another service. There exist three
levels of priority: high, normal or low.
• Reliability indicates the transmission characteristics required by an application. Three
reliability classes are defined, which guarantee certain maximum values for the probability of
loss, duplication, mis-sequencing and corruption of packets.
• Delay parameters define maximum values for the mean delay and the 95-percentile delay.
• Throughput specifies the maximum/peak bit rate and the mean bit rate.

5. Integral Part of the Future 3G Systems
• The different approaches to third generation (3G) wireless system were intended to address
the challenge of voice-to-data crossover and integration.
• The complexities of new and exciting wireless technologies have solved down progress in
their development and widespread deployment.
• To lessen the impact of the delay in implementing 3G wireless system, GPRS was introduced
as an intermediate step to efficiently transport high speed data over the current GSM and
TDMA based wireless network infrastructures.
• GPRS is therefore called the 2.5G in the evolution process of wireless cellular networks.

6. GPRS network architecture
• GPRS uses the GSM architecture for voice.
• In order to offer packet data services through GPRS, a new class of network nodes need to be
introduced as an upgrade to the existing GSM network. These network nodes are called
GPRS support nodes (GSN).
• GPRS support nodes are responsible for the delivery and routing of data packets between the
mobile stations and the external packet data networks (PDN).
• There are two types of support nodes:
i. SGSN (Serving GSN)
ii. GGSN (Gateway GSN)

7. Serving GPRS Support Node (SGSN)
• A serving GPRS support node (SGSN) is at the same hierarchical level as the MSC.
• Whatever functions MSC does for voice, SGSN does the same for packet data.
• SGSN’s tasks include packet switching, routing and transfer, mobility management, logical
link management, authentication and charging functions.
• SGSN processes registration of new mobile subscribers and keeps a record of their location
inside a given service area.
• The location register of the SGSN stores location information and user profiles of all GPRS
users registered with this SGSN.
• SGSN sends queries to Home Location Register (HLR) to obtain profile data of GPRS
subscribers.
• The SGSN is connected to the base station system with Frame Relay.

8. Gateway GPRS Support Node (GGSN)
• GGSN acts as an interface between the GPRS backbone network and the external packet
data networks.
• GGSN’s function is similar to that of a router in a LAN.
• It converts the GPRS packets coming from the SSGN into the appropriate packet data
protocol (PDP) format for the data networks like Internet or X.25.
• PDP sends these packets out on the corresponding packet data network.
• In the other direction, PDP receives incoming data packets from data networks and converts
them to the GSM address of the destination user.
• The readdressed packets are sent to the responsible SGSN.
• For this purpose, the GGSN stores the current SGSN address of the user and his or her
profile in its location register.
• The GGSN also performs authentication and charging functions related to data transfer.

10. • GSM network elements are as follows:
• Base Station System (BSS): BSS system needs enhancement to recognize and send
packet data. This includes BTS upgrade to allow transportation of user data to the SGSN.
Also, the BTS needs to be upgraded to support packet data transportation between the
BTS and the MS over the radio.
• Home Location Register (HLR): HLR needs enhancement to register GPRS user
profiles and respond to queries originating from GSNs regarding these profiles.
• Mobile Station (MS): The mobile station or the mobile phone for GPRS is different from
that of GSM.
• SMS Nodes: SMS-GMSCs and SMS-IWMSCs are upgraded to support SMS
transmission via the SGSN. Optionally, the MSC/VLR can be enhanced for more
efficient coordination of GPRS and non-GPRS services and functionality.

11. Transmission Plane Protocol Architecture
• The transmission plane consists of a layered protocol structure providing user data transfer,
along with associated procedures that control the information transfer such as flow control,
error detection, and error correction.

12. Air Interface
• The air interface is located between the MS and the BSS. The protocols used on the air
interface are as follows:
• Radio link control/medium access control (RLC/MAC).
• RLC provides a reliable radio link between the mobile and the BSS.
• MAC controls the access signaling procedures to the GPRS radio channel, and the
multiplexing of signaling and RLC blocks from different users onto the GSM physical
channel.
• GSM-RF layer. It is the radio subsystem that supports a certain number of logical channels.
• This layer is split into two sublayers:
1. Radio frequency layer (RFL), which handles the radio and baseband part (physical
channel management, modulation, demodulation, and transmission and reception of
radio blocks).
2. Physical link layer(PLL), which manages control of the RFL (power control,
synchronization, measurements, and channel coding/decoding).

13. Gb Interface
• The Gb interface is located between the SGSN and the BSS. It supports data transfer in the
transmission plane.
• The Gb interface supports the following protocols:
 BSS GPRS protocol (BSSGP). This layer conveys routing and QoS-related information
between the BSS and SGSN.
 Network service (NS). It transports BSSGP PDUs and is based on a frame relay
connection between the BSS and SGSN.
• A relay function is implemented in the SGSN to relay the packet data protocol (PDP) PDUs
between the Gb and Gn interfaces.

