How to integrate Sionna RT with Sionna PHY

[abidur0177]

Hello,

I have generated a time-varying Channel Frequency Response (h(t,f)) using Sionna RT and saved it in .npy format. Now, I would like to use this CFR to simulate OFDM transmission with Sionna PHY.

Below are the parameters I am considering:

num_ofdm_symbols = 32
num_subcarriers = 76 (FFT points)
batch_size = 128
num_rx = 1 (4 Rx antennas)
num_tx = 1 (1 Tx antenna)

Shape of h(f,t) = (128, 1, 4, 1, 1, 14, 76)
(batch_size, num_rx, num_rx_ant, num_tx, num_tx_ant, num_ofdm_symbols, num_sc)

# Define the parameters
BATCH_SIZE = 128
h_dop = np.load("/home/tear/Desktop/sionna/sionna_rt/h_dop.npy")  # Load generated channel
apply_channel = sn.phy.channel.ApplyOFDMChannel()  # Instantiate object to apply channel

NUM_BITS_PER_SYMBOL = 2
CODERATE = 0.5

n = int(RESOURCE_GRID.num_data_symbols * NUM_BITS_PER_SYMBOL)
k = int(n * CODERATE)

# Instantiate all required objects

binary_source = sn.phy.mapping.BinarySource()
encoder = sn.phy.fec.ldpc.LDPC5GEncoder(k, n)
mapper = sn.phy.mapping.Mapper("qam", NUM_BITS_PER_SYMBOL)
rg_mapper = sn.phy.ofdm.ResourceGridMapper(RESOURCE_GRID)

# Use frequency-domain channel from generated data
h_freq = h_dop  

ls_est = sn.phy.ofdm.LSChannelEstimator(RESOURCE_GRID, interpolation_type="nn")
lmmse_equ = sn.phy.ofdm.LMMSEEqualizer(RESOURCE_GRID, STREAM_MANAGEMENT)
demapper = sn.phy.mapping.Demapper("app", "qam", NUM_BITS_PER_SYMBOL)

decoder = sn.phy.fec.ldpc.LDPC5GDecoder(encoder, hard_out=True)

# Generate input and run block-wise implementation

no = sn.phy.utils.ebnodb2no(
    ebno_db=10.0,
    num_bits_per_symbol=NUM_BITS_PER_SYMBOL,
    coderate=CODERATE,
    resource_grid=RESOURCE_GRID
)

# Transmitter
bits = binary_source([BATCH_SIZE, NUM_UT, RESOURCE_GRID.num_streams_per_tx, k])
codewords = encoder(bits)
x = mapper(codewords)
x_rg = rg_mapper(x)

# Channel Output
y = apply_channel(x_rg, h_freq, no)  # Apply channel to input signal

# Receiver
h_hat, err_var = ls_est(y, no)
x_hat, no_eff = lmmse_equ(y, h_hat, err_var, no)
llr = demapper(x_hat, no_eff)
bits_hat = decoder(llr)

Question: Is my implementation appropriate?

[faycalaa]

I cannot run your code since I don't have access to the dataset of channel impulse responses. However, from reading the code, it looks correct.

Note that you can also directly interface the ray tracer with the link-level simulation without using a pre-collected dataset. This approach might lead to slower simulations as the ray tracer would be executed on-the-fly. You can find an example in this tutorial.

[abidur0177]

Thanks a lot. It worked