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June,20,2006 IWQoS2006@Yale University 1
GVGrid: A QoS Routing Protocol for Vehicular Ad Hoc Networks
Weihua Sun, Hirozumi Yamaguchi,Koji Yukimasa, Shinji Kusumoto
Osaka University, Japan
June,20,2006 IWQoS2006@Yale University 2
Background Vehicular Ad Hoc NETworks (VANETs)
Special type of MANETs which use vehicles as nodes
VANETs are used for Local information propagation for safety driving
& driving assistance (traffic jam, accident, parking, shops/restaurants information etc.)
Extend wireless range of ISP base stations
Internet
INOUT
June,20,2006 IWQoS2006@Yale University 3
Research Goal & Related Work Research goal
to design a routing protocol to build a stable inter-vehicle route Existing work
Broadcast UMB[7], RBM[8], MDDV[10]
VANETs Data dissemination to every node
Routing CarNet[14], GPCR[3]
VANETs Point-to-point communicationRoad structure is considered
None of them uses vehicles’ movement characteristics
June,20,2006 IWQoS2006@Yale University 4
Our Proposal We propose a routing protocol called GVGrid on VANETs We consider that the following vehicles’ movement
characteristics are important for stable routes Density
A certain density brings lower relative speed Alternate nodes can be easily found when a route is broken
Direction & Speed The same direction and similar speeds are better for link
stability There are many vehicles on major streets – density is high,
and directions & speeds are similar
GVGrid establishes a route along major streets to achieve longer route lifetime
June,20,2006 IWQoS2006@Yale University 5
Protocol GVGrid Overview GVGrid establishes a stable network route
between 2 fixed regions1. GVGrid selects a network route along major streets
2. Nodes toward the same direction are preferred
D
S
D
S
a
b
c
June,20,2006 IWQoS2006@Yale University 6
Assumptions Each node is equipped with
Same Ranged Wireless Device IEEE802.11, etc.
Car Navigator (GPS + Digital Map) Accurate geographic information, and
roads and direction information Grid
Geographic region is divided into grids Grid size w is determined based on r
so that node in every grid can communicate with nodes in neighboring grids
Nodes exchange the following information by hello messages Position, Road, Direction and ID
June,20,2006 IWQoS2006@Yale University 7
Route Discovery Process (1/2) Find all route candidates
that follow driving routes from S to D
1. S sets a forwarding zone2. S sends a RREQ message
to a node in every neighboring grid
3. Each node forwards the RREQ message in the same way
Road and node information is added when RREQ is forwarded
S
D
June,20,2006 IWQoS2006@Yale University 8
Neighbor Selection Strategyin RREQ Forwarding
Only one node is selected in a neighboring grid
A node on the same street is selected prior to the others
If there are multiple nodes, a node with the same direction is selected
If there is no such a node, a node on the crossing street is selected
u
v
w
x
Xy
z q
<22>
<00> <10> <20>
<01>
<02>
<11>
<12>
<21>
June,20,2006 IWQoS2006@Yale University 9
Route Discovery Process (2/2) Confirm the best route
from plural candidates1. Node d’ with the smallest ID
in grid D becomes the “leader” node
2. Node d’ calculates the best route from the information included in RREQs By estimating route lifetime
3. Node d’ transfers RREP to S via the selected route to confirm it
S
Dd’
June,20,2006 IWQoS2006@Yale University 10
Route Lifetime Estimation Leader d’ calculates the Number of Disconnections per
Time (NDT) of the candidate routes using the information in RREQs
(1) (2) (3.1) (3.2) (3.3)
Sd’
S does notmove
d’ will leavefrom D
Signal stop Turn Turn &Signal Stop
June,20,2006 IWQoS2006@Yale University 11
Route Maintenance Process We restore the original route
when the route is broken because the original route is considered
