Wi-Fi

Evaluating the wireless networking options

Presently, Wi-Fi comes in three flavors: 802.11A, 802.11B, and 802.11G. To help you decide which version will work best with your network, here is a discussion on the advantages and disadvantages of each of these standards.
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Now that wireless networking has been around for several years and is starting to mature, companies have a variety of wireless networking standards and products to choose from. There are long-distance products used to send data between buildings miles away and then there are the shorter range products that typically provide wireless networking services within an office building or a warehouse. Both of these areas have a lot of different products and standards available, and there is no way that I could discuss them all within one article. However, since Wi-Fi is the dominant wireless networking technology at the moment, I want to discuss the various Wi-Fi options available and how to choose between them.

802.11B
802.11B is the Wi-Fi technology that has been around the longest. I implemented an 802.11B network in my home in 1999. The standard is well supported and stable. An 802.11B network theoretically supports speeds of up to 11 Mbps. However, in the real world, I have never seen an 802.11B network with a throughput above 5 Mbps. The advantages to using 802.11B are price and compatibility. 802.11B hardware is widespread and extremely inexpensive compared to 802.11G or 802.11A hardware.

There are two distinct disadvantages to using 802.11B: security and performance. Security is an issue because 802.11B is so widespread. There are numerous hacking tools designed specifically for exploiting 802.11B networks. An example of such a tool is NetStumbler, which detects wireless networks and uses a GPS to plot the location of each detected access point onto a map.

The biggest performance issue is radio interference. There are so many 802.11B access points in use today that it is not at all uncommon to get interference from other access points in the area. 802.11B operates in the 2.4 GHz frequency range, which also means that it is susceptible to interference from microwave ovens and 2.4 GHz cordless phones.

802.11G
802.11G is an extension to 802.11B. Like 802.11B, 802.11G operates in the 2.4 GHz frequency range. This means that 802.11G devices are susceptible to interference from other access points, microwave ovens, and cordless phones. So what are the advantages to using 802.11G? The primary advantage is speed. 802.11G has a maximum rated speed of 54 Mbps. To achieve the higher speeds, however, you will have to make sacrifices.

For starters, an 802.11G signal requires 30 MHz of bandwidth. The entire 802.11G frequency range only consists of 90 MHz of total bandwidth. Thus, you will only be able to colocate a maximum of three 802.11G access points within a given area.

The other disadvantage to 802.11G is range. An 802.11G signal has a shorter range than an 802.11B signal. In a way, though, this is a mixed blessing. Because of the short range, you may be able to use more than three access points to service a building, so long as no more than three access points are within range of each other at any given time.

The other advantage to 802.11G, besides speed, is compatibility. 802.11G is completely backward compatible with 802.11B. Therefore, if you already have a big 802.11B network in place and want to upgrade to something with better performance, 802.11G will allow for a smooth transition. You would begin the transition process by swapping out the access points. Remember, though, that an 802.11G access point doesn't have the range of an 802.11B access point. Therefore, if your current access points are widely scattered, or if you have wireless clients far away from the existing access points, you will probably have to install more access points than are currently in use. Once the access points have been swapped out, you can begin changing out wireless NICs. Existing clients will continue to use 802.11B until they have been given an 802.11G NIC. The access point supports both protocols.

802.11A
802.11A is a completely different animal from 802.11B and 802.11G. Like 802.11G, an 802.11A network can deliver data at up to 54 Mbps. Additionally, multiple channels can be combined for even higher data rates. I converted the wireless network in my home to 802.11A a little over a year ago. While the standard is designed for a data rate of 54 Mbps, I am using what the access point manufacturer calls turbo mode to achieve data rates of 72 Mbps. If this were a true 72 Mbps, then it would mean that my wireless network would be almost as fast as my wired network, which runs at 100 Mbps. The sad truth is that 802.11A runs more slowly than specified. While running in Turbo mode, I usually get an average throughput of about 33 Mbps on my network. Even so, that's still much faster than 802.11B.

All of this speed comes at a price. 802.11A lacks the range of 802.11B and 802.11G. The 802.11A specification provides 12 nonoverlapping channels in the 5.8 GHz frequency range. This means that you can colocate up to 12 access points. Of course, if you are using turbo mode, you are using more than one channel and colocation becomes more of an issue.

In addition to the blazing speed, another good point of 802.11A is that it is much less prone to interference from other devices because it operates in the 5.8 GHz frequency range. At the time that this article was written, most cordless phones operate on a frequency of 2.4 GHz. Such phones often interfere with 802.11B and 802.11G networks. 802.11B and 802.11G networks are also subject to interference from microwave ovens. At this time, not many 5.8 GHz cordless phones are in use. Therefore, because of this and the fact that 802.11A is a less popular choice than 802.11B or 802.11G, these networks are less susceptible to interference than networks operating at 2.4 GHz.

Making the decision
There are a lot of factors to consider when choosing a Wi-Fi implementation. If you are building a new network, then I recommend using 802.11A. I say this because most hackers focus on 802.11B and 802.11G networks. There are few hacking tools available for 802.11A networks because few people use 802.11A. 802.11A is also much less susceptible to radio interference than 802.11B or 802.11G because it uses the 5.8 GHz frequency range.

However, if you have an existing wireless network, you may be better off using 802.11G. 802.11G will give you the speed of 802.11A, with a much smoother transition from 802.11B. Remember that 802.11G is compatible with 802.11B. 802.11A, on the other hand, isn't compatible with either 802.11G or 802.11B.
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