Lecture 1 mobile and adhoc network- introduction

Mobile & Ad Hoc Network

Chandra Prakash

Assistant Professor

LPU

1Chandra Prakash, LPU

Course Overview

Textbook:

• C. Siva Ram Murthy and B.S. Manoj, Ad Hoc Wireless

Networks: Architectures and Protocols , Pearson Education,

Inc.

• C.K Toh, Ad Hoc Mobile Wireless Networks, Pearson

Education, 2007

+ ( Research Papers literature)

Goal: Fundamental, design issues, solution to these issues–

architecture & protocol , developments in ad-Hoc Field


Related Sites

• Advanced Network Technologies Division, NIST,

– Wireless Ad Hoc Networks, http://w3.antd.nist.gov/wahn_home.shtml

• Autonomous Networks Research Group, USC

– WSN bibliography, http://ceng.usc.edu/~anrg/SensorNetBib.html

• IETF MANET WG

– http://www.ietf.org/html.charters/manet-charter.html

• IEEE 802 WG

– http://grouper.ieee.org/groups/802/dots.html

• Virtual lab

http://virtual-labs.ac.in/cse28/ant/ant/7/references/


http://w3.antd.nist.gov/wahn_home.shtml

http://ceng.usc.edu/~anrg/SensorNetBib.html

http://www.ietf.org/html.charters/manet-charter.html



http://grouper.ieee.org/groups/802/dots.html

http://grouper.ieee.org/groups/802/dots.html




Objectives of the Chapter

Introduction

Fundamentals of Wireless Communication Technology

The Electromagnetic Spectrum

Radio Propagation Mechanisms

Characteristics of the Wireless Channel

Evolution of mobile Cellular Networks

Generations of Cellular Mobile Communication

GSM, GPRS,CDMA ,PCS, UMTS

Wireless LANs, Wi-Fi

IEEE 802 Networking Standard

4 Chandra Prakash, LPU

We know

• What is NETWORK ?

• Type of Networks – Wired

– Wireless


Introduction

• Wireless Networking:

– refers to any kind of networking that does not involve cables.

• Wireless telecommunications networks are generally implemented

and administered using a transmission system called radio waves.

• This implementation takes place at the physical level (layer) of

the network structure


Some mobile devices

Clamshell handhelds

Tablets

Net–enabled mobile phones

Palm-sized

Laptop computers

Type of Networks

By Network Formation and Architecture

• Infrastructure-based network.

• Infrastructureless (ad hoc) network.

By Communication Coverage Area.

1. Wireless Wide Area Networks (Wireless WANs)

• Infrastructure-based networks

• Connections can be made over large geographical areas, across cities or even

countries

• Use of multiple antenna sites or satellite systems maintained by wireless service

providers.

• Examples :Cellular networks (like GSM networks or CDMA networks) and satellite

networks


Type of Networks 2. Wireless Metropolitan Area Networks (Wireless MANs).

– Referred as fixed wireless , infrastructure-based networks

– Enable users to establish broadband wireless connections among multiple locations ,for

example, among multiple office buildings in a city or on a university campus

– Serve as backups for wired networks

– Radio waves and infrared light can be used to transmit data.

3. Wireless Local Area Network (Wireless LANs)

– Enable users to establish wireless connections within a local area with in a 100 m range

– Provide flexible data communication systems that can be used in temporary offices or

other spaces that can operate in infrastructure-based or in ad hoc mode

– Include 802.11 (Wi-Fi) and Hiperlan2

4. Wireless Personal Area Networks (Wireless PANs).

– Enable users to establish ad hoc, wireless communication among personal wireless

devices such as PDAs, cellular phones, or laptops that are used within a personal

operating space, typically up to a 10 meter range.

– Two key Wireless PAN technologies are

• Bluetooth : is a cable-replacement technology that uses radio waves to transmit data

to a distance of up to 9–10 m,

• Infrared: connect devices within a 1 m range.9Chandra Prakash, LPU

Wireless Network Technology


Wireless Networks• Wireless Networks

– Infrastructured Network

• Cellular Network (3GPP or 3GPP2)

• Wireless LAN (IEEE 802.11)

– Infrastructureless Network

• Ad Hoc Network

11

Internet

WLAN

Cellular

[Mobile/Wireless] Ad Hoc NetworksChandra Prakash, LPU

Fundamental of Wireless Networks

Fundamentals of Wireless Communication Technology

where v is the speed of the wave (c in a vacuum, or less in other

media), f is the frequency and λ is the wavelength.