14. Gn/Gp Interface
• The Gn interface is located between two GSNs (SGSN or GGSN) within the same PLMN,
while the Gp interface is between two GSNs in different PLMNs.
• The Gn/Gp interface is used for the transfer of packets between the SGSN and the GGSN in
the transmission plane.
• The Gn/Gp interface supports the following protocols:
 GPRS tunnelling protocol (GTP). This protocol tunnels user data between the SGSN and
GGSN in the GPRS backbone network. GTP operates on top of UDP over IP. The layers
L1 and L2 of the Gn interfaces are not specified in the GSM/GPRS standard.
 User datagram protocol (UDP). It carries GTP packet data units (PDUs) in the GPRS
Core Network for protocols that do not need a reliable data link (e.g., IP).
 Internet protocol (IP). This is the protocol used for routing user data and control signaling
within the GPRS backbone network.

15. Interface Between MS and SGSN
• This interface supports the following protocols:
 Subnetwork-dependent convergence protocol (SNDCP). This protocol maps the IP
protocol to the underlying network. SNDCP also provides other functions such as
compression, segmentation, and multiplexing of network layer messages.
 Logical link control (LLC). This layer provides a highly reliable logical link that is
independent of the underlying radio interface protocols. LLC is also responsible for the
GPRS ciphering.

16. GPRS Network Operation
• Once a GPRS mobile station is powered on, it introduces itself to the network by sending a
“GPRS attach” request.
• Network access can be achieved from either the network side or MS side of the GPRS
network.
• GPRS perform the following operation:
1. Attachment and Detachment procedure
2. APN-Access Point Name
3. Mobility management
4. Routing
5. Communicating with the IP Network

17. Attachment and Detachment procedure
• This operation establishes a logical link between the MS and the SGSN.
• The network checks if the MS is authorized to use the services; if copies the user profile
from the HLR to the SGSN, and assigns a packet temporary mobile subscriber identity to the
MS.
• If the PDN is an IP network, it will request for an IP address; for a X.25 network it will ask
for a X.25 DTE address. This address is called PDP (packet data protocol) address.
• For each session, a PDP context is created.
• The allocation of the PDP address can be static or dynamic.
• In static address, the network operator permanently assigns a PDP address to the user.
• In dynamic address, a PDP address is assigned to the user upon activation of a PDP context.
• The PDP address can be assigned by the home network or by the visited network.
• In dynamic PDP address assignment, the GGSN is responsible for the allocation and the
activation/deactivation of the PDP addresses.This function is similar to the DHCP function.

18. PDP Context Activation

19. APN-Access Point Name
• GPRS/EDGE cellular data network use a mechanism called an Access Point Name (APN) to
determine hoe a MS, communicates via the GPRS network to a host site.
• A mobile device connects to a GPRS network by setting up a PDP context.
• An APN is chosen according to the settings in the mobile device and the SIM card.
• The chosen APN is used to query the network operation’s DNS server. This process gives
the IP address of a GGSN.
• An APN provides routing information for SGSN and GGSN and defines how users can
access the data network at that entry point, what IP addresses are assigned to the mobile
station, what security methods are used.
• APNs are general-purpose and are available to multiple customer or can be customized for
particular customers to address unique requirements.

20. • As a mobile station moves from one area to another, mobility management functions are used
to track its location.
• SGSNs communication with each other to update the MS’s location in the relevant registers.
• The mobile station’s profile are preserved in the VLRs that are accessible to SGSN via the
local MSC.
• A logical link is established and maintained between the mobile station and the SGS at each
PLMN.
• At the end of transmission or when a mobile station moves out of the area of a specific
SGSN, the logical link is released and the resources associated with it can be reallocated.
Mobility Management

21. • The important roles of GGSN involve synergy with the external data network. The GGSN
updates the location directory using routing information supplied by the SGSNs about the
location of an MS. It routes the external data network protocol packet encapsulated over the
GPRS backbone to the SGSN currently serving the MS. It also decapsulates and forwards
external data network packets to the appropriate data network and collects charging data that
is forwarded to a charging gateway (CG).
• There are three important routing schemes
1) Mobile-originated message - This path begins at the GPRS mobile device and ends at
the host.
2) Network-initiated message when the MS is in its home network - This path begins at
the host and ends at the GPRS mobile device.
3) Network-initiated message when the MS roams to another GPRS network - This
path begins at the host of visited network and ends at the GPRS mobile device.
Routing

22. Routing Example

23. • A GPRS network can be interconnected with Internet.
• GPRS supports both IPv4 and IPv6.
• In external IP network, the GPRS network look like any other IP sub-network, and the GGSN
look like a usual IP router.
• The IP address is taken from the address space of the GPRS operator maintained by a DHCP
server.
• The address resolution between IP address and GSM address is performed by the GGSN,
using the appropriate PDP context.
• A DNS managed by the GPRS operator.
• To protect the PLMN from unauthorized access, a firewall is installed between private GPRS
network and the external IP network.
• With this configuration, GPRS can be seen as a wireless extension of the Internet all the way
to a mobile station or mobile computer.
• The mobile user has direct connection to the Internet.
Communicating with the IP Network