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Novel Relay Scheme Based on
Traffic Type in Vehicular Networks
2008 International Conference on Intelligent Computation
Technology and Automation
Zuoqiao Shi, Fuqiang Liu, Shangzhi Xu
Speaker: Wu Wei-Cheng
Date: 2009/04/13
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Outline
1.
2.
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3.
4.
Introduction
Novel relay scheme based on traffic type
Primary and candidate relays’ cooperative
work scheme (PCC) for emergency message
Relay cluster scheme (RCS) for non-realtime traffic
Simulation and Results Discussion
Conclusions
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1. Introduction
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
Two novel relay schemes based on traffic type for
vehicle to vehicle data transmission.
Two type traffic:
(1)The emergency information and safety
messages such as serious accidents, traffic jams,
intersection statement and so on, which is strict
with low latency, own the highest priority.
(2)Non-real-time traffic, such as rich-content news,
service information, entertainment news and so on,
which aims to gain low bit error ratio and high
throughput at the receiver, owns lowest priority.
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2. Novel relay scheme based on
traffic type
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Each vehicle is able to obtain its own
geographical location, relative position, speed
and direction. This information is exchanged over
vehicular networks periodically.
Each vehicle is equipped with several wireless
transceivers. And wireless transmission range is
set to be 200 meters. 802.11 DCF technology is
used to control channel-access.
Each vehicle owns a unique ID to distinguish
himself with other vehicles.
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2.1 Primary and candidate relays’
cooperative work scheme (PCC) for
emergency message
1.
There need not the process of contentionresolve mentioned in section II and cause little
delay.
2.
This scheme can forward message as far as
possible.
3.
PID: primary relay vehicle.
CID: candidate relay vehicle.
4.
The two relays’ work pattern is cooperative
but not independent.
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2.1 Primary and candidate relays’
cooperative work scheme (PCC) for
emergency message
NNR: no-need-retransmit
NTR: need-to-retransmit
τ: quality of channel,
distance and speed.
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2.1 Primary and candidate relays’
cooperative work scheme (PCC) for
emergency message
The maximum delay for primary
relay to completely forward message in defined as:
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2.2 Relay cluster scheme (RCS) for nonreal-time traffic
1.
2.
3.
4.
The speed of the vehicles should be the same
as or similar to the destination’s.
Small distance between the selected relay
vehicles is much more preferred.
There should be no hidden nodes between two
vehicles in order to eliminate the other
vehicle’s interference.
Enough storage capability, powerful
computational ability.
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2.2 Relay cluster scheme (RCS) for nonreal-time traffic

Here we define 1 as the condition of existing
error and 0 as the situation of no error in the
report.
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2.2 Relay cluster scheme (RCS) for nonreal-time traffic
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In the case that all three vehicles receive correct
signal (main report:000), cluster head inform the
two members and itself to retransmit the signal
to the destination vehicle together.
(main report: 001, 010, 100), cluster head tell
the error report’s owner to discard the signal and
the other two forward the signal to the
destination with no delay.
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2.2 Relay cluster scheme (RCS) for nonreal-time traffic
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(main report: 110, 011, 101)
case1: cluster head’s data contains error. Hence
it sends a message to the cluster member which
receives the right data and letting it transmit the
data to the cluster head, then the two retransmit
the signal to the destination.
case2: cluster head’s data contains no error.
The cluster head choose one of the cluster
members and transmits data to it. After that,
they retransmit data to destination.
(main report:111), the cluster head let the
source vehicle retransmit the wrong sequence.
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3. Simulation and Results Discussion
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3. Simulation and Results Discussion
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3. Simulation and Results Discussion
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3. Simulation and Results Discussion
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3. Simulation and Results Discussion
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4. Conclusions
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The PCC scheme outperforms better, and can
obviously decrease transmission delay when
obtain the similar breakage times.
The RCS scheme can highly decreases the ber
and increases the throughput of the vehicular
system.
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