gps, manets 2

Courtesy: Jean M

arie Zogg –u-blox and

uNA

V

Departm

ent of Information &

Com

munication Technology ,M

IT Manipal

GP

S and Inter Vehicular com

munications

Courtesy: Jean Marie Zogg – u-blox and uNAV

1.User wants to get a taxi from a Taxi service provider It is betterand cost effective if free taxi closest to theuser is sent . How canthis software solution be developed ?

2. Geocasting?

3.How can the aerial distance covered by a vehicle iscomputed?

4. How do you compute the speed of a Vehicle ?

Application


Global Navigation Satellite System

A satellite navigation system with global coverage may be termed a global navigation satellite system or GNSS.

As of April 2013, only the United States NAVSTAR Global Positioning System (GPS) and the Russian GLONASS are global operational GNSSs.

Other planned GNSS are Galileo(EU), Beidou(China) and GAGAN(India)

Applications of GNSSLocation-Based Services , Aviation, Maritime, Rail,


Assignment: Location Based Services

FourSquare - Users ”Check in” at a certain location, enabling social networking, Finding points of Interest and recommending places

Wikitude - Augmented reality application, adding information to Camera view on points of interest, tourist information

Find Me Maybe – Sends geo-localised SMS to Facebook and Twitter informing contacts of the user’s situation


Applications: Point of Interest search, person and object tracking, Emergency caller location,

Location based gaming, sport and Entertainment, Weather information and news

Application stores: Apple App store, Amazon App storeWindows phone store, Google Play,

Devices: smartphones, Tablets, Digital Cameras,

fitness and tracking Devices, Binoculars

Technology:: Cell ID, WI-FI,GNSS, INS

Location –based Services

Augmented RealityIndoor positioning

775000 in App store

700,000 in Android40% use the

location information

Integration of position ing into devices such as

Cameras, Watches, and Binoculars

GNSS Market Report


Aim at a glance


IntroductionGPS ( Global Positioning System )

¾ First satellite - 22nd February 1978, and there are currently 28 operational satellitesTwo values can be determined any where on Earth

9 One’s exact location (longitude, latitude and height co-ordinates) 9 The precise time (Universal Time Coordinated, UTC)

Development of the GPS system9 provide users with the capability of determining position,

speed and time

9 continuous, global, 3-dimensional positioning capability.9 Offer potential service to develop applications for civilian use.

w Full description is : NAVigation System with Timing And Ranging

Global Positioning System, NAVSTAR-GPS


Building block / Basic principle


Basic structure ¾ 28 satellites inclined at 55° to the equator on 6

different orbits.

¾ Takes 11 hours and 58 minutes to orbits the earth.

¾ Launched at a height of 20,180 km .

¾ Each satellite has up to four atomic clocks on board.

¾ Losing a maximum of one second every 30,000 to1 million years.

¾ They send exact position & clock signals to earth at 1575.42MHz. with the speed of light (300,000 km/s) Therefore require approx.67.3ms to reach a position on the Earth’s surface under it.

¾ compare the arrival time of the satellitesignal with the on board clock time the moment the signal was emitted.


Determining transit time


Determining position on a plane

¾ If the position above the satellites is excluded, the location of the receiver is at the exact point where the two circles intersect beneath the satellites.

¾ Two satellites are sufficient to determine a position on the X/Y plane.


Position in real environment

space consists of an extra dimension (height Z), an additional third satellite must be available to determine the true position.The position sought is at the point where all three surfaces of the spheres intersect as shown in the figure.Assumed that the terrestrial clock and the atomic clocks on board the satellites are synchronised.


First step in analyzing

¾ Need for synchronised clock.

¾ The transit time is out by just 1μs this produces a positional error of 300m.

¾ Mathematics need 4 equations for 4 unknowns :longitude (X)latitude (Y)height (Z)time error (Δt)

¾ Therefore follows that in three-dimensional space four satellites are needed to determine a position.


GPS, THE TECHNOLOGY

Divided into three segments to reduce the complexity

¾ space segment.¾ control segment.¾ user segment.


Space segment


Orientation of satellites


Satellite signalsThe following information (navigation message) is transmitted by the satellite at a rate of 50 bits per second:

9 Satellite time and synchronisation signals.9 Precise orbital data (ephemeris).9 Time correction information to determine the exact satellite time9 Approximate orbital data for all satellites (almanac).9 Correction signals to calculate signal transit time.9 Data on the ionosphere.9 Information about satellite health.

The time required to transmit all this information is 12.5 minutes.

The minimum amount of power received must not fall below -160dBW (max value is 14.9dB)

L1 carrier transmission power must be 21.9W


Generating the satellite signal¾ The following time pulses and frequencies required for day-to day operation

are derived from the resonant frequency of one of the four atomic clocks

9 The 50Hz data pulse.9 The C/A code pulse (Coarse/Acquisition code, PRN-Code, coarse reception

code at a frequency of 1023 MHz), which modulates the data using an exclusive-or . (this spreads the data over a 1MHz (bandwidth)

9 The frequency of the civil L1 carrier (1575.42MHz)

¾ PRN code serves as unique identifier is continually repeated and serves two purposes with regard to the receiver:

9 Identification.9 Signal transit time measurement.


Detailed block system


Control segment¾ Five monitor stations equipped with atomic clocks that are spread around

the globe in the vicinity of the equator.

¾ Three ground control stations that transmit information to the satellites.

¾ The most important tasks of the control segment are:

9 Observing the movement of the satellites and computing orbital data (ephemeris)

9 Monitoring the satellite clocks and predicting their behaviour

9 Synchronising on board satellite time

9 Relaying precise orbital data received from satellites in communication

9 Relaying the approximate orbital data of all satellites (almanac)

9 Relaying further information, including satellite health, clock errors etc.


User segment

The signals transmitted by the satellites take approx. 67 milliseconds to reach a receiver.Synchronising the signals generated in the receiver with those from the satellites, the four satellite signal time shifts Δt are measured as a timing mark.


The GPS Navigation Message

The navigation message is a continuous stream of data transmitted at 50 bits per second.

The navigation message is needed to calculate the current position of the satellite and to determine signal transit time.


Navigation Message

The navigation message is a bit stream of ones and zeros with a data rate of 50Hz.

Message is divided into frames.

Entire message is 25 frames.Each frame has 1500 bits = 30 seconds.


Navigation Frame

Each frame has a 5 sub frames.First 3 sub frames contain local data.

Last 2 subframes contain system data.


Subframe Data


Navigation Subframe

First 3 subframes repeat every 30 seconds.>Ephemeris and clock corrections.

Last 2 subframes repeat every 12.5 minutes. >Almanac and Ionospheric data.

Each subframe contains 10 words.>Starts with preamble (1000 1011),ends with a 0.

Each word contains 30bits=600ms>24 data bits and 6 parity bits.>Parity bits are the Hamming code for the word.


Subframe Data

All subframes start with the TLM and HOW .First word is the TeLeMetry word (TLM).>TLM contains an 8 bit preamble (1000 1011).

Second word is Hand Over Word (HOW).>HOW contains 17 bit Time of Week (TOW).>TOW is synchronized to beginning of next

subframe.>Contains ID of the subframe.


Z-count / GPS Time

GPS time begins midnight between January 5 and 6, 1980.The number of X1 epochs (1.5s) is a 29 bit number called Z-count.19 LSBs are the TOW-counts10 MSBs are the GPS week number (modulo 1024)Transmitted Z-count is truncated to 17 LSB


(Cont…)

First subframe contains Satellite clock correction terms and GPS Week number.Frames two and three contain precise ephemeris data.Frame four contains Ionospheric and UTC data as well as almanac for SVs 25-32.Frame five contains almanac for SVs 1-24 and almanac reference time.


Structure of the navigation message


Ephemeris and Almanac

Almanac data is course orbital parameters for all SVs. Each SV broadcasts Almanac data for ALL SVs. This Almanac data is not very precise and is considered valid for up to several months.Ephemeris data by comparison is very precise orbital and clock correction for each SV and is necessary for precise positioning. EACH SV broadcasts ONLY its own Ephemeris data. This data is only considered valid for about 30 minutes. The Ephemeris data is broadcast by each SV every 30 seconds.


Comparison between Ephemeris and Almanac Data

Ephemeris and Almanac


PRN Codes

PRN = Pseudo Random Noise� Codes have random noise characteristics but are precisely defined.

A sequence of zeros and ones, each zero or one referred to as a “chip”.� Called a chip because they carry no data.

Selected from a set of Gold Codes.� Gold codes use 2 generator polynomials.

Three types are used by GPS� C/A, P and Y


PRN CODE GENERATION


First 100 Bits of PRN1 and PRN22


Code Correlation

Correlation value� The number of bits between two codes that have the same value.

Autocorrelation� Correspondence between a code and a phase shifted replica of

itself.

Cross Correlation� Correspondence between a code and a phase shifted version of

another code (of the same length).


PRN Code Correlation


PRN Code Properties

High Autocorrelation value only at a phase shift of zero.

Minimal Cross Correlation to other PRN codes, noise and interferers.

Allows all satellites to transmit at the same frequency.

PRN Codes carry the navigation message and are used for acquisition, tracking and ranging.


C/A Code

C/A Code (Coarse Acquisition).� Uses 2 10-bit generator polynomials.� 1023 bits long.� 1 ms duration.� Clock rate of 1.023MHz.� Repeats indefinitely.� Also referred to as Civil Access code.

Only code needed for commercial receivers.


P-Code

PRN codes used by the military.

Uses different generator polynomials.

15,345,037 bits long.

Has a duration of 7 days.

Clock rate of 10.23MHz

Y-Code� Replaces P-Code when anti-spoofing is enabled (encrypted).

Not necessary for positioning


Signal Structure

L1 carrier� 1575.42 MHz, ~19 cm wavelength� Modulated by both the C/A and P(Y) codes.� P(Y) code is 90 degrees out of phase from the C/A code.

L2 carrier� 1227.60 MHz, ~24 cm wavelength� Modulated by the P(Y) code only

Both carriers are centered in 20.46 MHz wide protected band


Signal Composition

Navigation message� Bit stream with data rate of 50bps.

C/A code� Bit stream with a data rate of 1.023 mega chips per second.

L1 Carrier� Sine wave with a frequency of 1.57542 GHz.

L2 carrier and P(Y) codes will be primarily ignoredfor the remainder of this tutorial.


Combining Navigation Message with the C/A Message

Navigation message is modulo 2 added to C/A code.20 C/A codes per Navigation Bit.


Data Collection Times

Cold start� No prior information – requires blind search� Up to 36 seconds starting after acquisition of the 4th satellite.

