improving reliability of platooning control messages … · improving reliability of platooning...

Improving Reliability of Platooning Control Messages Using Radio and Visible Light Hybrid Communication

Susumu Ishihara (Shizuoka University)

Vince Rabsatt, Mario Gerla (UCLA)

Platooning

• Autonomous Platooningor Cooperative Adaptive Cruise Control (CACC) • Improves the traffic flow• Reduces the fuel consumption• Improves the drivers’ safety

2

To the direct follower

Camera/RADAR/

LIDAR,etc.

Leader to followers

Sartre (EU)-2012

http://www.nedo.go.jp/activities/FK_00023.html

Energy ITS (Japan) -2013

1Truck and 3 cars Demo 6m gap @90km/h 5.9GHz DSRC 40Hz Message

4 Truck-Demo 4.7m gap @80km/h 5.8GHz DSRC + IR 50Hz Message

http://www.sartre-project.eu/en/about/news/Sidor/roadtrains_video.aspx

Recent Platooning Projects

3

http://www.nedo.go.jp/activities/FK_00023.html

http://www.sartre-project.eu/en/about/news/Sidor/roadtrains_video.aspx

4

Adaptive Cruise Control (ACC) Uses information of the preceding car

Cooperative Adaptive Cruise Control (CACC) Uses information of the preceding car and the leader car

Simulation of Platooning on Scenargie1, a discrete event simulator(Same scenario provided with plexe2, a platooning extension for Veins)

[1] Product of Space-Time Engineering, https://www.spacetime-eng.com/[2] Michele Segata, Stefan Joerer, Bastian Bloessl, Christoph Sommer, Falko Dressler and Renato Lo Cigno,

"PLEXE: A Platooning Extension for Veins," IEEE VNC 2014

http://www.ccs-labs.org/~segata/

http://www.ccs-labs.org/~joerer/

http://www.ccs-labs.org/~bloessl/

http://www.ccs-labs.org/~sommer/

http://www.ccs-labs.org/~dressler/

http://disi.unitn.it/locigno/

Many issues for realizing platooning

• Control Theory • Vehicle Dynamics • Communications • Sensing • Image Processing • Localization • Traffic Engineering • etc.

5

Communication Issues• Radio Communication Capacity

• If many vehicles are on the road, radio communication capacity may be exhausted.• Communication Rate Control• Transmission Power Control

• Security • What if attackers make a radio signal jam? • What if a malicious vehicle pretends other cars?• What if a malicious vehicle generates wrong update

information?

6

Fragile Radio Communication

• If there is a malicious machine that sends a jam signal, messages transmission from the leader vehicle can be easily damaged.• We can easily make jamming machine using

software radio platforms, such as GNU Radio/USRP, WARP, etc.

• This is a potential problem of CACC based on radio communications.

Slow down

7What if we use Visible Light Communication?

Contributions of this paper• We proposed an RF and VLC hybrid communication

protocol for platooning control messages for reliable message delivery under RF jamming attacks.

• We developed a simulation model supporting both radio communication and VLC on Scenargie

• The proposed protocol works effectively to decrease the end-to-end delay of the leader messages and improve the message delivery ratio under jamming attack

8

Simulation: Effect of jamming attack

Jam part is 802.11p Compliant PLCP Preamble + PLCP Header + Part of MAC Header

Jam

64us 10us

10~400us

Jam Jam Jam Jam Jam

Jam Jam

[Punal2015] Periodic Jammer

Our simulation

on Scenargie

10~400us Jam

CBR Broadcast on IEEE 802.11p 6Mbps

(Payload 300bytes / 10Hz)

J

S R

ds dr

dsr: 10m and 50m

Jammer

Tx Power 20dBm

Tx Power 20dBm

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Simulation Results: Packet Delivery Ratio under Jamming Attack

Dist(S, R) = 10m

10us 120us 150us 200usIdle duration of Jam signal 122us

75m65m 65m

• If the idle duration is long, the sender can find the channel idle state longerthan DIFS (=58us) + Backoff. Thus, the sender can send a frame.

• But if the distance between the sender and the receiver is long,due to the bad SINR, the receiver cannot decode the frame.

15m75m

Dist(S, R) = 50m

Color = Packet Delivery Ratio

Dist(Source, Jammer)

Dist(Receiver, Jammer)

15m75m

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Using Visible Light Communication (VLC)

• Uses LED lights for communication between adjacent vehicles • Cheap – Low Additional Equipment Cost

• Every vehicle has tail lights and head lights.• Difficult to attack - Highly directional

• VLC jammer has to be in the field of view of the receiver device to attack• Jamming light has to be concentrated to the receiver device

• But, long distance communication over multiple vehicles is difficult • Multi-hop communication is needed – Long message delivery delay

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Shortening message delivery delay

• Hybrid of RF Communication and VLC

• RF • Wide range – Propagates beyond multiple vehicles• Vulnerable to Jamming

• VLC • Short range – Hop by hop communication• Strong against Jamming

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Radio and VLC Hybrid Message Delivery for Platooning

RF Broadcast

LeaderVLC• Leader sends a message via both VLC and RF interfaces

• If a vehicle receives a new message from either of VLC and RF interfaces, it forwards the message via VLC (and RF).

• Only If a condition is satisfied, the vehicle forwards the message via both VLC and RF to avoid RF channel congestion.

