International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
Conveying Messages to Far Vehicles using RSUs
A.Vamsi Teja 1, Ch. Sudersan Raju 2
Final year student, M.Tech in DSCE, B.I.T Institute of Technology, HINDUPUR Andhra Pradesh, INDIA.
2
Assoc. Prof, B.I.T Institute of Technology, HINDUPUR Andhra Pradesh, INDIA.
Abstract— Vehicular networks have attracted great interest in
the research community. In case of highway traffic, position
based routing can deal well. However, it has difficulties to handle
obstacles (buildings) for city scenarios. In our research work we
operate the infrastructure of road side units (RSUs) to route
packets in VANETs efficiently. The algorithm (CAN DELIVER)
which was used in existing paper is extremely different and long
scenarios will be used. Now the proposed algorithm (EDSR) is
simpler, the complexity of the system development is reduced
and provides high efficiency and throughput as like existing. The
performance of our system is evaluated using ns2 simulation
platform and compares our scheme to the existing solutions.
Keywords— road side units (RSUs), routing, vehicular ad hoc
networks (VANETs).
I. INTRODUCTION
Vehicular network (VANET) is a special type of mobile
ad hoc network (MANET). The most distinguished feature of
VANET is that vehicles have some restricted mobility pattern.
Specifically, all vehicle movements are constrained in roads,
which have a static structure. Vehicles can only move in either
direction on the road, and move at a speed restricted by the
speed limit. In addition, some vehicles, such as buses, have
pre-determined routes. Many algorithms have been proposed
to utilize this predictable mobility for data delivery in
VANET.
A VANET is a group of vehicles that are equipped with
wireless communication devices, positioning systems, and
digital maps. In VANETs vehicles may connect to roadside
units (RSUs), which are connected to the Internet and may
also be connected with each other via a high-capacity mesh
network. VANETs routing is limited to vehicles few hops
away. But, communicating data to far vehicles is also
necessary.
Hence multi hop routing protocols are necessary. Most
routing protocols use position based protocols that uses the
geographic coordinates of vehicles. Some protocols [2]
consider carry and forward approach which are delay tolerant
algorithms. Position-based protocols [5] consider dense
conditions in which a vehicle always finds a neighbour to
forward to. Delay-tolerant algorithms do not perform well in
dense cases. In this paper, we propose to utilize RSUs to route
packets to far locations. A vehicle S requesting to send a
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packet P to a far vehicle D can send P to its nearest RSU (R1),
which, in turn, sends P to the nearest RSU to D (R2) with the
help of the RSU network. RSU2 then sends P to D through
multi hop.
The reason we are using RSUs to route packets is that
RSUs are a fixed infrastructure. It is so easy to transmit a
packet to a fixed target than to a remote moving target. More
over, the delay of sending the packet through the fixed RSU
network is much less than through the VANET. The design of
our system is divided into two basic parts: the first part
governs routing from a vehicle to its nearest RSU, and the
second part handles routing from RSUs to vehicles.
The applications that utilize great from our routing scheme
include queries about road conditions in far-away locations.
For example, consider a vehicle heading from one place to
another new place, the person who is driving might request
from an RSU on the road in which he is heading to
information about the road condition and the amount of traffic
in certain streets or information about some weather variables,
or even request road navigation information from a point to
another new place based on the expected traffic conditions.
[6] Says that, Dedicated Short range Communication is
better suited to vehicle to vehicle communication than 3G and
4G. Since the cost of cellular data communication is high and
expensive for unlimited plans.
The impressive perspectives promised by Vehicular Ad hoc
Networks (VANETs) have made it a worldwide focal area of
research. Ubiquitous connectivity on roads, improved safety
of driving, and reduced traffic congestion along with many
enterprise applications are just a few to name when it comes
to what VANETs have to offer. Most of the VANET
applications critically rely on routing protocols. Thus, an
optimal routing strategy that makes better use of resources is
crucial to deploy efficient VANETs that actually work in
volatile networks.
In section II we are going to discuss the existing system
details and the methodology of our proposed system and how
we overcome the complexity of the existing system. In section
III we are going to discuss about the results of our system. In
this section we will provide the comparison results of our
proposed system with the existing system.
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II. SYSTEM DESIGN
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International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
A. Existing System
The existing system CAN DELIVER [1] depends on the
system of RSUs to relay packets to the distant locations. The
existing system uses four algorithms to send the data packets
from the source vehicle to the destination vehicle, where the
complexity of the system is more in the existing system.
Fig. 2.1. (a) Vehicle’s vicinity and Hello packets, (b) RSU vicinity and
beacons, and (c) three sample scenarios in CAN DELIVER.
The above fig 2.1 shows how the existing system works,
where fig 2.1(a) represents the vicinity area of a vehicle and
how it sends Hello packets. The fig 2.1 (b) shows the vicinity
area of RSU and how it receives periodic beacons from
vehicles. The fig 2.1 (c) shows the three cases that are
considered in CAN DELIVER where case 1 represents when
source is in single hop distance to destination. Case 2
represents when source destination are present in same RSU
and case 3 shows when they are in different RSU vicinity
areas.
