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Prevailing over Wires in Healthcare Environments: Benefits and Challenges

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Wireless technologies spreading in healthcare environments ... Electrocardiogram (ECG) Records electrical signals from the heart. Continuous signals ... – PowerPoint PPT presentation

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Title: Prevailing over Wires in Healthcare Environments: Benefits and Challenges


1
Prevailing over Wires in Healthcare Environments
Benefits and Challenges
  • Authors David Cypher, Nicolas Chevrollier,
    Nicolas Montavont, and Nada Golmie
  • Presentation by Mohamad Chaarawi
  • COSC 7388 Advanced Distributed Computing

2
Introduction
  • Wireless technologies spreading in healthcare
    environments
  • Need a reliable connection especially in this
    kind of environment
  • Cost effectiveness
  • Universal interface for wireless communication

3
Wireless over Wires?
  • Cost and time of Wiring
  • Mobility
  • Interoperability
  • Patient comfort
  • Ubiquitous connectivity

4
Topology
5
Outline
  • Healthcare applications
  • User case
  • Wireless technologies
  • Deployment
  • Interference
  • Moving between APs
  • Summary

6
Universal Standard
  • Development of a specification for wireless
    universal and interoperable interface
    communication
  • Transparent
  • Easy to use
  • Quicky (re)configurable
  • Not starting from scratch
  • IEEE 802 Local Area Network/Metro Area Network
    standards organization

7
Healthcare Applications (I)
  • Requirements
  • Reliable connectivity
  • Timeliness and integrity of information
  • BW, delay, loss
  • Different medical applications will use different
    wireless technologies

8
Healthcare Applications (II)
Medical Data
General purpose
9
Wireless Technologies
  • Standards developed by IEEE 802.
  • WLAN (IEEE 802.11) uses a single media access
    control (MAC) sublayer with many different
    physical layers (a/b).
  • WPAN each defines its MAC sublayer and physical
    layers.
  • IEEE 802.15.1 includes layers of the Bluetooth
    specification
  • IEEE 802.15.4 designed for low data rates, low
    power consumption, and low usage applications

10
Electrocardiogram (ECG)
  • Records electrical signals from the heart
  • Continuous signals
  • Must be sampled to be digitized (important for
    choosing the traffic characteristics of the
    transport)
  • For Example we have 500 samples/s and sample
    size is 8 bits, this means that the data traffic
    requirement is 4000 bits/s

11
Heart to Digital
12
Wireless Technologies
13
Packetization
  • The pairing focuses on packetization (framing and
    the sample accumulation delay).
  • Considering just the data traffic requirement,
    the 802.15.4 is the most appropriate

14
Medium Access
  • Need to consider the method that contributes to
    the end-to-end delay
  • 802.15.4 uses CSMA/CA which produces a random
    access delay for each frame.
  • Analysis of the ECG shows that the medium access
    delay ranges from 1.024 to 5.216 ms, as the
    number of samples per frame varies from 1 to 118
    (max payload)

15
Data Service
  • ECG application is more sensitive to time delays
    than to packet loss.
  • IEEE 802.15.4 offers both unacknowledged and
    acknowledged which contribute to delay and
    overhead, so unacknowledged data service is used
    in our case.

16
Deployment issues (I)
  • Several issues need to be considered for
    deployment
  • Coverage Area
  • Network Architecture
  • Frequency Allocation
  • Output power

17
Deployment issues (II)
  • ECG leads on the patients body collect the
    medical data that is displayed on a monitor
    nearby. This data also is transmitted to a remote
    station.
  • Movement of the patient between rooms should not
    break the communication.

18
Coverage Area (I)
  • Coverage areas vary between
  • Body area (lt 1m)
  • Personal area (lt 10m)
  • Local area (lt 100m)
  • Wide area (gt 100m)
  • 802.15 designed for personal area and 802.11 for
    local area.

19
Coverage Area (II)
  • Coverage areas vary widely based on radio
    frequency used and the physical environment.
  • For the personal area, the signal can be
    constrained within a limited area, while for
    local area larger distances need to be covered.
  • Since the ECGs communication devices are close to
    each other, a personal area network (802.15.4)
    can be used.
  • But to communicate with remote stations, a local
    area network is needed.

20
Network Architecture
  • Wireless technologies are designed with
  • Infrastructure mode assumes a fixed AP, which
    attaches to the established network and thus
    provides a communication portal for stations in
    the APs range.
  • Ad hoc mode permits devices to communicate with
    other peer devices dynamically (802.15). Quick
    deployment is an advantage but Radio Frequency
    management can be a problem.
  • For the ECG, Ad hoc mode is more appropriate.

