WIRELESS AD-HOC NETWORKS Dr. Razi Iqbal Lecture 6

Wireless Ad-Hoc Networks It is a network in which each device has equal opportunity to connect with any other device in the range. This network does not rely on an central base station device like Routers etc. In this network each node participates in a network and help in forwarding data from one node to another. This type of network allows devices to connect and communicate anywhere anytime without any need of pre- existent infrastructure.

Wireless Ad-Hoc Networks

Wireless Ad-hoc Networks have provided a totally different and new concept of connecting devices. A person carrying two different communicating devices can make these devices communicate with each other using Wireless Ad-hoc Networks and use them as per convenience. A Personal Area Network is an example of Wireless Ad-hoc Networks where devices can be connected to each other using Bluetooth.

Wireless Ad-Hoc Networks Wireless Ad-hoc Networks can be between two devices which is the simplest Ad-hoc Network for fast and temporary communication.

Ad-hoc Routing Protocols The routing protocols of wired network cannot be used for wireless Ad-hoc networks because of extreme mobility of nodes. Wireless Ah-hoc network routing protocols are divided into two major categories Table Driven Routing Protocols On-Demand Routing Protocols

Ad-hoc Routing Protocols Table Driven Routing Protocols In these protocols, each node maintains the routing table containing the routes from that node to every other node of the network. These routing tables are up-to-date based on the latest information which is updated periodically. Each node responds to changes in the topology and that information is updated throughout the network.

Ad-hoc Routing Protocols Table Driven Routing Protocols N1 N2 N3 N4

Ad-hoc Routing Protocols On-Demand Routing Protocol In these protocols, tables are not maintained at each node for routes from that node to every other node of the network. Instead of keeping the routes at beginning, the routes are made on demand whenever required. When communication is required, the source invokes the mechanism of finding the route from source to destination and that route is valid till the node is reachable or route is needed.

Ad-hoc Routing Protocols On-Demand Routing Protocols N1 N2 N3 N4

Ad-hoc Routing Protocols On-Demand Routing Protocol Cluster Based Routing Protocols In such protocols nodes are divided into clusters. Each cluster has a cluster head. Each cluster head contains the information of the nodes of that cluster and information about neighboring cluster heads. Each node will contain the information of its neighboring node (link is directional or bi-directional, node is cluster head or a member)

Ad-hoc Routing Protocols On-Demand Routing Protocol Cluster Based Routing Protocols Whenever a node enters a cluster, it broadcasts a “Hello” message. If cluster head listens to the message it will respond with a hello message. As soon as node gets this hello message from cluster head, the node will change its status from “undecided” to “member”. If no message is received and the link to its neighbor is bi- directional, this node will make itself a cluster head.

Ad-hoc Routing Protocols On-Demand Routing Protocol Cluster Based Routing Protocols Cluster A Cluster B Cluster C head

Ad-hoc Routing Protocols On-Demand Routing Protocol Ad-hoc On-Demand Distance Vector Routing (AODV) The aim of this routing protocol is to reduce the broadcasting messages. In order to find a destination path, the node sends the request to its neighboring node which forwards the request to its neighboring node and this process continues, till the destination is reached or a node is reached which contains the updated route information to the destination.

Ad-hoc Routing Protocols On-Demand Routing Protocol Ad-hoc On-Demand Distance Vector Routing (AODV) If a node has already seen a request packet, it will discard that request packet. The requests are kept up-to-date to avoid any loops. In this techniques, the nodes which are not on the selected path, do not maintain the routing table or do not participate in routing table exchanges.

Ad-hoc Routing Protocols On-Demand Routing Protocol Ad-hoc On-Demand Distance Vector Routing (AODV) AODV request packet path

Ad-hoc Routing Protocols On-Demand Routing Protocol Ad-hoc On-Demand Distance Vector Routing (AODV) AODV response packet path

Mobile Ad-hoc Networks (MANETs)

MANETs MANETs are self-organizing, infrastructure less network of device connected wirelessly to each other. In such networks, each device is mobile (free to move) in any direction. Each device has the capability to at least forward the information to the next nodes even if that information is not for that node. MANETs can be restricted to local area like laptops. MANETs are dynamic so that are not considered very secure.

MANETs A B C

Characteristics of MANETs Distributed Operation The control of the network is distributed amongst the nodes. No background infrastructure is required. Each node act as a router or a relay device. Nodes communicate with each other without instructions from a central device.

Characteristics of MANETs Multi-hop Communication If nodes are not in the range of each other, relay or router nodes can transfer the information from source to destination. These nodes forward packet to their immediate nodes till the destination is reached.

Characteristics of MANETs Dynamic Topology Nodes are free to move in any direction at any speed. Each node is free to communicate with any other node in the network. This results in change in topology dynamically at unpredictable time. These nodes are capable of establishing their own network since they can act as a Host or a router.

Characteristics of MANETs Shared Physical Medium Nodes share a same physical medium to be a part of a network. Nodes are required to have adequate resources and appropriate equipment. Communication technology for a medium can be Bluetooth or Wi-Fi etc.

Advantages of MANETs Self Organizing Less expensive because of no central device. Scalable Flexible Geographically independent, as the network can be set up at any place any time.

Limitations of MANETs Limited Bandwidth Routing overhead Hidden Terminal problem Packet loss Power constraints Less security

Routing Protocols of MANETs MANETS follow same routing protocols as Wireless Ad- hoc Networks Proactive Table Driven Reactive On-Demand Hybrid