Energy-Efficient Communication Protocol for Wireless Microsensor Networks by Wendi Rabiner Heinzelman, Anantha Chandrakasan, and Hari Balakrishnan - PowerPoint PPT Presentation

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Energy-Efficient Communication Protocol for Wireless Microsensor Networks by Wendi Rabiner Heinzelman, Anantha Chandrakasan, and Hari Balakrishnan

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Title: Energy-Efficient Communication Protocol for Wireless Microsensor Networks by Wendi Rabiner Heinzelman, Anantha Chandrakasan, and Hari Balakrishnan


1
Energy-Efficient Communication Protocol for
Wireless Microsensor NetworksbyWendi Rabiner
Heinzelman, Anantha Chandrakasan, and Hari
Balakrishnan
  • Presented by
  • Sukun Kim

Based on presentation of Neha Jain
2
Overview
  • Introduction
  • Key Features of Microsensors
  • Sensor Network Model
  • Direct Communication Protocol
  • Minimum Transmission Energy Routing Protocol
  • Clusters
  • LEACH (Low-Energy Adaptive Clustering Hierarchy)
  • Results
  • Conclusion

3
INTRODUCTION
  • Nodes maybe mobile(though very low mobility)
  • Sensor networks are data-centric networks.
  • They are application specific
  • Adjacent nodes may have similar data.
  • No need of Unique ID as routing to from
    specific nodes is not required. Presence of large
    number of nodes implies large id thus, data sent
    may be less than the address.

4
Typical applications of Sensor Networks
  • Reliable environment monitoring for commercial
    and military applications
  • For a security system, acoustic, seismic and
    video sensors can be used to form an adhoc
    network to detect intrusion.
  • Monitor machines for fault detection and diagnosis

5
The Microsensor Networks
  • Consists of tens of thousands of extremely small
    , low power and low cost devices which share
    wireless channel bandwidth in order to achieve
    high quality , fault tolerant sensing networks
  • Equipped with programmable computing, multiple
    sensing and communication capability.
  • Routing protocols exercise local collaboration to
    reduce bandwidth requirement
  • have too much data to process hence automated
    data aggregation into small set of meaningful
    information is required
  • Data fusion produces more accurate signal from
    unreliable data measurement.
  • Operate and respond in a very dynamic environment

6
Assumptions for experiments
  • the radio channel is symmetric, energy required
    to transmit a message from node A to B is same as
    energy required to transmit message from node B
    to A (symmetry among nodes)
  • All the nodes in the network are homogeneous and
    energy constrained
  • All sensors are sensing data at a fixed rate and
    always have data to send to the end user.

7
Sensor Network Model
BS
8
Direct Communication Protocol
BS
9
Direct Communication Protocol
  • Requires large amount of transmit power from each
    node if the BS is far away from the nodes. This
    will quickly drain the battery of the nodes and
    reduce system lifetime.
  • The nodes furthest from the BS are the ones to
    die out first as they have the highest transmit
    energy .

10
Minimum Transmission Energy Routing Protocol
BS
Routing
11
Minimum Transmission Energy Routing Protocol
  • In these protocols nodes route data destined
    ultimately for the base station through
    intermediate nodes. Thus nodes act as routers for
    other nodes data in addition to sensing the
    environment.
  • First node dies out quicker using MTE than DC (if
    epsilon amp is large, these two will swap)
  • Nodes closest to the BS are the first to die out
    in MTE routing, as they are the ones most used as
    routers for other sensors data

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13
Which is more Energy Efficient ?
  • When network diameter is small / the radio
    electronics energy is high, direct transmission
    is more energy efficient than MTE.
  • The most energy efficient protocol to use depends
    on the network diameter and radio parameters of
    the system.

14
Clustering
BS
15
Clustering
  • Here nodes are organized into clusters that
    communicate with a local BS and these local Base
    Stations transmit the data to the global BS,
    where it is accessed by the end user.
  • Reduced distance of data transmission as the
    local BS is typically close to all nodes in the
    Cluster but BS becomes energy constrained
  • As soon as cluster -head node dies, all nodes
    from that cluster effectively die since there is
    no way to get their data to the base station.
  • In Adaptive clustering, cluster heads change as
    nodes move in order to keep the network fully
    connected.