The Electromagnetic Spectrum Spectrum allocation

15Frequency bands and their common uses Chandra Prakash, LPU


Radio Propagation Mechanisms

Reflection

Diffraction

scattering



Characteristics of the Wireless Channel

Path loss

Fading

Interference

Doppler shift

Multiple Access Techniques

Frequency Division Multiple Access (FDMA)

Time division multiple access (TDMA)

Code division multiple access (CDMA)/Spread spectrum multiple

access (SSMA)

Space division multiple access (SDMA)


Frequency Division Multiple Access

• Available bandwidth is divided into multiple frequency channels/bands

• Frequency band are separated from each other by guard frequency band to

eliminated inter channel interference.

• But this result in under-utilization of frequency spectrum.

• FDMA can be used with both analog and digital signal.

• Eg: analog system for portable telephone and automobile telephone.

• Base station (BS) dynamically allocates a different carrier frequency to each node.

• To conserve energy at Mobile station (MS) the uplink frequency is always lower

than downlink frequency.


Time Division Multiple Access

• Share available bandwidth in the time domain (time slot/channels).

• Each node is assigned one or more time slots in each frame, and the node

transmits only in those slots.

• Guard intervals are introduced between time slot to prevent

synchronization error and inter-symbol interference.

• FDMA requires devices to have the capability of simultaneously receiving

and transmitting signals, which leads to increased cost.

• But in TDMA device can use same slot for transmitting and receiving

signals

• Used in GSM Global System for Mobile Communication


Time Division Multiple Access


Code Division Multiple Access• All users share the same frequency all the time

• Every channel uses the entire spectrum.

• Individual conservation are encoded with a pseudo-random digital

sequence.

• CDMA employs spread-spectrum technology and a special coding scheme

(where each transmitter is assigned a code) to allow multiple users to be

multiplexed over the same physical channel.

• CDMA was first used during World War II by English Allies.

• Two techniques

– Frequency Hopped Multiple Access (FHMA)

• The sender receiver change frequency (calling hopping) using the same pseudo-

random sequence, hence they are synchronized

– Direct Sequence Multiple Access (DSMA)

• In CDMA, the narrowband message signal is multiplied by a very large bandwidth

signal called spreading signal (code) before modulation and transmission over the

air.

• To pick out the signal of specific user, this signal is modulated with a unique code

sequence.


Difference in TDMA,FDMA and

CDMA

An analogy to the problem of multiple access is a room (channel) in

which people wish to talk to each other simultaneously. To avoid

confusion, people could take turns speaking (time division), speak at

different pitches (frequency division), or speak in different languages

(code division).

CDMA is analogous to the last example where people speaking the same

language can understand each other, but other languages are

perceived as noise and rejected. Similarly, in radio CDMA, each

group of users is given a shared code. Many codes occupy the same

channel, but only users associated with a particular code can

communicate.


Space division multiple access

• FDMA TDMA and CDMA transmits signal in all direction

(omnidirectional in nature )

• SDMA uses directional transmitters/antennas to over angular

regions.

• Different area/region can be served using the same frequency

channel.

• Best suited to satellite systems.

• Use spot beam antennas

• The different beam area can use TDMA, FDMA, CDMA

• Sectorized antenna can be thought of as a SDMA

• Adaptive antennas can be used in the future (simultaneously steer

energy in the direction of many users)


Space division multiple access

24

spot beam

antenna

SDMA controls the radiated energy for each user in space.

The different beam area can use TDMA, FDMA, CDMA

Chandra Prakash, LPU

Wireless Network Setup

• There are two types of wireless network types.

– Infrastructure

– Ad Hoc

Infrastructure

• Referred to as a “hosted” or “managed” wireless network.

• Consists of one or more access points (know as gateways or wireless

routers) being connected to an existed network.


Infrastructure Wireless Network


Ad-Hoc Wireless Network

• Also referred to as an “unmanaged” or “peer to peer” wireless

network

• it consists of each device connecting directly to each other.

• Allow someone sitting outside in the garden with a laptop to

communicate with his desktop computer in the house and access the

Internet.


The MANET problem

• MobileRandom and perhaps constantly changing

• Ad-hoc Not engineered

• NetworksElastic data applications which use networks to communicate


Motivation

Chandra Prakash, LPU 29

Terminology and Paradigms


Basics


Wireless Ad-hoc Network

• A wireless ad-hoc network is a decentralized type of wireless

network.

• The network is ad hoc because it does not rely on a pre-existing

infrastructure, such as routers in wired networks or access points in

managed (infrastructure) wireless networks. Instead,

each node participates in routing by forwarding data for other nodes,

and so the determination of which nodes forward data is made

dynamically based on the network connectivity.

• In addition to the classic routing, ad hoc networks can

use flooding for forwarding the data.


Mobile Ad-hoc Network

• Self-configuring network of mobile routers (and associated

hosts) connected by wireless links

• This union forms a random topology

• Routers move randomly free

• Topology changes rapidly and unpredictably

• Standalone fashion or connected to the larger Internet

• While MANETs are self contained, they can also be tied to an

IP-based global or local network – Hybrid MANETs

• Suitable for emergency situations like natural or human-

induced disasters, military conflicts, emergency medical

situations, etc.


