AProject Report

On

Vehicle-to-Vehicle Communication&

Wireless Sensor Networks

Submitted in partial fulfillment of the 6th semester training of Bachelor of Technology Degree

(2007-2011)To

Department of Information Technology

Undertaken At:Department of Information Technology

Ministry of Communications and Information Technology

Govt. Of India

Submitted By: Rakesh kumar Roll no:0111507808

GOVERNMENT OF INDIAMINISTRY OF COMMUNICATIONS & INFORMATION

TECHNOLOGY

DEPARTMENT OF INFORMATION TECHNOLOGY

TO WHOMSOEVER IT MAY CONCERN:

This is to certify that Rakesh , University Roll No. -

0111507808, a student of B.Tech from Maharaja surajmal institute of Technologyhas done his 4th-semester training at CC&BT Group, Department of

Information Technology, New Delhi, from june-2010 to july-2010.

The project work entitled “Vehicle-to-vehicle Communications

and Wireless Sensor Networks” embodies the original work done

by Rakesh during his 4th semester project training period.

B.M. BAVEJASenior Director & HoD

B.Tech IIT, Delhi, MSc (Lon Univ.), MSc (Birmingham Univ.)

Sr. Director & Head, Convergence & Communication

Division

Dept. of Information Technology

Ministry of Communications & IT, Govt. of India,

6, CGO Complex, New Delhi-110003 Mobile:

919810720007

I sincerely thank Department Of Information

Technology, Communication & Broadcast Technology

Cell (CC&BT) for providing me the project training and all

the necessary resources and expertise for this purpose.

ACKNOWLEDGEMENT

I am deeply grateful to Ms. Sapna singh & Mr. Sunil

gupta Faculty Of Electrical & Electronics Departent,

who gave us opportunity to work under his valuable

guidance. I sincerely thank him for showing me direction

and constantly providing me with words of inspiration. Her

kind and elderly advice always inspired us in putting my

best effort to develop an efficient project and for extending

full support during our project

Sanuj kumar

Siddharth singhal

Rakesh kumar

PREFACE

Excellence is an attitude that the whole of the human race

is born with. It is the environment that makes sure that

whether the result of this attitude is visible or otherwise.

The well planned, properly executed and evaluated

industrial training help a lot in including the good work

culture. It provides linkage between the student and

industry in order to develop the awareness of industrial

approach to problem solving based on board understanding

of process and mode of operation of an organization.

During this period, the student gets their first hand

experience on working in the actual environment. Most of

the theoretical knowledge that they have gained during the

course of their studies is to put to test here. Apart from this

the student gets the opportunity to learn the latest

technology, which immensely help them in their career. This

also benefits the organization as many students doing their

projects perform very well.

I had the opportunity to have the real practical experience,

which has increased my sphere of knowledge to a great

extent. Now I m better equipped to handle the real thing

than anyone else that has not undergone any such training.

During the training period I learned how an actual project

progresses, what sort of problems actually occur during the

development of such big projects, how to produce quality

products and so on. And being in such a reputed

organization, I had but the best exposure.

TABLE OF CONTENTSTitle Page No.

Organizational Profile

Introduction to Dept of IT

Organizational Structure of Ministry of IT

Introduction to Wireless Technology

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12

26

27

Evolution of Wireless Technology

Components of Wireless Technology

Wireless Sensor Networks

Platforms

Mobile Ad-Hoc Networks

Wireless Ad-Hoc Networks

Intelligent Transportation System

Objective of the Project

Brief Outline of the Project

Description of the Project

IEEE 802.11 Set of Standards for WLAN

Protocols: Summary

Protocols: Description

IEEE 802.11p (Dedicated Short Range

Communication)

IEEE 802.11j

IEEE 802.16j

Wi-Fi

Wi-Max

Bluetooth

Bluetooth vs. Wi-Fi in Networking

Vehicle-to-vehicle Communication

Application Challenges

Bibliography

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ORGANIZATIONAL PROFILE

Overview

The year 2006 witnessed a revalidation of Indian

Information Technology- Business Process Outsourcing (IT-

BPO) growth story, driven by a maturing appreciation of

India’s role and growing importance in global services

trade. Industries performance was marked by sustained

double-digit revenue growth, steady expansion into newer

service-lines and increased geographic penetration, and an

unprecedented investment by Multinational Corporations

(MNCs) - in spite of lingering gaps about gaps in talent and

infrastructure impacting India’s cost competitiveness. The

sector looks set to close the year at record levels, with the

revenue aggregate growing by nearly ten times over the

past 10 years.

The Indian IT-BPO sector is committed to extend its

unmatched reputation in quality, to information security and

is working on a four-pronged programme to achieve this

objective. This comprises: a) engaging key stakeholders

(policy makers, industry players, enforcement agencies,

etc). To build a common understanding of key issues

relating to information security- in the context of global

service delivery; b) educating industry constituents about

developments in information security policies and practices;

c) enactment of policy

reform required to ensure compliance; d) addicting in the

effective enforcement of policy frameworks by encouraging

the practice of periodic security audits and certification,

developing and maintaining an incident response database

and facilitating greater cooperation with enforcement

agencies.

National e-Governance Plan (NeGP)

The National Common Minimum Programme adopted by the

Government accords high priority to improving the quality

of basic governance and in that context has proposed to

promote e-Governance on a massive scale in areas of

concern to the common man.

At the State-level the Mission Mode Project (MMP) would

include services around road transport, land records,

commercial taxes, employment exchanges, agriculture, civil

supplies, treasuries, land registration, policy and education,

while at Central Level, it will cover areas such as insurance,

Central Excise, National ID, pensions, e-Posts, banking,

passport, visa and income-tax.

State Wide Area Network (SWAN)

Government has already approved a scheme for the

establishment of State Wide Area Networks (SWANs) at a

total outlay of Rs. 3,334 crore over a period of 5yaers. These

SWANs will extend data

Connectivity of 2Mbps up-to the block level in all States and

Union Territories in country. The block level nodes in turn,

will have a provision to extend connectivity further to

village level using contemporary wireless technology. Under

the scheme, proposal for 24 states/UTs have already been

sanctioned.

ELITEX 2007

Electronics and Information Technology Expansion 2007

(ELITEX 2007), an exhibition and seminar to showcase

technologies, products and services developed under the

aegis of Department of Information Technology, was held

during 10-11 January 2007 at India Habitat Centre, New

Delhi. This event provided an opportunity to close

interaction between academia, R&D institutions and

industries. Three technologies developed by the Department

institutions were transferred to industries for

commercialization and 16 new products/technologies were

released during the Exposition.

National Informatics Centre

For timely and faster delivery/retrieval of information, NIC

has connected all the State Centres with leased line/fibre

optics of

capacity ranging from 2-45 Mbps with backup links in 19

States. The districts have been provided 2 Mbps leased

lines. e-Filing of cases has been started in Supreme Court.

IT based Attendance Recording System has also been in

implemented for all employees of Supreme Court.

INTRODUCTION TO DEPARTMENT OF

INFORMATION TECHNOLOGY

Presently known as Department of Information Technology,

this Department was established in 1970 as Department of

Electronics (DoE) by Government of India as an

Independent Department directly reporting to Prime

Minister with a view to promote electronics sector in the

country. With the rapid growth of global technology, to

promote Information Technology in India (DoE) was

renamed as Ministry of Information Technology in 1999.

Further, it was felt that all departments related to

information technology, telecommunications and post

should be brought under one umbrella, as such Ministry of

Information Technology (MIT) was renamed as Ministry of

Communications and Information Technology (MCIT) in

2001 and all three departments namely Department of

Telecommunication (DOT), Department of Information

Technology (DIT) and Department of Post were put under

one Ministry.

Department of Information Technology (DIT) a Department

under MCIT acts as a motivator and promoter to spread IT

amongst the masses and ensures speedy IT led development

in the country. Within DIT, there are number of groups

operating in different thrust areas of IT. National

Informatics Center (NIC) an attached office under DIT is

the primary govt. body for informatics development and

networking in govt. and co-operative sectors. At the DIT

headquarters, a large number of application divisions exist

which provide total informatics support to other ministries

and departments of the central government.

At the state level, MCIT’S attached body NIC has its NIC

state centers that provide informatics supports to their

respective state govt. and the district level lie the NIC

District informatics support to provide effective informatics

support to the development, revenue and judiciary

administration of the district, in order to promote

information technology based value added services in the

area of industry, business and commerce. DIT has also

established twenty-two national information technology

promotional units (NITPU’S) at major industrial commercial

cities.

DIT offers state-of-the art network services in the country,

so as to facilitate economic social scientific and

technological activities. DIT implement it projects in

collaboration with the Center \ State Govt. in respect of

centrally sponsored schemes, central sector schemes, state

sector and state sponsored schemes and districts

administration sponsored projects.

Some of the spectrum of services provided by DIT

encompasses various dimensions of information technology

area can be broadly listed as under:

1. Consultancy

2. Software design and development

3. Networking

4. Research & Development

5. Computer Literacy Excellence Awards

6. Microelectronics Development Program

CONSULTANCY

DIT provides extensive consultancy services to clients. It

also grants permission for any new project being

undertaken by the government or any private organization.

Some of the services in this area including the following:

1. Business requirement analysis and mapping /Re-

engineering.

2. Granting permission to any foreign company which wants

to set up its IT related business in India.

3. Undertaking feasibility studies and software requirement,

specification to identify the prospective areas of automation

and IT application.

4. Setting up complete onsite infrastructure.

5. Procuring necessary hardware and installing customized

software.

SOFTWARE DESIGN AND DEVLOPMENT

NIC is a body working under DIT is producing quality

software at low cost. Since DIT is working at the grass root

levels of the development administration, its expertise is not

limited only to software engineering but also lies in the area

of implementing it in various sectors of the economy thus it

possesses domain expertise as much as expertise in the field

of software development, affect that provides NIC with a

solid foundation in the software development process. These

application software packages are completely indigenous

and user friendly and are intended to bring the benefits of

the latest advancements in it to the government’s

doorsteps.

NETWORKING

DIT provides effective networking solutions of all kinds to

its clients ranging from installation of entire networks to

providing specialized services over networks such as video

conferencing; electronic data interchange etc, through its

attached offices like NIC, regional test labs, autonomous

societies and so on. The basic networks services include

setting up the local area network or providing the Intranet

solutions at the users or premises as per-the requirement.

RESEARCH AND DEVELOPMENT

DIT has initiated a project during March'05 to set up a

National Resource Center for Free/Open Source Software

(NRCFOSS) in Chennai with an objective to contribute to

the growth of Free/Open Source Software in India through

research and development, human resource development,

networking and entrepreneurship development, as well as

to serve as the reference point for all FOSS related

activities in the country. The project is being executed by

CDAC and Anna University - KBC Center (AUKBC) Chennai

jointly.

While CDAC Chennai is engaged in “Products

Development”, AUKBC has been involved with “HR

development” in the area. NRCFOSS portal is operational

with domain name http://www.nrcfoss.org.in/.

The Center, among other things, has brought out an Indian

Linux distribution targeting to Indian requirements

including Indian language support. The distribution named

Bharat Operating System Solutions (BOSS) has successfully

undergone testing and certification by an International body

and is ready for deployment.

FUTURE PLANS

1) To promote the development, deployment and adoption of

FOSS tools, technologies, products, architectures and

solutions in various applications and domains (Education,

SMEs, Government environment and Localization).

2) To set up a nation-wide network of open source software

resource centers to address many of the concerns in FOSS

area.

3) To pursue International S&T cooperation with other

countries in area of FOSS.

SCHEME FOR COMPUTER LITERACY

EXCELLANCE AWARDS

The Department of Information Technology (DIT), in the

year 2002 has instituted an Award Scheme for Excellence in

Computer Literacy and Information Technology in Schools

at State and National Level to create IT awareness among

schools and to encourage Computer Literacy among

students in early stage of schooling. All recognized schools

in India, Government and Private, teaching Computers and

Information Technology in their schools are eligible to

compete for the award. The qualifying criteria will be based

on the performance of the school.

MICROELECTRONICS DEVELOPMENT

PROGRAM

Recognizing the importance of microelectronics for the

growth of IT and electronics industry in the country, the

Microelectronics Development Program was initiated in the

late 1980s. The thrust of the program has been to build a

strong R&D, industrial and highly trained manpower base

and encourage entrepreneurship. As a result, India has

already emerged as a leading global destination for VLSI

Design and it is at the threshold of attracting Megafabs.

Under the Microelectronics Development Program, the

Division sponsors R&D projects on the recommendation of

the Working Group on Microelectronics comprising of

experts from academia, R&D institutions and industries.

The broad areas covered under the program are as follows:

Microelectronics devices

VLSI Design and related software

Micro-Electro Mechanical Systems (MEMS)

Process Technology

THE ALLOCATION OF BUSINESS RULES

PERTAINING TO DIT

(As published in Part II, Section 3, Sub-section (ii) of

the Gazette of India, Extra Ordinary, Dated the 6th

January 2004. Doc. CD-8/2004)

Policy matters relating to Information Technology;

Electronics; and Internet (all matters other than

licensing of Internet Service Provider)

Promotion of Internet, IT and IT enabled services.

Assistance to other departments in the promotion of E-

Governance, E-Commerce, E-Medicine, E-

Infrastructure, etc.

