This thesis evaluates the Variable Control Channel Interval MAC (VCI MAC) protocol for supporting emergency voice over IP (VoIP) applications in vehicular ad-hoc networks. The document outlines the motivation, goals, standard IEEE 1609.4 MAC protocol, VCI MAC protocol, simulation implementation, performance analysis, proposed enhancements, and conclusions. Key findings are that VCI MAC adapts well based on varying network conditions, improves MAC throughput and VoIP performance compared to the standard MAC, but has limitations for multi-hop scenarios. Channel negotiation is proposed to provide additional feedback capability.

1. Evaluation of Variable Control Channel
Interval With Multichannel Coordination MAC
Protocol for Vehicular Ad-hoc Networks
Final Thesis Presentation
Communication Networks Department
Mahalakshmi Tarikere Devendrappa [51405]
Supervisor: MSc. Parag Sewalkar
Responsible Professor: Prof. Jochen Seitz
2016/3/23 www.tu-ilmenau.de/ei_ms_cspPage 1

2. Agenda
• Motivation
• Goals
• Standard IEEE 1609.4 MAC
• VCI MAC
• Implementation
• Simulation and Performance Analysis
• Proposed Enhancement
• Conclusion
• Future Work
Page 2

3. Motivation
• WAVE Standards cater both safety, non-safety
applications
• Efficient management of control and service
channels
• Flexible Channel Intervals supported in VCIMAC [2]
• Evaluate VCIMAC for emergency VoIP application
scenario in VANETs.
Page 3

4. Goals
• Study on DSRC/WAVE, Multichannel coordination
schemes, VCI MAC, VoIP performance metrics
• Implementation of VCI MAC in OMNeT++, Veins
and SUMO
• Evaluation of Standard MAC 1609.4 and VCIMAC
on Emergency VoIP application
• Proposition of enhancements to VCI MAC as per the
defined scenario
Page 4

5. DSRC and WAVE
Page 5
(a) WAVE Protocol Stack [1]
(b) DSRC Spectrum [1]

6. SCH Advertised Communication
Page 6
WSA: WAVE Service Advertisement
WME: WAVE Management Entity
MLME: MAC Layer Management Entity

7. IEEE 1609.4 Multi-channel MAC
Page 7
Link Layer
Multi-channel MAC Layer
Channel routing
CCH (Safety, Service
Advertisements)
SCH (Safety, IP Data)
Internal contention Internal contention
Medium contention
BK BE VI VO BK BE VI VO
CCH-Control CH
SCH-Service CH
BK-Background
BE-Best Effort
VI-Video
VO-Voice
Physical Layer

8. Variable Control Channel Interval MAC
Page 8
Synchronization interval: T = 100ms
Data exchange
CCH
SCH
CCH
SCH
Data exchange
Standard
1609.4 MAC
VCI MAC
Tcch = 50ms
Tsch
Safety, Control
Safety
Interval
Tcch
Tsch = 50ms
WSA
Interval

9. Optimized Channel Intervals
Page 9
cch
sa
B
fN
T 
dataschsuccol
suc
col
idle
suc
satotalschsuccol
suc
col
idle
suc
wsa
TNTT
p
p
T
p
TTNTT
p
p
T
p
T




















1
1
wsasacch TTT  cchtotalsch TTT 
where, f – Frequency of safety message Tx
N – Number of nodes in the Tx range
psuc – Probability of successful WSA Tx

10. Service Channel Reservations
Page 10
WSA: WAVE Service Advertisement
RFS: Request For Service
ACK: Acknowledgement

11. Vehicle Node
Page 11
UDP Application
UDP
Network Layer
Wave Management
Entity
Link Layer
VCI MAC
Physical Layer
VCI Manager
VCI NIC

12. Performance Parameters
• VoIP Frame Delay
• VoIP Frame Loss
• VoIP Jitter
• VoIP Mean Opinion Score
• VoIP Normalized Throughput
• MAC Throughput
Page 12

13. Simulation Parameters
Parameter Value
Simulation Test Area 8000 m2
Maximum Speed 100 kmph (27.78 m/s)
Maximum Transmit Power 20 mW
Sensitivity - 89dBm
Analogue Model Simple Path loss Model
Transmission Range 675 m
Safety Message Frequency 2
Slot Time 20 μs
SIFS 10 μs
DIFS 50 μs
WSA Length 44 Bytes
ACK Length 38 Bytes
MAC Header Length 60 Bytes
Page 13

14. Scenarios
• Variation of Safety, WSA, Control and Service
channel intervals
• Single VoIP call performance
- Speed
- Distance
• Multiple VoIP applications on same SCH
- Number of applications
- Payload Size
- Number of nodes in range
Page 14

