Will building materials affect my wireless LAN?

Q: How much will different building materials affect the way we deploy our wireless LAN? – David, San Jose

A: This question is often the first one asked when an enterprise considers a WLAN deployment. Yes, each building has unique radio frequency characteristics as a result of the materials used in construction (glass, drywall, concrete, wood, etc.), as well as the way the floor plan is laid out.

But in the typical office environment, these have a minimal impact in determining how many radios are needed in a WLAN deployment. If you look at the typical 2.4 GHz path loss caused by different building materials (see chart), you will find that the difference in density between those materials most commonly found in office environments is often no more than a couple of decibels. For the most part, this variation is negligible when it comes to overall network design.

A typical office building will require approximately one access point for every 3,000 to 7,000 square feet in order to achieve seamless coverage, regardless of the type of material within the building. To determine whether you lean more towards placing one access point every 3,000 square feet or one access point every 7,000 square feet, consider your desired user performance and coverage. If your goal is to maximize throughput in your WLAN and provide the highest level of radio frequency coverage, then you would want a higher access point to square-foot ratio. If your primary goal is so minimize the number of access points deployed to keep costs down, then you will want a lower access point to square-foot ratio.

Things do get trickier if your environment has a large number of concrete walls, which can have a radio frequency path loss up to 10 to 15 decibels (or higher in some locations, such as a sports arena). This can dramatically limit radio frequency propagation, which alters the way that a WLAN should be designed. In these environments, you should use a radio frequency prediction tool to get better visibility into the specific coverage of a radio and numbers of radios needed. There are several commercial products available, and many WLAN vendors offer this as part of their planning tools. We’ve also seen some offers for free radio frequency coverage estimates, which could provide a great introduction into deploying a WLAN in your building.