3 ms·

Multi-kilometer and sub-terahertz communications at extreme frequency bands

42 points by wglb 4y ago

fb03 4y ago
Can someone ELI5 the advantage of terahertz (or sub-) communications over the plethora of currently available alternatives? Is there any edge to switching a signal to that high of a carrier frequency?
- charlescarver 4y ago
  More bandwidth! Also depending on frequency, you might be able to use the EM spectrum more efficiently (e.g., multiple narrow wavelength lasers).
  - klabb3 4y ago
    People focus too much on bandwidth, but latency is more important. Bandwidth has increased exponentially, but the speed of light has stayed the same for more than 10 years now.
    - hulitu 4y ago
      > but the speed of light has stayed the same for more than 10 years now. Don't worry, i bet that in the next time we will read on HN about revolutionary methods to increase the speed of light, just like those articles about fusion, charging or batteries. /s
      - greenbit 4y ago
        The news about the breakthrough in FTL will reach Andromeda long before that patent clerk's quaint musings about bendy space ever will.
    - JumpCrisscross 4y ago
      > the speed of light has stayed the same for more than 10 years now Little practical communication is constrained by the speed of light.
    - greenbit 4y ago
      It's usually stated in meters per second, a somewhat dry, cognitively inaccessible number. Try flipping it around though .. 3.336 microseconds per kilometer People, software engineering types anyway, have a feel for what a microsecond is; a CPU can get a quite noticeable amount of work done in a microsecond - and it takes three and a third of those just to reach the coffee shop on the corner! Jump across a continent, and now you're talking latencies on par with early 1980s disk systems. That being said, there's not too much you can do about the latency, 3E8 is the law, so we may as well fiddle with bandwidth.
      - ztetranz 4y ago
        Sort of related. "We can't send email more than 500 miles" https://web.mit.edu/jemorris/humor/500-miles https://web.mit.edu/jemorris/humor/500-miles
- BenjiWiebe 4y ago
  Because it's as-yet unused. The more spectrum we can get useful things done with, the more room there is for all those useful things.
amatecha 4y ago
I was wondering why they used the term "sub-terahertz" (isn't basically the entire RF spectrum "sub-terahertz"?), and it seems to refer to the ~75-300ghz range [0][1], including the W and D bands. While looking into this, I learned that terahertz frequencies are called THF or "tremendously high frequency"[2], which I thought was pretty funny. Pretty used to HF, VHF, UHF etc. but never heard of "THF" until now! [0] https://www.rfwireless-world.com/Terminology/Sub-THz-Bands-and-Frequencies.html https://www.rfwireless-world.com/Terminology/Sub-THz-Bands-a... [1] http://www.brave-beyond5g.com/index.php/sub-thz/ http://www.brave-beyond5g.com/index.php/sub-thz/ [2] https://books.google.ca/books?id=K9N1TVhf82YC&pg=PA7&redir_esc=y#v=onepage&q&f=false https://books.google.ca/books?id=K9N1TVhf82YC&pg=PA7&redir_e...
- pythonguython 4y ago
  Starting from VHF, the ITU names the bands in this order: very, ultra, super, extremely, and tremendously high. I once asked several of my friends who don’t know anything about radio to try to name the bands in ascending order after I scrambled them, and they all gave me different, incorrect answers.

42 points by wglb 4y ago

fb03 4y ago

Can someone ELI5 the advantage of terahertz (or sub-) communications over the plethora of currently available alternatives? Is there any edge to switching a signal to that high of a carrier frequency?

charlescarver 4y ago
More bandwidth! Also depending on frequency, you might be able to use the EM spectrum more efficiently (e.g., multiple narrow wavelength lasers).
- klabb3 4y ago
  People focus too much on bandwidth, but latency is more important. Bandwidth has increased exponentially, but the speed of light has stayed the same for more than 10 years now.
  - hulitu 4y ago
    > but the speed of light has stayed the same for more than 10 years now. Don't worry, i bet that in the next time we will read on HN about revolutionary methods to increase the speed of light, just like those articles about fusion, charging or batteries. /s
    - greenbit 4y ago
      The news about the breakthrough in FTL will reach Andromeda long before that patent clerk's quaint musings about bendy space ever will.
  - JumpCrisscross 4y ago
    > the speed of light has stayed the same for more than 10 years now Little practical communication is constrained by the speed of light.
  - greenbit 4y ago
    It's usually stated in meters per second, a somewhat dry, cognitively inaccessible number. Try flipping it around though .. 3.336 microseconds per kilometer People, software engineering types anyway, have a feel for what a microsecond is; a CPU can get a quite noticeable amount of work done in a microsecond - and it takes three and a third of those just to reach the coffee shop on the corner! Jump across a continent, and now you're talking latencies on par with early 1980s disk systems. That being said, there's not too much you can do about the latency, 3E8 is the law, so we may as well fiddle with bandwidth.
    - ztetranz 4y ago
      Sort of related. "We can't send email more than 500 miles" https://web.mit.edu/jemorris/humor/500-miles https://web.mit.edu/jemorris/humor/500-miles
BenjiWiebe 4y ago
Because it's as-yet unused. The more spectrum we can get useful things done with, the more room there is for all those useful things.

amatecha 4y ago

I was wondering why they used the term "sub-terahertz" (isn't basically the entire RF spectrum "sub-terahertz"?), and it seems to refer to the ~75-300ghz range [0][1], including the W and D bands. While looking into this, I learned that terahertz frequencies are called THF or "tremendously high frequency"[2], which I thought was pretty funny. Pretty used to HF, VHF, UHF etc. but never heard of "THF" until now! [0] https://www.rfwireless-world.com/Terminology/Sub-THz-Bands-and-Frequencies.html https://www.rfwireless-world.com/Terminology/Sub-THz-Bands-a... [1] http://www.brave-beyond5g.com/index.php/sub-thz/ http://www.brave-beyond5g.com/index.php/sub-thz/ [2] https://books.google.ca/books?id=K9N1TVhf82YC&pg=PA7&redir_esc=y#v=onepage&q&f=false https://books.google.ca/books?id=K9N1TVhf82YC&pg=PA7&redir_e...

pythonguython 4y ago
Starting from VHF, the ITU names the bands in this order: very, ultra, super, extremely, and tremendously high. I once asked several of my friends who don’t know anything about radio to try to name the bands in ascending order after I scrambled them, and they all gave me different, incorrect answers.