This slide was presented in the conference of DICOMO 2014 in Japan.

1. 1
Inter-Contact Time Study for MANETs
with Random Walk Mobility
Juntao Gao1
, Xiaohong Jiang2
1
Nara Institute of Science and Technology
2
Future University Hakodate
July 10, 2014

2. 2
Tokyo Ring Roads

3. 3
Tokyo Ring Roads
Vehicles rely on mobility and physical contacts to
communicate (e.g. spreading safety messages)

4. 4
Inter-Contact Time (ICT)
1. Inter-contact time (ICT): time interval between two
consecutive contacts of a pair of vehicles.
2. ICT significantly affects throughput and packet delay, and
thus serves as a fundamental metric to be studied.
ICT1
ICT2

5. 5
2. No accurate analytical results on inter-contact times in
MANETs.
Limitations of available works on ICT
1. Only empirical results (via simulation and real trace) and
analytical estimation results (without error analysis).
This hinders the performance evaluation and protocol design
in MANETs!
Inter-Contact Times (ICT)

6. 6
Outline
•System assumptions (random walk
mobility, preliminary definitions)
•Inter-contact time modeling
•Inter-contact time evaluation

7. Random Walk Mobility
Time is slotted and road is discretized into n sites.
p: counterclockwise move probability
q: clockwise move probability r: r=1-p-q
7

8. 8
Definitions
Node contact: If d(t) = 0, we say X1 and X2 contact each
other at time slot t.
Distance d(t): the number of sites vehicle
X1 has to travel clock wise to reach another
vehicle X2 at time slot t.
Inter-contact time:
is the time slots between two consecutive contacts of
X1 and X2

9. 9
Outline
•System assumptions (random walk
mobility, preliminary definitions)
•Inter-contact time modeling
•Inter-contact time evaluation

10. 10
ICT Modeling
Step 1: Analyze the distribution of the initial distance between
the two vehicles just after they lose contact
Step 2: Model how the distance between them evolves with
time slots until they contact again

11. 11
Initial distance could only be 1, 2, n-2 and n-1.
Step 1: distribution of the initial distance
Probability of initial distance being 1.
ICT Modeling

12. 12
Step 2: distance evolvement
ICT Modeling

13. 13
Step 2: distance evolvement
ICT Modeling

14. 14
Step 2: distance evolvement
ICT Modeling

15. 15
Step 2: distance evolvement
ICT Modeling

16. 16
Step 2: distance evolvement
ICT Modeling

17. 17
ICT Analysis
Transition matrix

18. 18
ICT Analysis
Transition matrix

19. 19
ICT Analysis
Accurate analytical results on inter-contact times

20. 20
Outline
•System assumptions (random walk
mobility, preliminary definitions)
•Inter-contact time modeling
•Inter-contact time evaluation

21. 21
ICT Evaluation
Mean value vs. mobility parameters

22. 22
ICT Evaluation
Mean value vs. numberof networksites n

23. 23
We proposed theoretical models to derive accurate
analytical results on inter-contact times.
Conclusion