## 3 Results
### Auditorium  
Figure 8a-c show the PDP for the three S-parameters at 41.5 GHz. Taking a closer look at the area of the component arriving first, it is easy to see that antenna \"2\" (closest to the transmitter) gets the most energy of the three. This can be explained by the fact that also reflections from the floor, tables and chairs are taken together, where those are at the same time partially blocked to the other antennas. Another explanation can be the coupling of the different receiving antennas, resulting in (smaller) modifications of the radiation pattern and hence reducing efficiency and performance. The direct component can be easily identified as the one with the smallest delay. As the receivers move away from the transmitter, that relative delay increases. The same trend can be seen in other contributions produced by scatterers placed between the transmitter and the receivers. However, at the central part of the graphs, there is a contribution that can be seen in Figure 8a (and less clearly in Figure 8c) starting at 20 ns delay and lowering its delay as the receivers move away  
Figure 7: Mapping the measured power delay profile (PDP) and ray-tracing estimations for the corridor channel received by antenna “3” in line of sight (LOS) conditions at the 60 GHz band. from the transmitter. This indicates that the contribution is arriving from a direction opposite to that of the direct component. It was probably produced by the laptop, which was the closest to antenna \"2\". As our simple ray-tracing tool does not take into account the amplitude of the components, it could predict some components that do not appear in the actual measured results due to their large attenuation and low power in the real world. This is the case for the sidewall reflection in Figure 8.  
Finally, the contributions coming from the chairs at the back area of the auditorium can also be identified by their initially longer delays, getting shorter when the receiver moves closer to these scatterers. Figure 8: _Cont._  
Figure 9 shows the measured PDP at the 60 GHz band together with the ray-tracing predictions. Aside from the difference between the three receivers, it is also interesting to recall the differences on the PDP between 40 GHz and 60 GHz. While for 40 GHz there are several multipath components, in 60 GHz only the line of sight and the reflection on the floor are present. The other contributions from the side and back wall suffer stronger attenuations and fall below the receiver's sensitivity (Figure 9a-c). In fact, the ray-tracing simulations predict the time delays that would correspond to those contributions, as can be seen in Figure 10, but no signal over the noise threshold was detected in the measurements. Figure 8: PDP at auditorium, at 41.5 GHz, moving the receiver along the central corridor of the auditorium: (**a**) Received by antenna “2”; (**b**) by antenna “3”; (**c**) by antenna “4”. Figure 9: _Cont._  
Figure 9: PDP at auditorium, at 60.5 GHz: (**a**) Received by antenna “2”; (**b**) by antenna “3”; (**c**) by antenna “4”. As stated before, time dispersion affects the maximum symbol rate that can be used without suffering ISI. In Figure 11, the RMS delay spread for all three S-parameters at both frequencies is plotted as a function of the receiver's position. The results are consistent with what was shown before (Figures 8 and 9). At 40 GHz the amount of multipath is more significant than at 60 GHz; therefore, the RMS delay spread is also larger. Figure 11: _Cont._  
Figure 10: PDP at auditorium, at 60.5 GHz, received by antenna “2”. Another interesting way to analyze the RMS delay spread values is by means of their cumulative distribution functions (CDFs). Computing the CDFs of the RMS delay spread can help to establish a reference value for the delay spread in that environment, by setting a level below which it stays for 99 percent of the time.