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> Dave knows to stay off the channel (otherwise he will cause interference) What would be the Bob-Alice-Dave equivalent to replacing the network hub with a swi

> Dave knows to stay off the channel (otherwise he will cause interference) What would be the Bob-Alice-Dave equivalent to replacing the network hub with a switch?

sarchertech 5y ago
If you wanted to add a learning switch to the example, you'd also need to add the concept of multiple channels. Once a switch learns which channel the recipient is on, it would only send to that channel instead of broadcasting to everyone. It still starts to break down unless you torture the analogy a bit more.
dragontamer 5y ago
Asking the FCC for dedicated channels and preventing everyone else in the world from using those channels. So I guess cellphones instead of one-at-a-time walkie talkies, since everyone on the cellphone network has a unique connection.
nvahalik 5y ago
There is no true radio analogue here in the sense of how OP was explaining it. At least in a wireless context, CDMA and TDMA are flawed examples because, CDMA uses fancy math to split communications over multiple channels and TDMA cuts the channels up into timeslots. You don't get full bandwidth allotment and utilization. To make a wireless switch, you'd need to have PTP optical/microwave/radio links which have highly directional antennas. This would give you full-bandwidth per user.
- vitus 5y ago
  Even in a wired context, frame-based protocols inherently utilize TDMA (over multiple channels), just not on timescales you normally think about. If I'm not mistaken, the radio example uses both frequency division and time division. You're on a particular channel (typically frequency, although AM exists too), and only one person can talk at a given instant, or else you get a collision which results in probably garbled output. (There's also space division at play, since radios are not infinitely powerful.) If the relay hop is also done over radio, then it's most likely achieved by hopping to dedicated frequencies for backbone comms, ideally with a separate antenna per channel so we can listen on all of them simultaneously. (You could constantly sweep the frequency space, but it's simpler to just have multiple antennas / radios.) A (modern) real-world example is that I can use my phone as a wifi hotspot. It relays packets to/from its upstream link (4G or even wifi again). (It also presumably behaves like a NAT, but that's an implementation detail.)

> Dave knows to stay off the channel (otherwise he will cause interference) What would be the Bob-Alice-Dave equivalent to replacing the network hub with a switch?

sarchertech 5y ago

If you wanted to add a learning switch to the example, you'd also need to add the concept of multiple channels. Once a switch learns which channel the recipient is on, it would only send to that channel instead of broadcasting to everyone. It still starts to break down unless you torture the analogy a bit more.

dragontamer 5y ago

Asking the FCC for dedicated channels and preventing everyone else in the world from using those channels. So I guess cellphones instead of one-at-a-time walkie talkies, since everyone on the cellphone network has a unique connection.

nvahalik 5y ago

There is no true radio analogue here in the sense of how OP was explaining it. At least in a wireless context, CDMA and TDMA are flawed examples because, CDMA uses fancy math to split communications over multiple channels and TDMA cuts the channels up into timeslots. You don't get full bandwidth allotment and utilization. To make a wireless switch, you'd need to have PTP optical/microwave/radio links which have highly directional antennas. This would give you full-bandwidth per user.

vitus 5y ago
Even in a wired context, frame-based protocols inherently utilize TDMA (over multiple channels), just not on timescales you normally think about. If I'm not mistaken, the radio example uses both frequency division and time division. You're on a particular channel (typically frequency, although AM exists too), and only one person can talk at a given instant, or else you get a collision which results in probably garbled output. (There's also space division at play, since radios are not infinitely powerful.) If the relay hop is also done over radio, then it's most likely achieved by hopping to dedicated frequencies for backbone comms, ideally with a separate antenna per channel so we can listen on all of them simultaneously. (You could constantly sweep the frequency space, but it's simpler to just have multiple antennas / radios.) A (modern) real-world example is that I can use my phone as a wifi hotspot. It relays packets to/from its upstream link (4G or even wifi again). (It also presumably behaves like a NAT, but that's an implementation detail.)