[LINK] Senator Coonan on 7:30 Report

[Saliya Wimalaratne]

On Tue, Jun 19, 2007 at 09:17:18AM +1000, Jan Whitaker wrote:
> At 12:36 AM 19/06/2007, Saliya Wimalaratne wrote:
> >Another thing that happens with increasing distance is the
> >necessity of adjusting timing to suit longer distances -
> >this pretty much doesn't happen with consumer-level kit and isn't
> >part of the standard(s) as far as I'm aware.
> 
> Saliya, how can the guy from Optus stand up in front of a camera and 
> say such stupid things about the reasonable use of this 'new' 
> technology for remote locations? Seems to me that if there are dead 
> spots for mobiles because of lack of towers, there will be dead spots 
> for wireless access. Or are they going to pay for high speed 
> satellite data streams? Has anyone seen the detail of this 'new' 'plan' 
> (sic)?

Hi Jan,

Um; because they don't know any better? I've been on the receiving end
of sales pitches before ('yeah, sure, it will make you coffee, as long
as you sign here'). I couldn't speculate on <insert seller name>'s
motives but I'm sure others can :)

In real life, in general, the longer the range, the lower the frequencies 
used (and the lower the bandwidth available per 'channel'). Let's look
at NextG - 850MHz, thus, not class-licenced - but it will have similar 
properties to current 900MHz kit. 

To stay within the 1W EIRP for the class licence, 900MHz kit with a 
max-power transmitter and a small, average sensitivity mobile receiver 
might have a usable radius of about 8km if my calculations are correct-ish. 

If the NextG licence allows (for example) 4W EIRP, then the usable
distance becomes a little bigger - say a 15km radius. But all users 
'attached' to that receiver must share the spectrum - the more users, 
the lower the speed per user. So they're probably better off sticking to 
a lower EIRP and putting in more cells...

Again, to do super-long distances you either need to violate the power
rules and/or have better (more directional and/or sensitive) receiving kit. 

There are guys overseas that have done a 5GHz 300km WLAN point-to-point 
link that they tested at about 5Mbps throughput - but they were using 
600mW of tx power, what is claimed to be 'the best' receive sensitive
equipment in the world, and what looked like about 35dB of homemade antenna 
gain - an EIRP of about 175W! Not to mention the antenna heights (they
were, if I read correctly, about 1300m and 1700m)...

Regards,

Saliya