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In this experiment an OFDM data transmission via a frequency-selective channel is established. Check the tutorial.
Initially a pilot sequence $d(i)$ is sent for channel estimation and equalizer initialization.
The equalizer coefficients are the reciprocal of $w(i)$ .
Now a data sequence is sent. Continue the simulation (6 steps). Step through the transmit chain:
$d(i)$ | A block containing 8 data symbols (representing 16 bits) is generated and serial-to-parallel converted. |
$u(i)$ | It IFFT-transforms to an OFDM symbol. |
$s(i)$ | The guard interval (GI) is added, i.e. the OFDM symbol is extended by a cyclic prefix containing the last single symbols. |
$r(i)$ | The received symbol is degenerated by the channel. |
$v(i)$ | The OFDM symbol is obtained by removing the guard interval, i.e. the first two single symbols. |
$w(i)$ | (After further 8 steps.) It FFT-transforms to the spectral representation of the OFDM symbol. |
${d}^{\prime}(i)$ | The equalized signal represents the 8 data symbols. |
Note that in this case no noise is present.
The app recurrently transmits a fixed data sequence.
Repeat the same flow as outlined above. Note that after clicking on OK the simulation restarts and the pilot sequence is sent via this channel. Therefore the channel estimation and equalizer initialization work properly.
Approve that ISI free detection requires a channel maximum delay spread (Echo delay) lower than the guard interval length (i.e. the adjustable discrete Prefix length times the sampling time of e.g. 1,6
$\mu s$
).