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The role of VoWLAN solutions

Learn about voice over wireless LAN (VoWLAN) deployment from specific case study applications. This chapter excerpt details specific instances of VoWLAN deployment success.

Deploying Voice over Wireless LANs
Chapter 1, VoWLAN Applications and Benefits

VoWLAN systems are an extension to wired VoIP systems and an alternative to traditional analog and digital voice communications. VoWLANs offer significant benefits of providing mobility and wirelessly converging voice with data applications. With VoWLANs, hospitals, enterprises, retail stores, warehouses, and home owners can reduce telephony costs and enable mobile applications.

This chapter describes various applications of Voice over Wireless LAN (VoWLAN) systems. Real-world examples and case studies provide you with a solid understanding of how VoWLAN can benefit a company. Details are also given about tangible benefits and expected return on investment (ROI).

Deploying Voice over Wireless LANs
Table of contents:
The role of VoWLAN solutions
Determining VoWLAN solution ROI

The role of VoWLAN solutions

VoWLAN systems are an extension to wired VoIP systems and an alternative to traditional analog and digital voice communications. VoWLANs offer significant benefits of providing mobility and wirelessly converging voice with data applications. With VoWLANs, hospitals, enterprises, retail stores, warehouses, and home owners can reduce telephony costs and enable mobile applications.

Examples of the systems that VoWLANs can replace include the following:

  • Wired telephones
  • Cellular telephones
  • Two-way radios

With VoWLANs, people can use VoWLAN phones to communicate by voice wirelessly with others inside and outside a facility. The experience is very similar to using a traditional wired telephone, except the user is free to move about the building. Furthermore, a VoWLAN phone can operate from many of the growing Wi-Fi hotspots, enabling a person to make use of the same mobile phone while within or away from the office or home. Some cellular phones incorporate VoWLAN capability, which enables users to make calls over traditional cellular networks when no wireless local-area network (wireless LAN) is available.

The optimum approach to configuring your VoWLAN depends on user requirements and existing telephone hardware. The local-only configuration, which is similar to two-way radios, consists of a wireless LAN that merely enables a user to talk to other users directly connected to the network. This supports a mix of wireless and wired VoIP telephones. For example, a clerk looking for a part in a warehouse may use a VoWLAN handset to communicate with a manager sitting at a desk and using a wired VoIP phone.

More advanced VoWLAN systems, however, allow users to place actual telephone calls from their VoWLAN handsets. The telephone traffic can travel over the Internet or the Public Switched Telephone Network (PSTN). With these two models, the use of the system is virtually the same as a traditional telephone. For example, a sales agent in her home office in Ohio may dial a phone number on her VoWLAN phone to call a customer in California.

The primary benefit of VoWLAN solutions is cost savings. For instance, according to recent studies, federal, state, and local agencies could achieve savings of $4.5 billion annually by making telephone calls over the Internet. In addition, VoWLAN systems are easier to deploy and allow flexible communications. VoWLAN plays a critical role in realizing these savings by mobilizing the workforce.

History of VoWLANs

The two primary technologies of VoWLANs are wireless LANs and VoIP. Both have been evolving over the past decade and are now stable enough to support wireless voice communications.


The earliest indication of VoIP systems was in the mid-1990s, when Vocaltec, Inc. released Internet Phone Software. This software ran on PCs and translated voice signals into digital packets that could be sent over the Internet. Both the sending and receiving callers must use the same software. Sound quality was not as good as traditional telephones, but long distance calls could be made for free.

Throughout the late 1990s, entrepreneurs began establishing gateways and switches to allow people to make free phone calls over the Internet using standard telephones. The users had to utilize a PC to set up the call, but then they were free to talk from standard wired telephones connected to a PC. With these systems, the VoIP market began evolving. Many companies, including Cisco, began selling VoIP equipment about the year 2000 to enterprises to converge voice and data and provide mobility.

Wireless LANs

In the early 1990s, the first wireless LAN products, NCR WaveLAN and Motorola Altair, appeared on the market. At this time, there were no applicable standards and prices were relatively high, at around $1,500 per wireless adapter. As a result, only companies having applications with significant benefits from wireless connectivity, such as inventory management and price marking, could afford to deploy wireless LAN solutions.

In 1997, the Institute of Electrical and Electronics Engineers (IEEE) ratified the first version of the 802.11 wireless LAN standard. 802.11 at this point provided up to 1Mbps and 2Mbps data rate operation in the 2.4GHz frequency band using direct sequence and frequency hopping, which are both spread spectrum technologies. The capacity of these first 802.11 solutions was not good enough to effectively support voice applications.

