Tutorial about Seismic Sensor Network

1
Tutorial about Seismic Sensor Network

• Vinayak Naik, Martin Lukac, and Deborah Estrin
• Information Processing in Sensor Networks
  (IPSN07), Cambridge, MA
• April 24, 2007
• Acknowledgments to Igor Stubailo, Derek Skolnik,
  Joey Degges, and Mike Allen for lending us
  equipments and time.

2
Special demands of seismic and acoustic
applications

• Seismic
• Large-scale deployment spanning hundreds of
  kilometers
• Its not easy
• Highly varying links with frequent disconnections
  results in challenged networks
• Remote monitoring and fixing of nodes demands
  services such as reliable broadcast, sink-based
  data collection, and maintenance of a global
  state
• Developing these services become non-trivial due
  to challenged networks
• Acoustic localization
• Sampling rate of the order few KHz
• Lew will summarize the challenges

3
Outline

• Using the seismic array out-of-the-box
• A few words about seismology
• Remotely managing and configuring array after the
  deployment
• Assembling the array in 30 minutes
• Adapting the software to fit your needs

4
Whats in the box?

• 1 PC
• 3 Cens Data Communication Controller (CDCCs)
• 1 Q330 (a combined ADC and data logger)
• Ubuntu live CD, which contains
• Emstar source code
• Emstar code compiled for the i366 and stargate
  architectures
• TFTP server and minicom to reflash the nodes (to
  be used while assembling the array)
• You may also use the CD to install all the
  required software on your PC or run it in an
  emulator such as qemu!

5
Using the CD

• Prerequisites
• A computer that can be booted using a CD and has
  wired ethernet connection
• A basic knowledge of Linux, such as use of ssh,
  scp, and ifconfig
• Procedure
• Boot your computer using the CD
• Set password for ubuntu "sudo passwd ubuntu
• setup IP address for the ubutu ifconfig eth0
  131.179.145.X netmask 255.255.255.0 broadcast
  131.179.145.255
• If using a virtual machine, unload USB-to-serial
  driver if alread loaded

6
The seismic activities before the start of the
tutorial

• Stop the data collection process (Duiker)
• Transfer data to the base station (PC)
• Strip the DTS header from the packet
• Uncompress the data
• Convert the data from miniseed to ascii format
• Transfer data to your laptop
• Plot the data using gnuplot
• Wait, the theory about seismology is coming up.

7
In situ data collection and presentation

• Start Duiker and let it run for 4 minutes
• Stop Duiker
• Strip the header
• Uncompress the data
• Convert the data from miniseed to ascii format
• Transfer data to my laptop
• Plot the data using gnuplot

Same as the previous slide
8
Outline

• Using the seismic array out-of-the-box
• A few words about seismology
• Remotely managing and configuring array after the
  deployment
• Assembling the array in 30 minutes
• Adapting the software to fit your needs

9
Seismology 101
Wikipedia An earthquake is a phenomenon that
results from the sudden release of stored energy
in the Earths crust that creates seismic waves.
There are two types of seismic wave, 'body
wave' and 'surface wave'. There are two kinds of
body waves primary (P-waves), travel fastest
through any type of matter and secondary
(S-waves), shear, the most destructive. Body
waves travel through the Earths interior
P-wave speed 1.5-8 Km/s S-wave speed 60-70 of
the speed of P-wave
10
Seismic wave energy

• Richter TNT for Seismic Example
• Magnitude Energy Yield (approximate)
• -1.5 6 ounces Breaking a rock on a lab
  table
• 1.0 30 pounds Large Blast at a Construction
  Site
• 2.0 1 ton Large Quarry or Mine Blast
• 4.0 1,000 tons Small Nuclear Weapon
• 4.5 5,100 tons Average Tornado (total
  energy)
• 6.5 5 million tons Northridge, CA Quake, 1994
  
• 7.0 32 million tons Japan Quake,1995Largest
  Thermonuclear Bomb
• 8.0 1 billion tons San Francisco, CA Quake,
  1906
• 9.0 32 billion tons Chilean Quake, 1960
• 12.0 160 trillion tons Fault Earth in half
  through center
• 160 trillion tons of dynamite is a frightening
  yield of energy. Consider, however, that the
  Earth receives that amount in sunlight every day.
  
• Because of this huge amount of energy released
  the seismic waves travel large distances and make
  possible to capture them with different kinds of
  seismic sensors (seismometers).

