Corporate Wi-Fi Integration, Part 3

By Mike Houghton

September 29, 2004

In this, the third part of our series, we delve further into what WLAN architects ought to consider including the factors that can lead to spotty coverage, real-world performance and the industry's top vendors.

In parts 1 and 2 of this of this 4-part series, we discussed some of the reasons for making the switch to Wi-Fi, the all-important site survey, and what components make up a WLAN. In this, part 3 of our series, we'll discuss some of the issues that inevitably crop up and a list of the top Wi-Fi vendors.

System Hang-ups

In spite of the many clear advantages, 802.11x networks can still be troublesome. Most building construction materials will obstruct 802.11x transmissions and the radios will pick up interference from competing devices on the same frequency. Major culprits of electromagnetic interference include such things as production equipment, any steel structure that can block or reflect the signal and even standard appliances found in many offices today, like microwave ovens and cordless phones.

Some other things to consider when planning a Wi-Fi network include fading signals around elevator shafts and stairwells, window tinting that contains metal and competing wireless LANs in close proximity. Typically you will be able to find ways around these types of interference by simply adding more access points (APs) while being sure to avoid overlapping channels.

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Most building construction materials will obstruct 802.11x transmissions and the radios will pick up interference from competing devices on the same frequency.
Another consideration are those rare times when the AP's bandwidth is maxing out, such as when there's a meeting in progress and several users are attempting to log onto the network from the same access point at the same time. Although occasions like this may be rare, the WLAN designer should remain mindful of this situation when engineering the design.

Then there is the issue of the ever-changing 802.11 standards. First, in 1997 we had plain 802.11. This standard supported a maximum bandwidth of 2 Mbps. That was hardly enough to make the investment worthwhile. In fact, manufacturers no longer support this standard.

Next we had 802.11b. This standard supports up to 11 Mbps. Fast enough to be comparable to Ethernet networks making it an attractive alternative to wired networks. This standard uses the same unregulated 2.4 GHz frequency as the original. Unfortunately this is a double-edged sword. Being unregulated means less expensive equipment but it also means that it can incur inference from other non-Wi-Fi appliances.

Created at the same time as the b standard, is 802.11a. This standard runs on a regulated 5 GHz frequency and supports up to a whopping 54 Mbps, however because of its higher frequency, its range is falls short of 802.11b. On the plus side, since it operates on a regulated frequency, you get little to no interference.

Then, of course, there is the ever-popular 802.11g standard. This standard also supports 54 Mbps and runs on the same 2.4 GHz frequency, thus allowing it to be compatible with b networks.

Last but not least, we have the relatively new 802.11i standard. With the approval from the Institute of Electrical and Electronic Engineers (IEEE) on June 24th of 2004, this is an important step towards legitimizing WLANs as it uses stronger cryptographic algorithms and reduces the number of packets involved in key management.

We will be seeing more of this standard in the future. Which leads us to the some additional issues to consider.

Page 2: Pressing Matters: Security, Range and Mobility

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