Radio Interface Procedures

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Agenda Radio Interface Overview Cell Synchronisation Idle Mode Procedures Broadcast of system Information PLMN selection Cell Selection and Reselection RRC Connection Setup Procedure CS AMR Call Establishment PS Call Establishment Handover Procedures : Softer, Soft, Inter-RAT

IntroductionUE is powered up Cell search Radio frame synchronisation Read BCCH Read BCCH Cell selection Register with core network Originating AMR speech call Handovers Release of AMR speech call Cell selection UE is powered up Cell search

Radio frame synchronisation

Register with core network Originating PS Call

Cell State Transitions

AMR Speech call

PS Data call

Radio Interface Overview

UTRANUE Uu

UTRANRadio Network Subsystem (RNS)

CNMSC/VLR Iub Iu-CScircuit switched (cs) domain

RNCUu Iur UE

Iub

RNC

Iu-PS SGSN

packet switched (ps) domain

Radio Network Subsystem (RNS)

Protocol Stacks Communication between the UE, RNC and circuit switched core makes useof

Uu interface protocol stack Iub interface protocol stack Iu,cs interface protocol stack A interface protocol stack

Node B Uu Iub

RNC

Multimedia Gateway

3G MSC

Iu,cs

A

Protocol stacks include both user and control planes

CS Radio Interface Protocol (RIP) Control Plane The radio interface protocol control plane allows RRC signalling between the RNC and UE RRC signalling is communicated across the Iub using the Iub user plane protocol stack i.e. usingFrame protocol and AAL2 based ATM

Acknowledged or unackowledged mode RLC is used between the UE and RNC

UERRC RLC-C MAC

RNCRRC RLC-C

Node BFP AAL2

MAC FP AAL2 ATM Phy

WCDMA L1

WCDMA L1

ATM Phy

Uu

Iub

CS Radio Interface Protocol (RIP) User Plane The 3G MSC provides connectivity to the circuit switched core and PSTN Transparent mode RLC is used between the UE and RNC AAL2 based ATM is used to transfer user plane data across the Iub and Iu,cs interfaces

UEe.g. vocoder RLC-U MAC

Multimedia GW RNCRLC-U e.g. vocoder Iu,cs UP A Law PCM, etc

3G MSCA Law PCM, etc PSTN

Node BFP AAL2

MAC FP AAL2 ATM Phy

Iu,cs UP

AAL2 ATM Phy

AAL2 ATM Phy

WCDMA L1

WCDMA L1

ATM Phy

Link Layer Phy

Link Layer Phy Phy

Uu

Iub

Iu,cs

A

AS and NAS SignallingUE CN Iu edge nodeNAS signalling and User data i.e. MM, PMM & CC, SS, SMS, SM

UTRAN RNCAccess Stratum Signalling (Uu Stratum) RRC Access Stratum Signalling (Iu Stratum) RANAP

Access Stratum Strata were introduced to group protocols related to one aspect of service. In this course, especially the Access Stratum is of importance. The Access Stratum comprises infrastructure and protocols between entities of the infrastructure specific to the applied access technique. In UMTS it offers services related to the data transmission via the radio interface. It also allows the management of the radio interface on behalf of other parts of the network. Two access strata are defined in UMTS: UTRAN MT The protocols in use between UTRAN and the mobile phone specify in detail radio interface related information. AS signalling is used to inform the UE about how to use the radio interface in the UL and DL direction. UTRAN CN The CN requests the access network to make transmission resources available. The interaction between UTRAN and the CN is hereby independent of the interaction between the UTRAN and the UE. In other words, the UTRAN CN access stratum is independent of the used radio interface technology. In this course, we focus our interest mainly on the transmission of signalling information and related parameters via the radio interface. Consequently, the access stratum between the UE and UTRAN will be discussed in detailed. But also NAS signalling will be outlined. NAS signalling is exchanged between the UE and the serving network. In this course material, this signalling is regarded as part of the non-access stratum.

UMTS QoS ArchitectureTE MT UTRAN CN Iu edge node CN Gateway TE

End-to-End ServiceTE/MT Local Bearer Service External Bearer Service

UMTS Bearer Service = UMTS QoSRadio Access Bearer Service Radio Bearer Service UTRA FDD/TDD Service Iu Bearer Service Physical Bearer Service

CN Bearer Service

Backbone Bearer Service

Radio Interface Protocol ArchitectureControl Plane Signallingcontrol control control

User Plane

RRC Layer RBscontrol control

PDCP

PDCP PDCP

BMC RLC RLC

RLC LayerRLC

RLC RLC

RLC RLC RLC

LogCHs MAC Layer TrCHs PHY Layer PhyCHs

WCDMA Frame Radio frame: A radio frame is a processing duration which consists of 15 slots. Thelength of a radio frame corresponds to 38400 chips.

