a methodology for mobile ip evaluation at california capital corridor inter-city rail

8/3/2019 A Methodology for Mobile IP Evaluation at California Capital Corridor Inter-City Rail

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A Methodology for Mobile IP Evaluation at California Capital

Corridor Inter-City Rail

Kazuhiro Yamada1*, Harsh Verma2, Bensen Chiou1,

Jean-Luc Ygnace3, Hamed Benouar1

1 California Center for Innovative Transportation, UC Berkeley, USA

2105 Bancroft Way, Berkeley CA 94720

Tel: +1(510)642-5082, E-mail: [email protected]

http://www.calccit.org

2 GLOCOL Inc, USA

3 INRETS, France

ABSTRACT

This paper presents the methodology for Mobile IP Trial Evaluation at Californias Capital

Corridor Inter-City Rail project [1] [2]. The goal of the project is to pursue Pilot

Demonstrations to provide Wireless LAN, High speed Internet connectivity and Info-centric

Services on trains and this started with an initial co-operation in Californias Capitol

Corridors AMTRAK service subsidized by California Department of Transportation

(Caltrans) managed by the Capitol Corridor Joint Powers Authority with similar efforts at

SNCF in France and co-operation between French technology center of excellence INRETS,

GLOCOL USA and the University of California (Berkeley). The Trains Connected

Partnership Project Work Group was set up to focus on emerging standards, technologies andevaluations which have received interest from various Rail Authorities. The focus is to

understand the best ways to incorporate satellite communication, Wi-Fi, Wi-Max, Mobile IP

and various promising technologies into broader applications such as passenger service, train

operations, safety and security. This paper reports seamless roaming simulations over

different systems using Mobile IP.

INTRODUCTION

During the next five to ten years, most rail system riders in North America and Europe are

expected to have onboard wireless Internet access (Wi-Fi), according to some industryestimates. Currently, there are many applications in these regions, mostly in the pilot stages.

A few services are offered on a commercial basis in the U.K, - GNER (Great North East

Railway) [3], Virgin Trains from London to Birmingham, Manchester and Glasgow [4], and

Southerns Brighton Express [5], in Northern Europe countries and also between Paris and

Brussels on the Thalys high speed trains [6]. In India the service is also offered by Railtel on

Delhi-Amritsar and Delhi-Bhopal train routes [7]. Similar services are used by train riders in

Canada and in the U.S.

The most promising solution today is probably the satellite communication systems because

there is no need for specific infrastructure along the track to provide the service almost

everywhere even in remote areas. The main drawbacks to guarantee connectivity and QoS are
mailto:[email protected]://www.calccit.org/mailto:[email protected]://www.calccit.org/


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due to the satellite visibility due to the occurrence of mask effects related to the specific

railways environments (tunnels, cutting, lattice mast supporting the catenaries, etc).

In order to overcome this deficiency, this paper focuses on the combination system of a

satellite access and discontinuous terrestrial networks which have to be divided into several

sub-networks. The largest difference from the system with only one satellite is the system hasmany different sub-networks along the track. Trains have to go across these networks as they

go. To change sub-networks on the way, they have to seamlessly roam from one sub-network

to another. This paper reports seamless roaming simulations for the mobile environment.

RELEVANCE OF THE PROJECT

The project is part of the CALFRANCE transportation research cooperation agreement

between France and California. It involves a public/private partnership to dramatically

increase the attractiveness of train passenger transportation in both areas and to speed up the

market deployment of passenger services by solving major technological barriers in the fieldof internet connectivity and telecommunication. The partnership is organized with global

industry players from both countries, major train operators, outstanding academic teams and

supported by DOTs who are really concerned by the economic viability of the train passenger

transportation sector.

Providing new services is essential to make railway transport more attractive. New services

making the distances seem shorter and the train journeys more pleasant and efficient is a

favorable way of attracting new travelers to trains which is one of the best transportation

systems for conservation of natural resources and protection of environment.

STATEMENT OF WORK

This task covers the technical side of the project. This task intends to conduct simulations and

demonstrations to provide WirelessLAN, Internet connectivity and Info-centric services on

Capitol Corridor in California using a terrestrial network system instead of a satellite

communication. In order to achieve the seamless handover Mobile IP was employed. It is a

world standard technology by IETF, Internet Engineering Task Force, and any devices which

support IP can support Mobile IP. To take Mobile IP into the Wi-Fi on trains system, Mobile

IP has to be optimized to roam seamlessly even faster. This paper introduces first how to

optimize Mobile IP to have it roam faster and then shows some trials and their results.

