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The text transcript could be improved: > The fourth Generation of wireless networks, four G for short, is now being extended to five G, and six G is in plannin

by nayuki 4y ago

The text transcript could be improved: > The fourth Generation of wireless networks, four G for short, is now being extended to five G, and six G is in planning. Spelling out "four G" does not improve clarity. The sentence should be: The fourth generation of wireless networks, 4G for short, is now being extended to 5G, and 6G is in planning. > GigaHertz ... Giga Hertz Must be written as gigahertz. > four hundred Mega Hertz Should be written as 400 MHz; using number words doesn't improve clarity. Also, the factual content could be improved in a few places: > If you want to transfer more information through a channel with a fixed noise-level, you have to increase either the bandwidth or the power. There's also beamforming and MIMO. > If you took all the water in the atmosphere and put it on the ground you’d get about 2.5 cm. The clouds alone merely make a tenth of a millimeter. To make the comparison easier, it should be written as 25.0 mm and 0.1 mm. Ironically, she linked to an original video that indeed uses millimetres. > The European Commission has agreed on –42 decibel watts for 5G base stations. The FCC in the US set a limit at –20 decibel watt. This is a logarithmic scale, so this is more than 30 orders of magnitude above the limit the meteorologists ask for. No, it's 3 orders of magnitude, or 1000×.

johnklos 4y ago
I suppose it's a sign of how good her articles and videos are that the only stuff you can find that're wrong are details. In the spirit of being pedantic (don't take too seriously): "There's also beamforming and MIMO" No. Beamforming attempts to increase apparent power by changing parameters. One could just as easily say "moving sender and recipient closer". MIMO is also manipulation of sending and receiving antennae, and therefore irrelevant to the discussion about transmitting through a channel with a fixed noise level. She did make a mistake about the number of orders of magnitude, though.
- ec109685 4y ago
  Why isn’t beamforming a way of increasing effective bandwidth?
  - johnklos 4y ago
    It is! But she's talking about "a channel with a fixed noise level". Making new antennae, changing current antennae, moving them closer, aiming them differently, replacing them with an ethernet cable are all ways of increasing effective bandwidth, but those are outside of what she's talking about.
    - cycomanic 4y ago
      The receiver is part of the channel. So if you do beamforming your power at the receiver is higher, i.e. your SNR is higher. Any other interpretation does not make sense, because it's completely irrelevant to the discussion.
      - johnklos 4y ago
        Sigh. The receiver is part of the channel. Exactly. Changing the parameters of the channel means you're no longer commenting on her statement - you're now making a new discussion. Her statement wasn't wrong, technically or otherwise, just because you can think of ways to increase information by changing parameters of the channel. I can think of ways to increase information, but absolutely none of them, suggested by you or by me, can change or invalidate her statement: "If you want to transfer more information through a channel with a fixed noise-level" Here, since this seems tough for you: "If you want to execute instructions more quickly in a CPU, you can increase the clock speed." You're saying, "but if you put in a new CPU that has higher IPC"...
- cycomanic 4y ago
  > "There's also beamforming and MIMO" No. Beamforming attempts to increase apparent power by changing parameters. One could just as easily say "moving sender and recipient closer". MIMO is also manipulation of sending and receiving antennae, and therefore irrelevant to the discussion about transmitting through a channel with a fixed noise level. Yes beamforming changes the SNR at the receiver, by shaping the beam to be more "concentrated", i.e. focusing onto the receiver. It is highly relevant because yes by increasing the SNR at your receiver you do increase the throughput (albeit only logarithmically). MIMO is very relevant to the discussion, because instead of increasing bandwidth you increase dimensionality of your channel, which has the same effect (i.e. you increase the term in front of the log in Shannon's formula). I don't know why this should be irrelevant for a channel with fixed noise level (also it's probably more correct to say fixed SNR).
Georgelemental 4y ago
I think the transcription issues are likely artifacts from computer transcription software

by nayuki 4y ago

johnklos 4y ago

I suppose it's a sign of how good her articles and videos are that the only stuff you can find that're wrong are details. In the spirit of being pedantic (don't take too seriously): "There's also beamforming and MIMO" No. Beamforming attempts to increase apparent power by changing parameters. One could just as easily say "moving sender and recipient closer". MIMO is also manipulation of sending and receiving antennae, and therefore irrelevant to the discussion about transmitting through a channel with a fixed noise level. She did make a mistake about the number of orders of magnitude, though.

ec109685 4y ago
Why isn’t beamforming a way of increasing effective bandwidth?
- johnklos 4y ago
  It is! But she's talking about "a channel with a fixed noise level". Making new antennae, changing current antennae, moving them closer, aiming them differently, replacing them with an ethernet cable are all ways of increasing effective bandwidth, but those are outside of what she's talking about.
  - cycomanic 4y ago
    The receiver is part of the channel. So if you do beamforming your power at the receiver is higher, i.e. your SNR is higher. Any other interpretation does not make sense, because it's completely irrelevant to the discussion.
    - johnklos 4y ago
      Sigh. The receiver is part of the channel. Exactly. Changing the parameters of the channel means you're no longer commenting on her statement - you're now making a new discussion. Her statement wasn't wrong, technically or otherwise, just because you can think of ways to increase information by changing parameters of the channel. I can think of ways to increase information, but absolutely none of them, suggested by you or by me, can change or invalidate her statement: "If you want to transfer more information through a channel with a fixed noise-level" Here, since this seems tough for you: "If you want to execute instructions more quickly in a CPU, you can increase the clock speed." You're saying, "but if you put in a new CPU that has higher IPC"...
cycomanic 4y ago
> "There's also beamforming and MIMO" No. Beamforming attempts to increase apparent power by changing parameters. One could just as easily say "moving sender and recipient closer". MIMO is also manipulation of sending and receiving antennae, and therefore irrelevant to the discussion about transmitting through a channel with a fixed noise level. Yes beamforming changes the SNR at the receiver, by shaping the beam to be more "concentrated", i.e. focusing onto the receiver. It is highly relevant because yes by increasing the SNR at your receiver you do increase the throughput (albeit only logarithmically). MIMO is very relevant to the discussion, because instead of increasing bandwidth you increase dimensionality of your channel, which has the same effect (i.e. you increase the term in front of the log in Shannon's formula). I don't know why this should be irrelevant for a channel with fixed noise level (also it's probably more correct to say fixed SNR).

Georgelemental 4y ago

I think the transcription issues are likely artifacts from computer transcription software