OFDMA (not OFDM) is used as an access mode in LTE in combination with
TDM. I'm toying with the idea for a while now, but with 5-6 hours a
week available I haven't made much progress lately. Regarding 4FSK,
personally I see no advantage over 2FSK. It's certainly more
complicated to get working.
It is always useful I think in every conversation about 2 and 4 fsk to
qualify the implementation...
IE optimal 4 receiver 4fsk versus 4fsk in a wide non liear demod
passband etc etc
IMO, the implementation method it really needs to be rammed home when
forming comparisons .
particular the
Thanks Ross - that's a great explanation. Yes 4FSK is the "sweet spot"
in the FSK family for bandwidth efficiency. Here is a really good PDF
that I find myself referring too all the time:
http://www.atlantarf.com/FSK_Modulation.php
I have been working with non-coherent FSK modems (phase
actually LTE doesnt quite work that way
LTE used OFDM on uplink and downlink.
The entire operator's LTE spectrum is divided up into 15kHz subchannels
which are generated/decoded in the usual OFDM FFT manner.
User payload is transmitted using 'resource blocks' (RB), which I think
are 12
For a 16kHz wide or 10kHz wide IF filter with non linear demodulation, I
consider 2FSK the mode to choice where the bitrate can be satisfied .
4FSK takes a big hit in this implementation case, for reasons outlined
in many places and many times here and elsewhere. (DMR/P25 chaose 4FSK
to
