
5G Beam-Steering Antennas: More Accurate, Less Power Hungry - rbanffy
https://spectrum.ieee.org/tech-talk/telecom/wireless/5g-beamsteering-antennas-more-accurate-less-power-hungry
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milankragujevic
I'm sorry for hijacking the thread, but why is it that air (LTE) can handle
much higher bandwidth than copper (i.e. DSL or DOCSIS)? I can easily get 150
Mbps speed per device, but can barely get DSL that's 10 Mbps (and that's over
VDSL2!). The distance from the DSLAM to the DSL modem by wire is less than the
distance from the base station / cell tower and the LTE modem by air. Does air
have more bandwidth even though there are many more signals and
users/subscribers than with DSL? I don't know, can anyone explain this to me?

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ucaetano
> much higher bandwidth than copper

It can't. Coax can easily support Gbps connections (I used to have a 800 Mbps
connection where the last few meters were over regular coax).

Now if you're talking about "why can't my copper twisted pair support that
bandwidth", then it is a function of quality (the twisted pair is likely old,
heavily bended, subject to interference, and running over old technologies.

Bandwidth is essentially a function of 2 things: spectrum availability
(measured in Hz) and spectral efficiency (measured in bits/second/Hz).

For example, if a carrier "owns" 20 MHz of spectrum (let's say, from 700 MHz
to 720 MHz), split in two symmetrical up/down channels, with a spectral
efficiency of 4bps/Hz (a common value for LTE), and the cell towers have 3
sectors, each cell tower can provide 20 _4_ 3/2 120 Mbps up and down (although
only 40 Mbps max per device, since a device can only be in one sector).

In wired communications, spectrum is less of a limit: every single wire has
the full spectrum available. And if you are using fiber, then there is no
interference, both from outside the wire or from different signals.

So air will never beat wired, because every single strand of wire has, in
practice, the entire capacity of air.

PS: There are more things in play, such as attenuation, actual frequencies
used (1 to 2 MHz has 1 MHz of spectrum; 1 to 2 GHz has 1000x more spectrum and
therefore more capacity), etc.

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foobarian
IIRC the wireless modulations got more attention because of the spectrum
scarcity and so are very efficient coming close to the Shannon limit. I don't
know if the same is true for wired; at least Ethernet uses a pretty dumb
modulation and started out focusing on other useful features such as simple
hardware, listen before talk, etc.

~~~
ucaetano
You don't really care that much about modulation when you have gigahertz of
spectrum to work with, and the cost to add another wire (or fiber) is
marginal.

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Nokinside
5G antennas are getting close to AESA (active electronically scanned array)
radars used in military (X-band is 8 to 12 GHz). Unlike radars in fighters, 5G
array can't cost millions per unit.

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sandworm101
They dont. The power levels are less than 1% of military radars. Plus mass
production. They are talking 10,000$ per unit, which isnt all that bad for
cell equipment that can aim itself.

Military radars are for detecting quiet targets, not cellphones wanting
internet. It is total apples and oranges in terms of energy levels.

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fooker
10000$ isn't very good either, because 5G needs far more base stations (by
about an order of magnitude) compared to 3G or LTE.

~~~
ars
$10,000 is nothing for that kind of thing - installation costs way more than
that. Just renting the area from the owner is several thousand per _month_.

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vvanders
Yeah, I've heard from ham types that it's really common to see near 7-figure
buy-outs for prime tower _land_ (50' x 50' \+ access) before even talking
about costs of putting up 100'\+ tower, power and hardware.

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TheSpiceIsLife
This gave me a chuckle:

“The beam can also be split and delivered to multiple target objects at the
same time _artificially and intelligently._ ” (emphasis mine).

What does that even mean?

Just managed to chuck in the words _artificial_ and _intelligence_ right
before the article ended.

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rubidium
I think you're over-reacting.

artificially: by means of human (or in this case programmed) intervention
rather than naturally.

intelligently: in a way that maximizes efficiency.

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dakr
An aside, but when it comes to electronic beam-steering, it's hard not to talk
about LOFAR[1], a low-frequency radio interferometer for astronomy spread
across Europe.

[1] [https://en.wikipedia.org/wiki/LOFAR](https://en.wikipedia.org/wiki/LOFAR)

