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