I've been experimenting lately with wireless clients having 802.11 power-save mode enabled and different access point beacon intervals. By increasing the beacon interval, clients will sleep longer and save battery power. To get a better idea of the savings, I ran some tests with the beacon interval set to 100 milliseconds (the default) and up to 5 seconds. I found beacon intervals at 1 second provide approximately 14 percent increase in battery life. Beacon intervals set beyond 1 second increased battery very slightly. So, it's probably worth setting the beacon interval out to around 1 second for clients implementing power-save mode. Just be certain that the longer beacon intervals don't negatively impact roaming.

The common design rule for installing access points is to set adjacent ones to non-overlapping channels (1, 6, and 11). This avoids the access points from competing for the same part of the spectrum, such as when transmitting beacons, data frames, and acknowledgements. When analyzing existing wireless LANs, however, I often find adjacent access points set to the same channel. In addition, it's common to have neighboring wireless LANs set to the same channels as yours. For example, a quick scan of my residential area shows several homes having access points all set to channel 6, the typical vendor default channel.

I've been analyzing various wireless LAN issues this week and ran some throughput tests last night between a wireless client and a particular access point - with and without the presence of another nearby ("interfering") access point set to the same channel. If fact, I only measured a few percent degradation in throughput when the interfering access point was active as compared to when it was not. This indicates that there's not much impact from the beacons of a neighboring access point set to the same channel. I plan to run similar tests to analyze the impacts on throughput while multiple clients are utilizing the interfering access point. So, stay tuned!

Many companies are either deploying wireless LANs that support voice, or they're installing wireless LANs that don't need much upgrade to support voice in the future. VoWLAN (voice-over-wireless LAN) is truly becoming the killer application for wireless LANs that we've been waiting for.

As part of a project I'm working on, I've been reading over Cisco's recommendations for deploying VoWLANs. You certainly need to focus on performing a thorough RF site survey when deploying VoWLAN applications. Ensure that the SNR is at least 25dB in all areas, there are at least two access points within range of each user, and adjacent access points are set to non-overlapping channels.

I just read an article that offers some good tips on securing public Wi-Fi connections. While on the road this week (literally), I've been very conscious about security while checking email from public Wi-Fi hotspots. My email system uses SSL encryption, so I'm not too concerned about someone passively monitoring my data traffic and finding anything worthwhile.