Like
VoIP,
VoWLAN contributes to cost efficiency. Because calls can be
routed over the data network internally or over the Internet
externally, mobile telephony costs can be eliminated or decreased
significantly. In the long term, VoWLAN deployment is a significant
step toward interoperability and seamless mobile connectivity
between private WLANs and public wireless and cellular
networks.Table of contents
UNDERSTANDING VoWLAN
- VoWLAN
basics:
A SearchVoIP.com member asked us to explain the basics of VoWLAN.
Read what our expert had to say.
VoWLAN
CASE STUDIES
UNDERSTANDING VoWLAN
VoWLAN
basics
Question: I know this is basic but want to know how VoWLAN
works. How do you see it in the future? I am new to this and would
like to learn.
Answer: If you notice, I always refer to "VoWLAN" as
"wireless VoIP". That is because that is all it is! Basically, a
model called the Open Systems Interconnection (OSI) model governs
all networking. The model defines different layers of networking
and sets them up such that you can use different technologies at
each layer without worrying about the layer above or below the one
you are addressing.
Now, IP is a "Layer 3" technology and is used to encapsulate
digital voice so that it can be transported. "Wireless" or, in the
case of VoWLAN, "802.11", is a "Layer 2" technology. Therefore
VoWLAN is simply Voice over IP over 802.11 wireless Ethernet. When
people refer to regular VoIP it can be running over Ethernet,
SONET, Token Ring, T-1s, whatever. The underlying transport does
not matter and that is the simplistic elegance of the OSI
model.
Net-net: VoWLAN is simply VoIP running on a wireless local area
network. Someone slapped the acronym together because that is the
nature of High-Tech – everything needs a catchy acronym.
VoWLAN: Preparing
your network for a voice over wireless LAN deployment
It is worth upfront time and effort to prepare for a voice over
wireless LAN (VoWLAN) deployment. Otherwise, if your VoWLAN
implementation does not deliver the call quality your users have
come to expect, it will be judged a failure.
Based on their experience with the wired network, users'
expectations are very high: calls without excessive noise,
momentary dropouts or disconnects in mid-call.
Planning a successful VoWLAN deployment involves three main
elements:
- Analysis of the radio frequency environment.
- Review of network security.
- Investigation of the wireless vendor's voice experience and
product features.
Analysis of the radio frequency environment
Meeting call quality goals requires maintaining a consistently
strong signal throughout your facility. The first step is a
comprehensive analysis of your facility's radio frequency (RF)
environment, which requires:
- Tools designed specifically for the task.
- Personnel with the expertise to understand the
results.
Any wireless deployment should include an RF analysis, but a
VoWLAN deployment also requires the analysis to cover areas of the
building that may not have been considered in an earlier wireless
deployment (e.g., stairwells or even restrooms), because voice
users expect to be able to make or continue calls from anywhere in
the building.
"Implementing Wi-Fi for VoIP today demands a level of
engineering expertise that goes well beyond what is needed for
email and Web surfing," said Joe Bardwell, chief scientist at
Connect802 Corp. of San Ramon, California. "The characteristics of
a voice call make it necessary to focus on a careful RF analysis of
the entire facility and on manufacturers' key specifications for
call quality, rather than simply focusing on 802.11 data rates the
way one would for simple Internet connectivity."
RF analysis for any wireless deployment requires use of a
spectrum analyser to measure signal strength. Analysis for VoWLAN
should also include measurement of
R-value, a measure of call quality developed
by the International Telecommunications Union (ITU). Specialised
tools to measure and display R-value are available from vendors
such as AirMagnet and
Veriwave.
The R-value measurement includes:
- Factors resulting from signal quality -- for example,
signal-to-noise ratio and single and burst packet loss.
- End-to-end delay, jitter and codec characteristics that are the
result of overall network design and the choice of wireless
equipment and phone handsets.
Review of network security
Security is a vital concern in any wireless deployment, but
VoWLAN creates new vulnerabilities. Many currently available
handsets support only the
WEP security standard, which has proven to be insufficient
protection against intruders. Intruders may crack a WEP password
simply to make free phone calls at your expense, but the goal may
also be to access your corporate data.
