[MLB-WIRELESS] Hold off on buying wireless equipment for a fe w months!

[Tony Langdon]

>        It good to see a good turn out at the bbq, and a 
> special thanks 
> should go to Tyson for organising and providing for the event.

It was good.  And we haven't had a "post mortem" on the event yet. :-)
Let's say it was good to talk to a lot of people.  However, a suggestion is
perhaps we should have some means of identification - we know each other,
until we meet fact to face! :-)

And next time, we'd like a little more elevation LOL.

The topographical map of Melbourne was just awesome.  :)
> 
> I don't place comments very often on this group, but my view 
> is that if 
> possible hold off on buying wireless lan 11Mbit cards and 
> access points for 
> a number of months.
> 
> 1) 802.11b, even though rated at 11Mbit, realistically over any
>    distance greater than a couple of hundred feet, rarely yields
>    an effective transfer greater than 150kilobytes/sec, even with
>    high gain directional antenna. I have personally played with cisco
>    access points, and lucent cards  and come to that conclusion.
> 
> 2) You should wait to the middle of this year for the 802.11g (54Mbit)
>    to emerge, also based on the 2.4GHz, not 5GHz. Don't waste money on
>    the current stuff! Cards from many card manufacturers will hit the
>    streets in May, June 2002. The Melbourne wireless group 
> has a unique
>    opportunity to start off correctly. If its 5 times faster than
>    802.11b, then realistic transfers should be in the order of
>    150 x 5 = 750kilobytes/sec. I therefore urge people to hold off
>    till then, rather than waste money now, and replace the equipment
>    in a few months.

A couple of comments here.  

1.  Bandwidth is (more or less) inversely proportional to receiver S/N.
This means that as you make a link longer, you will have to lower the bit
rate to get data through.  There is no way around this.  Shannon's Law can
be used to determine the maximum bitrate a particular channel can handle.
So, don't expect anywhere near 54 Mbit/sec in our application on most links.
However, there may be some improvements in protocol efficiency.

Also note that with a 54 MHz bandwidth, the cards are unlikely to support
multiple channels, so there's an increased risk of mutual interference in
areas with a large number of links.

We will need to experiment here.  :)

2.  802.11g is going to be expensive, at least initially.  I think
realistically, we are going to have to support 802.11b for a while yet, and
far beyond 3 months time.  Similarly, there's likely to be the odd branch
which uses non 802.11b cards that will need to be routed in.

> 3) Some people may be getting excited  with the new 802.11a cards.
>    Whilst these cards do show a significant performance increase, they
>    are based on 5Ghz band. The cable, antenna, are far harder to buy,
>    and costly than 2.4Ghz.You need to use the 1 inch diameter
>    coax,thats costs upwards of $28/meter to drive any
>    signal to a remote antenna. 802.11a  is only good for internal
>    office communication, and not point to point in my opinion.

Agreed.  for most applications, 5 GHz is getting tricky to handle.  To do it
properly would mean dumping coax and using waveguide for the feedline.
Anyone for some "plumbing"? :)

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