MOBILE IP FASTER ROAMING

Mobile IP allows entire networks and their subnets to be mobile and maintain all IP

connectivity, transparent to the IP hosts connecting through the network. In IP networks,

routing is based on stationary IP addresses. A device on a network is reachable through

normal IP routing by the IP address which is assigned on the network. A device sitting on a

network inside a moving medium such as an automobile, bus or train, as it roams away from

its home network, is no longer reachable by using normal IP routing. This results in the active

sessions of the device being terminated. Mobile IP enables users to keep the same IP addresswhile traveling to a different network, ensuring that a roaming individual can continue


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communication without sessions or connections being dropped.

Mobile IP, however, takes several seconds to complete a roaming. In order to apply Mobile

IP to transportation systems, the roaming time has to be reduced. In a roaming process, after

Mobile Router, or MR, moves to a new network, it has to wait for a periodical advertisement

from a Foreign Agent, or FA, to detect the movement. A Mobile Router does not start theregistration process until it detects the movement. In order to make a roaming faster this

waiting time has to be reduced.

SNMP version 3 linkup/linkdown traps can be used to reduce the waiting time. SNMPv3

linkup/linkdown traps can watch the interface condition on a Mobile Router. When the

wireless interface finds a new radio signal and comes up, the trap informs the Mobile Router

and then it solicits an advertisement to the Foreign Agent which is on the back of the wireless

connection. Figure 1 shows the roaming process time with and without SNMPv3 traps. In the

case without SNMPv3 traps, default case, the waiting time for the next advertisement is

3,460ms under the condition of every five seconds of the advertisement interval. In the case

with SNMPv3 traps the waiting time is just 20ms. At the same time when the wirelessinterface linkups the SNMPv3 trap tells the Mobile Router of the information and it solicits

an advertisement. The waiting time for 20ms starts with the solicitation leaving the Mobile

Router, or the wireless interface linkups, and ends with an advertisement from the Foreign

Agent arriving at the Mobile Router. The SNMPv3 trap dramatically reduced the mobile ip

roaming process time. This feature was used in the following Mobile Environment

Simulations.

Figure 1 Mobile IP Roaming Process with SNMPv3 trap

MOBILE ENVIRNMENT SIMULATIONS SYSTEM

The network topology which was set up for the simulations is shown in figure 2. Three

Foreign Agents are set up. One of them is wirelessly connected with the Home Agent. The

Mobile Router has a Mobile Network which includes PCs and an IP camera. In order to

access to the IP camera, a static private IP address is allocated to it and the address is

statically translated to a static global IP address at the Home Agent. IP addresses shown in

figure 1 are used for the simulation in a laboratory. They should be properly re-configured to

each network environment in each simulation.


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Figure 2 Network Topology for the Simulations

SIMULATION IN A LABORATORY

In this phase of the simulation mobile network was tested in the moving environment at

walking speed. Three Foreign Agents were installed far apart from each other, located at

three corners in CCIT, California Center for Innovative Transportation (See figure 3). The

Mobile Router was carried by foot within CCIT first and a video from the IP camera which is

attached to the Mobile Router was monitored from outside the mobile IP network through the

internet. Continuous pings from a PC outside mobile IP network to the IP camera were issued

and monitored.

Figure 3 Laboratory Test 1


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When the Mobile Router was in the close vicinity of one of the Foreign Agents, pings and the

video from the IP camera were stable. At the moment the Mobile Router moved from one

Foreign Agent to another, one or two pings were lost in many cases. No ping was lost in the

best case. Even in the best case, however, the video froze for about a second. The time delays

associated with the handover include two components first, the association time for Bridges

to associate and second, the Mobile IP process time. It was observed that the time delay ofthe interface linkdown/up was 500ms, while the Mobile IP process time was reduced by the

SNMPv3 traps to 48ms.The sum of both time delays add up to 548ms. Pings are the burst

data which are sent every one second. This interval sometimes enables pings to avoid their

loss by chance. On the other hand video is a streaming data which is sent continuously. Video

data can not avoid its loss while Mobile IP is processing. Video is also an application which

takes a little bit longer time to establish a connection than ping which is ICMP message. This

might have made the latency longer. Even though Mobile IP is employed, a short isolated

time is unavoidable. It is mandated to use middleware which controls delay and jitter to make

video or VoIP smooth.

For the second step the Mobile Router was taken outside CCIT. In this case two ForeignAgents, FA1 and FA2 in the figure 3, worked as an agent. FA1 and FA2 were set up just next

to windows and they made their coverage area outside CCIT (See figure 4). The results were

the same as an in-CCIT test.

