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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
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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
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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,
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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
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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
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Aim at a glance
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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
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Building block / Basic principle
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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.
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Determining transit time
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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.
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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.
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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.
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GPS, THE TECHNOLOGY
Divided into three segments to reduce the complexity
¾ space segment.¾ control segment.¾ user segment.
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Space segment
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Orientation of satellites
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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
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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.
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Detailed block system
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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.
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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.
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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.
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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.
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Navigation Frame
Each frame has a 5 sub frames.First 3 sub frames contain local data.
Last 2 subframes contain system data.
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Subframe Data
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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.
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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.
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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
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(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.
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Structure of the navigation message
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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.
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Comparison between Ephemeris and Almanac Data
Ephemeris and Almanac
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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
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PRN CODE GENERATION
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First 100 Bits of PRN1 and PRN22
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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).
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PRN Code Correlation
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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.
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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.
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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
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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
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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.
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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.
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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).
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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.
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Error Sources
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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
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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
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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
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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
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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
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Ideal Satellite GeometryN
S
W E
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Dilution Of Precision (DOP)
Good DOP
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Good Satellite Geometry
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Dilution Of Precision (DOP)
Good DOP
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Poor Satellite GeometryN
S
W E
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Poor Satellite Geometry
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Dilution Of Precision (DOP)Poor DOP
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Poor Satellite Geometry
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Dilution Of Precision (DOP)Poor DOP
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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
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DATA FORMATS AND HARDWARE INTERFACES
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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)
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Block Diagram of GPS Receiver
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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.
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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
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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.
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Data Formats
Description of Individual NMEA DATA SET blocks
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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 : $GPGGA,130304.0,4717.115,N,00833.912,E,1,08,0.94,00499,M,047,M,,*59<CR><LF>
Data Formats
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2. GLL Data Set: The GLL data set (geographic position latitude / longitude)
contains information on latitude and longitude, time And health.Example:$GPGLL,4717.115,N,00833.912,E,130305.0,A*32<CR><LF>
GGL Data Set Blocks
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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 :$GPGSA,A,3,13,20,11,29,01,25,07,04,,,,,1.63,0.94,1.33*04<CR><LF>
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4. GSV Data Set :The GSV Data set (GNSS Satellite in View) contains
information on the number of satellite in view, theiridentification, their elevation and azimuth, and the signalto-noise ratio.
Example :$GPGSV,2,2,8,01,52,187,43,25,25,074,39,07,37,286,40,04,09,36,33*44<CR><LF>
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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 : $GPRMC,130304.0,A,4717.115,N,00833.912,E,000.04,205.5,20601,01.3,W*7C<CR><LF>
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6. VTG Data set :The VTG data set (Course over ground Speed) contains
information on course and speed.
Example :$GPVTG,014.2,T,015.4,M,000.03,N,000.05,K*4F<CR><L>
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VTG Data Set Blocks
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7. ZDA Data Set : The ZDA data set (time and date) contains information
on UTC time, the date and local time.
Example :$GPZDA,130305.2,20,06,2001,,*57<CR><LF>
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ZDA Data Set Blocks
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Calculating Checksum : The checksum is determined by an exclusive-or
operation involving all 8 data bits (excluding start andstop bits) from all transmitted characters, includingseparators. It starts at ($ 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.
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Example : $GPRTE,1,1,c,0*07
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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.
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Differential GPS
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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
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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
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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)
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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
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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
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2. Helix Antenna: Helix antenna are cylindrical in shape and have higher gain than patch antenna.
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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.
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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
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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?
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arie Zogg –u-blox and
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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.
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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
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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
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Geostationary WAAS satellites
GPS Constellation
WAAS Control Station (West Coast)
Local Area System (LAAS)
WAAS Control Station (East Coast)
Wide Area Augmentation System
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+ -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 ?
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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.
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arie Zogg –u-blox and
uNA
V
Why G
alileo?
GLO
NA
SS is not fully operationalN
AV
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.
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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
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arie Zogg –u-blox and
uNA
V
Galileo Satellites in orbit
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arie Zogg –u-blox and
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V
A G
ALILE
O S
ATE
LLITE
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arie Zogg –u-blox and
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V
International Partners
•IN
DIA
•C
HIN
A•
ISR
AE
L•
UK
RA
INE
•M
OR
OC
CO
•S
AU
DI A
RA
BIA
•S
OU
TH K
OR
EA
•A
nd still counting
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arie Zogg –u-blox and
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V
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)
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arie Zogg –u-blox and
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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.
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arie Zogg –u-blox and
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
Ssignals,as
wellas
at1260–1300
MH
z.
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arie Zogg –u-blox and
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.)
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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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
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arie Zogg –u-blox and
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
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arie Zogg –u-blox and
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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
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arie Zogg –u-blox and
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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.
