mobility management.pdf

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UMTS Networks 1Oliver Waldhorst, Jens Mckenheim Oct-11

Mobility Management (MM)

References:

Kaaranen, Ahtiainen, Laitinen, Naghian, Niemi: UMTS Networks Architecture, Mobilityand Services. Wiley 2001, Ch. 5.2 (MM states) and 10.3 (MM procedures)

3G 23.060 GPRS Service Description

3G 24.007 Mobile radio interface signaling layer 3, General aspects

Different MM schemes for CS and PS mode

MM states

Involved protocols Procedures


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Mobility Management (MM) Basics

Mobility Management covers all procedures, methods and identities required to maintain knowledge about the UEs locations when it is

moving in the network

Involved entities

UE CN

SGSN (PS mode, transitions between PMM states) MSC/VLR (CS mode, transitions between MM states) HLR (in home network)

in MM/PMM connected mode RNC (cell and/or URA updates) GGSN/GMSC

in case of roaming visited PLMN


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CS Mobility Management States

MM in CS mode is highly related to connection management

MM-Idle

MM-Connected

MM-Detached

call completion

call setup orLA update

cell known

LA unknown(no paging)

LA known(paging possible)

active call(or signaling)

no active call(nor signaling)

UE switched off

MM state is maintained in UE and MSC/VLR

IMSI attach orLA update (UE is switched on)

IMSI detach


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PS (GPRS) Mobility Management States

P M M -

D E T A C H E D

P S A t ta c h

P S S i g n a l li n g

C o n n e c t io n R e l e a s e


C o n n e c t i o n E s t a b l is h

P S D e t ac h

P MM -

CONNEC TEDPMM - I D LE

D e t a c h ,

P S A t ta c h R e j e ct ,

R A U R e j e ct

P MM -

D E T A C H E D

P S D e t ac h

P MM -

CONNEC TED

S e r v in g R N C r e loc a t i on

3 G -S G S N M M S t ate sM S M M S t a te s

S M - A C T I V E o r

I N A C T I V E

S M - A C T IV E o r

I N A C T I V E


I N A C T I V E


I N A C T I V E

D e t a c h ,

P S A t ta c h R e j e c t

R A U R e je c tP S A t ta c h


C o n n e c t i o n E s t a b l is h


C o n n e c t io n R e l e a s ePMM - I D LE

Source: 3GPP 23.060-4.1.0

GPRS attach

GPRS detach

Paging only(no signaling

connectionbetween MSand SGSN)

SignalingconnectionbetweenMS and SGSN(addressingby U-RNTI)

PS Mobility Management (PMM) isindependent of Session Management (SM),e.g. availability of IP address & traffic activity

PMM is independent of the number and state of PDPcontexts for the subscriber

In both the PMM-IDLE and the PMM-CONNECTED states,session management may or may not have activated a PDPcontext (assigned a dynamic IP address)

U-RNTI: UTRAN - Radio Network Temporary Identity


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Signaling Connection

No signaling connection exists (MM/PMM-IDLE state)

UE has no relation to UTRAN, only to CN no data transfer

paging identification by IMSI, TMSI, P-TMSI

Signaling connection exists (MM/PMM-CONNECTED state)

Addressing by U-RNTI

UE position can be known on different levels:

- URA level (UTRAN registration area): URA is a specified set ofcells, which can be identified on the broadcast channel (BCCH)

- Cell level: Different channel types can be used for data transfer:

- Common transport channels (RACH, FACH, CPCH, DSCH)

- Dedicated transport channels (DCH)

Source: 3GPP 25.301-4.1.0, ch 6.2


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Relations between CM/SM, MM/PMM and RRCStates

CoreNetwork

CM/SM state(s)

(UE-SGSN-GGSN)

Subscrip-tion

PDCPaddress

inactive active

MM/PMM state

(UE, SGSN, HLR)

detached idle connected

UTRAN

Signalingconnection

(UE-SGSN)

none yes

RRC state

(UE-RNC)

idle connected

Addressingusing RNTI

Paging usingTMSI/P-TMSI

(cell_DCH, cell_FACH,cell_PCH, or URA_PCH)


