Analysis of the Downlink Connectivity Probability
within the Two-Hop Coveragre of an RSU in VANET
Zhenyu Wang, Jun Zheng, and Yuying Wu
National Mobile Communications Research Laboratory
Southeast University
Nanjing, Jiangsu 210096, China
Email: {zywang, junzheng, yuyingwu}@seu.edu.cn
Abstract—Network connectivity has a big impact on the
performance of a vehicular ad hoc network (VANET). This
paper studies the network connectivity problem in a VANET and
focuses on the analysis of the downlink connectivity probability
within the two-hop coverage of an RSU in a network scenario
where data is broadcast from RSUs to all vehicles in the network.
An analytical model is derived to calculate the two-hop downlink
connectivity probability, taking into account the road condition,
traffic distribution, and vehicle capability. The accuracy of the
analytical model is verified through simulation results. The
analytical model can be used to not only calculate the two-hop
downlink connectivity probability and but also investigate the
impact of different parameters on the connectivity probability,
which is useful in the deployment of RSUs in a VANET.
Keywords—connectivity probability; network connectivity;
roadside unit; vehicular ad hoc network
I. I
NTRODUCTION
Vehicular ad hoc networks (VANETs) have received a lot
of attention from both academia and industry in recent years.
A VANET consists of moving vehicles and roadside units
(RSUs), which can dynamically be organized in an ad hoc
manner to provide a variety of potential road safety and
entertainment applications [1-2]. Due to its highly dynamic
nature, the network connectivity of a VANET could often be
intermittent, which would largely affect the network
performance in terms of data transmission delay. To improve
the network performance, it is necessary to improve the
network connectivity.
Network connectivity has been widely studied in the
context of VANETs [3-9]. One way to improve the network
connectivity is to increase the number of RSUs deployed
along a road. But this would increase the deployment cost,
which is not always practical. Another way is to exploit the
advantage of multi-hop transmission, which can increase the
accessible coverage of an RSU by allowing a vehicle to use
its neighbor vehicle as a relay to forward data. However, this
would lead to a larger transmission delay, higher routing
complexity, and larger system overhead. According to [9], in
VANET, a multi-hop link offers a positive system gain only
for a limited number of hops (up to four). Meanwhile, in order
to transmit information to users efficiently in an emergency,
the broadcast mode is usually used in VANETs. For this
reason, the number of hops in data transmission should be
limited to up to four and it is interesting to analyze the
connectivity probability within the coverage of a given
number of hops of an RSU.
In this paper, we study the network connectivity problem
in a VANET. In particular, we consider the analysis of the
two-hop downlink connectivity probability in a network
scenario where data is broadcast from RSUs to all vehicles in
the network. The two-hop downlink connectivity probability
is defined as the probability that all vehicles in the network
are located within the two-hop coverage of the RSUs. To this
end, an analytical model is derived to calculate the two-hop
downlink connectivity probability, taking into account the
road condition, traffic distribution, and vehicle capability. The
accuracy of the analytical model is verified through
simulation results. This analytical model is useful in the
deployment of RSUs. It can be used to investigate if the
deployment distance between two adjacent RSUs can meet
the requirement in terms of the two-hop downlink
connectivity probability, which has an impact on the
transmission delay of the network.
The rest of this paper is organized as follows. In Section II,
we describe the network model and derive the analytical
model. In Section III, we show simulation results to verify the
accuracy of the derived analytical model and investigate the
impact of different parameters on the connectivity probability.
In Section IV, we conclude this paper.
II. A
NALYSIS OF
T
WO
-H
OP
D
OWNLINK
C
ONNECTIVITY
P
ROBABILITY
In this section, we first describe the network model and
then derive an analytical model for calculating the two-hop
downlink connectivity probability.
A
.
Network model
We consider a one-way highway scenario where RSUs are
deployed along the road with a fixed gap, as shown in Figure
1. In the model, L denotes the distance between two neighbor
RSUs and R
u
denotes the transmission radius of an RSU. Data
is broadcast from the RSUs to all vehicles moving on the road.
There are two types of vehicles moving on the road: type 1
and type 2. Type-1 vehicles have a smaller transmission
radius, denoted by R
1
, while type-2 vehicles have a larger
transmission radius, denoted by R
2
, where R
1
<R
2
<R
u
.
This work was supported by the National Natural Science Foundation o
China under Grant No. 61372105 and the Six Talent Peaks Project in Jiangsu
Province under Grant No. 2013-DZXX-010.
978-1-5090-5932-4/17/$31.00 ©2017 IEEE