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COMIT Training Course 1

Oct - 2015

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Objectives Describe how the radio connection supervision is carried out when the UE is using a common channel

Describe how in-sync and out-of-sync is determined by the radio link set supervision algorithm in the RBS when the

UE is using a dedicated channel

Describe how the RNC supervises radio link (sets) when the UE is using a dedicated channel

Describe how a call is dropped

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Radio Connection Supervision The Radio Connection Supervision (RCS) algorithm supervises the radio connection between

 WCDMA RAN and a UE in connected mode. The purpose is to judge whether or not WCDMA RAN

still has control over the UE. This supervision is only performed in WCDMA RAN for the uplink.

Supervision of the downlink is carried out by a similar supervision function located in the UE.The main goals of the supervision functionality are to:

• Achieve an efficient resource usage in WCDMA RAN 

• Avoid any long-term discrepancy concerning the status of the connection between the UE

and WCDMA RAN

• Avoid undue charging to customers The supervision is carried out in different ways depending on the UE state

(Cell_FACH or Cell_DCH).

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SUPERVISION OF THE UE IN STATE

CELL_FACH

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SUPERVISION OF THE UE IN STATE

CELL_FACH a) If the UE does not receive a Cell Update Confirm it will repeat the Cell Update message

a number of times before it moves to idle mode.

b) If the UE detects “Out of service area” it waits a period of time before it moves to idle

mode.

c) Upon expiry of the timer cchWaitCuT the overall release of the connection shall be

triggered and as a result the UE context is released in WCDMA RAN. The time set on the

timer cchWaitCuT is longer then the time set on timer t305 - that indicates how often the

UE has to send a Cell Update message and also long enough to allow the actions taken incase of a) and b).

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SUPERVISION OF THE UE IN STATE

CELL_DCH The Radio Connection Supervision

functionality is provided by means of two

different algorithms; the Radio Link Set

Supervision algorithm (in the RBS) and the

Radio Connection Supervision Evaluation

algorithm (in the SRNC)

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SUPERVISION OF THE UE IN STATE

CELL_DCHRadio Link Set Supervision considersthe UE belonging to one out of threedifferent synchronization states. Instate “In-sync”uplink data is

transmitted over Iub.

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RADIO CONNECTION SUPERVISION

EVALUATION This algorithm keeps track of the synchronization status of the radio

connection by assigning a tag to every RLS. Upon creation of a new RLSthe tag is set to "Fail". The tag is shifted to "OK" upon reception of a RLrestore indication and then to "Fail" upon reception of a RL failureindication. If all RLSs are tagged as "Fail" and the timer has expired,then the radio connection shall be considered lost and the overallrelease of the connection is triggered.

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RRC State Machine

URA_PCH

CELL_DCH CELL_FACH

CELL_PCH

UTRA RRC Connected Mode

Idle Mode

UE in DRX mode

discontinous reception

UE in DRX mode

discontinous reception

Dedicated resources

allocated (DCH, HS)

Tx and Rx mode

Common resources

allocated (RACH-FACH)

Tx and Rx mode

Cell selection

Cell re-selection

Listen to paging

Common Channel

Setup (optional)

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PS Connection Establishment

RNCUE SGSN

RRC Connection Establishment (SRB)

MM, CC & SM (e.g. PDP Context Activation)

RAB Assignment RequestTraffic VolumeParametersdetermination

Measurement Control* [Traffic Volume Measurements]

CELL_DCH

Start• UL_DLcapacityReqWait• SignallingLinkInactivityTimer

UL_DLcapacityReqWait

expiry

Capacity Request?

DCH for NRT RB(s) allocation

no

 yes

 yes

SignallingLinkInactivityTimeexpiry

CELL_

FACH

*RLC buffer level, reporting criteria, etc.

UL_DLcapacityReqWait 

RNC; 0..20; 0.5; 5 s

SignallingLinkInactivityTimer  RNC; 0..20; 0.5; 2 s

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Transition from .. / to ..

StartMAC: Inactivity detected

“FACH activation timer” 

UECELL

_FACH

Expiry

RNC

Cell Update

Cell Update

Cell Update Confirm

Transition to CELL_PCH

 MSActivitySupervision

CELL_

PCH

RRC-IDLE

CELL_

PCH Physical Channel Reconfiguration

“FACH activation timer” = ExtendedULDLActivationTmr   for UEs NOT supporting CELL_PCH 

= UL_DL_activation_timer   for UEs supporting CELL_PCHor always if ExtendedULDLActivationTmr  = 0

Start

Expiry

Cell Update

ExtendedULDLactivationTmrRNC; 0..120; 1; 0 s

UL_DL_activation_timerRNC; 0..10 s; 50 ms; 2 s

MSActivititySupervision RNC; 0..1440; 1; 29 min

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Transition from.. / to ..

