Network managers should avoid buying pre-certified
802.11n products because of the poor performance of wireless
devices that use the protocol, analyst firm Burton Group has
warned.
Standards body the Institute of Electrical and Electronics
Engineers has been working on a faster version of 802.11 for
several years. The new standard, 802.11n, is designed to turn a
weakness of wireless technology, known as multipath interference,
into a strength by using Mimo (multiple input, multiple output)
technology.
Mimo uses multiple antennas and transmits information over
multiple paths simultaneously, thereby boosting effective
throughput to hundreds of megabits per second, depending on the
antenna configuration.
Paul DeBeasi, senior analyst at Burton Group, said in a recent
paper that the 802.11n standard had been undergoing intense
scrutiny, and a group of leading wireless Lan suppliers had formed
the Enhanced Wireless Consortium (EWC) to try to break the deadlock
in the IEEE 802.11n committee.
"They were ultimately successful, and a single draft document -
draft one - was formed as the basis for the new standard," said
DeBeasi.
Many suppliers are aggressively promoting pre-standard 802.11n
products, but DeBeasi urged network managers to avoid purchasing
pre-standard 802.11n products.
"Many suppliers now sell 'pre-n' products based on an early
draft of the 802.11n standard. Early tests show that these products
do not provide supplier interoperability, and can negatively affect
existing 802.11g networks," he warned.
Other problems highlighted by DeBeasi include pre-n products
exhibiting mediocre throughput results and offering a signal range
that is worse than 802.11g.
There is also no cross-supplier compatibility and pre-n products
will require hardware upgrades to support the final 802.11n
standard.
More information
www.ieee802.org
www.enhancedwirelessconsortium.org
What does the draft 802.11n specify?
802.11n is a draft specification for a faster Wi-Fi protocol
with a theoretical bandwidth of 540mbps. It uses Mimo (multiple
input, multiple output) to enable the deployment of multiple
transmitter and receiver antennas to increase data throughput,
through a technique known as spatial multiplexing.
In May 2006, draft 1.0 failed to pass the first ballot and
received more than 12,000 comments, although many of these were
minor in nature.
The eventual standard will operate in the 2.4GHz (802.11b/g) and
5GHz (802.11a) frequency bands. The standard will be
backward-compatible with 802.11b/g/a and will specify use of Mimo
technology. It is likely that multiple Mimo antenna configurations
will be allowed and that suppliers will offer products at several
price/performance points.
The IEEE expects the 802.11n standard to achieve final working
group approval by January 2008.