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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
3A Seamless Vertical Handover Approach
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
4A Seamless Vertical Handover Approach
Coupling – Possibilities
P ibiliti f li th
WLANAP
Possibilities for coupling the different network technologies
Very tight couplingTight couplingLoose couplingVery loose couplingVery loose coupling
5A Seamless Vertical Handover Approach
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
6A Seamless Vertical Handover Approach
Example of Handover
UMTS
AP
WLAN Handover
SGSN GGSN Server
ME Node B RNC
7A Seamless Vertical Handover Approach
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
8A Seamless Vertical Handover Approach
Protocol Stack – Mobile Equipment
netw
ork
and
high
er la
yers
ayer
data
link
laph
ysic
alla
yer
9A Seamless Vertical Handover Approach
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
10A Seamless Vertical Handover Approach
Protocol – UMTS to Wireless LAN
Wireless LANconnection establishment
UMTS
Wireless LAN
11A Seamless Vertical Handover Approach
Protocol – UMTS to Wireless LAN
handover initiationhandover initiation
handover response
switch toWLAN
switch toWLAN
activate tunnel
handover complete
handoverfrom UMTS to Wireless LAN
UMTS
Wireless LAN
12A Seamless Vertical Handover Approach
Protocol – UMTS to Wireless LAN
set tunnelstandby
RB release completeRB release req.
t l
RAB rel. req.
remove tunnel
RAB rel resp
RL del. resp.
RL del. req.
RAB rel. resp.
UMTSconnection release
UMTS
Wireless LAN
13A Seamless Vertical Handover Approach
Protocol – Wireless LAN to UMTS
ME AP Node B RNC SGSN
UMTS device activation req.
PDP context req.create
inactive tunnel
connectionestablishment
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
14A Seamless Vertical Handover Approach
Protocol – Wireless LAN to UMTS
ME AP Node B RNC SGSN
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
15A Seamless Vertical Handover Approach
Protocol – Wireless LAN to UMTS
rhandove
response timdove
ron
tim
er
ermer
hand
initi
atio
handoverfrom Wireless LAN to UMTS
UMTS
Wireless LAN
16A Seamless Vertical Handover Approach
Protocol – Wireless LAN to UMTS
remove tunnel
di
remove tunnel
WLAN device deactivation req.
remove tunneldeact. req.
disassoc.
WLAN device deactivation resp.disass. Ack.
Wireless LANconnection releaseUMTS
Wireless LAN
17A Seamless Vertical Handover Approach
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
18A Seamless Vertical Handover Approach
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
19A Seamless Vertical Handover Approach
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
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
20A Seamless Vertical Handover Approach
Optimization – Preferred Networks (1)
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
release
21A Seamless Vertical Handover Approach
Optimization – Preferred Networks (2)
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
22A Seamless Vertical Handover Approach
Optimization – Preferred Networks (2)
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
UMTS to Wireless LAN
Handover initiationHandover response
Choosing the faster network
150
200
ms]
UMTS to Wireless LAN
50
100
150
ndov
er ti
me
[m
prefer UMTSstandardprefer WLAN
[ms] Establ. VHO Release OverallUMTS 230 200 170 600Std 230 105 165 500
0
50
han
UMTS to Wireless LAN
Std. 230 105 165 500WLAN 117 <1 163 280
23A Seamless Vertical Handover Approach
Optimization – Preferred Networks (3)
800
1000
ms]
200
400
600
over
all t
ime
[m
prefer UMTSstandardprefer WLAN
Wireless LAN to UMTS0
200o
Wireless LAN to UMTS
Wireless LAN to UMTS
[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
prefer UMTSstandardprefer WLAN
0
50
han
Wireless LAN to UMTS
24A Seamless Vertical Handover Approach
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
25A Seamless Vertical Handover Approach
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
26A Seamless Vertical Handover Approach
Thank you for your attention!
Questions?
27A Seamless Vertical Handover Approach
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