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The current flow diagram does the following:
- Generate a QPKS constellation from a random bit source. The
constellation is parametrized by the 'Constellation Rect. Object'
and the variables 'sps' (Samples Per Symbol) and 'excess_bw' (Excess
Bandwidth).
- Send the modulated signal through a AWGN channel. Noise channel taps
are controlled with the 'taps' variable, the other paramters are
given through the 'QT GUI Range' objects.
- Display the constellation diagram as well as the time and frequency
domain plots of the signal after the channel (receiver side).
- Synchronize the clock using a polyphase clock sync with root raised
cosine filters. The number of filters is stored in 'nfilts' and the
filter themselves are in 'rcc_taps'.
- Finally, display the constellation after the RCC filters.
What is still missing:
- Multipath fading taps in the channel model (for later)
- Equalization on the receiver side.
PROBLEM: The wiki tutorial targets GNU Radio 3.9, and uses 'Linear
Equlizer' and 'Adaptive Algorithm' blocks which are not
available in GNU Radio 3.8. We need to use 'CMA Equalizer'
and 'LMS DD Equalizer' and figure out their parameters
instead. Though this should not be hard.
- Phase and Fine Frequency Correction.
- Decode the message.
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