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Location-Aware Routing Protocolsin a Mobile Ad Hoc Network

Professor Yu-Chee Tseng Dept. of Computer Science and Information Engineering

National Chiao-Tung University( 交通大學 資訊工程系 曾煜棋 )

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Notebook + GPS

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Location-Aided Routing

LAR: in MobiCom 1998.

Main Idea

Using location information to reduce the number of nodes to whom route request is propagated.

Location-aided route discovery based on “limited” flooding

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Location Information

Consider a node S that needs to find a route to node D. Assumption:

each host in the ad hoc network knows its current location precisely (location error considered in one of their simulations)

node S knows that node D was at location L at time t0, and that the current time is t1

Location services in ad hoc networks, refer to A survey on position-based routing in mobile ad hoc networks, M. Mauv

e, J. Widmer, and H. Hartenstein, IEEE Network, Vol. 15 No. 6,  2001.

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Expected Zone

expected zone of D ---- the region that node S expects to contain node D at time t1, only an estimate made by node S

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Request Zone

LAR’s limited floodingA node forwards a route reque

st only if it belongs to the request zone

The request zone should include

expected zone other regions around the expe

cted zone

No guarantee that a path can be found consisting only of the hosts in a chosen request zone.

timeout expanded request zone

Trade-off between latency of route determination the message overhead

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Membership of Request Zone

How a node determines if it is in the request zone for a particular route request

•LAR scheme 1: inside or outside the request zone•LAR scheme 2: based on whether there is any progress

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LAR Scheme 1

Two cases: whether the source node is inside or outside the expected zone?

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LAR Scheme 2

S knows the location (Xd, Yd) of node D at time t0

Node S calculates its distance from location (Xd, Yd): DISTs

Node I receives the route request, calculates its distance from location (Xd, Yd

): DISTi

For some parameter δ, If DISTs + δ ≥ DISTi, node I replaces DISKs by DISKi and forwards the request to its neighbors; otherwise discards the route request

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Telecommunication Systems, 2001.

“GRID: A Fully Location-Aware Routing Protocol for Mobile Ad Hoc Networks”

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Basic Idea

Adopt Positioning Systemssuch as GPS receiversPresident Clinton ordered to discontinue SA (selective availability)

in May 2000will increase the accuracy by an order

Fully utilize location information:route discoverydata forwardingroute maintenance

We propose a new protocol called GRID.

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How to Utilize Location Information:Observation 1

Determine route quality based on location information:passing B is better than passing A

B

A

DS

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How to Utilize Location Information:Observation 2 (“Route Handover”)

Improving the vulnerability and quality of a route based on location information:When B moves away, E can work on behalf of B.When F roams in, using F is more reliable.

B C

AD

F

E

packet routeroaming direction

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Comparison of Using Location Information

Scheme Route Discovery

Packet Relay Route Maintenance

DSR

AODV

ZRP

LAR

GRID

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The GRID Routing Protocol

Partition the physical area into d x d squares called grid.

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Protocol Overview

In each grid, a leader will be elected, called gateway.

Routing is performed in a grid-by-grid manner.

Responsibility of gateway:forward route discovery packetspropagate data packets to neighbor gridsmaintain routes which passes the grid

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Route Search

We can adopt any existing route discovery protocol.

Major features/differences:limit the search range by the locations of source and destination

only gateway will help with the discovery processThe more crowded the area is, the more saving.

routing table is indicated by grid ID (instead of host address)

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Route Search Example

route search route reply

A

CS

B

E F

ID3

2

1

0

0 1 2 3 4 5

3

2

1

0

0 1 2 3 4 5

A

CS

B

E F

ID

first RREQ gateway host

non-gateway hostRREP

duplicate RREQ

(a) (b)

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Route Search Range Options

S

D

q

(c) Fan( )q, r

r

S

D

S

D

(a) Rectangle

(d) Two_Fan( )q, r

(b) Bar(w)

w

S

D

q

qr

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Routing Table Format

Next-hop routing:the next hop is identified by grid ID (not host ID)

Node S B E F D

Destination D D D D D

Next hop (2, 2) (3, 2) (4, 2) (5, 3) null

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Route Maintenance

Two issues:how to maintain a gateway in each gridhow to maintain a grid-by-grid route

Special Feature:longer route lifetime:

as long as there is a host in each gateway, a route will be alivemore robust

In existing protocols, once a node in the route roams away, the route will be broken.

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Gateway Election in a Grid

Any “leader election” protocol in distributed computing can be used.

Weaker than leader election:It is acceptable that there are multiple leaders in a grid.

But “without leader” is less acceptable.

Preference in electing a gateway:near the physical center of the grid

likely to remain in the grid for longer time

once elected, a gateway will remain so until leaving the grid to avoid ping-pong effect

X

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Gateway Election Details

BID(g, loc)

GATE(g, loc)

RETIRE(g, T)

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How to Maintain a Grid-by-Grid Route

Strength: more robust routemobility-resistant

Problems:Gateway moves away:

The gateway election will find the new gateway.So the route will remain alive.

