Cover Story
Wireless Prescriptions
Wake Forest University Baptist Medical Center installs a
900-access-point WLAN to mobilize electronic patient
charting and to gain valuable time savings.
WFUBMC staff in the PACU with an x-ray machine that transfers images rapidly
via the wireless LAN. Chuck Ware, director of computer and communication services,
is second from left. Bill Masten, senior network systems analyst is far right.
Hardwired
communications and computing devices are
no longer the preferred tools of the
trade for doctors and nurses at Wake
Forest University Baptist Medical Center
(WFUBMC) in Winston-Salem, N.C. That is
because the academic health system has
gone wireless.
The 1,300-bed
facility-comprising North Carolina
Baptist Hospital, Wake Forest University
School of Medicine and Brenner
Children's Hospital-concluded that a
campus-wide wireless network would give
medical staff faster and easier access
to patient records via its electronic
medical records (EMR) system.
"We realized that our
caregivers are highly mobile and need
devices that match their behavior,"
explains Chuck Ware, director of
computer and communication services at
the medical center. "They were losing
continuity of patient care when they
traveled between locations using cabled
PCs and phones."
For example, doctors
and nurses consult and update patient
charts continually as they roam among
inpatient, outpatient, office and
research lab facilities scattered
throughout 16 buildings. Having
electronic access to patient information
frees them from having to constantly
return to a nurse's station or hunt down
a given patient's paper chart and
manually update it.
The medical center
installed a 900-access-point (AP)
wireless LAN to mobilize the electronic
patient charting and to gain valuable
time savings with a direct, wireless
patient-to-nurse call system and
wireless connections for ultrasound
equipment. The WLAN spans about two
million square feet, stretching across
inpatient, outpatient, post-anesthesia
care and other critical areas, as well
as the medical school lecture halls. A
Meru Networks WLAN replaced the previous
wireless system, and has become the
first WLAN to cover all the other areas.
Going all wireless
in the medical school's two 120-seat lecture halls eliminated about $72,000 in cabling costs.
The initial 400 APs
took about a month to install, says Mike
Jarvis, lead network systems analyst.
The job was completed quickly because
the cabling was already in place to
connect APs to the medical center's
wired Cisco Catalyst switches, which
power the radios using standard 802.3af
power-over-Ethernet (PoE) technology.
The second and third deployments each
added about 250 APs and took about three
months, because they required installing
AP-to-switch cabling.
The project, to date,
has cost just under $900,000, comprising
mostly Meru AP208 dual-radio 802.11a/b/g
APs. In addition, 15 Draft 2.0
802.11n-compatible Meru AP311 APs serve
crowded lecture halls and
bandwidth-intensive, high-resolution
imaging areas, such as ophthalmology
outpatient clinics. The medical center
has deployed eight Meru MC3150
management controllers, which support up
to 150 APs each, in its data center.
SAVINGS WITH WIRELESS
From a business
perspective, going all wireless in the
medical school's two 120-seat lecture
halls eliminated about $72,000 in
cabling costs. The wireless network also
reduced the number of switch ports that
would otherwise have been necessary for
each laptop's Ethernet connection in the
lecture halls. With each port costing
about $100, capital expenses dropped
about $24,000.
Choosing a wireless
technology to deliver caregiver mobility
was not a given, says Ware. One
obstacle: The medical center had to
consider potential interference with its
patient monitoring systems.
"Some of our
monitoring equipment is older, so
cellular signals interfere with it. In
intensive care areas, for instance, we
still have to turn off cell phones,"
says Ware.
WFUBMC dismissed the
cellular option partly for that reason
and also because it did not want to pay
airtime voice charges for mobile
personnel using cell phones throughout
their shifts, he adds.
Having turned its
attention to Wi-Fi, the medical center
then had to account for a number of
facility-wide Philips portable patient
monitoring systems that support
frequency-hopping spread spectrum (FHSS)
technology. FHSS is an older method of
transmitting radio signals that rapidly
switches a carrier among many 1-MHz
frequency channels using a sequence
known to both transmitter and receiver.
The Philips equipment operates in the
2.4-GHz frequency band, the same band
used by 802.11b and 802.11g Wi-Fi
networks in 22-MHz chunks.
In short, the medical
center needed a Wi-Fi system that could
segregate its wireless communications
traffic from the Philips monitoring
traffic as much as possible to minimize
interference. So it first set aside the
2.4-GHz band for its internal voice
traffic, as well as for guest- and
patient-generated public Internet access
traffic. Internal data traffic runs
across an 802.11a network in the 5-GHz
band, so there is no interference
between internal data and the voice and
other traffic in the 2.4-GHz band.