Promotion of Information Technology education and

Information Technology-based education.

Matters relating to Cyber Laws, administration of the

Information Technology Act. 2000 (21 of 2000) and

other IT related laws.

Matters relating to promotion and manufacturing of

Semiconductor Devices in the country excluding all

matters relating to Semiconductor Complex Limited

(SCL) Mohali; The Semiconductor Integrated Circuits

Layout Design Act, 2000 (37 of 2000).

Interaction in IT related matters with International

agencies and bodies e.g. Internet for Business Limited

(IFB), Institute for Education in Information Society

(IBI) and International Code Council - on line (ICC).

Initiative on bridging the Digital Divide: Matters relating

to Media Lab Asia.

Promotion of Standardization, Testing and Quality in IT

and standardization of procedure for IT application and

Tasks.

Electronics Export and Computer Software Promotion

Council (ESC).

National Informatics Center (NIC)

Initiatives for development of Hardware/Software

industry including knowledge-based enterprises,

measures for promoting IT exports and

competitiveness of the industry.

All matters relating to personnel under the control of the

Department

DIT VISION/ THRUST AREAS

Vision

To make India an IT Super Power by the Year 2008. 

Vision Objectives

Creation of Wealth

Employment Generation

IT led Economic Growth

Roles of the Department of IT

Pro-active facilitator

Pro-active motivator

Pro-active promoter

Spread of IT to masses and ensure speedy IT led

development

THRUST AREAS OF THE DEPARTMENT OF

INFORMATION TECHNOLOGY

To facilitate and catalyze adoption of E-governance

packages in the Central and State Governments, as the

nodal agency for the implementation of the National E-

Governance Action Plan.

Evolve and implement policy packages to propel growth

of electronics and hardware manufacturing

Increase PC penetration in the country

Increase utilization of internet in the country

Growth of domestic software market

Development of local languages in Information

Technology

To encourage use of IT to increase productivity

To explore use of IT as a means of generating

employment

In addition, the Ministry is implementing the

following 10 Point Agenda

Shall aim at achieving convergence of Information,

Communication and Media Technologies. The

Department focus would be on PC penetration and

thereby bringing Cyber Connectivity to every

citizen.

To bring about transparency in administration and make

government functioning more citizen-centric, the

Department would stress on expeditious implementation

of the National E-governance Plan.

Broadband Connectivity: Providing broadband

connectivity to all, at the most reasonable prices.

Next Generation Mobile Wireless Technologies: Develop

4G technology for mobile telephony.

National Internet Exchange and Indian Domain Name:

To promote for enabling reduced bandwidth cost

and better security for internet traffic which

originates in India and has destination in India.

Migration to New Internet Protocol IPv6: To provide

policy framework and promotional measures in the

country to enable network providers to migrate to

IPv6.

Security & Digital Signature: To concentrate on Cyber

Infrastructure Protection and to promote the use of

Digital Signatures in the financial sector, judiciary

and education.

Media Lab Asia

Language Computing: To enable wide proliferation of

ICT in Indian languages

Outsourcing Skilled Manpower and R&D Thrust: To

make India the world's hub for outsourcing skilled

manpower in the IT sector.

ORGANISATIONS UNDER ADMINISTRATIVE

CONTROL OF DIT

Controller of Certifying Authorities (CCA)

Cyber Regulations Appellate Tribunal (CRAT)

Semiconductor Integrated Circuits Layout-Design

Registry

Computer Emergency Response Team (India) (CERT-In)

Attached Offices of DIT

Standardization, Testing and Quality Certification (STQC)

Directorate

National Informatics Center (NIC)

Section 25 Companies

Media Lab Asia

National Informatics Center Services Inc.(NICSI)

National Internet Exchange of India (NIXI)

Autonomous Societies of DIT

#Education & Research in Computer Networking

(ERNET)

Center for Development of Advanced Computing (C-DAC)

Center for Materials for Electronics Technology (C-MET)

DOEACC Society

Society for Applied Microwave Electronics Engineering

and Research (SAMEER)

Software Technology Parks of India (STPI)

Electronics and Computer Software Export Promotion

Council (ESC)

ORGANISATIONAL STRUCTURE OF DIT

INTRODUCTION TO WIRELESS TECHNOLOGY

Wireless Technology

The term wireless is normally used to refer to any type of electrical or electronic operation that is accomplished without the use of a "hard wired" connection, though they may be accomplished with the use of wires if desired. Wireless communication is the transfer of information over a distance without the use of electrical conductors or "wires". The distances involved may be short (a few meters as in television remote control) or very long (thousands or even millions of kilometers for radio communications). When the context is clear the term is often simply shortened to "wireless".

The term wireless technology is generally used for mobile IT equipment. It encompasses cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of wireless technology include GPS units, garage door openers and or garage doors, wireless computer mice and keyboards, satellite television and cordless telephones.

Wireless Communications

Various forms of wireless communications technologies have been proposed for intelligent transportation systems. Short-range communications (less than 500 yards) can be accomplished using IEEE 802.11 protocols specifically WAVE or the Dedicated Short Range Communications standard being promoted by the Intelligent Transportation Society of America and the United States Department of Transportation. Theoretically the range of these protocols can be extended using Mobile ad-hoc networks or Mesh networking.

4G is short for fourth-generation cellular communication

system. The 4G will be a fully IP-based integrated system of systems and network of networks achieved after the convergence of wired and wireless networks as well as computer, consumer electronics, communication technology, and several other convergences that will be capable of providing 100 Mbit/s and 1 Gbit/s, respectively, in outdoor and

indoor environments with end-to-end QoS and high security, offering any kind of services anytime, anywhere, at affordable cost and one billing.

The Wireless World Research Forum (WWRF) defines 4G as a network that operates on Internet technology, combines it with other applications and technologies such as Wi-Fi and WiMAX, and runs at speeds ranging from 100 Mbit/s (in cell-phone networks) to 1 Gbit/s (in local Wi-Fi networks). 4G is not just one defined technology or standard, but rather a collection of technologies and protocols to enable the highest throughput, lowest cost wireless network possible.

Historical Development and Standards

Much of this information is taken from [PC Tech Guide], which contains a thorough summary of communication network standards, topologies, and components.

Ethernet

The Ethernet was developed in the mid 1970’s by Xerox, DEC, and Intel, and was standardized in 1979. The Institute of Electrical and Electronics Engineers (IEEE) released the official Ethernet standard IEEE 802.3 in 1983. The Fast Ethernet operates at ten times the speed of the regular Ethernet, and was officially adopted in 1995. It introduces new features such as full-duplex operation and auto-negotiation. Both these standards use IEEE 802.3 variable-length frames having between 64 and 1514-byte packets.

Token Ring

In 1984 IBM introduced the 4Mbit/s token ring network. The system was of high quality and robust, but its cost caused it to fall behind the Ethernet in popularity. IEEE standardized the token ring with the IEEE 802.5 specification. The Fiber Distributed Data Interface (FDDI) specifies a 100Mbit/s token-passing, dual-ring LAN that uses fiber optic cable. The American National Standards Institute (ANSI) developed it in the mid 1980s, and its speed far exceeded current capabilities of both Ethernet and IEEE 802.5.

Gigabit Ethernet

The Gigabit Ethernet Alliance was founded in 1996, and the Gigabit Ethernet standards were ratified in 1999, specifying a physical layer that uses a mixture of technologies from the original Ethernet and fiber optic cable technologies from FDDI.

Client-Server networks

These became popular in the late 1980’s with the replacement of large mainframe computers by networks of personal computers. Application programs for distributed computing environments are essentially divided into two

parts: the client or front end, and the server or back end. The user’s PC is the client and more powerful server machines interface to the network.

Peer-to-Peer networking

These architectures have all machines with equivalent capabilities and responsibilities. There is no server, and computers connect to each other, usually using a bus topology, to share files, printers, Internet access, and other resources.

Peer-to-Peer Computing

It is a significant next evolutionary step over P2P networking. Here, computing tasks are split between multiple computers, with the result being assembled for further consumption. P2P computing has

sparked a revolution for the Internet Age and has obtained considerable success in a very short time. The Napster MP3 music file sharing application went live in September 1999, and attracted more than 20 million users by mid 2000.

802.11 Wireless Local Area Network

IEEE ratified the IEEE 802.11 specification in 1997 as a standard for WLAN. Current versions of 802.11 (i.e. 802.11b) support transmission up to 11Mbit/s. WiFi, as it is known, is useful for fast and easy networking of PCs, printers, and other devices in a local environment, e.g. the home.Current PCs and laptops as purchased have the hardware to support WiFi. Purchasing and installing a WiFi router and receivers is within the budget and capability of home PC enthusiasts.

Bluetooth

Bluetooth was initiated in 1998 and standardized by the IEEE as Wireless Personal Area Network (WPAN) IEEE 802.15. Bluetooth is a short range RF technology aimed at facilitating communication of electronic devices between each other and with the Internet, allowing for data synchronization that is transparent to the user. Supported devices include PCs, laptops, printers, joysticks, keyboards, mice, cell phones, PDAs, and consumer products. Mobile devices are also supported. Discovery protocols allow new devices to be hooked up easily to the network. Bluetooth uses the unlicensed 2.4 GHz band and can transmit data up to 1Mbit/s, can penetrate solid non-metal barriers, and has a nominal range of 10m that can be extended to 100m. A master station can service up to 7 simultaneous slave links. Forming a network of these networks, e.g. a Pico net, can allow one master to service up to 200 slaves.Currently, Bluetooth development kits can be purchased from a variety of suppliers, but the systems generally require a great deal of time, effort, and knowledge for programming and debugging. Forming Pico nets has not yet been streamlined and is unduly difficult.

Home RF

This was initiated in 1998 and has similar goals to Bluetooth for WPAN. Its goal is shared data/voice transmission. It interfaces with the Internet as well as the Public Switched Telephone Network. It uses the 2.4 GHz band and has a range of 50 m, suitable for home and yard. A maximum of 127 nodes can be accommodated in a single network. IrDA is a WPAN technology that has a short-range, narrow-transmission-angle beam suitable for aiming and selective reception of signals.

EVOLUTION OF WIRELESS TECHNOLOGY

First Generation

Almost all of the systems from this generation were analog systems where voice was considered to be the main traffic. These systems could often be listened to by third parties. Some of the standards are NMT, AMPS, Hicap, CDPD, Mobitex, and DataTac.

Second Generation

All the standards belonging to this generation are commercial centric and they are digital in form. The second generation standards are GSM, iDEN, D-AMPS, IS-95, PDC, CSD, PHS, GPRS, HSCSD, and WiDEN.

Third Generation

To meet the growing demands in the number of subscribers (increase in network capacity), rates required for high speed data transfer and multimedia applications 3G standards started evolving. The systems in this standard are basically a linear enhancement of 2G systems. They are based on two parallel backbone infrastructures, one consisting of circuit switched nodes, and one of packet oriented nodes. Currently, transition is happening from 2G to 3G systems. Some of the 3G standards are EDGE and EGPRS (sometimes denoted 2.75G),CDMA 2000,W-CDMA or UMTS (3GSM), FOMA, 1xEV-DO/IS-856, TD-SCDMA, GAN/UMA, 3.5G - HSDPA, 3.75G - HSUPA. The ITU defines a specific set of air interface technologies as third generation, as part of the IMT-2000 initiative.

Fourth Generation

According to 4G working groups, the infrastructure and the terminals will have almost all the standards from 2G to 3G implemented. The infrastructure will however only be packet based all-IP. Some of the standards that pave the way for 4G systems are Wi-Fi, WiMax,

WiBro, and the proposed 3GPP Long Term Evolution work-in-progress technologies HSOPA.

COMPONENTS OF WIRELESS TECHNOLOGY

1. Access Schemes:

The existing wireless standards use TDMA, FDMA, CDMA and combinations of these to multiplex multiple mobile stations (handsets, etc) use of spectrum, with CDMA (IS-2000, W-CDMA, TD-CDMA, TD-SCDMA) dominating the 3G space. However, all these technologies are limited; TDMA suffers from inherent inefficiencies due to the need for guard periods between frames, and CDMA from poor spectrum flexibility and scalability.

Recently, new access schemes like OFDMA, Single Carrier FDMA, and MC-CDMA have been proposed as part of the upcoming next generation UMTS, 802.16e and 802.20 standards. These offer the same efficiencies as older technologies like CDMA, but offer advantages in scalability.1.1 OFDMAOrthogonal Frequency Division Multiple Access (OFDMA) is a multi-user version of the popular OFDM digital modulation scheme. Multiple accesses are achieved in OFDMA by assigning subsets of sub carriers to individual users as shown in the figure below. This allows simultaneous low data rate transmission from several users.

Based on feedback information about the channel conditions, adaptive user-to-sub carrier assignment can be achieved. If the assignment is done sufficiently fast, this further improves the OFDM robustness to fast fading and narrow-band co channel interference, and makes it possible to achieve even better system spectral efficiency.

Different number of sub-carriers can be assigned to different users, in view to support differentiated Quality of Service (QoS), i.e. to control the data rate and error probability individually for each user.

OFDMA resembles code division multiple access (CDMA) spread spectrum, where users can achieve different data rate by assigning different code spreading factor or different number of spreading codes to each user.

