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Understanding VoWLAN

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.

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.

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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's 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 (more info here

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 doesn't matter and that's 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 doesn't 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's 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 analyzer 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). Specialized 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 prioritizing voice traffic above data. IEEE standard 802.11e, finalized 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 isn't 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 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 analyzes 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 utilizing 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 don't 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 doesn't 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's 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-optimized alternative to Wi-Fi, offering scalable and secure wireless voice communications using cordless technologies. DECT, according to some experts, is ideal for organizations 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 optimizes 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 Authorized 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."

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