High-Speed Wireless LAN Options 802.11a and 802.11g

The Wireless Local Area Network (WLAN) industry has emerged as one of the fastest-growing segments of the communications industry. WLAN equipment shipments grew to almost 12 million units in 2001 and market research firm Cahners In-Stat expects sales of wireless network cards and WLAN base stations to grow from $1.9 billion in 2001 to $5.2 billion in 2005.
This growth was due, in large part, to the introduction of standards-based WLAN products. These products – based on the 802.11b standard – are faster, lower in cost, and simpler to setup and use than previous generation products. The majority of WLAN products today communicate at speeds up to 11 megabits per second (Mbps).

Two new WLAN standards are now emerging and will deliver higher speeds, up to 54 Mbps, to WLAN users. These new standards are known as 802.11a and 802.11g. To help you to better understand these new technologies, the Wireless LAN Association (WLANA) has developed this
white paper as an introduction to high-speed WLAN options.

The Road to High-Speed Wireless LAN
You may be wondering why 802.11b products came before 802.11a. The letters after the number “802.11” indicate the order in which standards were first proposed, not the order in which products appear. The first wireless LAN standard, 802.11, was approved by the Institute of Electrical and Electronics Engineers (IEEE) in 1997 and supported speeds up to 2 Mbps.

In 1999, the IEEE approved both the 802.11a and 802.11b standards. 802.11a specified radios transmitting at 5 GHz and at speeds up to 54 Mbps using orthogonal frequency division multiplexing (OFDM) modulation technology. The 802.11b standard – now popularly known as Wi-Fi – specified operation in the 2.4 GHz band (also known as the ISM band) and could achieve speeds up to 11 Mbps using direct sequence spread spectrum (DSSS) technology. Because DSSS is easier to implement than OFDM, 802.11b products appeared on the market first, starting in late 1999. Since then, 802.11b products have been widely deployed in corporations, small offices/home offices (SOHO), in residential home and in public locations (Wi-Fi “hotspots”). Products bearing the Wi-Fi logo conform to the 802.11b standard, have passed an interoperability certification test defined by the Wireless Ethernet Compatibility Alliance (WECA) and have received permission from WECA to use the logo. In early 2002, the first end-users products based on the 802.11a standard were shipped. Currently, these products are all based on chipsets from a single vendor. WECA has announced that it is defining an interoperability certification test for 802.11a products, which will used as soon as the products are available based on a second vendor's chipset. Products passing this test will be known as Wi-Fi5 compatible.

In early 2001, the FCC announced new rules allowing additional modulations in the 2.4GHz range. This allowed IEEE to extend 802.11b to support higher data rates, resulting in the 802.11g standard, which is now in draft stage and expected to be completed and approved by the end of 2002. 802.11g defines new data rate, up to 54 Mbps, at 2.4Ghz using ODFM, while at the same time providing backward compatibility with 802.11b at speeds up to 11 Mbps using DSSS.