OFDMA can also be seen as an alternative to combining OFDM with time division multiple access (TDMA) or time-domain statistical multiplexing, i.e. packet mode communication. Low data rate users can send continuously with low transmission power instead of using a "pulsed" high-power carrier. Constant delay, and shorter delay, can be achieved.

However, OFDMA can also be described as a combination of frequency domain and time domain multiple accesses, where the resources are partitioned in the time-frequency space and slots are assigned along the OFDM symbol index as well as OFDM sub-carrier index.#1.1(a) Advantages over CDMA

OFDM can combat fading with less complexity.OFDMA can achieve higher spectral efficiency.

1.1(b) Advantages of OFDM over time-domain statistical multiplexing

Allows simultaneous low data rate transmission from several users.

Pulsed carrier can be avoided.Lower maximum transmission power for low data rate

users.

Shorter delay and constant delay.Contention based multiple access (collision avoidance) is

simplified.Further improves OFDM robustness to fading and

interference.

1.1(c) Disadvantages

Asynchronous data communication services such as web access are characterized by short communication bursts at high data rate. Few users in a base station cell are transferring data simultaneously at low constant data rate.

The complex OFDM electronics, including the FFT algorithm and forward error correction, is constantly active independent on the data rate, which is inefficient from power consumption point of view, while OFDM combined with data packet scheduling may allow that the FFT algorithm hibernates during certain time intervals.

The OFDM diversity gain, and resistance to frequency-

selective fading, may partly be lost if very few sub-carriers are assigned to each user, and if the same carrier is used in every OFDM symbol. Adaptive sub-carrier assignment based on fast feedback information about the channel, or sub-carrier frequency hopping, is therefore desirable.

Dealing with co-channel interference from nearby cells is more complex in OFDM than in CDMA. It would require dynamic channel allocation with advanced coordination among adjacent base stations. The fast channel feedback information and

adaptive sub-carrier assignment is more complex than CDMA fast power control.

1.1(d) Usage

OFDMA is used in the mobility mode of IEEE 802.16 Wireless MAN Air Interface standard, commonly referred to as WiMAX. OFDMA is currently a working assumption in 3GPP Long Term Evolution downlink, named High Speed OFDM Packet Access (HSOPA). Also, OFDMA is the candidate access method for the IEEE 802.22 "Wireless Regional Area Networks". The project aims at designing the first cognitive radio based standard operating in the VHF-low UHF spectrum (TV spectrum).

The term "OFDMA" is claimed to be a registered trademark by Runcom Technologies Ltd., with various other claimants to the underlying technologies through patents.

In addition to improvements in these multiplexing systems, improved modulation techniques are being used. Whereas earlier standards largely used Phase-shift keying, more efficient systems such as 64QAM are being proposed for use with the 3GPP Long Term Evolution standards.

1.2 Network Layer Technology (IPv6)

Unlike the 3G networks which are a jumble of circuit switched and packet switched networks, 4G will be based on packet switching only. This will require low-latency data transmission.

It is generally believed that 4th generation wireless networks would support a great number of wireless devices that are addressable and routable. Therefore, in the context of 4G, IPv6 is an important network layer technology and standard that can support a great number of wireless enabled devices. By increasing the number of IP addresses, IPv6 removes the need for Network Address Translation (NAT), a current workaround used to mitigate the dwindling number of IPv4 addresses.

In the context of 4G, IPv6 also enables a number of applications with better multi-cast, security and route optimization capabilities. With the available address space and number of addressing bits in IPv6, many innovative coding schemes can be developed for 4G devices and applications that could aid deployment of 4G networks and services.

1.3 Transmission schemes (Multi-Antenna Systems)

In the early 90s, to cater the growing data rate needs of data communication, many transmission schemes were proposed. One technology, spatial multiplexing, gained importance for its bandwidth

conservation and power efficiency. Spatial multiplexing involves deploying multiple antennas at the transmitter and at the receiver. Independent streams can be transmitted simultaneously from all the antennas. This increases the data rate into multiple folds with the number equal to minimum of the number of transmit and receive antennas. This is called as Multiple-input multiple-output

communications (MIMO). Apart from this, the reliability in transmitting high-speed data in the fading channel can be improved by using more antennas at the transmitter or at the receiver. This is called transmit or receive diversity.

WIRELESS SENSOR NETWORKS

A wireless sensor network (WSN) is a network made of many small computers or processing the sensor data. A sensor network is a computer network of many, spatially distributed devices using sensors to monitor conditions at different locations, such as temperature, sound, vibration, pressure, motion or pollutants. Usually these devices are small and inexpensive, so that they can be produced and deployed in large numbers, and so their resources in terms of energy, memory, computational speed and bandwidth are severely constrained. Each device is equipped with a radio transceiver, a small microcontroller, and an energy source, usually a battery. The devices use each other to transport data to a monitoring computer.

Wireless sensor networks (WSN) have emerged to take the concept of information gathering, dissemination, monitoring and control to a completely new level. This technology seamlessly dovetails into the existing Internet technology. A wireless sensor network is composed of large number of nodes densely deployed either inside the area of interest or very close to it. The advantage here is, the position of sensor nodes is not predetermined and may very well be random or mobile; this allows random and easy deployment in the area which is not easily accessible. Such an approach provides several advantages over traditional networking methods:

It enables remote monitoring and control.Large-scale, dense deployment extends the spatial

coverage and achieves higher data resolution.

WSN is fault tolerant and robust.The ad-hoc nature and deploy them and leave them vision

makes it more attractive in military applications and other risk-associated applications.

WSN are ideally suited for applications like habitat monitoring, environmental monitoring, target detection, surveillance, health care, warehouse inventory tracking, and many others areas.

Sensor networks involve three areas: sensing, communications, and computation (hardware, software, algorithms). Very useful technologies are wireless database technology such as queries, used in a wireless sensor network, and network technology to communicate with other sensors, esp by Motorola in home control systems.ecially multihop routing protocols. For example, Zigbee is a wireless protocol used by Motorola in home control systems.

Figure: Typical Wireless Sensor Network Architecture

A wireless sensor network (WSN) is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations. The development of wireless sensor networks was originally motivated by military applications such as battlefield surveillance. However, wireless sensor networks are now used in many civilian application areas, including environment and habitat monitoring, healthcare

applications, home automation, and traffic control.

In addition to one or more sensors, each node in a sensor network is typically equipped with a radio transceiver or other wireless communications device, a small microcontroller, and an energy source, usually a battery. The size of a single sensor node can vary from shoebox-sized nodes down to devices the size of grain of dust. The cost of sensor nodes is similarly variable, ranging from hundreds of dollars to a few cents, depending on the size of the sensor network and the complexity required of individual sensor nodes. Size and cost constraints on sensor nodes result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth.

In computer science, wireless sensor networks are an active research area with numerous workshops and conferences arranged each year.

Characteristics of WSN

Unique characteristics of a WSN are:Small-scale sensor nodesLimited power they can harvest or storeHarsh environmental conditionsNode failuresMobility of nodesDynamic network topologyCommunication failuresHeterogeneity of nodesLarge scale of deploymentUnattended operation

Sensor nodes can be imagined as small computers, extremely basic in terms of their interfaces and their

components. They usually consist of a processing unit with limited computational power and limited memory, sensors (including specific conditioning circuitry), a communication device (usually radio transceivers or alternatively optical), and a power source usually in the form of a battery. Other possible inclusions are energy harvesting modules, secondary ASICs, and possibly secondary communication devices (e.g. RS232 or USB).

The base stations are one or more distinguished components of the WSN with much more computational, energy and communication resources. They act as a gateway between sensor nodes and the end user.

Network Topology

The basic issue in communication networks is the transmission of messages to achieve a prescribed message throughput (Quantity of Service) and Quality of Service (QoS). QoS can be specified in terms of message delay, message due dates, bit error rates, packet loss, economic cost of transmission, transmission power, etc. Depending on QoS, the installation environment, economic considerations, and the application, one of several basic network topologies may be used.

A communication network is composed of nodes, each of which has computing power and can transmit and receive messages over communication links, wireless or cabled. The basic network topologies are shown in the figure and include fully connected, mesh, star, ring, tree, bus. A single network may consist of several interconnected subnets of different topologies. Networks are further classified as Local Area Networks (LAN), e.g. inside one building, or Wide Area Networks (WAN), e.g. between buildings.

Fully connected networks suffer from problems of NP-complexity as additional nodes are added, the number of

links increases exponentially. Therefore, for large networks, the routing problem is computationally intractable even with the availability of large amounts of computing power.

Mesh networks are regularly distributed networks that generally allow transmission only to a node’s nearest neighbors. The nodes in these networks are generally identical, so that mesh nets are also referred to as peer-to-peer nets. Mesh nets can be good models for large-scale networks of wireless sensors that are distributed over a geographic region, e.g. personnel or vehicle security surveillance systems. Note that the regular structure reflects the communications topology; the actual geographic distribution of the nodes need not be

a regular mesh. Since there are generally multiple routing paths between nodes, these nets are robust to failure of individual nodes or links. An advantage of mesh nets is that, although all nodes may be identical and have the same computing and transmission capabilities, certain nodes can be designated as ‘group leaders’ that take on additional functions. If a group leader is disabled, another node can then take over these duties.

All nodes of the star topology are connected to a single hub node. The hub requires greater message handling, routing, and decision-making capabilities than the other nodes. If a communication link is cut, it only affects one node. However, if the hub is incapacitated the network is destroyed. In the ring topology all nodes perform the same function and there is no leader node. Messages generally travel around the ring in a single direction.

However, if the ring is cut, all communication is lost. The self-healing ring network (SHR) shown has two rings and is more fault tolerant.

In the b, messages are broadcast on the bus to all nodes. Each node checks the destination address in the message header, and processes the messages addressed to it. The bus topology is passive in that each node simply listens for messages and is not responsible for retransmitting any messages.

PLATFORMS

Sensors

Sensors are hardware devices that produce measurable response to a change in a physical condition like temperature and pressure. Sensors sense or measure physical data of the area to be monitored. The continual analog signal sensed by the sensors is digitized by Analog-to-Digital converter and sent to controllers for further processing. Characteristics and requirements of Sensor node should be small size, consume extremely low energy, operate in high volumetric densities, are autonomous and operate unattended, and be adaptive to the environment. As wireless sensor nodes are micro-electronic sensor device, can only be equipped with a limited power source of less than 0.5Ah and 1.2 V. Sensors are classified into three categories.

Passive, Omni Directional Sensors: Passive sensors sense the data without actually manipulating the environment by active probing. They are self powered i.e. energy is needed only to amplify their analog signal. There is no notion of “direction” involved in these measurements.

Passive, narrow-beam sensors: These sensors are passive but they have well-defined notion of direction of measurement. Typical example is ‘camera’.

Active Sensors: These groups of sensors actively probe the environment, for example, sonar or radar sensor or some type of seismic sensor, which generate shock waves by small explosions.

The overall theoretical work on WSN’s considers Passive, Omni directional sensors. Each sensor node has a certain area of coverage for which it can reliably and accurately report the particular quantity that it is observing. Several sources of power consumption in sensors are a) Signal sampling and conversion of physical signals to electrical ones, b) signal conditioning, and c) analog-to-digital conversion. Spatial density of sensor nodes in the field may be ashighas20nodes/m3.

Wireless sensor networks represent an entirely new way of looking at computing. In a sensor network thousands of tiny, battery-powered computers, often called "motes," are scattered throughout a physical environment. Silently and wirelessly, each mote in this ad hoc network collects data, for instance, monitoring light, temperature, humidity, vibration or other environmental factors. The mote relays the collected data to its neighboring motes and then to a specified destination where it is processed. This sensory input, when gathered from all the motes and analyzed by more traditional computers, paints a comprehensive, high-resolution picture of the surroundings in real time.

Power Management Of Wireless Sensors

With the advent of ad hoc networks of geographically distributed sensors in remote site environments (e.g. sensors dropped from aircraft for personnel/vehicle surveillance), there is a focus on increasing the lifetimes of sensor nodes through power generation, power conservation, and power management. Current research is in designing small MEMS (microelectromechanical systems) RF components for transceivers, including capacitors, inductors, etc. The limiting factor now is in fabricating micro sized inductors. Another thrust is in designing MEMS power generators using technologies including solar, vibration (electromagnetic and electrostatic), thermal, etc.

RF-ID (RF identification) devices are transponder microcircuits having an L-C tank circuit that stores power from received interrogation signals, and then uses that power to transmit a response. Passive tags have no onboard power source and limited onboard data storage, while active tags have a battery and up to 1Mb

of data storage. RF-ID operates in a low frequency range of 100 kHz-1.5MHz or a high frequency range of 900 MHz-2.4GHz, which has an operating range up to 30m. RF-ID tags are very inexpensive, and are used in manufacturing and sales inventory control, container shipping control, etc. RF-ID tags are installed on water meters in some cities, allowing a metering vehicle to simply drive by and remotely read the current readings. They are also be used in automobiles folded beam suspension.

Meanwhile, software power management techniques can greatly decrease the power consumed by RF sensor nodes. TDMA is especially useful for power conservation, since a node can power down or ‘sleep’ between its assigned time slots, waking up in time to receive and transmit messages. The required transmission power increases as the square of the distance between source and destination.

