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Energy Aware Routing in Wireless Sensor Networks

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Energy Aware Routing in Wireless Sensor Networks Ashish Babbar EE 668 Overview Wireless Sensor Network Motivation Why? Concerns Routing protocol design goals Various ... – PowerPoint PPT presentation

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Title: Energy Aware Routing in Wireless Sensor Networks


1
Energy Aware Routing in Wireless Sensor Networks
  • Ashish Babbar
  • EE 668

2
Overview
  • Wireless Sensor Network
  • Motivation
  • Why?
  • Concerns
  • Routing protocol design goals
  • Various routing protocols
  • Flooding
  • Clustering
  • Geographic
  • Energy aware
  • Gradient
  • LEACH (Low Energy Adaptive Clustering Hierarchy)
  • SPIN (Sensor Protocols for Information via
    Negotiation)

3
What is Wireless Sensor Network?
  • Sophisticated systems that links the physical
    world with
  • digital data networks
  • Consist of base stations and hundred to thousand
    of nodes (wireless sensors).
  • Each node possesses the aptitude of performing
    computations and communication, executing
    different
  • sensing tasks.

4
Wireless Sensor networks.
  • Wireless sensor networks greatly extend our
    ability to monitor control physical environment
    from remote locations.
  • Can improve the accuracy of information by
    collaboration among sensor nodes.
  • They provide a distributed processing of vast
    quantities of information.
  • When networked the sensors can aggregate the data
    to provide a rich multi-dimensional view of the
    environment (e.g. seismic data, acoustic data and
    high resolution images).
  • Networked sensors can continue to operate
    accurately in face of failure of individual
    sensors.

5
Motivation
  • Each sensor node operates autonomously with no
    central point of control in the network.
  • Each node bases its decision on its mission,
    the information it currently has its knowledge
    of its Computing, Communicating and Energy
    resources.
  • Because the sensor networks can use up their
    limited supply of energy simply performing
    computations and transmitting information in a
    wireless environment, energy conserving form of
    communication and computation are essential.

6
Why?
  • Recharging sensors is a difficult task.
  • Minimizing energy consumption is essential in
    sensor networks.
  • Sensor networks have high level of redundancy,
    which can be eliminated.
  • A dense sensor network can work with only part of
    its nodes being active.
  • It is possible to prolong the network lifetime
    while maintain its functionality by carefully
    choosing the active nodes.

7
Concerns
  • A good power-saving coordination technique should
    have the following characteristics
  • It should allow as many nodes as possible to turn
    their radio receivers off.
  • Enough nodes must stay awake to form a connected
    backbone.
  • The backbone should provide about as much total
    capacity as the original network.
  • Power saving should inter-operate correctly with
    whatever routing system the sensor network uses.

8
Routing Protocol Design Goals
  • Low Energy
  • Minimize communication
  • Aggregate data in network
  • Low Node Duty Cycle
  • Minimize individual node responsibility
  • Traffic spreading / Load balancing
  • Shut down nodes when possible
  • Robust
  • Adapt to unpredictable environment without
    intervention
  • Scalable
  • Rely on localized algorithms no centralized
    control
  • Low Latency
  • Must meet application latency and accuracy
    requirements
  • Small Footprint
  • Must run on hardware with severe memory and
    computational power constraints

9
The Routing Protocols
  • Techniques
  • Flooding
  • Gradient
  • Clustering and Cellular
  • Geographic
  • Energy Aware

10
Flooding
  • A node wishing to disseminate data across the
    network sends a copy of the data to all the
    neighbors.
  • Whenever a node receives some data, it makes
    copies of the data and sends that data to all
    its neighbors except the node from which it just
    received the data.
  • Flooding introduces a lot of redundancy, due to
    data delivery to all nodes in its neighborhood.