Warm start� Have almanac or old ephemeris and approximate position –

speeds up search� Up to 36 seconds after the 4th satellite.

Hot start� Have valid ephemeris and approximate position� Up to 6.6 seconds to collect valid data (1 subframe).


Elevation & Azimuth Angle

Azimuth and elevation are angles used to define the apparent position of an object in the sky, relative to a specific observation point. The observer is usually (but not necessarily) located on the earth's surface.


Error Sources


Error consideration

In GPS system, several causes may contribute to the overall error:1. Satellite clocks2. Satellite orbits3. Speed of light4. Measuring signal transit time5. Satellite geometry


System Errors

Satellite clock� Errors in modeling of the satellite clock offset and drift using a

second order polynomial� Selective Availability

Satellite orbit� Errors that exist within the Keplerian representation of the

satellite ephemeris� Selective Availability


Ionospheric Errors

70 – 1000 km above the earth

Dispersive medium affects the GPS signals� Carrier experiences a phase advance� Codes experience a group delay

Delay is dependent on the total electron count (TEC)� Peaks during day due to solar radiation� Varies with geomagnetic latitude� Varies with satellite elevation


Ionospheric Errors

Frequency dependent� Can be eliminated with dual frequency receivers (L1/L2)

Reduce errors using Klobuchar model� Eight parameters are transmitted in the navigation message� Combined with an obliquity factor dependant on the satellite

elevation� Provides an estimate within 50% of the true delay


Trophospheric Errors

0-70 km above the earth

Delays both code and carrier measurements

Not frequency dependent within L band

Can be modeled� Dry component, 90% of the total refraction� Wet component, 10% of the total refraction� Temperature, pressure and humidity� Satellite elevation angle


Ideal Satellite GeometryN

S

W E


Dilution Of Precision (DOP)

Good DOP


Good Satellite Geometry


Dilution Of Precision (DOP)

Good DOP


Poor Satellite GeometryN

S

W E


Poor Satellite Geometry


Dilution Of Precision (DOP)Poor DOP


Poor Satellite Geometry


Dilution Of Precision (DOP)Poor DOP


Dilution Of Precision

GDOP = Geometric Dilution Of Precision (based on 4 co-ordinates)PDOP = Position Dilution Of Precision (based on 3 co-ordinates)VDOP = Vertical Dilution Of Precision (altitude)GDOP = Geometric Dilution Of Precision HDOP = Horizontal Dilution Of Precision (latitude, longitude)TDOP = Time Dilution Of Precision (time)

QUALITY DOPIdeal 1Excellent 2-3Good 4-6Moderate 7-8Fair 9-20Poor 21-50


DATA FORMATS AND HARDWARE INTERFACES


Introduction

GPS receiver requires different signals in order to function. These variables are broadcast after position and time have been successfully calculated and determined. International Standard formats data exchange ¾ NMEA (National Marine Electronics Association)¾ RTCM (Radio Technical Commission for Marine Services)


Block Diagram of GPS Receiver


Data Interfaces

NMEA – 0183 data interfaceIn order to relay computed GPS variables such as

position, velocity, course etc to a peripheral, GPS modules have serial interface( TTL or RS-232). The data is passed in a format standardised by the NMEA. NMEA – 0183 specification is the recently used.


Data SetsThe following are the data sets used in GPS

modules. � GGA (GPS Fix Data, fixed data for Global Positioning System)� GGL (Geographical Positioning – Latitude/Longitude)� GSA (GNSS DOP and Active Satellite)� GSV (GNSS satellite in view)� RMC (Recommended Minimum Specific GNSS data)� VTG (Course over Ground and Ground Speed)� ZDA (Time and Data)

Data Interfaces


Data InterfacesStructure of NMEA protocol

The rate at which the data is transmitted is 4800 baud using printable 8 bit ASCII character. Transmission begins with a start bit (logical zero), followed by eight bit data and a stop bit (logical one) added at the end. No parity is used.


Data Formats

Description of Individual NMEA DATA SET blocks


1. GGA DATA SET: The GGA dataset (GPS Fix Data) containsinformation on time, longitude and latitude, the quality of thesystem, the number of satellites used and the height.

Example : $GPGGA,130304.0,4717.115,N,00833.912,E,1,08,0.94,00499,M,047,M,,*59<CR><LF>

Data Formats

Courtesy: Jean Marie Zogg – u-blox and uNAVGGA Data Set Blocks


2. GLL Data Set: The GLL data set (geographic position latitude / longitude)

contains information on latitude and longitude, time And health.Example:$GPGLL,4717.115,N,00833.912,E,130305.0,A*32<CR><LF>

GGL Data Set Blocks


3. GSA Data Set:The GSA dataset (GNSSDOP and Active Satellites) contains

information on the measuring mode (2D or 3D), the number ofsatellites used to determine the position and the accuracy of themeasurements (DOP:Dilution of Precision).

Example :$GPGSA,A,3,13,20,11,29,01,25,07,04,,,,,1.63,0.94,1.33*04<CR><LF>

Courtesy: Jean Marie Zogg – u-blox and uNAVGSA Data Set Blocks


4. GSV Data Set :The GSV Data set (GNSS Satellite in View) contains

information on the number of satellite in view, theiridentification, their elevation and azimuth, and the signalto-noise ratio.

Example :$GPGSV,2,2,8,01,52,187,43,25,25,074,39,07,37,286,40,04,09,36,33*44<CR><LF>

Courtesy: Jean Marie Zogg – u-blox and uNAVGSV Data Set Blocks


5. RMC Data set :The RMC (Recommended minimum Specific GNSS) contains

information on time, latitude, longitude and height, system status,speed, course and date. This data set is relayed by all GPSreceiver.

Example : $GPRMC,130304.0,A,4717.115,N,00833.912,E,000.04,205.5,20601,01.3,W*7C<CR><LF>

Courtesy: Jean Marie Zogg – u-blox and uNAVRMC Data Set Blocks


6. VTG Data set :The VTG data set (Course over ground Speed) contains

information on course and speed.

Example :$GPVTG,014.2,T,015.4,M,000.03,N,000.05,K*4F<CR><L>


VTG Data Set Blocks


7. ZDA Data Set : The ZDA data set (time and date) contains information

on UTC time, the date and local time.

Example :$GPZDA,130305.2,20,06,2001,,*57<CR><LF>


ZDA Data Set Blocks


Calculating Checksum : The checksum is determined by an exclusive-or

operation involving all 8 data bits (excluding start andstop bits) from all transmitted characters, includingseparators. It starts at ($ sign) and ends beforechecksum separator (asterisk *).

The 8-bit result is divided into 2 sets of 4 bits (nibble) andeach nibble is converted into hexadecimal value.


Example : $GPRTE,1,1,c,0*07


DGPS correction data (RTCM SC – 104)

DGPS Correction Data (RTCM SC - 104) : The Radio Technical Commission Marine services Special Committee –

104 standard is used to transmit correction values.

The two versions of RTCM is¾ Version 2.0 (Jan 1990)¾ Version 2.1 (Jan 1994)

Both the message types are divided into 63 message types, numbers 1, 2, 3 and 9 being used primarily for correction based on code measurements.


Differential GPS


DGPS Site

x+30, y+60

x+5, y-3

True coordinates = x+0, y+0 Correction = x-5, y+3

DGPS correction = x+(30-5) and y+(60+3)True coordinates = x+25, y+63

x-5, y+3

DGPS ReceiverReceiver

Real Time DGPS


National Differential Global Positioning System

Yellow areas show overlap between NDGPS stations. Green areas are little to no coverage. Topography may also limit some areas of coverage depicted here.

NDGPS Ground Stations


RTCM Message HeaderRTCM Message Header :

Each message type is divided into words of 30 bits and, ineach instance, begins with a uniform header comprising twowords (WORD 1 and WORD 2)


The hardware interfaces areAntennaPower SupplyTime pulse

Antenna : GPS modules can either be operated with a passive or active antenna. Active is one with built in amplifier (LNA: Low Noise Amplifier) are powered from the GPS module.

Hardware Interfaces


There are two types of antenna 1. Patch Antenna: Patch antenna are flat, generally have a ceramic and metallised body are mounted on the metal plate. Often cast in housing.

Hardware Interfaces


2. Helix Antenna: Helix antenna are cylindrical in shape and have higher gain than patch antenna.


Supply : GPS module must be powered from an external voltage source of 3.3vto 6 Volts.

Time Pulse: 1PPS and Time SystemsMost GPS modules generate a time pulse every second, referred to as 1 PPS(Pulse per second), which is synchronized to UTC.

The time pulse can be used to synchronize communication networks (precision Timing).

The Five Important Time Systems are

1. Atomic time (TAI) : The international time scale was introduced in order to provide auniversal ‘absolute’ time scale that would meet various practical demands and at the sametime also be of significance for GPS positioning.


2. Universal time co-ordinated (UTC) :UTC was introduced, in order to have a practical time scale that was oriented

towards universal atomic time and, at the same time, adjusted to universal co-ordinated time.

3. GPS time :General GPS system time is specified by week number and the number of

seconds within that week. Each GPS week starts in the midnight from Saturday to Sunday. The continuous clock being set by the main clock at the Master Control Station.

4. Satellite time :Because of constant, irregular frequency errors in the atomic clocks in board

the GPS satellites time is at variance with GPS system time. The satellite clocks aremounted by control station and apparent time difference relayed to earth.

5. Local time: Local time is referred within a certain area.

The relationship of the time systemsTAI – UTC = +32secGPS – UTC = +13secTAI – GPS =+19sec


Zulu Time

Military Time(local time on a 24 hour clock)

Universal Coordinated Time

Greenwich Mean Time

Local Time: AM and PM (adjusted for local time zone)

GPS Time - 14*

* GPS Time is ahead of UTC by approximately 14 seconds(2007)

What Time is It?

Courtesy: Jean M


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essageincludes

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Applications

Many civilian applications benefit from GPS signals, using one or more of three basic components of the GPS: absolute location, relative movement, and time transfer. The ability to determine the receiver's absolute locationallows GPS receivers to perform as a surveying toolor as an aid to navigation.


Applications

The capacity to determine relative movement enablesa receiver to calculate local velocity and orientation,useful in shipsBeing able to synchronize clocks to exacting standardsenables time transfer, which is critical in largecommunication and observation systems. An exampleis CDMA digital cellular. Each base station has a GPStiming receiver to synchronize its spreading codes withother base stations to facilitate inter-cell hand off andsupport hybrid GPS/CDMA positioning of mobiles foremergency calls and other applications


The Wide Area Augmentation System (WAAS) is an air navigation aidby the Federal Aviation Administration to augment the Global PositioningSystem (GPS) to provide additional accuracy, integrity, and availability.

