Hotspot Networks on a Train - MikroTik

© 2007 Boingo Wireless, Inc. – Confidential –

Hotspot Networks on a Train

June 1st, 2007 (Good Morning!)

Brian Vargyas, Director of Network Engineering

http://mum.mikrotik.com/2007/US/


Overview

Who is Boingo?

Why The Interest In Trains

Design Phase

Construction Phase

Testing Phase

Conclusion


Who is Boingo?


We are….

Wireless neutral-host provider since 1997 with 103

employees and offices in Chicago, Dallas, New York and

Los Angeles.

Industry leader in turnkey cellular/Wi-Fi with 30% market

share of total 1.17M enplanements daily across 12

airports.

Roaming relationships with top WISPs covering over 70

airports in North America and over 60,000 hotspots

worldwide.


We’re net neutral

Allows for seamless integration of

WISPs

Shows dedication to serve

passengers, airport authoritys,

airlines and now railroads!

Maximizes network use and income

potential


Why the interest in trains?


Great Target Market

Commuter trains have a great captive audience.

Provides an extension of the workplace – allows

you to complete work you didn’t get done in the

office.

Some have connectors into airports

Commute times are usually between 30 minutes

to 1 ½ hours -- long enough to break out that

laptop or handheld WiFi PDA.


Ideal Ridership - NICTD

NICTD – Northern Indiana Commuter

Transportation District

Train line connects from South Bend, Indiana to

Chicago downtown. Picks up Notre Dame

university students.

14,300 passengers ride each day

Over 4 million unique passengers each year

Average rider age 42, has a college degree and

makes $50k/year


NICTD Ideal because…

They own most all of their own track network

from South Chicago to South Bend.

Have installed their own fiber optic backbone

along the tracks for a new signaling system with

spare fiber available for other uses such as WiFi

Have power available trackside for wireless

equipment (It’s an electric train line)

Poles are spaced evenly for overhead wires

which work well for mounting wireless

equipment


The Track Network - Side Revenue

Provides WiFi service on train platforms while

waiting for the train

Provides limited WiFi coverage near the track

line for business and residential access

High bandwidth video on train cars for real time

monitoring and homeland security applications

Railroad gate crossing remote video monitoring

and enforcement

Daily rail inspections and first responder rail

disaster site evaluation information


Design Phase


For this trial….

We needed to design for the fastest train

speeds which were around 75mph

Wanted to incorporate two stations to provide

waiting passenger WiFi access

Wanted to understand AP placement and how

often we needed to regenerate signal from the

fiber vs. using mesh to carry the signal.

Chose 7 miles of test track between Ogden

Dunes and Dune Park

Total train line is approx 75 miles


Determining track spacing of AP’s


Drive until we loose it!


Pole Placement


Route of test track


For the track network….

Factoring in fade margin, the spacing between

poles at 5Ghz was about 4 tenths of a mile with

modifications for turns, grade changes and

bridges.

We needed 18 AP’s for our 7 miles of track or

approximately 180 AP’s for the entire route.

Every 3 AP’s we would regenerate the signal off

of the backbone fiber


For the train car…..

Stainless steel exterior

and lots of metal to

overcome

Height of the car around

17 feet, just below

trackside network

antenna height of 19

feet

Will need a AP inside

the car for local clients


Construction Phase


Special hardware was developed

Mikrotik outdoor enclosures modified with 5Ghz

panel antennas on both sides so signal would

run down the track in both directions

DSS Satellite mount was used off the pole so it

could swing away if overhead wire work was

necessary

Special bracket for DSS mount to allow for

curved wooden telephone pole mounting made

Stainless steel enclosures & grounding required


Fiber Backbone Node


Antenna Arm


Mikrotik Configuration Used

Routerboard 532a with two ubiquiti SR5 cards,

each one feeding a separate panel, estimated

output power at 35db, using fixed frequency

PoE injection via shielded Cat5e cables

Turned off CPU resource saving to keep from

equipment freezing due to lake effect snow and

blowing cold wind (0 Degree F in area at times)

Running 2.9.40 and WDS bridging using RSTP

Dude Server monitoring the network


Layer 2 Rapid Spanning Tree

The RSTP was chosen because it allowed for

fast convergence of the train car onto the

backbone network and kept us loop free

Used 8 port 2940 Cisco switches at fiber

locations running RSTP

Head end routerboard was the master and had

highest priority

Had to adjust RSTP weights because Cisco

used different values then Mikrotik


Trackside Network Topology


Remote Power

We hung 2kw (smallest available) transformers

on polls connected to 2400VAC overhead lines

Disconnect switches were installed for 120VAC

and 2400VAC per national electric code

Looked into solar power for wireless mesh

nodes (4-10W) – however trees on south side of

tracks were blocking sunlight in many areas.

Ultimately solar power is cheaper then

transformers due to labor costs to hang them

and service them.


Train Car Hotspot

Routerboard 532 feeding an indoor 2.4Ghz

antenna.

On-train voltage varied, but was mostly 72Vdc

and was always on (due to batteries)

We used a rail certified DC-DC power supply

from ABSOPULSE to convert down to 12Vdc

Indoor Routerboard feeds outdoor one

connected to 5Ghz omni antenna. It was done

this way to minimize 5Ghz loss.


Train Car Hotspot Topology


Train Car Hotspot on plywood


On the roof of car #15


A better antenna would have been…

Huber + Suhner Sencity

rail antenna at 5Ghz with

two 13dbi directional

patch antennas built in.


Testing Phase


Developing the plan

Needed to understand latency

Packet Loss Measurement

How quick handoff’s occurred between AP’s

Did web surfing feel “normal”

Hotspot Authentication on or off train?


The Drive Test

Drove alongside the tracks with an omni

antenna on top of a truck

Watched registration table for handoffs

Had to use connect-list to set the minimum

connect level on client (-85db)

When using RB112, it was not fast enough to

handle the WDS RSTP handoffs --- ended up

using a RB532


Drive Test Results

Lost connections when we were NLOS because

roadway veered away from tracks at times

During LOS, we maintained connectivity to at

least 2-3 AP’s at a time, with seamless handoffs.

Ping times varied from 3-4ms up to 800ms

depending how hard the handoff was.

Speeds were 700kbps under worst conditions

up to 6-8Mbps when near a fiber node

Drove anywhere from 20mph to 80mph. As

speed increased, data decreased.


Train test

Had to ride the train from Michigan City to

Chicago --- Only had 10 minutes for testing for a

1 Hour ride!

Signal coverage was excellent throughout the

car and even penetrated the neighboring car

Hotspot pages local, so quick response when

logging in

Was able to get connected to more AP’s then

drive test due to LOS along the track.


Train test cont….

Neighboring freight train on siding caused

signal drops due to reflections of steel cars and

AP being between tracks rather then above it

Saw similar ping times and speeds as with drive

test

As speed increased the registration time to

acquire trackside AP’s increased.

Overall, web surfing felt like you were

connected to a WAN vs LAN, but worked fine.


What might have helped results

Diversity antenna’s

Using directional antenna’s instead of omni

Using RouterOS 3 WDS mesh mode instead of

RouterOS 2.9 WDS non-mesh aware mode

Locking the radio speeds at 24Mbps or even

6Mbps


Conclusion


Definitely worth investigating….

The trial proved it’s possible to provide WiFi

service on the train

Need to improve on the efficiency in which each

trackside node is installed

Need to reduce the number of fiber nodes to

reduce costs in doing fiber taps and trenching

Increasing the height of nodes to further

improve signal quality and reduce reflections

Hotspot Networks on a Train - MikroTik

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