16
Optimal percentage of nodes, N that should be
cluster heads
  • If it is less than optimal N, some nodes have to
    transmit very far to reach the cluster head,
    large global energy.
  • If more than optimal N, more cluster heads have
    to transmit the long haul distances to the base
    station, hence compression is less. N 5,
    reduces energy consumption by a factor of 7.

17
Hierarchical Clustering
Each cluster head aggregates data sends to the
BS or higher level cluster head
18
Key Features of LEACH (Low-Energy Adaptive
Clustering Hierarchy)
  • Localized coordination and control for cluster
    set up and operation.
  • Local compression to reduce global communication
  • Randomized rotation of the cluster heads and the
    corresponding clusters.
  • Random Death of nodes there is no one section
    of the environment that is not being sensed as
    nodes die, as occurs in the other protocols.

19
Randomised Rotation
  • The high energy cluster head position rotates
    among the various sensors in order to not to
    drain the battery of a single sensor. (currently
    just random)
  • Sensors elect themselves to be the local cluster
    heads at any given time with a certain
    probability, and broadcast their status to other
    sensors each sensor node choosing the
    cluster-head with strongest signal (can minimize
    transmission power)
  • Each node takes the decision independent of the
    other nodes to become cluster head. It is based
    on the suggested percentage determined a priori
    and round number

20
LEACH - Algorithm Details
  • The operation is broken up into rounds
  • Advertisement phase
  • use CSMA MAC protocol, and all cluster heads
    transmit with same energy
  • Set up phase Cluster is organized
  • each node transmits to which cluster head it
    wants to belong to using a CSMA MAC
  • Steady State Phase Data Transfers to Base
    Station occur

21
LEACH
  • Uses TDMA with CDMA

TDMA
code3
code1
CDMA
code2
22
LEACH uses TDMA with CDMA
  • Then cluster head creates a TDMA schedule for all
    nodes within its cluster telling each node when
    it can transmit.
  • Allows radio component of each non cluster head
    to be turned off at all times except during its
    transmit time, thus minimizing the energy
    dissipated in the individual sensors. They must
    keep their receivers on during set up phase to
    hear the advertisements of all cluster heads.
  • Transmission in one cluster will affect
    communication in a nearby cluster, hence each
    cluster communicates using different CDMA codes.

23
How is LEACH Energy Efficient ?
  • Energy requirement is distributed among all the
    sensors by randomized rotation
  • Local fusion of data in cluster head reduces
    amount of data to be transmitted to the base
    station (computation for fusion is cheaper than
    communication) .
  • Main energy saving is due to combining lossy
    compression with the data routing . tradeoff
    between quality of output and amount of
    compression resulting in substantial reduction of
    overall energy dissipation.

24

Total system energy dissipated using direct
communication, MTE routing and LEACH for
the 100-node random network . Eelec 50 nJ/bit,
messages are 2000 bits
25
System lifetime using direct transmission, MTE
routing, static clustering, and LEACH with 0.5
J/node
26
Results
  • LEACH reduces communication energy by as much as
    8 times compared to direct transmission and MTE
    routing
  • The first node death in LEACH occurs over 8 times
    later, and last node death occurs over 3 times
    later than any other protocol.

27
Conclusion
  • LEACH outperforms conventional routing protocols
    like direct transmission, minimum-transmission-ene
    rgy, static clustering algorithms
  • LEACH is distributed. Nodes do not require
    control information from the base station nor
    knowledge of the global network

28
Possible Questions
  • How much data fusion is possible in cluster head?
    (with randomized rotation of cluster head, it can
    be worse)
  • What if BS has big antenna?
  • What is the effect of contention and bandwidth
    limit?
  • With parameters of mica or mica2?

29
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30
Big antenna at base station
BS
Cost 5
Cost 5
Cost 20
31
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32
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