WAAS enables users to rely on GPS for all phases of flight, includingduring precision approaches to any airport within its coverage area.

WAAS uses a network of ground-based reference stations to monitor andmeasure the GPS satellite signals. Measurements from the referencestations are routed to master stations, which generate and send thecorrection messages to geostationary satellites. Those satellitesbroadcast the correction messages back to Earth, where WAAS-enabledGPS receivers apply the corrections while computing their position.The International Civil Aviation Organization (ICAO) calls this type ofsystem a Satellite Based Augmentation System (SBAS). Europe and Asiaare developing their own SBASs


Geostationary WAAS satellites

GPS Constellation

WAAS Control Station (West Coast)

Local Area System (LAAS)

WAAS Control Station (East Coast)

Wide Area Augmentation System


+ -3 meters

+-15 meters

With Selective Availability set to zero, and under ideal conditions, a GPS receiver without WAAS can achieve fifteen meter accuracy most of the time.*

Under ideal conditions a WAAS equipped GPS receiver can achieve three meter accuracy 95% of the time.*

* Precision depends on good satellite geometry, open sky view, and no user induced errors.

How Good is WAAS ?


Galileo Satellite based positioning system

�Global Navigation Satellite System, to be built by the European Union (EU) and European Space Agency (ESA).

�The €20 billion project is an alternative and complementaryto the U.S. Global Positioning System NAVSTAR (GPS)and the Russian GLONASS.

Courtesy: Jean M


uNA

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Why G

alileo?

GLO

NA

SS is not fully operationalN

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STAR

is fully under US m

ilitary controlU

S Defense m

aintains a Selective Deniability (SD

) which

may be used to effectively jam

civilian GPS units

Poor coverage of higher latitudes.

Courtesy: Jean M


uNA

V

Objectives of G

alileo

More

precisem

easurements

toall

usersthan

availablethrough

GPS

orGLO

NA

SS,

Betterpositioning

servicesathigh

altitudes.Independent

positioningsystem

uponw

hichEuropean

nationscan

relyeven

intim

esof

war

orpolitical

disagreement.

Courtesy: Jean M


uNA

V

Galileo satellites

•30 spacecrafts

•orbital altitude: 23 222 km

•3 orbital planes, 56°inclination (9 operational satellites and one active spare per orbital plane)

•satellite lifetim

e: >12 years•

satellite mass: 675 kg

•satellite body dim

ensions: 2.7 m x 1.2 m

x 1.1 m•

span of solar arrays: 18.7 m•

power of solar arrays: 1500 W

Courtesy: Jean M


uNA

V

Galileo Satellites in orbit

Courtesy: Jean M


uNA

V

A G

ALILE

O S

ATE

LLITE

Courtesy: Jean M


uNA

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International Partners

•IN

DIA

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A•

ISR

AE

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UK

RA

INE

•M

OR

OC

CO

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AU

DI A

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OU

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nd still counting

Courtesy: Jean M


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SE

RV

ICE

S

Open S

ervice (OS

)

Com

mercial S

ervice (CS

)

Public R

egulated Service (P

RS

)

Safety of Life S

ervice (SoL)

Courtesy: Jean M


uNA

V

Open Service

Free for anyone to accessB

roadcast in two bands, at 1164–1214 M

Hz and at 1563–

1591M

Hz.

Receivers w

ill achieve an accuracy of <4 m horizontally and

<8 m vertically if they use both O

S bands. R

eceivers that use only a single band will still achieve <15 m

horizontally and <35 m

vertically, comparable to w

hat the civilian G

PS C/A

service provides today. It is expected that m

ost future mass m

arket receivers, such as autom

otive navigation systems, w

ill process both the GPS C

/A

and the Galileo O

S signals, for maxim

um coverage.

Courtesy: Jean M


uNA

V

Com

mercial S

ervice (CS

)

Itwillbe

availablefora

feeand

willofferan

accuracyofbetterthan

1m

.The

CS

canalso

becom

plemented

byground

stationsto

bringthe

accuracydow

nto

lessthan10

cm.

Thissignal

will

bebroadcast

inthree

frequencybands,the

two

usedfor

theO

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wellas

at1260–1300

MH

z.

Courtesy: Jean M


uNA

V

Public R

egulated Service (P

RS

)

Provide an accuracy com

parable to the Open S

ervice.M

ain aim is robustness against jam

ming

Reliable detection of problem

s within 10 seconds.

Targeted at security authorities (police, military, etc.)

Courtesy: Jean M


uNA

V

Safety of Life S

ervice (SoL)

providean

accuracycom

parableto

theO

penService.

robustnessagainst

jamm

ingand

thereliable

detectionofproblem

swithin

10seconds.

safety-criticaltransport

applications(air-traffic

control,autom

atedaircraft

landing,etc.),

respectively.

Courtesy: Jean M


uNA

V

GA

LILEO

will offer satellite

positioning services to everyone everyw

here with

guaranteed reliability.

Individuals, companies,

tourists administrations w

ill all be able to find their w

ay on the roads, railw

ays, in the skies or at sea.

It will enhance the search

and rescue operations.

APPLICATIONS

Courtesy: Jean M


uNA

V

Sectors that will benefit

•Transport

•E

nergy•

Telecom•

Civil P

rotection•

Rail

•Insurance

•A

viation•

Civil E

ngineering•

Agriculture

•M

aritime

•S

afety•

Environm

ent

Courtesy: Jean M


uNA

V

Benefits to the Energy Sector

•B

y integrating GA

LILEO w

ith other technologies, the energy com

munity can benefit from

:-Im

proved control of energy infrastructures-Im

proved power flow

-Improved tim

e-synchronization of power-related

instruments

-Increased safety and efficiency in oil exploration-Im

proved control of drilling facilities-Tim

ely decision-making thanks to faster positioning

information, even in rem

ote areas

Courtesy: Jean M


uNA

V

Conclusion

Coupled

with

thealready

existingU

.S.N

AV

STAR

system,

GA

LILEOw

ouldresultin

GPS

usershaving

accessto

almost

75satellitesforhighly

accuratenavigation

andpositioning.

Thesedevelopm

entshave

many

potentialadvantages

forthe

datacollection

aspectsforGPS

usersforthe

developmentofnew

applicationsusingG

PSw

orldwide.

Potentialareasof

growth

usingthese

coupledsystem

sw

illbeassociated

with

newapplications,

hardware

andsoftw

are,analysis

techniquesand

willrequire

additionaltrainingforG

ISprofessionals.

Courtesy: Jean M


uNA

V

Inter-Vehicular C

omm

unication

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

.A G

PS

fitted, aerial vehicle moves from

Le Harve to Lyon. W

hen the vehicle started at Le H

arve, the readings on the GP

S receiver w

ere(* indicates degrees)49*28’33.91’’ N0* 4’06.70” EA

ltitude = 30 Meters

The vehicle when landed in the Lyon, the G

PS

readings were

45*44’57.23”N

4*49’28.17” EA

ltitude –120 M

eters C

ompute the D

istance covered by the Vehicle.

Given x = alt * cos(long) * sin(90 deg –

lat)y = alt * sin(long) * sin(90 deg –

lat)z = alt * cos(90 deg –

lat)

Courtesy: Jean M


uNA

V

•Component of Intelligent Transportation System

(ITS)•O

ne of the concrete applications of MA

NE

TS-VAN

ETs

Motivation

•Improves road safety and efficiency by increasing the horizon of drivers

and on-board devices•Transm

ission of road-side information about em

ergencies, congestion, etc.

•Ability for inter-driver com

munication

•Existing ad hoc networks protocols and experiences can actually be put

to practice

Inter vehicular Comm

unication:

Courtesy: Jean M


uNA

V

Groups &

Applications

•Association of E

lectronic Technology for Autom

obile Traffic and D

riving (JSK), Japan -early 1980’s

•CarTALK

, EU

-2000•FleetN

et, Germ

any -2000•PA

TH, California

•Chauffeur, EU

•DE

MO

2000, Japan

Groups &

Applications

Courtesy: Jean M


uNA

V

IVC

–M

ain Applications

Information and W

arning FunctionsD

issemination of road inform

ation to distant vehicles

Comm

unication-based Longitudinal ControlE

xploiting “look-through” capacity to avoid accidents, platooning vehicles, etc.

Co-operative Assistance System

sCoordinating vehicles at critical points

Added-value A

pplicationsInternet access, Location-based services, M

ultiplayer games

Courtesy: Jean M


uNA

V

•Both infrared and radio waves have been studied and em

ployed•Radio w

aves: VH

F, micro, and m

illimeter w

aves•V

HF and m

icrowaves are of broadcast type

•Dedicated Short Range Com

munication (D

SRC) spans 75MH

z ofspectrum

in the 5.9 GH

z band•D

EM

O 2000, Chauffeur used 5.8 G

Hz D

SRC•CarTA

LK, FleetN

et use ULTRA

TDD

•JSK, PA

TH, CarTA

LK have used infrared, typically for cooperative

driving

Radio Frequency S

pectrum

Courtesy: Jean M


uNA

V

Definition: W

ireless Netw

orks

Refers

tothe

useof

infraredor

radiofrequency

signalsto

shareinform

ationand

resourcesbetw

eendevices

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

Definition: W

ireless Ad hoc N

etworks

isa

Com

puterN

etwork

inw

hichthe

comm

unicationlinks

arew

ireless.Thenetw

orkis

Adhoc

becauseeach

nodeis

willing

toforw

arddata

forother

nodes,and

sothe

determination

ofw

hichnodes

forward

datais

made

dynamically

basedon

thenetw

orkconnectivity

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

Routing In A

dhoc networks(M

AN

ET)

Courtesy: Jean M


uNA

V

Routing in W

ire Net

Link State

Distance Vector

Will it W

ork for M

ANET??

Courtesy: Jean M


uNA

V

Structural differences b/w

Wired &

Wireless

WIR

ELE

SS

WIR

ED

Sl.No

Rate of topology

changeH

igh, due to mobility of

nodes etc.Very less, since nodes are stationary. N

ormally event

driven.

1

Quality of Link

Less predictable, fluctuates considerably depending on netw

ork and environmental

conditions.

Stable w

hen compared

to wireless N

etworks

2

Link TypeW

ireless Links can be asym

metric and

unidirectional.

