GEWLAN Seamless Handover

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UTD-ETRI Mid year project presentation
3GE-WLAN Seamless Handover

• Shanthy Menezes, S. Venkatesan
• UT-Dallas

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Characteristics of Interworking Scenarios2
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Research on Interworking Architectures

• Broadband Radio Access Networks (BRAN) by ETSI3
• WLAN-GPRS integration by Salkintzis et al.4
• Evaluation of architectures by Tsao and Lin5

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BRAN by ETSI

• Two architectures defined for interworking
  between HIPERLAN/2 and 3G systems
• Loose coupling is defined as the utilization of
  HIPERLAN/2 as an access network complementary to
  current 3G access networks, utilizing the
  subscriber databases but without any user plane
  Iu type interface, i.e. avoiding the SGSN, GGSN
• Connecting HIPERLAN/2 network to the rest of the
  UMTS network (the core network) in the same
  manner as other UMTS radio access technologies
  (UTRAN, GERAN) using a new interface is termed
  Tight Coupling.

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Tight Coupling Architecture of BRAN
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Tight Coupling for WLAN-GPRS Integration
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Tight Coupling Protocol Architecture
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Loose Coupling for WLAN-GPRS Integration
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WLAN Authentication Protocols for Loose Coupling
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Tight Coupling using RNC Emulator
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Performance Evaluation by Tsao and Lin
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Architecture Comparisons
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Architecture Comparisons
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Architecture Comparisons
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Handover Categories

• Horizontal Handover (HO)
• HO between base stations utilizing the same radio
  access technologies
• Vertical Handover
• HO between base stations that use different radio
  access technologies

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Vertical HO Categories
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Handover Algorithms
Traditional
High Complexity
Vertical HO based on prediction
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Traditional Algorithms
Input Value V Received Signal Strength OR Signal
to Interference Ratio
If V from new BS V from old BS then HO to new
BS
If (V from old BS V from old BS) then HO to new BS
If V from new BS V from old BS Hysterisis h
then HO to new BS
If (V from old BS new BS V from old BS Hysterisis h) then HO
to new BS
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Traditional AlgorithmsDirection Biased
Handover To BS2
Candidate BS 1
Mobile Direction
Candidate BS 2
Signal Strength from BS1
Signal Strength from BS2
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Traditional Algorithms

• Distance Based
• HO to the nearest BS
• Velocity Adaptive
• Employ a variable hysterisis and threshold based
  on mobiles velocity

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High Complexity Algorithms

• Dynamic Programming Based
• Utilizing Pattern Recognition
• Neural Network Based
• Fuzzy Logic Based

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Vertical HO Algorithms

• Hybrid Information System (HIS) based HO by Lott
  et al. 6
• HO in mobile data networks by Pahlavan et al 7
• Location Assisted HO by Leeuwen et al.8

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HIS based HO
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Pahlavan et al
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Location Assisted HO

• Best suited for fast vehicular users.
• Assumptions
• Measurement reports of the mobile are available
  in the current network (WLAN or UMTS).
• and
• Mobile periodically sends its GPS coordinates to
  the current network.

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Location Assisted HO Algorithm

• Predict what the mobile location will be when it
  sends the next measurement report.
• Calculate the probability P, that at this
  location HO is required.
• If P Threshold initiate HO

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Our Contribution
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Fast MIPv6 Handover (Predictive)
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Fast MIPv6 Handover (Predictive)
MN detects new AP (link specific method)
Router Sol for Proxy Adv
Proxy Router Adv
Fast Binding Update
HI
Hack
Fast Binding Ack
Fast Binding Ack
Disconnect
Forward packets
Disconnect
Fast Neighbor Advertisement
Deliver packets
MN
Previous AR
New AR
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Fast MIPv6 Handover (Reactive)
MN detects new AP (link specific method)
Router Sol for Proxy Adv
Proxy Router Adv
Disconnect
Connect
FNA FBU
Fast Binding Update
Fast Binding ack
Forward packets
Deliver packets
MN
Previous AR
New AR
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3GPP-WLAN Interworking System1
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FMIPv6 based Fast HO in UMTS-WLAN

• GGSN Router that provides IP access to MN in
  UMTS
• PDG Router that provides IP access to MN in WLAN
• GGSN and PDG participate in fast HO

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WLAN to UMTS HO

• Network provides three link layer triggers to MN
• Trigger one MN detects movement to new subnet
• Trigger two MN starts pre-authentication
• Trigger 3 MN initiates FBU and then HO

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Movement Detection
Router Sol for Proxy Adv
Construct response containing Prefix, IP address
and L2 address
Proxy Router Adv
PDG
MN
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Pre-authentication

• Without using UMTS interface
• Activate UMTS interface and use UMTS

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Pre-authentication without UMTS interface

• MN sends GPRS attach to SGSN through WLAN
  interface (via WAG)
• SGSN authenticates by communicating with
  HLR/HSS/AuC
• After authentication, state of MN at SGSN and MN
  PMM_IDLE
• GPRS attach procedure is executed while UMTS
  interface is in receive mode
• Need interface between WAG and SGSN
• Protocol stack at MN and WAG needs to be modified

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Pre-authentication using UMTS Interface

