Page 282 - Kaleidoscope Academic Conference Proceedings 2024
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2024 ITU Kaleidoscope Academic Conference




                                                                 12
              14      RIS -NOMA
                      AF Relay NOMA                                       RIS-NOMA
              12                                                 10 8     AF Relay NOMA
             Throughput (Mbps)  8 6                             Sum Rate (Mbps)  6
              10





              4                                                   4
                                                                  2
              2
              0                                                   0
                      5     10     15     20     25     30         0      5     10     15     20     25    30
                              Transmit Power (dB)                                    SNR(dB)


               Figure 4- Throughput versus Transmit power          Figure 5- Throughput versus Transmit power
           The resultant SINR can be expressed using the modelling   interference  and  improve  the  total  signal  strength  that  is
           discussed in [18] and can be written as            received at the destination. However, The AF relay is a more
                                                              straightforward  method  in  which  the  relay  amplifies  and
                                    1  h h  P                transmits  the  signal  that  has  been  received  without  any
                                      sR
                      =               1  1 R d         (13)   external processing and hence lags at high SNR.
                        (  2  h  2  +  1  2  h  h  / h  2 )  2
                                   +
                          1
                              1 R d
                                            1 R d
                                                 2 R d
                                         2 1 R
                                      1
                                        R
                                                                To facilitate spatial multiplexing, RIS regulates the spatial
                                                              distribution  of  reflected  signals  by  serving  multiple  users
           The  achievable  rate  and  the  throughput  can  be  calculated   simultaneously,  thus,  it  has  the  potential  to  enhance  the
           using the equation 6.                              system's capacity and throughput and this can be seen from
                                                              the plot shown in the Fig. 4. Additionally, by generating a
                       3.  SIMULATION RESULTS                 variety of propagation paths, reducing fading, and enhancing
                                                              overall  system  reliability,  the  RIS  can  offer  high  spatial
           In order to validate the closed form expressions obtained in   diversity  as  compared  to  the  AF  relay.  The  AF  relay  has
           the proposed work presented in section II, systematic monte   limited scope for beamforming capabilities as compared to
           Carlo simulation has been performed for both the STAR-RIS   RIS and hence low throughput as compared to the RIS.
           NOMAV2V as well as for the AF relay-based NOMA V2V
           models. Thorough investigation was carried out for accuracy   Fig. 5 illustrates the sum rate plot for RIS and AF relay, The
           of  the  benchmark  performances  of  both  the  model  and  a   results of the simulation indicate that under all conditions,
           comparative  study  was  carried  out  for  the  maximum   the sum rate of the signal monotonically increase when the
           achievable  rate  and  throughput  of  the  both  models.  The   maximum transmit power threshold of     rises and when the
                                                                                                
           entire  model  was  simulated  for  2  vehicular  models,  the   transmit power threshold of     rises, the power assigned to
                                                                                        
           distance between the vehicles and RIS and Vehicle to relay   vehicles increases, resulting in a higher achievable rate that
           were all kept at 100 m. the model was validated for Rayleigh   the user demands. In order to send the signal point to point,
           channel for urban scenario and the channel gain was taken   to  a  specific  vehicle,  the  SDR  algorithm  modulates  the
           the  random  value  between  zero  and  one.  The  power   reflection phase shift of each reflecting unit on the RIS by
           transmitted by both the relays have been assumed to be same   enhancing  the      maximum  transmit  power  threshold
                                                                              
           and was taken as 1W, the number of RIS element was taken   simultaneously optimizing the phase shift of reflected signal
           as 81, noise power was taken as -80dBm in all the cases.   which substantially increases the vehicles signal rate.
           First and the foremost, In the Fig. 3, maximum achievable   In  the  proposed  comparison  of  both  methods,  STAR-RIS
           rate of the two models has been compared with respect to the   V2V  NOMA  has  outperformed  AF  relay  V2V  NOMA.
           SNR, It can be noticed that at low SNR values the achievable   However, the AF relay has better scope, it does not require
           rate of RIS assisted model and AF relay assisted model both   accurate channel state information (CSI) for beamforming or
           have comparable values but as the SNR increases beyond 15   reflection corrections, it works better in situations where it is
           dB the AF relay assisted model lags the RIS assisted model   difficult to get CSI quickly and accurately. Since AF relay
           and this is possible because the reconfigurable elements are   does  not  depend  on  exact  placement  or  reflection
           introduced by STAR-RIS, which have the ability to reflect   modifications, it may be more adaptable in scenarios where
           and  change  the  incident  signals  simultaneously.  By   it is difficult to determine the relay's exact location.
           implementing intelligent adjustments to the phase shifts of
           these elements, RIS is able to generate constructive





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