[LINK] Coalition hasn't checked its s... (abc.net.au)
tomk at unwired.com.au
Thu Feb 16 23:38:55 AEDT 2012
> -----Original Message-----
> From: link-bounces at mailman.anu.edu.au
> [mailto:link-bounces at mailman.anu.edu.au] On Behalf Of Antony Barry
> Sent: Thursday, 16 February 2012 9:48 PM
> To: Link list
> Subject: [LINK] Coalition hasn't checked its s... (abc.net.au)
> Coalition hasn't checked its satellite NBN facts. Here they
> http://www.abc.net.au/technology/articles/2012> /02/16/3432368.htm
Interesting article. It needs a little bit of de-gaussing.
Those engineers argued they had spent two years doing capacity planning,
and said the company could probably have "kludged together" up to 10GHz
of total leased satellite capacity to deliver the NBN to rural areas;
that's apparently around one-quarter the total capacity available in
Australia, and around 10 per cent of the 90GHz in additional capacity
the two planned NBN Co satellites will contribute.
Interesting. 10 GHz equals 1666 users at 6 mbits each, per footprint.
Each Transponder has a footprint. Therefore 32 Transponders equals
53,333 6 Mbps Simultaneous users divided by battery capacity.
Turnbull, who fell into a familiar tempo by deriding NBN Co's plan as a
'Rolls-Royce' solution in his response to the announcement, readily
concedes that Ku-band satellites are an inadequate solution for
providing satellite broadband, instead conceding that the Ka-band birds
NBN Co is buying are necessary to provide reliable 12Mbps services to
large numbers of customers (Ka-band systems operate in the 26.5 to 40GHz
range and offer higher throughput but are more susceptible to
interference from ground weather conditions).
26.5 to 40 = 13.6 GHz. Or 13500 Mhz (with 6 Mbps per MHz).
Assuming that spectrum is contiguously available (it's currently not)
and it doesn't interfere with other land stations (it would in
Carnarvon) then that allows 72533 Australians to enjoy simultaneous
connectivity to the internet at a download speed of 12 Mbits each. (When
the batteries are new or the sun is at full strength. (Lunchtime).
(By the time our Satellites are launched we will need remote access for
approximately 720000 Australians so assuming 2.3 per household, that's
313,043 remote households or a contention ratio of 4.31:1.
Most satisfactory and damn good (current known data environment) design.
However, for the rest of Australia, that then puts the Newsat offer in a
different perspective. For the future Data services that will be
required direct to device, (Car/Truck/Train/Plane/Tablet/Phone) it looks
like the NBN Satellites will be inadequate to offer coverage in that
area. We saw this problem in 1997 with Jasaurus (See Me Wee 3) when 5
Gigabits was going to last for a decade. I think from memory it lasted
four months before it was full.
i.e.: Current capacity planning is at it's outside limit giving Newsat
probably the last laugh.
Just where this capacity will come from, however, he has not said.
Newsat might offer a bit of capacity with its Australia-focused Jabiru-2
satellite offers Ku-band connectivity, while its Jabiru-4 will offer
6GHz of Ka and Ku-band coverage across the Pacific Ocean region
(including Australia). However, its Jabiru-1 will deliver 7.6GHz of
direct Ka-band capacity primarily in a swathe from eastern Africa to
India; Jabiru-3 focuses Ka-band coverage on Europe and Africa; and
Jabiru-5 covers North America, South America, and western Africa.
The Spectrum problem is not so much a downlink problem as an uplink one.
I personally would have handled the overhead thing slightly differently.
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