If you’ve ever setup a wireless network, you know that there is a great mismatch between what a manufacturer claims the range of its router or access point is, and the ability to connect to that device from different points in a home or office.
The range you can achieve is greatly affected by the environment. Your 802.11 devices may claim anywhere from 150 to 300 feet of range, but where you place your access points, residential gateways, and the computers you want to connect can have a major impact on the quality of your network.
Walls, ceilings, sources of RF noise like microwave ovens, 2.4 GHz wireless phones, other wireless networks, and other interferences lower throughput and diminish the range of your WLAN. Consider these two facts.
Every wall between your client and its network access device diminishes the range of the connection by about 100 feet (this varies according to construction details). Furthermore, if you connect up to a wireless device through a 1-foot wall at a 0-degree angle, the wall behaves like it is a 1-foot wall.
But if you try to connect to an access point in your basement using a computer in your bedroom, and there is an 85-degree angle, that wall will appear to your computer to be 11.47 feet thick (cos α = 1/x).
If there are multiple WLANs in the same space using the same channels, then wherever they overlap there is interference and signal loss. All is not hopeless, however.
Regardless of your situation there are techniques you can apply to improve your wireless coverage. You can compensate for loss of range by adding more access points, by using repeaters, by altering the channels of different WLANs so that they don’t overlap, and by better placement of the devices you have.
First Access Point
The best place to put your first access point is in a central location away from walls and any other electronic gear. If possible, a location several feet off the ground is best. You may simply want to try experimenting with placement until you find some sweet spots in your location.
If you took an organized approach to creating your WLAN, you may have started with a connection diagram that placed the location of your access points, routers, and clients on a map.
This map doesn’t have to be drawn to architectural scale, but it’s best if it is approximately representative. You can draw this map on a sheet of paper, or if you want to be a hit at cocktail parties you can use the back of your napkin.
However, we recommend that you create this map inside a drawing program. It can be a simple drawing program using common shapes for the identities of your network components, or truly representative icons from a networking library that Visio might offer you.
The advantage of an electronic file is that you can move the objects around as you learn more about your devices and their capabilities. You may have some ideas as to where to place your access points, but to really know what’s going on you need to measure your network connection and throughput.
A really good measurement would include signal strength and throughput, but for a small environment it is probably adequate to simply measure signal strength.
Chances are that your signal strength will vary during the course of a day, so you should check the strength at different locations at three or four different times during the day.
Good times are times of maximum network usage such as the morning e-mail check, and the end-of-day last minute desperation hour before 5 p.m., as well as times of low network usage such as late night.
Atmospherics do make a difference, and 802.11 essentially is a radio technology, so nighttime reception is often much improved over daytime reception. There are really two logical places to put your first access point:
- In the center of your office or house to get the maximum possible range.
- In a location where you want the best wireless connection possible; say a den, study, or bedroom where you want to work wirelessly often.
Each location for your first access point has both advantages and disadvantages. Given the amount of material written on Wi-Fi, it’s rather amazing how little has been said about location selection.
The first consideration for location is that you have to have your access point attached to a network connection. If you have no wired LAN to connect to, you have to locate your first access point so that it connects to your broadband connection, or to a hub that you’ve connected to that router.
If you have a wireless router and that is your outside network connection, then you are limited to the length of your direct connection to the outside wire. It’s best to choose a location as high off the floor as possible, and with the clearest location, or for smaller rooms, on a desktop.
Don’t put the access point on the floor. Remember that placement of your access point is a little like placing a radio: don’t put the access point on top of your TV, near a stereo, anything with a power supply (a computer), or with a strong magnet (speakers, for example) or any other RF source.
This is a good point in the process to determine the impact of changing antennas and other tweaks you might want to use. Suffice it to say here that the use and placement of an antenna can be just as significant as the placement of the access point itself in determining performance.
Don’t forget to move the antennas around to different positions to measure the effect. It’s a little like positioning antennas on a TV; direction does matter. You can also improve access points, repeaters, and other wireless devices by adding a better antenna to them than the one that they come with.
This is one important reason to purchase an access point that lets you swap out its antenna. Most 802.11a devices have fixed antennas, but most of the new 802.11b and 802.11g devices let you add a different antenna.
Signal Loss
Signal loss is a major problem for WLANs. Signal loss occurs because the radio signal interacts with solid material and is transformed from electromagnetic radiation into heat, or because of other interference such as other radio waves canceling your Wi-Fi signal out.
The causes of signal loss are numerous and include:
- Physical obstructions, such as walls and ceilings.
- Interference from other radio frequency devices including microwave ovens and phones, and competing wireless networks
- Signal reflection and interference from metallic surfaces, mirrors, metal coated insulation, metallic paints, and even nails and studs in the walls.
- Dense construction material such as concrete.
Each of these factors lowers the signal strength, and the amount of degradation is also dependent on the frequency of the wireless signal.
Thus an 802.11b access point will have a lower loss through material than an 802.11g will for the same signal strength because 802.11g is higher energy and has a more powerful interaction with material or other radio waves.
