Wireless LANs enable us to go mobile with laptops and PDAs, but that means we must rely on batteries for power. Of course, we all know about the battery issues when traveling in an airplane, waiting for a connection at an airport, or performing a RF site survey. We're lucky if our laptop lasts for over an hour. Take a look at the new methanol fuel cells that enable operation of a laptop for approximately eight hours. This could be the answer to the battery longevity issue.

A while back, I'd discussed tests that I'd performed while introducing interference from a neighboring access point set to the same channel. My finding then was that there wasn't much impact. This was with no users actively using the neighboring access point, however. Recently, I re-ran the tests with ten users continuously sending TCP/IP pings to the neighboring access point, and the throughput fell by roughly fifty percent! Keep that in mind when planning access point channels. There's certainly merit in setting neighboring access points to non-conflicting channels.

I've been working with radio cards radio from multiple vendors recently with a Linksys access point (actually router) and occasionally run into issues where a card isn't able to see the access point. This generally happens after activating and deactivating WEP or WPA. In order to fix the problem, I just simply disabled and then enabled the radio card. After that, the card is able to see the access point. I'm not sure why this happens, but it's something to keep in mind if you find a radio card that is having trouble either seeing or associating with an access point. I imagine that this is analogous to the benefits of rebooting a PC when problems arise.

By default, access points have their data rate set to "auto" so that they will rate shift as needed to maintain associations with users. Most access points also allow the data rate to be set to specific values, such as 1Mbps. Keep in mind, however, that the setting in the access point only applies to the data rate that the access point uses, not the wireless clients. For example, setting the access point to 1Mbps causes the access point to transmit all frames at 1Mbps. In this situation, wireless clients set to "auto" still continue to use higher data rates if possible. In order to extend range by forcing lower data rates, you generally need to set both access points and user radio cards to the lower data rate configurations.