15. Variation in Channel Intervals
Page 15
0
0.02
0.04
0.06
0.08
0.1
0 20 40 60 80 100
Interval(s)
Number of Nodes
Variation with Number of nodes
CCH Interval
SA Interval
WSA Interval
SCH Interval
0
0.02
0.04
0.06
0.08
0.1
1 2 3 4
Interval(s)
Number of SCH in use
Variation with Number of SCH
CCH interval
SA Interval
WSA interval
SCH Interval

16. Page 16
0
0.02
0.04
0.06
0.08
0.1
0 5 10 15 20 25 30
Interval(s)
Data rate (Mbps)
Variation with Data rate
CCH interval
SA Interval
WSA interval
SCH Interval
0
0.02
0.04
0.06
0.08
0.1
0 500 1000 1500 2000
Interval(s)
Data Payload (Bytes)
Variation with Data Payload Size
CCH interval
WSA interval
SA interval
SCH interval

17. Multiple VoIP Applications – Single SCH
Page 17
SCH 174
VoIP 1 VoIP 2
MAC/VCIMAC
PHY
…
PHY
VoIP 1 VoIP 2
…
MAC/VCIMAC
TxRx

18. Multiple VoIP Applications – Single SCH
Page 18
0
4000
8000
12000
16000
20000
0 5 10 15 20 25 30 35
FrameDelayinms
Number of VoIP calls
Variation of Frame Delay
MAC
VCIMAC
Threshold
0
20
40
60
80
100
0 5 10 15 20 25 30 35
FrameLoss%
Number of VoIP calls
Variation of Frame Loss
MAC
VCIMAC
Threshold
Payload length = 160 Bytes
Data rate = 3Mbps

19. Page 19
0
500
1000
1500
0 5 10 15 20 25 30 35
Jitterinms
Number of VoIP calls
Variation of Jitter
MAC
VCIMAC
0
1
2
3
4
5
0 5 10 15 20 25 30 35
MeanOpinionScore
Number of VoIP calls
Variation of MOS
MAC
VCIMAC
Threshold

20. Page 20
0
0.2
0.4
0.6
0.8
1
0 5 10 15 20 25 30 35
NormalizedThroughput
Number of VoIP calls
Variation in Normalized Throughput
MAC
VCIMAC
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15 20 25 30 35
MACDataThroughputMbps
Number of VoIP calls
Variation of MAC Tx Throughput
MAC
VCIMAC

21. Observations
+ Adaptive to number of nodes inside the transmission
range, payload size, number of SCHs used
+ Increased Throughput on SCHs
─ Supports only single-hop scenarios
─ Smaller data payload increases CCH interval
─ Applications lasting for longer duration, except in first
sync Interval, WSA interval time in subsequent sync
intervals is wasted.
Page 21

22. Proposed Channel Negotiation
Page 22
Provider User Provider User Provider User
Data Exchange
Data Exchange
I. Service Accept II. Reject Channel Busy III. Reject Not Specified

23. Channel Negotiation - Analysis
Page
23
WSA
ACK
WSA
ACK
Successful WSA Tx Successful 2nd WSA Tx
Contention
Z
Z
Z
Z
Contention
Total SCH Reservation Period
SIFS DIFS SIFS DIFS
PeriodnReservatioSCHVCIMAC2PeriodnReservatioSCH 

24. Conclusion
• Simulator for VCIMAC and WAVE Management
Layer implemented
• Increased MAC Throughput in VCIMAC improves
VoIP performance and is adaptive
• Channel Negotiation gives additional feedback
capability but increases reservation time
Future Work
• Multi hop scenario support
• Multiple VoIP applications on different SCHs
• Mathematical Model for Channel Negotiation
Page 24

25. References
[1] IEEE Trial-Use Standard for Wireless Access in Vehicular Environments (WAVE) - Networking
Services. In: IEEE Std 1609.3-2007 (2007), April, S. 1–99.
http://dx.doi.org/10.1109/IEEESTD.2007.353212. – DOI 10.1109/IEEESTD.2007.353212
[2] Wang, Qing ; Leng, Supeng ; Fu, Huirong ; Zhang, Yan: An IEEE 802.11 p-based multichannel
MAC scheme with channel coordination for vehicular ad hoc networks. In: Intelligent Transportation
Systems, IEEE Transactions on 13 (2012), Nr. 2, S. 449–458.
[3] Xie, Xu ; Huang, Benxiong ; Yang, Shaoshi ; Lv, Tiejun: Adaptive multi-channel MAC protocol for
dense VANET with directional antennas. In: Consumer Communications and Networking Conference,
2009. CCNC 2009. 6th IEEE IEEE, 2009, S. 1–5
Page 25

26. Questions
Page 26

27. Thank You
Page 27

28. Variation with Speed
Page 28

29. Variation with Payload size
Page 29

30. Number of nodes in range
Page 30

31. WSA Transmission - Markov chain model
Page 31
{s(t), b(t)}
s(t): back-off state
b(t): back-off window size
p: Probability of Collision
t: Probability of Successful
Tx of WSA
W0: CW for 0th Stage
Wi: CW for ith Stage