B. Proposed System
We call our proposed system as EDSR (Enhanced
Dedicated Shortest Routing) algorithm. Since, it finds the
shortest path between the vehicle and RSU. The EDSR
depends on RSUs to deliver packets to distant locations. In [7]
some RSUs are standalone and some wired to each other. In [4]
it is assumed that all RSUs are connected over links. In our
work it is assumed that some RSUs are wired to each other
and others connect to RSU network via Internet. We assume
vehicle is equipped with a positioning system (GPS), has
access to maps of its locality and equipped with navigation
system. We assume vehicles and RSUs synchronize their
clocks from accurate time information from GPS.
Each vehicle V adds its own location (geographic
coordinates), speed, direction, and timestamp (LSDT) to the
first Hello it sends to its neighbours. Each neighbour adds the
data of V to its L. After this, each vehicle includes in a Hello
its LSDT as well as the data it has in L. Each vehicle
periodically sends Hello packets to its neighbours, and
maintains a list L of pseudonyms, positions, speeds,
directions, and timestamps of vehicles in its vicinity. The list
L is built and updated as follows: Each RSU receives periodic
beacons from all vehicles in its vicinity. A beacon contains the
LSDT of a vehicle V and is unicasted by V to its nearest RSU.
The vicinity of an RSU R can be described as a circle with R
in the center and a radius equal to the distance to its farthest
RSU neighbour. An RSU uses the LSDTs to send packets to
their vehicles. Each vehicle that receives a Hello will add an
entry in the Hello to L.
In the proposed system EDSR, whenever any vehicle S
wants to send a packet to an RSU R it examines whether R is
within its transmission range. S uses the digital maps to find
the shortest path between vehicle and RSU. It will calculate
the distance between S and R using way points in map. V
checks if any of its neighbours are nearer from it to R. If S
finds that it has no neighbours nearer from it to R, it moves P
to a queue (keeps carrying it) and checks (every Tq seconds) if
it has new neighbours nearer to R. If S doesn’t receive an
ACK within Tw then it resends P.
V= vehicle speed, d= distance between S and R
= Avg distance during which vehicle carries P
C= transmission time between two neighbours
r = transmission range
= safety time factor.
After RSU receives P then it knows the location of D from
periodic beacons and it estimates the effective area in which
the D will be present while P reaches from R to D. Next R
estimates D’s position when P reaches D i.e., distance
travelled dc. Time required for P to reach D is tf
dc= v1 X tf
The next step taken by R is estimating the area (AE) to
which P should be sent. R defines AE as a circle whose center
is dp and radius ra, where dp is the estimated coordinates of D,
and ra is the error factor in calculating dt. For example, r
could be set to (0.5 × dt). It can be proved that D should be
inside AE, even if it turns to side roads more than once. Next,
R examines the roads within its transmission range to find the
nearest one to centre of AE. After R chooses road then it
transmits P to neighbour vehicles to D. If any intermediate
vehicle N receiving P is outside estimated area then it checks
whether D is neighbour, otherwise it updates newly estimated
area in which D is present and looks for nearest neighbour to
forward P to D. If no neighbour is present then it waits for
some time and rechecks if it is in estimated area. If N is in the
estimated area then it checks D is neighbour. Otherwise it
finds any neighbours to forward P.
The following Fig 2.2 will explain how our proposed system works.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
Start
Initialize the source and
destination
Identify the RSU
Transmit the packets to
RSU
Locate the destination
at RSU
Estimate the effective area
of Destination
Inside
Whether the N
is inside or
outside
Outside
Yes
If D is
neighbour
No
If D is
neighbour
Yes
Transmit P directly to
D
No
Update estimated
area
Transmit P
directly to D
Drop P
No
Drop P
If it has
neighbours
End
Yes
End
Transmit P to
neighbours
Transmit P nearest
neighbours
Delay
III. RESULT ANALYSIS
Fig 2.2 Flow Chart of EDSR
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International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
This section gives the simulations that were performed to
evaluate EDSR using the network simulator ns2 software
(version 2.34). The default number of vehicles was set to 300,
and their minimum and maximum speeds were set to 30 and
70 m/s. Ten RSUs were deployed uniformly across the map to
balance their loads as much as possible. Some RSUs were
wired to each other, whereas the other RSUs were simulated
to have an Internet connection. We compared our system
EDSR with the existing method CAN DELIVER. The metrics
used for comparison are Throughput, End to End Delay and
Packet Delivery ratio. Fig3.1 (a),(b),(c) shows how the three
compared metrics change when number of vehicles is varied
between 0 and 12. The Fig3.1 (d),(e),(f) shows the comparison
of our proposed algorithm with the existing method. This
proves that our proposed method improved the efficiency and
reliability of the system in delivering the message packets to
the destination.
