19-05-2012, 01:26 PM
Node Connectivity in Vehicular Ad Hoc Networks withStructured Mobility
[attachment=22450]
Abstract1
Vehicular Ad hoc NETworks (VANETs) is a
subclass of Mobile Ad hoc NETworks (MANETs).
However, automotive ad hoc networks will behave in
fundamentally different ways than the predominated models
in MANET research. Driver behaviour, mobility constraints
and high speeds create unique characteristics in the network.
All of these constraints have implications on the VANET
architecture at the physical, link, network, and application
layers. To facilitate the cross-layer designs for VANETs,
understanding of the relationship between mobility and
network connectivity is of paramount importance. In this
paper, we focus on studying transport systems with
structured mobility (e.g., bus systems), which have unique
characteristics on the road such as fixed routes that have
never been explored in previous work. The main
contributions of this paper are three-fold: 1) we provide an
analytical framework including the design requirements of
the mobility model for realistic vehicular network studies,
and metrics for evaluating node connectivity in vehicular
networks; 2) we demonstrate.
INTRODUCTION
Mobile Ad hoc NETworks (MANETs) is a collection of
wireless nodes communicating with each other in the
absence of any infrastructure. Classrooms, battlefields and
vehicle-to-vehicle communications are a few scenarios
where MANETs can be applied. Due to its readily
deployable nature, it is attracting a lot of attention from the
research community.
Inter-vehicle communication network or Vehicular Ad
hoc NETworks (VANETs) is a subclass of MANETs, which
would perform crucial functions in road safety, detection of
traffic accidents and reduction of traffic congestions.
However, VANETs exhibit very different characteristics
from MANETs. Specifically, the constraints on vehicle
movements, varying driver behaviour, and high mobility
cause rapid topology changes, frequent fragmentation of the
network, and limited utility from network redundancy.
These changes have implication for the VANETs
architecture from the physical to the application layers.
In VANETs, the impact of mobility on the performance
of communication protocols can be realized as the block
diagram shown in Figure 1. First, different mobility models
have different degrees of spatial dependence, temporal
dependence, relative speeds and geographic restrictions,
which give rise to different link durations between nodes
and thus distinct path availabilities for multi-hop
transmissions. Network connectivity in turn influences the
performance of the communication protocol. It was shown
in [1] that higher link duration will result in higher
throughput and vice versa.
Figure 1. Block diagram illustrating the impact of mobility on the
performance of communication protocols.
Therefore, to ensure the design feasibility of VANETs,
we require a fundamental understanding of the impact of
mobility on network connectivity (the first two blocks in
Figure 1), which is the focus of this paper. In this paper, we
show through simulations that commonly used mobility
models in MANET research are insufficient to capture realworld
vehicle movements, and suggest relevant
mobility/traffic models, transport-related elements and
connectivity metrics that should be included in the
framework for VANET studies. Specifically, we focus on
studying transport network with structured mobility, such as
bus network, which have unique traffic patterns on the road
with fixed routes and timetables that have never been
investigated in prior work. We simulate a bus network on a
road-based map and demonstrate the impact of advanced
traffic models on node connectivity and, in essence, show
that multi-hop paths perform dramatically poorer than
single-hop links in the vehicular environment. Even if we
increase the transmission range of vehicles, it is found that
multi-hop connectivity cannot be improved.
This paper is organized as follows. Section II delivers
related work on VANETs in terms of the mobility models
and traffic simulators. Section III presents the list of
parameters that should be considered in a realistic VANET
simulation, especially for buses. Section IV introduces the
1
The work reported in this paper forms part of the MESSAGE project.
MESSAGE is a three-year research project which started in October 2006 andis funded jointly by the UK Engineering and Physical Sciences ResearchCouncil and the UK Department for Transport. The project also has thesupport of nineteen non-academic organisations from public sector transportoperations, commercial equipment providers, systems integrators andtechnology suppliers. Moreinformationisavailablefromtheweb site
www.message-project.org. The views expressed in this paper are those of theauthors and do not represent the view of the Department for Transport or anyof the non-academic partners of the MESSAGE project.
RELATED WORKS
In this section, we first present the commonly used
mobility models in MANET research and the macromobility
and micro-mobility models in transport studies in
Subsection A, followed by the review of existing traffic
simulators in Subsection B.
A. Mobility Models
Several mobility models are widely used in the research
community of MANETs. However, classic and purely
random models, such as the Random Walk, Random
Waypoint, and Reference Point Group Mobility models [2]
are insufficient to capture the major characteristics of the
real-world vehicle movement, these models can generate
unreliable results as they do not even pose fixed road
constraints to nodes
[attachment=22450]
Abstract1
Vehicular Ad hoc NETworks (VANETs) is a
subclass of Mobile Ad hoc NETworks (MANETs).
