3G Protocol Stack - V2 26-08

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3G – Protocol

Architecture

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UMTS – Universal Mobile Telecom System

Inter-PLMN Backbone Network 3G-SGSN _3G-MSC CS Domain 3G-GGSN PS Domain Iu-CS Iu-PS Gs Node B RNC UTRAN Iur WCDMA Iub Uu

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GSM/WCDMA Network Architecture

3G/WCDMA NAS

2G/GSM

SGSN – Serving GPRS Support Node GGSN – Gateway GPRS Support Node MSC – Mobile Services Switching Centre

GMSC – Gateway MSC

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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

• VLR: Visitor Location Register

• Database of Active Users in the area

• HLR: Home Location Register

• Subscriber Information

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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…

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Layer 1: The Physical Layer

• Connects Node-B to UE • Cell Searching • Spreading • Scrambling 3G Network • Scrambling • Modulation • Power Control • Measurements

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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)

• Traffic Volume Monitoring

• Identification of UE on common channels

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Layer 2: RLC

• Radio Link Control

• Segmentation and Re-Assembly of data

• In-sequence delivery

• Error detection and recovery

• Flow control

• Ciphering of Control Data

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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”

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Layer 3: Non Access Stratum

• Mobility Management

• Keeps track of Location Area

• Call Management

• Everything related to calls

• Session Management

• Data Connection management

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User Data

• PDCP

• Packet Data Convergence Protocol

• Header Compression

• BMC

• Broadcast and Multicast Control

• Broadcast of information – Like “Tsunami Warnings”,

“Traffic Alerts”

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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?

• Setup a connection

• Authenticate

• Update the network with UE’s location information

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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.

• Exchange call information –

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

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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

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Soft/Softer handover

BTS 1 BTS 2 BTS 3 RNC 1 (SRNC ) RNC 2 (DRN C) Call transferred Via SRNS relocation

Sector 1 _{Sector 2} _{Sector 3} _{Sector 4} Sector 5 _{Sector 6}

Add Sector 2 :

Softer Add Sector 3 : _{Soft Handover,}Add Sector 4, _{remove Sector}Add Sector 5, _{remove Sector} Add sector 6, Remove sector remove Sector 3 Setup call

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Overall Architecture

L3

Non Access Stratum

User Data CM

SMS 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

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Interested in Reading Further?

• Web:

• http://www.3gpp.org/

• Look for Specification number 25.301

• http://www.etsi.org/

• Print Media

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Q & A ?

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