Ad hoc Network

江崎研究室　修士１年中島　亮

What is Ad hoc Network?

Meaning of Ad hoc Network Ad hoc＝その場限りの Node to node

→ノード間で一時的に形成されるネットワーク

A B

C

Communicate with A… I can!!

Use of Ad hoc Network

Sensor network IC chip Weather sensor Sensor for scout

Mobile network Cellular phone Note PC PDA→movable and weak computation　 and

battery power

Packet transferring

Multi-hop between nodes Efficient packet routing

→need to find efficient route

Efficient route

Multi-hop transferring

Getting routing information Pro-active

Making routing table beforehand Smaller lookup delay but more

communication Ex.　 OLSR, TBRPF

Re-active Look up route when needed Bigger delay but fewer communication Ex.　 DSR, AODV

OLSR

Optimized Link State Routing Hello message

One hop to all neighbor nodes Never forward (IP TTL=1) Message: own and neighbor’s address

HELLO MESSAGE

Feature of OLSR

MPR( Multi-Point Relay ) Smallest set of 1 hop nodes that can join all 2 hop

neighbor nodes Efficient flooding

Pink object in right picture is MPR

Getting topology

TC( topology control ) message All nodes selected as MPR MUST send Contain links between MPR and the node which s

elect the node as MPR Broadcast to all nodes Each nodes calculate topology and route from thi

s TC message and HELLO message

DSR

Dynamic Source Routing Route discovery

Efficient flooding by sequence number Relay node cache route information too

Request Reply

Feature of DSR

Route is written in Packet No loop can occur Confirm connection: use wireless ack

S

B

H

G

F

C

S-A-B-D

S-A-B-D

S-A-B-D

A

E

ID

Source Node

Destination Node

AODV

Ad hoc On-demand Distance Vector Re-active but partly pro-active

Search route when needed Same as DSR

Each node cache route from forwarding packet

Can use the same Hello Message as OLSR use To confirm links to neighbors are alive

Feature of AODV

Distance Vector (DV) Routing table

Destination node’s address Hop number to Destination node Next node to Destination node

Smaller packet Route is not in the packet

Smaller routing table Each node know only next hop node

Distance Vector

Conclusion

Outline of ad hoc network Behavior of OLSR, DSR, AODV Advantages and Disadvantages

OLSR:smaller delay,bigger communication Have way to lessen communication

DSR:bigger delay,smaller communication Have way to lessen delay

→Choose protocol as the situation demands