Page 52 - ITU Journal Future and evolving technologies Volume 3 (2022), Issue 2 – Towards vehicular networks in the 6G era

ITU Journal on Future and Evolving Technologies, Volume 3 (2022), Issue 2

Thus, the optimization is finally formulated as: With (15), the three-dimensional relation curve of
signal distance, main interferer distance and
max = ∑ log ( , ) , (14)

,
,
, , ∈ ∈ success probability could be plotted in Fig. 2. It can
be seen from the figure that is a monotonically
and an updating algorithm to solve this ,
optimization problem by adjusting is derived in growing function with signal distance. Therefore,
,
the following section. for each vehicle, shortening the signal distance will
result in better link success probability. However,
the slope will be vanished, which means that when
5. THE PROPOSED ALGORITHM
the distance is larger, the gain by making it shorter
To obtain the real performance of each is not that much. While, when the distance is small
communication link, we need to use V2X-specific (close to zero), it will be very attractive to make it
and accessible attributes to represent link even shorter.
performance. With the discussion above, the per
node PRR should be predictable based on the two By taking a partial derivative on both sides, we have
the gradient of the utility with respective to as:
distances, e.g., the signal distance and the main ,
interference distance. we propose a two-distance = = ∙ 1 ∙ 1 , (16)
model to predict for a receiver as follows: , , , ,
,
the gradient indicates that the transmitter
,
( , ) = α log , + β log + γ , (15) moves in a fair manner, i.e., if the of one link for

,

,

,
where α is the coefficient associated to signal a receiver is high, the gain from moving closer will

distance , β is the coefficient associated to the be relatively small.

,
main interference distance of a receiver j, i.e., , γ For example, is the transmitter in Fig. 3, ,
i

1
0
is the intercept from the regression. and are three receivers of the current V2X
2
3
The values of α , β and γ are receiver-specific packet, they are traveling in three directions. 0,1 ,

coefficients as their values depend on how many 0,2 , 0,3 ( 0,3 > 0,1 > 0,2 ) are the distance between
interferers are surrounding j as well as the transmitter 0 and receivers. ,
4
strengths of the interferences. It is because the and are three interferers
6
5
simplified formula of , considers the main using the same resource with transmitter . ,
1
0
2
interference distance only. The accuracy of using and ( > > ) are the distance between
2
3
1
3
the main interference to represent the whole interferers and receivers. has a good packet
2
interference in the SINR term in (7-8) varies when receiving probability because the signal distance is
the composition of interference at j varies. Thus, we small while the interference distance is big.
propose to assume the coefficients α , β and γ are Similarly, we can find that has a modest
1

dependent on the Number of Surrounding receiving probability while has the lowest
3
interfering Vehicles (NSVs). The value of α , β and receiving probability. In order to optimize the PRR,

γ will be found via regress in Section 6 for different the 0,1 , 0,2 and 0,3 need to be adjusted by moving

the transmitter. The higher the return it is
numbers of NSVs.
estimated to have from the moving closer to a
receiver , the more the transmitter should move
towards the receiver .
Fig. 2 – Three-dimensional relation curve of signal distance,
interferer distance and success probability
Fig. 3 – The position of transmitter, receivers and interferers

40 © International Telecommunication Union, 2022