Page 50 - 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

transmitter at position ( , ), with velocity ⃗⃗⃗⃗ , should be 20% of the total resources in the

and receiver at position ( , ), with velocity ⃗⃗⃗⃗ resource selection window. Otherwise,

could be calculated according to: increase the threshold RSRP by 3dB until the
2
2
, = √( − ) − ( − ) , (1) conditions are met.

• Sort the candidate resources according to their
, = √( ⃗⃗⃗⃗ − ⃗⃗⃗⃗⃗ ) . (2) RSSI, and select the best three resources.
2

• Randomly select one of the three resources.
After a packet is transmitted using the chosen
resource, the received signal power , of link l is
computed as:
, = ∙ , ∙ ℎ , 2 . (5)

The interference power from one of interferers
,
to receiver is calculated as:
, = ∙ , ∙ ℎ , 2 , (6)

where is the transmission power of , , is the

path loss from vehicle to . And the total
interference affecting the signal transmitted on link
(a, b) is:

Fig. 1 – C-V2X communication system model. , = ∑ c∈ , , (7)
Next, the data obtained from the road model could In (7), the summation suggests that the total
be used to the network model. It is assumed that the interference affecting the signal transmitted on link
transmission power of transmitter is , the (a, b) is coming from the set of all nodes that are

carrier frequency of the signal is , and the noise concurrently transmitting at the same time, i.e., the
power is considered as Gaussian white noise. set denoted by . The channel fluctuation in time

Therefore, path loss from vehicle to is , and and frequency, i.e., compliant to winner model,
the Doppler between them is , : ℎ , is the mean channel coefficient between and
, and ℎ is the mean channel coefficient between
,
, = ∙ [ 0 ] , (3) and . The mean is applied across all Res in
, reference symbols of that packet. Then the SINR of
, = 2∙ ∙ , . (4) link to could be calculated as:
8
3×10
,
The path-loss model indicates that the path-loss , = , + . (8)
gain for the link from to is proportional to the In order to obtain the link success probability
,
⁄
order of 1 , , where equals to 2 in the free of each vehicle communication link, considering the
space scenarios. Then the resource selection randomness of the vehicle network channel, we
process of SPS could be simulated. First, calculate perform per-link bit level simulations on discrete
the measured Reference Signal Received Power SINR and velocity points, and obtain curves of link
(measured RSRP), threshold Reference Signal success probability as a function of the Doppler and
Received Power (threshold RSRP) and Received the SINR by linear interpolation. The interpolated
Signal Strength Indicator (RSSI) of the resources, curves form the C-V2X physical abstraction and is
and then make a list. The autonomous scheduling used to obtain a the success probability for a
with three steps according to the SPS mechanism is transmission from vehicle to vehicle using the
as follows. Doppler and SINR calculated from (4) and (8),

• If an SCI is received on the time slot, or the respectively. For a transmitter, the transmission
corresponding time slot is reserved by the power s values returned by each transmission link
previous SCI, and the measured RSRP is larger could be added to obtain the per-node PRR. As our
than the threshold RSRP, the resource is current study focuses on a low-modest speed
excluded. The remaining candidate resources scenario with high vehicle density, i.e., urban
scenarios, the change of Doppler has little effect on

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