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Some of the other benefits of wireless have already been touched on but are worth repeating. Having to trench to get to a remote location is always an expensive proposition. If that trench has to cross a parking lot, runway or other hard surface, the cost can double or triple. Being able to install a wireless link across those surfaces instead of digging up and replacing them can sometimes offer much more value than just saving money.
So what makes a wireless access control system tick? Let’s look at some of the different ways wireless is being implemented today, as well as some of the hardware options available.
How the Technology Works
Defined standards have really driven the IP network-based industries. Wireless is no different. There are, however, a few standards to choose from.
Paxton Access chose to base its wireless Net2Nano line of wireless products on the up-and-coming 802.15 standard, also known in some implementations as ZigBee. Using the 2.4GHz frequency band, 802.15 was originally conceived as a low-power replacement for cables between devices and even as a successor to Bluetooth. It has grown into a very capable mesh network wireless standard.
Engineered for low power consumption and long battery life, 802.15 lends itself nicely to the small bandwidth requirements of access control. Unlike video applications where large amounts of data are constantly streamed across the network or wireless link, access control only needs small amounts of information such as updates to access databases or event logs sent back and forth. All this put together means a very robust device-to-device communications network.
Some manufacturers like IR take a different approach. They rely on a lower frequency range, 900MHz, for their communication needs. Some of the benefits of 900MHz over other technologies like 802.11 WiFi wireless include longer range and better battery life, as well as a smaller amount of interference in the 900MHz band.
Both systems, however, are similar in their approach to hardware. The actual card readers are hard-wired to a local controller or reader interface unit. Sometimes these controllers handle a single door, sometimes multiple doors. These controllers then communicate wirelessly back to another node on the wired network, connecting them with the server. These controllers will accept manufacturers’ own lines of readers but in most cases also can take in open standards like Wiegand, allowing a very wide range of reader technologies like proximity or smart cards.
A solution that is proving to be very popular in small to midsize systems is an integrated package with the wireless transmitter, card reader and, sometimes, a keypad integrated into the lockset itself. This type of wireless product offers some of the greatest savings in lab
or and materials as no cable has to be run at all. The all-in-one lockset is installed on the door itself, and you are done.
For some of the applications we described above, especially the historic building projects, this self-contained wireless lockset can be a lifesaver. And because of the small amount of data being sent between the server and the device, battery life can be measured in months or years in some cases.
Careful Planning Pays Off
As is usually the case, the most important thing you can do to make sure your installation is successful is to plan ahead. Don’t forget the old adage: Prior Planning Prevents Poor Performance.
Remember that even though the data usage and bandwidth requirements of access control systems are far less than video systems, it is still important to ensure the best quality wireless links that you can.
The first and most important thing you can do is a site survey. Even with the best survey possible, there’s no guarantee that the situation won’t change as soon as you sign off on the project. That doesn’t mean it shouldn’t be done, however. There are many tools available for the site survey from the fairly reasonable in cost to pretty expensive but powerful.
Essentially, a site survey is used for two things. The most basic is to map out and determine the signal strength between your wireless devices. This is the most important part of the survey.
Some survey tools go further and provide a way to pick up and, in some cases, identify sources of interference. In the 2.4GHz range, the most common interfering device is the WiFi network access point. Every frequency range, however, has interference of some kind. Whether it’s cordless or cell phones, microwaves, TV and radio stations, there are no truly clear frequencies in use today. Making sure you pick the best locations and available channels will go a long way to ensuring issue-free operation.
(Both of the manufacturers mentioned in this article have their own preinstall survey kits available, and both are very simple to use.)
It is also important when planning a wireless access installation to follow the manufacturer’s recommended distances between devices as closely as possible. Here too, however, keep in mind that every wireless installation has its own set of particular circumstances, and many factors will affect the distance you can place devices apart.
