2.

5 G Cellular Systems and Architecture

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 2.5G Cellular System

• Introduction to GPRS and EDGE

• 2.5G System Architecture

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Evolution of Wireless

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 GPRS
• General Packet Radio Service
• Value added service to 2G to connect users
to IP (Internet Protocol) -based data
networks
• Forms basis of Packet Switched Network
• Data rate up to 115 Kbps with GPRS and
384 Kbps with EDGE

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 Motivation for GPRS
• Wireless access to internet and intranet

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 Circuit and Packet Switching
• Circuit Switching
o Dedicated resources to each user
o Higher performance and higher cost
• Packet Switching
o Shares resources with multiple users
o Lower performance and lower cost
o Requires MAC (Medium Access Control)
o Requires memory buffering
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Circuit Switching Network

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Packet Switching Network

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 EDGE
• Enhanced Data rate for Global Evolution

• Also called as Enhanced GPRS or EGPRS

• Improves efficiency of GPRS by use of

advanced modulation technique- Octal PSK
or 8 PSK Modulation
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GPRS Network

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GPRS Network Terms

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 Major functions of SGSN
• Provides Packet Switching and routing for
GPRS services- analogous to MSC in 2G
• Contains a database of subscribers,
including visitors (roamers) and home
subscribers- analogous to VLR in 2G
• Handles authentication and admission
control – analogous to MSC/HLR/AuC

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 Major functions of GGSN
• Provides Packet Switching and Routing for
GPRS services
• Provides interface to external Public Data
Networks (PDNs) e.g. the Internet
• First point of contact for packet session
originating outside the PLMN

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 Major functions of GERAN
• Handles admission control

• Handles radio resource management

• Performs packet relay and routing functions

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Elements of Communication System

Transmission Destination/
Source Transmitter Receiver
Channel Transdcers

Noise,
interference
and distortion

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 Typical Wireless Terminal

Analog-Digital
User Digital Interface
RF Front-end
Interface Baseband (Analog
Baseband)

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 Typical 2.5G Wireless Terminal
VCXO_ON
I2C PMIC

Vcc Synth
Vcc RX
Vcc TX
JTAG

Aux Pins

ABB
Audio I/F

Vcc
Baseband

Vcc ABB

Vcc RX
VCTCXO
Manitoba

Vcc TX
Vcc Synth
Vcc
Vcc
Port Rx Data
AFE
Aux. RX

Port GPRS Tx Data Vcc Synth

Voiceband mixed 13MHz

Port signal VCTCXO
Synthesizer
SPI RF Filter
solution Control

Control Vcc
GSM/GPRS
VCTCXO

GSM/ RF solution Vcc TX

T/R Switch
GPRS 13MHz MAIN
VCO SPI
Digital SPI Control
Baseband Control

RFCLK
Control
(13MHz) TX TX VCO
Control LPF
Vcc TX
Band Vcc TX

PA
Vcc
Manitoba

Ramp Control
Ramp Control
PA Control
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