A Seamless Vertical Handover ApproachVertical Handover ... · PD er ha n respo n timer handover...

Institute of Computer ScienceDepartment of Distributed SystemsDepartment of Distributed Systems

Prof. Dr.-Ing. P. Tran-Gia

A Seamless Vertical Handover ApproachVertical Handover Approach

www3.informatik.uni-wuerzburg.deRastin Pries, Dirk Staehle, Thorsten GutbrodRastin Pries, Dirk Staehle, Thorsten Gutbrod

Issues for Vertical Handover Policies

(2) Handover, yes or no?

(3) If yes, when to handover?

WLANHotspot

( ) y ,

(1) Which connection to choose? WLAN or UMTS?

UMTS NodeB

2A Seamless Vertical Handover Approach

UMTS NodeB

WLAN or UMTS?

Decision requires knowledge of current situation in all networks

We needAn architecture for coupling the technologiesAn architecture for coupling the technologiesA vertical handover protocolAdmission control for each technologygy

We need a network entity forStoring the current situation of the whole networkAllowing a predictive investigation of networks` behaviorsInitiating the handover between different technologiesInitiating the handover between different technologies


Ideas for a Vertical Handover Approach

SimplicityPredefined handover criteria, no user interaction needed

Hotspots with better services and higher bandwidths

Reduced costsfor provider and user by using cheaper network technologiesp y g p g

Better network coverageWireless LAN increases indoor usage in buildings

Reduced network loadReduced network load


Coupling – Possibilities

P ibiliti f li th

WLANAP

Possibilities for coupling the different network technologies

Very tight couplingTight couplingLoose couplingVery loose couplingVery loose coupling


Our Approach – Design

Tight coupling architectureDirectl connected to the SGSNDirectly connected to the SGSN

Being able to work on data link layer / layer 2No need for Mobile IP etc.Fast handover

Network initiated handover

Using services provided by UMTS networkAccess controlAccountingAccounting


Example of Handover

UMTS

AP

WLAN Handover

SGSN GGSN Server

ME Node B RNC


Protocol Stack – Mobile Equipment

Changes in data link layerVertical handover management layer is

applications

TCP UDP rk a

ndla

yers

management layer is introduced at top of the data link layer IP

TCP UDP

netw

orhi

gher

Accordingly to that UMTS GMM has to be adapted

vertical handover management

handovermessages

handovercommands er

Wireless LAN GMM– Placed on top of the

Wireless LANGMM

UMTSGMM

g

data

link

laye

pWireless LAN MAC

– Responsible for connection to SGSN

UMTSMAC

Wireless LANMAC

d

UMTSphysical layer

Wireless LANphysical layer

phys

ical

laye

r


Protocol Stack – Mobile Equipment

netw

ork

and

high

er la

yers

ayer

data

link

laph

ysic

alla

yer


Protocol – UMTS to Wireless LAN

ME AP Node B RNC SGSN

WLAN device activation req. (SSID AP, channel AP)

assoc. req.assoc. resp.

Wirel

AP ACL entry insert req.

oc.

merer

create inactive tunnel

ess LAN activation tim

assoc. ack.

P ac

tivat

ion

timer PDP context req.

create active tunnelPDP context

req.

ass

tim

devi

ce a

ctiv

atio

n tim

e

connectionestablishment

WLAN device activation resp.

PDP context accept

handover initiation

switch toWLAN

merP

D

hanrespon ti

mer

handover responseWLAN

switch toWLAN

ndovernse tim

eractivate tunnel

handover completehand

over

initi

atio

n

handover

set tunnelstandby

RB release completeRB release req.

remove tunnel

RAB rel. req.

devi

ce d

eact

. ti

mer U

MTS

deactim

e connectionremove tunnel

RAB rel. resp.

RL del. resp.

RL del. req.

UMTS

Wireless LAN

ctivationr

releaseUMTS

Wireless LAN



Wireless LANconnection establishment

UMTS

Wireless LAN



handover initiationhandover initiation

handover response

switch toWLAN

switch toWLAN

activate tunnel

handover complete

handoverfrom UMTS to Wireless LAN

UMTS

Wireless LAN



set tunnelstandby


t l

RAB rel. req.

remove tunnel

RAB rel resp

RL del. resp.

RL del. req.

RAB rel. resp.

UMTSconnection release

UMTS

Wireless LAN


Protocol – Wireless LAN to UMTS


UMTS device activation req.

PDP context req.create

inactive tunnel


UM

TS activation timer

PDP

activ

atio

ntim

er

devi

ce a

ctiv

atio

n tim

er

RB setup complete

RB setup req.

create activetunnel

RAB asc. req.RL add. req.

RL add. rsp.

rr

UMTS device activation resp.

PDP context accept

handover initiation

tunnelRAB asc. rsp.

handoverhandover

esponse timer

hand

over

initi

atio

n tim

erhandover response

switch toUMTS

activatetunnel

switch toUMTS

handover complete

connection

WLA

N deactivtim

erdisassoc.

remove tunnel

WLAN device deactivation req.

remove tunneldeact. req.

disass Ack

handover complete

disa

ss.

timer

ce d

eact

. tim

er

release

vationWLAN device deactivation resp.disass. Ack.

