How to generate FDD uplink and downlink channel responses that can have the partial reciprocity

[david-xc]

I tried to generate UMi channel for both uplink and downlink in a FDD system. My question is how to set the channel configration so that the uplink and downlink channel has partial reciprocity.

Here is the code I used to generate the channel but it seems the cosine similarity between uplink and downlink channel is quite low. So I wander if I missed something in the configuration.

###################################
channel_model_ul = UMi(carrier_frequency = 3.5e9,
                    o2i_model = 'low',
                    ut_array = ut_array,
                    bs_array = bs_array,
                    direction = 'uplink')

channel_model_dl = UMi(carrier_frequency = 3.6e9,
                    o2i_model = 'low',
                    ut_array = ut_array,
                    bs_array = bs_array,
                    direction = 'downlink')

topology = gen_topology(batch_size, num_ut, scenario)

channel_model_ul.set_topology(*topology)
channel_model_dl.set_topology(*topology)
UL_channel=OFDMChannel(
                               channel_model_ul,
                                pusch_transmitter.resource_grid,
                                normalize_channel=True,
                                return_channel=True)
DL_channel=OFDMChannel(
                               channel_model_dl,
                                pusch_transmitter.resource_grid,
                                normalize_channel=True,
                                return_channel=True)
x, b = pusch_transmitter(batch_size)

y_ul,h_ul=UL_channel([x,no])
y_dl,h_dl=DL_channel([x,no])
##################################################

Thank you!

[jhoydis]

Hi @david-xc,

As far as I know, the 3GPP channel models do not have any form of channel reciprocity. If you want such a feature, you should rely on ray tracing on different frequencies.