Editor’s note: This is the first in a three-part series about wireless area networks written for LTW by Matt Gunter of Goose Creek Communications.Nearly everyone has seen the ad that shows a person wirelessly connected to the Internet while in some isolated outdoor area. These ads make it appear that with wireless LAN (WLAN), you can have a wireless Internet connection just about anywhere, even at a mountain base camp. They only further increase the confusion and misunderstanding that surround WLAN.
We are fooled into thinking that WLAN is magic, plug-n-play, and ubiquitous. Just take a look at the paragraphs of fine print at the bottom of the ad to see how much information is being left out. The message from the hardware vendors can be misleading to the uninformed buyer.
The WLAN ads and accompanying hype are not entirely bad. WLANs are a very productive and useful tool when implemented properly in the workplace or home. Currently there are too many sources of misinformation when it comes to WLAN.
First, you have the hardware manufacturers who spread the hype through misleading multi-million dollar ad campaigns.
Second, there are the value added resellers (VARs) who just blindly regurgitate the manufacturer’s hype to the customer in order to offload hardware and make a buck.
Finally, there is the media who have been misinformed by first two parties in this equation. These sources either know better and are spreading hype to sell a product or are drunken with the wonderful technology and don’t care about the facts.
For the businessman trying to enable a more productive workforce, it is hard to cut through the hype and make an educated decision. One does not know where to go to get a straight answer about WLAN. The decision-making process can seem like an alphabet soup or a letter-number game. Often vendors use this confusion to their advantage and overwhelm the customer. In this article series we will expose the realities of WLAN in five areas: radio frequency engineering, security, performance, alternate wireless technologies, and regulatory compliance. Hopefully, the reader will gain some powerful tools and useful information that will enable them to more effectively navigate the WLAN ocean.
Radio Frequency (RF) Engineering
RF Engineering is the science used to study how wireless signals propagate through various materials. The physics of this science is used to design both wireless devices and the large-scale systems those devices work within. For example, to determine the placement of cellular towers geographically around a city, RF Engineering is used. The same physical principles apply to the placement of WLAN access points within a building. Each building consists of a unique floor plan and wall materials. These two factors greatly affect how each WLAN access point will provide coverage. For instance, going behind a wall while surfing the Internet with your wireless notebook can be equated to driving behind a mountain while talking on the cell phone. On the cell phone you may drop the call due to loss of coverage, while on the notebook computer your speed may decrease or your connection can be lost.
To solve the coverage problem incurred by signal loss from walls, one probably has to add more WLAN access points. Contrary to the way WLAN is portrayed as plug-n-play, you cannot haphazardly place the access points here and there and expect the performance to be great. You need an expert who can show you where to place the access points given your floor plan and wall materials. This expert is an RF Engineer. An RF Engineer is an electrical engineer with a specialty in electromagnetics. Don’t be fooled by imitators.
Many hardware vendors will tell you that you don’t need a RF Engineer to implement your WLAN. They also may try to sell you their proprietary access point placement software to replace the RF Engineer. Although the network may initially come together and seem to hum along just fine, problems will become apparent as the system grows. The fact remains that each WLAN deployment is in a unique environment and that you need someone to thoroughly examine your unique floor plan and wall materials to properly determine access point placement.
No software from a hardware vendor can adequately model your unique situation. The placement software will either overbuild or underbuild the WLAN, both of which are not an option for you. In fact, to cover their tail and make more money, don’t you think the vendor’s software will overbuild the WLAN?
Some vendors may tell you that a site survey is not necessary to implement a WLAN. A site survey is where a technician uses a test access point in a fixed location to determine the amount of coverage that can be achieved in the environment where you plan to deploy your WLAN. This information can be used to further tune the propagation model used to position your WLAN access points. During the site survey other important information such as neighboring WLAN channels and ambient interference will be recorded. This information is critical to designing a well-performing WLAN and minimizing interference.
Also, be aware of the test and measurement equipment that your system integrator uses during this phase. A notebook computer with a wireless card and the vendor’s site survey software (or NetStumbler) is inadequate. There is too much variance in the sensitivity of wireless cards and this should not be the basis for a design. A calibrated spectrum analyzer should be used to ensure proper design.
The physical layer
Because of the nature of wireless (i.e. no wires), many IT admins neglect the very important physical layer of the wireless interface. The wireless physical layer is the foundation of the network. It is comparable to the Cat5 wires in a wired LAN. Some think that if you cannot see the problem it does not exist.
Without proper planning on the physical layer, how can one expect all of the higher network layers to work properly? Therefore, it is absolutely critical to have an expert in the physical layer, an RF Engineer, design your WLAN. You will save yourself a lot of heartache and money in the future because your WLAN will be robust enough to stand the test of time.
Next: Information Security
Goose Creek Communications: www.goosecreekcom.com