Parameter settings

main_code.mlx  (Setting simulation parameters)

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Parameter
Variable in code
Unit
Carrier frequency
param.freq_carr
Hz
Speed of light
param.c
meter/sec
Wavelength of carrier frequency
param.lambda
meter
Sampling rate
param.freq_band
Hz
Maximum number of reflections
param.num_reflct
-
Maximum number of diffractions
param.num_difrct
-
Scattering area
param.sctt_area
-
Scattering grid interval
param.sctt_grid
-
Diffusion lobe width
param.itg_lobe
-
Number of BSs
simulset.num_bs
-
Number of IRSs
simulset.num_irs
-
Number of UEs
simulset.num_ue
-
Number of VEHs
simulset.num_vehc
-
Grid map domain in x-axis
simulset.x_axis
-
Grid map domain in y-axis
simulset.y_range
meter
Number of grid points of UE positions
simulset.num_grid
-
Number of subcarriers
simulset.num_subcar
-
Number of cyclic prefixes
simulset.num_cycprf
-
Number of blocks
simulset.num_blck
-
Number of sample sets
simulset.tot_samp
-
Period of getting sample sets
simulset.period_samp
sec

BS: base station

IRS: intelligent reflecting surface

UE: user equipment

VEH: vehicle

Tx: transmitter

Rx: receiver

RT: ray tracing

PG: propagation graph

OFDM: orthogonal frequency division multiplexing

Adjusting the carrier frequency of the wireless channel is possible with param.freq_carr. The speed of light is a physical constant, and the wavelength is determined by the carrier frequency. The sampling rate of the wireless communication system is determined with param.freq_band, which defines the time difference between consecutive channel snapshots. The channel snapshot is the smallest unit of channel data in WiThRay.

The channel path between the transmitter and receiver can undergo multiple numbers of reflections and diffractions, but the developed RT algorithm only finds the channel paths under the defined numbers of reflections and diffractions. The permitted numbers of reflections and diffractions are param.num_reflct and param.num_difrct. The RT algorithm of WiThRay theoretically has no limit on the numbers of reflections and diffractions, but increasing param.num_reflct and param.num_difrct can significantly increase the simulation runtime.

WiThRay supports generating the scattering paths based on the modified PG method. To implement the scattering, the modified PG method casts the grid points around the reflecting and diffracting points. The scattering area is the area with the scattering grid points, which is determined by param.sctt_area. The interval of grid points is determined by param.sctt_area. The interval of grid points in the scattering area is param.sctt_grid. As param.sctt_grid decreases, the resolution of scattering evaluation is enhanced, but the simulation complexity increases. WiThRay adopts the directive scattering model for the reflecting evaluation, where the lobe width is determined by param.itg_lobe.

simulset.num_bs, simulset.num_irs, simulset.num_ue, and simulset.num_vehc determine the numbers of BSs/IRSs/UEs/VEHs imported from [data] map.xlsx. Please remember that, if simulset.num_bs=4, there should be four or more BSs data in [data] map.xlsx. It is the same for simulset.num_irs, simulset.num_ue, and simulest.num_vehc.

There are two types of UE position settings, i.e., (i) grid-type and (ii) trajectory-type. simulset.experiment is to choose the UE position setting; "grid" and "traj." More details of UE position settings are explained here. The grid-type UE positions are determined by simulset.x_range, simulset.y_range, and simulset.num_grid. The trajectory-type UE positions are determined by simulset.num_subcar, simulset.num_cycprf, simulset.num_blck, simulset.tot_samp, and simulset.period_samp.

scattering points.png