Page 280 - Kaleidoscope Academic Conference Proceedings 2024

2024 ITU Kaleidoscope Academic Conference

Figure 1- STAR-RIS assisted V2V NOMA system Figure 2- AF relay assisted V2V NOMA system
power levels of each vehicle to create a real-life scenario to = = ⋯ = = 1. For effective data transmission,

1
2
compare the feasibility of both the models. the RIS's reflection phase shift matrix and the ’s

transmitted beam configuration work jointly. Since the
2. SYSTEM MODEL channel follows reciprocity, the channel state information
(CSI) acquired by uplink pilot training can congruently be
2.1 RIS assisted NOMA V2V model utilized for transmission in downlink for all quasi-static flat
fading channels. If the reflected signal by RIS is twice or
The system model for the proposed STAR-RIS assisted V2V more, the path loss of the signal will become more
network has been shown in Fig. 1. In this arrangement, one significant due to the multiple reflection of the transmitted
vehicle has been considered the source vehicle, this can signal. In addition, it is anticipated that has full

be increased to any finite number of vehicles, which tries to information of the CSI, which will support the efficient
communicate with the destination vehicles , where ∈ performance by STAR-RIS, this can be achieved using [14].

{1,2 … , }. Let us assume the vehicle is single antenna

system and the vehicle is also carrying single antenna each. The received signal at vehicle is given by

It is assumed that there is no cellular link for direct
communication between these vehicles. This transmission H H )
L
h h  +
x +
has been proposed to be supported via a reflected path y = ( rl sr h sl  i i  , i (2)
l
through RIS. i= 1
Where  is the beamforming vector of ℎ vehicle , is
The RIS used in this model have N discrete elements. It is i
assumed that the transmission is carried out by means of a the message signal transmitted by the source vehicle and

single large RIS also known as single RIS-assisted is the additive white Gaussian noise having the mean

2
transmission (SRAT) through dedicated short-range value as 0 and the variance of [15]. At the receiver end
communication (DSRC). the NOMA adopts the successive interference cancellation
technique to retrieve the source’s information [16]. The
The channel between the source or transmitter vehicle and vehicle decodes its signal treating the rest information

1

the STAR-RIS is represented by ℎ ∈ ℂ 1 , the channel as noise. When is more than or equal to 2, the user detects

between RIS and is given by ℎ ∈ ℂ 1 and the channel each signal separately; afterwards, after removing other

between and is given by ℎ ∈ ℂ , which can be the vehicles detected signals from the actual received signal, it

line of sight (LoS) path links. For N discrete elements, the regains the signal amplitude and finds the remaining signals.
reflection coefficients matrix of STAR-RIS can be written as This process is repeated until the requested signals are
decoded. The sequence of the receiver vehicles depends
 = diag  e j 1 , 2 e j 2 ,..., N e j N  (1) upon the channel condition, as the distance between the
source vehicle and the destination vehicles increase the
 1
channel condition degrades which can be given by ‖ℎ ‖ ≤
1
Where is the reflection coefficient of the ℎ ‖ℎ ‖ ≤ ‖ℎ ‖ ≤ ⋯ ≤ ‖ℎ ‖ , where ℎ vehicle is the

2
3

reflecting element of the STAR-RIS such that ∈ [0,1] farthest and Vehicle is the nearest one.
1

whereas is the phase coefficient of ℎ element and

∈ [0, 2 ] . Every reflecting element on the RIS is The signal available at the receive vehicle before its

considered to operate at maximum reflection, implying that decoding can be written as
each one's amplitude coefficient satisfies the relation
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