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Hoglund and Varga: Building a Reliable Wireless Medical Device Network

WLAN design may incorrectly place Wireless Access be used over the life of the WLAN. Today there are
Points (WAPs), WAP location modifications can eas- tools from such companies as Ixia (www.ixiacom.
ily be made in the field at the time of deployment. com) that allow end users and WLAN device manu-
When installing a WLAN, all operational settings facturers to assess the scalability of a WLAN. Given
are configured in a central WLAN controller that the new higher-speed WLAN standards, it is common
interfaces with the facility’s core network and allows to build and scale networks to thousands of users
for efficient network communication. In addition, to support data, voice, video, and WLAN-enabled
depending on the size of the WLAN, a separate WLAN medical devices.
management system may also be implemented to
• Two-way communication: Previous generations of
provide a single “pane of glass” for the management,
proprietary wireless communication for telemetry
monitoring, alarming, troubleshooting, reporting,
was unidirectional; WLANs offer two-way or bi-
and assurance of consistent configurations across
directional communication. Two-way communica-
multiple WLAN controllers. All of these improve-
tion supports the latest generation of patient-worn
ments make the implementation of a reliable LAN
monitoring devices. These devices send patient vital
and WLAN scientific and predictable.
signs data to the central monitoring station for display
• Interference: While RF interference is always a pos- and alarming, as did yesterday’s telemetry transmit-
sibility, the modern WLAN generally has spectrum ters, but they also display and alarm locally. So, if
analysis functions built into the network as a whole. the patient accidentally walks outside of the Wi-Fi
This allows for constant monitoring of the network for network coverage area, the patient will continued
any interference and acts to either issue an alarm to to be monitored locally. The caregiver is therefore
the network administrator or automatically mitigate able to monitor the patient without compromising
those specific interferers. As good design practice, the mobility of ambulatory patients.
an onsite spectrum analysis should be performed to
• Cost issues: Healthcare systems are under tremen-
determine any RF interferers present in the facility
dous cost pressures, so the more value that they can
in the 2.4GHz and 5GHz bands and their potential
realize from a technology investment, the better. In
impact.
the case of patient monitoring, this is yet another
• Reliability: Today’s WLAN is an intelligent network. application across which to allocate the fixed WLAN
Although WAPs have a mean time between failure cost. More than likely, the investment in the WLAN
(MTBF) of over ten years, this network can auto- was made for Bar Code Medication Administration
matically sense and alarm if a WAP fails or is not (BCMA), wireless voice-over-IP (VoIP), real-time
performing as expected. Good WLAN design practices location services (RTLS), and/or “smart” infusion
dictate overlapping adjacent WAP cells to ensure pumps. Adding WLAN-based patient monitoring
seamless client device roaming across the network. may add some small incremental costs, but this
Even if an individual WAP fails, radio output power in application can be amortized over a number years
adjacent WAPs can be set to automatically increase/ with the other applications to improve the return
decrease to ensure adequate coverage. In addition, on investment (ROI).
High Availability (HA) designs feature redundant
WLAN controllers that will failover in a seamless Wi-fi vs. WMTS cost comparison
fashion in the event of a network controller failure.
The costs of implementing patient monitoring on
• Scalability: In the past, understanding how the Wi-Fi are significantly less than on a WMTS network.
WLAN client density may increase was a challenge. The following cost comparison tool provides a general
WLAN designs must anticipate the potential number indication of costs involved.
of client devices such as patient monitors that will

J Global Clinical Engineering Special Issue 1: 42-49; 2018 44