From there, the
medical center deployed the Meru
single-channel-based Wi-Fi system. The
architecture allows dense deployment of
APs on the same channel to eliminate
co-channel interference. There are three
non-overlapping channels in the 2.4-GHz
band. With WFUBMC dedicating one Meru
channel to Wi-Fi voice and for guest and
patient Internet access, two free
non-overlapping channels are left in
which the Philips equipment's frequency
hopping behavior is not a problem-as it
would be in a traditional micro-cell
environment that uses all three channels
concurrently.
CHANNEL INTERFERENCE STOPPED
The Philips system
can use adaptive frequency hopping to
detect and avoid channels already in
use. As a result, the hop pattern
largely avoids the Meru channel
dedicated to Wi-Fi and rarely
interferes, says Bill Masten, senior
network systems analyst.
In addition, WFUBMC
implemented a Meru system-management
feature called Virtual Cell to eliminate
network latency as users roam. This
feature allows client devices-such as
mobile telephones, laptops and tablet
computers-to associate with a "logical
AP" that is represented by a single
media access-control (MAC) address
belonging to a centralized Meru MC3150
controller.
The controller
manages the physical APs and decides,
based on current network-wide
conditions, which physical AP a client
connects to when it joins the network
and moves around. This setup allows
client load-balancing among APs to avoid
congestion. It also eliminates physical
AP-to-AP session handoff and the
associated delays that would otherwise
interrupt sessions as employees roam.
The two other
wireless LAN systems WFUBMC evaluated
were based on micro-cell, multichannel
architectures. Using these designs, the
Wi-Fi network maps APs onto a
checkerboard of alternating,
non-overlapping channels (channels 1, 6
and 11 in the 2.4-GHz band). In such a
setup, the FHSS sequence would interrupt
all channels at some point, notes
Jarvis.
Management
considerations also played a part in the
choice of Meru's single-channel
approach. "In a typical micro-cell
environment, each AP has to be on a
different channel," explains Jarvis.
"With an installation this size, it
would be a nightmare to keep track of
all that."
Nurses have pared
minutes off per-patient response times
by responding directly to patients who
call them on Wi-Fi telephony devices.
The average caregiver-to-bedside arrival
time has dropped as a result, from about
7.5 minutes to 2.5 minutes, according to
Ware.
"And if the patient
can tell the nurse exactly what the
issue is, the caregiver can show up
armed with the appropriate supplies," he
notes.
IMPROVED VOICE QUALITY
The single-channel
architecture and Virtual Cell
capabilities are critical for retaining
voice quality, says Jarvis, as is a
feature in the Meru system-management
software called airtime fairness.
Airtime fairness guarantees client
devices on the network equal usage of
the airwave medium in terms of
transmission time, precluding voice
calls from being knocked offline by a
slow data transmission.
"Virtual Cell lent
itself to higher MOS during testing,"
says Jarvis. MOS, or mean opinion score,
is a numerical indication of the
perceived quality of a call. Scores
range from one to five, where one is the
lowest perceived quality. Meru scored
above four, considered landline quality,
while the previous vendors' MOS scores
fell below that, Jarvis says.
"I can literally run down the hall with the phone and retain the call. There are zero drops." - Bill Masten
"For quality voice
calls that avoid jitter and latency, you
need a single virtual MAC address," adds
Ware. "If voice sessions have to change
MAC addresses as users roam, the extra
process adds latency."
Hospital personnel
typically roll carts carrying ultrasound
devices from a fixed imaging area to the
intensive care unit and scan five or six
patients during one session.
Historically, they have then rolled the
cart back to the imaging area, set it up
again, and transferred the images for
physicians to view.
The back-and-forth
hauling is necessary because the
ultrasound equipment must be configured
with a static IP address that binds it
to a particular subnet. If the equipment
cart is moved to a location that does
not support access to that subnet, it
cannot connect to the wired network and
transfer images, Masten explains.
With the static IP
address subnet limitation, two hours or
more might be necessary before the
images could be uploaded for the doctors
to view using the wired network.
Getting wireless
connections to ultrasound equipment
required some resourcefulness.
Ultrasound units arrive from the factory
with wired Ethernet network interface
cards but no wireless connections. As a
result, WFUBMC installed a wireless
bridge to extend the Ethernet connection
to the WLAN.
