Trainsense presentation

1. Fakultät Informatik – Institut für Systemarchitektur – Professur Rechnernetze
TrainSense:
A Novel Infrastructure to Support
Mobility in Wireless Sensor Networks
Presenter: Martin Rataj
Supervisor: Dr.-Ing. habil. Waltenegus Dargie
Chair of Computer Networks
TU Dresden
H. Smeets, Ch. I. Shih, M. Zuniga, T. Hagemeier, P. J. Marrón

2. Outline
1. Motivation for Mobility
2. Core Idea of TrainSense
3. Interesting Features
4. Practical Applications
5. Related Work
Folie 1

3. Mobility in WSN
Motivation
• To increase the
communication capacity
• To enhance sensing
coverage
• To facilitate network
deployment
Challenges
• Specification of the speed
and direction of each node
• Node tracking / positioning
• Reliable source of energy
• Automatic reprogramming
• Path scheduling
• Energy budgets
Folie 2

4. Concept of TrainSense
• Designed as a testing environment
• Wireless nodes are integrated with model trains
• Model train infrastructure provides many advantages
• The existing infrastructure needs adjustments to
provide:
• Real-time train control
• Precise positioning
• Energy management
• Automatic train-mote
operations
• Back-channel information
Folie 3

5. Model Train Components
• Host computer – user friendly interface to
communicate with the controller
• Controller – controls speed and direction of trains,
control of turnouts
• Detector – detects when a train reaches a certain point
and informs the controller of this fact
• Tracks – carry power and data
• Locomotives with their decoders
Folie 4

6. Contribution of Trainsense
• Adjustments to HW and SW of the controller
• New software for the host computer
• Locomotives equipped with TrainSense motes
• Host mote – communication to other motes
• USB docking station
Folie 5
Fig. 1:TrainSense mote Fig. 2: TrainSense architecture

7. Modified controller
• As opposed to the commercial standard, it provides
real-time guarantees
– Change train speed commands
– Switch turnouts
– Trigger fired upon position detection
• Based on the Maerklin/Motorola standard
– Can address up to 80 trains and 256 turnouts
– Packets contain speed information or direction commands for
trains and switch commands for turnouts
Folie 6

8. Positioning techniques
• Position detection is based on a short circuit between
the two rails, created by the wheels of the train
• Detectors store the position in a register, which is
periodically polled by the controller
• Two techniques – Dead reckoning and Dead start
• The train is expected to move at a constant speed
1) Dead reckoning
• Introduces cumulative errors – needs calibration
Folie 7
Node crosses
a detector on
position x
Wait for x’/s
seconds
Send a “stop”
packet to the
train
The position
of the node is
x+x’

9. Positioning techniques
2) Dead start
• The train starts from a still position
• Used if the train can not reach the nominal speed
before encountering the first detector
Folie 8
Fig. 3: Dead reckoning Fig. 4: Dead reckoning vs. Dead start

10. Energy management
• For long can the power supply
provide power on an outage?
• First, the golden capacitors
are charged for one minute
• RSSI of packets sent at min.
and max. power levels (-
20dBm and 0dBm)
• Distance between motes: 2 m
• Need to convert ±18V to 5V DC – an AC/DC converter
is embedded in the on-board power supply unit
• The motes are powered through their USB interface
• Dirty tracks can cause short power outages – the power
supply needs to be robust
Folie 9
Fig. 5: Power disconnection experiment

11. USB Docking station
• For re-programming and data download
• The trains are not powerful enough to dock into
regular USB ports – custom USB docking station
• 97% of effectiveness of the regular USB port (based on
an experiment)
Folie 10
Fig. 6: USB Docking Station

12. Electromagnetic interference
• Moving trains or turnout changes can cause an
interference to the radio communication
• 4 modes, noise floor is measured at 2 kHz
1) Baseline mode – Tracks are powered with 18V DC, no
interference
2) Heavy traffic – The controller sends a continuous
stream of packets
3) Frequent turnout changes – Turnouts switched back
and forth as fast as possible
4) Dirty tracks – Power on/off every second
Folie 11

13. Interference - results
• Measurement at 2 kHz may not capture all noise
• For example, the coils of the turnouts generate
pulses in the order of milliseconds
• Theory: Instead of increasing the sampling rate,
measure PRR
Folie 12
Fig. 7: Noise floor for the various modes Fig. 8: Packet Reception Rates

14. Practical Application
Self-deployment
• Goal: let the nodes move autonomously to create a
distribution that maximizes a network metric
• In this case, the nodes should move autonomously to
repair a route
• Two nodes, a sink and a source are placed 3 meters
from each other
• Nodes move from the sink to the source, one after
another to establish a multi-hop route
• TDMA-MAC is used to avoid collisions
Folie 13

15. Practical Application
Folie 14
Fig. 9: a) Self-deployment in a controlled environment, b) Self-deployment in an uncontrolled environment

16. Practical Application
Data Muling
• Goal: collect data from several static nodes along the
track and upload the data via the docking station
• Static nodes at 50, 150 and 200 cm from the dock, 20
cm away from the tracks
• The data is broadcast with power level 1 of TelosB
motes (transmission range about 30 cm)
• Test the number of delivered packets for 7 different
speeds
Folie 15

17. Practical Application
• Result: All packets were correctly delivered
• Trade-off between speed and the number of packets
Folie 16

18. Related Work
Core
technology
Energy
management
$ Setup Positioning
TrainSense
(Smeets et
al.)
Model trains Unlimited
energy from
the tracks
$ Quite
difficult
Detectors +
dead-
reckoning
Sensei-UU
(Rensfelt et
al.)
Robot
following a
line
N/A $$$ Easy Travelled
distance
estimation
MiNT-m
(De et al.)
Robotic
vacuum
cleaner
(Roomba)
Batteries, auto
recharging
mechanism
$$ Very easy Video
cameras
Folie 17

19. Thank you for your attention
Folie 18