N k d R T A Network-Assisted Inter-RAT Handover SchemeHandover Scheme

Sangheon Pack (Korea University)25 August 200925 August 2009

Heterogeneous Wireless NetworksHeterogeneous Wireless NetworksBilling VHE

Signalling Gateway

WAP Accounting ISP

SIP Proxy Server

Internet

P

IP backbone

Satellite FES

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Broadcast Networks(DVB-T, DMB)

GSM / GPRS

UMTS

G S

IP-based micro-mobility Wireless

LANs

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Case Study: 3G-WLAN VHO (1/2)Case Study: 3G-WLAN VHO (1/2)

NWLANLow cost, high data rate, small coverageDesigned for low terminal velocity (non-contiguous spots)Office, Stations, Department store, Subway etc.

3G Cellular NetworkHigh cost, medium data rate, large coverageEven a fast moving vehicle can use on-line gbrowser

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Case Study: 3G-WLAN VHO (2/2)Case Study: 3G-WLAN VHO (2/2)

3G WLANData rate < 2Mbps < 11MbpsRange 3-5 Km 50-60 mHandover Yes LimitedSecurity High Low (being improved)C Wid H Coverage Wide area

(continuous)Hot spots (non continuous)

Mobility High speed Stationary NomadicMobility High speed Stationary, NomadicService Voice and data Primarily data

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Related Works (1/2)Related Works (1/2)N k k di h d Numerous works on network discovery, handover decision/execution

[1] Wengui Zhang “Handover Decision Using Fuzzy MADM in [1] Wengui Zhang, Handover Decision Using Fuzzy MADM in Heterogeneous Networks,” in Proc. IEEE WCNC 2004.[2] A. Hasswa et al. “Generic Vertical Handoff Decision Function for Heterogeneous Wireless Networks ” in Proc IEEE WOCN 2005Heterogeneous Wireless Networks, in Proc. IEEE WOCN 2005.[3] R. Tawil, O. Salazar and G. Pujolle, “Vertical Handoff Decision Scheme Using MAMD for Wireless Networks,” in Proc. IEEE WCNC 20082008.[4] W. Ying et al., “Vertical Handover Decision in an Enhanced Media Independent Handover Framework,” in Proc. IEEE WCNC 2008.[5] E. Stevens et al., “An MDP-Based Vertical Handoff Decision Algorithm for Heterogeneous Wireless Networks,” IEEE Trans. Vehicular, March 2008.[6] F. Zhu and J. McNair, “Optimizations for Vertical Handoff Decision Algorithms,” in Proc. IEEE WCNC 2004.

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Related Works (2/2)Related Works (2/2)

H d d d d H Handover decision: depending on VHO criteriaChannel condition is a key criteria for VHO

Price Bandwidth Channel condition

Sojourn time

Power Security User preference

[1] O O O O O X X[1] O O O O O X X[2] O O O X O O O

[3,4] O O O X X X X[5,6] X O O X X X X

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MotivationMotivation

h l d bl b Channel scanning is indispensible to obtain channel conditions; However, channel

l d f l !scanning leads to significant latency!In WLANs, scanning latency is about 200-300

!msec!How to reduce channel scanning latency in VHO?

IEEE 802.21 MIH provides useful information via Information Server (IS)Exploit temporal and spatial locality in IS!

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MIH Services (1/3)MIH Services (1/3)

E ( d d d E )MIES (Media Independant Event Service)Link up/down, link parameters change, link going down, link event rollback

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MIH Services (2/3)MIH Services (2/3)

( d d d d )MICS (Media Independant Command Service)MIH Scan, MIH Configure

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MIH Services (3/3)MIH Services (3/3)

( d d d f MIIS (Media Independant Information Service)

Discover and obtain neighboring network information within a geographic region

h h k l- Communicate with neighboring network elements- Query/response mechanism: neighboring network

id d t MAC dd f names, providers and cost, MAC addresses of neighboring network elements, channel information, security QoS security, QoS, ...

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Spatial LocalitySpatial Locality

Information SServer

Collaborative channelchannel scanning

Me!A

11B

Temporal LocalityTemporal Locality

Information SServer

Collaborative channel scanning

Me!A at T B at T-Δ

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System Model (1/2)System Model (1/2)

DB h h d (E )DB Schema in enhanced IS (EIS)Extended channel state information (ECSI)

• ( )( ), , , , id t x y δ

Access point identification,Measurement time,

idt

( )Measurement location,Signal-to-noise ratio (SNR),

( ),x yδ

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System Model (2/2)System Model (2/2)

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Each MN should notify the ECSI to EIS

Estimating the SNR (1/2)Estimating the SNR (1/2)

Temporal LocalityTemporal Locality

Spatial Locality

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Estimating the SNR (2/2)Estimating the SNR (2/2)

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Exising IEEE 802 21 VHOExising IEEE 802.21 VHOMobile node IS

Mobile WiMAX PoAHSDPA PoA

Mobile node

Handover trigger

Neighbor list queryNeighbor list query

Neighbor list response ( HSDPA PoA, Mobile WiMAX PoA )

scanning

scanning late

ncy

Network selection Han

dove

r

Target list query (with the results of scanning)

Target list response ( Mobile WiMAX PoA > HSDPA PoA )

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Vertical handover to Mobile WiMAX PoAHandover to Mobile WiMAX PoA

Proposed IEEE 802 21 VHOProposed IEEE 802.21 VHO

( )( )ECSI id t δ( )( ), , , , ECSI id t x y δ

( )( ), , , , ECSI id t x y δ( )( ), , , , ECSI id t x y δ

( )( )( )0 0 0, , x y t

r lat

ency

Han

dove

Handover to Mobile WiMAX PoA

18Handover to other PoAs for handover failures

Simulation EnvironmentSimulation Environment

l h l d lWireless channel modelCOST-231 Hata model

Mobility modelyRandom way-point mobility model

Heterogeneous network modelHSDPA + Mobile WiMAX + WiFiHSDPA + Mobile WiMAX + WiFi

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Simulation Results (1/4)Simulation Results (1/4)

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Hit: PoA by the proposed scheme = PoA by full scanning procedure

Simulation Results (2/4)Simulation Results (2/4)

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Simulation Results (3/4)Simulation Results (3/4)

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There is optimal for minimizing VHO delayMR

Simulation Results (4/4) ( WiFi P A)Simulation Results (4/4) ( + WiFi PoA)

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Optimal is dependent on the smallest network coverage in heterogeneous networks

MR

ConclusionConclusion

Network assistance and collaboration are important mpin mobile Internet!

To achieve seamless inter-RAT handovermOptimization techniques are needed

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