# Comparative Study of Indoor Propagation Model Below and Above 6 GHz for 5G Wireless Networks
## 6 Results and Discussion
### Path Loss Results and Analysis  
Figure 4 shows the CI and FI scatter plots and path loss models at 3.5 GHz and 28 GHz for the LOS scenario. Generally, it can be shown that the path loss increases as the distance is increased for both frequencies measured. Using CI models, the path loss exponent (PLE) values are \(n\)= 1.6 and \(n\)= 1.3 for 3.5 GHz and 28 GHz, respectively. It is noted that both PLEs are less than the free space path loss exponent \(n=2\) even though the environment is LOS. This implies that the test bed of measurement (indoor corridor) acts as a waveguide; the many reflected signals reach the receiver from both walls on either side, floor and ceiling are added up constructively. From this study as well as many previous  
Figure 3: Floor Plan for Measurement Environment. studies in an indoor environment, it is noted that the PLE is not frequency dependent but is strongly environment dependent [30; 35]. The standard deviation values of the CI path loss models are 3.2 dB and 1.3 dB for 3.5 GHz and 28 GHz, respectively. The 3 GPP WINNER II model (FI) was also used to investigate the measured data. Figure 4 shows that the FI model also fits the measured data very well at both frequencies. The slope is 1.5 for both bands, which is comparable to the PLE for the CI model. Moreover, the values of the floating intercept (\(\alpha_{FI}\)) indicate the validity of this model in bands below and above 6 GHz. The \(\alpha_{FI}\) values are 44.9 dB and 62.3 dB for 3.5 GHz and 28 GHz, respectively. These values are slightly different by 1 dB as compared to the free space path loss at reference point of CI model (\(d_{0}\) = 1 m). The standard deviation values for the FI model are 3.0 dB and 1.0 dB for 3.5 GHz and 28 GHz, respectively. The scatter plots of path loss, CI and FI path loss models for the NLOS scenario are shown in Figure 5. From the CI model, it can be shown that the PLE is more than the FSPL exponent for both bands. The PLE values are 2.7 and 3.6 for 3.5 GHz and 28 GHz, respectively. This implies that the signal power drops at a rate of 7 dB/decade and 16 dB/decade more than the signal power drop in the FSPL model (20 dB/decade). For the FI model, the slope (\(\beta_{FI}\)) values are 2.1 and 3; and the \(\alpha_{FI}\) values are 48.9 dB and 72.2 dB for 3.5 GHz and 28 GHz, respectively. It is shown from the observed parameters for both the CI and FI models that the signal degradation with Tx-Rx separation distance is more in the 28 GHz band. The \(\alpha_{FI}\) values for the FI model deviate from the FSPL at 1 m by 5.6 dB and 10.8 dB for 3.5 GHz and 28 GHz, respectively. Since this model is not physically based, while the CI is physically based, the more accurate parameter for signal drop is the PLE (\(n\)). For multi frequencies, the ABG and CIF path loss models are used to investigate the channel propagation at two different bands; one below 6 GHz (3.5 GHz) and the other is above 6 GHz (28 GHz). The ABG multi-frequency path loss model for the LOS scenario is shown in Figure 6. The distance dependent factor (\(\alpha_{ABG}\)) is 1.5 and the frequency dependent factor is (\(\gamma\) = 2.1). The optimization factor (\(\alpha_{ABG}\)) is 33.2 dB. The physical-based multi-frequency path loss model (CIF) is shown in Figure 7. With the fixed reference frequency \(f_{0}\) of 10.5 GHz, the PLE (\(n_{CIF}\)) frequency is 1.5 with the slope of linear frequency dependency (b = \(-\)0.2). The observed parameters of this model indicate that this model is accurate and simple and is physically-based. For LOS scenario, it can be shown that the both \(\alpha_{ABG}\) and \(n_{CIF}\) are identical for the ABG and CIF path loss models. This implies that in these measurements the ABG model has good performance for path loss in LOS scenario, although it is not a physically-based model. Figure 4: Path loss CI and FI models fitting versus Tx-Rx separation distance at 3.5 GHz and 28 GHz for LOS scenario. Figure 8 shows the ABG path loss model for the NLOS scenario.