CIGDP

1
CIGDP a protocol for generation dissemination
of traffic information in Vehicular Ad-hoc
Networks
Computer Science2005, Technical University of
Sofia

• Mitko Shopov
• On October 1, 2005

2
VANET Unique Characteristics

• High mobility that leads to dynamic, rapidly
  changing topology
• Regular movement, restricted by both road
  topologies and traffic rules
• Communication locality, limited to vehicles
  geographically close to each other
• Partitioned
• Vehicles are usually aware of their position and
  spatial environment through the use of GPS and
  pre-stored digital maps
• Vehicles have sufficient power, computing and
  storage capacity

3
New proposed approach Messages for traffic
events will be generated and disseminated by the
vehicles in the opposite direction
Blue cars ? Participants in traffic event
Red car ? Generate and disseminate the message
(marked ACTIVE)
Green cars ? Store message (marked PASSIVE). Can
become ACTIVE
4
Message structure

• Current location of the vehicle
• Time of registration
• Location of event (road segment)
• Direction
• Status (active or passive)
• Code of event (jam, etc.)
• Time-to-Live
• Some other information

5
Time-to-Live Field

• TTL determine how long to disseminate the message
• It is decremented on every crossroad
• More when crossroad is with equal streets
• Less on crossroads with trunk and secondary
  streets

6
Status field

• Status field takes two values ACTIVE PASSIVE
• Only Active vehicle disseminate the message
• Passive vehicle only store the message and act as
  back-up
• Passive vehicle can become Active to increase
  reliability and expand the covered area

7
Implementation Issues

• Java language gives us platform independence
• Simulation is done through Java based JiST/SWANS
  simulator
• STRAW realistic vehicle mobility model

8
Algorithms

• Distance calculations
• Location_new get_location() from GPS
• distance calculate_euclidean_distance(
  location_new , location_old )
• Push distance to distances array
• Location_old location_new
• Sleep ( 1 second )

9
Algorithms (2)

• Jam detection
• for i in 3 minutes interval do
• d d distances i
• If d lt d1 then
• jam true
• else
• jam false
• Sleep ( ?t1 seconds)

10
Algorithms (3)

• Enquiry for new events
• send (enquiry message) to all neighbors
• while receiving responses do
• responses_count
• If responses_count gt (max Number of lanes)
  then
• generate_message (jam)
• Sleep ( ?t2 seconds)

11
Algorithms (4)

• Message dissemination
• If status of message m is Active then
• If message m1 is received and m1 is new
  version of m then
• Erase (m)
• m.status passive
• Else
• send (m) to all neighbors
• Sleep ( ?t3 seconds)
• Else if new message m2 is received and m2.status
  active then
• Sleep ( ?t3 random offset )
• Else
• m.status active
• Sleep (?t3 seconds)
• End if

12
Functional scheme
13
Q A