Sym

metric and bidirectional

3

Courtesy: Jean M


uNA

V

Structural differences b/w

Wired &

Wireless

WIR

ELE

SS

WIR

ED

Sl.No

Broadcast

transmissions

Unreliable

Does not exist

4

Usage of resources -

battery power,

transmission

bandwidth, C

PU

tim

e

Presents technological

limitations on usage of

resources

Does not present m

ore technological lim

itations w

hen compared to

wireless netw

orks.

5

Security

Weak. D

ue to the nature of radio transm

issions, in the absence of any authentication m

echanism, a

malicious node can easily corrupt

route tables etc. Advertise false route

information.

Much better than

wireless N

etworks.

6

Courtesy: Jean M


uNA

V

How M

ANET different?

Bandw

idth constraint

Pow

er constraint

Short radio range (150-200 m

eter)

High m

obility -> no fixed route

Courtesy: Jean M


uNA

V

Why W

ired-solution not Work?

Link State:

�E

ach node must know

whole topology

�Flooding of inform

ation for high mobility

�R

equire consistency in the RIB

Distance V

ector:�

Maintain com

plete list of routes �

Broadcast create high overhead for high m

obility�

Count to infinity, routing loop, convergence tim

e

Courtesy: Jean M


uNA

V

Constraints in M

obile Ad-H

oc Netw

orks Inform

ation about network flow

s is typically not available in datagram

networks.

Netw

ork topology can vary rapidly.

Incremental delay and residual capacity, change m

ore quickly than the physical topology.

Even if a radio generates tim

ely routing information that reflects

changes in delay and capacity, the delay in propagating that inform

ation throughout the network m

ay be such that the information

is stale by the time it reaches a distant node.

Incremental delay and residual capacity of a radio link are affected

by the traffic being carried on other radio links.

Courtesy: Jean M


uNA

V

Routing and M

obility Managem

ent in Infrastructure Wireless N

/W’s

Mobility M

anagement

-consists of set of mechanism

s by which location

information is updated in response to term

inal mobility.

Location tracking consists of 2 operations

-Updating (R

egistration)--The process by w

hich a mobile endpoint initiates a

change in the location database according to its new

location.

-Finding (Paging)

--The process by which the netw

ork initiates a query for an endpoint’s location to update the location databases.

Courtesy: Jean M


uNA

V

Routing and M

obility Managem

ent Contd…

.

For Wired E

nvironments

-Routing paths are fixed since term

inals are static.-Location tracking is not required

For Infrastructure Wireless N

etworks

-Endpoint m

obility within designated area is

transparent to the network.

-Location tracking is required when an endpoint

moves from

one domain to another.

Courtesy: Jean M


uNA

V

Updating the location database

Two strategies are used for updates.-S

tatic update strategy-D

ynamic update strategy

Static update strategy

-Consists of predeterm

ined set of areas in which

location updates may be generated.

-Location update is generated only when endpoint

enters one of these cells.

Courtesy: Jean M


uNA

V

Static updating strategy in detail

Two approaches are used in updating.

-Location areas-Reporting cells

Location areas

-Also referred as paging or registration areas

-Service area is partitioned into group of cells.

-Each group is a location area.

-Endpoint’s position is updated if and only if it changes location areas.

-When an endpoint needs to be located, paging is done over the

most recent location area visited by endpoint

Courtesy: Jean M


uNA

V

Static update strategy Contd…

.

Reporting C

ells

-Subset of cells is designated as the only one from

w

hich the endpoint location may be updated.

-When an endpoint needs to be located , search is

conducted in the vicinity of the reporting cell, from

which the m

ost recent update was generated.

Draw

backs of static update strategy

-D

o not accurately account for user mobility and

frequency of incoming calls.

Courtesy: Jean M


uNA

V

Updating location database C

ontd…D

ynamic update strategy

-Update is generated by the endpoint based on its

movem

ent.-

Update m

ay be generated in any cell.

Three dynamic strategies are described in w

hich an endpoint generates a location update.

-E

very T seconds (time based)

-A

fter every M cell crossings (m

ovement based)

-W

henever the distance covered (in terms of num

ber of cells) exceeds D

(distance based).

Courtesy: Jean M


uNA

V

Location tracking in Internet

Mobile IP

-Protocol standardized by IE

TF -P

rovides support for mobile hosts in internet

-Mobile nodes are allocated perm

anent IP addresses

in home netw

ork.-M

obile nodes are allocated new tem

porary forwarding

addresses as it moves to a foreign netw

ork.

Two w

ays of obtaining forwarding address

-Through the foreign agent in the visited network.

-Address discovery protocol such as D

HC

P.

Courtesy: Jean M


uNA

V

Location tracking in internet Contd…

.

Data transfer

-A node w

ishing to send a message to a m

obile node sends the m

essage to the permanent

address of the node.

-If the mobile node is in the foreign netw

ork (roam

ing away from

home netw

ork), the message

is encapsulated and tunneled to its new location.

Courtesy: Jean M


uNA

V

Routing and M

obility Managem

ent in Mobile W

ireless N/W

s

In mobile netw

orks with m

obile infrastructure, such as mobile radio

networks, com

munication term

inals are free to move, causing frequent

change in routing paths.

Mobiles m

ust keep track of each others locations and interconnectivity as they m

ove.

Mobility m

anagement in M

ANE

T involve 3 mechanism

s.R

oute discovery -Initially m

obile node consults its route cache for the presence of route.

-If the unexpired route to the destination does not exist, initiates route discovery procedure.

-D

iscovery procedure is completed w

hen one or more routes

are found or all possible route permutations are exam

ined.

Courtesy: Jean M


uNA

V

Routing and M

obility Managem

ent in Mobile W

ireless N/W

s

Route selection

-Considers local or global inform

ation about the network

state in selecting the next hop to the destination.

Route M

aintenance

-R

esponsible for reacting to topological changes in the netw

ork so that in the event of a link failure the affected data sources are inform

ed.-

Error in the link m

ay be repaired locally at the point of failure w

ith no further notification to affected source node.

Courtesy: Jean M


uNA

V

Route D

iscovery

Three components are considered

-Source N

ode-

Intermediate N

odes-

Destination N

ode

Source N

ode

-Broadcasts (flooding) a query (R

oute Request) packet in

order to discover the route to the destination.-The packet is flooded through the netw

ork.

Courtesy: Jean M


uNA

V

Route discovery C

ontd….

Intermediate N

odes

-Helps in propagating the requests if

--The request has not been forwarded previously.

--The node is not the destination of the searching procedure.

-Extracts reachability inform

ation for the source node on receiving the route request.

--This is accomplished by using the m

obile node from w

hich the query w

as obtained, as the next hop to reach the source node.

Courtesy: Jean M


uNA

V

Route D

iscovery Contd…

.D

estination Node

-On reception of query packet, a route reply m

essage is sent back to the source indicating the route to destination.

Route reply travels in the reverse direction of the

discovered route.

-Each interm

ediate node maintains route request table.

-When a node receives a route reply, the m

atched route request is retrieved from

the route request table.-The route reply is then forw

arded to the node (Source

node) from w

hich the initial route request message w

as received.

Route reply contains route-cost inform

ation

Courtesy: Jean M


uNA

V

Route D

iscovery ….

Recipients can select routes based on specific costs.

Each recipient of the route reply m

ay update its route to the destination using as next hop to the node from

which

the reply is obtained.

A node m

ay also maintain m

ultiple routes to other nodes, but route acceptance shall be done in a w

ay as to guarantee freedom from

loops.

Courtesy: Jean M


uNA

V

Optim

izations to flooding-based route searching

Two m

echanisms are used for an efficient route discovery m

echanism

that reduces the excessive overhead induced by flooding.

-Query quenching

-Expanding ring search

Query quenching

-Intermediate nodes on receiving the route query, m

ay them

selves reply to the query by sending a route reply message

back to the source on behalf of destination, given that they m

aintain valid routing information for the destination in search.

Courtesy: Jean M


uNA

V

Advantages &

Disadvantages of Q

uery quenching.

Advantages of Query quenching

-Early quenching of the route search stops the spreading of the

query flooding at some interm

ediate node.

-To a large extent query quenching may reduce the route

discovery overhead and inherent route acquisition latency.

Disadvantages of Query quenching

-S

ince the route requests are not broadcasted end-to-end, the route constructed by the m

echanism m

ay not always be the optim

um routes.

-The source node may be prevented from

discovering the better route even if one exists.

-When up to date end-to-end inform

ation is required in proper route selection (such as end-to-end bandw

idth availability, individual node energy reserve) , query quenching is not a desired option.

Courtesy: Jean M


uNA

V

Optim

izations to flood based route searching

Expanded Ring Search-

Several route discovery attem

pts of limited scope are m

ade before a flooding is triggered.

-At each attem

pt the searching scope is increased by some factor.

-Process continues until

--searching scope reaches maxim

um threshold after w

hich query is flooded.

Or

--The node in search is successfully located

Drawbacks

-Increase in route discovery latency when the initial attem

pt to discover a route fails and a new

route discovery cycle is initiated.

Courtesy: Jean M


uNA

V

Route S

election and forwarding

In wired netw

orks shortest path routing is preferred for packet forw

arding.

In wireless m

obile networks shortest path routing is not

preferred since it does not differentiate between good

links and bad links.

In wireless m

obile networks a path w

ith many forw

arding hops m

ay have better links and thus be of higher quality than a path w

ith fewer, but w

orse-in-quality, links.

Courtesy: Jean M


uNA

V

Route M

aintenance

Route M

aintenance

-It’sthe

mechanism

thatdetectswhetherthe

network

topologyhas

changedsuch

thatadata

pathisno

longerviableand

routereconstruction

isrequired.

Detection of Broken Link

-Mechanism

similarto

beaconingprotocolsisused.

-During

thepropagation

ofdatatraffic

eachforw

ardingnode

sendsalink

layeracknowledgem

enttothe

previoushopnode,confirm

ingthe

packetreception.-Ifthe

nodedoesnotreceive

thelink

layeracknowledgem

entfromthe

nexthopnode

aftertransmitting

packetsin

maxim

umnum

beroftim

es,itindicatesthelink

isbroken.

Courtesy: Jean M


uNA

V

Route M

aintenance Contd…

.

Informing the source node about the broken route.

-R

oute error message is sent by a node that detects the

broken route, to the source node.

At the source Node

-The source Node after receiving the route error m

essage, rem

oves the broken link from the cache.

-If the source node has another route to the destination in its route cache, it sw

itches the flow over the new

route im

mediately, else it m

ay invoke a route discovery to find the new

route.

