3G Protocol Stack - V2 26-08

3G – Protocol ArchitectureArchitecture

Amal Chandran

© 2008 Nokia 3G Protocol Stack.ppt / 2009-08-26 / AC1

UMTS – Universal Mobile Telecom System

Inter-PLMN Backbone Network

3G-SGSN 3G-MSC

CS Domain3G-GGSN

PS Domain

Iu-CSIu-PS

Gs


Node B

RNC

UTRANIur

WCDMA

IubUu

GSM/WCDMA Network Architecture

3G/WCDMA

NAS

2G/GSM


SGSN – Serving GPRS Support NodeGGSN – Gateway GPRS Support NodeBSC – Base Station ControllerBTS – GSM Base Transceiver StationGERAN –GSM/EDGE Radio Access Network

MSC – Mobile Services Switching CentreGMSC – Gateway MSCHLR – Home Location RegisterRNC – Radio Network ControllerNode B – WCDMA Base StationUTRAN – UMTS Radio Access Network

Network Components

• Node – B (BTS) : Physical Layer Device

• RNC: Radio Network Controller

• Controls the Node-B’s

• MSC/GMSC: Mobile Switching Centre, Gateway MSC

• Circuit Switched Services• Circuit Switched Services

• VLR: Visitor Location Register

• Database of Active Users in the area

• HLR: Home Location Register

• Subscriber Information

• SGSN/GGSN: Serving GPRS Support Node, Gateway GSN

• Packet Switched Services


Protocol Stack – Review of Concepts

• Software Architecture for enabling Communication

• Each Layer has specific function

Layer 3 message


Layer 2 Header

L1 L1 L1

L1 = Layer 1 Header

101010101000010101000010101010111010110101010......

Spreading, Scrambling, Modulation…

Layer 1: The Physical Layer

• Connects Node-B to UE

• Cell Searching

• Spreading

• Scrambling

3G Network

• Scrambling

• Modulation

• Power Control

• Measurements

• Physical Channels of WCDMA


Layer 2: MAC

• Medium Access Control

• Provides Access to Layer 1.

• Priority Handling between the data flows of the UE

• Multiplexing of Logical Data (Logical Channels)• Multiplexing of Logical Data (Logical Channels)

• Traffic Volume Monitoring

• Identification of UE on common channels

• Ciphering of Voice Data


Layer 2: RLC

• Radio Link Control

• Segmentation and Re-Assembly of data

• In-sequence delivery

• Error detection and recovery• Error detection and recovery

• Flow control

• Ciphering of Control Data

• Three modes: Acknowledged, Unacknowledged, and Transparent


Layer 3: RRC – The Brain

• RRC : Radio Resource Control

• Management of Radio Resources

• Connection Management

• Setup, Maintenance, Release.

• Monitor the connection states

3G Network

• Monitor the connection states

• Transfer of control messages

• Called “Signalling Messages”

• Control of 3G measurements


Layer 3: Non Access Stratum

• Mobility Management

• Keeps track of Location Area

• Call Management

• Everything related to calls• Everything related to calls

• Session Management

• Data Connection management

• SMS Services


User Data

• PDCP

• Packet Data Convergence Protocol

• Header Compression

• BMC• BMC

• Broadcast and Multicast Control

• Broadcast of information – Like “Tsunami Warnings”,

“Traffic Alerts”


Powering up a mobile, in 3G

• Search for cells

• Find out the parameters of the cell from the information broadcast

• Identify the Network ID (PLMN ID) of the network

• Check the quality of the cell

• Cell is good? • Cell is good?

• Setup a connection

• Authenticate

• Update the network with UE’s location information

• Ready to go…


Incoming Call?

• Paging message

• UE’s ID is registered with the network now.

• Send out paging request to UE

• Identify the UE ID, and respond to the paging. • Identify the UE ID, and respond to the paging.

• Exchange call information –

• Codec to use, Quality (Data Rate) of the call etc.

• Setup the call

• Establish a dedicated connection


Change of Cells – Hand Over

• Current cell quality is low

• Move to another cell

• Simultaneous reception from two (or more) Node-Bs

• Soft Hand Over• Soft Hand Over

• Softer Handover


Soft/Softer handover

BTS 1

BTS 2

BTS 3

RNC 1

(SRNC)

RNC 2

(DRNC)

Call transferred �

Via SRNS relocation


Sector 1 Sector 2 Sector 3 Sector 4 Sector 5 Sector 6

Add Sector 2 : Softer Handover

Add Sector 3 : Soft Handover, same RNC

Add Sector 4, remove Sector 1

Add Sector 5, remove Sector 2

Add sector 6,

Remove sector 4,

Triggers SRNS relocation

remove Sector 3

Setup call

Overall Architecture

L3Non Access Stratum

User Data

CMSMS MM

SNDCP

SM

TCP/IP Data – User Data


L3

WCDMA

WCDMA MAC

WCDMA L1

RRC

WCDMA RLC

PDCP

GSM/GPRS

L1

L2

RR

GSM L2

GPRS MAC

GPRS LLC

GPRS RLC

GSM L1

Interested in Reading Further?

• Web:

• http://www.3gpp.org/

• Look for Specification number 25.301

• http://www.etsi.org/

• Print Media

• WCDMA For UMTS : Antti Toskala, Harri Holma


Q & A ?

THANK YOU ☺☺☺☺

Q & A ?discussion.forum.nokia.com/vtuedusat

WCDMA_L1.ppt / 25-Aug-2009/ UDN18

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3G Protocol Stack - V2 26-08

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