[LINK] US switch to dig TV - potential for Internet?

Stilgherrian stil at stilgherrian.com
Sat May 26 12:23:39 AEST 2007


On 26/5/07 10:43 AM, "rchirgwin at ozemail.com.au" <rchirgwin at ozemail.com.au>
wrote:
> Geez, Stil, get with the program. The whole purpose of all bandwidth is
> to allow "content producers" to stuff things down the pipe at "content
> consumers". All else is anarchy. What fool considers democratic use of
> spectrum when it can be sold to pigopolists for buckets of cash?

Sorry, yes, I am a dangerous anarchist. My apologies.


> Now. I haven't actually done much background reading on the relationship
> between channel width and data rates, so this is a "thought experiment".
> Please correct me, anyone with better clue.
> 
> If 10 Mbps symmetrical needs 20 MHz channels (ie, one bit per hertz),
> then *one* customer connection on a 70MHz carrier signal needs a channel
> from 60 MHz to 80 MHz; and per 100 MHz you have five channels. Even with
> oversubscription you get, say, 50 customers per 100 MHz.

What you're after here is the Shannon­Hartley Theorem, which says how much
data you can shove down a channel for a given bandwidth and signal-to-noise
ratio.

    http://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_law

Equations and I don't mix on a Saturday, but towards the bottom of the page
there's some useful approximations just right for this back-of-envelope
stuff.

Stil


-- 
Stilgherrian http://stilgherrian.com/
Internet, IT and Media Consulting, Sydney, Australia
mobile +61 407 623 600
fax +61 2 9516 5630
ABN 25 231 641 421









More information about the Link mailing list