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RF Broadcast

Condition for forwarding a message via RF

• Candidates of conditions • Distance from the previous RF hop vehicle• Elapsed time from the transmission by the leader• Number of hops from the leader• SINR of the signal from previous radio-hop vehicle• etc.

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In this simulation: “If a new leader message arrives from VLC, forward it via RF and VLC.”

Intuition: If an RF message does not arrive, the leader may be suffering jamming attack and cannot send the message. Thus other vehicles have not received the message. …. RF broadcast is needed.

Simulation Model

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30°

RF IEEE802.11p Interface (6Mbps, AC_VI) Omni antenna: 5.9GHz

VLC interfaces with a directional antenna model Comm. range: 5m (the same as the inter vehicular distance) MAC: ALOHA Bitrate: 50kbps (assuming cheap off-the-shelf devices)

Note: This model is just an abstract model of VLC. It does not simulate realistic visible light propagation.

5m

We implemented multiple interfaces with different antenna models (pos. and direction) and an application model using these interfaces on Scenargie

Simulation Scenario

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500m10m

10m

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t=010 vehicles

10m

…

Periodic Jammer

…

5m

12.5m

17.0m/s

• Jammer: Periodic Jammer [64us JAM and 10us idle period] • Platoon of 10 vehicles: 1 platoon scenario and 4 x 4 platoon scenario • Leader sends 200byte message to the members every 0.1sec. • Tx power of All vehicles and Jammer: 20dBm • Propagation: Free Space, Fading: Nakagami

Compared Strategies

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Use VLC Use RF Forwarding

Forward only when receiving a new

message via VLC

Only Direct RF (FFF) F F F

RF Forward (FTF) F T F

VLC + No RF Fwd. (TFF) T F F

VLC + unconditional RF Fwd. (TTF) T T F

VLC + conditional RF Fwd. (TTT) T T T

End-to-End delay at 5th car / 1platoon

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Fig. 7. Time series variation of end to end delay of leader messages(1 platoon)

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Fig. 8. Time series variation of end to end delay of leader messages (4× 4platoons)

Longblind period (4sec.)

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VLC’s multi-hop delay

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Long delay period is shortened

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No positive effect of conditional RF Fwd.

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5th car/1platoon 10th car/1platoon 5th car/ 4 x 4 platoons

10th car/ 4 x 4 platoons

Other cars / Many platoons cases

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Fig. 9. Packet delivery ratio

By forwarding beacon messages using RF at each membervehicle (FTF, (a2) (b2)), the number of beacon messagesreceived by the members increases, but the end-to-end delayis long and the number of received messages during a fewseconds when the vehicle at the closest point of the jammer.If the leader vehicle cannot send any beacon message due tothe busy state of the RF channel caused by the jammer, thefollower vehicle cannot forward the beacon message, thus thepacket received by the member vehicles is still small.

By using only VLC for forwarding beacon message ofthe leader vehicle (TFF (a3), (b3)), the reachability of thebeacon messages improves. It can be confirmed clearly inFig. 9. However, the end-to-end delay is long for long duration,especially when the position of the vehicle in the platoon isbackward and the number of platoons is large.

Using both RF and VLC for forwarding beacon messages ofthe leader (TTF, (a4), (b4)), the duration of end-to-end delayis shortened. When using the forward via RF only if VLS isfaster strategy (TTT, (a5) ,(b5)), due to the smaller number ofRF forwarding messages caused by the strategy, the end-to-enddelay is longer than TTF case when the number of platoon is1. The idea behind the strategy is to prevent congestion causedby the messages forwarded by member vehicles under RFjamming attacks. Thus, the effect of the strategy is expected topresent when the number of vehicles/platoons is large. Whenthe number of the platoon is 16 (Fig. 8), the difference betweencases of TTF and TTT is very small. We cannot see neithernegative impact nor positive impact of the forward via RF onlyif VLS is faster strategy in this case.

Note that in the simulation of in this paper, we assumedvery slow VLC link (50kbps) that will be realized by today’soff-the-shelf LED and photo-diode devices. The delay factor ofthe system strongly is dependent on the link speed. To balancethe requirement of the end-to-end delay that the platooningalgorithm requires and the link speed and technology used inVLC should be carefully chosen.

VI. CONCLUSION

We proposed a radio and visible light hybrid protocolfor improving the reliability of control message used in au-tonomous platooning systems and evaluated the effectivenessof the strategies through simulations. The simulation resultsshow that by using both radio communication and multi-hop visible-light communication, the reliability of platooningcontrol messages from the leader vehicle can be significantlyimproved and the end-to-end delay can be shortened. Futurework will be more simulation with realistic scenarios thatinclude the real platoon mobility and precise VLC commu-nication model including the interference of VLC signals,especially in congested and/or curved lanes.

ACKNOWLEDGMENT

This work is supported by KAKENHI 15H02689.

5th car

10th car

1 platoon

# of new messages delivered in 1sec.

FFF

FTF (RF Fwd.)

TTF TTT

TFF

with VLC

Why packet delivery ratio < 1 with VLC?

Leader Member

RF

VLCGap

Conclusion• We proposed an RF and VLC hybrid

communication protocol for platooning control messages for reliable message delivery under RF jamming attacks.

• Findings • Long blind under a jamming attack only with RF.• RF + VLC Hybrid communication can better message

delivery ratio and short delay

• Future work • Effect of different communication speed of VLC• Effect of RF jamming on the dynamics of platoons• VLC jamming attack

21

Thank you

improving reliability of platooning control messages … · improving reliability of platooning...

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