## Ongoing Projects

Mar. 2017 ~ Feb. 2019

Beamforming Techniques for 5G Millimeter-Wave Wireless Communication Systems

We are developing new millimeter-wave beamforming

technologies for 5G communication Systems.

Jan. 2017 ~ Dec. 2021

Development of Integer-Forcing MIMO Transceivers for 5G & Beyond Mobile Communication Systems

We are developing new MIMO communication technologies

for 5G and beyond cellular communication systems.

Working with Prof. Yang (POSTECH), Prof. Cho (POSTECH), and Prof. Lee (POSTECH)

Aug. 2017 ~ Jul. 2018

Samsung Electronics - Massive MIMO Topics

We are developing new MIMO communication technologies

for 5G and beyond cellular communication Systems.

## Parameter settings

main_code.mlx (Setting simulation parameters)

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.