CSLI 5350G - Pervasive and Mobile Computing
Week 3 - Paper Presentation
“RPB-MD: Providing robust message dissemination for vehicular ad
hoc networks”
Name: Dinesh Bilimoria
Date: Oct 2nd, 2013
Research Paper
Bibliography:
Liu C., Chigan C., "RPB-MD: Providing robust
message dissemination for vehicular ad hoc
networks", Ad Hoc Networks, Volume 10, Issue 3,
May 2012, Pages 497-511
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Background
Relative Position Based Addressing Model
Vehicle on Highway
Dissemination Direction
Set of Vehicles on ZoR
Total Relative Distance
Range of Zone of Relevance (ZoR)
During the message dissemination session
, , each vehicle j with
satisfying
, should be in the intended receiver set
.
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Background
Directional Greedy Broadcast Routing (DGBR)
Vehicle A is assumed to be the
message source node, and it
transmits the message to its front
vehicles by its front directional
antenna.
Vehicle C, with the smallest Ti,
will be the best next
forwarder to rebroadcast the
message with its two directional
antennas. It will transit from
inactive state to active state to
act as the new message head.
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In A’s communication range, vehicles B
and C will receive this message at their
first time, and they will contend to
rebroadcast the message after their own
period Ti
In the case that the message head E
does not overhear any new
rebroadcast after T, the network is
considered to be disconnected and
vehicle E will rebroadcast the message
at an interval T’.
RPB-MD: Providing robust message dissemination for
vehicular ad hoc networks
Objective
The goal is to reliably and efficiently disseminate messages to the vehicles in
the zone-of-relevance using Relative Position Based Message
Dissemination (RPB-MB).

Proposal

Use only the forwarding state of message dissemination

Achieve robust message dissemination and reduce communication
overhead using Directional Greedy Broadcast Routing (DGBR)

Implement RPB-MB based on local traffic density, speed and the number of
neighbors. This can be achieved in real time by exchanging beacons among
neighbors

Proposed protocol to be adaptive to real vehicular traffic using;
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RPB-MD: Providing robust message dissemination for
vehicular ad hoc networks
Message Forwarding State

In the forwarding state, every node goes thru 3 states and enter one stage;
Active State:
Intermediate State:
Inactive State:
Failure Processing:
Node in this state is the Message Head
Node in this state are the Message Holders
Node do not receive or have dropped the Message
When ACK is not received
RPB-MD: Providing robust message dissemination for
vehicular ad hoc networks
Contributions
Guarantee high delivery ratio with acceptable latency and limited overhead
using RPB-MD
Improve the dissemination reliability by rebroadcasting message dynamically
using DGRB
Vehicular traffic density will significantly affect the network connectivity
Under varying traffic density, the message will be disseminated efficiently
RPB-MD can be extended to 2-D scenarios
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Assumptions
Vehicles can assume the relative distance between neighbors based on
GPS position
Two directional antennas with bandwidth of 180 degrees are equipped
All the vehicles can acquire local vehicle traffic density and average vehicle
velocity
Assume that all the vehicle nodes are synchronized
The vehicle communication range ie R is set to be uniform to calculate the
neighbor's waiting weight
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RPB-MD: Providing robust message dissemination for
vehicular ad hoc networks
Message Dissemination
From Message Head 1 to Message Head n, the message is disseminated by
DGBR which is based on relative distance and moving direction

= Weight of Relative Distance
= Ramp Function of Vehicle Velocity
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RPB-MD: Providing robust message dissemination for
vehicular ad hoc networks
Message Dissemination Scenarios
Scenario Case
Impact
Message holder (message head)
does not receive the implicit ACK
The old message head will rebroadcast the message again.
If the new message head is in range, then it will send an implicit ACK
Otherwise, the new message holders will contend to send the implicit ACK
If the message head comes upon
some fault to disseminate the
message.
The message holders, whose moving direction is the same as the
message dissemination direction, will resume another contention to
forward the message after certain time period t1
GPS measurements will have
certain amount of inaccuracy
depending on the environment and
systems
RPB-MD will not suffer the problem of transmission failures
due to location errors since it does not maintain neighbor tables.
Sensitivity analysis of packet
duplication
Can have one packet duplication in a scenario where Vehicle V1 has a
time period T1 and there exists another vehicle V2 with a time period such
that where
is the minimum time interval needed for packet
suppression.
Impact on Curving Road
Consider both routing in the road segment and routing in the intersection.
Both road distance and traffic condition must be considered. In future how
to select road segment reflecting dynamic road segment will
require further research.
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RPB-MD: Providing robust message dissemination for
vehicular ad hoc networks
Evidence

Time parameters are designed dynamically and adaptively according to the
message attributes and vehicular traffic density
Evaluation of Prototype

Simulation experiments are conducted using four protocols: epidemic routing
mechanism, GPSR, IVG and proposed RPB-MD protocol.

Metrics are used to compare performance, Data Delivery Ratio, Data
Overhead, Average Delay, Network Reachability

RPB-MD can steadily hold very high delivery ratio at different vehicle
densities

In epidemic routing, IVG and GPSR, there are more collisions than that of
RPB-MD

The data delivery ratio of epidemic routing, IVG and GPSR decreases faster
than that of RPB-MD when data sending rate increases.
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RPB-MD: Providing robust message dissemination for
vehicular ad hoc networks
Results
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RPB-MD: Providing robust message dissemination for
vehicular ad hoc networks
Shoulder of Giants

This research was build on previous car following model.
= Co-efficient of the Maximum Accelerations
= Safety Distance between Rear Bumper and Rear Bumper
This research also looked at other routing protocols;
(1) destination sequenced distance vector (DSDV) routing
(2) ad hoc on-demand distance vector (AODV) routing
Impact

Cited by 5 papers since 2012
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RPB-MD: Providing robust message dissemination for
vehicular ad hoc networks
Open problems

Investigate ways to design an advanced cross-layer between MAC and
routing layer to solve the problem of interference, scalability and connectivity
in VANET.

Focus on the issues of message storage in the ZoR within the message
lifetime.
Discussion points

What is RPB-MD ?

Relative Position Based Message Dissemination

In which state does the Message Holders carry information?

Intermediate State

Which routing protocol was used to reduce communication overhead ?

Directional Greedy Broadcast Routing (DGBR)
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