channel gain and users location

[yacine074]

I would like to know if it is possible to get the channel gain between a pair of users, or users/BS and specify the users location in this tutorial sionna tutorial

[jhoydis]

Hi,

The location of users and base stations can be set with the function set_topolgy.
In cell 12 of the tutorial, the model updates the user positions each time it is called through the method new_topology.

In cell 8, the line

h_freq = cir_to_ofdm_channel(frequencies, a, tau, normalize=True)

transforms the channel impulse responses into the channel frequency responses which are used for the simulation of OFDM transmissions. This is visualised in cell 9.

You can also call the function cir_to_time_channel to obtain the discrete time-domain impulse responses. This process is nicely explained in cells 10-14 of this tutorial.

The 3GPP 38.901 models only define the channels between users and base stations, but not between users.

Also note that pathloss and shadow fading are disabled in the tutorial you mention. You could activate both by changing cell 4 to

channel_model = UMi(carrier_frequency=carrier_frequency,
                    o2i_model="low",
                    ut_array=ut_array,
                    bs_array=bs_array,
                    direction=direction,
                    enable_pathloss=True,
                    enable_shadow_fading=True)