Editor’s note: This is the third part of a series about Wireless Local Area Networks. Matt Gunter, a radio frequency engineer, founded Goose Creek Technologies.Wireless Local Area Network vendors are always boasting of increased speed, higher power, longer coverage distances, and mesh technology.
Most of this is complete baloney and is stretching the facts.
You just can’t fight the physics of Mother Nature, although many vendors’ claims appear to do just that. As with all advertising claims, if it is too good to be true it probably is.
The WLAN market is still the Wild West with little regulation of claims and compatibility. Yes, there is the Wi-Fi Alliance (WECA), but even they have difficulty controlling all of the players and ensuring devices are up to par.
Hardware vendors are all of the time trying to one-up each other with the fastest WLAN devices. Unless you install a WLAN with hardware all from that one vendor, this doesn’t make much sense. Even then, what happens when a guest comes to the office and has a wireless device from a different manufacture? With this in mind, don’t fall for the ‘Turbo’ modes that are not part of the 802.11 standards.
This vendor-proprietary speed mode will get you nowhere. Besides, what good is 108 Mbps or even 54 Mbps on the WLAN if it is connected to a T1 (1.5 Mbps) going out from the office to the Internet? These turbo devices may achieve those speeds, but the moment a device operating within the standard comes into the WLAN, the turbo devices are clocked down to normal.
Limits on speed
High speeds even within the standard are usually never attained. Factors such as channel interference, system loading, and signal strength all affect the actual throughput. There are not many times when operating on a congested 802.11b system that you even clock in at 11 Mbps. Even if you do get the top speed of 11 Mbps, the effective throughput is really around 5 to 6 Mbps. As the WLAN sees more deterioration in the wireless channel, all devices will be continually clocked down to a crawl.
Everyone always hears the vendors touting a 300 ft coverage radius of a WLAN access point. This may be true if you were outdoors and there were no obstructions between the user and the access point. The 300 ft claim is by far the most misleading and over-generalized information from the hardware vendors. When placed in an office environment with walls, cubicles, floors, doors, and desks you will be lucky to have quality signal within 100 feet. The radius of coverage of a WLAN access points depends on the output power and the obstructions.
There are certain phased-array WLAN access point vendors out there touting 200 to 300 percent increases in effective coverage range. While phased array technology can offer increased coverage radii, why would you want to spread that much coverage out there? With all wireless systems you really want a smaller, well-defined footprint of quality coverage and thus better user capacity and throughput. You do not want to be covering (and wasting RF energy) on the building next door. This causes interference and system deterioration for everyone.
Power doesn’t equal performance
High power WLAN devices do not necessarily mean better performance. Adding more power to the WLAN is like yelling louder in a room full of other people screaming so that you can communicate to the person in front of you. It just does not help the situation.
Having a high power access point does not help the interaction with the wireless card at the end user. You need a balanced wireless link. If you have an unbalanced wireless link, the user may ‘hear’ the access point, but because the user is of weaker power, the access point may not ‘hear’ the user. One-way communication brought forth by adding more power is no good to anyone.
Mesh WLAN technology sounds great and if it really works would have a positive impact on system performance. The basis for mesh networks comes from a field of computer science called ‘distributed systems’ where each node of a network takes on a load balancing process. An access point would be considered a node. Currently there is no industry standard for mesh networks. Too many performance problems are encountered with mesh that include extraneous air traffic, packet paths, and quality of service. No one vendor has the fix for all of these problems, and until there is a merging of vendors in the mesh field, we won’t see an effective mesh solution. When it does come, it will be a great improvement, though.
Speed and coverage performance can be helped by properly designing the WLAN with RF Engineering from the very beginning. With any wireless network, the desire is to have small zones of quality coverage with minimal overlap among zones. These smaller zones of quality coverage enable users to have better throughput and higher system performance in general. Increasing power levels and expanding coverage radii are not effective solutions to WLAN performance problems.
Part Four on Tuesday: Wireless Alternatives
Part One of series: www.localtechwire.com/article.cfm?u=9124
Part Two of series: www.localtechwire.com/article.cfm?u=9135
LTW interview with Matt Gunter: www.localtechwire.com/article.cfm?u=9106
Goose Creek: www.goosecreekcom.com