To enhance the performance of wireless LANs, the IEEE ratified the 802.11a and 802.11b standards in 1999. 802.11a provides up to 54Mbps data rates in the 5GHz band using orthogonal frequency division multiplexing (OFDM). 802.11b extends the maximum data rates of the initial 2.4GHz direct sequence 802.11 standard to 11Mbps. Later, in 2004, IEEE released 802.11g, which further extends data rates in the 2.4GHz band to 54Mbps using OFDM. The higher data rate 802.11 standards, 802.11a, 802.11b, and 802.11g, offer adequate capacity for supporting VoWLAN applications. 802.11a, however, provides the highest capacity, mainly because the Radio Frequency (RF) channels in the 5GHz band do not overlap with each other as they do in the 2.4GHz band. 802.11n, which will offer 100Mbp or more performance, is nearing ratification.

Other recent improvements to the 802.11 standard include security (802.11i), which includes much stronger encryption and authentication mechanisms than the initial standard. The use of Temporal Key Internet Protocol (TKIP) and Advanced Encryption Standard (AES), along with 802.1i protocols, makes wireless LANs very secure. Also, the ratification of the 802.11e standard in 2006 offers quality of service important for VoWLAN applications.

Within the past couple of years, the prices for wireless LAN adapters have decreased to well under $100 each. This dramatic drop in prices has fueled the proliferation of wireless LANs for a variety of applications in all markets. The Wi-Fi Alliance has also been actively promoting wireless LANs through the Wi-Fi brand and mandating interoperability testing.

Because of the proliferation of wireless LANs, VoWLAN solutions are also proliferating. Companies offering VoIP equipment, such as Cisco, have been marketing VoWLAN phones that interface with their digital telephony systems. Even service providers, such as Vonage, now offer Wi-Fi phones that interface with their Internet Protocol (IP) telephony service.


Hospitals were one of the first users of VoWLAN solutions, such as Vocera, mainly because of the significant need for effective communication among high-valued medical staff. The ability for doctors and nurses to respond quickly with verbal instructions is crucial for saving the lives of patients. For example, Children's Hospital in Madera, California, uses a VoWLAN system to support push-to-talk features on its VoWLAN phones to broadcast Code Blue alerts that summon emergency teams. Patients receive a higher level of care, which leads to faster recovery. VoWLAN systems allow hospital staff to not waste time looking for a phone to use.

An issue with deploying VoWLANs in hospitals, though, is the difficulty in providing adequate wireless LAN coverage. Hospitals include x-ray rooms surrounded by lead, irregular metal objects, and unpredictable traffic flows of people. These factors lead to significant signal impairments. In addition, RF interference from other wireless systems operating in the 2.4GHz band, such as frequency-hopping spread spectrum devices, can cause degradation in performance. As a result, installers must conduct thorough RF site surveys when identifying optimum placement of wireless access points.


Enterprises are taking advantage of VoWLAN applications to provide mobility to workers and reduce costs through a common network infrastructure for voice and data. In many cases, enterprises implementing VoWLAN are doing so as an extension to wired VoIP systems. A company, for example, can equip the majority of the employees with a wired VoIP desk phone, and VoWLAN handsets are given to the employees needing mobility. Certainly the benefit of going wireless is that users can carry their phone with them throughout the facility, which enables them to respond faster to customer needs and functions within the company. The use of VoWLAN phones also eliminates the costs associated with rewiring telephone lines when employees change offices.

Enterprise executives making the decision to spend money on the necessary hardware and services need solid numbers before committing funds. An issue with deploying VoIP, and especially VoWLAN, in enterprises, however, is accurately predicting ROI. Assessing the returns a company will achieve by enabling faster response to customer needs, for example, is difficult. A company must be capable of achieving significant productivity benefits before moving forward with a VoWLAN deployment.


A university environment is highly mobile, with teaching staff and students moving along different classrooms, libraries, and offices. The use of VoWLANs at a university offers tremendous benefits by enabling university staff to stay in touch from anywhere on campus. This capability makes teachers more accessible to students, and the learning environment is much safer. A teacher, for example, can report safety issues as they occur, rather than having to wait until a class ends.

Excerpted with permission from Deploying Voice over Wireless LANs, by Jim Geier, Copyright 2007. For more information about this book and other titles, please visit Cisco Press.

A challenge of deploying a VoWLAN system at a university is that coverage must include a wide variety of buildings and outdoor areas. An extensive RF site survey is very important to take into account the varying facility construction and obstacles blocking radio waves. Even after installing the system, reevaluating coverage from time to time is generally necessary to determine whether student traffic and campus functions offer major signal attenuation.


To satisfy the needs of customers and staff, retail store managers must be accessible from anywhere within the store. Voice communications with these managers is crucial in providing customer satisfaction. For example, a customer may need to replace a part found broken when putting together a newly purchased bicycle, or someone may need to know the status of a shipment of a particular brand of dog food. Whenever the need arises, immediate communication with the store manager is necessary, and customers cannot be kept waiting, or they will shop somewhere else. In this type of environment, VoWLAN really shines. In many cases, the retail store already has an existing wireless LAN, and the store managers and staff can benefit from low-cost telephony.

