# Investigations on Millimeter-Wave Indoor Channel Simulations for 5G Networks
## 2 Previous Related Work  
Channel modeling for 5G indoor networks has been an exciting topic. In [16], measurements were conducted in university campaigns at 28 GHz and 73 GHz to estimate path loss exponents in line-of-sight LOS and non-LOS scenarios. The authors [17] conducted measurements in two buildings and compared indoor path-loss models at 38 GHz; they proposed an enhanced model based on ITU recommendations for indoor propagation. WINNER project [18] presents channel models based on channel measurements performed at 1-6 GHz; the model was later extended to cover LOS and NLOS propagation scenarios at 61-65 GHz [19]. In [16], the authors investigated the behavior of delay spread, path loss, and received signal strength at mmWave frequencies for multi-floor environments using ray-tracing software; a similar study was reported by [17]. The usage of ray-tracing software for mmWave frequencies is highly dependent on the software input parameters and accuracy of environment design; in [20], the authors investigated the effect of using different values of electrical constitutive parameters (permittivity and conductivity) on ray-tracing results. It was found that choosing the accurate values of permittivity and conductivity is vital for obtaining accurate results. In [21], authors studied the millimeter frequency band (26, 28, 32, and 38 GHz) propagation properties in indoor multi-floor stairwell situations; the estimated PLE value was around 7. A similar study was performed at 26 GHz and 38 GHz in corridors and stairwell scenarios; it was found that directional PLE in corridors was less than 2 and 4 for LOS and NLOS, respectively, for both types of linear polarizations (V-V and V-H). At the same time, omnidirectional PLE is lower, especially for V-H polarization cases; in stairwells, the omnidirectional PLE values are slightly bigger than those recorded in corridors. In contrast, the directional PLE values are remarkably bigger than the recorded values in corridors. In [22], experiments were conducted in a typical indoor office environment at New York University. The study investigated large-scale path loss and temporal statistics at 28 GHz and 73 GHz. The PLEs for LOS scenarios were 1.1-4.1 and 1.3-4.7 at 28 GHz and 73 GHz, while, for NLOS scenarios, PLEs were 2.7-5.1 and 3.2-6.4 at 28 GHz and 73 GHz, respectively. In [23], a wideband double-directional channel sounding campaign at 28 GHzis presented and the investigated environments include an indoor open hall. For LOS and NLOS scenarios, PLE were around 1.9 and 2.8, respectively. PLE and RMS delay spread were examined at 28 GHz within an indoor environment [24]; for LOS scenarios, the PLE and RMS-DS were 1.5 and 5-20 ns, respectively, while, for NLOS scenarios, the PLE and RMS-DS were 2.2 and 10-40 ns, respectively. A set of wideband directional propagation measurements was conducted at 39 GHz in an indoor hall environment, where the PLE at LOS was around 1.8 [25]. Authors of [26] conducted measurements within an indoor environment at 60 GHz with different antenna heights; in their study, they found that scatter paths contribute more to signal strength than direct paths and that human movements can cause obstructions around 18-36 dB. The PLE for LOS scenarios were in the range of 0.6-1.2, while, for NLOS scenarios, the PLE were in the range of 2.7-5.4. Authors in [27] examined PLE and RMS-DS in LOS, obstructed LOS, and NLOS scenarios at 30 GHz and 60 GHz within indoor environments; for 30 GHz, the recorded PLE values for LOS, OLOS, and NLOS were 1.7, 1.8, and 2.3, while, for RMS-DS, the recorded values for LOS, OLOS, and NLOS were 6.7 ns, 27.1 ns, and 28.3 ns, respectively. For 60 GHz, the recorded PLE values for LOS, OLOS, and NLOS were 1.2, 3.7, and 5.7, while, for RMS-DS, the recorded values for LOS, OLOS, and NLOS were 3.4 ns, 23.5 ns, and 22.5 ns, respectively. RMS-DS tends to be smaller for higher frequency, while PLE tends to be larger.