Path Loss Model in RIS scenario

Vienna 5G Link Level Simulator
1

Hi sir,
I actived scStr.topology.geometricLayout =true
and use pathloss model type =urban
what effect does these prameters when choose urban scStr.simulation.pathLossModel.alpha = 1;
scStr.simulation.pathLossModel.alpha2 = 3.9;
scStr.simulation.pathLossModel.breakDistance = 50;
scStr.simulation.pathLossModel.averageBuildingHeight = 1
when i choose position for RIS [x,y,z] ex: [200,100,20]
does z=20 for BuildingHeight because ris on height 20m
best regards
Roaa

2

Dear Roaa,

It means that the building’s height is 1 meter, and the RIS is at 20 meters, and therefore the RIS is 19 meters above the rooftop.

To see how this is calulcated, open the file +Parameters/SimulationParameters.m and scroll down to line 2457. There you find how these values are used, and what 3GPP document / section the calculation follows.

Best regards,
Bashar

3

Thanks for response, i want to question about alpha when chose pathloss exponent for urban from 2.7 to 3.5 ,the throughput becomes =zero why ??

4

With the higher exponent the path loss becomes higher, and therefore the recevied signal becomes too weak to be detected. In this case, higher transmit powers should be used, or you should lower the modulation order and code rate used.

5

Dear Bashar
In the RIS scenario, you chose two cells, the first cell without RIS and the second with RIS. I determined the location of the RIS for the second cell and the height of the building. For the first cell, I did not put a RIS, How does the height of the building affect it? Is the location of the RIS always specified above the building?
Best regards,
Roaa

6

Dear Roaa,

Please keep in mind that these models are not designed for RIS. They assume a BS to UE setup. With the “urban” model, the height parameter only the affects the transmitter height, which would be the BS for the link from the BS to RIS, and so the RIS is seen as a UE here. For the link from the RIS to the UE, the RIS is the transmitter and therefore the height parameter is applied to it.

These path loss models are abstract models that are designed for the a BS to UE setup. Therefore, interpreting their meaning in the context of BS-RIS-UE links is not a good idea. You should either think of the equivalent meaning of these parameters in the context of a RIS scenario, or you should look for a new path loss model that includes the RIS in it, and then you can add it as a new model in the simulator yourself.

Check the function setGeometricParameters() in the +Parameters/SimulationParameters.m file, for how these models are applied.

Best regards,
Bashar

7

Hello sir,
thank you for this information, i would to know ,how can i know building location when use urban model
Best regards,
Roaa

8

You can only specify the location of the BS, UE, and RIS. These you can choose in the scenario file under, for example,

scStr.topology.nodesPosition{1}	= [257,274,10];

which means that node 1 lies at the [x,y,z] position of [257,274,10] in meters. There are no “buliding” position to be defined in these models. The path loss models are derived statistically based on measurement campaigns and are fitted based on certain controlling paramemters, such as the heights of the BS and UE, frequency range, average building height, etc.

Please have a look at 3GPP documents to get a better understadning of how these models are defined. For example, Section 7.4 of https://www.etsi.org/deliver/etsi_tr/138900_138999/138901/16.01.00_60/tr_138901v160100p.pdf

Best,
Bashar