How can you address network security in planning? You may need
to add new tests to your ongoing set of penetration tests to make
sure your network is not vulnerable to this added threat. For the
future, look to the WPA2 standard to provide a much higher level of
protection. Handsets supporting WPA2 are just now becoming
available.
Investigation of the wireless vendor's voice experience and
product features
Key considerations in vendor selection should include:
- Support for IEEE standard 802.11e or equivalent Quality of
Service (QoS) technique.
- Call admission control at access points.
- Security features.
Meeting latency and jitter requirements involves prioritising
voice traffic above data. IEEE standard 802.11e, finalised in late
2005, adds QoS features to the previous 802.11 standard. Some
vendors have now implemented the standard, but others continue to
use nonstandard methods that may be equally effective. If possible,
test your vendor's performance under realistic conditions. If
running your own tests is not possible, review tests done by a
third party.
Access points (APs) can maintain acceptable call quality only by
limiting the number of simultaneous calls. From your vendor, find
out the following and compare with your expected usage:
- How many calls each AP can handle; compare.
- Whether an AP will continue to accept calls even though the
quality is dropping, or whether it will reject calls beyond what it
can handle with high quality.
Some vendors have added security features intended to address
vulnerabilities that come into play with voice. For example, some
wireless controllers contain a firewall that identifies a voice
call and protects against any attempt to access resources that are
not appropriate for a phone call. Find out how your vendor
approaches this problem.
Some architectures require re-authentication every time a caller
roams from AP to AP, which may result in an unacceptably long gap
in the conversation. Other products perform a single authentication
in a central controller and exhibit no delay when roaming. Test
your vendor's product to determine how it handles roaming.
Adding voice to an existing wireless network may seem easy, but
without a careful analysis of your RF environment, network security
and your vendor's product capabilities, the result may be unhappy
users and possibly a network break-in.
VoWLAN CASE STUDIES
VoWLAN system analysis improves hospital's
productivity
For one hospital, voice over wireless local area networks (VoWLANs)
was a choice that helped staff members -- nurses in particular --
save time and ease stress loads, once other interference issues had
been resolved.
For the employees of Wake Forest, the VoWLAN technologies
offered through Vocera held out the promise that they could save
time tracking down the right nurse when a patient needed attention
or locating a wheelchair and bringing it to a specific room. In the
first several buildings of the Wake Forest campus, implementation
of Vocera went fairly smoothly, and employees were soon seeing the
promised results of the new solution.
Resembling a Star Trek communication badge, the Vocera badge
uses VoWLAN and voice recognition technologies to improve the
communications of mobile workers in on-campus environments.
Pressing a button causes the badge to call the system operator.
After that initial action, all other commands are executed by
voice, and the user is free to tell the operating system to call a
specific person or department as needed. The call is connected to
the recipient, who can accept or cancel the call with a voice
command.
The field engineers at Vocera began to use Cognio's
SpectrumExpert, a tool that analyses the wireless spectrum to hunt
down problems. Vocera had already been using the SpectrumExpert for
two years. Running the software on their laptops, the field
engineers were able to pinpoint the device that was causing the
interference with the hospital staff's voice communications.
It turns out that the interference was coming from a legacy
patient monitoring system, and it caused the Vocera solution to hop
frequencies as it tried to find the best frequency to work on.
There was also frequency hopping from interference from the
neighboring buildings, though that was the easier of the two issues
to resolve.
Owing to the complexities of testing medical equipment, however,
Wake Forest is still evaluating whether it will use the Vocera
solution in that particular building -- it continues to use it in
other buildings -- and whether it will replace the legacy patient
monitoring system. The early and continued success of the Vocera
VoWLAN solution in the other buildings presents a strong case for
its continued and campus-wide use.
By utilising the wireless technologies of the data spectrum,
many enterprises are finding they can place their voice
communications onto the wireless data network, wireless local area
networks (WLANs), and create a more effective communications system
for campus environments, where the majority of employees are
constantly on the go.