Figure 4 Laboratory Test 2

SIMULATION IN A CAR ENVIRNMENT

In this phase of the test mobile network was tested in the moving environment at car speed.

The ground system such as FAs and BRs were set up on the Richmond campus for PATH

(California Partners for Advanced Transit and Highways) (See figure 5). The Mobile Router

was installed in a car which was moving on a street at 25mph. The PC in the building 180

issued continuous pings and monitored the video from the IP camera on a car. The car was

repeatedly traveling on the street back to forth. The ping turn around time was measured on

the way.


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Figure 5 Test system

Results

The result was the same as the one from the lab test. Mobile IP supported the seamless

roaming. Figure 6 shows the ping turn around time. The x-axis of the graph shows the

number of the pings and the numbers themselves do not link to anything such as the distance.

The x signs on the graph show No ping reply. There are two humps around ping number

is 50 and 110. They are roaming points. The Mobile router on the car which came from left in

the figure 5 roamed from Foreign Agent 3 to Foreign Agent 1 around ping number is 50 and

also roamed from Foreign Agent 1to Foreign Agent 2 around ping number is 110. Therefore

this result shows that the car speed does not affect mobile IP at all.

Figure 6 shows one more interesting result. The ping turn around time gradually goes up just

before the handover and suddenly comes down and stable in both cases. This is because of

Wi-Fi default specifications. Once Wi-Fi gets associated with one of the access points, it

persists in the connection until it loses the connection due to a reason such as going out of the

radio range even if it sees another better connection. In this trail as the Mobile Router on the

car goes right, the radio intension deteriorates. This caused the longer ping turn around time,

as it went right. It went far right, it eventually lost the connection to the Foreign Agent 3

because it went out of the range of the bridge attached to the Foreign Agent 3. Just after thisdisconnection the Mobile Router saw a strong radio from the bridge attached to Foreign

Agent 1, and then it connected to the agent. The strong wireless connection to Foreign Agent

1 provided the Mobile Router with the stable communication to the internet. This was why

the ping turn around time got short and stable just after the handover.

This result shows that the ping turn around time before the handover can be reduced (the

handover can be finished before the time gets longer) if wi-fi is optimized to choose the most

suitable bridge to be associated with. This must make the roaming performance even better.


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0

500

1000

1500

2000

Figure 6 Ping Turn around Time

CONCLUSION

SNMPv3 trap reduced Mobile IP handover process time (waiting time for the next

advertisement) from 3,460ms under the condition of every five seconds of advertisement

interval to 20ms and Mobile IP worked well.

The simulation environment provided an excellent test-bed to identify issues and concerns as

a phased testing, installation and deployment could be considered. The results in a car

environment simulation show Mobile IP itself can be applied to transportation systems. On

the other hand they also show the optimization of Mobile IP is not all needed. Mobile IP

works on the Layer-three which does not work without the Layer-two connection. In order to

make the performance in the figure 6 even better layer-two technology must be customized tochoose the most suitable bridge to be associated with. After the optimization of layer-two, the

layer-four connection will also have to be customized. The other Layer connections also must

be optimized at the next step.

REFERENCE

[1] Verma, H, Ygnace, J.L., Benouar, H, Trains Connected Project, ITS World Congress at

Nagoya Japan, October 2004.

[2] CalFrance consortium, Trains Connected; Internet on rails and beyond to improve thefuture of transportation. Proposal submitted to the California Dot and the French Dot,

November 2004.

[3] http://www.icomera.com/customers_case_studies_gner.asp

[4] http://www.wi-fiplanet.com/columns/article.php/3486706

[5] http://www.techworld.com/mobility/features/index.cfm?FeatureID=1351

[6] http://www.thalys.com/be/en/wi-fi/overview

[7] http://newswww.bbc.net.uk/1/hi/business/3835525.stm

xxx x

Ping turn around time (ms)
http://www.icomera.com/customers_case_studies_gner.asphttp://www.icomera.com/customers_case_studies_gner.asphttp://www.wi-fiplanet.com/columns/article.php/3486706http://www.techworld.com/mobility/features/index.cfm?FeatureID=1351http://www.thalys.com/be/en/wi-fi/overviewhttp://newswww.bbc.net.uk/1/hi/business/3835525.stmhttp://www.icomera.com/customers_case_studies_gner.asphttp://www.wi-fiplanet.com/columns/article.php/3486706http://www.techworld.com/mobility/features/index.cfm?FeatureID=1351http://www.thalys.com/be/en/wi-fi/overviewhttp://newswww.bbc.net.uk/1/hi/business/3835525.stm

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