Fig 3.1(d) Comparison of Throughput of EDSR and CAN DELIVER
Fig 3.1(e) Comparison of End to End Delay of EDSR and CAN DELIVER
Fig 3.1(a) Throughput of EDSR
Fig 3.1(f) Comparison of Packet Delivery Ratio of EDSR and CAN
DELIVER
Fig 3.1(b) End to End Delay of EDSR
Fig 3.1(c) Packet Delivery Ratio of EDSR
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Most works on VANETs that consider using 3G or 4G
focus on transportation and safety applications (since these
applications do not require large data packets to be sent to the
cellular infrastructure). In addition, many of these works [3]
mention that sending data packets from a vehicle to another
via the cellular network requires a dedicated channel (DCH),
and hence is not feasible.
An important parameter that highly affects the
performance of EDSR is the number of RSUs (NRSU). In the
previous results, the system was tested with 20 RSUs. In this
section, we simulated scenarios with 28 RSUs uniformly
distributed across the network. The Fig 3.2 shows the route
map of the nodes. The results were calculated for a vehicle
that is a distance dmed away from its nearest RSU sends
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International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
requests to it. dmed was fixed at 1 km, and the density of
vehicles Nd was varied between 0 and 12 vehicles. The
table3.1 shows default simulation parameters.
Jul. 2007.
[5] J. Zhao and G. Cao, ―VADD: Vehicle-assisted data delivery in vehicular
ad hoc networks,‖ IEEE Trans. Veh. Technol., vol. 57, no. 3, pp. 1910–
1922, May 2008.
[6] Y. Ko, M. Sim, and M. Nekovee, ―Wi-Fi based broadband wireless access
for users on the road,‖ BT Technol. J., vol. 24, no. 2, pp. 123–129,
Apr. 2006.
[7] E.Fonseca, A.Festag, ―A Survey of existing approaches for secure adhoc
routing and their adaptability to VANETS‖, NEC network laboratories, 28
pages, Version 1.1, March- 2006, pp. 1-28.
[8] The Network Simulator – ns-2,‖ http://www.isi.edu/nsnam/ns/
[9] http://www.isi.edu/nsnam/ns/tutotial/
Mr. A.Vamsi Teja received
Bachelor’s Degree in Electronics
and Communication Engineering
from JNTU, Hyderabad and
Studying Master’s degree in Digital
Systems and Computer Electronics
in BIT Institute of Technology,
Hindupur affiliated to JNTU,
Anantapur
.
Fig 3.2. Network Animator result of EDSR
TABLE 3.1: SUMMARY OF DEFAULT SIMULATION PARAMETERS
Parameter
Value
Simulation Time
100 ms
Minimum possible radius of estimated
area
Packet time in queue
Vehicle vicinity
300m
RSU vicinity
2.5km
35 ms
1.6km
IV. CONCLUSION AND FUTURE SCOPE
This paper has presented EDSR, which is part of a
complete system that we are designing for providing car
drivers and passengers, the freedom of access to the required
data while on the road. The proposed system exposes the use
of RSUs to reduce the load on vehicles and to reduce the
complexity of getting the required information. The evaluation
of EDSR confirmed its effectiveness when compared to recent
routing protocols for VANET. The future work will focus on
providing secure mechanisms for registering users to the
system of RSUs and designating them as proxies to Internet
service providers that provide data to these users.
Mr. Ch. Sudersan Raju received
Bachelor’s Degree in Electrical
and Electronics Engineering
from
SJMIT,
Chitradurga,
Karnataka and Master’s degree
in Digital Systems and Computer
Electronics
from
JNTU,
Anantapur. He is a life time
member of Indian Society for
Technical Education (ISTE).He
is also a life time member of
IMAPS. He is currently working
as Associate Professor with Department of Electronics and
Communication Engineering in BIT Institute of Technology,
Hindupur. His research interests include wireless networks
and Vehicular Ad Hoc and Sensor Networks.
V. REFERENCES
[1] Khaleel Marshad, Hasan Artail and Mario Gerla ―We Can Deliver
Messages to Far Vehicles” IEEE Transactions on Intelligent Transportation
Systems. Vol.13., no. 3, Sep 2012.
[2] Y. Ding, C. Wang, and L. Xiao, ―A static-node assisted adaptive routing
protocol in vehicular networks,‖ in Proc. VANET, New York, Sep. 2007,
pp. 59–68.
[3] C. Lochert, H. Hartenstein, J. Tian, H. Füÿler, D. Hermann, and
M. Mauve, ―A routing strategy for vehicular ad hoc networks in city
environments,‖ in Proc. IEEE Intell. Veh. Symp., Jun. 2003, pp. 156–161
[4] V. Namboodiri and L. Gao, ―Prediction-based routing for vehicular ad
hoc networks,‖ IEEE Trans. Veh. Technol., vol. 56, no. 4, pp. 2332–2345,
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