Courtesy: Jean M


uNA

V

MANET Routing Decisions

Proactive

Reactive/O

n-demand

Location aidedS

ingle / Multi-path

Best effort / G

uarantee delivery

Courtesy: Jean M


uNA

V

MA

NE

T routing protocols

AD

-HO

C M

OB

ILE R

OU

TING

PRO

TOC

OLS

ON

-DEM

AN

D-D

RIV

EN

REA

CTIV

E

HY

BR

IDD

SDV

OLSR

TAB

LE DR

IVEN

/ PR

OA

CTIV

E

DSR

AO

DV

ZRP

Courtesy: Jean M


uNA

V

Proactive R

outing

Table Driven

Each node periodically floods status of its links

Each node re-broadcasts link state inform

ation received from

its neighborE

ach node keeps track of link state information

received from other nodes

Each node uses above inform

ation to determine next

hop to each destination

Courtesy: Jean M


uNA

V

Reactive R

outing

Build route only w

hen node needs to send data packetThe source flood the netw

ork by sending out a request to discover the destination and routeE

ach node keep a complete route to each active

destination

Courtesy: Jean M


uNA

V

Reactive P

rotocols

�D

SR

�A

OD

V

Courtesy: Jean M


uNA

V

Dynamic Source Routing (DSR)

On-dem

andProtocolRREQ

: �

route requestRREP: �

route replyRERR: �

route error

S

D

5

62

1

4

3

RR

EQ(S)

RR

EQ(S)

RR

EQ(S)

(S,5)

(S,6)

(S,2)

(S,6,4)(S,6,4,3)

(S,2,1)

Courtesy: Jean M


uNA

V

DSR

Route selection�

Destination receive m

ultiple RR

EQ�

Shortest vs Fastest

Route cache�

Prom

iscuous mode:A

mode of operation in w

hich nodes can receive the packets that are neither broadcast nor addressed to itself

�R

educe floodingR

outing data packet:�

Use the route discovered during R

RE

Q�

Include the complete route inside data packet

Courtesy: Jean M


uNA

V

DSR: Route Maintenance

Perform

only when route in use

Detect out of range neighbor (failure)�

Link layer feedback 802.11�

Missing A

CK

Send R

ER

R back to original sender

�H

ow?

�R

oute repair?

Courtesy: Jean M


uNA

V

RO

UTE

MA

INTE

NA

NC

E

1

5

4

2

3

7

8

12

6

10

11

14

15

9

13

Source ID

Destination ID

SE

LEC

TED

PATH

RO

UTE

ER

RO

R

BR

OK

EN

LINK

Courtesy: Jean M


uNA

V

Dynam

ic Source R

outing: Advantages

Routes m

aintained only between nodes w

ho need to com

municate

�reduces overhead of route m

aintenance

Route caching can further reduce route discovery

overhead

A single route discovery m

ay yield many routes to the

destination, due to intermediate nodes replying from

local caches

Courtesy: Jean M


uNA

V

Disadvantages

Packet header size grow

s with route length

Flood of route requests may potentially reach all

nodes in the network

Care m

ust be taken to avoid collisions between

route requests propagated by neighboring nodes�

insertion of random delays before forw

arding R

RE

QIncreased contention �

Route R

eply Stormproblem

�R

eply storm m

ay be eased by preventing a node from

sending RR

EP if it hears another R

RE

P with a shorter route

Courtesy: Jean M


uNA

V

Disadvantages

An interm

ediate node may send R

oute Reply using a

stale cached route, thus polluting other cachesThis problem

can be eased if some m

echanism to

purge (potentially) invalid cached routes is incorporated. For som

e proposals for cache invalidation, see [H

u00Mobicom

]�

Static tim

eouts�

Adaptive timeouts based on link stability

Courtesy: Jean M


uNA

V

Disadvantages of DSR

Excessive flooding to find route

Hop-by-hop route

Security:�

RR

EQ

�Traceable route

Courtesy: Jean M


uNA

V

Ad H

oc On-D

emand D

istance Vector R

outing

DS

R includes source routes in packet headers

Resulting large headers can som

etimes degrade

performance

�particularly w

hen data contents of a packet are small

AO

DV

attempts to im

prove on DS

R by m

aintaining routing tables at the nodes, so that data packets do not have to contain routesA

OD

V retains the desirable feature of D

SR

that routes are m

aintained only between nodes w

hich need to com

municate

Courtesy: Jean M


uNA

V

AO

DV

Route R

equests (RR

EQ

) are forwarded in a m

anner sim

ilar to DS

RW

hen a node re-broadcasts a Route R

equest, it sets up a reverse path pointing tow

ards the source�

AOD

V assum

es symm

etric (bi-directional) links

When the intended destination receives a R

oute R

equest, it replies by sending a Route R

eplyR

oute Reply travels along the reverse path set-up

when R

oute Request is forw

arded

Courtesy: Jean M


uNA

V

Route R

equests in AO

DV

B

A

SE

F

H

J

D

C

G

IK

Z

Y

Represents a node that has received RREQ for D from

S

M

N

L

Courtesy: Jean M


uNA

V

Route R

equests in AO

DV

B

A

SE

F

H

J

D

C

G

IK

Represents transmission of RREQ

Z

YBroadcast transm

ission

M

N

L

Courtesy: Jean M


uNA

V

Route R

equests in AO

DV

B

A

SE

F

H

J

D

C

G

IK

Represents links on Reverse Path

Z

Y

M

N

L

Courtesy: Jean M


uNA

V

Reverse P

ath Setup in A

OD

V

B

A

SE

F

H

J

D

C

G

IK

•Node C receives RREQ from

G and H, but does not forw

ardit again, because node C has already forw

arded RREQonce

Z

Y

M

N

L

Courtesy: Jean M


uNA

V

Reverse P

ath Setup in A

OD

V

B

A

SE

F

H

J

D

C

G

IK

Z

Y

M

N

L

Courtesy: Jean M


uNA

V

Reverse P

ath Setup in A

OD

V

B

A

SE

F

H

J

D

C

G

IK

Z

Y

•Node D does not forward

RREQ, because node D

is the intended target of the RREQ

M

N

L

Courtesy: Jean M


uNA

V

Route R

eply in AO

DV

B

A

SE

F

H

J

D

C

G

IK

Z

Y

Represents links on path taken by RREP

M

N

L

Courtesy: Jean M


uNA

V

Route R

eply in AO

DV

An interm

ediate node (not the destination) may also send a R

oute Reply

(RR

EP) provided that it knows a m

ore recent path than the one previously know

n to sender S

To determine w

hether the path known to an interm

ediate node is more recent,

destination sequence numbersare used

The likelihood that an intermediate node w

ill send a Route R

eply when using

AO

DV

is not as high as DSR

�A

new R

oute Request by node S for a destination is assigned a higher

destination sequence number. A

n intermediate node w

hich knows a route,

but with a sm

aller sequence number, cannot send R

oute Reply

Courtesy: Jean M


uNA

V

Forward P

ath Setup in A

OD

V

B

A

SE

F

H

J

D

C

G

IK

Z

Y

M

N

L

Forward links are setup w

hen RREP travels alongthe reverse path

Represents a link on the forward path

Courtesy: Jean M


uNA

V

Data D

elivery in AO

DV

B

A

SE

F

H

J

D

C

G

IK

Z

Y

M

N

L

Routing table entries used to forward data packet.

Route is notincluded in packet header.

DATA

Courtesy: Jean M


uNA

V

Timeouts

A routing table entry m

aintaining a reverse path is purged after a tim

eout interval�

timeout should be long enough to allow

RR

EP to come back

A routing table entry m

aintaining a forward path is purged if

not used for a active_route_timeoutinterval

�if no data is being sent using a particular routing table entry, that entry w

ill be deleted from the routing table (even if the route m

ay actually still be valid)

Courtesy: Jean M


uNA

V

Link Failure Reporting

A neighbor of node X

is considered active for a routing table entry if the neighbor sent a packet w

ithin active_route_tim

eoutinterval, which w

as forwarded using

that entryW

hen the next hop link in a routing table entry breaks, all active

neighbors are informed

Link failures are propagated by means of R

oute Error m

essages, which also update destination sequence num

bers

Courtesy: Jean M


uNA

V

Route Error

When node X

is unable to forward packet P (from

node S to node D) on link

(X,Y

), it generates a RER

R m

essage

Node X

increments the destination sequence num

ber for D cached at node X

The incremented sequence num

ber Nis included in the R

ERR

When node S receives the R

ERR

, it initiates a new route discovery for D

using destination sequence num

ber at least as large as N

Courtesy: Jean M


uNA

V

Destination S

equence Num

ber

Continuing from

the previous slide …

When node D

receives the route request with

destination sequence number N

, node D w

ill set its sequence num

ber to N, unless it is already larger than

N

Courtesy: Jean M


uNA

V

Link Failure Detection

Hello messages: N

eighboring nodes periodically exchange hello m

essage

Absence of hello m

essage is used as an indication of link failure

Alternatively, failure to receive several M

AC

-level acknow

ledgement m

ay be used as an indication of link failure

Courtesy: Jean M


uNA

V

Why S

equence Num

bers in AO

DV

To avoid using old/broken routes�

To determine w

hich route is newer

To prevent formation of loops

�A

ssume that A

does not know about failure of link C

-D because R

ERR

sent by C

is lost�

Now

C perform

s a route discovery for D. N

ode A receives the R

REQ

(say, via path C

-E-A)

�N

ode A w

ill reply since A know

s a route to D via node B

�R

esults in a loop (for instance, C-E-A

-B-C

)

AB

CD

E

Courtesy: Jean M


uNA

V

Why S

equence Num

bers in AO

DV

�Loop C

-E-A-B-C

AB

CD

E

Courtesy: Jean M


uNA

V

Optim

ization: Expanding R

ing Search

Route R

equests are initially sent with sm

all Time-to-

Live (TTL) field, to limit their propagation

�D

SR

also includes a similar optim

ization

If no Route R

eply is received, then larger TTL tried

Courtesy: Jean M


uNA

V

Sum

mary: A

OD

V

Routes need not be included in packet headers

Nodes m

aintain routing tables containing entries only for routes that are in active useA

t most one next-hop per destination m

aintained at each node�

DS

R m

ay maintain several routes for a single destination

Unused routes expire even if topology does not change

Courtesy: Jean M


uNA

V

Proactive P

rotocols

�O

LSR

�D

SD

V

Courtesy: Jean M


uNA

V

Optim

ized Link State R

outing (OLS

R)

The overhead of flooding link state information is

reduced by requiring fewer nodes to forw

ard the inform

ationA

broadcast from node X is only forw

arded by its m

ultipoint relaysM

ultipoint relays of node X are its neighbors such that each tw

o-hop neighbor of X is a one-hop neighbor of at least one m

ultipoint relay of X�

Each node transmits its neighbor list in periodic beacons, so that

all nodes can know their 2-hop neighbors, in order to choose the

multipoint relays

Courtesy: Jean M


uNA

V

Optim

ized Link State R

outing (OLS

R)

