System Design Exercise
So far, we’ve been discussing our project and what needs to be done. Let’s simulate the installation.
We have a 150x150-foot, L-shaped building to protect. Using the Pythagorean Theorem, the distance between the two corners in Figure 13 is 212 feet, which is pretty close to the 200-foot rating we established earlier. However, by putting PIMs in room 14, you should be able to cover the entire floor, as the RF can cut across the open courtyard between the two wings of the building (see Figure 14).
The only problem with this scenario is that you do not have control over the courtyard. When looking at a blueprint, all you see are the building dimensions — the challenge is to plan for the unexpected and visualize how the space will be used in a year or more down the road. For example, after building completion, landscapers install trees, shrubs, flowers, picnic tables and a walking path as shown in Figure 15.
How will this effect RF performance? Chances are the trees will eventually impede the signal from reaching doors 1, 23, and 24 as shown in Figure 16. That’s why is best to be more conservative in your planning as in Figure 17, where PIMs are split between Rooms 6 and 14 to ensure 100-percent coverage.
To quickly recap, the 200-foot coverage radius is considered a cell of 275x275 feet. We counted the number of doors needing access control to ensure we had sufficient PIM capacity. We laid these square cells on top of our floor plan to determine the number of PIMs required and, then, found the best locations for them, adjusting our squares accordingly. Using our worksheet, we wrote down all the equipment we needed, leaving nothing to chance.
Once you have created your first wireless access control system, the next will become even easier. This exercise should start you on the right path.
Andy Geremia is Product Manager for Schlage Electronics, a division of Ingersoll Rand Security Technologies.