Source moves away: (see next page)getting closergetting farther away

Destination move away: (similar)

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(a) getting closer(b) same length(c) getting farther, remaining connected(d) getting farther, but disconnected

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Relationship of Grid Size and Transmission Distance

r = radio transmission distance d = grid size

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Simulation Model

Physical area of size 1000m1000m n = number of hosts: 100~300 r=300m d = grid size

GRID-1:

GRID-2:

GRID-3:

Roaming speed: 30 km/hr, 60 km/hr

10

2rd

3

2rd

22

rd

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Route Lifetime

With better route maintenance, our route lifetime is longer.

30 km/hr 60 km/hr

0

10

20

30

40

50

60

70

80

100 150 200 250 300

The number of hosts

Ave

rage

tim

e of

per

con

nect

ion(

sec) GRID-1

GRID-2

GRID-3

LAR

AODV

0

10

20

30

40

50

60

70

80

100 150 200 250 300

The number of hosts

Ave

rage

tim

e of

per

con

nect

ion(

sec) GRID-1

GRID-2

GRID-3

LAR

AODV

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Routing Cost (s=30 km/hr)

0

2

4

6

8

10

12

14

16

18

20

GRID-1 GRID-2 GRID-3 LAR AODV

Rou

ting

Cos

t

Gateway-Election Packets Per Data PacketRouting Packets Per Data Packet

0

2

4

6

8

10

12

14

16

18

20

GRID-1 GRID-2 GRID-3 LAR AODV

Rou

ting

Cos

t

Gateway-Election Packets Per Data PacketRouting Packets Per Data Packet

0

2

4

6

8

10

12

14

16

18

20

GRID-1 GRID-2 GRID-3 LAR AODV

Rou

ting

Cos

t

Gateway-Election Packets Per Data PacketRouting Packets Per Data Packet

n = 100, 200, 300(number of hosts)

GRID is better in more crowded area.

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Delivery Rate

With less routing cost (and thus less traffic load), our packets can be delivered with higher success rate.

30 km/hr 60 km/hr

60%

70%

80%

90%

100%

100 150 200 250 300

The number of hosts

Del

iver

y ra

te

GRID-1

GRID-2

GRID-3

LAR

AODV

60%

70%

80%

90%

100%

100 150 200 250 300

The number of hosts

Del

iver

y ra

te

GRID-1

GRID-2

GRID-3

LAR

AODV

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Route Length

Limited by gateway positions, the route length could be longer for GRID approach.

30 km/hr 60 km/hr

0

2

4

6

8

10

100 150 200 250 300

The number of hosts

Hop

cou

nts

per

rout

e

GRID-1GRID-2GRID-3LARAODV

0

2

4

6

8

10

100 150 200 250 300

The number of hosts

Hop

cou

nts

per

rout

e

GRID-1GRID-2GRID-3LARAODV

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Implementation Experience

Platform:Red Hat Linus

building our routing protocol in the kernel

5 ~ 10 notebooksWaveLAN cards

Application:ad hoc classroom ( 隨意教室 )

打破傳統教室界線anytime, anywhere classroom

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Conclusions

A FULLY location-aware routing protocol:route discovery: by gateways onlydata forwarding: by gateway ID, instead of host IDroute maintenance: like handoff in GSM systems

Taking advantage of geometric property of network.instead of graph property in other approaches

Less routing costlonger route lifetime, more resilient routeless traffic load

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Geographical Routing Using Partial Information Geographical Routing Using Partial Information for Wireless Ad Hoc Networksfor Wireless Ad Hoc Networks

Pahul Jain, Anuj Puri, Raja Sengupta

University of California, Berkeley

IEEE Personal Communication, 2001

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Basic Idea

to use the geographical position of the destination in making routing decisionsacyclic routes

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Rule 1: Packet Forwarding

When a node S receives a packet for destination D, it finds the neighboring host X which is closest to D than any other neighbors.then forward the packet to X

S DX

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Rule 2: Route Discovery

If S itself is closest to D than any other hosts. We say that the packet is stuck.Node S initiates a route discovery to destination D, following the

DSR protocol.

S

D

Stuck, initiating route discovery

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Example

physical location

** Initially, everyone only knows its

neighbors.

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Case 1: node A needs a route to destination C at (3, 1).Forward the packet to node B (closest to (3, 1)).B forwards the packet to C.

Case 2: node A needs a route to destination D at (2.5, 0)It gets stuck (no one is closer to (2.5) than itself).A initiates Route Discovery.

finding a new path <A,B,C,D >

A updates its routing table. then forward the packet.

See Table 5 (next page).

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newly learned

learnedfrom

snooping

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Case 3: node A needs a route to destination ED is the nearest to E in A’s routing table.

forward the packet to Next(D) = B

Node B forwards the packet to node C.Node C forward the packet to node E.

note: C will behave based on its own routing table.

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Conclusion

Advantage:Routing table is small in size.Routing tables are cycle-free.Low communication overhead.

Disadvantage:Destination position is known by the source before routing.

A location discovery service is required.

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Geocasting

Geocasting:sending a message to everyone WITHIN a specific geographical re

gionApplication:

emergency messages to a building, or an assembly groundgeographic advertisement

Geocast region

Geocast group