Study On Vehicular Ad Hoc Networks Computer Science Essay

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The electronic systems of automobiles are increasingly complex. Microcontroller or microprocessors control everything from anti-lock braking systems(ABS) and fuel injection units to rear-seat entertainment system that support advanced audio,video and wireless gaming capabilities.This report presents ad hoc networking an enabling technology relevant to a vast number of scenarios The technology is a fundamental building block for the future networking capability of the armed forces for both war and peace keeping operations.Ad hoc networking has attracted much attention in the last few years and is growing in maturity.Using mobile ad-hoc networks in an automative environment (VANET) opens a new set of applications,such as this distribution of information about local traffic or road condition.

INDEX TERMS-Wireless technologies, Configuration of networks, mobile communication, antenna based

INTRODUCTION-Driving means changing constantly location. This means a constant demand for information on the current location and specifically for data on the surrounding traffic, routes and much more. This information can be grouped together in several categories:-

A very important category is driver assistance and car safety. This includes many different things mostly based on sensor data from other cars. One could think of brake warning sent from preceding car.

Information about road condition and maintenance.

Detailed regional weather forecast, premonition of traffic jams, caution to an accident behind the next bend, detailed information about an accident for the rescue team and many other things.

One could also think of local updates of the cars navigation systems or an assistant that helps to follow a friend's car.

Another category is infotainment for passengers. For example internet access, chatting and interactive games between cars close to each other.The kids will love it .

Next category is local information as free parking space (perhaps with a reservation system), detailed information about fuel prices and services offered by the next service station or just tourist information

about sights.

A possible other category is car maintenance. For example online help

from your car mechanic when your car

breaks down or just simply service

information.

Our vehicular ad hoc networks based on wireless technologies which are illustrated below:

1- GSM (Global System For MobileCommunications)

2- GPRS or UMTS(General Packet Radio Service)

3-WLAN(Wireless Local Area Networks)

So far no inter-vehicle communication system for data exchange between vehicles and between roadside and vehicles has been put into operation.

But there are several different research projects going on.

GSM -During the period of Evolution of mobile communication technologies various systems were introduced and deployed to achieve standardization in mobile industry but all the efforts were failed. Multiple issues were sustained like incompatibility of systems, development of digital radio frequency. That is when GSM (Global System For Mobile Communication) Technology was introduced and problems like standardization, incompatibility etc were overcame. TDMA solution was chosen in 1987, It is narrowband system and TDMA standards for Time Division Multiple access[1]

GPRS-Mobile technology has gone beyond imagination of one would have thought. We have read about GSM technology which is used for voice data. GSM use technology called Circuit Switched Data (CSD) for transferring data. CSD creates special connection to the network to transfer data, it can take up to 30 seconds before this connection can put to use. After the connection is made, data started to transmit and subscriber is charged for the amount of time it remained connected to the network. Data transmission speed is relatively slow using CSD which is about 14.4 kbps for those GSM networks who are operated at 1800 frequency band, even low at 9.6 kbps when 900 MGHZ GSM network is used.

WLAN- There exist two different standards for Wireless LAN: HIPERLAN from European Telecommunications Standards Institute (ETSI) and 802.11 from Institute of Electrical and Electronics Engineers (IEEE). Nowadays the 802.11 standard totally dominates the market and the implementing

hardware is well engineered.[1]

Our term report is about ad hoc networks so we are not going in depth of these two technologies we will be focused on WLAN

1 CONFIGURATION OF NETWORKS -The IEEE 802.11 standards, specifies two different ways to configure a network:-

1-Ad hoc

2-Infrastructure

The infrastructure mode uses fixed, network access points over which mobile nodes can communicate These network access points are usually connected to landlines to widen the LAN's capability by bridging wireless nodes to other wired nodes Fig(1.0) If service areas of access points overlap, mobile nodes may be handed over between them. This structure is very similar to the present day cellular networks

Fig (1.0) Infrastructure of WLAN

AD HOC NETWORKS- In an ad hoc network, computers are brought together to form a network

"on the fly." As shown in Figure(1.1), there is no fixed structure to the network, there are no fixed points and usually every node is able to communicate with every other node in its communication range. Such networks are called Mobile Ad hoc Networks (MANET) .

Figure(1.1) WLAN of ad hoc networks

One could even think of a combination of these two networks to a hybrid network structure. Like this it would be possible to grant internet access

to a large number of mobile nodes over only a few base stations. But there is no standard for such hybrid networks yet [1].

2 PROTOCOLS IN VANET- An ad hoc routing protocol is a convention, or standard, that controls how nodes decide which way to route packets between computing devices in a mobile ad hoc network .In ad hoc networks, nodes do not start out familiar with the topology of their networks; instead, they have to discover it. The basic idea is that a new node may announce its presence and should listen for announcements broadcast by its neighbours. Each node learns about nodes nearby and how to reach them, and may announce that it, too, can reach them. In a wider sense, ad hoc protocol can also be used literally, that is, to mean an improvised and often impromptu protocol established for a specific purpose.

