Friday, June 1, 2007

Wireless standards for mobile ad-hoc networks


By Humayun Bakht

Wireless networks tend to offer numerous benefits, including wider coverage, cost reduction and data transmission at high speeds. In this article, we will investigate different available wireless standards as defined by the Institute of Electrical and Electronics Engineers (IEEE).

Developed back in 1997, IEEE 802.11 was the first wireless local area communication standard. Although IEEE 802.11 is very slow and can support data transmission up to 2 Mbps, its development opens a new chapter in the field of wireless communication. Nearly all of the existing or the newly developed wireless standards are either based on or are an extension of IEEE 802.11.

There are three formats using the IEEE 802.11 standard. They are 802.11a, 802.11b, and 802.11g. These are the most commonly used standards today. You'll see them in home networks, in laptops, coffee shops, airports, etc. Let's find out how they compare.

IEEE 802.11b is a Wireless Local Area Network (WLAN) standard that was developed in July 1999 and can offer a maximum bandwidth of 11 Mbps. The main benefit of IEEE 802.11b is its cost. This is mostly because network equipment for 802.11b costs less than some of the other wireless standards. IEEE 802.11b uses a 2.4 GHz frequency range. The 2.4GHz frequency is unregulated, meaning that there are many devices that could use this frequency range, such as cordless phones, microwaves, and even your laptop computer. As a matter of fact, all the standards which operate with 2.4 GHz frequency range are subject to the interference of other wireless services utilizing the same frequency range. This interference causes not only distraction in effective data transmission but also reduces the over all efficiency of various wireless equipment. However, in the case of IEEE 802.11b, this interference can easily be avoided by the installation of some extra equipment.

The 802.11a standard followed two years later, in 2001. It supports a maximum bandwidth of 54Mbps, which is one of the main benefits of using IEEE 802.11a. It's much faster than using 802.11b. Even though 802.11a is much faster than 802.11b, why isn't more widely used? 802.11a does have a couple of drawbacks. The first is the extra cost which is required to manage hardware equipment. IEEE 802.11a also uses 5GHz or above frequency for radio transmission. Moreover, 802.11a has been ratified to support interoperability among various vendors.