Wireless access control is the latest technology innovation in the access control industry. It sounds like the way of the future. As a result, there is a lot of interest in this new type of system architecture. But as we know, there's no value to innovation unless it solves a real problem or makes an existing solution better, faster or less costly. Proponents of this new technology claim it does just that. But how does it work, and is it as reliable and secure as the tried-and-true wired systems?
How Does It Work?
Wireless access control eliminates the wiring from the access portal being controlled to the main control panel. This is done by adding a transceiver at the entry portal and another in an RF panel interface module connected to the main panel. These panel interface modules usually wire to the panel just like a door using standard reader technology, so they receive RF signals and output Wiegand or magstripe signals via those wires. The transceiver at the portal can communicate through walls to the panel interface module that is connected to the door control panel. As a result, the main control panels, the door control panels and the panel interface modules in this new architecture are all installed in the same equipment closet. This saves space, time and money.
Some wireless access control solutions are also integrated. Instead of a series of separate components that have to be wired together around the door, they are all integrated into one unit. For example, Recognition Source incorporates the transceiver in its Modular Integrated Reader Lock. This product also has the electric door lock, card reader, door position switch, power supply, request-to-exit and optional request-to-enter functions combined. Preassembling these devices into one unit can reduce the installation time at the door by up to 90 percent.
Panel interface modules can control two to 16 doors, depending on the main-control-panel manufacturer, and are offered with Wiegand, magstripe or RS485 connections. With an RS485 connection, only four wires need to be connected to the panel interface modules to control up to 16 doors each. If the brand of control panel selected does not have an RS485 connection for wireless access, the panel interface module wires to the main panel or door-control sub-panel just as if it were a door using the Wiegand or magstripe protocol. Panel interface modules using the Wiegand or magstripe approach can control up to four doors.
Reliability and security are two big concerns for end users and integrators. The reliability concern questions if the communications are robust enough to be accurate year after year.
There are generally two kinds of security concerns. The first is whether a transceiver can be tricked into allowing unauthorized access. The second is whether any RF signal in the area will block a request or command message so a door won't open after a request to enter. There are several critical system features that can significantly reduce these reliability and security concerns.
First, to ensure reliability, wireless systems should use spread-spectrum techniques that help make the communications robust. The spread-spectrum direct-sequence technique takes information, encrypts it, and spreads it over a wide frequency band to resemble noise. The transmitted message now has a very low power spectral density compared to other modulation techniques. However, when correlated by the receiver's encryption keys, it is the equivalent of higher power density. This allows long communication distances.
Since the user data bits are coded and transmitted over a wide bandwidth, and since the receiver correlates using a set of keys, the communication system tolerates a relatively high degree of noise. This represents a basic benefit of the system's process gain, and it makes communications reliable even in RF-laden or electrically noisy areas.