However, automotive ad hoc networks will behave in
fundamentally different ways than the predominated models
in MANET research. Driver behaviour, mobility constraints
and high speeds create unique characteristics in the network.
All of these constraints have implications on the VANET
architecture at the physical, link, network, and application
layers. To facilitate the cross-layer designs for VANETs,
understanding of the relationship between mobility and
network connectivity is of paramount importance. In this
paper, we focus on studying transport systems with
structured mobility (e.g., bus systems), which have unique
characteristics on the road such as fixed routes that have
never been explored in previous work. The main
contributions of this paper are three-fold: 1) we provide an
analytical framework including the design requirements of
the mobility model for realistic vehicular network studies,
and metrics for evaluating node connectivity in vehicular
networks; 2) we demonstrate.
INTRODUCTION
Mobile Ad hoc NETworks (MANETs) is a collection of
wireless nodes communicating with each other in the
absence of any infrastructure. Classrooms, battlefields and
vehicle-to-vehicle communications are a few scenarios
where MANETs can be applied. Due to its readily
deployable nature, it is attracting a lot of attention from the
research community.
Inter-vehicle communication network or Vehicular Ad
hoc NETworks (VANETs) is a subclass of MANETs, which
would perform crucial functions in road safety, detection of
traffic accidents and reduction of traffic congestions.
However, VANETs exhibit very different characteristics
from MANETs. Specifically, the constraints on vehicle
movements, varying driver behaviour, and high mobility
cause rapid topology changes, frequent fragmentation of the
network, and limited utility from network redundancy.
These changes have implication for the VANETs
architecture from the physical to the application layers.
In VANETs, the impact of mobility on the performance
of communication protocols can be realized as the block
diagram shown in Figure 1. First, different mobility models
have different degrees of spatial dependence, temporal
dependence, relative speeds and geographic restrictions,
which give rise to different link durations between nodes
and thus distinct path availabilities for multi-hop
transmissions. Network connectivity in turn influences the
performance of the communication protocol. It was shown
in [1] that higher link duration will result in higher
throughput and vice versa.
Figure 1. Block diagram illustrating the impact of mobility on the
performance of communication protocols.
Therefore, to ensure the design feasibility of VANETs,
we require a fundamental understanding of the impact of
mobility on network connectivity (the first two blocks in
Figure 1), which is the focus of this paper. In this paper, we
show through simulations that commonly used mobility
models in MANET research are insufficient to capture realworld
vehicle movements, and suggest relevant
mobility/traffic models, transport-related elements and
connectivity metrics that should be included in the
framework for VANET studies. Specifically, we focus on
studying transport network with structured mobility, such as
bus network, which have unique traffic patterns on the road
with fixed routes and timetables that have never been
investigated in prior work. We simulate a bus network on a
road-based map and demonstrate the impact of advanced
traffic models on node connectivity and, in essence, show
that multi-hop paths perform dramatically poorer than
single-hop links in the vehicular environment. Even if we
increase the transmission range of vehicles, it is found that
multi-hop connectivity cannot be improved.
This paper is organized as follows. Section II delivers
related work on VANETs in terms of the mobility models
and traffic simulators. Section III presents the list of
parameters that should be considered in a realistic VANET
simulation, especially for buses. Section IV introduces the
1
The work reported in this paper forms part of the MESSAGE project.
MESSAGE is a three-year research project which started in October 2006 andis funded jointly by the UK Engineering and Physical Sciences ResearchCouncil and the UK Department for Transport. The project also has thesupport of nineteen non-academic organisations from public sector transportoperations, commercial equipment providers, systems integrators andtechnology suppliers. Moreinformationisavailablefromtheweb site
www.message-project.org. The views expressed in this paper are those of theauthors and do not represent the view of the Department for Transport or anyof the non-academic partners of the MESSAGE project.
RELATED WORKS
In this section, we first present the commonly used
mobility models in MANET research and the macromobility
and micro-mobility models in transport studies in
Subsection A, followed by the review of existing traffic
simulators in Subsection B.
A. Mobility Models
Several mobility models are widely used in the research
community of MANETs. However, classic and purely
random models, such as the Random Walk, Random
Waypoint, and Reference Point Group Mobility models [2]
are insufficient to capture the major characteristics of the
real-world vehicle movement, these models can generate
unreliable results as they do not even pose fixed road
constraints to nodes