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Research Challenges in Wireless Networks of Biomedical Sensors

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Title: Research Challenges in Wireless Networks of Biomedical Sensors


1
Research Challenges in Wireless Networks of
Biomedical Sensors
  • Presented by -
  • Dipti R. Patel

2
Topics Covered
  • Introduction.
  • Biomedical Sensor Applications.
  • Artificial Retina Prosthesis.
  • Some research challenges for wireless
    communication in biomedical sensor networks.
  • Few power efficient topologies.
  • Wireless communication protocols.
  • Conclusion.
  • Questions???

3
Introduction
  • What is a sensor?
  • A sensor is a device that receives input from a
    physical or energetic phenomenon such as light,
    heat, or force.
  • Converts it into a usable input form like
    electricity.
  • Another device acts on the input and performs
    suitable action.
  • What are smart sensors?
  • Are built using a combination of sensors and
    integrated circuits.
  • Performs suitable actions on the sensed input.
  • Have wireless capabilities in order to
    communicate with an external device.

4
Biomedical Sensor Applications
  • Glucose level monitors.
  • Wireless blood sensors implanted in the human
    body.
  • Sensors monitor glucose levels and transmit that
    to external display device, say, wrist watch.
  • Cancer Detectors.
  • Cancer cells exude nitric oxide in the tissue
    surrounding the tumor.
  • Sensors can be implanted in such locations to
    detect abnormalities.
  • General Health Monitors.
  • NASA has been working on pill-sized packages
    containing sensors for monitoring surrounding
    conditions.
  • Small pills containing sensors can be swallowed
    thus enabling wireless transmission of intestinal
    conditions or diagnose gastrointestinal diseases.

5
Artificial Retina Prosthesis
6
Processing steps in retinal prosthesis

7
Challenges for wireless communication
  • Low power
  • Due to the absence of wires small physical
    size, sensors have severe power restrictions.
  • Power can be supplied using an integrated power
    supply like battery but this has a limited power
    source.
  • Power can be supplied by wireless sources like,
  • Inductance using infrared, RF signals
  • Using photo diode arrays which converts light
    into power.
  • Since biomedical sensors are implanted inside the
    human body, too much heat dissipation can damage
    the surrounding tissue.
  • Limited Computation
  • Computation is limited as a result of low power
    capabilities.
  • Most of the power is used for communication.
  • Image compression is used in retinal prosthesis
    before transmission.
  • Size constraints
  • As the sensors are implanted in the human body,
    they have to be very small.
  • Retinal prosthesis sensors have to be small
    enough to fit within the human eye.

8
Some more challenges
  • Biocompatible material
  • Sensors should be made of biocompatible materials
    as the immune system is designed to combat a
    foreign substance.
  • Some common materials used are synthetic or
    biological polymers, metals, ceramics.
  • Continuous operation
  • Once placed, sensors need to work for decades.
  • Medical risks associated with implantation make
    frequent placements and adjustments impractical.
  • Scalability
  • Many small sensors may need to be placed and work
    in conjunction with each other.

9
Some more challenges
  • Robust and Fault tolerant
  • Failure of one node should not cause the entire
    network to cease operation
  • To ensure proper data is being sent and received,
    checksums, parity check and cyclic redundancy
    check can be used
  • Security and Interference
  • It should be secure free from malicious
    interaction as it could be dangerous or even
    fatal for false readings to appear on patients
    glucose monitor and erroneous images being
    projected into eye.
  • Interference from other types of wireless
    communication such as Bluetooth devices or
    wireless networks in people standing next to
    each other

10
Power efficient topologies
  • By topology, we mean the arrangement of
    individual sensor nodes in the smart sensor chip.
  • Being fixed in specific locations,
    self-organization and routing protocols are not
    needed, thus saving power.
  • A sensor is placed within close proximity of
    other sensor nodes.
  • The power used by the transmitter is a function
    of distance and the bits transmitted. The
    receiver expends power to receive messages.
  • Few 2D topologies studied,

6 neighbors
4 neighbor
3 neighbor
11
Power efficient topologies
  • 3D topologies studied
  • Edge Routing
  • Message communication involves outer edges of the
    network where there are fewer neighbors.
  • Interior Routing
  • Here messages are communicated within the
    interiors of the network involving more neighbors.

12
Analysis Results

Interior routing 2D topology
2D and 3D topology
2D and 3D topology
13
Wireless communication protocols
  • The sensor nodes communicate with the external
    processor via the transceiver (base station).
  • All communication is wireless and TDMA is used
    for media access.
  • TDMA has the advantage in the sense that nodes
    can sleep when not sending/receiving data.
  • 2 approaches are used,
  • Cluster Based.
  • Small fraction of nodes (leaders) communicate
    with the base station.
  • The leaders collect data from other nodes in the
    cluster, compress the data and then send the data
    to the base station.
  • Since the node locations are fixed and the base
    station has a knowledge about them, the base
    station can nominate the leaders and assign a
    specific frequency to each of the leaders.
  • Leaders transmit signal which are scanned by
    non-leader nodes. The nodes then select the
    frequency/leader offering the best signal/noise
    ratio.
  • The node then joins the cluster. In this way, the
    clusters are formed.

14
Wireless communication protocols
  • Tree Based approach
  • Base station elects one or more children to be
    its children based on factors like proximity and
    node density.
  • Each node sends low intensity transmission at its
    own specific frequency.
  • Nodes that receive this signal then request the
    transmitting node to be its parent based on
    signal-noise ratio.
  • After requesting their parents, it is the turn of
    the child nodes to determine their child nodes.
  • Child node sends data to its parent via low
    energy transmissions which sends data further to
    its parent.
  • Communication between base station and its child
    is via high energy transmissions.

15

16
Comparison of protocols
  • Using the two protocols the power consumption
    with respect to distance between nodes as well as
    number of nodes in the network was studied.

17
Comparison of protocols
  • As seen in both cases cluster based approach
    proves to be more power efficient as compared to
    the tree based approach.
  • In tree based scheme each data packet passes via
    several levels of the tree and transmission/recept
    ion costs are incurred at every level. The cost
    of such multihop routing then becomes greater
    than the cost of single-hop routing that is
    present in the cluster-based scheme

18
Conclusions
  • To conclude the following can be said,
  • Wireless sensors have an immense potential in the
    field of medicine.
  • A sensor embedded in the human body can be useful
    in many ways like retinal prosthesis, cancer
    detection, blood glucose level monitoring etc.
  • There are a number of constraints on the sensors
    components like material, size, power consumption
    etc.
  • The design of wireless sensors is a critical step
    in enabling their use in medicine.

19
  • Questions????
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