3 ms·

Anyone got a resource that explains the relationship between spectrum/frequency/modulation-tech/etc and bandwidth in an understandable way for someone not-so-ph

by auganov 11y ago

Anyone got a resource that explains the relationship between spectrum/frequency/modulation-tech/etc and bandwidth in an understandable way for someone not-so-physics/signal-processing-literate? My [uninformed] intuition tells me that you can have theoretically infinite bandwidth over any spectrum or modulation scheme, but the cost/size/energy-requirement quickly gets prohibitively high because of the "sensitivity" such a device would have to have?

samcheng 11y ago
That's why they call it "bandwidth" - the width of the spectrum band is what determines the information throughput. Wikipedia might work as a primer. See Nyquist & Shannon: https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem#Sampling_of_non-baseband_signals https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampli... For example, in order to sample the FM radio signals in the frequency range of 100-102 MHz, it is not necessary to sample at 204 MHz (twice the upper frequency), but rather it is sufficient to sample at 4 MHz (twice the width of the frequency interval).
- typon 11y ago
  When I first learned this it blew my mind at it's implications and then obviousness. Shannon was a once-in-a-century genius...in a century of many once-in-a-century geniuses.
- ucaetano 11y ago
  Also take a look at spectrum efficiency, which is the "practical implementation" of all this. It really helps to understand how spectrum is a limited public resource. For example, a carrier with 20MHz of spectrum each way and a tower covering 1km2 in 3 sectors could offer at most 60Mbps down over 3G. If you have 6000 customers in that same area (remember that some cities have densities in the 10+k/km2), that means ~10Kbps per customer on average, which is enough for 1.5 GB/month/customer.

3 ms·

Anyone got a resource that explains the relationship between spectrum/frequency/modulation-tech/etc and bandwidth in an understandable way for someone not-so-ph

by auganov 11y ago

samcheng 11y ago
That's why they call it "bandwidth" - the width of the spectrum band is what determines the information throughput. Wikipedia might work as a primer. See Nyquist & Shannon: https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem#Sampling_of_non-baseband_signals https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampli... For example, in order to sample the FM radio signals in the frequency range of 100-102 MHz, it is not necessary to sample at 204 MHz (twice the upper frequency), but rather it is sufficient to sample at 4 MHz (twice the width of the frequency interval).
- typon 11y ago
  When I first learned this it blew my mind at it's implications and then obviousness. Shannon was a once-in-a-century genius...in a century of many once-in-a-century geniuses.
- ucaetano 11y ago
  Also take a look at spectrum efficiency, which is the "practical implementation" of all this. It really helps to understand how spectrum is a limited public resource. For example, a carrier with 20MHz of spectrum each way and a tower covering 1km2 in 3 sectors could offer at most 60Mbps down over 3G. If you have 6000 customers in that same area (remember that some cities have densities in the 10+k/km2), that means ~10Kbps per customer on average, which is enough for 1.5 GB/month/customer.