Page 72 - ITU Journal Future and evolving technologies – Volume 2 (2021), Issue 2

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 2

observed that the second loor provides a higher mean
EMR than the fourth loor but the standard deviation is

also higher for the former. A similar observation can be
made for the TX locations TX1 and TX2, which are placed
on the second loor. Even though TX2 provides a higher

EMR on the average than TX1, the standard deviation of
the EMR is also higher at TX2, making it a dif icult decision

to choose between the two locations. However, for the

TX locations TX4 and TX5 on the fourth loor, the mean
EMR is higher and the standard deviation of the EMR is
smaller at TX4 than at TX5. Therefore, it can be concluded
that TX4 is a more preferable location than TX5. It should
be noted that for a fair comparison between the EMR of
different TX locations, one should perform several mea‑
surements at the same set of RX locations. Similarly, while
(a) comparing the EMR of different loors, to remove the bias
in the EMR values, we suggest considering a comparable
number of measurements for both LOS and NLOS scenar‑
ios on each loor.

We conclude with an important caveat. The EMR met‑

ric calculated based on the measurements at 28 GHz can‑
not be extrapolated to different bands. For a given prop‑

agation environment, it would be possible to compare

the EMR at two different frequencies (e.g., a mmWave

and a THz frequency) only when the measurements are

available for both of the frequencies. As discussed ear‑
lier in Section 1, the EMR metric depends on the carrier

frequency (due to different levels of attenuation at dif‑

ferent frequencies) along with some other parameters.

This is also the reason why this metric can help to eval‑
uate the suitability of an environment for a particular de‑

ployment band. On the other hand, the EMR is a mea‑

(b)
sure of how many effective alternate paths are available
and how valuable they are for establishing a reliable link.
Since NLOS directional communication is critical to com‑
pensating for the high attenuation at high frequencies

(i.e., mmWave and THz frequencies), the knowledge of
the backup paths is more important at these frequencies.
Therefore, this metric is especially informative for the ef‑
fective deployment and operation of the network infras‑
tructure at higher frequencies.
5. CONCLUSION

In this paper, we introduced a new metric to assess
the effective multipath richness of a given environment,
which is key to the success of directional communications

in next generation wireless networks. Due to the use of
higher frequencies (mmWave and THz), increased link

directionality is critical to be able to maintain a reason‑
(c)
able communication range, and it is critical to assess the
Fig. 9 – Box plots of the EMR from LOS and NLOS measurements for (a) robustness of such directional links against blockages. In
∘
different importance factors ( = 20 , min = −60 dBm), (b) differ‑ this context, our proposed EMR metric takes into consid‑
ent blockage widths ( = 0.4, min = −60 dBm), and (c) different eration the required power level, the angular diversity of
∘
MPC thresholds min ( = 0.4, = 20 ).
the paths, and the angular width of the blockage with re‑
lated for all TX‑RX location pairs on the second and fourth spect to transmitter and receiver positions. It also allows
loor of the library. We also show the same statistics for to adjust the relative importance of the paths (directions)
two different TX locations on the same loors. It can be that are not the primary choice for communications.
58 © International Telecommunication Union, 2021