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Tetsuya Arita and Fumio Teraoka

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1 A Fast Handover Mechanism Using Cross-Layer Collaboration for Mobile Networks in High-Speed Trains
Tetsuya Arita and Fumio Teraoka Graduate School of Science and Technology, Keio University, Japan

2 Introduction High-Speed Trains Passengers Business
Spend long hours on a train Less transfer Can’t use all applications because of narrowband Business Demands for monitoring the train using video streaming

3 The Goal of this Research
To provide the communication environment faster than 1 Gbps to High-speed train There are three requirements for the goal Communication Speed The current wireless LAN technologies (WiFi and WiMAX) cannot satisfy this requirement Session Continuity Fast Handover Mechanism

4 Communication Speed over 1Gbps
Infrared Comm. Device (IR-CD) has been developed by Prof. Shinichiro Haruyama* and Railway Technical Research Institute * Graduate School of System Design and Management, Keio University Front view Rear view Infrared laser Serial Interface Beacon Ethernet Interface SPEC Speed : 1.25 Gbps Range : 360m Feature : Directional Power cable Power Switch Receive Level

5 Session Continuity Network Mobility (NEMO) Basic Support [RFC3936]
The network mobility protocol in IPv6 Mobile Router (MR) executes handovers and provides mobile node with mobility-transparent connectivity Home Agent (HA) manages the binding of Home Address (HoA) and Care-of Address (CoA) Home network (4) Communication HoA Correspondent Node MR HA Mobile network (3) Foreign Network CoA (2) Mobile network (1) Movement MR (2) Register CoA and MNP with HA (3) IPv6–in IPv6 tunnel

6 Fast Handover Mechanism
Conventional Handover Procedure takes more than 1 sec 1. Waiting for receiving Router Advertisement (RA) message 2. The Duplicate Address Detection (DAD) procedure new AR HA (4) RA (6)BU (7)BA (3) wait for RA (5) DAD Network Layer Mobile Node Total disruption time (more than 1 sec) Link Layer (1) comm. quality getting worse (2) L2 handover BU : Binding Update message BA : Binding Acknowledgement message

7 L3-Driven Fast Handover
L3-Driven Fast Handover [RFC5184] Developed in our laboratory Using cross-layer collaboration We defined link layer primitives new AR HA (8)BU (9)BA (4) pre-DAD Network Layer (2) L2-LinkStatus Changed (3) L2-PoAList (7) L2-LinkUp (5) L2-Link Connect Mobile Node Total disruption time (10-15 ms) Link Layer (1) comm. quality getting worse (6) L2 handover

8 Proposal: Fast Handover Mechanism For the IR-CD
Eliminating DAD processing Time DAD process In case of WiFi It is possible to predict handovers by Receive Signal Strength Indicator Execute DAD before handovers In case of IR-CD It is impossible to predict handovers Cannot execute DAD before handover Single administration organization A Railway company Assign each mobile router a unique interface identifier Therefore, the proposed mechanism disables DAD processing In case of WiFi, execute DAD before handover It is possible to predict handover by RSSI In case of IR-CD, it is impossible to execute DAD before handover

9 Proposal: Fast Handover Mechanism For the IR-CD
Eliminating Waiting Time to Detect Link Layer Handover In case of IR-CD MR and IR-CD are connected by Ethernet cable Link state between MR and IR-CD is always LinkUp state IR-CD is regarded as a repeater Connect IR-CD to MR with Data cable and Control cable Control cable can notify MR of the infrared link state (LinkUp/LinkDown) L3-Deriven Fast Handover Notification of L2-LinkUp WiFi device can detect the link status Infrared Comm. Device on the train Infrared Comm. Device on the ground Data cable(1 Gbps) Infrared Laser LinkUp/LinkDown Control cable Train

10 Proposal: Fast Handover Mechanism For the IR-CD
The Proposed Procedure new AR HA (5) RS (6) RA (7) BU (8) BA Network Layer (2) L2-Linkdown (4) L2-Linkup Mobile Router Total disruption time Link Layer (1) Linkdown frame (3) Linkup frame Infrared communication device

11 Implementation Environment OS : NetBSD 4.99 SHISA
An implementation of Mobile IPv6 and NEMO BS on NetBSD fhod (fast handover daemon) on NetBSD Daemon to achieve fast handover fhod mrd nemonetd Mobility Socket Routing Socket kernel userland Binding Update Database Destination Options header module Management Neighbor Discovery Address Routing table Routing table Tunneling Forwarding Our implementation Module diagram of our implementation based on SHISA

12 Message Flow Message Flow in L3 Handover tunnel Train MR IR-CD fhod
mrd nemonetd Prev. AR new AR HA Link disconnected (1)Linkdown Link connected (3)Linkup (5) RS (6) RA (7) BU (8) BA Tunnel estab. tunnel

13 Evaluation – Handover Time -
Test network Emulate the train environment IR-CD MR AR HA 1.7 msec 0.3 msec 4.0 msec train ground 0.003msec Linkup RS RA BU BA Details of Handover Time router HA CN AR-1 AR-2 無線環境エミュレータにスクリプト読ませてる図 列車の走行をエミュレートしている 本研究室で開発したを明記 scenario Wireless Environment Emulator MR Data cable Control cable CN: Correspondent Node LFN: Local Fixed Node LFN

14 Evaluation – Packet Loss Ratio -
configuration 10 IR-CDs are connected to a single AR a handover occurs per 5 seconds A train runs at 300km/h and IR-CD is installed every 420m a L3 Handover occurs in 10 handovers packet loss never occurs on the infrared link L2 handover time 10ms, 50ms, 100ms RTT between MR and HA 0 – 30 ms UDP packet were sent form CN to MR at 1 Mbps ハンドオヴぁ時間の単位 仮に100msでも Even in the worst case, The average packet loss ratio is about 2%.

15 Conclusion The goal of this research
To provide the mobile network in high-speed train with high-speed connectivity (more than 1 Gbps) We proposed a fast handover mechanism Using cross-layer collaboration for mobile network installed in High- speed train Defined the Linkup control frame MR can immediately start handover procedure The measurements show that handover time is approximately 6.0ms + L2 handover time packet loss ratio is approximately 2 % in the worst case.

16 Thank you for your attention.

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