Careful planning in choosing which Wi-Fi standard your WLAN will be based on will help you avoid headaches and wasted money.
802.11b has been on the market the longest, and that means that there's a lot of 802.lib-compliant hardware on the market. Now that 802.llg and 802.11a have arrived on the scene, the prices on 802.11b hardware have fallen considerably. If you shop for 802.11b equipment, you are bound to find many bargains.
In most WLANs, the likely throughput offered by 802.11b (6-7 Mbps) is plenty, so this may be the best way for you to go. If you feel that you need more speed in the future, you can get an 802.11g AP now and upgrade the wireless NICs to 802.llg in the future.
802.llg access points are backward-compatible with most 802.11b NICs, meaning that 802.11b devices work with an 802.llg AP, but only at their normal speed, not at the higher speed offered by the 802.llg standard. This enables you to purchase a faster AP and to upgrade cards to take advantage of the higher speed as you can afford it. However, the performance of some 802.11g APs suffers in a mixed 802.11b/g WLAN. If you take this route, your 802.11g equipment may not operate at full throughput when it shares an AP with 802.1 lb devices.
Note:Some older 802.11 b hardware may not interoperate with 802.11 g hardware. Older 802.11 b devices may not be upgradeable, or able to support new security standards (such as 802.11 i or Wi-Fi Protected Access). Consider this if you decide to purchase older equipment and save money, or if you are combining components of an older network with new ones.
802. 11g hardware is newer and costs more than devices based on 802.11b, but it supports higher throughput (typically not over 21 Mbps), and is more likely to support future firmware upgrades for security and performance. 802.llg operates in the same 2.4 GHz frequency range, so it is susceptible to the same interference as 802.11b devices.
802.11a has similar (or higher) throughput to 802.llg devices, but it is not compatible with either 802.11b or 802.11g equipment. 802.11a operates in the 5 GHz range and isn't as susceptible to the same interference as 802.11b or 802.llg devices. 802.11a works better than 802.llg in environments where there is a lot of network traffic; if your network is going to see heavy use by many users then you will see better performance with 802.1 la compliant equipment.
However, the effective range of 802.11a tends to be less than 802.11b or 802.llg, so you may see performance drop unless you're close to the AP. This may require you to invest in more than one AP to provide coverage for your entire house or office.