Straining the alphabet WLAN soup

Just when you thought you had your wireless LAN strategy all mapped out, the IEEE’s standards board ratified 802.11g, which ups the data rate of the popular 802.11b WLAN standard, and the FCC is proposing to more than double the number of frequencies available to 802.11a. How does it add up? Let’s review.

Just when you thought you had your wireless LAN strategy all mapped out, the IEEE’s standards board ratified 802.11g, which ups the data rate of the popular 802.11b WLAN standard, and the FCC is proposing to more than double the number of frequencies available to 802.11a.

How does it add up? Let’s review.

The newly approved 802.11g standard bumps up 802.11b from 11M bit/sec to 54M bit/sec. Both standards use radio frequencies in the 2.4GHz range, and 802.11g devices can fall back to 802.11b data rates, meaning 802.11g access points can support existing 802.11b nodes.

Our tests show that 802.11g throughput is 15M to 24M bit/sec, about four to five times the 4M to 5M bit/sec throughput of 802.11b. This means 802.11g networks should support four to five times the number of users as 802.11b nets.

Essentially, 802.11g is an amendment to 802.11b, bringing it up to 802.11a’s data rate. But unlike 802.11b/11g, 802.11a uses frequencies in the 5GHz range, free from interference from devices such as cell phones that can be a problem for 802.11b/11g. More importantly, it is free from interference from the growing population of 802.11b devices. Stan Shatt, an analyst with Forrester Research, says a client in Oklahoma did a scan before building a WLAN and picked up signals from 11 neighboring 802.11b WLANs.

The FCC’s proposal to make more frequencies available for 802.11a – upping the number of channels that each access point can support from 11 to 24 – will make 802.11a even more immune to interference. By comparison, 802.11b/11g access points only support three non-overlapping channels. That makes 802.11a ideal for installations with high concentrations of users who need high-speed access.

Is your head spinning yet? Don’t worry, you can avoid the alphabet soup by deploying dual radio 802.11a/11g access points and get the best of what 802.11a has to offer, and the broad reach and backward-compatibility of 802.11g. However, this is: 1) the most expensive solution today; and 2) a compromise. As Shatt says, in dual mode environments you can’t optimize for either approach so you end up with a network that is the best of neither.

Other analysts say the whole 802.11a/b/g question will be moot in the longer term because all three will be built into silicon and available in all products. But it will take some time to get there so the dual-radio approach might be the safest bet if you’re worried about painting yourself into a corner.