Fundamental Concepts

• Ad hoc networks are autonomous networks operating either in

isolation or as “stub networks” connecting to a fixed network

• Do not necessarily rely on existing infrastructure

– No “access point”

• Each node serves as a router and forwards packets for other nodes in

the network

• Topology of the network continuously changes


Differences to other wireless

networks


Mobile Ad Hoc Networks (MANET)

36

Mobile nodes

Access points

Backbone

Wireless Mobile Network

MANET


Ad Hoc Networks vs. …

• Ad hoc networks vs. Wireless mobile networks

– Infrastructureless vs. Infrastructured Network

– All devices of an ad hoc network are likely to have similar constraints

• Ad hoc networks vs. Peer-to-peer networks

– P2P devices use existing networked structures such as Internet

– All P2P networks are not ad hoc network

• Because NOT all ad hoc network utilize an existing structure for the communication among devices


Ad hoc networks

• 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– Started from DARPA PRNet in 1970

• Cooperative nodes (wireless)– Each node decode-and-forward packets for other nodes

• Multi-hop packet forwarding through wireless links– Proactive/reactive/hybrid routing protocols

• Most works based on CSMA/CA to solve the interference problem– IEEE 802.11 MAC


Ad Hoc Network

39

Ad hoc networks

Mobile ad hoc networks(MANETs)

Wirelss Mesh Networks(WMN)

Wireless sensor networks

The application areas, the security requirements and the

constraints of the single devices differ …


Cellular Net vs. Ad Hoc Net


Cellular Net vs. Ad Hoc Net


Cellular and ad hoc wireless

networks.


Cellular and ad hoc networks.


Comparison of wireless cellular and wireless ad-hoc network

concepts


MANET ApplicationApplications Descriptions/Services

Tactical Networks •Military communication, operations

•Coordination of military object moving at high speeds such as fleets

of airplanes or ships

•Automated battlefields

Sensor networks •Collection of embedded sensor devices used to collect real time data

to automate everyday functions. Data highly correlated in time and

space, e.g., remote sensors for weather, earth activities; sensors for

manufacturing equipments.

•Can have between 1000 -100,000 nodes, each node collecting sample

data, then forwarding data to centralized host for processing using low

homogeneous rates.

Emergency

services

•Search, rescue, crowd control, and commando operations as well as

disaster recovery

•for e.g. Early retrieval and transmission of patient data ( record,

status, diagnosis ) from /to the hospital

•Replacement of a fixed infrastructure in case of earthquakes,

hurricanes, fire etc. 45Chandra Prakash, LPU

MANET Application

Applications Descriptions/Services

Commercial

environments

•E-commerce, e.g., electronic payments from anywhere (i.e., in taxi).

•Business:

dynamic access to customer files stored in a central location on

the fly provide consistent databases for all agents

Mobile office

•Vehicular services:

transmission of news ,road conditions ,weather, music

local ad hoc network with nearby vehicles for road/accident

guidance

Home and

enterprise

networking

•Home/office wireless networking(WLAN), e.g., shared whiteboard

application, use PDA to print anywhere, trade shows

•Personal area network (PAN)

Educational

applications

•Set up virtual classrooms or conference rooms

•Set up ad hoc communication during conferences, meetings, or

lectures46Chandra Prakash, LPU

MANET Application

Applications Descriptions/Services

Entertainment Multiuser games

Robotic pets

outdoor internet access

Location- aware

Services

Follow- on services, e.g., automatic call forwarding, transmission of the

actual workspace to the current location

Information services

push, e.g., advertise location-specific services, like gas stations

pull, e.g., location-dependent travel guide; services( printer, fax,

phone, server, gas stations) availability information; caches,

intermediate results, state information, etc.


Major Applications

• Military

• Emergency Service

• Collaborative and Distributed Computing

• Wireless Mesh Network

• Wireless Sensor Network

• Telematics

• Wireless Personal Area Network

• Home Network

• Ad Hoc Relay for Cellular Network

• Networks for ubiquitous computing

48

Demands for

group

communications


Military


Emergency Service


MANET – Overview

• MANET

– No infrastructure

– Self organizing networks

– Communications via mobile

nodes

– Dynamic topology

– Heterogeneity bandwidth-

constrained variable-capacity

links

– Limited physical security

– Nodes with limited battery life

and storage capabilities


Issues in Ad Hoc Networks

• Medium access scheme

• Routing

• Multicasting

• Transport layer protocol

• QoS provisioning

• Security

• Energy management

• Addressing and service discovery

• Scalability

• Deployment considerations
