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 select the node as MPR  Broadcast to all nodes  Each nodes calculate topology and route from this 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-A-B-D Source Node S F C G A S-A-B-D E H B S-A-B-D D Destination Node I 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 Distance Vector  Smaller packet  Route is not in the packet  Smaller routing table  Each node know only next hop node 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