Therefore, multiple short message transmission hops require less power than one long hop. In fact, if the distance between source and destination is R, the power required for single-hop transmission is proportional to R2. If nodes between source and destination are taken advantage of to transmit n short hops instead, the power required by each node is proportional to R2/n2. This is a strong argument in favor of distributed networks with multiple nodes, i.e. nets of the mesh variety.

A current topic of research is active power control, whereby each node cooperates with all other nodes in selecting its individual transmission power level. This is a decentralized feedback control problem.

Congestion is increased if any node uses too much power, but each node must select a large enough transmission range that the network remains connected. For n nodes randomly distributed in a disk, the network is asymptotically connected with probability one if the

transmission range r of all nodes is selected using

Where y (n) is a function that goes to infinity as n becomes large.

ZigBee

ZigBee is the name of a specification for a suite of high level communication protocols using small, low-power digital radios based on the IEEE 802.15.4 standard for wireless personal area networks (WPANs). ZigBee is targeted at RF applications that require a low data rate, long battery life, and secure networking.

ZigBee Technology

#The idea behind ZigBee is to develop a standardized specification upon which low-power wireless sensor networks can operate and be interoperable. The ZigBee specification sits on top of the physical (PHY) and medium access control (MAC) layers of the IEEE802.15.4 standard.

The IEEE802.15.4 standard is focused on low-rate personal area networking with key unique features of low-power, packet-based, highly-secure, large networks at low-cost that will co-exist with other wireless networks (such as Wi-Fi). These make ZigBee suitable for reliable, low-power, wireless data communications for monitoring and control devices.

The ZigBee standard provides more complex network topologies such as tree and mesh networks, standardization and compliance, profiles for various applications and

marketing activities. ZigBee divides the network into three layers, layer 1 being the PHY and MAC (IEEE802.15.4), layer 2 being the mesh network and layer 3 being the profiles.

The level 1 network layer (unique to the IEEE802.15.4 PHY and MAC) was established in 2003 and provides a number of features which are keys to wireless sensor networks pervading industrial, commercial buildings and home applications. As an example, networks will not be deployed in a commercial building unless they have the features of low-power, high level of security, long range, small size and will not interfere with a Wi-Fi network.

The level 2 network layer provides tree or mesh networking and has been established since 2005. Typically a mesh network comprises controllers (or full-function devices), routers and endpoints or reduced function devices (RFD). The key feature of a mesh network is to be able to dynamically add and remove devices (whether routers or endpoints) and the network adapts around the changes. A wide variety of network topologies can be configured, from long, thin networks to wide, fat networks.

At level 3 the ZigBee Alliance creates a number of profiles for common applications. This is at an early stage and will develop over time.

Application DiversityThere are a lot of talks in wireless markets of killer applications. Wireless sensor network products and applications won’t have a single killer application, but hundreds of killer applications. The key to understanding the potential diversity of applications is to start from the standpoint of how to enable a specific application, rather than how to implement the standard. In other words, don’t think ZigBee, but instead, think applications.Applications based on this standard are not just limited to one specific market. Its possible to create networks from simple point-to-point networks to ZigBee compliant mesh networks in

anything from industrial and commercial buildings, to home automation, personal healthcare and more.

#In a typical home automation scenario (Fig 2), intelligent sensors can provide flexible control of lighting, heating, cooling, watering, appliances and security systems C from anywhere in the home. The potential benefits include the ability to adjust the home environment to run more efficiently and to reduce utility costs. In such an environment, the interoperable nature of the ZigBee standard means that even off-the-shelf products should work together in the networked environment. The fact that ZigBee is targeted at applications

requiring low power, such as light switches and sensors, means that many of the sensors and nodes can operate using standard batteries for possibly years.Another main advantage of ZigBee-based networks in a home automation application or even any industrial or other application is that builders and contractors can easily reconfigure heating, lighting, and security systems to accommodate additional sensors and nodes.

UsesZigBee provides the foundation to wirelessly communicate with its mesh network stacks, interoperability and co-existence with other networks.ZigBee protocols are intended for use in embedded applications requiring low data rates and low power consumption. ZigBee's current focus is to define a general-purpose, inexpensive, self-organizing, mesh network that can be used for industrial control, embedded sensing, medical data collection, smoke and intruder warning, building automation, home automation, domotics, etc. The resulting network will use very small amounts of power so individual devices might run for a year or two using the originally installed battery.

Device typesThere are three different types of ZigBee device:

ZigBee coordinator (ZC): The most capable device, the coordinator forms the root of the network tree and might bridge to other networks. There is exactly one ZigBee coordinator in each network since it is the device that started the network originally. It is able to store information about the network, including acting as the Trust Centre & repository for security keys.

ZigBee Router (ZR): As well as running an application function a router can act as an Intermediate router, passing data from other devices.

ZigBee End Device (ZED): Contains just enough functionality to talk to its parent node (either the coordinator or a router); it cannot relay data from other devices. This relationship allows the node to be asleep a

significant amount of the time thereby giving you the much quoted long battery life. A ZED requires the least amount of memory, and therefore can be less expensive to manufacture than a ZR or ZC.

MOBILE AD-HOC NETWORK

A mobile ad-hoc network (MANet) is a kind of wireless ad-hoc network, and is a self-configuring network of mobile routers (and associated hosts) connected by wireless links – the union of which form an arbitrary topology. The routers are free to move randomly and organize themselves arbitrarily; thus, the network's wireless topology may change rapidly and unpredictably. Such a network may operate in a standalone fashion, or may be connected to the larger Internet.

Mobile ad hoc networks became a popular subject for research as laptops and 802.11/Wi-Fi wireless networking became widespread in the mid to late 1990s. Many of the academic papers evaluate protocols and abilities assuming varying degrees of mobility within a bounded space, usually with all nodes within a few hops of each other, and usually with nodes sending data at a constant rate. Different protocols are then evaluated based on the packet drop rate, the overhead introduced by the routing protocol, and other measures.

The Children's Machine One Laptop per Child program hopes to develop a cheap laptop for mass distribution (>1 million at a time) to developing countries for education. The laptops will use IEEE 802.11s based ad hoc wireless mesh networking to develop their own communications network

out of the box.

Vehicular Ad Hoc Networks (VANET) are a form of MANets used for communication among vehicles and between vehicles and roadside equipment.

Intelligent Vehicular AdHoc Network (InVANET) is a kind of Intelligence in Vehicle(s) that provide multiple autonomic intelligent solutions to make automotive vehicles to behave in intelligent manner during vehicle-to-vehicle collisions, accidents, drunken driving etc. InVANET uses WiFi IEEE 802.11 b/802.11g/802.11p and WiMAX IEEE 802.16 for providing easy, accurate, effective communication between multiple vehicles on dynamic mobility. Effective measures to track the automotive vehicles, media download /upload, conference

between vehicles are also preferred. InVANET can also be applied for artillery vehicles during warfare / Battlefield / Peace operations.

WIRELESS AD-HOC NETWORK

A wireless ad-hoc network is a computer network in which the communication links are wireless. The network is ad hoc because each node is willing to forward data for other nodes, and so the determination of which nodes forward data is made dynamically based on the network connectivity. This is in contrast to wired network technologies in which some designated nodes, usually with custom hardware and variously known as routers, switches, hubs, and firewalls, perform the task of forwarding the data. It is also in contrast to managed wireless networks, in which a special node known as an access point manages communication among other nodes.

Minimal configuration and quick deployment make ad hoc networks suitable for emergency situations like natural disasters or military conflicts. The decentralized nature of most wireless ad hoc networks makes them suitable for a variety of applications where central nodes cannot be relied on, and may improve the scalability of wireless ad-hoc networks compared to wireless managed networks, though theoretical[1] and practical [2] limits to the overall capacity of such networks have been identified.

Types of wireless ad-hoc networks include Mobile ad hoc networks (MANets), wireless mesh networks, and wireless sensor networks.In most wireless ad-hoc networks the nodes compete to access the shared wireless medium (the "ether"), often resulting in collisions. Using Cooperative wireless communications improves immunity to interference by having the destination node combine self-interference and other-node interference to improve decoding of the desired signal.

The earliest wireless ad hoc networks were called "packet radio" networks, and were sponsored by DARPA.

INTELLIGENT TRANSPORTATION SYSTEM

The Intelligent Transportation Systems (ITS) program is a worldwide initiative to add information and communications technology to transport infrastructure and vehicles. It aims to manage factors that are typically at odds with each other such as vehicles, loads, and routes to improve safety and reduce vehicle wear, transportation times and fuel consumption.

Intelligent Transportation Technologies

Intelligent transportation systems vary in technologies applied, from basic management systems such as car navigation, traffic signal control systems, container management systems, variable message signs or speed cameras to monitoring applications such as security CCTV systems, and then to more advanced applications which integrate live data and feedback from a number of other sources, such as Parking Guidance and Information systems, weather information, bridge de-icing systems, and the like. Additionally, predictive techniques are being developed, to allow advanced modeling and comparison with historical baseline data. Some of the constituent technologies typically implemented in ITS, are described in the following sections.

In the period from 1992 to around 1995 the ITS sector was known as Intelligent Vehicle Highway Systems (IVHS). At the time it was recognized that all forms of transport could benefit from the application of information and communications technologies (ICT). However the term ICT had not yet been described in popular vernacular. The global leaders in ITS at the time then determined that there needed to be a term to describe the application of ICT to transport and coined the term Intelligent Transportation Systems.

Floating Car Data; Floating Cellular Data (FCD)

Virtually every car contains one or more mobile phones. These mobile phones routinely transmit their location information to the network – even when no voice connection

is established. These cellular phones in cars are used as anonymous traffic probes. As the car moves, so does the signal of the mobile phone. By measuring and analyzing triangulation network data – in an anonymized format – the data is converted into accurate traffic flow information. The more congestion, the more cars, the more phones and thus more probes. In metropolitan areas the distance between antennas is shorter and, thus, accuracy increases. No infrastructure need be built along the road - only the mobile phone network is leveraged. The FCD technology provides great advantages over existing methods of traffic measurement:

much less expensive than sensors or cameras more coverage: all locations and streets faster to set up (no work zones) and less maintenance works in all weather conditions, including heavy rain

Sensing Technologies

State-of-the-art sensor technologies have greatly enhanced the technical capabilities and safety benefits awaiting Intelligent transportation systems around the world. Sensing systems for ITS can be either infrastructure based or vehicle based systems, or both - see, for example, Intelligent vehicle technologies. Infrastructure sensors are devices that are installed or embedded on the road, or surrounding the road (buildings, posts, and signs for example). These sensing technologies may be installed during preventive road construction maintenance or by sensor injection machinery for rapid deployment of road in-ground sensors. While vehicle sensors are those devices installed on the road or in the vehicle, new technology development has also enabled cellular phones to become anonymous traffic probes, such as floating car data.

Inductive Loop Detection

Inductive loops can be placed in a roadbed to detect vehicles as they pass over the loop by measuring the vehicle's magnetic field. The simplest detectors simply count the number of vehicles during a unit of time (typically 60 seconds in the United States) that pass over the loop, while more sophisticated sensors estimate the speed, length and weight of vehicles and the distance between them. Loops can be placed in a single lane or across multiple lanes, and they work with very slow or stopped vehicles as well as vehicles moving at high-speed.

Video Vehicle Detection

Traffic flow measurement and Automatic Incident Detection using video cameras is another form of vehicle detection. Since video detection systems do not involve installing any components directly into the road surface or roadbed, this type of system is known as a "non-intrusive" method of traffic detection. Video from black-and-white or color cameras is fed into processors that analyze the changing characteristics of the video image as vehicles pass. The cameras are typically mounted on poles or structures above or adjacent to the roadway. Most video detection systems require some initial configuration to "teach" the processor the baseline background image. This usually involves inputting known measurements such as the distance between lane lines or the height of the camera above the roadway. A single video detection processor can detect traffic simultaneously from one to eight cameras, depending on the brand and model. The typical output from a video detection system is lane-by-lane vehicle speeds, counts and lane occupancy readings. Some systems provide additional outputs including gap, headway, stopped-vehicle detection and wrong-way vehicle alarms.

Intelligent Transportation Applications

Electronic Toll Collection

Electronic toll collection (ETC) makes it possible for vehicles to drive through toll gates at traffic speed, reducing congestion at toll plazas and automating toll collection. Originally ETC systems were used to automate toll collection, but more recent innovations have used ETC to enforce congestion pricing through cordon zones in city centers and ETC Lanes.

Until recent years most ETC systems were based on using radio devices in vehicles that would use proprietary protocols to identify a vehicle as it passed under a gantry over the roadway. More recently there has been a move to standardize ETC protocols around the Dedicated Short Range Communications protocol that has been promoted for vehicle safety by the Intelligent Transportation Society of America, ERTICO and ITS Japan.

Whilst communication frequencies and standards do differ around the world there has been a broad push toward Vehicle Infrastructure Integration (VII) around the 5.9GHz frequency (802.11.x WAVE).

ITS Australia also facilitated via its National Electronic Tolling Committee representing all jurisdictions and toll

road operators interoperability of toll tags in Australia for the multi lane free flow tolls roads.

Other systems that have been used include barcode stickers, license plate recognition, infrared communication systems and Radio Frequency Identification Tags (see M6 Toll tag).