Slot: A slot is a duration which consists of fields containing bits. The length of a slotcorresponds to 2560 chips

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

10ms

Cell Search Procedure Radio Interface Synchronisation

Cell Synchronisation

Phase 1 P-SCH

Detect cells Acquire slot synchronisation

Phase 2 S-SCH

Acquire frame synchronisation Identify the code group of the cell found in the first step

Phase 3 P-CPICH

Determine the exact primary scrambling code used by the found cell Measure level & quality of the found cell

Radio Interface Synchronisation Cell synchronisation is achieved with the Synchronisation Channel (SCH). This channel divides up into two sub-channels: Primary Synchronisation Channel (P-SCH)

Secondary Synchronisation Channel (S-SCH) CPICH channel: Primary scrambling code identification

(continued on the next text slide)

Synchronisation Channel (SCH)2560 Chips 256 Chips

Primary Synchronisation Channel (P-SCH) CP

CP P

CP

CP

Secondary Synchronisation Channel (S-SCH) Cs1 Cs2 Cs15 Cs1

Slot 0

Slot 1

Slot 14

Slot 0

10 ms FrameCp = Primary Synchronisation Code Cs = Secondary Synchronisation Code

Step 1- Slot synchronization

Slot Synchronization

PSC : Primary synchronization code PSCH256 chip sequence transmitted in each slot interval Same for all cells and slot intervals Mobile Station uses the PSC to acquire slot synchronization The sot timing of the cell can be obtained by detecting peak values in the matched filter

TS Boundary

Matched filterStored PSCH

2560 chips

Step 2 - Frame SynchronizationSSC: Secondary synchronization code 256 chip sequence transmitted in parallel with PSC. In general different for different cells and slot intervals 16 different 256 chip sequence ( 16 secondary synch code) Code word of 15 consecutive SSC indicates cell scrambling code group There are 64 such code groups UE checks in each slot 16 possible SSC sequences and select which gives the

highest correlation value => 15 codes are selected The cyclic shift is unique and gives the frame synchronization and the scrambling code group

Slot No.Group1 Group2 Group3.. .. SSC1 SSC1 SSC1

0SSC1 SSC1 SSC2

1SSC2 SSC5 SSC1

2.. ..

14SSC16 SSC10 SSC12

Group64

SSC9

SSC12

SSC10

SSC10

SSC Allocation for S-SCHscrambling code group group 00 group 01 group 02 group 03 group 04 group 05 slot number0 1 1 1 1 1 1 1 1 1 2 2 2 3 2 2 5 1 3 16 4 3 8 16 15 1 6 7 4 9 7 5 8 6 4 5 10 3 5 6 11 1 6 15 14 12 5 15 5 7 8 16 16 2 5 5 8 10 3 6 5 12 3 9 16 10 11 8 1 6 10 2 5 2 4 15 2 11 7 12 16 4 12 8 12 15 14 11 6 16 7 13 7 12 15 3 11 6 14 16 10 12 7 2 8

group 62 group 63

9 9

11 12

12 10

15 15

12 13

9 14

13 9

13 14

11 15

14 11

10 11

16 13

15 12

14 16

16 10

11

15

5

I monitor the S-SCH

Step 3 - Scrambling Code Identification With the help of the SCH, the UE was capable to perform chip, TS, and frame synchronisation. Even the cells scrambling code group is known to the UE. But in the initial cell selection process, it does not yet know the cells primary scrambling code. There is one primary scrambling code in use over the entire cell, and in neighbouring cells, different scrambling codes are in use. There exists a total of 512 primary scrambling codes. How does UE identify Cells primary scrambling code ( 1 out of 512 codes)

Step 3 - Scrambling code Identification 1) Long Scrambling code :262143 Codes 2) To speed up the cell search => only 8192 codes 3) 8192 code grouping: 512 groups of 16 codes each (512*16 = 8192) 4) 16 codes in each group => first code is Primary scrambling code and 15 codes are Secondary scrambling codes 5) Again 512 codes are further divided into 64 groups of 8 codes 6) These 64 groups map to the 64 scrambling code group used at stage 2 during frame synchronization That way UE limits its Primary Scrambling code search to just 8 codes At this stage max 8 attempts to find out the Primary Scrambling code of the cell 7) Each cell is allocated one Primary scrambling code ( Carrying P-CPICH, PCCPCH, PICH, AICH and S-CCPCH) 8) Other channels can use Primary scrambling code or secondary scrambling codes from the same group

Primary Common Pilot Channel (P-CPICH)10 ms Frame2560 Chips 256 Chips

Synchronisation Channel (SCH)

CPP-CPICH

applied speading code = cells primary scrambling code Cch,256,0

Cell