Nodes C

and E are m

ultipoint relays of node A

A

BF

C

D

EH

GK J

Node that has broadcast state information from

A

Courtesy: Jean M


uNA

V

Optim

ized Link State R

outing (OLS

R)

Nodes C

and E forw

ard information received from

A

A

BF

C

D

EH

GK J


A

Courtesy: Jean M


uNA

V

Optim

ized Link State R

outing (OLS

R)

Nodes E

and K are m

ultipoint relays for node HN

ode K forwards inform

ation received from H

�E

has already forwarded the sam

e information once

A

BF

C

D

EH

GK J


A

Courtesy: Jean M


uNA

V

1

5

4

2

3

7

8

12

6

10

11

14

15

9

13

Node 4 selects M

PR

set {2,3,10,12}

Node belonging to M

PR

set of node 4

Broadcast packets forw

arded by m

embers of M

PR

set

Courtesy: Jean M


uNA

V

OLS

R

OLS

R floods inform

ation through the multipoint relays

The flooded information itself is for links connecting

nodes to respective multipoint relays

Routes used by O

LSR

only include multipoint relays as

intermediate nodes

Courtesy: Jean M


uNA

V

Destination-S

equenced Distance-V

ector

Each node m

aintains a routing table which stores

�next hop tow

ards each destination�

a cost metric for the path to each destination

�a destination sequence num

ber that is created by the destination itself�

Sequence num

bers used to avoid formation of loops and distinguish stale

route from fresh ones

Each node periodically forw

ards the routing table to its neighbors�

Each node increm

ents and appends its sequence number w

hen sending its local routing table

�This sequence num

ber will be attached to route entries created for this node

AB

CD

E

Courtesy: Jean M


uNA

V

Route E

stablishment

1

5

4

2

3

7

8

12

6

10

11

14

15

9

13

SourceID

Destination ID

DESTIN

ATIO

NN

EXT

NO

DE

DISTA

NC

ESEQ

UEN

CE

NU

MB

ER

22

122

32

226

45

232

55

1134

66

1144

72

3162

85

3170

92

4186

106

2142

116

3176

125

3190

135

4198

146

3214

155

4256

Courtesy: Jean M


uNA

V

DS

DV

Assum

e that node X receives routing inform

ation from Y

about a route to node Z

Let S(X

) and S(Y

) denote the destination sequence number for node Z

as stored at node X, and as sent by node Y with its routing table to node

X, respectively

XY

Z

Courtesy: Jean M


uNA

V

DS

DV

Node X

takes the following steps:

�If S

(X) > S

(Y), then X ignores the routing inform

ation received from Y

�If S

(X) = S

(Y), and cost of going through Y is smaller than the route know

n to X

, then X sets Y as the next hop to Z

�If S

(X) < S

(Y), then X sets Y as the next hop to Z, and S

(X) is updated to

equal S(Y)

XY

Z

Courtesy: Jean M


uNA

V

Hybrid P

rotocols

�ZR

P

Courtesy: Jean M


uNA

V

Zone Routing P

rotocol (ZRP

)

Zone routing protocol combines

Proactive protocol: w

hich pro-actively updates network

state and maintains route regardless of w

hether any data traffic exists or not

Reactive protocol: w

hich only determines route to a

destination if there is some data to be sent to the

destination

Courtesy: Jean M


uNA

V

ZRP

All nodes w

ithin hop distance at most d

from a node X

are said to be in the routing zone of node X

All nodes at hop distance exactly d

are said to be peripheral nodes of node X’s routing zone

Courtesy: Jean M


uNA

V

ZRP

Intra-zone routing: Pro-actively m

aintain state inform

ation for links within a short distance from

any given node�

Routes to nodes w

ithin short distance are thus maintained

proactively (using, say, link state or distance vector protocol)

Inter-zone routing: Use a route discovery protocol for

determining routes to far aw

ay nodes. Route discovery

is similar to D

SR

with the exception that route requests

are propagated via peripheral nodes.

Courtesy: Jean M


uNA

V

Routing Zone for N

OD

E 8 in ZR

P

1

5

4

2

3

7

8

12

6

10

11

14

15

9

13

SourceID

Destination ID

Courtesy: Jean M


uNA

V

ZRP

: Exam

ple

SC

A

EF B

D

S performs route

discovery for D

Denotes route request

Zone Radius = d = 2

Courtesy: Jean M


uNA

V

ZRP

: Exam

ple with d = 2

SC

A

EF B

D

S performs route

discovery for D

Denotes route replyE know

s route from E to D,

so route request need not beforw

arded to D from E

Courtesy: Jean M


uNA

V

ZRP

: Exam

ple with d = 2

SC

A

EF B

D

S performs route

discovery for D

Denotes route taken by Data

Courtesy: Jean M


uNA

V

Challenges

�R

eactive v/s Proactive

�A

ddress Assignm

ent

Courtesy: Jean M


uNA

V

Reactive versus P

roactive

Choice of protocol depends on�

Mobility characteristics of the nodes

�Traffic characteristics

How

to design adaptive protocols ?E

xisting proposals use a straightforward com

bination of reactive and proactive�

Proactive within “radius” K

�R

eactive outside K�

Choose K som

ehow

Courtesy: Jean M


uNA

V

Reactive versus P

roactive

Need a m

ore flexible way to m

anage protocol behavior

Assign proactive/reactive tag to each route (A

,B) ?

How

to determine w

hen proactive behavior is better than reactive ?

Courtesy: Jean M


uNA

V

Address Assignm

ent

How

to assign addresses to nodes in an ad hoc netw

ork ?S

tatic assignment

�E

asier to guarantee unique address

Dynam

ic assignment

�H

ow to guarantee unique addresses w

hen partitions merge?

Do w

e need to guarantee unique addresses ?

Courtesy: Jean M


uNA

V

Sum

mary

Plenty of interesting research problem

s

Research com

munity disproportionately obsessed w

ith routing protocols

Courtesy: Jean M


uNA

V

VE

HIC

ULA

R A

DH

OC

NE

TWO

RK

S

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

VA

NE

TS???

Ad hoc netw

ork composed of vehicles.

Provide comm

unications among nearby vehicles.

Com

munication betw

een vehicles and nearby fixed equipment.

V2I (V

2R) –

Internet Access in vehicles.

V2VO

R IVC

–C

omm

unication among vehicles.

Departm


Com


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Courtesy: Jean M


uNA

V

NEED

FOR

VANETS…

.

SAFETY ON RO

ADS

-REDUCING ACCIDENTS

-ALLEVIATING

TRAFFIC CONDITIO

NS-IM

PROVING

TRANSPORT EFFICIENCY

-MO

NITORING

TRAFFIC

ENVIRONM

ENT-REDUCE TRAFFIC CO

NGESTIO

N-REDUCE PO

LLUTION

DRIVING CO

MFO

RT-DRIVING

ASSISTANCE-INFO

TAINMENT APPLICATIO

NS

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

ITS –

IN B

RIE

F W

HAT IS

ITS?

Stands for INTELLIG

ENT TR

AN

SPOR

TATIO

N SYSTEM

ITS improves transportation safety and m

obility

Enhances productivity through the use of advanced com

munications

technologies.

Encom

pass a broad range of wireless and w

ire line comm

unications-based inform

ation and electronics technologies.

The 5.9 GH

z band has been designated by the FCC

for vehicular com

munications using ITS.

Departm


Com


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Courtesy: Jean M


uNA

V

CO

NTIN

UED

….

ITSis

made

upof16

typesoftechnology

basedsystem

s.

System

sare

dividedinto

two

parts

Intelligentinfrastructuresystem

sintelligentvehicle

systems.

Departm


Com


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Courtesy: Jean M


uNA

V

Intelligent Infrastructure

Departm


Com


IT Manipal

Arterial M

anagement

Freeway M

anagement

Transit Managem

entIncident M

anagement

Em

ergency Managem

ent

Electronic P

ayment

Traveler Information

Information M

gmt

Crash P

revention and safety

Roadw

ay Operations

and maintenance

Road W

eather M

anagement

Com

mercial Vehicle

Operations

Intermodal Freight

Courtesy: Jean M


uNA

V

Intelligent Vehicles

Departm


Com


IT Manipal

Collision

Avoidance S

ystems

Collision

Notification

System

s

Driver

Assistance

System

s

Courtesy: Jean M


uNA

V

DS

RC

-An O

verview�

Aw

irelesstechnology

forvehiculartraffic

�R

oad-to-vehiclecom

munications

bym

eansofw

irelessis

called“D

edicatedS

hort-Range

Com

munications

(DS

RC

)developedby

JapanforITS

applicationssuch

asE

TC,etc.

�E

lectronicTollC

ollection(E

TC)is

asystem

forprocessingautom

atictoll

collection,usingw

irelesscom

munications

between

comm

unicationequipm

entinstalledin

tollgatesand

otherunitson

passingvehicles.

�5.8

GHz

waveband

plannedforD

edicatedS

hortRange

Com

munication

(DS

RC

)INuse

inJapan.

�E

xistingD

SR

Cin

JAP

AN

of5.8G

Hz

ism

eantfordedicatedITS

applicationsand

doesnot

supportfutureapplications

suchas

intervehicularcomm

unicationsand

generalpurposeapplications,and

henceithas

tobe

modified.

Departm


Com


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Courtesy: Jean M


uNA

V

Departm


Com


IT Manipal

Spectrum

of DS

RC

Courtesy: Jean M


uNA

V

DS

RC

-type Inter Vehicular C

omm

unications (IVC

)

DSRC type V2V enables

�C

reation of AD

HO

C netw

orks among vehicles.

�A person’s vehicle can com

municate vehicle

control information bi-directionally w

ith other vehicles running nearby.

�A

group of vehicles are configured which shares a

comm

unication service on a temporary basis.

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

DS

RC

-type Road to V

ehicle Com

munication (V

2R)

�C

omm

unication is done between w

ireless base stations located at the road-side and m

obile stations.

�S

ervice area environment w

ill be on roads themselves or near roads.

�S

ervice area is a pico-cell with a radius of approxim

ately a few tens of

meters or, at m

ost a micro-cell w

ith a radius of a few hundred m

eters.

�DSRC-type V2R system

s, system design can be done on the basis

of the following assum

ptions.

-Existence of “line of sight” comm

unication paths-M

ulti-path propagation paths

�C

apability of simultaneously providing m

ultiple general purposeservices, in addition to ITS

dedicated services such as VIC

S, ETC

, AHS

.