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arie Zogg –u-blox and
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V
Inter-Vehicular C
omm
unication
Departm
ent of Information &
Com
munication Technology ,M
IT Manipal
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arie Zogg –u-blox and
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)
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arie Zogg –u-blox and
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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:
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arie Zogg –u-blox and
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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
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arie Zogg –u-blox and
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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
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arie Zogg –u-blox and
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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
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arie Zogg –u-blox and
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V
Definition: W
ireless Netw
orks
Refers
tothe
useof
infraredor
radiofrequency
signalsto
shareinform
ationand
resourcesbetw
eendevices
Departm
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
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arie Zogg –u-blox and
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V
Routing In A
dhoc networks(M
AN
ET)
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arie Zogg –u-blox and
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V
Routing in W
ire Net
Link State
Distance Vector
Will it W
ork for M
ANET??
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arie Zogg –u-blox and
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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
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arie Zogg –u-blox and
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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
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arie Zogg –u-blox and
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
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arie Zogg –u-blox and
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
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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).
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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.
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arie Zogg –u-blox and
uNA
V
MANET Routing Decisions
Proactive
Reactive/O
n-demand
Location aidedS
ingle / Multi-path
Best effort / G
uarantee delivery
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
Reactive P
rotocols
�D
SR
�A
OD
V
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
Disadvantages of DSR
Excessive flooding to find route
Hop-by-hop route
Security:�
RR
EQ
�Traceable route
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
Why S
equence Num
bers in AO
DV
�Loop C
-E-A-B-C
AB
CD
E
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
Proactive P
rotocols
�O
LSR
�D
SD
V
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
Node that has broadcast state information from
A
Courtesy: Jean M
arie Zogg –u-blox and
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
Node that has broadcast state information from
A
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
Hybrid P
rotocols
�ZR
P
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
Challenges
�R
eactive v/s Proactive
�A
ddress Assignm
ent
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
Sum
mary
Plenty of interesting research problem
s
Research com
munity disproportionately obsessed w
ith routing protocols
Courtesy: Jean M
arie Zogg –u-blox and
uNA
V
VE
HIC
ULA
R A
DH
OC
NE
TWO
RK
S
Departm
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
uNA
V
CO
NTIN
UED
….
ITSis
made
upof16
typesoftechnology
basedsystem
s.
System
sare
dividedinto
two
parts
Intelligentinfrastructuresystem
sintelligentvehicle
systems.
Departm
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
uNA
V
Intelligent Infrastructure
Departm
ent of Information &
Com
munication Technology ,M
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
arie Zogg –u-blox and
uNA
V
Intelligent Vehicles
Departm
ent of Information &
Com
munication Technology ,M
IT Manipal
Collision
Avoidance S
ystems
Collision
Notification
System
s
Driver
Assistance
System
s
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
uNA
V
Departm
ent of Information &
Com
munication Technology ,M
IT Manipal
Spectrum
of DS
RC
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
uNA
V
DS
RC
and Other C
omm
unications
Departm
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
uNA
V
IEE
E 802.11P
Departm
ent of Information &
Com
munication Technology ,M
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
arie Zogg –u-blox and
uNA
V
IEE
E 802.11P
Departm
ent of Information &
Com
munication Technology ,M
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
uNA
V
Location-sensitive queries
Departm
ent of Information &
Com
munication Technology ,M
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
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Courtesy: Jean M
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Gas S
tationQuickTim
e™ and a
TIFF (LZW) decompressorare needed to see this picture.
QuickTime™
and aTIFF (LZW) decompressor
are needed to see this picture.
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
arie Zogg –u-blox and
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
ent of Information &
Com
munication Technology ,M
IT Manipal
Courtesy: Jean M
arie Zogg –u-blox and
uNA
V
VITP
transactions
Departm
ent of Information &
Com
munication Technology ,M
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
arie Zogg –u-blox and
uNA
V
Departm
ent of Information &
Com
munication Technology ,M
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
arie Zogg –u-blox and
uNA
V
Inter Vehicular C
omm
unication Applications
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
INFOSHARE DETAILS
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
Sim
ple Scenario to explain Infoshare
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
arie Zogg –u-blox and
uNA
V
Sim
ple Scenario to explain Infoshare
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
Greedy P
erimeter S
tateless Routing
Protocol (G
PSR
)
A position based routing
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
Perim
eter Forwarding
st
Forwarding is show
n only for exposition of perimeter m
ode
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
State D
iagram for G
PS
R operation
Courtesy: Jean M
arie Zogg –u-blox and
uNA
V
INFOG
EO D
ETAILS
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
uNA
V
Scenario to explain G
eoRoute
Courtesy: Jean M
arie Zogg –u-blox and
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).
Scenario to explain G
eoRoute
Courtesy: Jean M
arie Zogg –u-blox and
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.
Scenario to explain G
eoRoute
Courtesy: Jean M
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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
arie Zogg –u-blox and
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)