This document presents an overview and comparison of three hybrid adaptive beaconing schemes proposed for vehicular ad hoc networks (VANETs). The schemes aim to optimize beacon dissemination by adjusting transmission power, data rate, and/or contention window size based on factors like vehicle density, channel load, and speed. The first scheme jointly adapts power and contention window size using an enhanced distributed channel access mechanism. The second scheme considers power, contention window, and rate, adjusting them according to measured congestion level. The third scheme optimizes reception probability by adjusting power and rate based on vehicle speed, acceleration, channel load, and other parameters. The schemes are contrasted based on their classification, performance criteria, control parameters,

1. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
Adaptive Beaconing Schemes in VANETs:
Hybrid Approach
SYED HASSAN AHMED, SAFDAR HUSSAIN BOUK, AND DONGKYUN KIM
3/9/2015 1

2. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
Outline
• Introduction
• Beaconing
• Hybrid Beaconing Schemes Overview
• Comparison
• Conclusion and Future Work
3/9/2015 2

3. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
Introduction
Intelligent Transportation System (ITS)
◦ Need of today due to exponential growth in number of
Vehicles around the globe.
◦ ITS = Applications + Technologies + Communication
Infrastructure
◦ Provides:
◦ Mobility and traffic management,
◦ Driver and passengers’ Safety and Comfort,
◦ Travel efficiency  Time and Energy Saving,
◦ Information availability on the go,
◦ etc.
3/9/2015 3

4. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
Introduction
Vehicular Ad hoc NETwork (VANET)
◦ One of the promising step towards the future ITS.
◦ Vehicles with communication capability.
◦ Vehicle to Vehicle (V2V) communication.
◦ Vehicle to Infrastructure (Road Side Unit) (V2I)
Communication.
3/9/2015 4

5. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
Introduction
Vehicular Ad hoc NETwork (VANET)
◦ Characteristics:
◦ Dynamic topology (High Mobility).
◦ Unpredictable network density.
◦ Delay bound communication.
◦ Intermittent connectivity and link lifetime.
◦ Safety and Non-Safety applications.
◦ Large data requirements.
◦ Delay constraints, etc.
◦ With/Without infrastructure support.
◦ Data ranges from short messages to large video contents
3/9/2015 5

6. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
Introduction
Vehicular Ad hoc NETwork (VANET) (Applications)
3/9/2015 6
Safety-related applications
• Assistance
• Navigation
• Cooperative collision avoidance
• Lane-changing
• Information
• Speed limit
• Work zone info
• Warning
• Post-crash
• Obstacle
• Road condition warnings
Non Safety-related applications
(Comfort-related)
• Weather information
• Instant messaging
• Online games
• Internet access
• Advertisements
Intersection
Collision Warning
Work Zone
Warning
Rollover WarningEmergency Vehicle
Approaching Warning
Lane Change
Warning
Co-operative
Collision Warning

7. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
3/9/2015 7
Beaconing
o Information sharing through short messages (Beacons) among vehicles,
called Beaconing.
o Freshness and Accuracy of information  Frequency/Interval of Beacons.
o Proximity area of Network Awareness  Transmission Power of Beacons.
Information
Accuracy/Freshness
Beacon
Interval SmallLarge
Beaconing Schemes for VANETs
Fixed Rate Adaptive
Rate / Frequency
Trans. (Tx) Power
Contention Window
Hybrid
+
Network/Channel characteristics:
• Node Density
• Packet Drop Rate
• Distance between neighbors
• ….. etc.

8. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
3/9/2015 8
Hybrid Beaconing Schemes
1. Joint Power and CW Size [D.B. Rawat et al.]
◦ Uses Enhanced Distributed Channel Access
(EDCA) mechanism of 802.11e to control
Transmission Power.
◦ Provides QoS by defining multiple Access
Categories [ACs] at MAC.
◦ First computes Range (R) using vehicular traffic
characteristics
◦ Map R in “Range vs Power” loop-up table.
◦ The CW size is adaptive adjusted with access priority
of the critical message, collision rate and 2.
D. B. Rawat et al., “Enhancing VANET Performance by Joint Adaptation of Transmission Power and Contention Window Size,” IEEE Transactions on Parallel
and Distributed Systems, vol.22, no.9, Sep. 2011, pp.1528–1535.
Length of
Road Segment
Ratio of vehicle density:
Actual No. of Vehicles
Total No. of Vehicles
Traffic Flow
Constant

9. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
3/9/2015 9
Hybrid Beaconing Schemes
2. Power, CW, and Rate [D. Puthal et al.]
• Parameters: Data Rate, Neighborhood Density (N), Current Queue Level (QL), and
Channel Usage (CU) Time.
• Congestion Level (CD)
• Transmission Power and Transmission Rate
• Adoption is based on the measured CD.
D. Puthal et al., “Cross-layer architecture for congestion control in Vehicular Ad-hoc Networks,” International Conference on Connected Vehicles and Expo (ICCVE), 2013,
Dec. 2013,pp.887–892.
No. of QueuesAccess Category (AC)
Number
Arbitration Inter-Frame Space Number
TABLE I. ACCESS CATEGORIES WITH MIN., MAX. CW AND AIFSN
Congestion Level Value of CD CW Adaption
Full CD > 90 Block comm. for all ACs except AC3
High 70 < CD ≤ 90 CW of all ACs except AC3CW(ACi)=CW(ACi)*1.5
Medium 30 < CD ≤ 70 CW(ACi)=min(CW(ACi),CW(ACi)MAX)
Ideal CD ≤ 30 All ACs CW(ACi)=CW(ACi)MIN

10. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
3/9/2015 10
Hybrid Beaconing Schemes
3. Power and Rate [Tessa Tielert et al.]
o Parameters: Speed of Vehicle (v), Max. acceleration
(a), Speed difference to its neighbors (), System
Latency (ts), and Driver’s reaction time (tr). Packet
Reception Probability (p) between successive lost
packets, Channel Load (l), etc.
o Target Distance: (To optimize reception performance)
T. Tielert et al., “Joint power/rate congestion control optimizing packet reception in vehicle safety communications,” In Proceeding of the tenth ACM international
workshop on Vehicular inter-networking, systems, and applications (VANET ’13), 25–28 June 2013, pp.51–60.
max
Congestion
Control Start
Congestion
Control Active
?
estimate l
l < l max
?
Pt < f (dt , lmax)
?
r < rmax
?
increase Pt
increase r
r > rmin
?
decrease Pt
decrease r
Yes
No
Yes
Yes
No
No
No
Yes
Yes
Congestion
Control Stop
Case 1: when vehicle sends emergency
beacon message to its neighbors
that are within the close proximity.
Case 2: when speed difference between
vehicle and its neighbors is large.

11. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
3/9/2015 11
Comparison

12. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
o A comprehensive study of state of the art hybrid adaptive
beaconing schemes proposed for VANETs.
o These schemes optimize the combination of beacon power,
rate and/or CW.
o All schemes are contrasted using the following parameters:
o Classification
o Performance Criteria
o Control Parameters
o Control Method
3/9/2015 12
Conclusion

13. KYUNGPOOK
NATIONAL UNIVERSITY, Daegu, Korea.
MoNet Laboratory
www.monet.knu.ac.kr
Thanks
hassan@knu.ac.kr