Retail stores use existing wireless LANs to support bar code applications, such as price marking and inventory management. These applications make the deployment of VoWLAN systems in retail stores more of a plug-and-play situation. The existing wireless applications, however, generally have very low capacity requirements, and the access points already in place may not be capable of supporting the much higher bandwidth demands of voice communications. For example, a store may only have a wireless LAN based on the initial 802.11 standard, such as direct sequence spread spectrum supporting up to 2Mbps data rates. This particular store would need to upgrade its access point hardware to at least 802.11b, which introduces costs for hardware and services in addition to purchasing the wireless handsets.


Warehouses involve a host of functions where VoWLAN systems can provide significant benefits. Clerks end up being scattered throughout the warehouse facility, which can be quite expansive, and communication with other clerks and managers is essential to perform various functions. In most cases, having the clerks and managers meet face-to-face to communicate is not practical. In fact, being able to even find each other is often not possible, due to the numerous rows of bins and products. For example, an order may come in for the shipment of a particular item to a customer. Rather than waiting for a clerk to return to the main office, having the shipping department call a clerk directly and have him pick the item is much faster and more productive.

As with retail environments, many warehouses already have existing wireless LANs. However, because these wireless networks primarily support relatively low-performance bar code solutions for implementing inventory management functions, the wireless LAN may not have enough capacity to support a large number of VoWLAN phones. A company must analyze the wireless LAN and ensure that adequate data rates, signal strength, and roaming exist to support wireless voice applications.


In manufacturing facilities, line supervisors monitor production lines, and managers must be able to contact each other and other employees immediately to check the status of various operations and solve problems that regularly arise. A division manager in charge of a particular business unit, for example, is certainly anxious to ensure that the plant is getting products ready to ship in time to make revenue numbers. If a part of the orders for that period is at risk of not being completed in time, fixes can be considered and put in place to keep manufacturing on schedule.

A VoWLAN system makes communications in manufacturing extremely beneficial because managers are constantly on the move. In many cases, a manufacturing plant will have an existing wireless LAN in place, making the deployment of a VoWLAN extremely feasible. Even if the installation of wireless access points is necessary, the VoWLAN solution is still worthwhile because of the monetary benefits associated with immediate communications. In this situation, the value of the company to shareholders depends on effective communication among stakeholders in the manufacturing process. A VoWLAN solution allows managers to communicate immediately and solve problems to keep production in line with sales.

Small offices and homes

Many small offices and homes are installing wireless LANs to support mobile access to common Internet applications. Service providers, such as Vonage, are strongly advertising the capability of using the Internet for making phone calls to augment or replace standard PSTN telephones. Home and small-office owners are taking advantage of Internet telephony to save money on long-distance phone calls.

The use of VoWLAN is further extending the benefits of VoIP by providing mobility and even replacing the need for a cellular phone. A consumer is likely to select a VoWLAN solution as compared to wired VoIP service to enable mobility similar to what cordless phones offer. Someone can take the phone around the house and talk while doing house chores.

A single access point can easily support most home and small-office voice applications. Range is sufficient for the entire home, and a single 802.11b or 802.11g access point can support the limited number of phones (generally only one) that will be in use simultaneously. RF interference from microwave ovens and neighboring wireless LANs set to the same channel can cause significant impacts on performance, however. Consumers may have to reconfigure the RF channel of their access point to have effective wireless voice service.

Unfamiliarity with wireless technologies may preclude some consumers from purchasing VoWLAN equipment. In addition, the inability of Internet telephony to operate during power outages and limited operation of 911 services may keep some consumers from moving forward with a wired or wireless VoIP solution. Despite these issues, though, VoWLANs in homes and small offices is expected to proliferate over the next few years.

Security systems

The ability for people to quickly report wrongdoings and suspicious activities is vitally important for providing security in all companies and organizations. A person equipped with a wireless phone, for example, can get critical information to the appropriate organization for it to respond to an emergency situation. For example, a security person in an airport can report the findings on an unattended piece of luggage, which would trigger a reaction from the airport security team. VoWLAN systems can certainly support these types of functions to bolster security through faster response to situations.

Companies can also deploy wireless security cameras that send video over wireless LANs. This approach is much more feasible than running wires to each camera. The ease of installation allows a greater number of cameras to be put in place, which increases the viewing of the different parts of a facility or campus.

A major issue with using wireless LANs for supporting wireless voice and video is that they are vulnerable to denial of service (DoS) attacks. A person wanting to disrupt the security system can block the flow of voice and video signals by jamming the network. For example, someone can transmit either an overriding RF signal or specialized protocols (such as multiple CTS frames having long NAV values) that block phones and cameras from accessing the network. Also, wireless video cameras are vulnerable to sniffing. For example, someone could passively monitor the video stream using a tool such as driftnet. Companies must consider these threats and plan accordingly.

Read the second section: Determining VoWLAN solution ROI

Read Chapter 1, "VoWLAN Applications and Benefits" from Deploying Voice over Wireless LANs in its entirety.

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