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Prevailing over Wires in Healthcare Environments: Benefits and Challenges

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. Introduction.

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Prevailing over Wires in Healthcare Environments: Benefits and Challenges

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  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 patient’s 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 (< 1m) • Personal area (< 10m) • Local area (< 100m) • Wide area (> 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 AP’s 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 -> mains • WPANS -> 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 patient’s 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 patient’s 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. Questions?

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