Module wireless 

Wireless blocks: several antennas, fading channels, OFDM and MIMO detection.

Block	Does
mimo_tx	spreads the symbols over $n_{t}$ antennas: spatial multiplexing (one layer per antenna, power $1/n_{t}$ each) or Alamouti’s code
rayleigh	flat Rayleigh or Rician fading, $n_{r} \times n_{t}$, constant over the trial or over coherence blocks, with exponential antenna correlation
tdl	a tapped delay line (EPA, EVA, ETU, ITU Pedestrian A and Vehicular A, exponential) with Doppler
cdl	a clustered delay line of 3GPP TR 38.901 (CDL-A to CDL-E) between uniform linear arrays, with the Doppler of a moving receiver
ofdm_tx	maps every antenna’s symbols on a resource grid with pilots and modulates it
ofdm_rx	demodulates, estimates the channel (perfect, LS or LMMSE) and detects every resource element
mimo_rx	detects a single-carrier link over flat fading with the known channel

Scales

The OFDM modulator gives the samples the power $K/(L N)$ ($K$ active subcarriers, IFFT of size $L N$), so that a resource element of unit energy spreads over $L N / K$ samples: ofdm_tx sets the samples per symbol to $L N / K$ and the symbol rate to the rate of the resource elements $K \Delta f$. The noise blocks then set the SNR per resource element: awgn with snr_db gives $E_{s}/N_{0}$ on every data resource element of unit energy, and the noise of every demodulated resource element has the variance of the noise per sample. Spatial multiplexing divides the power among the antennas, so that the SNR is the total transmitted energy per resource element over the noise of one receive antenna.

Example

link:
  - {type: source, constellation: 16-QAM, n_symbols: 4800}
  - {type: mimo_tx, n_tx: 2}
  - {type: ofdm_tx, n_fft: 256, n_subcarriers: 200, n_cp: 18, n_symbols: 14}
  - {type: tdl, profile: EPA, doppler_hz: 5, n_rx: 2}
  - {type: awgn, snr_db: $snr_db}
  - {type: ofdm_rx, estimation: lmmse, detector: mmse}

References

1. S. M. Alamouti, “A simple transmit diversity technique for wireless communications,” IEEE J. Sel. Areas Commun., 16(8), 1451–1458, 1998.
2. O. Edfors, M. Sandell, J.-J. van de Beek, S. K. Wilson and P. O. Börjesson, “OFDM channel estimation by singular value decomposition,” IEEE Trans. Commun., 46(7), 931–939, 1998.
3. 3GPP TS 36.101, E-UTRA; User Equipment radio transmission and reception, Annex B.2 (EPA, EVA, ETU).

Structs

OfdmFrame

An OFDM frame: what the receiver needs to undo transmit.

Enums

Csi

The channel of a trial, as a genie-aided receiver knows it.