7/15UMTS Networks 7Oliver Waldhorst, Jens Mckenheim Oct-11

PS Mobility Management States

PMM-DETACHED State:

No communication between the MS and the SGSN MS and SGSN hold no valid location or routing information for the MS

MS MM state machine does not react to system information related tothe SGSN

MS is not reachable by the PLMN, as the MS location is not known to

the SGSN

MM context establishment:

GPRS-attach procedure: establish MM contexts in the MS and the SGSN

When PS signalling connection is established between the MS and

the SGSN for performing the GPRS attach, the state changes toPMM-CONNECTED in the SGSN and in the MS

The PS signalling connection is made up of two parts: an RRCconnection and an Iu connection

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PMM-CONNECTED State: MS location is known in the SGSN with an accuracy of a serving RNC

Location of the MS is tracked by the serving RNC MS performs the routing area update procedure when RAI changes

A PS signaling connection is established between the MS and the SGSN

Release of signaling connection (move to PMM-IDLE state):

In SGSN: PS signalling connection release or failed downlink transfer with cause

"IMSI unknown in RNC" changes the state to PMM-IDLE In MS: enter the PMM-IDLE state when its PS signaling connection to the SGSN

has been released or broken (release or failure is explicitly indicated by theRNC to the MS or detected by the MS > RRC connection failure)

Signaling connection is also released if a URA update fails because of "RRCconnection not established", or if the URA update timer expires while the MS is

out of coverage SGSN may decide to release the PS signaling connection after a signaling

procedure (e.g. routing area update)

MM context release:

GPRS detach changes the state to PMM-DETACHED

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PMM-IDLE State:

MS location is known in the SGSN with an accuracy of a routing area

Paging is needed in order to reach the MS, e.g. for signalling

MS and SGSN have established MM contexts

MS performs a routing area update if the RA changes

(signaling towards the HLR is needed if the (new) SGSN does not havean MM context for this MS)

Establishment of signaling connection (move to PMM-CONNECTED state):

MS and SGSN enter the PMM-CONNECTED state when the PS signallingconnection is established between the MS and the SGSN

MM context release:

GPRS detach procedure changes the state to PMM-DETACHED SGSN may perform an implicit GPRS detach any time after the MS

reachable timer expiry; the MS's MM context is deleted, preferably aftera certain (implementation dependent) time; the HLR may be informedabout the deletion

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Mobility Management Involved Protocols (PS mode)

Protocols used by MM procedures

Uu: RRC protocol

Iu: RANAP protocol

Gr (SGSN and HLR): MAP protocol

Gf (SGSN and EIR): MAP protocol

Gs (SGSN and VLR): BSSAP+ protocol

Source: 3GPP 23.060-4.1.0, Ch 6.4

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Mobility Management Procedures

Connected state

Cell update (PS mode): UE-UTRAN interaction

URA update (PS mode): UE-UTRAN interaction

Idle state

RA Update (PS mode): UE-CN interaction (transparent to UTRAN) LA Update (CS mode): UE-CN interaction (transparent to UTRAN)

See also Kaaranen, ch 10.3



Cell Update (PS)

UE RNC

RRC: cell update

RRC: cell update confirm

PS mode:

-> explicit cell update procedure

Reasons for cell update

cell reselection

periodic cell update

uplink data transmission

paging response re-entered service area

radio link failure

unrecoverable RLC error

CS mode:

continuous exchange of cellinformation during call (or transaction)

exchange of RRC msgs

reason forcell update



URA Update (PS)

PS mode:

-> explicit URA update procedure

Reasons for URA update

URA identity changes

periodic URA update

UE RNC

RRC: URA update

RRC: URA update confirm

exchange of RRC msgs

reason forURA update



RAUpdate(withch

angeofS

GSN)


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