Emergency Vehicle Notification Systems

The in-vehicle eCall is an emergency call generated either manually by the vehicle occupants or automatically via activation of in-vehicle sensors after an accident. When activated, the in-vehicle eCall device will establish an emergency call carrying both voice and data directly

to the nearest emergency point (normally the nearest 112 Public Safety Answering Point, PSAP). The voice call enables the vehicle occupant to communicate with the trained eCall operator. At the same time, a minimum set of data will be sent to the eCall operator receiving the voice call.

The minimum set of data contains information about the incident, including time, precise location, the direction the vehicle was travelling and vehicle identification. The pan-European eCall aims to be operative for all new type-approved vehicles as a standard option. Depending on the manufacturer of the eCall system, it could be mobile phone based (Bluetooth connection to an in-vehicle interface), an integrated eCall device, or a functionality of a broader system like navigation, Telematics device, tolling device. eCall is expected to be offered at the end of 2010, at the earliest, pending standardisation by the European Telecommunication Standardization Institute (ETSI) and commitment from large EU member states like France and the United Kingdom.

Cordon Zones With Congestion Pricing

Cordon zones have been implemented in Singapore, Stockholm and London where a special fee is collected (see Congestion pricing) from vehicles entering a congested city center. This fee or toll is charge automatically using Electronic toll collection or licence plate recognition technology, since stopping the users at conventional toll booths would cause long queues, long delays and even gridlock.

Figure: Many ETC systems use transponders like this one to electronically debit the accounts of registered cars without

their stopping.

Figure: Transponder used in some Chilean expressways

Figure: Electronic Road Pricing Gantry at North Bridge Road, Singapore

Co-operative Systems on the Road

Cooperation on road includes Car to Car, Car to Infrastructure and vice versa communication. Data which is available at the vehicle is acquired and transmitted to a server for central fusion and processing. This data can be used to detect events such as rain (wiper activity) and congestion (frequent breaking activities). Cooperative systems will support the driver at his driving tasks. The system will be based on a wireless data transmission network. The server processes a driving recommendation dedicated to a single or a specific group of drivers and transmits it wireless and directly to the vehicle. The goal of cooperative systems is to utilise and plan communication

and sensor infrastructure to increase road safety.

The definition of cooperative systems in road traffic is according to the European Commission: “Road operators, infrastructure, vehicles, their drivers and other road users will cooperate to deliver the most efficient, safe, secure and comfortable journey. The vehicle-vehicle and vehicle-infrastructure co-operative systems will contribute to these objectives beyond the improvements achievable with stand-alone systems.” 3rd eSafety Forum, 25 March 2004

Examples for Co-Operative Systems: COOPERS - Co-operative Systems for Intelligent Road Safety

T raffic Estimation and Prediction System

Traffic estimation and prediction system (TrEPS) have the potential to improve traffic conditions and reduce travel delays by facilitating better utilization of available capacity. These systems exploit currently available and emerging computer, communication, and control technologies to monitor, manage, and control the transportation system. They also provide various levels of traffic information and trip advisory to system users, including many ITS service providers, so that travelers can make timely and informed travel decisions.

OBJECTIVE OF THE PROJECT

Investigation and design of wireless, both vehicle-to-

vehicle (V2V) communication and vehicle-to-roadside

(V2R) communication system architecture which is

fault tolerant and robust

Development of an energy efficient mutihop protocol

which incorporates mobility

Data aggregation algorithms (development of a

distributed and collaborative signal processing

algorithm)

Development of a system based on wireless sensors for

vehicle surveillance technology

Development of wireless collision avoidance system and

communication of this information

Develop an efficient toll collection using wireless access

from vehicles

Setup of a test bed at IIT-Bombay

Field deployable prototype

Investigations of theoretical issues related to wireless

access networks for vehicular communication

including localization, multihop routing algorithms,

distributed signal processing and clustering

Likely End User(s)

RoadTransportationAgenciesAutomobileIndustries

BRIEF OUTLINE OF THE PROJECT

The project envisages investigating and exploiting different forms of wireless communication technologies, like IEEE 802.11p (DSRC – Dedicated Short Range Communication), IEEE 802.16j and the existing Wi-Fi, Wi-Max in intra and

inter vehicular communication system. The work proposal will include investigation and development of systems for both vehicle-to-vehicle (V2V) communication and vehicle-to-roadside (V2R) communication. This will indeed involve multi-hop communication. We will exploit latest developments in wireless communication, including wireless sensor networks, 802.11p, 802.11j, and signal processing to achieve the broad objectives of intra and inter vehicular communication system: Succinctly, enhancement of vehicle handling capacity, road travel safety and communication and information management system. We also plan to investigate a system based on wireless sensors for vehicle surveillance technology because of its low cost and potential for large scale deployment. As a by product, we will also look at efficient toll collection using wireless access from vehicles. We also propose to explore development of an early warning system for vehicle collision avoidance using wireless sensor networks.

We will explore theoretical issues related to design of wireless access networks for vehicular communication: for example issues like localization of vehicles, efficient multihop routing protocol, collaborative signal processing and clustering algorithms. Our focus will be on system development as well as associated theoretical issues.

There are several challenging research issues related to V2R and V2V communication systems. Some of the issues we plan to look at are: Radio links between V2V and also between V2R are very short but there is still presence of multipath reflections and interference from other links using the same frequency channel. Radio propagation modeling has been shown to importantly affect the performance of traditional mobile and wireless communication systems. We propose to investigate different PHY layer models in a vehicular network, by analyzing the contributions of path loss, shadowing and fast fading effects. Different multiple access schemes such as TDMA, DS-CDMA,

FH-TDMA, OFDMA and MC-CDMA will be investigated. We will also look into security issues related to vehicular communication. Both V2V and V2R networks differ from ad hoc and cellular systems significantly in resource availability and mobility characteristics. Both V2V and V2R imply exchange of data between communication nodes whose location, velocity and heading are constantly being modified. Moreover, the addresses of these communication nodes are not known and the communication scenario change quickly as vehicles travel on different roads and in different areas. Therefore, adopting existing wireless networking solutions to this environment may result in low performance in delay, throughput, and fairness. We will investigate new MAC protocols and application-specific protocol optimizations. The goal would be to develop multihop communication protocols for both V2V and V2R communication while supporting high throughput, low delay, and fair access to available resources. Both, the fading and multipath nature of wireless channels and fast mobility of vehicles create challenges for satisfying the stringent emergency warning message delivery systems. The design of effective vehicular communication poses a series of technical challenges as elaborated above. We will investigate some of these and others that we encounter along the way under this proposal.

The key fall out of the project will be a field deployable wireless access network in site-specific road transportation applications. It will also lead to publications and possibly to patents and prototypes out of the applied research and system development conducted by us. It will be our endeavor that the wireless access network technology developed in this project will lead to incubating a company.

DESCRIPTION OF THE PROJECT

Currently, a variety of sensors ranging from temperature sensors to visual sensors are available onboard vehicle.

These sensors collect important data related to the vehicle, the driver, the passengers, as well as the vehicle's surrounding. For example, the millimeter wave radar can be used for detecting the distance of obstacles or other vehicles. The millimeter-wave radar is based on the FM-CW (Frequency Modulated-Continuous Wave) radar system, and can detect targets even during stormy conditions. It can simultaneously measure both the target's distance and its relative velocity. It can, hence, be used in driving conditions with poor visibility such as driving in a fog. In addition, a visual sensor or a camera can also be mounted on board for classification of sensed objects. It has been observed that cameras mounted on vehicles could assist the driver to drive the vehicle more safely. If more than one type of sensors is used in a vehicle, it is necessary and possible to combine or fuse the data sensed by each sensor to facilitate processing and communication among vehicles. In this project, we plan to investigate the formation of mobile ad hoc sensor networks for vehicular communication, in order to facilitate exchange of sensing information. Use of such network will help in achieving the basic objectives intra and inter vehicular communication system; these objectives being: (i) Enhancing vehicle handling capacity, (ii) Increasing mobility, (iii) Increasing safety, (iv) Improving the conditions of travel, (v) Reducing adverse environmental effects.

The goal of the project is to explore exploit the latest developments in wireless communication for V2V and V2R communication system. Wireless technologies will include, wireless sensor networks, DSRC (Dedicated Short Range Communication) technologies like 802.11p and 802.16j. We will exploit existing technologies like WiMax (802.16e), 3G (both on their way in India) and GPRS. All these wireless technologies will be enhanced with signal processing to achieve the broad objectives of intra and inter vehicular communication system (see Figure 1). Broadly, some of the aspects

will include enhancement of vehicle handling capacity, road travel safety and communication and information management system.

Figure: Communication Technologies

IEEE 802.11p Wireless Access in the Vehicular Environment (WAVE) is a standard in the IEEE 802.11 family. It defines enhancements to 802.11 required to support intra and inter vehicular communication system applications. This includes data exchange between high-speed vehicles and between the vehicles and the roadside infrastructure in the licensed band of 5.9 GHz (5.85-5.925 GHz). It is envisaged that IEEE 802.11p will be used as the groundwork for Dedicated Short Range Communications (DSRC). In the case of the V2V and V2R, the DSRC– type systems will be investigated for the purpose of high speed data transmission simultaneously, considering the radio propagation characteristics of the radio wave along the road. Furthermore, the DSRC-V2V system will be investigated for a wireless communication system between the vehicles. The DSRC-V2V system will make an ad-hoc network in which the vehicle control data is transmitted between it and the other neighborhood car. Thereby,

the vehicles operate in a group cooperative driving which are changing from moment to moment. The ultimate vision is development of a network that enables communications between vehicles and roadside access points or other vehicles. The basic architecture for our investigations is illustrated in Figures 2 and 3.

Figure: V2V Ad-Hoc Approach

Figure: Typical Architecture of an Intelligent Car and Mobility System

We also plan to explore a system, based on wireless sensor network for vehicle surveillance technology because of its low cost and potential for large scale deployment. The idea is to sense vehicles position (could be using GPS), speed and direction, number of vehicles nearby (level of congestion) and other parameters, and transmit the same to a central control system which in turn will transmit to drivers, the vehicular traffic information and safety and alert messages. As a by product, we will also look at efficient toll collection using wireless access from vehicles.

We also propose to explore development of an early warning system for vehicle collision avoidance using wireless sensor networks. Each year around the world, motor vehicle crashes account for human losses and financial losses in the order of millions. The pursuit of advanced vehicle collision warning system is one of many efforts by auto

manufacturers and traffic safety administration to reduce the crash rate. The introduction of collision warning systems could

dramatically reduce crash fatalities, injuries and property damage. The wireless sensors in the vehicle will gather information about the position of the vehicle using GPS receiver and other vital information, like speed, acceleration, etc. The system will use this information to cooperatively assess the possibility of a collision with other vehicles in the vicinity, using DSRC. Depending on the criticality of the situation, the driver would be given different levels of warning. Collision Warning Systems share a common need: the vehicle needs to know about the locations and motions of all the neighboring vehicles, representing the state of the vehicle neighborhood. Most collision warning systems in the literature try to learn the state of the neighboring vehicles or roadway by using sensors like radar, laser, or vision looking forward, to the rear, to the right lane and left lane, or predict a collision cooperatively with the neighboring vehicles. The proposed scheme is based on V2V communication using ad hoc wireless sensor networks. Threat detections are achieved by vehicles cooperatively sharing critical information for collision anticipation, i.e., location, velocity, acceleration, etc. By sharing the information between peers, each vehicle is able to predict potential hazards. Although this system does not require a support infrastructure, the ultimate value of this kind of peer-to-peer cooperative system depends on the percentage of vehicles on the road using it. The more vehicles using it, the more valuable it is. A proposed system is depicted in Figure. As can be seen the warning system will work even if the potentially colliding vehicles are out of sight.

IEEE 802.11: SET OF STANDARDS FOR WIRELESS LOCAL AREA NETWORK

IEEE 802.11 is a set of standards for wireless local area network (WLAN) computer communication, developed by the IEEE LAN/MAN Standards Committee (IEEE 802) in the 5 GHz and 2.4 GHz public spectrum bands.

Although the terms 802.11 and Wi-Fi are often used interchangeably, the Wi-Fi Alliance uses the term "Wi-Fi" to define a slightly different set of overlapping standards. In some cases, market demand has led the Wi-Fi Alliance to begin certifying products before amendments to the 802.11 standard are complete.

The 802.11 family includes over-the-air modulation techniques that use the same basic protocol. The most popular are those defined by the 802.11b and 802.11g protocols, and are amendments to the original standard. 802.11a was the first wireless networking standard, but 802.11b was the first widely accepted one, followed by 802.11g and 802.11n. Security was originally purposefully weak due to export requirements of some governments, and was later enhanced via the 802.11i amendment after governmental and legislative changes. 802.11n is a new multi-streaming modulation technique that is still under draft development, but products based on its proprietary pre-draft versions are being sold. Other standards in the family (c–f, h, j) are service amendments and extensions or corrections to previous specifications.