Industries such as healthcare, hospitality and retail are more
inclined to be looking for solutions such as VoWLAN. With a
primarily mobile workforce, locating and contacting the right
person at the right time can be difficult in these settings. As
VoWLAN technologies continue to develop, solutions that allow a
specific nurse, doctor, salesperson or manager to be located either
within the campus or through a voice system are becoming more
practical and prevalent.
VoWLAN, IP DECT devices
connect campus nomads
VoWLAN and IP DECT devices, unveiled this week by Avaya, are
targeted at the latest breed of mobile workers: the campus nomads
who do not leave the workplace but are rarely at their desks.
This new type of mobile worker, who is mobile within the
boundaries of a distributed enterprise, has needs different from
those of the typical teleworker, remote worker or road warrior. In
many cases, it does not make sense for companies to pay for mobile
devices and cell phones for workers who only need connectivity
while on the enterprise campus.
Recent data from Juniper Research suggests that Voice over WLAN
(VoWLAN) sales to enterprises will grow over the next five years,
jumping from $2 billion this year to $15 billion by 2012.
According to Terry Robinson, an Avaya director of product
management, workers who are nomadic while on campus will fuel a lot
of that VoWLAN growth.
Robinson said the Avaya 3641 and 3645 VoWLAN handsets, announced
this week, are rugged IP wireless devices designed for industrial
environments such as warehouses and hospitals. The devices, which
keep workers connected using VoIP over the wireless LAN, support
802.11 a/b/g and enhance voice quality through reduced wireless
interference. The devices allow push-to-talk functionality for
instant communications and can be integrated with third-party
applications such as messaging, nurse call systems and alarm
alerts.
Another VoWLAN handset, the Avaya 3631, features a color display
and uses 802.11 b and g WLANs. It is designed to be easily
installed on any WLAN network.
Along with the new VoWLAN devices, Avaya this week released a
handset that uses IP Digital Enhanced Cordless Technology (DECT).
The Avaya 3711 uses IP DECT, which was recently ratified by the FCC
for use in North America. IP DECT is a voice-optimised alternative
to Wi-Fi, offering scalable and secure wireless voice
communications using cordless technologies. DECT, according to some
experts, is ideal for organisations that do not want to commingle
voice and data on the same wireless network, ensuring that voice
communications receive top priority. With so much traffic already
traversing the WLAN, IP DECT provides a way to keep voice separate
while also eliminating some of the congestion on the WLAN.
IP DECT, Robinson said, encrypts voice traffic. Where the
wireless LAN mixes data and voice traffic, a DECT network optimises
voice while also allowing for alerts and SMS messaging. Instead of
a wireless access point, which VoWLAN devices use, IP DECT uses a
radio fixed port, which functions as an access point.
These new devices are for all types of internally mobile
workers, including warehouse supervisors, corporate managers and
healthcare workers. The education market is also key, Robinson
said, especially because of its high demand for mobile
communications.
One education user, Kansas State University, needed mobile video
communications so that personnel could be productive while
traversing its large campus, which consists of approximately 100
buildings.
Linda Grubbs, one of the university's end users, has taken on
the Avaya 3631 VoWLAN handset.
"I often leave my desk to handle all different types of errands
across campus," Grubbs said. "With my old wireless phone, there
were too many steps to take to manage communications when I left my
desk."
"[The new device] makes it simpler to conference call,
speed-dial or manage multiple lines while I am roaming on campus,"
she added. "It makes my job so much easier."
Along with its in-building wireless capabilities, Kansas State's
mobility also goes outside campus walls, using the Avaya Extension
to Cellular, which lets mobile workers receive incoming desk calls
on their cell phones. For example, an end user who leaves campus
can receive any call that comes into his desk phone.
Kansas State was guided through its VoWLAN deployment by SKC, an
Avaya Authorised Business Partner. SKC offered support and counsel
during the university's beta testing phase.
"Businesses require their employees to be increasingly mobile –
their success relies on it," said Geoffrey Baird, Avaya's vice
president and general manager of applications, mobile and small
systems division. "This in turn drives the demand for devices that
make individuals more productive even while not at a desk."