When should you use 802.11a versus 802.11g?

As such I've broken this down into two sections. The first, entitled "Why people like myself love 802.11a" and the second entitled "Why the uninformed and inexperienced like 802.11g."

Why I love 802.11a

1. Throughput
   1. 802.11a will give you 28-32 Mbps effective throughput.
   2. 802.11g will give you 20-24 Mbps effective throughput.
   3. In mixed 802.11b/802.11g mode, 802.11g clients will get about 7-9 Mbps effective throughput.

2. Spectrum management
   1. When using 802.11a for wireless LAN, most parts of the globe allows for 8 non overlapping channels (inc. UK, US, AUS, CAN, etc)
   2. 802.11b/g on the other hand has a maximum of 3 non overlapping channels anywhere in the world. The lower numbers of non overlapping channels results in more a much more difficult wireless LAN deployment as soon as you start deploying in any medium to high density environments.
   3. There are a couple of ratifications coming through to do with automatic channel allocation and once through many spectrum management bodies have promised to DOUBLE the spectrum available for the 5GHz equipment. This will just make everyone's lives a little bit easier.

3. Spectrum cohabitation
   1. 802.11a operates in the 5.15GHz—5.35GHz range which used almost solely for 802.11a wireless LAN throughout the world.
   2. Both 802.11b and 802.11gg operate in the same part of the spectrum as your microwave emissions, many cordless phones, Bluetooth devices (including mobile phones), any MANY other Industrial, Medical and Scientific instruments. (The 2.4GHz was declared available many years ago as the ISM band… specifically for Industrial, Medical and Scientific device radiation)

Why other people like 802.11g

1. Compatibility - 802.11g is backwards compatible with 802.11b. If you have a 2-4 year old 802.11b Wi-Fi Compliant wireless card, it will almost definitely work with any ratified 802.11g equipment.

2. Cost - No upgrade cost to work with new equipment. Of course this is a double edge sword (ref: speed issues in previous section).

3. Range - At full power and the biggest antennae you can use in each of the spectrums 802.11b/g will give you more range. There are a number of factors and variable to the whole range equation. Many people believe that you get much less range out of 802.11a than 802.11b/g. Well, it's true in many cases and false in others. Here are the variable in such as equation
   1. Power output and RF governing bodies - The reason that most 802.11a networks go only a half as far as 802.11b networks is the legal restrictions in many countries. (US example).
      1. 802.11b/g is restricted to 36dBm; that's 4 Watts of power!
      2. 802.11a for Wireless LAN is restricted to 23dBm; only 200mW (95% less than 802.11b/g)
   2. Transceiver design - There was a lot of work done on the 2.4 GHz transceivers initially to increase their range however little was done on the 5GHz ones (802.11a). This resulted in much poorer quality equipment simply because the R&D had not been done. This has been rectified some what and the throughput, signal quality and receiver sensitivity have all increased over the past 12 months.

So now you need to make up your own mind. If you get a 802.11a/b/g card I recommend the new Cisco ones due to their unbeatable throughput and operational distance; however a Netgear card will still work if you're close enough.

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