A Collaboration-based Hybrid Vehicular Sensor Network Architecture

1
A Collaboration-based Hybrid Vehicular Sensor
Network Architecture
Fanyu Kong Department of Electrical and Computer
Engineering Michigan Technological
University Houghton, Michigan 49931 Email
fkong_at_mtu.edu
Jindong Tan Department of Electrical and Computer
Engineering Michigan Technological
University Houghton, Michigan 49931 Email
jitan_at_mtu.edu

• ??? 69721047
• ??? 69721020
• ??? 69621057

2
Outline

• Introduction
• Background
• Overview
• Elements
• Communication Protocol
• Static and mobile sensors
• Mobile and Mobile sensors
• Traffic Congestion Control
• Simulation And Evaluation
• Conclusion

3
Introduction(1/3)

• An intelligent transportation system aims to make
  roads safer and less congested.
• Compared to traditional sensor networks, this
  recently emerged sensor network is not restricted
  by the power supply and the storage space.
• This paper is concerned with such an system
  framework consisting of static road side sensors
  and mobile vehicular sensors.

4
Introduction(2/3)

• Presents a detailed data collection, storage and
  exchange mechanism for vehicular sensor
  networks and addresses the congestion problem
  raised by multiple mobile sensor users when
  accessing to a single road side sensor at the
  same time.
• When these road side and vehicular sensors are
  networked together to share information, a
  dynamic infrastructure for smart road can be
  formed to make roads safer and less congested.

5
Introduction(3/3)

• The simulation results show system can reduce 42
  traf?c jams and save the drivers for upto 36.6
  total time.

6
Background(1/5)

• The advances in wireless networking, sensing and
  embedded microprocessors have enabled a new
  generation of large scale sensor networks
  suitable for multiple future commercial and
  military applications.
• In an intelligent transportation system, plenty
  of sensors should be used for traf?c monitoring
  purpose.
• This paper is concerned with the design of an
  optimal system architecture for such a vehicular
  sensor network.

7
Background(2/5)
Several assumptions have been made

• First, we assume vehicles participating in this
  system are equipped with GPS devices, so they can
  know their own positions correctly.
• Second, all the sensor nodes on both road sides
  and vehicles are equipped with identical
  preloaded digital maps.
• Also, all the sensors have plentiful space for
  storage.
• The last and the most basic assumption we make is
  that vehicles can detect and recognize the road
  information correctly.

8
Background(3/5)

• The central question addressed in this paper is
  how to design a feasible, ef?cient and robust
  vehicular sensor network framework to monitor
  road traf?c and provide desired and reliable
  information for users, particularly for drivers
  in automobiles.
• We focus on vehicular mobility, collaboration
  between mobile and static nodes, and information
  exchange among mobile cars.

9
Background(4/5)
Some of the questions addressed in this paper are

1. What kind of role do maps act in the system? How
   to make use of the map to deploy road side
   sensors effectively and ef?ciently?
2. What are the road side sensors used for? How to
   differentiate them from the mobile sensors and
   why they are necessary in the whole system?
3. What is the role of mobile sensors? How to make
   use of their mobility and how to decrease the
   negative in?uence to connectivity caused by the
   mobility?
4. What is the communication protocol for static
   sensors, mobile sensors and both of them to make
   them work together?
5. How to control traf?c congestions with the system?

10
Background(5/5)

• We answer these questions by presenting a system
  architecture consisting of road side sensors and
  mobile sensors, communication protocols between
  these models and traf?c control mechanisms.
• Usually, the road side sensors are positioned
  near the intersection and are used to collect
  data from cars passing by while vehicular mobile
  sensors, can know the road information along
  their own path, meanwhile, the key idea is that
  they can communicate with other sensors to get
  more information about the adjacent pathes.

11
Overview(1/3)

• Our collaborative-based vehicular sensor network
  framework consists of two kinds of sensors
• Road side sensors
• Larger storage space than vehicular sensors.
• Collect data from all the vehicular sensors
  passing by
• They are interested in data from any location.
• When a car comes into the communication range of
  a road side, communication will happen.

