* Under the 802.11g covers
You’ve likely heard that the first batch of 802.11g products was recently certified by the Wi-Fi Alliance. For the past year or so, commercial .11g products have seen some controversy, because a number of vendors released “802.11g-based” products before the IEEE ratified the final version of the standard last month.
However, now the .11g specifications are legit, and the Wi-Fi Alliance has sanctioned four access points and four PC Cards as successfully having completed Wi-Fi certification testing. The Wi-Fi Alliance is the vendor consortium that certifies interoperability among different vendors’ wireless LAN (WLAN) products once standards have been approved and at least three chipset vendors offer commercially available products.
The .11g products that have been Wi-Fi-certified come from the following vendors: Atheros, Broadcom, Intersil, Melco (a.k.a., Buffalo) Proxim, and Texas Instruments.
As you likely know, this flavor of WLAN standard runs in the 2.4-GHz range and will communicate with 802.11b clients (although the .11g network takes a performance hit when .11b clients associate with a .11g access point). It also runs at a maximum theoretical speed of 54M bit/sec and has a range, oh, of about 150 feet when communicating through interior walls.
802.11g WLANs use the same modulation technique – orthogonal frequency division multiplexing (OFDM) – as 802.11a, the 54M-bit/sec industry-standard WLAN that runs in the 5-GHz band. OFDM transmits large amounts of data over a radio wave by splitting a signal into multiple smaller sub-signals and transmitting them simultaneously at different frequencies.
OFDM differs from the modulation format for .11b WLANs, complementary code keying, which is a single-frequency waveform. The multifrequency nature of OFDM enables the higher data rates and boosts reliability of .11g and .11a networks in the presence of severe signal distortion due to multipath.
At one point, the FCC prohibited the use of OFDM in the 2.4-GHz band. Now, however, the common OFDM modulation format can now be used in both bands.