11
FLOODING
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FLOODING
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FLOODING
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FLOODING
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FLOODING
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FLOODING
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17
Clustering
  • Sensor nodes in a particular region are assigned
    to different clusters.
  • Each cluster has a central cluster head.
  • Nodes send data to this central cluster head.
  • The cluster head in turn forwards it to a base
    station.
  • Cluster heads have to be high energy nodes.

18
Geographic Routing
  • The physical nature of a sensor networks
    deployment makes geographically scoped queries
    natural.
  • If nodes know their locations, then geographic
    queries can be leveraged to constrict the data
    dissemination to the relevant region only.
  • This would reduce the routing control overhead,
    by optimizing the search process by finding
    sources based on geographic information.
  • Typical examples are Greedy Perimeter Stateless
    Routing (GPSR) and Geographic and Energy aware
    routing (GEAR)

19
LEACHLow-Energy Adaptive Clustering Hierarchy
  • Techniques
  • Randomized, self-configuring cluster formation.
  • Localized control of data transfer.
  • Low energy media access control.
  • Application specific data processing such as data
    aggregation and compression.

20
LEACH Abstract
  • Nodes organize themselves into clusters with one
    node acting as cluster head.
  • All non-cluster head nodes transmit data to their
    cluster head.
  • Cluster-head receives data and performs signal
    processing functions on the data and transmits
    data to the remote Base Station.
  • Leach involves randomized rotation of high energy
    cluster heads so that it does not drain out the
    battery of a single node.

21
Leach operation
  • Two Phases
  • Set-up phase
  • -Clusters are organized
  • Steady phase
  • -Data transferred from nodes to cluster-heads on
    to Base station.

22
Cluster Head Selection
  • Each node elects it self to be a Cluster-head at
    the beginning of a round, with a certain
    probability.
  • Nodes that have not become Cluster heads recently
    may become one.
  • Decision based on the suggested percentage of
    cluster-heads for the network.
  • In order to evenly distribute energy dissipation
    among the nodes the cluster heads are not fixed.
  • This position is self-elected at different time
    intervals.

23
Cluster Head Selection
  • The cluster head node broadcasts its status to
    other sensors in the network.
  • Each sensor node determines to which cluster it
    wants to belong by choosing cluster heads which
    need the minimum communication energy.
  • Once all nodes are organized into clusters each
    cluster head creates a schedule for nodes in its
    cluster.

24
Set Up Phase
  • Cluster Formation
  • Each cluster-head sends an advertisement message
    (ADV) using CSMA MAC protocol
  • Consists of nodes ID and header that distinguish
    it as an ADV message
  • Based on the strength of the ADV signal, each
    non-cluster head node determines its CH
  • Each node transmit a join-request to the CH using
    CSMA MAC protocol.
  • Message consist of node ID and CH ID.
  • Each cluster-head sets a TDMA schedule
  • This guarantees no collisions in data messages,
    radio components can be turned off at all times
    except during transmission

25
Steady phase
  • Nodes send data in their assigned time slot.
  • After receiving all its data the Cluster head
    performs data fusion (aggregation).
  • The aggregated data is then sent to the base
    station (high energy transmission).
  • To reduce the node interference each cluster uses
    different CDMA codes.
  • Before transmission each node senses the channel.
  • If the channel is free the cluster head transmits
    the data to the base station.

26
Advantages of LEACH
  • Uses a self organizing adaptive clustering
    protocol to distribute energy load evenly among
    sensors in the network.
  • Performs local data fusion to compress the amount
    of data being sent from clusters to the base
    station, further reducing energy dissipation and
    increasing system lifetime.
  • The optimal number of clusters can be determined
    a-priori depending on the network topology and
    relative cost of computation versus
    communication.
  • The first node death in LEACH occurs about 8
    times later than the first node death in direct
    transmission and static clustering protocols

27
SPINSensor Protocols for Information via
Negotiation
  • Efficiently disseminates information among
    sensors in an energy constrained wireless sensor
    network.
  • Nodes running SPIN protocol name their data using
    high level data descriptors called meta data.
  • The nodes use meta data negotiations to eliminate
    transmission of redundant data in the network.
  • SPIN nodes can base their communication decisions
    on knowledge of data and resources allowing them
    to distribute data given limited energy supply.

