Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica, - - PowerPoint PPT Presentation

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Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica, Emmanuel Chaput, Andr-Luc Beylot University of Toulouse Institut de Recherche en Informatique de Toulouse IEEE 8 th International Conference on Mobile Ad-hoc and Sensor

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Physical Carrier Sense in Vehicular Ad-hoc Networks

University of Toulouse Institut de Recherche en Informatique de Toulouse IEEE 8th International Conference on Mobile Ad-hoc and Sensor Systems Valencia - 20 October 2011

Razvan Stanica, Emmanuel Chaput, André-Luc Beylot

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Physical Carrier Sense in Vehicular Ad-hoc Networks

 Safety Communication in Vehicular Networks  Particularities of the VANET Control Channel  The Importance of the Carrier Sense Range  Adaptive Carrier Sense Threshold

Razvan Stanica University of Toulouse IEEE MASS 2011

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Adaptive CS Safety V2V Carrier Sense Range

VANET objective: Building an accurate image of the exterior world  Cooperative Awareness Message (CAM)  Decentralised Environmental Notification (DEN)

Control Channel Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

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Safety V2V Control Channel Adaptive CS Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

 Intersection Collision Warning  Emergency Electronic Brake Lights  Approaching Emergency Vehicle  Lane Change Assistant  Left-Turn Collision Warning

Safety Applications

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Safety V2V

5.860 5.870 5.880 5.890 5.900 5.910 5.920 G5SC4 G5SC3 G5SC1 G5SC2 G5CC CH172 CH174 CH176 CH178 CH180 CH182 CH184 USA Spectrum Allocation Europe Spectrum Allocation  Service channels (SCH) – non-safety (usually IP-based) applications  Control channel (CCH) – safety applications

Control Channel Adaptive CS Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

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Safety V2V Control Channel

Safety beaconing

 A beacon expires if the next CAM is produced  No exposed terminals  Practically no internal contention on the CCH  MAC delay automatically considered in the expiration probability  Metric of interest: reception probability

Adaptive CS Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

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Safety V2V Control Channel

IEEE 802.11p on the CCH

Adaptive CS Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

100% broadcast communication No ACK message Collisions can not be detected BEB mechanism deactivated Always use the minimum value for CW

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Safety V2V Control Channel

Congestion Control

 Reduce Beaconing Frequency

Adaptive CS Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

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Safety V2V Control Channel

Congestion Control

 Reduce Beaconing Frequency  Increase Data Rate

Adaptive CS Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

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Safety V2V Control Channel

Congestion Control

 Reduce Beaconing Frequency  Increase Data Rate  Control Transmission Power

Adaptive CS Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

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Safety V2V Control Channel

Congestion Control

 Reduce Beaconing Frequency  Increase Data Rate  Control Transmission Power  Modify Back-off Mechanism

Adaptive CS Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

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Safety V2V Control Channel

Congestion Control

 Reduce Beaconing Frequency  Increase Data Rate  Control Transmission Power  Modify Back-off Mechanism  Adapt Carrier Sensing

Adaptive CS Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

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Safety V2V Carrier Sense Range Control Channel Adaptive CS Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Carrier Sense in IEEE 802.11

 MAC Layer – Network Allocation Vector

based on the RTS/CTS handshake
unusable on the broadcast CCH

 PLCP Layer – Clear Channel Assignment

header detection
energy detection

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Safety V2V Carrier Sense Range Control Channel Adaptive CS Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Carrier Sense Range

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Safety V2V Carrier Sense Range Control Channel Adaptive CS Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Carrier Sense Range Safety Range

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Safety V2V Carrier Sense Range Control Channel Adaptive CS Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Carrier Sense Range Safety Range Worst Case Scenario Pt CSt Pi CSi X= CSr/SFr SIR= Pt/Pi(X-1)θ

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Safety V2V Carrier Sense Range Control Channel Adaptive CS Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Carrier Sense Range Safety Range Transmission Power Control Pt CSt Pi - Pε CSi SIR

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Safety V2V Carrier Sense Range Control Channel Adaptive CS Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Carrier Sense Range Safety Range Carrier Sense Threshold Control Pt CSt Pi CSi - CSε SIR

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Safety V2V Carrier Sense Range Control Channel Adaptive CS Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Carrier Sense vs. Transmission Power

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Safety V2V Carrier Sense Range Control Channel Adaptive CS Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Carrier Sense Range Safety Range Why Not Use the Minimum Carrier Sense Threshold?

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Safety V2V Carrier Sense Range Control Channel Adaptive CS Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Carrier Sense Range = Competition for Channel Access Safety Range Why Not Use the Minimum Carrier Sense Threshold?

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Vehicular Density

 More neighbours – longer back-off  More neighbours – more expired beacons  More neighbours – more collisions

Control Channel Safety V2V Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Collision Capture Effect Capture Effect

Carrier Sense Range Adaptive CS

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Vehicular Density

 More neighbours – longer back-off  More neighbours – more expired beacons  More neighbours – more collisions

Control Channel Safety V2V Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Collision

Carrier Sense Range Adaptive CS

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Adaptive Carrier Sense Threshold

 Low CSt value under low density  High CSt value under high density  Beacon-based density estimation – λ  CSt= f(λ)

Adaptive CS Control Channel Safety V2V Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

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Simulation Study

 JiST/SWANS framework  Street Random Waypoint mobility model  Three different real maps from TIGER database  Medium and high vehicular density

Adaptive CS Control Channel Safety V2V Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

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Adaptive CS Control Channel Safety V2V Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Beaconing Reception Probability for different Densities and CS Thresholds

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Adaptive CS Control Channel Safety V2V Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Impact of the Carrier Sense Range

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Adaptive CS Control Channel Safety V2V Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Adaptive vs. Best Fixed CSt

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Adaptive CS Control Channel Safety V2V Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Different Optimal Values for CSt

Adaptive vs. Best Fixed CSt

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Adaptive CS Control Channel Safety V2V Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Vehicular Density Adaptive Mechanism CSt= -95 dBm CSt= -85 dBm CSt= -75 dBm 25 veh/lane/km 91.02% 86.42% 89.88% 88.64% 35 veh/lane/km 86.12% 78.38% 84.27% 81.81% 45 veh/lane/km 81.41% 69.76% 76.32% 80.20%

Adaptive vs. Best Fixed CSt

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Adaptive CS Control Channel Safety V2V Carrier Sense Range Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

Distribution of CSt for the Adaptive Mechanism

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Conclusion

Physical Carrier Sense in Vehicular Ad-hoc Networks Razvan Stanica University of Toulouse IEEE MASS 2011

 The properties of the CCH need to be taken into account when studying V2V communication  The carrier sense mechanism represents the basis for CSMA/CA channel access techniques and should receive more attention  Carrier sense threshold control is more powerful than transmission power control on the VANET CCH  A simple adaptive mechanism can bring important performance improvement in IEEE 802.11p networks

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Physical Carrier Sense in Vehicular Ad-hoc Networks

University of Toulouse Institut de Recherche en Informatique de Toulouse IEEE 8th International Conference on Mobile Ad-hoc and Sensor Systems Valencia - 20 October 2011