On Tuesday, September 13, 2016 at 3:26:04 PM UTC-7, Tim Wescott wrote:
> I can't Google for this -- I just tried.
The symmetric vs. asymmetric reminds me of a different, and currently
interesting, point.
When WiFi started, it was assumed symmetric, at least in terms of the
power requirements for each side. Now we have many portable
devices (such as cell phones) that can't really afford the power to
reach some stations, but where those stations can afford the power.
I only found recently that the original design for the cellular phone
system was for car phones, with a good power source, and then
someone figured out that the same system would work with battery
powered handsets. But I presume that has been included in newer
cell phone systems.
The OP was asking about cost, but it also comes up in power
considerations.
On Tuesday, September 13, 2016 at 3:26:04 PM UTC-7, Tim Wescott wrote:
> I can't Google for this -- I just tried.
> Broadcast radio, and DirectLink satellite TV, have Really Expensive
> transmitters to serve lots and lots of cheap receivers, because it
> minimizes total system cost.
> "Old style" satellite TV had (fairly) inexpensive transmitters and (until
> people put them in their back yards) a few big expensive receivers (and
> antennas). Because -- it minimizes total system cost (at least until
> everyone put one in the back yard).
It is actually more interesting. In the days before backyard TVRO
antennas, the FCC required them to be fairly big. Partly that was
necessary to make sure that they pick up one satellite within the
diffraction width. But the FCC requirement was bigger than it
needed to be. Those wanting to build home receivers petitioned
the FCC to allow for smaller ones.
The power per channel for the big antenna satellites is about
five watts. It takes a certain size to get enough signal to get
above the thermal noise, but that gets smaller as amplifiers
get better.
When they are owned by TV networks, the cost is a fairly small
fraction of the cost of running a network, and a good signal is
pretty important. For home use, cost is much more important
(and it isn't really the number that matter) and signal not quite
as important.
> Is there a name for this sort of economic decision? I'm trying to write
> some material for training new engineers, to give them an idea of how
> decisions like this are made.
As someone noted, Pareto is part of the answer, but it seems to me
part of what you are asking is economy of scale. Making a lot of
them decreases the cost per item. As quantity went up, they got
pretty good at making them cheap enough, if you had enough yard
to put one in. Mostly that was for rural homes.
The small dish system takes about 100W per channel, (in both cases
covering the whole US). That allows for a 20 times smaller dish.
(I didn't look up the numbers, but I think they are close.)
-- glen
Reply by Eric Jacobsen●September 13, 20162016-09-13
On Tue, 13 Sep 2016 17:25:56 -0500, Tim Wescott
<seemywebsite@myfooter.really> wrote:
>I can't Google for this -- I just tried.
>
>Broadcast radio, and DirectLink satellite TV, have Really Expensive
>transmitters to serve lots and lots of cheap receivers, because it
>minimizes total system cost.
>
>"Old style" satellite TV had (fairly) inexpensive transmitters and (until
>people put them in their back yards) a few big expensive receivers (and
>antennas). Because -- it minimizes total system cost (at least until
>everyone put one in the back yard).
>
>Is there a name for this sort of economic decision? I'm trying to write
>some material for training new engineers, to give them an idea of how
>decisions like this are made.
>
I'm not sure I follow your satellite TV example, since the earth
station expense for U/L and D/L didn't differ that much with the big
sites, i.e., the TX wasn't necessarily cheaper than the RX and was
probably more expensive.
Cellular systems are comparable, though; e.g., handsets are way
cheaper than basestations, by many orders of magnitude. So are cable
systems and many similar systems.
The term "big stick" gets used sometimes in these contexts to refer to
a large, expensive central antenna or tower, such as for a broadcast
TV/Radio transmitter.
I think the terms you used in the title are appropriate. They do
apply to and are often used to describe the channel usage as well;
e.g., many systems have much more bandwidth and data capacity in the
downstream direction than upstream, especially as experienced by a
single user terminal, so the term "asymmetric" is often applied,
especially if the user terminal uses a different bandwidth, channel,
or waveform than the provider. So, since "asymmetric" is used to
describe the channels, physical layers, throughput, etc., I don't know
why it wouldn't be appropriate to also apply it to the terminal
economics.
Reply by Cedron●September 13, 20162016-09-13
>I can't Google for this -- I just tried.
>
>Broadcast radio, and DirectLink satellite TV, have Really Expensive
>transmitters to serve lots and lots of cheap receivers, because it
>minimizes total system cost.
>
>"Old style" satellite TV had (fairly) inexpensive transmitters and (until
>people put them in their back yards) a few big expensive receivers (and
>antennas). Because -- it minimizes total system cost (at least until
>everyone put one in the back yard).
>
>Is there a name for this sort of economic decision? I'm trying to write
>some material for training new engineers, to give them an idea of how
>decisions like this are made.
>
>--
>
>Tim Wescott
>Wescott Design Services
>http://www.wescottdesign.com
>
>I'm looking for work -- see my website!
Perhaps "Pareto optimal" is the term you are looking for.
https://en.wikipedia.org/wiki/Pareto_efficiency
"Pareto efficiency, or Pareto optimality, is a state of allocation of
resources in which it is impossible to make any one individual better off
without making at least one individual worse off. The term is named after
Vilfredo Pareto (1848–1923), an Italian engineer and economist who used
the concept in his studies of economic efficiency and income distribution.
The concept has applications in academic fields such as economics,
engineering, and the life sciences."
Ced
---------------------------------------
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Reply by John Larkin●September 13, 20162016-09-13
On Tue, 13 Sep 2016 17:25:56 -0500, Tim Wescott
<seemywebsite@myfooter.really> wrote:
>I can't Google for this -- I just tried.
>
>Broadcast radio, and DirectLink satellite TV, have Really Expensive
>transmitters to serve lots and lots of cheap receivers, because it
>minimizes total system cost.
>
>"Old style" satellite TV had (fairly) inexpensive transmitters and (until
>people put them in their back yards) a few big expensive receivers (and
>antennas). Because -- it minimizes total system cost (at least until
>everyone put one in the back yard).
>
>Is there a name for this sort of economic decision? I'm trying to write
>some material for training new engineers, to give them an idea of how
>decisions like this are made.
There is also the "ricochet" network, where nodes pass packets to
their destination.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Reply by Rob Gaddi●September 13, 20162016-09-13
Tim Wescott wrote:
> I can't Google for this -- I just tried.
>
> Broadcast radio, and DirectLink satellite TV, have Really Expensive
> transmitters to serve lots and lots of cheap receivers, because it
> minimizes total system cost.
>
> "Old style" satellite TV had (fairly) inexpensive transmitters and (until
> people put them in their back yards) a few big expensive receivers (and
> antennas). Because -- it minimizes total system cost (at least until
> everyone put one in the back yard).
>
> Is there a name for this sort of economic decision? I'm trying to write
> some material for training new engineers, to give them an idea of how
> decisions like this are made.
>
Upfront v. recurring?
--
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order. See above to fix.
Reply by Tim Wescott●September 13, 20162016-09-13
I can't Google for this -- I just tried.
Broadcast radio, and DirectLink satellite TV, have Really Expensive
transmitters to serve lots and lots of cheap receivers, because it
minimizes total system cost.
"Old style" satellite TV had (fairly) inexpensive transmitters and (until
people put them in their back yards) a few big expensive receivers (and
antennas). Because -- it minimizes total system cost (at least until
everyone put one in the back yard).
Is there a name for this sort of economic decision? I'm trying to write
some material for training new engineers, to give them an idea of how
decisions like this are made.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
I'm looking for work -- see my website!