Wireless Routing Protocols

Matt Cleveland

Mobile network types

Infrastructured network is a network, such as this campus, with fixed and wired gateways

Ad-hoc network, has no fixed routers, all nodes are capable of movement and all may function as routers (emergency search and rescue operations, conventions where people wish to quickly share information, and data acquisition in inhospitable terrain)

Ad-Hoc Network types

Table driven

Ad-Hoc Network types

On-demand

Table-Driven Protocols

Have consistent overview of the network Table contains routing information to every other

node in the network Typically broadcasts a specified beacon “hello”

to network at fixed intervals of time and updates its connection table accordingly

Destination Sequence Distance Vector (DSDV), Wireless Routing Protocol (WRP), and Cluster-head Gateway Switch Routing (CGSR) are common protocols using this technique

Destination Sequence Distance Vector (DSDV) Routing table contains list to all available

destinations, number of hops required to reach each destination, and the sequence number (last updated)

Periodically transmit updated table information to neighboring machines, or in the event of a change, do so as well

Destination Sequence Distance Vector (DSDV) Full dump – transmit entire contents of

routing table to neighbors Incremental update – transmits only

pertinent table updates to neighbors Full dump occur in rapidly-changing

network where incremental updates are used in relatively stable networks to avoid extra traffic

Wireless Routing Protocol (WRP)

Each node contains a Distance table, a Routing table, a Link-Cost table, and a Message-Retransmission list

Distance table contains distance between the node and a given node y from each of current node’s neighbors

Routing table contains list of distances between the node and a given node y from given node x, along with the predecessors and successors of x

Wireless Routing Protocol (WRP)

Link-Cost table contains the cost of connecting to each of the node’s neighbors, along with information regarding timeouts

Message Retransmission List has information regarding which nodes need to be resent information (like stop-N-wait)

Clusterhead Gateway Switch Routing (CGSR) protocol Is based on the DSDV protocol Nodes are combined into clusters with a

specified cluster-head Nodes that lie in overlapping clusters are

designated as Gateway nodes

Clusterhead Gateway Switch Routing (CGSR) diagram

Clusterhead Gateway Switch Routing (CGSR) Requested packets are transmitted to

cluster-head, then transmitted to the gateway node

Receiving end does this in reverse order Nodes contain table of paths to other

nodes on network using DSDV algorithm

Advantages of Table-Driven Protocol

Having up-to-date list of all possible connections to devices on network

Disadvantages of Table-Driven Protocols Continuous table updating may be

redundant and unnecessary (wastes CPU and battery, which are extremely limited commodities in a mobile device)

Tables updating causes unnecessary network overhead in many instances

On-Demand routing protocols

When path is needed to given source, must wait until path is discovered

AODV, DSR, and ABR are common protocols using this strategy

Ad-Hoc On Demand Vector Routing (AODV)

To find path to destination, source broadcasts a request packet

Packet is rebroadcast by neighbors and neighbors’ neighbors until it either reaches the destination or finds a node with recent routing information regarding the destination

Request is returned, and each node in path appends its routing information in the request

Ad-Hoc On Demand Vector Routing (AODV)

Dynamic Source Routing (DSR)

Nodes contain path routes in cache, which are updated when new information is discovered

When a message is sent, a node checks its cache to see if the destination is known, if so, message is sent, otherwise a request is broadcast to neighbors asking for path

Associativity-Based Routing (ABR)

Routes are selected based on degree of association stability of given nodes.

Nodes periodically generate beacons to acknowledge is alive.

Beacon is received and nodes are updated with node’s information (degree of association stability).

Associativity-Based Routing (ABR)

Has three phases1. Route Discovery –

a) Broadcasts query: sends request for path to destination node, nodes with information respond, appending their information (associativity) on the query for a full path

b) The path to the destination with the best associativity is chosen

Associativity-Based Routing (ABR)2. Route reconstruction – prompted by moving or

new nodes, which causes change in associativity

a) Partial route discoveryb) Invalid route erasurec) Valid route updatesd) New route discovery

3. Route Deletion – when a path is found to be no longer valid, a route delete (RD) broadcast is sent to other nodes so that they can update their information

Advantages of On-Demand Protocols

Only have to determine routing path when necessary

Highly dynamic and adaptable, doesn’t rely on a stable network

Disadvantages of On-Demand Protocols

Takes longer to discover routing path than it does to look it up on an IP table

Bibliography

http://www.computingunplugged.com/issues/issue200407/00001326001.html

http://citeseer.ist.psu.edu/cache/papers/cs/16265/http:zSzzSzusers.ece.gatech.eduzSz~cktohzSzroyer-ck.pdf/royer99review.pdf

http://www.cse.ohio-state.edu/~jain/cis788-99/ftp/adhoc_routing/index.html