• Initially, UMTS interface of MN in receive mode
• MN transmits on UMTS interface
• Perform GPRS attach
• After successful GPRS attach, UMTS interface
  returns to receive mode

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After pre-authentication
FBU
HI
HACK
Setup tunnel between Previous CoA and New CoA
Disconnect from WLAN and connect to UMTS
Fast Neighbor Advertisement
Deliver tunneled packets
BU to HA and CN
MN
PDG
GGSN
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UMTS to WLAN HO

• In addition to network provided triggers, MN has
  internal triggers

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Movement Detection
Router Sol for Proxy Adv
Construct response containing Prefix, IP address
and L2 address
Proxy Router Adv
GGSN
MN
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Pre-authentication

• Without using WLAN (using only UMTS interface)
• Activate WLAN interface and use WLAN

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Pre-authentication without WLAN interface

• MN performs EAP authentication and authorization
  procedure via UMTS
• Change state of MN to WLAN-attach
• Needs
• EAP over WLAN is to run on UTRAN (modification
  needed)
• Wg interface between WAG and 3GPP AAA server
  needs enhancement for exchanging EAP messages

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Pre-authentication using WLAN Interface

• Initially, WLAN interface of MN in receive mode
• MN transmits on WLAN interface
• Perform EAP authentication
• Change WLAN to receive mode

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After pre-authentication
FBU
HI
HACK
Setup tunnel between Previous CoA and New CoA
Disconnect from UMTS and connect to WLAN
Fast Neighbor Advertisement
Deliver tunneled packets
BU to HA and CN
MN
GGSN
PDG
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HO Trigger to Aid FMIP6

• Challenges
• When to trigger?
• Predicting the next Access Point?

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When to Trigger?
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Inputs to Prediction Algorithm

• Signaling strength of neighboring APs.
• Direction of the mobile.
• Geographical terrain information Consists of
  terrain map with position of APs and possible
  directions for users while on this terrain.
• Handover history with direction A list of (AP1,
  ?, AP2, Rating), where the Rating increases each
  time the mobile goes from AP1 to AP2 while moving
  in the direction ?.

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Inputs to Prediction Algorithm

• Path history A history of sequence of APs
  traversed by all mobiles.
• Current Path The current sequence of APs
  traversed by the mobile.
• Map of coverage areas of all neighboring APs.

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Prediction AlgorithmStep I
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Prediction AlgorithmStep II
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Prediction AlgorithmStep III
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Prediction AlgorithmStep IV
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Prediction AlgorithmStep V
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Prediction AlgorithmStep VI Choose Best AP
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OPNET Modeler

• Modeling using Finite State Machine
• Programming Language C/C
• Most networks already modeled

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OPNET Modeling Domains
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802.11 WLAN in OPNET
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UMTS network in OPNET
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Availabe features of Mobile IPv6 in OPNET

• Supported Mobility Features
• Route optimization
• Mobile node (MN)home agent (HA) bi-directional
  tunneling
• Available IPv6 extension headers
• Mobility extension headers
• Routing (type 2) and destination option extension
  headers

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WLAN-3G intworking in OPNET

• New nodes to build
• Dual mode User Equipment (UE)
• AAA Server
• Wireless Access Gateway (WAG)
• Packet Data Gateway (PDG)

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WLAN-3G intworking in OPNET

• New interfaces to add
• Ww - Interface between the UE and the WLAN Access
  Network
• Wn - Interface between the WLAN Access Network
  and the WAG.
• Wp - Interface between the WAG and PDG.
• Wm Interface between point is located between
  3GPP AAA Server and PDDG

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Other additions to OPNET

• Fast Mobile IPv6 extensions to the existing
  Mobile IPv6.
• Node to execute the HO Algorithms.

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Future Plans (current project year)

• OPNET simulation for validation
• Choose parameters for prediction based on
  extensive simulation
• Measure prediction accuracy
• Update prediction algorithm

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Future Plans (after current project)

• Can we generalize to HO between any RAT and any
  RAT?

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REFERENCES

• 3gPP TS23.234 v 6.4.0, 3GPP system to Wireless
  Local Area Network interworking system
  description 3GPP specifications.
• 3gPP TS22.934 v 6.4.0, Feasibility study on 3GPP
  system to Wireless Local Area Network
  interworking. 3GPP specifications.
• ETSI TR 101 957
• A.K. Salkintzis, C. Fors, and R. Pazhyannur.
  WLAN-GPRS Integration for Next-Generation Mobile
  Data Networks, IEEE Wireless Communication, pp.
  112-124, October, 2002.
• S. Taso and C. Lin, Design and Evaluation of
  UMTS-WLAN Interworking. Strategies, IEEE VTC
  2002 Fall, vol. 2, pp. 777-781, Sep. 2002
• Lott et al. Interworking of WLAN and 3G
  systems. Communications, IEE Proceedings- Volume
  151,  Issue 5,  24 Oct. 2004 Page(s)507 513
• K. Pahlavan et al., Handoff in Hybrid Mobile
  Data Networks IEEE Pers. Commun., Apr. 2000.
• Leeuwen et al. Location assisted fast vertical
  handover for UMTS/WLAN overlay networks
  International conference on wired/wireless
  internet communications (WWIC) 2005.