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

V2R

General P

urpose Services

�M

obile Com

munication S

ervices.

�S

atellite Broadcast S

ervices.

�Large scale D

ata downloading S

ervices.

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

DS

RC

and Other C

omm

unications

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

IEE

E 802.11P

Departm


Com


IT Manipal

IEE

E 802.11p is a standard in the IEE

E 802.11 family.

IEEE

802.11p also referred to as Wireless A

ccess for the V

ehicular Environm

ent (WA

VE) defines enhancem

ents to 802.11 required to support Intelligent Transportation S

ystems (ITS

) applications.

Includes data exchange between high-speed vehicles

and between the vehicles and the roadside infrastructure

in the licensed ITS band of 5.9 G

Hz (5.85-5.925 G

Hz) for

US.

IEE

E802.11p is being standardized in the US

and E

urope.

Courtesy: Jean M


uNA

V

IEE

E 802.11P

Departm


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IT Manipal

802.11p will be used as the groundw

ork for DS

RC

for U

S and Europe to support existing D

SRC

applications such as V

ICS,E

TC etc as w

ell as future applications.

The IEEE

802.11p standard is being developed from

IEE

E802.11a.

Courtesy: Jean M


uNA

V

CH

AR

AC

TER

ISTIC

S•

VAN

ETs are characterized by:

•W

ide spectrum of applications (safety/non-safety)

•S

elf-organization and self-managem

ent (fully decentralized)

•N

etwork protocol requirem

ents (efficient geo-casting/flooding)

•A

dverse medium

conditions (congestion and radio channel)D

epartment of Inform

ation & C

omm

unication Technology ,MIT M

anipal

Courtesy: Jean M


uNA

V

Benefits and D

rawbacks

ÆBenefitsAd-hoc vehicular netw

orks provide ubiquitousenvironm

entsA

bundant information by C

2C and C

2IInteractiveness can provide location-based services,driving safety, and on-dem

and servicesN

o practical limit on pow

er and computation

Drawbacks

–H

igh mobility m

ay restrict bandwidth

–S

ecurity problems : identity, location privacy

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

Need for D

ata Validation

•Out-of-date inform

ationV

ehicles move and change speed

Packets m

ay get lost in transitS

olution: Data aging

•Malicious nodes can corrupt data

Inject incorrect dataR

efuse to forward data

Modify data

•Solution: P

robabilistic validation

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

Push v/s P

ull

Most cars are interested in inform

ation about imm

ediate neighboring road segm

ent�

“Push” mechanism

is sufficientH

ow to get inform

ation about other roads?B

roadcast is not scalable�

Road segm

ents are extensive in size�

Traffic information is dynam

ic in nature

There is a need for “pull” i.e. On-Dem

and traffic query

Departm


Com


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Courtesy: Jean M


uNA

V

On-dem

and Traffic Query P

rotocol

VITP –Vehicular Inform

ation Transfer Protocol�

Location-sensitive queries and replies between nodes

of a VA

NE

T�

VITP Peers –

nodes that operate as •

Clients

•Interm

ediates•

Servers

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

Location-sensitive queries

Departm


Com


IT Manipal

Quic

kTim

e™ and a

TIF

F (U

ncompress

ed) decompres

sorare nee

ded to see this

picture.

Quic

kTim

e™ and a

TIF

F (U

ncompress

ed) decompres

sorare nee

ded to see this

picture.

Gas S

tationQuickTim

e™ and a

TIFF (LZW) decompressorare needed to see this picture.

Coffee

place

QuickTime™

and aTIFF (LZW) decompressor

are needed to see this picture.

GS

M Link

TrafficS

erver

QuickTime™ and aTIFF (Uncompressed) decompressor


QuickTime™ and aTIFF (Uncompressed) decompressor


Courtesy: Jean M


uNA

V

Virtual A

d-Hoc S

ervers The server that com

putes the reply is a dynamic collection

of VITP peers that:

�R

un on vehicles moving inside the target-location area

of Q.

�Are w

illing and able to participate in Q’s resolution.

Departm


Com


IT Manipal

Gas S

tationQuickTim

e™ and a

TIFF (LZW) decompressorare needed to see this picture.

QuickTime™

and aTIFF (LZW) decompressor


Q uic kT im e™ and aT IF F ( Uncom press ed) decom pres sor

ar e nee ded t o se e t his pictu re.

Courtesy: Jean M


uNA

V

VA

HS

(continued)

Established on the fly in an ad-hoc m

anner

Identified with a query and its target-location area.

Maintains no explicit know

ledge (state) about its constituent V

ITP peers

Follows a best-effort approach in serving queries

VAH

S mem

bers maintain no inform

ation about other m

embers of the V

AH

S

Departm


Com


IT Manipal

Courtesy: Jean M


uNA

V

VITP

transactions

Departm


Com


IT Manipal

VITP P

eer

VAN

ET node

VAH

SQ

Q

Intermediary nodes

Q1

Q2Q

3

Q4

Q5Q

6Q

7

R

RR

Dispatch-query phase

VAH

S-computation phase

Dispatch-R

eply phaseR

eply-delivery phase

Courtesy: Jean M


uNA

V

Departm


Com


IT Manipal

•C

ar manufacturers have m

assively invested in this area

•S

ecurity leads to a substantial overhead and must be taken into

account from the beginning of the design process

•P

lent of problems to address in ITS

CONCLUSIO

N

Courtesy: Jean M


uNA

V

Inter Vehicular C

omm

unication Applications

Courtesy: Jean M


uNA

V

Why do w

e need IVC

Applications??

Informing about traffic situations.

Informing about the things happening in that region

when a vehicle passes through that region.

Getting all the inform

ation needed from the gatew

ay node ( Inform

ation like latest news updates, latest

score updates….etc). The gatew

ays are connected to the internet.

Courtesy: Jean M


uNA

V

IVC

Applications

InfoShare

(Information

Sharing

Application

forIVN

s)

-A

pplicationw

hichis

usedto

sharedata

between

thevehicles

moving

alongthe

road.-D

oesnotuse

anyrouting

algorithm.

-Query

message

isbroadcasted

ina

multihop

fashion.

InfoGeo

-Builtupon

infoshare.-U

sesG

eorouterouting

algorithm.

Courtesy: Jean M


uNA

V

A sim

ple Scenario

•Gatew

aynodes

arepresent

atthe

roadends

which

areconnected

tothe

internetand

which

containallthe

information

items

.•When

avehicle

passesthrough

agatew

aynode,itdow

nloadsallthe

information

fromthe

gateway

node.

•When

avehicle

isfar

away

froma

gateway

nodeand

ifit

needssom

einform

ation,it

triesto

getthe

information

with

thehelp

ofothervehicles.(

Theother

vehiclesactas

therelays).

Courtesy: Jean M


uNA

V

A S

imple S

cenario

•Forexam

ple,in

thefigure

shown,

ifthe

violetcarwants

some

information,

itis

away

fromboth

thegatew

aynodes.

So,

itbroadcasts

thequery

message

andother

vehiclesreceive

thisquery

message.

Ifthat

vehiclehas

therequired

information,itreplies

with

therequired

information.

Ifit

dosen’thave,

italso

broadcaststhe

query.

•So,

inthis

example,

blue,pink

andred

vehiclesreceive

thequery

fromviolet

carw

henit

needssom

einform

ation.S

o,these

carsact

asrelays.

Courtesy: Jean M


uNA

V

Requirem

ents for these applicationsV

ehiclesto

beequipped

with

highbit

rateradio

interfaceand

gigabytesof

storagesupporting

lotsof

applications.S

ensibledissem

inationand

cachingpolicy

isneeded.

Aset

ofinform

ationcategories

thatusers

may

beinterested

in,andthatthey

“pull”fromthe

network.

Access

pointsorgatew

aynodes

feedpassing

carsthe

information

theyrequire.

Tom

aximize

thechance

ofgetting

freshinform

ation,w

eassum

ethatvehicles

arecapable

ofcooperatingto

disseminate

theinform

ationthat

was

pulledfrom

gateways,in

ordertoreach

farthervehiclesby

forming

anad

hocnetw

ork.

Courtesy: Jean M


uNA

V

INFOSHARE DETAILS

Courtesy: Jean M


uNA

V

Infoshare

An application w

hich is used to share multiple sm

all pieces of inform

ation between vehicles m

oving along the road.

Infoshare works as follow

s:�

A vehicle which requires som

e information sends a request

message.

�This request m

essage is broadcasted until a vehicle carrying desired inform

ation is found.�

The information is sent back follow

ing the same return path.

�Then the vehicle stores this inform

ation for a certain period of tim

e and then discards it later.

Courtesy: Jean M


uNA

V

Infoshare Query M

essage Format

A query m

essage generated by a vehicle has the follow

ing information:

�Inform

ation ID: The identifier of the requested piece of

information, am

ong the N available ones.

�Sequence Num

ber : current number of the request perform

ed by the application. This is increm

ented at each newly generated

query, and it is used by nodes receiving the query message to

distinguish among copies of the sam

e query.�

Source Address : The address of the node that generated the query.

�Next Hop Address: the address of the node that sent this query m

essage. when the query is generated first tim

e, this is same as

the source address.�

Time to live: field contains the m

aximum

number of hops

allowed for the current m

essage.

Courtesy: Jean M


uNA

V

Infoshare Query S

preading

Query spreading is totally perform

ed through broadcast in a m

ultihop fashion.The query is broadcasted by the source vehicle.The other vehicles that receive the query have a query list.E

ach query in the query list is described by:�

Information ID

�S

equence number

�Next hop address : This is the address of the node from

which

the query was received.

�Status : P

END

ING

or SO

LVED

.

Courtesy: Jean M


uNA

V

Infoshare Query S

preading

Ifthe

applicationdoes

nothave

therequested

information

inits

cacheand

theTTL

fieldin

thequery

message

isnot

zero,the

vehicleacts

asa

relay,forw

ardingthe

query.B

eforeretransm

ittingthe

query,thenode

replacesthe

contentof

thenext

hopaddress

fieldw

ithits

own

address.Itw

aitsfora

flooding.query

lagintervaloftim

e,priortochecking

whetherthe

querystatus

isstillP

EN

DIN

G:thus

itlimits

query

Courtesy: Jean M


uNA

V

Infoshare Information R

etrieval and Transm

ission

When

thequery

isreceived

bya

nodew

hichhas

theinform

ation,then

thatnode

transmits

thisinform

ationto

thenexthop

indicatedin

thereceived

query.

