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>Higher bandwidth should also make connection more robust Nope. Higher bandwidth could mean two things: Larger channel size: larger channels have a higher noi

by ac29 3y ago

>Higher bandwidth should also make connection more robust Nope. Higher bandwidth could mean two things: Larger channel size: larger channels have a higher noise floor and are are therefore less robust Faster throughput: Faster throughput generally means larger channels (as above) or various techniques to get more bits/Hz (such as more complex modulation), both of which are less robust

pzo 3y ago
I was more thinking if there is some frame collision and have a lot of data to send then overall robustness latency should be reduced? Similar like in a bus even if they travel at the same speed if you miss your bus or bus is full you have to wait. On the other hand if the bus is bigger with more sits or bus scheduled more frequent it's less likely you will have to wait. Also if bus breaks there is another one not far away behind to pickup passengers from broken bus.
eximius 3y ago
I think I read this somewhere but I am struggling to recall where, so hopefully I didn't dream this: I believe the larger channels are much, much larger and include adaptive techniques to dynamically exclude noisy regions within channel. It can afford to entirely sacrifice bands in this way because the channels are much larger.
- ac29 3y ago
  Even in the absence of all anthropogenic RF noise, the noise floor on larger channels is higher. Specifically, I'm thinking of thermal noise: https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise
cycomanic 3y ago
What you're writing isn't really correct either, this partly stems from the difficulty of what we mean by "robust". To increase throughput (i.e. bitrate ) we can either increase the channel bandwidth or the SNR (and use that SNR for higher modulation formats). Increasing the channel bandwidth does increase the noise power (assuming matched filtering) but we typically also assume that the psd of the signal stays the same => signal power increases and SNR stays the same. If we mean by "robust" that the signal is not as susceptible to fluctuations of the noise, than increasing the bandwidth could help. Assuming we want the same bitrate, we could use the larger bandwidth to reduce the modulation format and thus the required SNR while keeping the bitrate the same. However a larger bandwidth typically also increases probabilities of impairments (interferers, filtering...) but this is typically still a win, because capacity throughput is linearly proportional to bandwidth but only logarithmically to SNR.

by ac29 3y ago

pzo 3y ago

I was more thinking if there is some frame collision and have a lot of data to send then overall robustness latency should be reduced? Similar like in a bus even if they travel at the same speed if you miss your bus or bus is full you have to wait. On the other hand if the bus is bigger with more sits or bus scheduled more frequent it's less likely you will have to wait. Also if bus breaks there is another one not far away behind to pickup passengers from broken bus.

eximius 3y ago

I think I read this somewhere but I am struggling to recall where, so hopefully I didn't dream this: I believe the larger channels are much, much larger and include adaptive techniques to dynamically exclude noisy regions within channel. It can afford to entirely sacrifice bands in this way because the channels are much larger.

ac29 3y ago
Even in the absence of all anthropogenic RF noise, the noise floor on larger channels is higher. Specifically, I'm thinking of thermal noise: https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise

cycomanic 3y ago

What you're writing isn't really correct either, this partly stems from the difficulty of what we mean by "robust". To increase throughput (i.e. bitrate ) we can either increase the channel bandwidth or the SNR (and use that SNR for higher modulation formats). Increasing the channel bandwidth does increase the noise power (assuming matched filtering) but we typically also assume that the psd of the signal stays the same => signal power increases and SNR stays the same. If we mean by "robust" that the signal is not as susceptible to fluctuations of the noise, than increasing the bandwidth could help. Assuming we want the same bitrate, we could use the larger bandwidth to reduce the modulation format and thus the required SNR while keeping the bitrate the same. However a larger bandwidth typically also increases probabilities of impairments (interferers, filtering...) but this is typically still a win, because capacity throughput is linearly proportional to bandwidth but only logarithmically to SNR.