The first wireless LAN (WLAN) standard was created by the IEEE committee in 1997, and was called 802.11. However, 802.11 standard supported only up to 2 Mbps of bandwidth, and quickly became obsolete. Subsequently, IEEE created the 802.11a, and 802.11b standards.

The following are the advantages of the IEEE 802.11a standard compared to 802.11b:

• 802.11a uses 5GHz frequency band which is less crowded and hence has relatively smaller interference problem.
• 802.11a supports up to 54Mbps of bandwidth, which is much faster than the 11Mbps bandwidth provided by 802.11b standard devices.
• 802.11a offers as many as 12 non-overlapping channels. With more channels, larger number of users can be accommodated with no performance degradation.

Some of the disadvantages of using the 802.11a standard are:

• Not many client devices such as note book computers, PDAs support 802.11a standard. Most of these support either 802.11b or Bluetooth standards.
• It is more expensive compared to other contemporary technologies like 802.11b and Bluetooth.
• 802.11a standards are not compatible with 802.11b. Hence, devices manufactured complying with 802.11a and 802.11b respectively, are not interoperable.
• The distance covered will be slightly less compared to 802.11b due to higher operating frequency (5 GHz). Note that, higher the radio frequency,  lower the propagation distance for a given output power.

You may consider using 802.11g in place of 802.11a for reasons of cross compatibility.