CELLF ACH Cell Update (Cell reselection)

Cell Update (Cell reselection)

Cell Update Confirm

URA_PCH

 MaxCellReselectionsCellReselectionObservingTime

Start

Expiry

URA Update

URA Update

URA Update Confirm

Inactivity detected

Transition to URA_PCH

 MSActivitySupervision

URA_PCH

RRC-IDLE Expiry

CELLPCH

or

High mobility UE is detected based on the frequency of cell reselections – if more than N  reselections

occur within T  seconds, RNC moves UE from Cell_FACH or Cell_PCH to URA_PCH:

The maximum time a UE can stay in UTRAN PCH states is limited by  MSActivitySupervision parameter.

 MaxCellReselections

RNC; 0 .. 100; 1; 3 times

T305Periodic Cell/URA Updates

0 (no), 5, 10, 30..720 min; 30 min

CellReselectionObservingTime

RNC; 0 .. 60; 1; 16 min

MSActivititySupervision

RNC; 0..1440; 1; 29 min

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R t i f C ll/URA PCH t

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Returning from Cell/URA_PCH to

Cell_DCH

CELL_PCH orURA_PCH

Cell Update (Paging Response)

Data detected in GTP

UL & DL packet scheduling

Radio Link SetupCell Update Confirm

(SRB-DCH and 0/0 for PS)

Paging

CELL_DCH

TrafVolThrDLLowGTP

0..1024 Byte; 128 Byte

CUCforPCHtoDCHallowed

defines if it is allowed to move UEdirectly from Cell/URA_PCH to

Cell_DCH

RNC; false (0), true (1)

CELL_FACH

 After transition: UE stays in Cell/URA_PCH until new data UL/DL in L2 buffers.

Direct return / reconfiguration to Cell_DCH possible, if traffic volume threshold TrafVolThrDLLowGTP  exceeded &

CUCforPCHtoDCHallowed  = true. Signaling procedure below.RNC must send a paging notification to get in touch with UE.

UE answer with RRC: Cell Update (cause: paging response)

RNC initiated

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Returning from Cell/URA_PCH to Cell_DCHOn reception on Cell Update message from UE, RNC checks if

a) CUCforPCHtoDCHallowed  = 1 (true) and b) EcNo > CUCEcNoThreshold  (default = – 8,5 dB)

 RNC sends Cell Update Confirm message.

If a) is or b) reported EcNo < CUCEcNoThreshold>, RNC moves UE to Cell_FACH. 

CELL_PCH orURA_PCH

Cell Update (Ec/No; Traffic Volume Indicator = TRUE)

Data detected in UE L2

UL & DL packet scheduling

Radio Link SetupCell Update Confirm

(SRB-DCH and 0/0 for PS)

Rel5 UE& newer

CELL_DCH

CUCforPCHtoDCHallowed0 = false, 1 = true

&Ec/No > 

CUCEcNoThreshold WCEL; 0..49; 1;  31 = -8.5 dB

CUC: Cell Update Confirm

CELL_FACH

UE initiated

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Transition: Cell/URA_PCH to

Cell_FACHThe UE sends RRC: Cell Update message to RNC to inform about specific event.

Following trigger reasons for Cell Update procedure are defined in 3GPP:

• Periodical Cell Update / URA Update (based on T305)

• Cell Update due to Cell Reselection (S-criteria)

• UL Data Transmission (L2 buffer data volume)

• RLC unrecoverable failure (L2 RLC procedure failure)• Paging Response (answer to RNC paging)

• Re-entering service area (UE back in network coverage)

• Radio Link Failure (DL L1 fails in Cell_DCH)

CELL_PCH URA_PCH

Cell_FACH

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Transition: CELL_FACH to CELL_DCH

RNCUECELL_

FACH Node B

Radio Bearer Reconfiguration

Measurement Report (Traffic Volume Event; CR )

CELL_DCH

Radio Link Setup

Radio Bearer Reconfiguration Complete

UE initiated

Defined & discussed later

UL & DL packet scheduling

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