New Wlan Deployment; Site Surveys - Black Box LWN602A User Manual

Upgrading from a thin AP solution is also easy. However, because a thin AP makes use of an overlay tunneled network, you
sometimes have to add a local VLAN for access or use tunnels to replicate the overlay network. However, because using VLANs
rather than tunnels provides significant performance and scalability advantages, which is clearly the recommended path.

2.2.2 New WLAN Deployment

In a new—or greenfield—WLAN deployment, you do not have the benefit of an existing network for testing and analysis, which
makes your job a bit more difficult. In this case, the following key questions are critical to the proper design of your WLAN:
• How many users will need wireless service and what applications will they use?
Determining the scope of your WLAN deployment will have a major impact on capacity and coverage. Will only certain groups
within the organization have WLAN access, or will it be rolled out across the enterprise? Will you provide guest access to visi-
tors, consultants, and contractors? Most WLANs support just data applications, but many organizations are considering adding
voice services. Voice support raises other design considerations that drive the need for denser deployments of access points and
different Quality of Service (QoS) settings.
• Are there any known major sources of interference?
For example, is there a nearby cafeteria with microwave ovens? Commercial-grade microwaves are a particularly bad source of
interference. Is there a wireless telephone or video surveillance system not using Wi-Fi? Is there a radar installation nearby? If
you cannot find the answer to these questions easily, consider employing a spectrum analysis product, such as the AirMagnet
Spectrum Analyzer.
• Are building blueprints available?
With blueprints, you can see the location of elevators, load-bearing walls, and other building characteristics that can impact
signal quality. Different materials, such as concrete walls, brick walls, cubicle walls, glass, and elevator shafts impact signal
quality differently. You can often load these blueprints into a planning or site survey tool to make the process easier.
• What devices need to access the WLAN?
Determine and document the full complement of devices that people will use to access the WLAN. The performance
requirements of the WLAN will depend on both the applications and the capabilities of the client devices. For example, design
engineers, architects, and doctors tend to work with bandwidth-hungry applications, so you might need to provide greater
capacity. Conversely, if it is a warehouse with a low client density of mostly barcode scanners, a lower access point density
might be suitable. Finally it is important to consider voice, or the future use of voice. If some or all people will use VoWLAN
(Voice over WLAN) devices, that can affect how many users each access point can accommodate.
NOTE: For some access point User Guidelines, see Section 2.2.5, Bandwidth Assumptions for Wi-Fi.

2.2.3 Site Surveys

One of the first questions IT managers ask when they are preparing for a WLAN deployment is whether or not a site survey
should be performed. In a site survey, the administrator walks around the facility with a site survey tool to measure the radio
frequency (RF) coverage of a test access point or the existing WLAN infrastructure.
Whether or not you decide to do a site survey for your enterprise depends on the cost of the survey and the complexity of the
environment. Here are the three ways to deploy a wireless network—with and without a site survey:
• Predeployment Survey
The safest approach is to perform a site survey before deployment to determine the best locations for the access points.
Typically, site survey professionals temporarily place access points in different locations, take measurements, and adjust their
settings and locations as necessary. After they complete the survey, they install the access points and then perform another site
survey to confirm that the goals have been achieved. This method is clearly the most reliable way to deploy a wireless network;
however, it can be expensive, time consuming, and impractical if an enterprise has many sites.
Chapter 2: Preparing for a WAN Deployment
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