Sionna for Basic Channel Estimation

[kmlfrkbsrn]

How to use Sionna for Basic Channel Estimation? I have already checked OFDM channel model. I'm trying use in 4X4 MIMO LDPC channel, but I couldn't do this. Is it possible?

[SebastianCa]

Hi @kmlfrkbsrn,
please have a look at the OFDM MIMO detection tutorial. This should explain the basics of channel estimation in Sionna.

[kmlfrkbsrn]

Hi @SebastianCa ,
Thnx for reply. I have already check this page. But I couldn't adapt this to basic comm. channel.

[SebastianCa]

I think there is something conceptually wrong with your code. For channel estimation you typically rely on known pilots (i.e., they are part of the transmitted signal x at known positions). See LS estimator for a detailed explanation. In your case, you send random payload bits - and, thus, random symbols- but you define the value of the pilots only at the receiver.

A simple sanity check of your code is to assume that the receiver knows a fraction of the transmitted symbols and use these know symbols for channel estimation.

[kmlfrkbsrn]

pilot_symbols = tf.constant([[1.0 + 1j, 1.0 - 1j, 1.0 + 1j, 1.0 - 1j]], dtype=tf.complex64) # 1x4 pilot symbols

In here I gave the pilot symbol for testing channel. I know the output bits. I have curiosity about Is channel estimation technics available in Sionna only for OFDM channel?

[kmlfrkbsrn]

In addition, Are there any way to use below code for other channels estimations? Such as LDPC or AWGN channel.

sionna.mimo.lmmse_equalizer(y, h, s, whiten_interference=True)

[SebastianCa]

pilot_symbols = tf.constant([[1.0 + 1j, 1.0 - 1j, 1.0 + 1j, 1.0 - 1j]], dtype=tf.complex64) # 1x4 pilot symbols

In here I gave the pilot symbol for testing channel. I know the output bits. I have curiosity about Is channel estimation technics available in Sionna only for OFDM channel?

The idea of channel estimation is to compare the received signal y against the known transmitted pilots x_p. Assuming y=h*x_p+n where n is some additional noise term, the channel estimator can then estimate h. See LS estimator for a more detailed explanation.

In the code above, you define the pilots only at the receiver. However, the transmitter sends random payload bits (and thus, random QAM symbols). Thus, there is a mismatch between the pilots you provide to the channel estimator and the actual transmitted symbols. Without these anchor points, the used channel estimator does not work.

[SebastianCa]

In addition, Are there any way to use below code for other channels estimations? Such as LDPC or AWGN channel.

sionna.mimo.lmmse_equalizer(y, h, s, whiten_interference=True)

This is for MIMO channels where the system has multiple transmit/receive antennas. Please see OFDM MIMO channel estimation tutorial for further details.

Note that for an AWGN channel no equalizer is required as the channel only adds Gaussian noise.