GPRS

1
GPRS

• Adapted from www.mobinet.gr
• Also see
• http//en.wikipedia.org/wiki/GPRS

2
What is GPRS?

• GPRS
• stands for General Packet Radio Service
• is the major GSM Phase 2 enhancement and an
  important step to 3G
• aims at providing data services to mobile users
  with high bandwidth efficiency and always on
  connectivity

3
Why introducing GPRS?

• The percentage of people accessing the Internet
  as part of their every day activities has known
  an explosive growth during the last decade
• This fact combined with the impressive
  penetration of mobile telephony in the last few
  years, has triggered a global interest towards
  mobile access to IP-based applications (e.g.
  e-commerce) and services
• GSM could not support data services with traffic
  patterns similar to those that exhibit Internet
  applications (bursty characteristics)

4
Shortcomings of GSM

• Users point of view
• Data rates are too slow up to 9.6 kbps
• Connection setup takes too long
• The service is too expensive
• for end users
• Technical point of view
• GSM deploys circuit-switched mechanisms, which
• are inappropriate for the bursty characteristics
  of Internet traffic
• impose a time-oriented charging scheme

5
GPRS Characteristics

• GPRS
• supports high data rates
• up to 172 kbps
• offers fast call setup times
• provides always on
• connectivity
• supports QoS aware
• mechanisms
• integrates IP infrastructure into the GSM network
• deploys packet-switched mechanisms, which
• allow for a volume-based charging discipline
• result in more efficient resource utilization
  when bursty traffic is concerned

6
User s view of GPRS

7
Coding Schemes

• Channel coding is used in every digital
  communication system to
• increase channel capacity
• protect against errors
• GPRS makes use of 4 different coding schemes,
  depending on channel conditions

• When 8 slots are used, the maximum data rate of
  171.2 kbit/s is achieved

8
What Calls for QoS Support?

• Technical point of view
• Applications have inherent requirements in terms
  of delay, delay variation of packet
  transmissions, packet loss and throughput

• Users point of view
• Different users perceive different Quality when
  offered the same service

9
QoS Support

• GPRS-Release 97/98 allowed the definition of
  different QoS profiles by determining four
  parameters
• Service precedence is the priority of a service
  in relation to another service
• Reliability guarantees certain maximum values
  for different metrics

• Delay defines defines maximum values for the
  mean delay and the 95-percentile delay
• The throughput specifies the maximum/peak bit
  rate and the mean bit rate

10
QoS Support

• GPRS-Release 99 specified four distinct traffic
  classes

11
GPRS Network Architecture (1/3)
12
GPRS Network Architecture (2/3)

• GSN GPRS support nodes
• Delivery and routing of data packets between MS
  and external PDN (packet data network)
• The Serving GPRS Support Node (SGSN) is
  responsible for
• Admission control
• Routing, mobility management, location
  management, authentication, charging
• Receiving and delivering data packets
• Address translation and mapping
• Encapsulation

13
GPRS Network Architecture (3/3)

• The Gateway GPRS Support Node (GGSN)
• acts as interface between GPRS backbone and
  external Packet Data Networks (PDN) or other
  Public Mobile Land Networks
• converts GPRS packets coming from SGSN into the
  appropriate packet data protocol (PDP) format
  (e.g. IP or X.25)
• converts the PDP addresses of incoming data
  packets to the GSM address of the destination
  user, and sends the readdressed packet sto the
  responsible SGSN

14
Two Routing Scenarios

• Scenario 1 A GPRS mobile station located in PLMN
  1 sends packets to a host connected to the IP
  network

• The SGSN that the MS is registered with
  encapsulates the IP packets, examines the PDP
  context, and routes them through the intra-PLMN
  GPRS backbone to the appropriate GGSN

• The GGSN decapsulates the packets and sends them
  out on the IP network

• IP routing mechanisms are used to transfer the
  packets to the access router of the destination
  network. The latter delivers the IP packets to
  the host

• Scenario 2 Assume the home-PLMN of the MS is
  PLMN2. The host is now sending IP packets to the
  MS, which are sent out onto the IP network and
  are routed to the GGSN of PLMN2

• The GGSN of PLMN2 queries the HLR and obtains the
  current location of the MS (PLMN1). It
  encapsulates the incoming IP packets and tunnels
  them to the appropriate SGSN in PLMN1

• The SGSN decapsulates the packets and delivers
  them to the MS

15
Simultaneous Use of Circuit Packet Switched
Services

• Class A
• Simultaneous operation of GPRS and conventional
  GSM services are possible
• Class B
• A mobile station can register for both GPRS and
  conventional GSM services, but can only use one
  of the 2 services at a given time
• Class C
• A mobile station can attach for either GPRS or
  GSM services (exception SMS)

16
GPRS Services

• GPRS provides two types of services
• PTP (Point-to-Point) service
• PTP-CLNS (connectionless mode, e.g. IP)
• PTP-CONS (connection-oriented mode, e.g. X.25)
• PTM (Point-to-Multipoint) service
• PTM-M (multicast service)
• PTM-G (group call service)

17
GPRS Applications

• Information services as text or graphics
• m-commerce - not all content is delivered via
  the mobile network
• vending machine, juke box, car wash, and road
  toll services
• web shopping
• tickets for transport (eg trains)
• gaming and gambling
• banking
• Location Based Services
• Corporate email, Internet email
• LAN applications
• Mobile Office
• Web browsing
• File transfer

18
2.5G prepares the market for 3G

• GPRS consolidates global success of GSM
• 6.4 million GPRS users worldwide by end 2002
• Approximately 150 GPRS networks operational in 58
  countries
• More than 50 million GPRS terminal devices
  delivered worldwide