Tale of the Tech Tape
Controversy has already plagued 802.11g. To finally get 802.11g out the door, by
agreeing to disagree after years of 802.11 committee fights finally proved that
neither one could get enough committee votes to gets its own pet 22Mbps solution
official 802.11g blessing. The end result is that 802.11g is a compromise
incorporating no fewer than four different wireless standards
For 802.11b compatibility, 802.11g incorporates 802.11b's Complementary Code
Keying (CCK) to achieve bit transfer rates of 5.5 and 11Mbps in the 2.4Ghz band.
In addition, 802.11g adopts 802.11a's Orthogonal Frequency Division Multiplexing
(OFDM) for 54Mbps speeds but in the 2.4Ghz range.
802.11g also comes with a pair of optional, and incompatible, modes to achieve
throughput ranges in the 22Mbps range. These are Intersil's CCK-OFDM mode with a
maximum throughput of 33Mbps and TI's Packet Binary Convolutional Coding
(PBCC-22), with a throughput range of 6 to 54Mbps.
Both 802.11a and 802.11g offers up to 55Mbps speeds in the lab. In the field,
802.11a delivers about 20Mbps. That may not sound like much unless you know that
802.11b's 11Mpbs theoretical speed is more often 4Mbps in practice. Early
versions of 11g chipsets have real-world speeds in the 6Mbps range according to
vendors.
It's also clear from early tests that 802.11g has the same, or perhaps slightly
better, range than 802.11b. On the other hand, 802.11a seems to maintain a
higher throughput out to the limit of its range, while 802.11g appears to run
out of steam at its extreme range.
Of course, 2.4GHz, with interference from everything to satellites to microwave
ovens to high-end wireless phones, has to contend with a lot of radio frequency
(RF) noise. This can result in lower throughput, which in turn can effectively
reduce its range. 802.11a's 5Ghz, on the other hand, has much less interference
to deal with and it's part of the spectrum appears from FCC regulations likely
to stay free of most other RF devices.
Finally, 802.11g can handle only three channels at once. The first generation of
Aethero's chips though could handle eleven channels at once and the next
generation supports thirteen channels in the US market and nineteen in Europe.
Thus, in a business environment, with multiple users, even if components were
delivering 55Mbps speeds, 802.11a would effectively have more bandwidth in heavy
usage situations.
It's clear that neither technology is a slam-dunk over the other. Technology
issues though are only part of the story.
