Wireless Access Control and Security Demystified

A tutorial on the fundamentals of designing a wireless access control system


Let's step back in time and recall a simpler life. The good ol' days. Days when you'd come home after a long day, driving home in a torrential downpour, and getting soaked to the skin running from your car to your garage door and back because automatic garage door openers weren't available yet. Or how about relaxing on the couch with your family and your favorite television program is about to come on. But it's on another channel and you'd have to trudge across the room to turn the dial. While these scenarios are a bit dated, they still illustrate life without wireless technology. Since then, we've become dependent on mobile phones, WI-FI, and many other wireless devices in our daily lives.

Why are these applications successful? They solve problems. They're more efficient. They are less disruptive. These are the same attributes of wireless access systems. To design a successful wireless access system, follow three simple steps: 1) Determine product placement; 2) Select wireless products; 3) Conduct an RF coverage test. In the article below, we approach steps 1 and 3, with the goal of allowing you to make wireless access products an integral part of your upcoming access control projects to provide a greater value to your customers.

Determining Product Placement

Radio frequency transmissions from wireless systems don't require line of site for effective communications with indoor applications. By operating at 900 MHz, signals are able to transmit through common building materials such as cinder block, plaster board, wood and concrete. This enables tremendous flexibility with product placement.

Panel Interface Modules are at the center of wireless solutions, which are the bridge between wired systems and wireless locksets or access points. PIMs are available in two versions. The most common type supports up to two wireless access devices and connects to most access control panels or reader interface modules via standard Wiegand or mag stripe protocols. Another type supports up to 16 wireless access points and connects directly to select access control panels via an RS485 interface without reader interface modules.

Companies that have developed this interface are the exclusive distribution channels for PIM-485 modules, including Apollo, Diebold Card Systems, Geoffrey Systems, GE, Lenel, MAXxess, Pacom Systems, RS2, Software Data Systems, and Software House. While PIMs can be placed up to 500 feet away from access control panels, PIMs are often co-located in the same equipment closet simplifying the installation process.

For best performance, ensure wireless access points are within 200 feet of their respective PIM, which is located on the same floor. If you're looking to retrofit wireless access into an existing building, you can always measure distance by counting ceiling or floor tiles, pacing it off, or tape measures and measuring wheels. But what if the building isn't constructed yet? You can work from building plans by making a 275-foot square to the same scale as the blueprint's, as shown in Figure 1 (see Figures display area, at right). In many cases, you'll be able to cover the whole floor from the equipment closet.

For large buildings like warehouses and airplane hangers, you may need multiple, remotely located PIMs to ensure coverage for all the doors. You may also need multiple PIMs if you have many doors to secure. This is not a problem because there are 15 channels to choose from and over 65,000 unique addresses per channel. That's nearly a million combinations so you can follow the likes of Biola University, Mississippi State University, and University of Wisconsin-Whitewater that have hundreds of wireless access points installed on their campuses.

In Figure 2 (A and B), the IT closet near the middle of the floor is an ideal location to install panel interface modules despite the courtyard in the center of the building. Given the door count, multiple PIM-485s would be the best option to communicate with wireless modular mortise locksets and the wireless exit bar in the stairwell.

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