802.11b and 802.11g use the 2.4 GHz ISM band, operating in the United States under Part 15 of the US Federal Communications Commission Rules and Regulations. Because of this choice of frequency band, 802.11b and g equipment may occasionally suffer interference from microwave ovens and cordless telephones. Bluetooth

devices, while operating in the same band, in theory do not interfere with 802.11b/g because they use a frequency hopping spread spectrum signaling method (FHSS) while 802.11b/g uses a direct sequence spread spectrum signaling method (DSSS). 802.11a uses the

5 GHz U-NII band, which offers 8 non-overlapping channels rather than the 3 offered in the 2.4GHz ISM frequency band.The segment of the radio frequency spectrum used varies between countries. In the US, 802.11a and 802.11g devices may be operated without a license, as explained in Part 15 of the FCC Rules and Regulations. Frequencies used by channels one through six (802.11b) fall within the 2.4 GHz amateur radio band. Licensed amateur radio operators may operate 802.11b/g devices under Part 97 of the FCC Rules and Regulations, allowing increased power output but not commercial content or encryption.

PROTOCOLS: SUMMARY

Protocol

Release

Date

Op. Freque

ncy

Throughput

(Typ)

Data Rate (Max)

Modulation

Technique

Range (Radi

us Indoo

r)

Depends, # and type of

walls

Range (Radi

us Outdo

or)

Loss includes one wall

Legacy

1997 2.4 GHz0.9

Mbit/s

2 Mbit/s

~20 Meters

~100 Meter

s

802.11a

1999 5 GHz 23 Mbit/s54 Mbit/s

OFDM~35

Meters

~120 Meter

s

802.11b

1999 2.4 GHz4.3

Mbit/s

11 Mbit/s

DSSS~38

Meters

~140 Meter

s

802.11g

2003 2.4 GHz 19 Mbit/s54 Mbit/s

OFDM~38

Meters

~140 Meter

s

802.11n

June 2009

[4]

(est.)

2.4 GHz5 GHz

74 Mbit/s

248

Mbit/s

~70 Meters

~250 Meter

s

80

June 2008

3.7 GHz 23 Mbit/s 54 Mb

~50 Meters

~5000 Meter

2.11y

[4]

(est.)it/s s

PROTOCOLS: DESCRIPTION

802.11-1997 (802.11 legacy)

The original version of the standard IEEE 802.11, released in 1997 and clarified in 1999, specified two raw data rates of 1 and 2 mega bits per second (Mbit/s) to be transmitted in Industrial Scientific Medical frequency band at 2.4 GHz.

Legacy 802.11 was rapidly supplemented (and popularized) by 802.11b.

802.11a

Release Date

Op. Frequenc

y

Data Rate (Typ)

Data Rate (Max)

Range (Indoor)

October 1999

5 GHz 23 Mbit/s 54 Mbit/s ~35 m

The 802.11a standard uses the same core protocol as the original standard, operates in 5 GHz band with a maximum raw data rate of 54 Mbit/s, which yields realistic net achievable throughput in the mid-20 Mbit/s.

Since the 2.4 GHz band is heavily used to the point of being crowded, using the relatively un-used 5 GHz band gives 802.11a a significant advantage. However, this high carrier frequency also brings a slight disadvantage: The effective overall range of 802.11a is slightly less than that of 802.11b/g; 802.11a signals cannot penetrate as far as those for 802.11b because they are absorbed more readily by walls and other solid objects in their path.

802.11b

Release Date

Op. Frequenc

y

Data Rate (Typ)

Data Rate (Max)

Range (Indoor)

October 1999

2.4 GHz 4.5 Mbit/s 11 Mbit/s ~35 m

802.11b has a maximum raw data rate of 11 Mbit/s and uses the same media access method defined in the original standard. 802.11b products appeared on the market in early 2000, since 802.11b is a direct extension of the modulation technique defined in the original standard. The dramatic increase in throughput of 802.11b (compared to the original standard) along with simultaneous substantial price reductions led to the rapid acceptance of 802.11b as the definitive wireless LAN technology.

802.11b devices suffer interference from other products operating in the 2.4 GHz band. Devices operating in the 2.4 GHz range include: microwave ovens, Bluetooth devices, baby monitors and cordless telephones. Interference issues, and user density problems within the 2.4 GHz band have become a major concern and frustration for users.

802.11g

Release Date

Op. Frequenc

y

Data Rate (Typ)

Data Rate (Max)

Range (Indoor)

June 2003

2.4 GHz 19 Mbit/s 54 Mbit/s ~35 m

In June 2003, a third modulation standard was ratified: 802.11g. This works in the 2.4 GHz band (like 802.11b) but operates at a maximum raw data rate of 54 Mbit/s, or about 19 Mbit/s net throughput.

802.11g hardware is fully backwards compatible with 802.11b hardware.

The then-proposed 802.11g standard was rapidly adopted by consumers starting in January 2003, well before ratification, due to the desire for higher speeds, and reductions in manufacturing costs. By summer 2003, most dual-band 802.11a/b products became dual-band/tri-mode, supporting a and b/g in a single mobile adapter card or access point. Details of making b and g work well together occupied much of the lingering technical process; in an 802.11g network, however, activity by a legacy 802.11b participant will reduce the speed of the overall 802.11g network.

802.11g devices suffer interference from other products operating in the 2.4 GHz band. Devices operating in the 2.4 GHz range include: microwave ovens, Bluetooth devices,

baby monitors and cordless telephones.

802.11-2007

In 2003, task group TGma was authorized to "roll up" many of the amendments to the 1999 version of the 802.11 standard. REVma or 802.11ma, as it was called, created a single document that merged 8 amendments (802.11a,b,d,e,g,h,i,j) with the base standard. Upon approval on March 08, 2007, 802.11REVma was renamed to the current# # # # standard IEEE 802.11-2007. This is the single most modern 802.11 document available that contains cumulative changes from multiple sub-letter task groups.

802.11n

Release Date

Op. Frequency

Data Rate (Typ)

Data Rate (Max)

Range (Indoor)

June 2009 (est.)

5 GHz and/or 2.4

GHz

74 Mbit/s

248 Mbit/s (2 streams) ~70 m

802.11n is a proposed amendment which improves upon the previous 802.11 standards by adding multiple-input multiple-output (MIMO) and many other newer features.

Though there are already many products on the market based on Draft 2.0 of this proposal, the TGn workgroup is not expected to finalize the amendment until November 2008.

Channels And International Compatibility

The channels that are available for use in a particular country differ according to the regulations of that country. In the United States and Canada, for example, regulations for the 2.4 GHz only allow channels 1 through 11 are allowed to be used. In most European Union countries channels 1–13 are licensed for 802.11 operation. In Japan, only channel 14 is licensed for 802.11 2.4 GHz operation. For more details on this topic, see List of WLAN channels.

802.11b and 802.11g – as well as 802.11n when using the 2.4 GHz band – divide the 2.4 GHz spectrum into 14 overlapping, staggered channels whose center frequencies are mostly 5 megahertz (MHz) apart. The Clause 17 of the 802.11 standard specifies the center frequency of the channel and a spectral mask width to a power level for that channel. The spectral mask requires that the signal be attenuated by at least 30 dB from its peak energy at ± 11 MHz from the center frequency. This means that an 802.11b/g product occupies

five channels to an energy level of 30 dB down from the peak or center of the signal. For the United States, the valid channels are one through eleven: this limits the number of non-overlapped channels to three usually 1, 6 and 11. Most European Union country allow for channels 1-13 allowing for four non-overlapping channels at 1, 5, 9 and 13.

Since the spectral mask only defines power output

restrictions up to ± 22 MHz from the center frequency to be attenuated by 50 dB, it is often assumed that the energy of the channel extends no further than these limits. It is more correct to say that, given the separation between channels 1, 6, and 11, the signal on any channel should be sufficiently attenuated to minimally interfere with a transmitter on any other channel. Due to the near-far problem a transmitter can impact a receiver on a "non-overlapping" channel, but only if it is close to the victim receiver (within a meter) or operating above allowed power levels.

Although the statement that channels 1, 6, and 11 are "non-overlapping" is limited to a spacing or product density, the 1–6–11 guideline has merit. If transmitters are closer together than channels 1, 6, and 11 (for example, 1, 4, 7, and 10), overlap between the channels may cause unacceptable degradation of signal quality and throughput.

IEEE 802.11p (DEDICATED SHORT RANGE COMMUNICATION)

IEEE 802.11p is a draft amendment to the IEEE 802.11 standard to add wireless access in the vehicular environment (WAVE). It defines enhancements to 802.11 required to support Intelligent Transportation Systems (ITS) applications. This includes data exchange between high-speed vehicles and between the vehicles and the roadside infrastructure in the licensed ITS band of 5.9 GHz (5.85-5.925 GHz). IEEE 1609 is a higher layer standard on which IEEE 802.11p is based. 802.11p will be used as the groundwork for Dedicated Short Range Communications (DSRC), a U.S. Department of Transportation project based on European system CALM looking at vehicle-based communication networks, particularly for applications such as toll collection, vehicle safety services, and commerce transactions via cars. The ultimate vision is a nationwide network that enables

communications between vehicles and roadside access points or other vehicles. This work builds on its predecessor ASTM E2213-03.

Dedicated Short Range Communications (DSRC)

It is a short to medium range wireless protocol specifically designed for automotive use. It offers communication between the vehicle and roadside equipment. It is a sub-set of the RFID-technology. This technology for ITS applications is working in the 5.9 GHz band (U.S.) or 5.8 GHz band (Japan, Europe). Former standard used the 915 MHz band.Currently its main use In Europe and Japan is in Electronic toll collection. DSRC systems in Europe, Japan and U.S. are not, at the present moment compatible.

Other possible applications are:Emergency warning system for vehicles Cooperative Adaptive Cruise Control Cooperative Forward Collision Warning Intersection collision avoidance Approaching emergency vehicle warning (Blue Waves) Vehicle safety inspection Transit or emergency vehicle signal priority Electronic parking payments Commercial vehicle clearance and safety inspections In-vehicle signing Rollover warning Probe data collection Highway-rail intersection warning

Other short-range wireless communication technologies are IEEE 802.11j, IEEE 802.16j, Wi-Fi, Wi-Max, Bluetooth and CALM.

IEEE 802.11j-2004 Or 802.11jIt is an amendment to the IEEE 802.11 standard designed specially for Japanese market. It allows Wireless LAN operation in the 4.9 to 5 GHz band to conform to the Japanese rules for radio operation for indoor, outdoor and mobile applications. The amendment has been incorporated into the published IEEE 802.11-2007 standard.802.11 is a set of IEEE standards that govern wireless networking transmission methods. They are commonly used today in their 802.11a, 802.11b, and 802.11g versions to provide wireless connectivity in the home, office and some commercial establishments.

IEEE 802.16jThe IEEE 802.16 Working Group on Broadband Wireless Access Standards, which was established by IEEE Standards Board in 1999, aims to prepare formal specifications for the global deployment of broadband Wireless Metropolitan Area Networks. The Workgroup is a unit of the IEEE 802 LAN/MAN Standards Committee. A related future technology Mobile Broadband Wireless Access (MBWA) is under development in IEEE 802.20.Although the 802.16 family of standards is officially called WirelessMAN, it has been dubbed “WiMAX” (from "Worldwide Interoperability for Microwave Access") by an industry group called the WiMAX Forum. The mission of the Forum is to promote and certify compatibility and interoperability of broadband wireless products.

802.16 Standards

The first 802.16 standard was approved in December 2001. It delivered a standard for point to multipoint Broadband Wireless transmission in the 10-66 GHz band, with only a line-of-sight (LOS) capability. It uses a single carrier (SC) physical (PHY) standard.802.16a was an amendment to 802.16 and delivered a point

to multipoint capability in the 2-11 GHz band. For this to be of use, it also required a non line-of-sight (NLOS) capability, and the PHY standard was therefore extended to include Orthogonal Frequency Division Multiplex (OFDM) and Orthogonal Frequency Division Multiple Access (OFDMA). 802.16a was ratified in January 2003 and was intended to provide "last mile" fixed broadband access.802.16c, a further amendment to 802.16, delivered a system profile for the 10-66 GHz 802.16 standard.

In September 2003, a revision project called 802.16d commenced aiming to align the standard with aspects of the European Telecommunications Standards Institute (ETSI) HIPERMAN standard as well as lay down conformance and test specifications. This project concluded in 2004 with the release of 802.16-2004 which superseded the earlier 802.16 documents, including the a/b/c amendments.An amendment to 802.16-2004, IEEE 802.16e-2005 (formerly known as IEEE 802.16e), addressing mobility, was concluded in 2005. This implemented a number of enhancements to 802.16-2004, including better support for Quality of Service and the use of Scalable OFDMA, and is sometimes called “Mobile WiMAX”, after the WIMAX forum for interoperability.Amendments in Progress

Active amendments:802.16e-2005 — Mobile 802.16 802.16f-2005 — Management Information Base 802.16g-2007 — Management Plane Procedures and

Services 802.16k-2007 — Bridging of 802.16 (an amendment to

802.1D) Amendments under development:

802.16h — Improved Coexistence Mechanisms for License-Exempt Operation

802.16i — Mobile Management Information Base 802.16j — Multihop Relay Specification 802.16Rev2 — Consolidate 802.16-2004, 802.16e,

802.16f, 802.16g and possibly 802.16i into a new document.

Amendments at pre-draft stage:802.16m — Advanced Air Interface. Data rates of 100

Mbit/s for mobile applications and 1 Gbit/s for fixed applications, cellular, macro and micro cell coverage, with currently no restrictions on

the RF bandwidth (which is expected to be 20 MHz or higher).[1] The proposed work plan would allow completion of the standard by Sept 2008 for approval by Dec 2008.