11
Seismic sensors
Most signals are composites of many
frequencies. Analog with light and
sound Seismic Light Sound Short-period Bl
ue Treble Long-period Red Bass
Typical seismogram
The long-period and short period instruments are
called "narrow" band used for volcano experiment
by Harvard. They sense frequencies near 1/15 s
and 1 hertz respectively. The yellow region is
the low end of the frequency range audible to
most humans, 20 hertz to 20,000 hertz.
A broadband instrument senses most frequencies
equally well. For our data collection we use the
best in its class CMG-3T broadband sensor, made
by Guralp Systems. Its standard frequency
response is 120 s 50 Hz what results in high
quality seismic data.
Frequency responses of seismometers
12
About Middle America Subduction Experiment (MASE)

• We have a seismic deployment to study the
  structure of the mantle in Mexico
• The deployment consists of wireless stations
  covering large distances
• We developed software to
• Handle collection the seismic data
• Manage the seismic system
• This tutorial presents this software and how to
  use it

13
Seismic deployment application requirements

• Extensive 500 Km from Acapulco through Mexico
  City to Tampico
• Dense 1 sensor every 5-10 Km
• High bandwidth Data acquisition rate 3 - 24 bit
  channels at 100Hz each
• Online and Reliable Semi real-time (on the order
  of days), reliable data delivery to UCLA for
  analysis
• Online system management
• Query state, change configuration, update
  binaries
• Can not interfere with data delivery
• Application driven topology application
  determines sensor placement
• Infrastructure does not (Cant rely on
  pre-existing cell or power infrastructure)

MASE Given these requirements, we deployed solar
powered seismic stations equipped with 802.11b
14
MASE wireless seismic station
15
A block diagram of the systems architecture
ethernet
Q330 (ADC)
Replace with your own
16
Pakistan earthquake

• Our network
• Achieves almost 10 times better resolution than
  the previous network as of Oct. 2005 (with 50
  sites total). Now it is 20 times better (100
  sites)
• Provides visualization of the upper mantle and
  the subduction process, coast to coast across
  Mexico.

17
Google video

• The data was used to analyze the structure of the
  earth underneath Mexico
• Results are being submitted to the Science journal

18
Outline

• Using the seismic array out-of-the-box
• A few words about seismology
• Remotely managing and configuring array after the
  deployment
• Assembling the array in 30 minutes
• Adapting the software to fit your needs

19
Networking support needed for both data
acquisition and system management

• Data delivery Bandwidth driven
• Bandwidth 20-40 of MB per day per station
• Latency get the data eventually, but reliably
• Many to one routing
• System Management Latency driven
• Bandwidth usually less than 10s of KBs
• Latency as fast as possible
• One to all routing and back

20
Use of wireless network for remote operation

• Demonstrate use of Delay Tolerant Shell (DTS)
• Start dtsh
• Issue a ps command
• See result of the ps command
• Demonstrate the use file transfer
• Xfer a file from /opt/test
• Demonstrate the use of file mover
• Create a file on a stargate
• Show the same file on the PC
• Xfers
• Shows the active transfers
• Links
• Shows existing links on a node
• Sink_status
• Shows the upstream route to the sink

Configuration utilities
Data collection utility
Adjunct utilities
21
Challenges handled by DTS, file transfer, and
file mover

• Frequent unpredictable disconnections
• Rainy season sites flood (some 24x7), trees grow
• Wind misaligned antennas
• Equipment malfunction amps burn, voltage
  regulators break
• Poor and unstable links
• Connectivity secondary concern for site selection
• Stretched links highly susceptible to weather and
  environment
• Useful tools for operating wireless sensor
  networks under harsh wireless settings

22
System management

• Existing management tool remote shell (ssh)
• Modified management tool Disruption Tolerant
  Shell
• Asynchronous remote shell to all nodes in network
  simultaneously
• Provides node management capabilities when
  end-to-end connections are unavailable or fail
• Ensures that commands will succeed as long as
  there is eventually a connection between a node
  and any other node that already has the command

df h ls /opt/dts/file_mover wc
A
E
B
C
D
F
Commands
Responses
23
Data delivery using DTN techniques

• Buffer data into hour long bundles (1-3 MB)
• Deliberate one hop bundle transfer
• Path to sink determined by best ETX
• Improvement over end-to-end
• Not affected by path disconnections
• Keeps retrying on single link instead of full
  path
• Continual progress being made towards sink
• More efficient use of bandwidth in face of
  disconnections and bottlenecks

A
B
C
F
end-to-end
hop-by-hop
24
Extra fun features of DTS

• Guaranteed in order execution from source node
• Reboot and crash safe
• Implicit feed back on nodes and links spot
  bottlenecks, dead nodes
• Execute a command on individual nodes
• Push a file to all nodes
• Distribute new script or component

25
Handling sessions in DTS

• A sequence number is assigned per source node per
  session
• Each node publishes a starting sequence number
  across the network
• It identifies the oldest command issued by a node
  that should be in the network
• Any commands and responses with sequence numbers
  below the value (for that particular node) are
  discarded and not propagated
• User controls the starting sequence number
• To remove commands from the network, user
  increments the commands source node starting
  sequence number
• Can choose to do this after all the nodes have
  reported responses or sooner
• Giving control of seqno to user is simple, easy
  to understand, and efficient
• Utilities to handle seqno
• Use seqno command to see all the nodes starting
  sequence numbers
• Use incr command to increment the starting
  sequence number on the current node

