Wireless access points work best for spanning between floors when the floors in question are next to each other (e.g., floors 1 and 2). If your organisation is in a building where another company has an intervening floor, using wireless access points becomes problematic due to distance problems and the potential for interference. Look for a common area on each floor where you can place the access points. A janitor or supply closet is a great second choice for access point placement if you don't have wiring closets on each floor. The locations do not have to be "stacked" one on top of the other, but stacking the access points will cause the signal to be stronger. Put an access point on one floor and go to the other to see how well you can "hear" the access point on the other floor using a laptop with a wireless card. If you get anything other than a full-strength signal, move the access point to another location. If you can't accomplish a full-strength signal in any location, you will need to look at some type of directional antenna to boost the signal so that you can punch through the floor and achieve a reliable signal. Once you've found the best signal location, place your second access point there. Continue until you have access points placed on all floors of your building. Don't forget to check which 802.11b channels are in use on both floors. Make sure that the channel you use for between the floors isn't too close to the channels in use on the floors. If you have channel 2 in use on Floor 1 and channel 5 on Floor 2, using a channel between 2 and 5 wouldn't be a good idea for in between the two floors. If you use a channel between 2 and 5, you could experience overlap and interference, which can slow down communications. In this case, you would want to use a higher channel, such as 10 or 11. Access point placement: Building-to-building
Connecting building-to-building utilises some of the same concepts as using access points from floor-to-floor. Do a site survey at both locations with a laptop and wireless card to see what channels are in use. Once you can find a clear frequency, you will need to find a location at each building where you have line-of-sight to the target building. This may require the use of a tower to get the antenna high enough to get a clear view of the other building. In a building-to-building connection, using the antenna that comes with the access point probably won't work. Most antennas that come with access points are typically omnidirectional, which means they send an equal amount of signal in all directions. Because you will be sending data directly from one building to another, a directional antenna will do a much better job. Keep in mind that the higher the decibel (dB) gain figure for the antenna (dB is a measurement that indicates how efficiently the antenna is broadcasting the signal), the narrower the beam or signal path coming from the antenna. This narrower beam means that the signal can travel farther before starting to degrade. However, a narrow beam has one drawback: The higher the gain of the antenna, the more carefully you will need to align the antennas to get the best signal between buildings. In a building-to-building link, you should have an external (outdoor) access point. Outdoor access points are generally a little more expensive than the access points you would use inside the building. If you don't want to use, or can't afford, an outside access point, you could also use an internal (indoor) access point in conjunction with a high-gain antenna mounted outside the building. Regardless of type, make sure the coax cable between the access point and antenna is as short as possible. Because 802.11b uses frequencies in the 2.4-GHz range, long coax cable runs between the access point and the antenna can cause more signal degradation to occur. Bridge the gap
Wireless networking solves a lot of problems for network administrators. Sometimes it's just too difficult to run new wires in a building or it's too costly to connect remote buildings on a campus. In these instances, you can use the flexibility of 802.11b to save both time and money. Carefully place your access points, and you'll wonder why you needed cable in the first place.
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