Build OFDM from first principles. Start with the problem—high data rates in a multipath channel—and discover why modern broadband radios use many orthogonal subcarriers, the FFT/IFFT, a cyclic prefix, synchronization, pilots and equalization.
Course 05 does not begin by asking you to memorize an OFDM block diagram. It begins with an engineering problem: how do we move much more information through a wideband multipath channel without making the receiver unmanageable?
Increase symbol rate and discover why short symbols become increasingly vulnerable to delayed copies of the signal.
See how echoes spread energy across time and create intersymbol interference in a high-rate single-carrier link.
Split one fast stream across many slower, orthogonal subcarriers and discover the core idea behind OFDM.
IFFT, FFT, cyclic prefix, synchronization, pilots and equalization are introduced only when the radio encounters the problem each block solves.
Courses 01–04, or equivalent comfort with I/Q, digital modulation, synchronization, framing and signal analysis.
Follow the engineering chain rather than memorizing the finished architecture.
Each stage introduces the next piece of OFDM because the radio needs it.
Push a digital link toward higher rates. Connect shorter symbol periods, multipath delay spread and intersymbol interference.
Divide the data among many slower subcarriers so each stream uses a longer symbol period while the aggregate data rate remains high.
Develop orthogonality visually and experimentally. See why carefully spaced subcarriers can overlap in spectrum yet remain separable at the receiver.
Use the IFFT to synthesize an OFDM symbol from QPSK/QAM subcarrier values and the FFT to recover those subcarriers at the receiver.
Introduce the cyclic prefix as a solution to delayed copies spilling into the useful OFDM symbol and connect it to simple frequency-domain equalization.
Use a known preamble for timing and frequency synchronization. Explore CFO and see why synchronization matters before the FFT can do its job.
Use pilots and known information to estimate channel effects, equalize the subcarriers and restore recognizable constellation points.
Map bits to symbols, place data and pilots on subcarriers, IFFT, add CP, transmit, synchronize, FFT, estimate/equalize and recover the message.
Interactive experiments and GNU Radio labs connect the mathematics to waveforms you can see, break and repair.
Increase data rate, add multipath and observe when delayed symbols begin interfering with one another.
Experiment with subcarrier spacing and discover what orthogonality looks like in time and frequency.
Place QPSK values into frequency bins, run the IFFT and connect the resulting time waveform back to its subcarriers.
Compare the same OFDM link with and without a CP in a multipath channel.
Add timing error and CFO. Watch the constellation fail, then use the preamble to bring the receiver back into alignment.
Use pilots to expose subcarrier-dependent channel distortion and correct it before symbol decisions.
Add AWGN, CFO and dynamic channel effects and connect each impairment to what you see in the spectrum and constellation.
Build an end-to-end OFDM transmitter and receiver with SDR hardware and exchange a message over the air with another station.
You've completed the five-course radio-engineering journey. Now the recipe disappears. Apply the toolbox from Courses 01–05 to unfamiliar signals and prove that you can capture, characterize and recover the information.
Course 05 turns the concepts from the first four courses into a complete broadband OFDM radio.
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