Now, the ICU's
Ethernet connection links to a wired
switch, which connects to the wireless
bridge configured with a subnet mask
that transcends about 2,000 hosts across
the entire campus. "As soon as you
finish the first scan you can send it
and doctors can view it. Speed is
particularly important for ICU
patients," says Masten. The image
delivery time has been cut from about
two hours to half an hour.
Some caregivers wear
wireless telephony badges, which support
speech recognition, for the hands-free
ability to place and receive
voice-activated calls. In certain areas
of the facility, however, the badges do
not transmit at a high enough power to
avoid dropped calls, says Ware.
To combat this
problem, Ascom Wi-Fi telephony handsets
were deployed, transmitting a stronger
signal. Because there are no physical
handoffs from AP to AP in the Meru
infrastructure, "I can literally run
down the hall with the phone and retain
the call," says Masten. "There are zero
drops."
CHALLENGES REMAIN
A current challenge,
though, is that the Ascom handsets do
not support voice recognition or
Bluetooth, which would allow caregivers
hands-free operation as they juggle
patients, equipment, medications and
supplies. On the data side, too, the
biggest challenge is finding the right
device for caregivers. Ware explains
that personal digital assistants (PDAs),
for example, have screens that are too
small to support chartless rounds, and
because of their size, have a weak radio
signal.
"But laptops are too
cumbersome to lug around," Ware says. As
a result, the organization is testing
Wi-Fi-enabled tablet computers from
Dell, Fujitsu, Motion Computing and
Toshiba, which combine the bigger
display of a laptop with the greater
portability of a PDA.
For now, WFUBMC is
running primarily 802.11a/g network
traffic and has just started testing
Draft 2.0 802.11n products from Meru.
802.11n is a still-emerging IEEE
standard that uses special antennas and
multiplexing techniques to fit more
traffic over a given wireless channel.
Current connect rates per radio in early
802.11n equipment are 300 Mbps;
real-world throughput is typically less,
depending on distance and environmental
factors.
In the near term,
WFUBMC will use 802.11n in 2x2 mode,
which means that two AP transmitting
antennas and two AP receiving antennas
exchange separate, multiplexed streams
of data. Other modes are also available
from Meru that could increase
throughput, but require increased power.
Jarvis explains that
the organization recently spent about
$225,000 to upgrade to 802.3af and
cannot justify replacing that gear with
yet another power
infrastructure-particularly since
running 2x2 on 802.3af power "works just
fine, and we'll have legacy 802.11g
devices for a long time, anyway."
The medical school,
in particular, needs 802.11n, and Meru
11n equipment has already been installed
in the school's lecture halls and
conference rooms. "There is a new class
of students coming in that will all have
11n client devices," explains Tonya
Suttles, senior network systems analyst.
"Also, as an infrastructure planner, you
have to stay a little ahead of things.
We have a three-year equipment lease; if
we didn't get 11n, we would regret it a
year or two into the lease."
Ware recommends a
thorough upfront physical site survey,
particularly if there are varied types of
construction in the facility. "For example,
in the radiology/MRI area, we have shielding
in walls that affects the wireless signal,"
says Jarvis.
He adds that prestaging
the APs is "very easy to do remotely with
Meru's EzRF management system by using the
AP redirect feature." As soon as a new AP
comes on line, the primary controller can
redirect the AP to a different controller
based on either the subnet on which the AP
is installed or the AP's MAC address. If the
number of APs associated with a given
controller is close to the licensed limit,
the primary controller will tell the new AP
being installed to associate with another
controller, and redirect it to the IP
address of the new controller.
Labeling all the AP locations according
to information on the floor plan is also
advised, "because that is what you will see
in EzRF," adds Masten. "By sticking to the
floor plans, we gain a consistent view of
the WLAN for coverage, asset management and
fault management within EzRF."
For more information
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About Meru Networks
Ihab Abu-Hakima
Meru Networks develops and markets enterprise wireless infrastructure solutions for major Fortune 500 companies, universities, healthcare organizations and local, state and federal government agencies. Meru products deliver predictable bandwidth and wireless service fidelity for business-critical applications and converged voice and data services in the emerging all-wireless enterprise.
Ihab Abu-Hakima, a 25-year veteran of the computer and communications industry, joined Meru in January 2005 as president and chief executive officer. Hakima has an M.B.A. degree and a degree in electrical engineering, both from McGill University in Montreal.