Page 58 - ITU Journal: Volume 2, No. 1 - Special issue - Propagation modelling for advanced future radio systems - Challenges for a congested radio spectrum
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ITU Journal: ICT Discoveries, Vol. 2(1), December 2019




                      Table 5 – Simulation parameters                 ⋅10 −2
                                                                    1
                                                                                                         RTS
                                        = 0.3
                                                                   0.8                                  DACM
             ITU-R urban parameters     = 500 buildings/km 2
                                        
                                        = 15
                                                                   0.6
             Virtual city side length (  )  1600 m                     (   m )
                 BS height (ℎ )      30 m                          0.4
                          BS
                 MS height (ℎ )      1.5 m
                          MS
                Number of MS (  )    3771                          0.2
              BS transmit power (P )  20 dBm                        0
                              t
              Carrier frequency (   )  2 GHz, 28 GHz                −180 −135 −90 −45    0   45   90   135  180
                                
               Cut-off power (P )    -150 dBm                                           (degree)
                                                                                      m
                            off
              Max rays per MS (ℛ MAX )  100                                        (a)       = 2 GHz
                 Cluster gap (  )    50 ∘
                                                                       ⋅10 −2
          data can be clustered by sophisticated algorithms such as  1
                                                                                                         RTS
          hierarchical clustering once the shortest distance    is set  0.8                             DACM
          up. Then ℳ and    can be determined consequently. Fi-
                         m
          nally when taking all MS into consideration,   (ℳ) and   0.6
             (   ) can be obtained by calculating their PMF and PDF        (   m )
            
              m
          respectively. Fig. 6 shows the comparison of the direc-  0.4
          tional channel model and the RTS results regarding    .  0.2
                                                        m
          Adjustments on the curve  itting parameters have been
                                                                    0
          made to have    (   ) symmetric on    = 0 and right con-  −180 −135 −90 −45    0    45   90  135  180
                        
                         m
                                         m
          tinuous. The  inal step is to model the power per clus-                       (degree)
                                                                                      m
          ter. We use the E- ield strength per ray from RTS to solve
          this problem. The total received power per MS is P =                    (b)       = 28 GHz
                                                      r
          ∑ ℛ     , and the power per cluster is P = ∑ ℛ m     [27],  Fig. 6 – The curve  itting of       (   m ) at 2 GHz and 28 GHz.
              =1                          m       =1    
          where    is the time averaged received power in watts of
                   
          the   -th ray, calculated by the E- ield components:  some 5G direction-based applications. We summarize the
                                                               model in two phases, the directionality of the clusters and
                                                               the power distribution. The guideline for the model im-
                        2
                                      2
                     =  8     0  ∣     ,    +      ,   ∣  (8)  plementation is in Algorithm 1.
                     
                        2
                                                2              Algorithm 1 DACM implementation steps
                    =      ∣             ,    +      ,             ,   ∣ .  (9)  1: Get system set-up parameters,    ,   
                                ,  
                       8     0                                  2: for each Receiver    do      
          where      ,    and      ,    are the    and    components of E- ield  3:  Get number of clusters ℳ, following the PMF in Ta-
          of the   -th ray,    and    are the magnitude and the phase  ble 2
          of the ray,    is the wavelength,    is the impedance of free  4:  for all m ∈ ℳ do
                                    0
          space (377 Ω) and    is the overlap of the frequency spec-  5:  Get    following (4)
                                                                           m
          trum of the transmitted waveform and the spectrum of  6:     Condition: MAX(   −    m-1 ) ≤   , m = 2...ℳ
                                                                                       m
          the frequency selectivity of the receiver [27]. The power  7:  Get    following (7)
                                                                           m
          ratio in (6) can be rewritten as:                            Condition: ∑ ℳ     = 1
                                                                8:
                                                                                   m=1  m
                                                                9:     P ←    P
                                                2                       m    m r
                       ∑ ℛ m  ∣             ,    +               ,   ∣  10:  end for
                    =      =1    ,         ,    2  .  (10)
                  m
                       ∑ ℛ  ∣             ,    +               ,   ∣  11: end for
                           =1    ,         ,  
          Two examples of the curve  itting for   (   ) given ℳ = 2,
                                            m
             = 2 GHz and ℳ = 3,    = 28 GHz are shown in Fig. 7.  8.  DACM VERIFICATION
            
                                
                                                               To verify our model, we propose two methods, ray trac-
                                                                                                    ®
          7.  DACM IMPLEMENTATION STEPS USING                  ing simulated veri ication by Wireless Insite and numer-
              SOFTWARE TOOLS                                   ically simulated veri ication by Monte-Carlo simulations.
                                                               For the former method, we consider both virtual city (VC)
          The proposed directional channel model in this paper en-  models generated by Matlab and an actual Melbourne
                                                                                        ®
          ables readers to calculate the distributed azimuth and  CBD footprint imported from online databases [24, 25].
          power in clusters. Such information can be helpful when  The system model for the veri ication follows the same
          directional features play an important role in the de-  set-up as section 3. Then we choose    = 500 receivers
          sign and analysis of the wireless channel, for example,  uniformly from RTS set-up to join the verifying calcula-
           42                                © International Telecommunication Union, 2019
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