12
Overview(2/3)

• Mobile vehicular sensors
• Communicate with both road side sensors and
  mobile sensors.
• Query about the road condition to the destination
• Send its data to the road side sensor.
• When two cars moving across, data on both cars
  will be exchanged.
• Then both cars will know much more about what
  happened far away in their direction.

13
Overview(3/3)
14
Elements(1/12)

• A. Road segmentation
• 1) Roads in the city
• We divide roads into segments between two
  neighboring intersections, as traffic lights are
  natural traffic deliminators.
• Location of the deliminators can be easily found
  from GPS devices.
• Coordinates of there positions can be found in
  the digital map
• 2) Free way
• Free way is longer than a normal road and has no
  intersections or stop signs in the middle.
• Cars enter and leave the free way at the exits.
• Free way is jammed, we need to make the car
  informed in advance. So we consider exits as
  traffic deliminators.

15
Elements(2/12)

• Two road side sensors, located at the both ends
  of the segment
• Get the road condition before entering this
  segment.
• Intersection waiting for the traffic lights, they
  have enough time to collect data form road side
  sensors

16
Elements(3/12)

• B. Road information data model
• When road segment is congested, it can be either
  serious or minor.
• Every mobile sensor and static sensor has a
  database. And road information corresponds to a
  record

17
Elements(4/12)

• Typical record includes
• Location
• Each record is uniquely identified.
• Keeps only the latest road information.
• Road condition
• We record the condition by an unsigned integer.
• The larger of which, the worse road condition is.
• When it is zero, the condition of segment is
  perfect.
• Never seen the condition of a certain road
  segment, the value is UNKNOWN.

18
Elements(5/12)

• Typical record includes
• The time of the latest record
• As time passes, the road condition will change.
• Updating is time consuming.
• We just keep a record of the time,
• when querying this record, the system will
  estimate the current state of the road.

19
Elements(6/12)

• C. Road side sensors
• More or less a small computer with database.
• They can get and restore data from any car in
  their communication range.
• Get their destination road condition information
  from the road side sensors, because these sensors
  have a larger virtual monitor range.

20
Elements(7/12)

• Road side sensor is realized by 5 individual
  components
• Core
• It coordinates the processing of traffic
  information and new data packets.
• Database
• It restores traffic information.
• Indexed by the road segment identifier.
• Map and position
• Provides the area map.
• Match the map and geographical coordinates.
• Communication
• Communicate with other mobile cars.

21
Elements(8/12)

• Block diagram of road side sensor

22
Elements(9/12)

• D. Mobile car sensors
• Mobile sensors are located on the moving cars
  with GPS devices.
• Sensors monitor the car speed, at the same time
  GPS can give the precise location and load
  segment.
• Sensors can acquire the road condition through
  the car speed and the road segment.
• When data exchange happens
• Data related to the destination or along the
  route to the destination will have a higher
  priority to transmit.

23
Elements(10/12)

• Mobile sensors are able to communicate
• Static road side sensors
• They can upload their own data to the access
  point
• Get information they need.
• Mobile sensors
• They can get data from the other cars near by.

24
Elements(11/12)

• Components of mobile sensors.
• GPS
• It provides the precise position information.
• Sensor
• Determines traffic condition for the current
  location of the vehicle.
• Communication
• Communicate with both mobile and static sensors.
• Display
• Visualization of the current available
  information, the position of the vehicle and the
  destination.
• Red represents jammed slow road, yellow medium
  and green high speeds.

25
Elements(12/12)

• Block diagram of mobile sensors.

