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Chapter 2: Preparing for a WAN Deployment
• Deploy and Check
In this scenario, an initial site survey is not performed. Instead, wireless administrators make educated guesses on the best
locations for the access points, or they use a planning tool to determine the locations more reliably. After deploying the access
points, the administrators do a quick site survey. If they need to provide greater coverage, they deploy additional access points.
If there are areas where access points are interfering with each other, they then relocate one or more of them. With cooperative
RF control, SmartPath APs automatically adjust their channel and power to compensate for coverage gaps and areas of
interference.
The deploy-and-check approach is often much cheaper and faster than doing a predeployment site survey. The risk is that you
might have to move some access points and CAT5 (Category 5) Ethernet cables if you do not plan properly. SmartPath provides
a huge competitive advantage in the deploy-and-check approach, thanks to its flexible mesh networking capability. An
administrator can deploy with mesh (before running wires) and check the performance in several layouts, determine the best
layout, and then run the wires to their final location.
• Deploy without Survey
Although it is usually advisable to do a site survey, there are many situations in which it is not feasible or even necessary. If the
location is sufficiently small—for example, a deployment of only three or fewer access points—site surveys have limited value
because there is virtually no opportunity for interference. If there are numerous remote locations, a site survey might be
impractical because of the cost of traveling to each site. In these locations, you can use a slightly denser deployment to ensure
appropriate coverage and capacity. SmartPath APs automatically adjust their radio power levels to ensure that there is minimal
overlap from interfering channels. Usually the cost of extra access points is offset by the cost saved by not doing a site survey in
a remote location.
2.2.4 Budgeting Wi-Fi: The Chicken and Egg Problem
The hardware cost of a Wi-Fi solution is generally driven by the number of access points needed, and a SmartPath network is no
exception. Unfortunately, a traditional challenge of budgeting for Wi-Fi is that it is difficult to know how many access points to
plan for until you have deployed and measured them. There are methods of doing site surveys before a deployment to answer
these questions. While doing so is often worthwhile, you might just need a general idea of what you should budget. Fortunately
there are some simple guidelines that you can use to figure out how many access points you need, including the number of
access points per square foot, the number of clients per access point, and the distance between access points.
• Access Points per Square Foot
The simplest and most common way of budgeting access points is per square foot. You simply take the square footage of a
building and divide it by some number. The most common metric used today is one access point for every 4000 to 5000 square
feet for standard offices with cubicles. However, if you need to support voice applications, you need a higher concentration of
access points. In this case, the recommended formula is one access point for every 3000 square feet, or even as low as one
access point for every 2000 square feet. In the lightest weight convenience networks, it is possible to use fewer access points,
and densities as low as one access point for every 10,000 to 15,000 square feet can be successful. Keep in mind that such a
deployment often has dead spots and can only support very low client densities.
• Number of Clients for Each Access Point
Another way to determine the number of access points needed is to consider the number of clients you want each access point
to support. In a standard office environment, most enterprises plan to support an average of 5 to 15 clients per access point.
Although the specifications of most access points state that they can support up to about 120 clients, a significantly lower
density is recommended to get an acceptable throughput for standard office applications. If you expect to support voice over
Wi-Fi in the enterprise, account for those phones as well. With the addition of voice, the client density substantially increases,
requiring you to plan for an average of 5 to 10 data clients and 5 to 10 voice clients for each access point. Remember that voice
clients consume virtually zero bandwidth when they are not on a call. However, when they are on a call, it is imperative that the
traffic goes through.
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