A-STAR:
A mobile ad hoc routing strategy for
metropolis vehicular
communications
B. Seet, G. Liu, B. Lee, C. Foh, K. Wong, and K. Lee,
in Lecture Notes in Computer Science,
vol. 3042, no. 0302-9743.
Springer Berlin / Heidelberg, Jan 2004, pp. 989–999.
報告學生：
69821046 張君睿
69821008 宋富馨
69821049 劉奕緯
Outline
• Introduction
• Challenges of Position-Based Routing in IVCS
• Anchor-based Street and Traffic Aware
Routing(A-STAR)
• Mobility Model and Simulation Setting
• Simulation Results and Analysis
• Conclusion
Outline
• Introduction
• Challenges of Position-Based Routing in IVCS
• Anchor-based Street and Traffic Aware
Routing(A-STAR)
• Mobility Model and Simulation Setting
• Simulation Results and Analysis
• Conclusion
Introduction
• MANET routing protocols work well when
– nodes are uniformly distributed
– moving freely
• But vehicular nodes are unevenly distributed
– vehicles tend to concentrate more on some roads
than others
• designed specifically for IVCS in a city
environment.
– Anchor-based Street and Traffic Aware Routing
(A-STAR)
Outline
• Introduction
• Challenges of Position-Based Routing in IVCS
• Anchor-based Street and Traffic Aware
Routing(A-STAR)
• Mobility Model and Simulation Setting
• Simulation Results and Analysis
• Conclusion
Challenges of Position-Based Routing
in IVCS
• A send a packet to d.
• Use Greedy forwarding will fail
– local maximum
• in GPSR, the packet enters into
perimeter-mode
– using the right hand
– Many hop count
•
•
s can reach a, and a can reach b, both in one
hop
Show perimeter-mode to recover local
maximum is very inefficient and timeconsuming.
• much shorter path
– from s to d via a route that passes
through e and f
– But perimeter-mode of GPSR based on
right hand rule
•
is biased to a specific direction when
selecting for the next hop
Outline
• Introduction
• Challenges of Position-Based Routing in IVCS
• Anchor-based Street and Traffic Aware
Routing(A-STAR)
• Mobility Model and Simulation Setting
• Simulation Results and Analysis
• Conclusion
Anchor-based Street and Traffic Aware
Routing(A-STAR)
• adopts the anchor-based routing approach with street
awareness
• using the street map to compute the sequence of junctions
(anchors)
• in a metropolitan area, some streets(major streets) are wider
and accommodate more vehicular traffic than others.
• the street with higher density of vehicular nodes
– more stable
– e.g. city buses path
• computed using Dijkstra's least-weight path algorithm
– e.g. more vehicles, less weight assigned
• called a statistically rated map
Anchor-based Street and Traffic Aware
Routing(A-STAR)
• Local Recovery
– In A-STAR the street at which local maximum
occurred is marked as “out of service” temporarily
– this information is distributed to the network by
piggybacking them onto the packets to be
recovered
– The “out of service” streets are not used for
• anchor computation
• re-computation
Outline
• Introduction
• Challenges of Position-Based Routing in IVCS
• Anchor-based Street and Traffic Aware
Routing(A-STAR)
• Mobility Model and Simulation Setting
• Simulation Results and Analysis
• Conclusion
Mobility Model and Simulation Setting
• M-Grid Mobility Model
– Node heterogeneity
– Preferential movements
– Radio obstacles
Line-of-sight
A
C
B
Mobility Model and Simulation Setting
• Simulation Setting
– Simulator : NS-2
– three bus lines for the M-Grid total of 37
buses will be running in the city
• two with 12 buses
• one with 13 buses
– Speed limit
• buses 50 km/h
• cars 70 km/h
Mobility Model and Simulation Setting
Outline
• Introduction
• Challenges of Position-Based Routing in IVCS
• Anchor-based Street and Traffic Aware
Routing(A-STAR)
• Mobility Model and Simulation Setting
• Simulation Results and Analysis
• Conclusion
Simulation Results and Analysis
• A-STAR differs from GSR and GPSR in two main
aspects
– A-STAR incorporates traffic awareness by using
• statistically rated
• dynamically rated maps
– A-STAR employs a new local recovery strategy
• more suitable for a city environment than
– the greedy approach of GSR
– the perimeter-mode of GPSR
Simulation Results and Analysis
Performance
without local
recovery
Simulation Results and Analysis
Performance
without local
recovery
Simulation Results and Analysis
Performance
with local
recovery
Simulation Results and Analysis
Performance
with local
recovery
Simulation Results and Analysis
Outline
• Introduction
• Challenges of Position-Based Routing in IVCS
• Anchor-based Street and Traffic Aware
Routing(A-STAR)
• Mobility Model and Simulation Setting
• Simulation Results and Analysis
• Conclusion
Conclusion
• A-STAR
– use of city bus route information to identify
anchor paths of higher connectivity
• more packets can be delivered to their destinations
successfully