21
Frequency Allocations (I)
  • Radio frequency (RF) spectrum (3 kHz 300 GHz)
  • In the US, the Federal Communications Commission
    (FCC) divides it into many usage bands.
  • Bands for medical usage include (ISM)
  • Industry
  • Scientific
  • Medical
  • Those bands are shared however with other users.

22
Frequency Allocations (II)
  • Need to select first which ISM band to use.
  • All three wireless technologies use the 2400 MHz
    band. 802.11a and 802.15.4 have other channels in
    some bands that can be used in case the 2400 MHz
    band is overcrowded.
  • Next step How the band is used?

23
Frequency Allocations (III)
  • Need to configure the channels to avoid or reduce
    interference by avoiding overlapping channels.
  • Channel configuration can be done statically or
    dynamically.

24
Frequency Allocations (IV)
25
Output Power
  • Power used to generate the signal affects the
    coverage area and the power consumption of the
    device.
  • WLANS -gt mains
  • WPANS -gt batteries
  • Wireless to remove wires!! So ECG is battery
    powered

26
Pairing ECG and Wireless Technologies
  • After looking at the deployment issues discusses,
    the IEEE 802.15.4 can support the needs for the
    ECG.
  • A WLAN can support the communication between the
    monitor device and remote station.
  • RF frequencies can be selected for peaceful
    coexistence of different wireless technologies.

27
Interference
  • In the wireless world, anticipation of devices is
    very low, since any device can appear anytime
    anywhere.
  • How serious will the interference be?
  • How will devices maintain communication?

28
Interference in the 2400 MHz Band
  • Usage scenario is extended by adding an
    individual that enters the patients room using a
    Bluetooth device.
  • The Bluetooth device spans the entire frequency
    band. Overlap is inevitable with the WLAN or WPAN
    channels.

29
Walk in Usage Scenario
  • The simulation consists of the WPAN sensors
    carrying ECG traffic, which is collected and
    transmitted via the WLAN to a remote location.
  • When the walk in Bluetooth device is activated,
    the packet loss at the MAC sublayer of the low
    level WPAN monitor is measured for performance.
  • The loss came up to 60 at close range (0.5m)
  • Interference mitigation techniques are needed to
    tackle this issue.

30
Interference Mitigation Techniques
  • Two main categories
  • Collaborative require communication between
    heterogeneous protocol stacks.
  • Noncollaborative no direct communication between
    devices, rely on channel or network measurements
    to detect presence of other devices.

31
Noncollaborative Techniques
  • Two strategies are used to avoid usage of the
    same frequency
  • Time-Division Multiplexing (TDM) postpone
    transmissions till a channel is clear (reduce
    packet loss but increase delay)
  • Frequency-Division Multiplexing (FDM) allocate
    different portions of the frequency band to a
    specific group of communicating devices.
  • Neither of these can eradicate interference, and
    these techniques are triggered after the
    communication is impacted.

32
Mobility of Wireless Networks (I)
  • Main advantage of using wireless in healthcare is
    the ability to move those devices around.
  • Wireless technologies have to handle the movement
    of devices even when there is an ongoing
    communication.
  • In a hospital environment, the assumption is that
    the movement is in the hospital and at walking
    speed.

33
Mobility of Wireless Networks (II)
  • Two wireless devices are communicating directly
    (Cell phone and earset or ECG sensors and
    monitor)
  • Wireless devices are communicating through an AP
    (the patients bed moving out of the current
    coverage area of the current WLAN AP)
  • Handle interference effects and mobility
    management

34
Handover Management
  • Changing the point of attachment to the
    infrastructure
  • Layer 2 handover old and new APs share the same
    subnet.
  • Layer 3 handover the APs are connected to a
    different subnet

35
Layer 2
  • Discovery Phase
  • Passive waits for a beacon message sent
    periodically by the AP
  • Active send probe request messages, in which
    in-range APs reply to by a probe response message
  • Authentication Phase mobile nodes and APs
    exchange identities.
  • Association Phase exchange two frames to
    allocate an association identifier to the mobile
    node

36
Layer 3
  • Need to discover the information of the link
  • IPv6
  • Router Advertisement
  • Update location of the node with the link

37
Summary
  • Surveyed several wireless technologies
  • Used ECG as a user case for choosing the right
    technology
  • Deployment issues
  • Need to fully investigate the requirements of the
    medical application, and the functions of the
    wireless technology
  • Continuous evaluation
  • Trade offs for wireless networks

38
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