June,20,2006IWQoS2006@Yale University1 GVGrid: A QoS Routing Protocol for Vehicular Ad Hoc Networks...

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


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


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


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


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


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


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


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>


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’


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


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


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


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


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


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


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


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


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


Thank You For Your Attention


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

June,20,2006IWQoS2006@Yale University1 GVGrid: A QoS Routing Protocol for Vehicular Ad Hoc Networks...

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