3 ms·
Basically OFDM makes analogue engineering unnecessarily difficult when CMOS designs are still riding Moore's horse. Don't forget that the QAMs can go pretty hi
by anotherhue 3y ago
Basically OFDM makes analogue engineering unnecessarily difficult when CMOS designs are still riding Moore's horse.
Don't forget that the QAMs can go pretty high, 128/256 points iif the SNR is sensible.
I studied radio TDMA and it's still magical to me.
- oplaadpunt 3y agoWith QAM you're more thinking about the error vector magnitude (EVM), rather then the signal-to-noise ratio. From the EVM you get a bit error rate, which determines maximum sensible data speeds. How high QAM will go is also a strong function of what frequency band: at low frequency, I've seen 512-QAM and higher, while at >100GHz they're struggeling for 32-QAM
- madengr 3y ago[dead]
- zokier 3y ago> Don't forget that the QAMs can go pretty high, 128/256 points iif the SNR is sensible. Isn't 4096-QAM already pretty commonplace these days? For example DOCSIS is apparently pushing already 16k QAM: > DOCSIS 3.1 adds 16-QAM, 128-QAM, 512-QAM, 1024-QAM, 2048-QAM and 4096-QAM, with optional support of 8192-QAM/16384-QAM. https://en.wikipedia.org/wiki/DOCSIS https://en.wikipedia.org/wiki/DOCSIS
- voxadam 3y agoI'm almost certain that modern ADSL variants employ up to at least 32768-QAM.
- dfox 3y agoModern ADSL and VDSL version typically use DMT, which is more or less the same thing as OFDM. Interesting part of that in context of xDSL is that each of the subcarriers (typically QAM-64 modulated) can have different amount of actual payload data assigned to them depending on the loop quality and interference (many xDSL CPEs have spectrogram somewhere in their web interface which directly shows how the payload is distributed over the subcarriers).
- amelius 3y ago> The OFDM signal family is designed to be robust in the presence of strong multipath effects that result in a long delay spread.