802.16e-2005 Technology

The 802.16 standard essentially standardizes 2 aspects of the air interface - the physical layer (PHY) and the Media Access Control layer (MAC). This section provides an overview of the technology employed in these 2 layers in the current version of the 802.16 specification (which is strictly 802.16-2004 as amended by 802.16e-2005, but which will be referred to as 802.16e for brevity).

PHY802.16e uses Scalable OFDMA to carry data, supporting channel bandwidths of between 1.25 MHz and 20 MHz, with up to 2048 sub-carriers. It supports adaptive modulation and coding, so that in conditions of good signal, a highly efficient 64 QAM coding scheme is used, whereas where the signal is poorer, a more robust BPSK coding mechanism is used. In intermediate conditions, 16 QAM and QPSK can also be employed. Other PHY features include support for Multiple-in Multiple-out (MIMO) antennas in order to provide good NLOS (Non-line-of-sight) characteristics (or higher bandwidth) and Hybrid automatic repeat request (HARQ) for good error correction performance.MACThe 802.16 MAC describes a number of Convergence Sublayers which describe how wireline technologies such as Ethernet, ATM and IP are encapsulated on the air interface, and how data is classified, etc. It also describes how secure

communications are delivered, by using secure key exchange during authentication, and encryption using AES or DES (as the encryption mechanism) during data transfer. Further features of the MAC layer include power saving mechanisms (using Sleep Mode and Idle Mode) and handover mechanisms.

A key feature of 802.16 is that it is a connection oriented technology. The subscriber station (SS) cannot transmit data until it has been allocated a channel by the Base Station (BS). This allows 802.16e to provide strong support for Quality of Service (QoS).QoSQoS in 802.16e is supported by allocating each connection between the SS and the BS (called a service flow in 802.16 terminology) to a specific QoS class. In 802.16e, there are 5 QoS classes:

Service Abbrev

Definition Typical Applications

Unsolicited Grant Service

UGS Real-time data streams comprising fixed-size data packets issued at

periodic intervals

T1/E1 transport

Extended Real-time

Polling Service

ertPS

Real-time service flows that generate variable-sized data packets on a

periodic basis

VoIP

Real-time Polling Service

rtPS Real-time data streams comprising variable-

sized data packets that are issued at periodic

intervals

MPEG Video

Non-real-time

Polling Service

nrtPS

Delay-tolerant data streams comprising variable-sized data packets for which

minimum data rate is required

FTP with guaranteed minimum

throughput

Best Effort BE Data streams for which HTTP

no minimum service level is required and

therefore may be handled on a space-

available basis

The BS and the SS use a service flow with an appropriate QoS class (plus other parameters, such as bandwidth and delay) to ensure that application data receives QoS treatment appropriate to the application.

Wi-Fi

Wi-Fi is a wireless technology brand owned by the Wi-Fi Alliance intended to improve the interoperability of wireless local area network products based on the IEEE 802.11 standards. Common applications for Wi-Fi include Internet and VoIP phone access, gaming, and network connectivity for consumer electronics such as televisions, DVD players, and digital cameras.The Wi-Fi Alliance is a consortium of separate and independent companies agreeing to a set of common interoperable products based on the family of IEEE 802.11 standards. The Wi-Fi Alliance certifies products via a set of established test procedures to establish interoperability. Those manufacturers that are members of Wi-Fi Alliance whose products pass these interoperability tests can mark their products and product packaging with the Wi-Fi logo. Wi-Fi technologies have gone through several generations since their inception in 1997. Wi-Fi is supported to different extents under Microsoft Windows, Apple Mac OS X and open source Unix and Linux operating systems.

Uses

A Wi-Fi enabled device such as a PC, game console, cell phone, MP3 player or PDA can connect to the Internet when within range of a wireless network connected to the Internet. The area covered by one or more interconnected access points is called a hotspot. Hotspots can cover as little as a single room with wireless-opaque walls or as much as many square miles covered by overlapping access points. Wi-Fi has been used to create mesh networks, for example, in the City of London. Both architectures are used in community networks. Wi-Fi also allows connectivity in peer-to-peer (wireless ad-hoc network) mode, which enables devices to connect directly with each

other. This connectivity mode is useful in consumer electronics and gaming applications.When the technology was first commercialized there were many problems because consumers could not be sure that products from different vendors would work together. The Wi-Fi Alliance began as a community to solve this issue so as to address the needs of the end user and allow the technology to mature. The Alliance created the branding Wi-Fi CERTIFIED to show consumers that products are interoperable with other products displaying the same branding.Many consumer devices use Wi-Fi. Amongst others, personal computers can network to each other and connect to the Internet, mobile computers can connect to the Internet from any Wi-Fi hotspot, and digital cameras can transfer images wirelessly.Routers which incorporate a DSL or cable modem and a Wi-Fi access point are often used in homes and other premises, and provide Internet access and internetworking to all devices connected wirelessly or by cable into them. Devices supporting Wi-Fi can also be connected in ad-hoc mode for client-to-client connections without a router.Business and industrial Wi-Fi is widespread as of 2007. In business environments, increasing the number of Wi-Fi

access points provides redundancy, support for fast roaming and increased overall network capacity by using more channels or creating smaller cells. Wi-Fi enables wireless voice applications (VoWLAN or WVOIP). Over the years, Wi-Fi implementations have moved toward 'thin' access points, with more of the network intelligence housed in a centralized network appliance, relegating individual Access Points to be simply 'dumb' radios. Outdoor applications may utilize true mesh topologies. As of 2007 Wi-Fi installations can provide a secure computer networking gateway, firewall, DHCP server, intrusion detection system, and other functions.In addition to restricted use in homes and offices, Wi-Fi is publicly available at Wi-Fi hotspots provided either free of charge or to subscribers to various providers. Free hotspots are often provided by

businesses such as hotels, restaurants, and airports who offer the service to attract or assist clients. Sometimes free Wi-Fi is provided by enthusiasts, or by organizations or authorities who wish to promote business in their area. Metropolitan-wide WiFi (Mu-Fi) already has more than 300 projects in process. Advantages of Wi-Fi

Wi-Fi allows LANs to be deployed without cabling for client devices, typically reducing the costs of network deployment and expansion. Spaces where cables cannot be run, such as outdoor areas and historical buildings, can host wireless LANs.As of 2007 wireless network adapters are built into most modern laptops. The price of chipsets for Wi-Fi continues to drop, making it an economical networking option included in ever more devices. Wi-Fi has become widespread in corporate infrastructures, which also helps with the deployment of RFID technology that can piggyback on Wi-Fi. Different competitive brands of access points and client network interfaces are inter-operable at a basic level of service. Products designated as "Wi-Fi Certified" by the Wi-

Fi Alliance are backwards inter-operable. Wi-Fi is a global set of standards. Unlike mobile telephones, any standard Wi-Fi device will work anywhere in the world.Wi-Fi is widely available in more than 250,000[citation needed] public hotspots and tens of millions of homes and corporate and university campuses worldwide. WPA is not easily cracked if strong passwords are used and WPA2 encryption has no known weaknesses. New protocols for Quality of Service (WMM) make Wi-Fi more suitable for latency-sensitive applications (such as voice and video), and power saving mechanisms (WMM Power Save) improve battery operation.

Disadvantages of Wi-Fi

Spectrum assignments and operational limitations are not consistent worldwide. Most of Europe allows for an additional 2 channels beyond those permitted in the U.S for the 2.4 GHz band. (1-13 vs. 1-11); Japan has one more on top of that (1-14). Europe, as of 2007, is now essentially homogeneous in this respect. A very confusing aspect is the fact a Wi-Fi signal actually occupies five channels in the 2.4 GHz resulting in only 3 non-overlapped channels in the US: 1, 6, 11, and four in Europe: 1,5,9,13Some countries, such as Italy, formerly required a 'general authorization' for any Wi-Fi used outside an operator's own premises, or require something akin to an operator registration.[citation needed] Equivalent isotropically radiated power (EIRP) in the EU is limited to 20 dBm (0.1 W).Power consumption is fairly high compared to some other low-bandwidth standards, such as Zigbee and Bluetooth, making battery life a concern.The most common wireless encryption standard, Wired Equivalent Privacy or WEP, has been shown to be easily breakable even when correctly configured. Wi-Fi Protected Access (WPA and WPA2), which began shipping in 2003, aims to solve this problem and is now available on most products. Wi-Fi Access Points typically default to an "open"

(encryption-free) mode. Novice users benefit from a zero-configuration device that works out of the box, but this default is without any wireless security enabled, providing open wireless access to their LAN. To turn security on requires the user to configure the device, usually via a software graphical user interface (GUI). Wi-Fi networks that are open (unencrypted) can be monitored and used to read and copy data (including personal information) transmitted over the network, unless another security method is used to secure the data, such as a VPN or a secure web page. (See HTTPS/Secure Socket Layer.)Many 2.4 GHz 802.11b and 802.11g Access points default to the same channel on initial startup, contributing to congestion on certain

channels. To change the channel of operation for an access point requires the user to configure the device.Wi-Fi networks have limited range. A typical Wi-Fi home router using 802.11b or 802.11g with a stock antenna might have a range of 32 m (120 ft) indoors and 95 m (300 ft) outdoors. Range also varies with frequency band. Wi-Fi in the 2.4 GHz frequency block has slightly better range than Wi-Fi in the 5 GHz frequency block. Outdoor range with improved (directional) antennas can be several kilometres or more with line-of-sight.Wi-Fi performance also decreases exponentially as the range increases.Wi-Fi pollution, or an excessive number of access points in the area, especially on the same or neighboring channel, can prevent access and interfere with the use of other access points by others, caused by overlapping channels in the 802.11g/b spectrum, as well as with decreased signal-to-noise ratio (SNR) between access points. This can be a problem in high-density areas, such as large apartment complexes or office buildings with many Wi-Fi access points. Additionally, other devices use the 2.4 GHz band: microwave ovens, security cameras, Bluetooth devices and (in some countries) Amateur radio, videosenders, cordless phones and baby monitors can cause significant additional

interference. General guidance to those who suffer these forms of interference or network crowding is to migrate to a WiFi 5 GHz product, (802.11a or the newer 802.11n IF it has 5GHz/11a support) as the 5 GHz band is relatively unused and there are many more channels available. This also requires users to set up the 5 GHz band to be the preferred network in the client and to configure each network band to a different name(SSID).It is also an issue when municipalities, or other large entities such as universities, seek to provide large area coverage. This openness is also important to the success and widespread use of 2.4 GHz Wi-Fi.Interoperability issues between non WiFi brands or proprietary deviations from the standard can disrupt connections or lower

throughput speeds on all user's devices that are within range, to include the non-WiFi or proprietary product.Standard Devices

Wireless access points connects a group of wireless devices to an adjacent wired LAN. An access point is similar to a network hub, relaying data between connected wireless devices in addition to a (usually) single connected wired device, most often an ethernet hub or switch, allowing wireless devices to communicate with other wired devices.Wireless adapters allow devices to connect to a wireless network. These adapters connect to devices using various external or internal interconnects such as PCI, miniPCI, USB, ExpressCard, Cardbus and PC card. Most newer laptop computers are equipped with internal adapters. Internal cards are generally more difficult to install.Wireless routers integrate a WAP, ethernet switch, and internal Router firmware application that provides IP Routing, NAT, and DNS forwarding through an integrated WAN interface. A wireless router allows wired and wireless ethernet LAN devices to connect to a (usually) single WAN device such as cable modem or DSL modem. A wireless router allows all three devices (mainly the access point and router) to be configured through one central utility. This

utility is most usually an integrated web server which serves web pages to wired and wireless LAN clients and often optionally to WAN clients. This utility may also be an application that is run on a desktop computer such as Apple's AirPort.Wireless network bridges connect a wired network to a wireless network. This is different from an access point in the sense that an access point connects wireless devices to a wired network at the data-link layer. Two wireless bridges may be used to connect two wired networks over a wireless link, useful in situations where a wired connection may be unavailable, such as between two separate homes.

Wireless range extenders or wireless repeaters can extend the range of an existing wireless network. Range extenders can be strategically placed to elongate a signal area or allow for the signal area to reach around barriers such as those created in L-shaped corridors. Wireless devices connected through repeaters will suffer from an increased latency for each hop. Additionally, a wireless device connected to any of the repeaters in the chain throughput that is limited by the weakest link between the two nodes in the chain from which the connection originates to where the connection ends.Aerials and Connectors

Most commercial devices (routers, access points, bridges, repeaters) designed for home or business environments use either RP-SMA or RP-TNC antenna connectors. PCI wireless adapters also mainly use RP-SMA connectors. Most PC card and USB wireless only have internal antennas etched on their printed circuit board while some have MMCX connector or MC-Card external connections in addition to an internal antenna. A few USB cards have a RP-SMA connector. Most Mini PCI wireless cards utilize Hirose U.FL connectors, but cards found in various wireless appliances contain all of the connectors listed. Many high-gain (and homebuilt antennas) utilize the Type N connector more commonly used by other radio communications methods.