the best route based on the estimated route lifetime
For this purpose, the grids of original driving route are memorized by all nodes on the route
When the route is broken1. Exclude all nodes outside the original
route2. Repair the route by nodes which remain
on the route3. Select alternate nodes from the front
grid if no node remains in the grid
June,20,2006 IWQoS2006@Yale University 12
Simulation setup Traffic simulator NETSTREAM (Toyota
Central R&D Labs) Wave range: 200m
Grid size: 70m
Field size: 1,500m x 1,500m Route lengths: 500m 1,000m 1,500m 2,000m
Node max speeds: 8.3m/s~16.6m/s
Density: 720/km2 (3~6/grid), 240/km2 (1~2/grid)
Message collision was not considered Propagation Model
Basically only Line-of-Sight is considered Exceptionally, nodes nearby intersection
within 30 meters can communicate with nodes in the same region X
X
June,20,2006 IWQoS2006@Yale University 13
Implementation of GPCR (for Comparison Purpose)
An on-demand geographic routing protocol for VANETs[3] GPCR searches the network in the
depth-first. greedy forwarding way
When the route is broken, all links were disabled without repairing
GPCR does not exploit vehicles’ moving characteristics to improve the route lifetime and stability of communication
[3]C. Lochert, M. Mauve, H. Fusler, and H. Hartenstein. Geographic routing in city scenarios. ACM SIGMOBILE Mobile Computing and Communications Review, pages 69-72, 2005.
<1><2>
d1
d2
<3>
d1
d2
<4>
d1
d2
<5>
X
<6>
d
s
u
v
w
x
y
z
o
pq
June,20,2006 IWQoS2006@Yale University 14
Performance Metrics Route Lifetime
The whole route’s lifetime shows the stability The longer route lifetime is better to provide a
stable data transmission Link Lifetime
The lifetime of node-to-node links shows the similarity of nodes’ movement
Higher link lifetime can help the route’s stability Packet Delay and Route Connection Status
Low packet delay and stable connection is important for high quality data transmission service
June,20,2006 IWQoS2006@Yale University 15
Ave. Route Lifetime (Dense)
GVGrid
GPCR
S- D Route Length (m)
Route
Lifeti
me (
s)The number of hops is more than 30. This is too far to maintain a stable network
1000 1500 2000
10
8
6
4
2
500
GVGrid shows good performance in
short route length
June,20,2006 IWQoS2006@Yale University 16
Link Lifetime Distribution
GPCR
GVGrid
S-D Route Length (m)
Lin
k Li
feti
me (
s)
Because GPCR does not repair the route, all links are disabled when the route is broken
Link lifetime is very long in GVGrid because these links can be reused in maintenance process
30
25
20
15
10
5
0 500 1000 1500 2000
June,20,2006 IWQoS2006@Yale University 17
Packet Delay (distance=500m)
GVGrid GPCR
Dela
y (
ms)
Dela
y (
ms)
Timeline (s) Timeline (s)
Broken Broken
The delay of GVGrid is a little more than GPCR, because the number of hops of GVGrid is larger than GPCR
Stable connection is important for high quality data transmission.
GVGrid broke 15 times GPCR broke 19 times
1000
800
0
200
400
600
200 400 600 800 1000 0 200 400 600 800 1000
June,20,2006 IWQoS2006@Yale University 18
Conclusion We have proposed a QoS routing protocol GVGrid
for VANETs GVGrid constructs a route along major streets, taking
nodes toward the same direction as possible Through simulation results, we confirmed that GVGrid
could provide high stability for high quality data transmission services
Future work More accurate simulations in various maps, densities
and mobility Make a network simulator inter-work with the traffic
simulator to simulate the message collisions and so on
June,20,2006 IWQoS2006@Yale University 19
Thank You For Your Attention
June,20,2006 IWQoS2006@Yale University 20
C : Signal cycle ρ: Ratio of the green light time in C θ: Probability that a node stays on the road
after passes an intersection