26
Outline

• Using the seismic array out-of-the-box
• A few words about seismology
• Remotely managing and configuring array after the
  deployment
• Assembling the array in 30 minutes
• Adapting the software to fit your needs

27
Ingredients

• 3 stargates to form a 1-hop network
• 1 computer
• 1 serial cable
• 1 ethernet hub and 1 ethernet cable

28
Assembling a seismic node

• Connect an episensor to the Q330
• Connect Q330 to the wired ethernet hub
• Connect a stargate to the wired ethernet
• Connect wireless antenna to the stargate
• Note that you can substitute Q330 with your
  choice of data logger

29
Reprogramming the stargates

• Connect PC to the wired ethernet
• Connect a serial cable from PC to a stargate
• Configure minicom profile called stargate0
• In stargate-install.exp, change the IP address of
  the TFTP server to PCs IP address
• Flash the kernel and the root file system
• The kernel and the root file system comes with
  all the seismic software!
• Screenshot of the flashing in progress

30
Configuring a gateway node (base station)

• Designate a stargate as a gateway
• Restart DTS

31
Index

• Episensor
• Measures movement across multiple axes
• Q330
• Data logger, GPS, accurate maintenance of time
• PDA
• Reports status and configures Q330 via infra-red
• Williard
• A closed-source software to retrieve the data
  from Q330
• Duiker
• An open source software to retrieve the data from
  Q330
• A comparison with Antelope (supports network,
  open source, and inexpensive)
• DTS
• An open source software for the remote management
  of stargates

32
Outline

• Using the seismic array out-of-the-box
• A few words about seismology
• Remotely managing and configuring array after the
  deployment
• Assembling the array in 30 minutes
• Adapting the software to fit your needs

33
Use of the software for other wireless sensor
networks

• Replace Q330 with ADC of your choice
• Install a driver that collects data from the ADC
  and creates files on the stargate at
  /opt/dts/xfer
• file_mover will transfer files to the gateway
  node
• No change in DTS and other utilities

34
Convert existing 7.2/7.3 stargates into seismic
nodes

• Download dts-whole-system.tar.gz and
  dts-whole-system-install.tar.gz to /opt on the
  stargate
• Make sure that the script dts-whole-system-install
  .tar.gz is executable
• Execute the script

35
Adapting the DTS code for your needs

• Change code in emstar/devel/dts/dts/dts_status.c
• Compile code for stargate architecture
• Stop DTS if it is running
• Copy the new code to the right place on a
  stargate
• Start DTS and see the change

36
Convert other platforms into seismic arrays

• Portable to Linux-based platforms
• Instructions to port EmStar to other platforms

37
Seismology of the future at CENS

• Deploy the CDCCs in Peru
• Use of low power LEAP-II nodes instead of
  stargate
• Use of low power and inexpensive ADC boards from
  Reftek Corp. instead of Q330
• Deploy combination of the LEAP-II and the new ADC
  
• For GeoNet to study aftershocks
• For structural health monitoring of tall
  buildings in Los Angeles

38
A few upcoming features of DTS

• Provide visualization of the data movement
• Using a coarse grained global time (one second),
  recreate movie of file movement for entire
  network
• Can help spot network problems and bottlenecks
• Upload data to SensorBase.org
• Makes it easy to visualize and browse data
  collection status
• RSS feed can provide access to anyone who wants
  to monitor problems or generic status of network
• Web interface to simplify operation
• Command line interface is nice for Linux pros
• Web interface more intuitive for asynchronous
  model

39
Thank you

• Resources for users and developers
• Emstar web-page
• Emstar mailing list
• Disruption Tolerant Shell in the Proceedings of
  the 2006 SIGCOMM workshop on Challenged Networks

• Wish you happy seismography!

40
Use of seismic sensing

• The similarity between the Mexico and LA region
• P and S waves
• How is the seismic array different from the
  Harvard's volcano motes?
• What is the sampling frequency

41
Need for DTS, file transfer, and file mover

• Unreliable links
• Need to broadcast commands to the nodes and get
  responses from the all the nodes
• Need to broadcast files to the nodes
• Hop-by-hop data movement

42
18 - A 152 - B 69 - C 77 - D 107 - E 42 -
F 81 - G 202 - H 76 - I 106 - J 95 - K 53 -
L 157 - M
13 Node Cuernavaca Line
L
K
Data paths
A
B

• Network topology does not reflect the mostly
  linear physical topology

A sink Direct inet connection
F
G
D
C
E
H
M
I
J
N