Embedded Systems

Figure: Embedded serial to WiFi module

Wi-Fi availability in the home is on the increase. This extension of the Internet into the home space will increasingly be used for remote monitoring. Examples of remote monitoring include security systems and tele-medicine. In all these kinds of implementation, if the Wi-Fi provision is provided using a system running one of operating systems mentioned above, then it becomes unfeasible due to weight, power consumption and cost issues.Increasingly in the last few years (particularly as of early 2007), embedded Wi-Fi modules have become available which come with a real-time operating system and provide a simple means of wireless enabling any device which has and communicates via a serial port.This allows simple monitoring devices – for example, a portable ECG monitor hooked up to a patient in their home – to be created. This Wi-Fi enabled device effectively becomes part of the internet cloud and can communicate with any other node on the internet. The data collected can hop via the home's Wi-Fi access point to anywhere on the internet.These Wi-Fi modules are designed so that minimal Wi-Fi knowledge is required by designers to wireless enable their product.

Wi-MAXWiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. It is based on the IEEE 802.16 standard, which is also called WirelessMAN. The name WiMAX was created by the WiMAX Forum, which was formed in June 2001 to promote conformance and interoperability of the standard. The forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL."

Definitions of Terms

802.16dStrictly speaking, 802.16d has never existed as a standard. The standard is correctly called 802.16-2004 and was developed by the IEEE 802.16 Task Group d. Therefore the project was called 802.16d, but the standard never was. However, since this standard is frequently called 802.16d, that term is also used in this article to assist readability.802.16eJust as 802.16d has never existed as a standard, neither has 802.16e. 802.16e is an amendment to 802.16-2004, and the amendment is properly referred to as 802.16e-2005. 802.16e-2005 is not a standard in its own right - since it is only an amendment, the original document (802.16-2004) has to be read and then the amendments added to it.Fixed WiMAXThis is a phrase frequently used to refer to systems built using 802.16-2004 ('802.16d') and the OFDM PHY as the air interface technology.

Fixed WiMAX deployments do not cater for handoff between Base Stations, therefore the service provider cannot offer mobility.Mobile WiMAX

A phrase frequently used to refer to systems built using 802.16e-2005 and the OFDMA PHY as the air interface technology. "Mobile WiMAX" implementations can be used to deliver both fixed and mobile services.

Broadband Access of Wi-Max

Many companies are closely examining WiMAX for "last mile" connectivity at high data rates. The resulting competition may bring lower pricing for both home and business customers or bring broadband access to places where it has been economically unavailable. Prior to WiMAX, many operators have been using proprietary fixed wireless technologies for broadband services.WiMAX access was used to assist with communications in Aceh, Indonesia, after the tsunami in December 2004. All communication infrastructure in the area, other than Ham Radio, was destroyed, making the survivors unable to communicate with people outside the disaster area and vice versa. WiMAX provided broadband access that helped regenerate communication to and from Aceh.WiMAX was used by Intel to assist the FCC and FEMA in their communications efforts in the areas affected by Hurricane Katrina.

BLUETOOTH

Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth provides a way to connect and exchange information between devices such as mobile phones, laptops, PCs, printers, digital cameras, and video game consoles over a secure, globally unlicensed short-range radio frequency. The Bluetooth specifications are developed and licensed by the Bluetooth Special Interest Group.

List Of Applications

More prevalent applications of Bluetooth include:Wireless control of and communication between a mobile

phone and a hands-free headset or car kit. This was one of the earliest applications to become popular.

Wireless networking between PCs in a confined space and where little bandwidth is required.

Wireless communications with PC input and output devices, the most common being the mouse, keyboard and printer.

Transfer of files between devices with OBEX. Transfer of contact details, calendar appointments, and

reminders between devices with OBEX. Replacement of traditional wired serial communications

in test equipment, GPS receivers, medical equipment, bar code scanners, and traffic control devices.

For controls where infrared was traditionally used. Sending small advertisements from Bluetooth enabled

advertising hoardings to other, discoverable, Bluetooth devices.

Seventh-generation game consoles—Nintendo Wii [3] , Sony PlayStation 3—use Bluetooth for their respective wireless controllers.

Dial-up internet access on personal computer or PDA using a data-capable mobile phone as a modem.

Receiving commercial advertisements ("spam") via a kiosk, e.g. at a movie theatre or lobby

Future of BluetoothBroadcast Channel: enables Bluetooth information

points. This will drive the adoption of Bluetooth into cell phones, and enable advertising models based around users pulling information from the information points, and not based around the object push model that is used in a limited way today.

Topology Management: enables the automatic

configuration of the piconet topologies especially in scatternet situations that are becoming more common today. This should all be invisible to the users of the technology, while also making the technology just work.

Alternate MAC PHY: enables the use of alternative MAC and PHY's for transporting Bluetooth profile data. The Bluetooth Radio will still be used for device discovery, initial connection and profile configuration, however when lots of data needs to be sent, the high speed alternate MAC PHY's will be used to transport the data. This means that the proven low power connection models of Bluetooth are used when the system is idle, and the low power per bit radios are used when lots of data needs to be sent.

QoS improvements: enable audio and video data to be transmitted at a higher quality, especially when best effort traffic is being transmitted in the same piconet.

Bluetooth technology already plays a part in the rising Voice over IP (VOIP) scene, with Bluetooth headsets being used as wireless extensions to the PC audio system. As VOIP becomes more popular, and more suitable for general home or office users than wired phone

lines, Bluetooth may be used in cordless handsets, with a base station connected to the Internet link.

VEHICLE-TO-VEHICLE COMMUNICATION

Traffic accidents have been taking thousands of lives each year, outnumbering any deadly diseases or natural

disasters. Studies show that about 60% roadway collisions could be avoided if the operator of the vehicle was provided warning at least one-half second prior to a collision.

Human drivers suffer from perception limitations on roadway emergency events, resulting in large delay in propagating emergency warnings, as the following simplified example illustrates. In Figure 1, three vehicles, namely A, B, and C, travel in the same lane. When A suddenly brakes abruptly, both vehicles B and C are endangered, and being further away from A does not make vehicle C any safer than B due to the following two reasons:

Line-of-sight limitation of brake light: Typically, a driver can only see the brake light from the vehicle directly in front. Thus, very likely vehicle C will not know the emergency at A until B brakes.

Large processing/forwarding delay for emergency events: Driver reaction time, i.e., from seeing the brake light of A to stepping on the brake for the driver of vehicle B, typically ranges from 0.7 seconds to 1.5 seconds [6], which results in large delay in propagating the emergency warning.

Emerging wireless communication technologies are promising to significantly reduce the delay in propagating emergency warnings.

The dedicated Short Range Communications (DSRC)

consortium is defining short to medium range communication services that support public safety in vehicle-to-vehicle (V2V) communication environment.

Using V2V communication, in our previous example, vehicle A can send warning messages once an emergency event happens. If vehicles B and C can receive these messages with little delay, the drivers can be alerted immediately. In such cases, C has a good chance of avoiding the accident via prompt reactions, and B benefits from such warnings and when visibility is poor or when the driver is not paying enough attention to the surroundings. Thus, the vehicle-to-vehicle communication enables the cooperative collision warning among vehicles A, B and C.

Figure: GM display indicates that there is a vehicle ahead on the road (depicted with the red icon) and has stopped (depicted with yellow

triangle)

Even though V2V communication may be beneficial, wireless communication is typically unreliable. Many factors, for example, channel fading, packet collisions, and communication obstacles, can prevent messages from being correctly delivered in time. In addition, ad hoc networks formed by nearly vehicles are quite different from traditional ad hoc networks due to high mobility of vehicles.

APPLICATION CHALLENGES

Using V2V communication, when a vehicle on the road acts abnormally, e.g., deceleration exceeding a certain threshold, dramatic change of moving direction, major mechanical failure, etc., it becomes an abnormal vehicle (AV). An AV actively generates Emergency Warning Messages (EWMs), which include the geographical location, speed, acceleration and moving direction of the AV, to warn other surrounding vehicles. A receiver of the warning messages can then determine the relevancy of the emergency based on the relative motion between the AV and itself.

Challenge 1: Stringent delay requirements immediately after the emergency

Over a short period immediately after an emergency event, the faster the warning is delivered to the endangered vehicles, the more likely accidents can be avoided. We define EWM delivery delay from an AV A to a vehicle V as the elapsed duration from the time the emergency occurs at A to the first corresponding EWM message is successfully received by V. Since a vehicle moving at the speed of 80miles/hour can cross more than one meter in 30 ms, the EWM delivery delay for each affected vehicle should be in order of milliseconds.

However, the link qualities in V2V communications can be very bad due to multipath fading, shadowing, and Doppler shifts caused by the high mobility of vehicles.

Moreover, in an abnormal situation, all vehicles close to the AV may be potentially endangered and they all should receive the timely emergency warning. But the group of endangered vehicles can change quickly due to high

mobility of vehicles. For example, in Figure 2, at the time of emergency event at vehicle A, the nearby vehicles N1, N2, N3, N4, and N5 are put in potential danger. Very soon, vehicles N5

and N1 may pass A and should no longer be interested in the emergency warning. Meanwhile, vehicles N6, N7 and N8 can get closer and closer to A and should be informed about the abnormal situation.

Both the unreliable nature of wireless communication and the fast changing group of affected vehicles create challenges for satisfying the stringent EWM delivery delay constraint in cooperative collision warning.

Challenge 2: Support of multiple AVs over a longer period

After an emergency event happens, the AV can stay in the abnormal state for a period of time. For example, if a vehicle stops in the middle of a highway due to mechanical

failure, it remains hazardous to any approaching vehicles, and hence, remains an abnormal vehicle until it is removed off the road.

Furthermore, emergency road situations frequently have chain effects. When a leading vehicle applies an emergency brake, it is probable that vehicles behind it will react by also decelerating suddenly.

We define co-existing AVs as all the AVs whose existences overlap in time and whose transmissions may interfere with each other. Due to the fact that an AV can exist for a relatively long period and because of the chain effect of emergency events, many co-existing AVs over a more extended period of time.

Challenge 3: Differentiation of emergency events and elimination of redundant EWMs

Emergency events from AVs following different lanes/trajectories usually have different impact on surrounding vehicles, hence, should be differentiated from each other. As the example in Figure 3 shows, vehicle A is out of control and its trajectory crosses multiple lanes. In such an abnormal situation N1 and N3 may both react with emergency braking and it is important for both N1 and N3 to give warnings to their trailing vehicles, respectively. At the same time, since the trajectory of vehicle A does not follow any given lane and it may harm vehicle N5 in near future, vehicle A needs to give its own emergency warning as well. In this particular example, three different emergency events are associated with three different moving vehicles.

On the other hand, multiple AVs may react to a same emergency event and impose similar danger to the approaching vehicles. For example, in Figure 2, vehicle A suddenly stops in the middle of the road. In reacting to the sudden stop of A, vehicle N3 brakes abruptly and stops behind A as well. For the viewpoint of vehicle A, vehicle N3 shields it from all vehicles behind. In such a case, there is no need for A to continue sending redundant EWMs some time after the emergency for several reasons: first, channel bandwidth would be consumed by unnecessary warning messages; and second, as more senders contend for a common channel, the delays of useful warning messages are likely to increase.

In real life, various reactions from drivers can happen. In the example of Figure 2, EWMs from A is redundant as long as N3 stays behind it and send EWMs. Later on, the driver of N3 may change lane and drive away. When this happens, EWMs from A becomes necessary again if A remains stopped in the middle of the road. Therefore, the design of collision warning communication protocol needs to both take advantage of traffic patterns, and be robust to

complicated road situations and driver behaviors.

VEHICULAR COLLISION WARNING COMMUNICATION PROTOCOL

A vehicle can become an abnormal vehicle (AV) due to its own mechanical failure or due to unexpected road hazards. A vehicle can also become an AV by reacting to other AVs nearby. Once an AV resumes its regular moment, the vehicle is said no longer an AV and it returns back to the normal state. In general, the abnormal behavior of a vehicle can be detected using various sensors within the vehicle. Exactly how normal and abnormal status of vehicles is detected is beyond the scope of this project. We assume that the vehicle controller can automatically monitor the vehicle dynamics and activate the collision warning communication module when it enters an abnormal state. A vehicle that receives the EWMs can verify the relevancy to the emergency event based on its relative motion to the AV, and give audio or visual warnings/advice to the driver.

Each message used in VCWC protocol is intended for a group of receivers, and the group of intended receivers changes fast due to high mobility of vehicles, which necessitate the message transmissions using broadcast instead of unicast. To ensure reliable delivery of emergency warnings over unreliable wireless channel, EWMs need to be repeatedly transmitted.

Conventionally, to achieve network stability, congestion control has been used to adjust the transmission rate based on the channel feedback. If a packet successful goes through, transmission rate is increased; while the rate is decreased if a packet gets lost.

Unlike conventional congestion control, here, there is no channel feedback available for the rate adjustment of EWMs due to the broadcast nature of EWM transmissions. Instead, we identify more application-specific properties to help EWM congestion control, which consists of the EWM transmission rate adjustment algorithm and the state transmission mechanism for AVs.

The VCWC protocol also includes emergency warning dissemination methods that make use of both natural response of human drives and

EWM message forwarding, and a message differentiation mechanism that enables cooperative vehicular collision warning application to share a common channel with other non-safety related applications. Without loss of continuity, the latter two components are largely skipped due to space limitation.

BIBLIOGRAPHY

www.wsntechnologies.com

www.wikipedia.com

www.wsn.networks.org

www.standards.ieee.org

www.xbow.com

www.maksat.com

www.intel.com

www.mit.gov.in