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= WARPLab 7 Example: SISO OFDM =
File: [source:/ResearchApps/PHY/WARPLAB/WARPLab7/M_Code_Examples/wl_example_siso_ofdm_txrx.m wl_example_siso_ofdm_txrx.m] 

This WARPLab example implements a SISO OFDM transmitter and receiver. 

== Transmitter ==
[[Image(wl_ofdm_blkDiag_Tx.png, nolink)]]

The OFDM transmitter code implements the following functions:
 * Random data generation
 * Modulation of random data to complex constellation symbols
 * Mapping of symbols to data-bearing subcarriers
 * Insertion of pilot tones in pilot subcarriers
 * Inverse fast Fourier transform (IFFT)
 * Cyclic prefix insertion
 * Preamble construction and insertion
 * Interpolation by 2x


== Receiver ==
[[Image(wl_ofdm_blkDiag_Rx.png, nolink)]]

The OFDM receiver code implements the following functions:
 * LTS correlation for synchronization
 * CFO estimation and correcting use time-domain estimation from LTS
 * Cyclic prefix removal
 * Fast Fourier transform (FFT)
 * Channel estimation from frequency-domain LTS
 * Residual phase error estimation from frequency-domain pilot tones
 * Equalization of data-bearing subcarriers using channel estimates and phase error estimates
 * Demodulation of complex symbols to data values

== Running the Example ==
The WARPLab OFDM example can be used in simulation only mode and in hardware-in-the-loop mode.

=== Simulation ===
To use the example in simulation mode set the top-level param {{{USE_WARPLAB_TXRX = 0;}}}, then run the m-script. When the script finishes 6 plots will show:

||  [[Image(wl_ofdm_plots_sim_txIQ.png,nolink)]][[BR]]Transmitted waveform  ||  [[Image(wl_ofdm_plots_sim_rxIQ.png,nolink)]] [[BR]]Received waveform  ||  [[Image(wl_ofdm_plots_sim_ltsCorr.png,nolink)]] [[BR]]Preamble correlation results (peaks indicate locations of preamble LTS)  ||
||  [[Image(wl_ofdm_plots_sim_chanEst.png,nolink)]] [[BR]]Channel estimate per subcarrier (I/Q components and complex magnitude)  ||  [[Image(wl_ofdm_plots_sim_phaseError.png,nolink)]] [[BR]]Phase error per OFDM symbol based on pilot tones  ||  [[Image(wl_ofdm_plots_sim_constellations.png,nolink)]] [[BR]]Tx and Rx constellations  ||

== Limitations ==
This example is intended as a staring point for researchers wishing to use WARPLab to prototype a wireless communications link. This examples does not implement some some blocks common in deployed OFDM systems, such as scrambling, interleaving and error correcting coding. For an example of a real-time OFDM implementation that implements all of these subsystems, please see the PHY in the [wiki:802.11 802.11 Reference Design].