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
INTRODUCTION
• 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.
INTRODUCTION
• 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
rediscovery.
INTRODUCTION
• Thus, we adopted multi-path routing
protocol to decrease the route discovery
frequency and mitigate broadcast storm
problem.
• 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)
protocol.
Adaptive Routing Metric
• When selecting metric of link-quality
information, we adopted the Maximum
Retransmission Counts (MRC) along one
path
• 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_HOP(K), MAX_MAXRETRAN(K) and
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-SAOMDV 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
MAX_MAXRETRAN(K).
PERFORMANCE EVALUATION
• 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.
PERFORMANCE EVALUATION
PERFORMANCE EVALUATION
PERFORMANCE EVALUATION