Page 48 - 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

accounted by controlling the mobility of the the performance of the link level and the distance
transmitter, i.e., how the transmitter moves. between transmitter and receiver. Since Media
Access Control (MAC) parameters, such as the
The rest of this paper is organized as follows.
Section 2 introduces related work on controlled probability of retaining wireless resources and
mobility for PRR optimization. Section 3 and Section resource counters, will affect the duration of
4 describe the system settings and the optimization wireless resource conflicts. A new algorithm is
problem formulation, respectively. The proposed designed to optimally configure these parameters
algorithm is derived in Section 5. And performance according to the current vehicle density in [6].
of the algorithm is evaluated in Section 6 with However, C-V2X specific procedures such as the
blind-detection of PSCCH without knowing the
numerical results. Finally, Section 7 concludes this
paper. cyclic shift used by the other nodes, autonomous
SPS scheduling and carrier sensing to decide the
2. RELATED WORK transmission resource, and the non-feedback
mechanism all changes the link level sidelink
Road safety use cases of C-V2X, where the vehicles performance. These studies were not carried out
send out status-update and warning messages, based on realistic sidelink performance models of
require the messages to be disseminated to as many C-V2X mode 4 and this makes it difficult for the
neighboring vehicles as possible. The connectivity results to reflect the true network level
and coverage issue has been well studied in the performance.
literature, while one important degree of freedom Traditionally, wireless multi-hop networks are
has been lightly explored. That is the vehicles’ considered to be fixed and easy to manage and
mobility. Mobility indeed is an active impacting control. However, in view of the development of the
factor in the connectivity and coverage for V2X
networks. It defines the network topology. Internet of vehicles and UAV, mobile multi-hop
Moreover, if vehicles could move wisely in time, the networks began to receive research attention [7-9].
network coverage, in terms of the Packet Reception The impact of node mobility on wireless multi-hop
Rates (PRRs), could be further improved. However, networks resource allocation is in fact two-sided.
due to the following challenges, the controlled On one hand, stationary nodes give us convenience
mobility has been lightly reviewed in vehicular in network management and control. For example,
network PRR optimizations. nodes’ position information does not need to be
updated frequently, and there is no fast channel
• The traditional Signal-to-Interference-plus- fading caused by relative movement between nodes.
Noise Ratio (SINR)-based link model only However, on the other hand, stationary nodes
parameterizes distance. However, finding the constrain the exploitable potential of the wireless
optimal distances does not necessarily produce network. For example, in terms of network capacity,
an optimal solution in position. Tse et al. [10-11] pointed out that the random
• Most of the optimization needs to know SINR movement of nodes in a wireless network (even if it
feedback, but the broadcast has no SINR is only a random movement in a one-dimensional
direction) is able to improve the theoretical
feedback.
network capacity from √ to approximately 1,
In the following, we present a literature review on where N is the number of nodes in the network. It is
PRR optimization and controlled movement for foreseeable that if nodes perform ‘wisely’
vehicular networks followed with a comparison movement in a controlled manner, the capacity of
between our proposed solution and existing studies. the wireless network should have more room to
grow.
The performance of C-V2X mode 4 has been a
research focus in the past few years. The As for the problem of controlled movement, the
relationship of the PRR and the distance between research in [12] studied how the robot can move to
the transmitter and the receiver is studied in [4]; it the required position autonomously for sensing and
is pointed out that the PRR is positively correlated data acquisition. The initial and possibly
with the distance between the users. The disconnected networks are self-organized via an
transmission errors of mode 4, such as those caused autonomous movement to form a bi-connected
by half-duplex propagation and packet conflict, are network. In order to use only one-hop information
comprehensively studied in [5]. The author for movement control, achieve maximizing network
proposes that the occurrence of conflict depends on coverage and minimizing the total moving distance,

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