26
Communication Protocol

• Static and mobile, mobile and mobile can
  communicate with each other. and managed.
• Static and mobile sensors
• Mobile and Mobile sensors

27
Static and mobile sensors(1/2)

• Mobile sensor moves into the the communication
  range of a road side sensor
• Road side sensor will detect this mobile sensor
  and send a connection request
• After road side sensor receiving the
  acknowledgement,a connection will be setup.
• The destination and a data mask will be sent to
  the road side sensor
• Road side sensor will transmit data with priority

28
Static and mobile sensors(2/2)

• When a mobile sensor want to transmit its own
  data to the static sensor, the static sensor
  first sends a data mask filter to the mobile
  sensor
• The mobile sensor will calculate the data to send
  first.
• At this time, other vehicular sensors may change
  the static sensor database
• The static sensor has to update its mask filter
  after receiving new packets and send the new mask
  filter to the mobile sensor.

29
Mobile and Mobile sensors (1/4)

• Vehicular sensor is moving on a road segment,
  where it is out of range of road side sensors, it
  will be valuable to communicate with other cars
• Mobile sensors also need to setup a connection to
  transmit data. And a data mask filter is also
  sent to the sender first
• Then the sender will send data with priority
  according to the filter
• And in our model, vehicular sensors only
  communicate to their immediate neighbors
• No message forwarding between sensors.

30
Mobile and Mobile sensors (2/4)

• Communication between mobile sensors is different
  from that in static and mobile sensors
• The difference lies in the moving direction of
  mobile sensors.
• classify two categories based on the moving
  direction, same directional grouping and
  different directional passing by.

31
Mobile and Mobile sensors (3/4)

• Same directional
• When a car joins a group, it will send its own
  data mask filter to the nearest car in the group
• New sensing data will be shared in the group. The
  group will maintain a unique group ID, and every
  car will broadcast a group maintenance message to
  the group. The receiver will reply an
  acknowledgement with group ID.
• If a car leaves a group, it will receive
  different reply compared to former cases.

32
Mobile and Mobile sensors (4/4)

• Different directions
• If a group of vehicular sensors encounter another
  mobile sensor coming from the direction they are
  moving to
• Connection will be setup between the first car in
  the group and the coming car.
• Cars in a group may have different destinations,
  so they are interested in different data.The
  coming car will transmit all its data to the
  group, meanwhile the header of the group will
  send all its data to the coming car too

33
Traffic Congestion Control(1/2)

• Road information can be displayed on the
  screen,the program on the computer will give the
  driver directions when running.

34
Traffic Congestion Control(2/2)

• 1 .Get the destination from the driver.
• 2. Get current location from GPS.
• 3.Calculate the possible acyclic pathes to the
  destination.
• 4. Fetch road condition of these pathes from the
  database.
• 5. Estimate the time to the destination along the
  possible routes.
• 6. Find the shortest estimation time and display
  the result on the screen.
• 7. Repeat 2 until driver inputs a new destination.

35
Simulation And Evaluation (1/4)

• For simplicity we build a map consisting of 40
  road segments and 25 intersections. Every segment
  is 300 meters long. Up to 1000 cars with random
  start points and destinations are running on the
  map
• We get the whole system performance by measuring
  the number of roads which are jammed and the
  total time for all the cars to reach the
  destination, with and without the database
  support respectively.

36
Simulation And Evaluation (2/4)

• At the beginning of each trial, we randomly
  allocate 1000 cars on the map, some cars may
  occupy a same position, so the beginning of Fig.
  5. is very high

37
Simulation And Evaluation (3/4)

• As the running of the whole system, we can find
  the difference between the traffic conditions
  with database support and without database
  support are significant. And at the peak time,
  the database support can reduce the number of
  traffic jams by 42.
• If with the support of the database, the average
  time is reduced by 36.6.

38
Simulation And Evaluation (4/4)
39
Conclusions(1/2)

• Traffic problems such as traffic jams and traffic
  delay are some of the most critical issues in our
  life.
• If correct road condition information can be
  delivered to the drivers before the cars move
  into jammed areas, these problems will be
  significantly alleviated.
• As sensor network can deploy on the cars and road
  side, and they can communicate and collaborate
  together, a new solution is possible.

40
Conclusions(2/2)

• In this paper, we propose a collaborative hybrid
  method to deliver desired data to particular
  drivers effectively and efficiently.
• The simulation results show the system can reduce
  42 traffic jams and save the drivers upto 36.6
  total time.