[MLB-WIRELESS] The Age Technology article

Sat Nov 16 16:31:14 EST 2002

Hi Matt.

Hope my email clears it up.

The original 802.11 standard used 2.4Ghz and Direct Sequence Spread Spectrum
Modulation (DSSS) or Frequency Hopping Spread Spectrum Modulation (FHSS). Both
of which have been used as modulation schemes by military for decades. Speed was
1 or 2Mbps and even included infra red!

The amended 802.11 standard, 802.11b, uses 2.4Ghz and standardised on the Direct
Sequence Spread Spectrum Modulation (DSSS). Link speed is 11Mbps

802.11a uses 5Ghz and Orthogonal Frequency Division Multiplexing Modulation
(OFDM) Link speed is 54Mbps. OFDM is a more complex and newer modulation scheme
than DSSS or FHSS, thus the speed.

802.11g is designed to use 2.4Ghz standard OFDM modulation to run at 54Mbps.
2.4Ghz is chosen so that there is an ability to be backwards compatible with
802.11b due to it's wide installation. For example D-Link worldwide has sold
over 25 million wireless products with thw majority of those being 802.11b.

Texas Instruments developed PBCC Modulation so that they could run at 22MB on an
802.11b network. D-Link uses their chipset in their AirPlus range. Thus the
commonly referred "802.11b+" product. Obviously these devices can only "talk" to
others running the same modulation scheme, so therefore can only run in 802.11b
mode with DSSS modulation (standard 802.11b) or "802.11b+" mode in PBCC
modulation (enhanced 802.11b). Oh and guess what? PBCC is an option for 802.11g
standard so can you see what Texas Instruments are trying to do here?

The AirPlus product is popular because it offers twice the speed of  standard
11MB (and twice the WEP encryption), while maintaining the range advantage of
2.4Ghz 802.11b. at over 15 metres AirPlus is around the same speed as 802.11a,
due to the high propagation loss inherent in higher frequencies such as 5Ghz
802.11a.

Hope this helps,

Michael Florence
michael at dlink.com.au

"Dave Keller" <david at bay.net.au> on 16/11/2002 08:56:08 AM

 To:      "melbourne wireless" <melbwireless at wireless.org.au> 

 cc:      (bcc: Michael Florence/Sales/DLINK-AUST)            

 Subject: Re: [MLB-WIRELESS] The Age Technology article       

Similar to the 56k modem standards, their was the same battle between two
different methods to get the higher speed connections. While the IEEE were
off having their little infighting trying to decide which standard to use..
Texas Instruments had their standard, based on PBCC, which is sometimes
called 802.11b+ which is sort of backward compatible with 802.11b. If they
cant talk at "802.11b+" they just start talking 802.11b.

http://geelong.wireless.org.au/modules.php?name=News&file=article&sid=4&mode
=&order=0&thold=0

Ciao,
Dave.

----- Original Message -----
From: "Matt Pearce" <mattpearce at optusnet.com.au>
To: "melbourne wireless" <melbwireless at wireless.org.au>
Sent: Friday, November 15, 2002 7:43 PM
Subject: [MLB-WIRELESS] The Age Technology article

> Hey all,
>
> Just read this interesting little article in the age, it claims that
802.11g
> is a 20mb connection and is compatible with 802.11b, correct me if I am
> wrong but I though that the 20mb connection was used by people such as
> D-Link and was not actually a ratified standard.  I also thought that it
is
> only compatible when it drops back to 11mb speeds.  And I also thought
that
> 802.11g is 54mb connection on 2.4G ??
>
> Anyone care to correct me or is this reporter correct ??  See the link
below
> for the full article.
>
> http://www.theage.com.au/articles/2002/11/09/1036308526730.html
>
> Matt.
>
>
>
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