Thenext

hopvehicle

thatreceives

thisinform

ationupdates

thestatus

ofthe

queryto

“solved”and

thentransm

itsit

tothe

nexthop

andthis

continuestillthe

information

reachesthe

sender.

Courtesy: Jean M


uNA

V

Sim

ple Scenario to explain Infoshare

Car1 -R

edC

ar2 -Green

Car3 –

Blue

Car4-P

inkA

ccess points at each road ends -Black

Courtesy: Jean M


uNA

V

Sim


Car3

(Blue)needs

some

information

(ID=

k).Itbroadcasts

thequery

message

with

Information

ID=

kand

nexthopaddress=

addrofcar3,source

addr=

addrofcar3.A

ssume

car2and

car4

arein

rangeof

car3.They

receivethe

queryfrom

car3.If

theydon’t

havethe

requestedinform

ationin

cache,�

Theycheck

theTTL

field.Ifitisnotzero,then

theyactas

relays.�

Itaddsthis

queryin

thequery

list(with

statuspending)

�They

replacethe

Next

hopaddr

with

theirow

naddr

andthey

broadcastthequery

again.(forexam

plein

thissecnario,car4

replacesnexthop

addrtoaddr

ofcar4and

broadcaststhe

queryagain).

Courtesy: Jean M


uNA

V

Sim


Thisquery

fromcar4

willbe

receivedby

thegatew

aynode.S

o,it

repliesw

iththe

requiredinform

ationto

node4(using

thenexthop

addressin

thequery).

Car4

thenupdates

thestatus

ofthisquery

toS

OLV

ED

inthe

querylistand

forwards

thisinform

ationto

Car3

(usingthe

nexthopaddress

inthe

query).C

ar3w

hichis

thesource

finallyreceives

therequired

information.

Courtesy: Jean M


uNA

V

Problem

s with Infoshare

Theinform

ationthatis

requiredis

returnedback

tothe

sourceusing

thesam

epath

asexplained

inthe

previousslides

(U

singnext

hopaddress).

But

sincethe

network

formed

isadhoc,

anode(car)

inthe

pathm

aynot

bepresent

while

theinform

ationis

beingreturned

backto

thesource.

Since

itdoes

notuse

anyrouting,

(sim

plebroadcast

mechanism

isused)

thenetw

orktraffic

will

bevery

high.

Courtesy: Jean M


uNA

V

Why InfoG

eo ?

Toapply

ageographical

routingprotocol

suchas

GeoR

outeto

am

odifiedversion

ofthe

Infoshareapplication

inorder

tom

aximize

ofinform

ationretrieval,

while

limiting

theflooding

ofinform

ationqueries.

Courtesy: Jean M


uNA

V

Greedy P

erimeter S

tateless Routing

Protocol (G

PSR

)

A position based routing

Courtesy: Jean M


uNA

V

GP

SR

The algorithm consists of tw

o methods for forw

arding packets:

�G

reedy forwarding, w

hich is used wherever possible, and

�Perim

eter forwarding, w

hich is used in the regions greedy

forwarding cannot be.

Courtesy: Jean M


uNA

V

Greedy Forw

arding�

Under G

PSR, packets are m

arked by their originator with their

destinations’ locations.

�A

s a result, a forwarding node can m

ake a locally optimal, greedy

choice in choosing a packet’s next hop.

�Specifically, if a node know

s its radio neighbors’ positions, the locally optim

al choice of next hop is the neighbor geographically closest to the packet’s destination.

�Forw

arding in this regime follow

s successively closer geographic hops, until the destination is reached.

Courtesy: Jean M


uNA

V

Exam

ple

xy

D

x forwards the Packet to

y as distance between

y andD

is less than any ofx’s other neighbor. This forw

arding repeats until packet reaches D

Courtesy: Jean M


uNA

V

Greedy forw

arding Failure

xy

w

vz

D

x is closer to D than its neighbors w

and y. Although there exist tw

o paths (x-y-z-D)

and

(x-w-v-D

),but xw

ill not choose to forward to w

or yusing greedy forw

arding. x is a local

maxim

um in its proxim

ity toD

.

Courtesy: Jean M


uNA

V

Need for P

erimeter Forw

arding

Intersection of x'sradio range and the circle about D

of radius xDis em

pty of

neighbors. The shaded region without nodes is called void.

If x seeks to forward a packet to destination D

beyond the edge of this void. Intuitively,

xseeks to route around the void, if a path to D

exists from x.

Courtesy: Jean M


uNA

V

Concept behind P

erimeter Forw

arding

Right hand rule

•It traverse the interior of a closed polygon region (a face) in clock w

ise edge order

Exam

ple: x receives a packet from y forw

ards it to z

1.

2.

3.

y

xz

Courtesy: Jean M


uNA

V

Perim

eter Forwarding

st

Forwarding is show

n only for exposition of perimeter m

ode

Courtesy: Jean M


uNA

V

Com

bining Greedy &

Perim

eter Forwarding (G

PS

R A

lgorithm)

All packets are forw

arded in greedy mode

Forward packet to neighbor closest to D

estination

If greedy fails, switch to perim

eter mode

•M

ark packet with current location

•Forw

ard along successively closer faces by right-hand rule until reaching

Destination or

Reach a node closer to D

estination than perimeter m

ode entry point

•Return to greedy forw

arding mode

Traverse face closer to Destination (D

) along xD(line joining

forwarding node x

and D) by right-hand rule.

Courtesy: Jean M


uNA

V

Limitation in G

PS

R

Looping

Moving aw

ay from destination (w

rong direction), in case of perim

eter mode.

Many hops.

Courtesy: Jean M


uNA

V

State D

iagram for G

PS

R operation

Courtesy: Jean M


uNA

V

INFOG

EO D

ETAILS

Courtesy: Jean M


uNA

V

InfoGeo

InfoGeo

which

isbuilt

uponinfoshare

makes

useof

GeoR

oute.C

onsistsoftw

ophases:

Phase1:

broadcastphase

(Sim

ilarto

InfoShare

application)P

hase2:makes

useofG

eoRoute

routingalgorithm

.

NO

TE:1.

Itis

assumed

thatevery

vehicleis

equippedw

ithG

PS

(Toknow

it’sow

ncoordinates).

2.W

henevera

vehiclepasses

througha

gateway,

itgets

thelocation

ofthenextnearestgatew

ay.

Courtesy: Jean M


uNA

V

Georoute

Routing protocol to deliver the inform

ation packets to destination “D

” with know

n geographical coordinates (Xd, Y

d).A transm

itter node should know it’s ow

n coordinates and the coordinates of the destination node as w

ell. (P

osition aware routing protocol).

Courtesy: Jean M


uNA

V

Georoute H

eader

Packet Identifier:local identifier of the packet.Flow

ID: Identifier of the flow m

essage in the case w

here the sender has more than one active m

essage flow

.Hop CounterSNC, DNC,CSNC

(source, destination, current node coordinates).

Courtesy: Jean M


uNA

V

Selection of relay nodes

Weighted progression factor G

= f(Dp,D

c) where the

function G is defined as (D

p-Dc).

Dp-Distance betw

een the previous hop node and the destination.

Dc-Distance betw

een the current hop node and the destination.

Courtesy: Jean M


uNA

V

Relaying

Ifthenode

realizesto

besuitable

asa

relay,i.e.,G>

0,it

storesthe

following

fields,P

ID,

SN

C,

FIDand

DN

Cin

asm

allcache,

usedto

avoidforw

ardingthe

same

packetmore

thanonce.

Then,the

node,after

atim

einterval

inverselyproportional

tothe

valueof

itsprogress

factor,forw

ardsthe

datapacket

replacingin

thepacket

headerthecoordinates

ofthecurrenttransm

itternode(C

SN

C)

with

itsow

ncoordinates

andincreases

thehop

counter(HC

)byone.

Courtesy: Jean M


uNA

V

Scenario to explain G

eoRoute

Courtesy: Jean M


uNA

V

Source –

Car B

Destination –

Car E

Assum

e Car A

and Car C

are in the range of Car B

.so, the query m

essage from B

will be received by A

and C

.At car A:D

p = 700,D

c = 1000 (from fig)

Therefore G at car A

= Dp-D

c = 700-1000 < 0.S

o, according to Georoute, carA

will cancel

relay(will not act as relay node).


eoRoute

Courtesy: Jean M


uNA

V

At car C

,D

p = 700D

c = 500 (from fig)

G = D

p-Dc = 700-500 = 200 > 0.

Therefore according to Georoute, C

ar C w

ill act as relay.


eoRoute

Courtesy: Jean M


uNA

V

InfoGeo (phase 1)

�P

hase1

iscalled

broadcastphase.�

Anode

wishing

toretrieve

aninform

ationitem

generatesa

querym

essageand

broadcaststhe

requeststo

itsneighbors,i.e.,the

nodesw

ithinits

coveragerange.

�The

querybroadcast

isperform

edusing

thesam

em

echanisms

specifiedby

theInfoshare

application.�

Aquery

listiscreated

ateachnode

andthe

querystatus

isfirstsetto

PE

ND

ING

�The

TTLfield

issetto

1so

thatonlyone

hopis

allowed.

�A

newflag,

calledB

RO

AD

CA

STis

introduced,w

hichis

setto1

Courtesy: Jean M


uNA

V

Ifthe

queryreaches

avehicle

thatow

nsthe

desiredinform

ation,this

will

imm

ediatelysend

backthe

information.

Ifnoreply

isreceived

within

agiven

timeout,the

noderequesting

theinform

ationitem

entersthe

secondphase

oftheInfoG

eoschem

e. InfoGeo (phase 1)

Courtesy: Jean M


uNA

V

InfoGeo (P

hase2)The

secondphase

isperform

edw

henthe

Broadcastphase

fails,i.e.,

thetim

eouttim

erexpires

andthe

querystatus

atthe

requestingnode

isstillP

EN

DIN

Gand

thecorresponding

BR

OA

DC

AS

Tflag

issetto

1.

Thevehicle

generatesa

new,unicastquery,reporting

itsow

ncoordinates,

theaddress

ofthe

nearestgatew

ayalong

theroad

asdestination

address,and

thegatew

aycoordinates.

Courtesy: Jean M


uNA

V

Thequery

will

berouted

towards

thedestination

gateway

accordingto

theG

eoRoute

policy.

When

thegatew

ayreceives

thequery,

itreplies

with

thedesired

information

message

sentthrough

a(possibly

different)unicast

pathto

thevehicle

thatgenerated

thequery.

InfoGeo (P

hase2)

gps, manets 2

Documents

satellite navigation

global coverage

certain location

global operational gnsss

application courtesy

emergency caller location

tracking devices

planned gnss