UMTS

Wireless LAN

d

devi

c

UMTS

Wireless LAN




UMTS device activation req.

PDP context req.

RAB asc. req.

createinactive tunnel

RB setup req.

RL add. req.

RL add. rsp.

RB setup completecreate active

tunnelRAB asc. rsp.

UMTS device activation resp.

PDP context accept

UMTSconnection establishment

UMTS

Wireless LAN



rhandove

response timdove

ron

tim

er

ermer

hand

initi

atio

handoverfrom Wireless LAN to UMTS

UMTS

Wireless LAN



remove tunnel

di

remove tunnel

WLAN device deactivation req.

remove tunneldeact. req.

disassoc.

WLAN device deactivation resp.disass. Ack.

Wireless LANconnection releaseUMTS

Wireless LAN


Fallback Solutions

Errors can appear in every single step of the handover process

Errors could beMissing reactionNegative responsesUnexpected messages

How to detect errors and how to handle them?Missing reaction is detected with timers

– Due to handover and process state start a fallback solutionNegative responses directly starts a fallback solutionUnexpected messages are inspected

Fallback solutions can result inRetriesAbort handoverAbort handoverRevert handoverForce handover


Handover Delays

From UMTS to Wireless LANOverall handover: 500 ms 600

700800

overallOverall handover: 500 ms

– Establishment: 230 ms– Pure handover: 105 ms

Connection release: 165 ms 200300400500

time

[ms] establishment

pure handover

i– Connection release: 165 ms0

100

UMTS to Wireless LAN

connectionrelease


Handover Delays

From UMTS to Wireless LANOverall handover: 500 ms 600

700800

overallOverall handover: 500 ms

– Establishment: 230 ms– Pure handover: 105 ms

Connection release: 165 ms 200300400500

time

[ms] establishment

pure handover

i– Connection release: 165 ms0

100


connectionrelease

From Wireless LAN to UMTSOverall handover: 732 ms

600700800

overall

– Establishment: 535 ms– Pure handover: 98 ms– Connection release: 100 ms 200

300400500600

time

[ms] establishment

pure handover

0100200

Wireless LAN to UMTS

connectionrelease


Optimization – Preferred Networks (1)


WLAN device activation req. (SSID AP, channel AP)

assoc. req.assoc. resp.

Wirel

AP ACL entry insert req.

oc.

merer

create inactive tunnel

ess LAN activation tim

assoc. ack.

P ac

tivat

ion

timer PDP context req.

create active tunnelPDP context

req.

ass

tim

devi

ce a

ctiv

atio

n tim

e


WLAN device activation resp.

PDP context accept

handover initiation

switch toWLAN

merP

D

hanrespon ti

mer

handover responseWLAN

switch toWLAN

ndovernse tim

eractivate tunnel

handover completehand

over

initi

atio

n

handover

set tunnelstandby


remove tunnel

RAB rel. req.

devi

ce d

eact

. ti

mer U

MTS

deactim

e connectionremove tunnel

RAB rel. resp.

RL del. resp.

RL del. req.

UMTS

Wireless LAN

ctivationr

release



Three messages in handover protocol can be send via both networksnetworks

UMTS or Wireless LAN device activation responseHandover initiationHandover initiationHandover response

Choosing the faster network



800

1000

ms]

Three messages in handover protocol can be send via both networks

200

400

600

over

all t

ime

[m

prefer UMTSstandardprefer WLAN

networksUMTS or Wireless LAN device activation responseHandover initiation

0

200o


Handover initiationHandover response

Choosing the faster network

150

200

ms]


50

100

150

ndov

er ti

me

[m


[ms] Establ. VHO Release OverallUMTS 230 200 170 600Std 230 105 165 500

0

50

han


Std. 230 105 165 500WLAN 117 <1 163 280



800

1000

ms]

200

400

600

over

all t

ime

[m


Wireless LAN to UMTS0

200o



[ms] Establ. VHO Release OverallUMTS 630 200 100 930

150

200

ms]

UMTS 630 200 100 930Std. 535 98 100 732

WLAN 535 <1 115 650

50

100

150

ndov

er ti

me

[m


0

50

han



Extension – Queue Forwarding

Queue forwardingWhen switching networks at the client, packets that were l d i f th h d d l t th GMM d lalready given from the handover module to the GMM module

cannot be transferred when the connection is releasedThe queued packets were destroyed when releasingq p y gQueue forwarding is managed by the handover module which sends an forward queue interrupt to the GMM which will be releasedreleasedThe GMM sends the handover module the queued packets which forwards them to the active GMMThe packets that arrived at the active GMM were queued at the top position of the queue

handover

WLAN UMTS


Conclusion

Seamless vertical handoveroverall handover delay below 1 secondpure handover switching time below 1 millisecond possible

Bottleneck is the UMTS air interfaceFaster handover by using HSPA or HSOPA/LTE instead of R99

Future workintegration of HSDPA HSUPA and WiMAXintegration of HSDPA, HSUPA, and WiMAX


Thank you for your attention!

Questions?


A Seamless Vertical Handover ApproachVertical Handover ... · PD er ha n respo n timer handover...

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