By,S.R.MANOJ (FINAL CSE),

S.SANTHOSH (FINAL CSE).

INTRODUCTIONToday’s broadband is associated with wired line using DSL or

cable modem services.Moreover , in rural areas the people are unwilling to go for

equipments for connection.Broadband Wireless Access (BWA) has emerged as a

promising solution for “last mile” access technology to provide high speed connections.

IEEE 802.16 and its associated industrial consortium WIMAX begun to provide a high speed broadband without wired infrastructure.

It is of low cost, provides interoperability and reduces risk to operators.

DESCRIPTIONThe first standard of IEEE 802.16 was published in 2001 and

had frequency range of 10-66 GHZ and required line of propagation for communication.

This reduces multipath distortion and increases efficiency.Providers could use multiple channels for a single transmission

to provide BW up to 350 Mbps.A number of wireless routing protocols are already designed to

provide communication in wireless like AODV,OLSR,DSDV,ZRP etc.,

Even though all are compared already none came for WIMAX environment.

WIRELESS ROUTING PROTOCOLSIn this paper we compare the performance of :

• Ad-hoc On- demand distance Vector Routing Protocol(AODV).• Dynamic source Routing (DSR).• Optimized Link State Routing(OLSR).• Zone Routing Protocol(ZRP).

Ad-hoc On- demand distance Vector Routing Protocol(AODV)Is a variant of classical distance vector

routing algorithm.It differs from other by keeping one entry per

destination and has multiple route cache entries for each destination.

ROUTE DISCOVERY:

Contd..ROUTE MAINTAINENCE:

A route established between source and destination and is maintained until the source needs the route.

It sends the error message (RERR) to the affected active upstream neighbors and the error is propagated until the source is reached.

The affected source node may then choose to either stop sending data or reinitiate route discovery for that destination by sending out a new RREQ message.

DYNAMIC SOURCE ROUTING (DSR)This is an example for on-demand routing

protocol.Designed for use in Multihop ad hoc networks

of mobile nodes.It allows the network to be completely

organizing and self-configuring and does not need any existing network infrastructure.

It doesn’t uses periodic routing messages like AODV, thereby reduces the network bandwidth overhead, conserves power and large updates.

Contd..ROUTE DISCOVERY:

When a mobile node has a packet to send, it searches whether there is any already existing unexpired node, if so uses it, otherwise it does route discovery and sends it.

Each time it checks for its cache for the destination address it adds its own address and then performs route discovery.

ROUTE MAINTAINENCE: The source is responsible for receiving the

acknowledgement . The packet is retransmitted until the conformation of

receipt is received. After retransmission of a maximum number of times the

source truncates a packet.

OPTIMIZED LINK STATE ROUTING (OLSR)

It inherits the stability of pure link state algorithm and adopted for mobile ad hoc networks.

It is proactive in nature and has the advantage of having routes immediately available when needed.

The key concept is multipoint relays (MPRs).MPRs are a selected set of nodes that broadcast messages

during flooding.Hence, it reduces size of control packet and it doesn’t

generate extra control traffic in response to failures.

Contd..NEIGHBOURS SENSING:

For detection of messages all nodes periodically send its own messages to all its neighbors(one –hop).

MULTIPOINT RELAY STATIONS: Each node of network selects its own set of

multipoint relays.

Contd..MPR INFORMATION AND ROUTING

TABLE: Each node periodically broadcasts one type of

control messages called Topology Control (TC) to build intra-forwarding database needed to routing packets.

A TC consists of MPR selection set and a sequence number , incremented when the selection set changes.

Each node maintains a routing table which is calculated from the TC message it receives.

The entry consists of destination address, next hop address and distance.

ZONE ROUTING PROTOCOLIt is a hybrid protocol which combines both

proactive and reactive schemes.

SIMULATION RESULTS

CONCLUSIONA performance comparison of four different

ad hoc routing protocols (AODV, DSR, OLSR and ZRP) is performed here using different mobility scenarios.

Simulation has been conducted in Mobile WiMAX environment.

From the result of our studies, it can be said that, on an average ZRP and AODV perform better than DSR and OLSR.

QUERIES