Wireless underground sensor networks

1. Guide-K A Netravathi

2.  Sensor networks are highly distributed networks
of small, lightweight wireless nodes, deployed
in large numbers to monitor the environment or
system by the measurement of physical
parameters such as temperature, pressure, or
relative humidity.
 Sensor nodes have limited computational
power, limited memory,limited power in form of
battery,limited communication capability
 The applications of sensor networks are
endless, limited only by the human imagination

3.  WUSN is defined as a group of nodes whose
means of data transmission and reception is
completely subterranean
 In WUSN the node is completely
underground
 It may be in open space like a cave or
completely embedded in dense soil or rock
 WUSN have many applications like
infrastructure,security,environmental
monitoring etc.

4.  The current system consists of a buried sensor and a data
logger on the surface
 Very useful for a variety of applications
 Suffer from several shortcomings when compared to wireless
underground sensor networks
 Concealment
 Ease of deployment
 Timeliness of data
 Reliability
 Coverage density

5.  Concealment
› In current systems the dataloggers are deployed
on surface
› Communication is easier as no underground
communication is involved
› Above ground equipment is vulnerable to
agricultural and landscaping equipment or
unacceptable for asthetic reasons
› In WUSN the equipment is underground secure
from any theft and protected from damage

6.  Ease of deployment
› Current technology uses wired systems
› Tough to add new sensors or data loggers
› No scalability issues with WUSN as its fully wireless
Timeliness of data
Due to wireless nature the data from sensors is
forwarded in real time to sink
In data loggers the data may be stored for later
retrieval

7.  Reliability
› Current systems are fully dependent on data
loggers
› Data logger failure means whole network failure
› WUSN eliminate the need of datalogger
› Each sensor can forward sensor readings
independently
› WUSN’s are self healing

8.  Coverage density
› Current systems require the sensor to be
deployed close to the data logger
› It results in less coverage
› WUSN eliminate the need of data logger
› Sensors can be deployed anywhere,hence
increasing the coverage area

9.  Environmental monitoring
› Monitor soil water and mineral content for
irrigation
› Monitor soil conditions for sports field monitoring
› Monitor soil movement for landslide prediction
› Coal mine monitoring
› Monitor glacier movement
› Earthquake monitoring

10. • A WUSN deployed for monitoring a golf course.
• Underground sensors can be used to monitor soil salinity, water
content, and temperature.
• Surface relays and sinks, which can be placed away from playing
areas, are used to forward WUSN sensor data to a central receiving
point

11.  Infrastructure monitoring
› Underground infrastructure like pipes,wiring
etc.
› Monitoring underground components of
bridges, dams etc.
› Minefield monitoring
Location determination of objects
Driver alert
Autonomous fertilizer unit
Locating people in case of building collapse

12.  Border patrol and security monitoring
› Home security systems
› Detecting border intrusions

13.  Power conservation
 Topology design
 Antenna design
 Environmental extremes

14.  Underground sensor nodes require more
power as attenuation is more
 Difficult to recharge or replace batteries
 Solar or any alternate energy form also
can’t be used
 Power conservation is the key
 Should be implemented by using power
efficient hardware and communication
protocols

15.  Considerations
› Application-The density of sensor deployment is
dictated by the application.Security application
require dense whereas soil monitoring less dense
deployment
› Power usage minimization-Power usage can be
minimized by designing a topology with a large
number of short-distance hops rather than a smaller
number of long-distance hops.
› Cost-Deeper and Denser deployments result in more
costs.Establish trade offs

16.  Underground topology
› All sensor devices underground
› Sink may be underground or above it
› Can be single depth or multi depth
› Provides maximum concealment of network
› Ground air ground path can be used

17. Underground topology Hybrid topology

18.  Hybrid topology
› Mixture of underground and aboveground
sensor devices
› Power intensive underground hops can be
traded for less expensive hops in a terrestrial
network.
› Terrestrial devices can be easily recharger or
replaced
› Network is not fully concealed

19.  Issues to be considered
› Variable requirements-Devices near the
surface air interface have different
requirements from those deeper inside as
they suffer from reflection
› Size-Lower frequencies require larger
antennas, this is a challenge as sensor
device size should be small
› Directionality-The antennas should be
oriented for both horizontal and vertical
communication

20.  Underground environment is not ideal for
electronic devices
 Protection from water,animals,insects
etc. is needed.
 Devices should be resistant to pressure of
people or objects moving overhead

21.  Underground channel properties
› Extreme path loss
› Reflection/Refraction
› Multi path fading
› Reduced propagation velocity
› Noise

22.  Effect of soil properties on channel
› Water content
› Particle size
› Density
› Temperature
 Alternative physical layer technologies
› EM waves not optimal for underground
› Magnetic induction can be a possible
alternative as it does not get affected by soil
and water
› Multi path fading not an issue for MI as its near
field,non propagating
› Antenna design is simpler
› Antenna strength is proportional to no of turns

24.  Physical layer
› Lower frequencies are ideal for WUSN
› They face less attenuation but the antenna size
becomes large
› Lower frequencies result in lesser bandwidth
› Due to this the data rate in WUSN is very less

25.  Data link layer
› In WUSN the focus should be on less
retransmissions
› Traditional link layer protocols are contention
based or TDMA based
› These may not be applicable for WUSN
› Collision avoidance using CTS/RTS involves too
much overhead
› In TDMA based scheme the synchronization may
be lost between nodes

26. Network layer
› Ad hoc routing protocols may be
proactive,reactive or geographical
› Both proactive and reactive are not applicable
to WUSN due to signalling overhead and
syncronization issues
› Geographical routing can be helpful for WUSN
only in some cases
› Routing protocols should be dynamic as link
costs change due to soil conditions,water etc.

27.  Transport layer
› Performs function of flow control and congestion
control
› Congestion control can be done by routing
data to terrestrial relays which are capable of a
higher data rate
› Window based mechanism for flow control may
not be applicable to WUSN as retransmissions
are more
› In WUSN retransmission should be less to save
energy

28. › Utilizing sensor data for channel prediction
› Utilizing channel data for soil property prediction
› Physical-layer based routing
› Opportunistic MAC scheduling
› Cross-layer between link and transport layers

29.  Deploying wireless sensor networks for underground
applications have many advantages like ease of
deployment,concelment etc. over conventional sensor
networks
 Several challenges like underground wirless channel,
less bandwidth, power conservation etc. arise when
WSN are implemented for underground networks
 Several changes need to be made at different layers of
the protocol architecture for WUSN
 A cross layer protocol solution may be used to solve
some of the issues with the present protocols

30.  I. Akyildiz and E. Stuntebeck,
“Underground wireless sensor
networks:research challenges,” Ad
Hoc Networks (Elsevier), in press, June
2006.
 E.P Stuntebeck. D Pompili, T Melodia, "
Wireless underground sensor networks
using commodity terrestrial motes", in
proceedings of the 2nd IEEE workshop
on wireless mesh networks, pp.111-116,
September 2006.

31.  Mo Li , Yunhao Liu, Underground
structure monitoring with wireless
sensor networks, Proceedings of the
6th international conference on
Information processing in sensor
networks, April 25-27, 2007,
Cambridge, Massachusetts, USA
 T. Zia and A.Y. Zomaya, "Security
Issues in Wireless Sensor
Networks," Proc. Int',l Conf. Systems
and Networks Comm. (ICSNC
',06), p. 40, Oct. 2006.
 Kalpana Sharma, M K