Adhoc Networs

7/28/2019 Adhoc Networs

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Ad hoc Wireless Networks


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Mobile Ad hoc Networks Ad hoc Networks useful when infrastructure not available, impractical, or expensive

Do not need backbone infrastructure support

Are easy to deploy

military applications, rescue, home networking MANET

Host movement and Topology change frequent

Infrastructure may not be present in a disaster area or war zone

Infrastructure may not be practical for short-range radios; Bluetooth (range ~

10m) No cellular infrastructure. Multi-hop wireless links.

Data must be routed via intermediate nodes.

A

B AB


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MANET-Some Features Temporary network composed of mobile nodes without

preexisting communication infrastructure, such as Access

Point (AP) and Base Station (BS)- Each node plays the role

of router for multi-hop routing Self-organizing network without infrastructure networks

Each node decode-and-forward packets for other nodes

Multi-hop packet forwarding through wireless links


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Mobile Ad hoc Networks Ad Hoc Wireless Networks: multi-hop radio relaying and

without support of infrastructure

Wireless Mesh Networks

Wireless Sensor Networks


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EXAMPLE


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Comparison


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Comparison


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Applications Personal area networking

cell phone, laptop, ear phone, wrist watch

Military environments

soldiers, tanks, planes Civilian environments

taxi cab network

meeting rooms

sports stadiums

boats, small aircraft

Emergency operations

search-and-rescue

policing and fire fighting


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Wireless Mesh Networks An alternate communication infrastructure for mobile or fixed

nodes/users

Provides many alternate paths for a data transfer session

between a source and destination Advantages are High data rate, quick and low cost of

deployment, enhanced services, high scalability, easy

extendability, high availability, and low cost per bit


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Wireless Sensor Networks A collection of a large number of sensor nodes that are

deployed in a particular region

Differences with the ad hoc wireless networks

Mobility of nodes ( not mandatory),

size of network (larger)

density of deployment ( depends on application)

power constraints (more stringent than ad hoc)

data/information fusion ( for reducing delay of packets)

traffic distribution ( traffic pattern varies depends on applictaion)


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Challenges in Mobile Environments

Limitations of the Wireless Network

packet loss due to transmission errors

variable capacity links

frequent disconnections/partitions

limited communication bandwidth Broadcast nature of the communications

Limitations Imposed by Mobility

dynamically changing topologies/routes

lack of mobility awareness by system/applications

Limitations of the Mobile Computer

short battery lifetime

limited capacities


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Issues in Designing MANET

Medium access scheme Distributed operation

Synchronization

Hidden terminals

Exposed terminals

Throughput

Access Delay

Real time traffic support Resource reservation

Ability to measure resource availability

Power control

Use of directional antennas


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Routing Mobility

Bandwidth Constraint

Error prone shared medium

Location dependent contention

Other resource constraints

Requirements of a Routing protocol

Minimum route acquisition delay Quick route reconfiguration

Loop free routing

Distributed routing approach

Minimum control overhead Scalability

QoS

Security and privacy


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Multicasting

Robustness

Efficiency Control overhead

QoS

Efficient group management Scalability

Security


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TPC protocol

Setting up and maintain end to end delivery of

packets, flow control and congestion control Pricing scheme

Non optimal path consumes more resources and

affects throughput, wastes battery power and

energy of nodes

QoS

Per flow, per node per link basis.


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Self-organization

Neighbor discovery, topology organization. Topology

reorganization

Security

Denial of service, Information disclosure, Interference

Energy management

Transmission power management

Battery energy management

Processor power management

Device power management


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Addressing and service discovery

Scalability

Deployment considerations Low cost of deployment

Incremental deployment

Short deployment time

Reconfigurability


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Effect of mobility on the protocol stack

Application

new applications and adaptations

Transport

congestion and flow control

Network

addressing and routing

Link

media access and handoff

Physical

transmission errors and interference

Adhoc Networs

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