28
Why use SPIN?
  • The Classical flooding approach has the following
    deficiencies
  • IMPLOSION The nodes send data to its neighbors
    regardless of the fact whether the node has
    already received data from another source. The
    system thus waste energy in doing so.
  • OVERLAP Sensor nodes often cover overlapping
    geographical areas and thus the nodes often
    gather overlapping pieces of sensor data. This is
    a harder problem to solve than implosion.
  • RESOURCE BLINDNESS In classical flooding nodes
    do not modify their activities based on the
    amount of energy available to them.

29
Implosion
Node A starts by flooding data to all its
neighbors
A
C
B
D
30
Implosion
Node A starts by flooding data to all its
neighbors
A
C
B
D
31
Implosion
Two copies of data arrive at D. The system wastes
energy in the unnecessary send and receive
A
C
B
D
32
Overlap
r
s
q
A
B
(r,s)
(q,r)
C
33
The Solution
  • The SPIN protocol incorporates two key
    innovations that overcome the deficiencies
  • NEGOTIATION
  • To overcome the problem of implosion and overlap,
    the SPIN nodes negotiate with each other before
    transmitting data.
  • Negotiation ensures that only useful information
    will be transferred.
  • To negotiate successfully nodes must be able to
    describe or name the data they observe, these
    descriptors are called meta-data.
  • Thus the negotiation process which precedes the
    actual data transmission eliminates implosion by
    not transmitting the redundant data messages.
  • The use of meta data descriptors eliminates the
    overlap as it allows nodes to name the portion of
    data they are interested in obtaining.

34
The Solution.
  • RESOURCE ADAPTATION
  • In SPIN the nodes poll their resources before
    data transmission.
  • Each sensor node has its own resource manager
    that keeps track of resource consumption.
  • The various applications would probe the manager
    before transmitting or processing data.
  • Being aware of local energy resources allows
    sensors to cut back on activities whenever their
    energy resources are low.
  • The nodes hence monitor and adapt to changes in
    their own energy resources to extend the
    operating lifetime of the system.

35
SPIN Messages
  • SPIN nodes use three types of messages to
    communicate
  • ADV new data advertisement. When a SPIN node
    has data to share it can advertise this fact by
    transmitting an ADV message containing meta-data.
  • REQ request for data. A SPIN node sends an REQ
    message when it wishes to receive some actual
    data.
  • DATA data message. Data messages contain actual
    sensor data with meta-data header.
  • Because ADV and REQ messages contain only
    meta-data they are smaller and cheaper to send
    and receive than their corresponding data
    messages.

36
SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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SPIN
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ADV REQ DATA
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51
QUESTIONS?
52
References
  • W. Heinzelman, A. Chandrakasan and H.
    Balakrishnan, Energy-Efficient Communication
    Protocol for Wireless Microsensor Networks,''
    Proceedings of the 33rd Hawaii International
    Conference on System Sciences (HICSS '00),
    January 2000.
  • W. Heinzelman, J. Kulik, and H. Balakrishnan,
    Adaptive Protocols for Information Dissemination
    in Wireless Sensor Networks,'' Proc. 5th ACM/IEEE
    Mobicom Conference (MobiCom '99), Seattle, WA,
    August,1999
  • Wireless sensor networks / edited by C.S.
    Raghavendra, Krishna M. Sivalingam, Taieb Znati.
  • Energy scavenging for wireless sensor networks
    with special focus on vibrations / by Shad
    Roundy, Paul Kenneth Wright, Jan M. Rabaey
  • http//www.ibr.cs.tu-bs.de/lehre/ws0304/muc/pdf/ws
    n_energy.pdf
  • http//ramp.ucsd.edu/mmcnett/re/SNTalk.ppt
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