An Adaptive Cross-Layer Multi-Path Routing Protocol for Urban VANET

					 An Adaptive Cross-Layer Multi-Path
 Routing Protocol for Urban VANET

             指導教授:許子衡 教授
             學  生:董藝興 學生

作者:Yufeng Chen; Zhengtao Xiang; Wei Jian; Weirong Jiang;
出處:Automation and Logistics (ICAL), 2010 IEEE International
Conference on
• To construct networks between vehicles for
  future applications, such as active safety
  and traffic management, suitable routing
  protocols are needed.

• When designing routing protocols, we
  should select routing metrics firstly, which
  influence routing performance heavily.
• In VANET, high mobility and complex
  environment may cause connections to break
  off with high probability, which means high
  requirements of route rediscovery.

• Multi-path routing protocol works better in
  such circumstances because candidate routes
  can be used to avoid frequent route
• Thus, we adopted multi-path routing
  protocol to decrease the route discovery
  frequency and mitigate broadcast storm

• Based on the above considerations, an
  adaptive cross- layer multi-path routing
  protocol is proposed based on the
  improvement of Ad hoc On-demand
  Multipath Distance Vector (AOMDV)
      Adaptive Routing Metric
• When selecting metric of link-quality
  information, we adopted the Maximum
  Retransmission Counts (MRC) along one

• The MRC gives the estimation of the
  worst link along one path.
         Adaptive Routing Metric

•   α is the weight of hop-count,
•   β is the weight of MRC,
•   (1-α-β) is the weight of speed,
•   K is the number of paths to destination node D,
    MAX_MAXSPEED(K) are the maximum hop-count,
    the maximum MaxREtran, and the maximum
    MaxSpeed of the K paths.
    Designing Routing Protocol
• The MaxREtran of bi-directional paths
  should be obtained respectively and stored
  in routing tables.

• However, the measurement of MaxREtran
  of S→D should be stored in the routing
  table of source node S.
    Designing Routing Protocol
• Routing table The routing table entry
  structure and route list structure of R-S-
  AOMDV are shown in Fig.1 and Fig.2.
    Designing Routing Protocol
• Routing protocol When source node S
  needs a route to destination node D, and
  there are not available paths, the source
  node will initiate a route discovery process.

  – --First, node S broadcasts RREQ routing packet,
    as source nodes do in AOMDV.
     Designing Routing Protocol
• --Second, when other nodes receive duplicate
  RREQ packets, they will establish or update
  the reverse paths to source node S according
  to different first hops of RREQ.
• --Third, if RREP packets are received by other
  nodes, the forward paths to node D will be
  established in routing table according to
  different RREP First Hops and RREQ First Hops
  in RREP packets.
    Designing Routing Protocol
• --Fourth, when other node receives a
  RRETRAN packet with marked ACK from a
  neighbor, it will search their routing table
  to find a reverse path whose Last Hop is
  identical with the First Hop of the
  RRETRAN packet.
    Designing Routing Protocol
• --Fifth, when other nodes receive RRETRAN
  packets with non-marked ACK from their
  neighbors, they will identify the forward
  paths according to the neighbors.
• --Sixth, when forwarding data packets, the
  weights of hop-count, MRC and speed are
  adjusted according to the current
• Simulation time is 300 seconds.
• We simulated two urban scenarios, one for
  sparse scenario with 20 nodes and the
  other for dense with 50 nodes.
• The maximal speed is 15 m/s.
• Acceleration is set to 0.5 m/s 2 .
• The 802.11 MAC layer is used with
  Shadowing propagation model and the
  communication range is 250m.

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