The following is a list of some ad hoc network routing protocols.

Geograghical Protocol

Power Aware Routing Protocol

There are many ad hoc protocols, but we are discussing only two of them because they are relevent to our topic

GEOGRAPHICAL PROTOCOL-This type of protocols acknowledges the influence of physical distances and distribution of nodes to areas as significant to network performance. The main disadvantages of such algorithms are:

Efficiency depends on balancing the geographic distribution versus occurrence of traffic.

Any dependence of performance with traffic load thwarting the negligence of distance may occur in overload

POWER AWARE PROTOCOL-Energy a>=d required to transmit a signal is approximately proportional to dα, where d is the distance and is the attenuation factor or path loss exponent, which depends on the transmission medium. When α = 2 (which is the optimal case), transmitting a signal half the distance requires one fourth of the energy and if there is a node in the middle willing to spend another fourth of its energy for the second half, data would be transmitted for half of the energy than through a direct transmission [4].The main disadvantages of the algorithm are:-

This method induces a delay for each transmission.

No relevance for energy network powered transmission operated via sufficient repeater infrastructure

3 EXAMPLES OF WIRELESS NETWORKS- Wireless Ad-hoc Networks consists of a number of sensor networks spread across a geographical area. Each sensor has wireless communication capability and some level of intelligence for signal processing and networking of the data. There are example of ad hoc wireless networks:-

Military sensor networks to detect and gain as much information as possible about enemy movements, and other phenomena of interest. In a military sensor network, track an enemy tank as it moves through the geographic area covered by the network. Also the military sensor networks designed to maintain a low probability of intercept and/or a low probability of detection. Hence the nodes prefer to radiate as little power as necessary and transmit as infrequently as possible, thus decreasing the probability of detection and interception. Sensor networks to detect and characterize Chemical, Biological, Radiological, Nuclear, and Explosive material.

4 OMNI DIRECTIONAL ANTENNAS- The antenna of a WLAN card or station is the link between the medium and the processing hardware. In most countries the maximal radiation power of an antenna is limited by regulations.But there

exist several different types of antennas for optimal use of the allowed power.Directivity is the ability of an antenna to focus energy in a particular direction when transmitting, or to receive energy better from a particular direction when receiving. This characteristic is mostly called gain and is

measured in dBi.In a static situation, it is possible to use the antenna directivity to concentrate the radiation beam in the preferred direction. However in a dynamic system as in a WLAN where the transceiver is not fixed, the antenna should radiate equally in all directions, and this is known as an

omni-directional antenna.[2]

5 MOBILE COMMUNICATION- Armed forces deployed in offensive or peace keeping missions have increasing need to communicate on the move whether between vehicles or between dismounted troops While voice communications are currently the norm, future requirements for other types of communication (telemetry, situation awareness information, video ) will drive the procurement of data communication capabilities. Ad hoc networking technology will be an essential component of such systems [2]

Fig (5.0) Armed force is in mobile communication

Mobile vehicular networks- Vehicles are required to communicate whilst on the move. In order to reach all vehicles in a convoy, or an operational deployment, the radio technology is traditionally required to have a range whilst on the move. In order to reach all vehicles in a convoy, or an operational deployment, the radio technology is traditionally required to have a range able to cover the span of the vehicle formation.Ad hoc technologies relax this constraint, by only requiring each vehicle to be in range of its closest neighbours. The appropriate neighbour will forward any data which is destined for a more distant vehicle. As the vehicles move, the connectivity between them changes as they come in and out of range of each other. The technology is able to cope with such variations and finds paths through.

A soldier can leave behind him when he moves away from his section. This provides relays which strengthen the network's connectivity if the section is spread out or operating in harsh conditions such as penetrating deep into a building.[3]

Dismounted soldier networks- For the dismounted soldier, a dynamic network short range radio is sufficient to span the entire section and provide communications beyond the individual soldier's reach. An additional feature for this scenario is the use of dedicated relays[3].

6 UNMANNED VEHICLES- Unmanned vehicles are set to play an increasing role in the future armed forces' operational missions. They can be used as individual platforms for surveillance or other purposes, but can be more profitably exploited as a networked group.

We consider a scenario in which a group of unmanned air vehicles is deployed over a battlefield Figure (6.0). Two broad categories of applications can be supported by this network. These are described below:

Networking Applications-The ad hoc network formed by the UAVs in the sky can provide a backbone for land based platforms to communicate when they are out of direct range, or when obstacles prevent direct communication. The ad hoc network therefore extends down to the land based forces and allows communication across the battlefield. Voice and video, as well as sensing and data applications can be supported.

Network Enabled Applications-The ad hoc networks also allows network enabled applications to run on the UAVs. For example, they may be able to enhance their performance by collaborating with each other over the network, for navigation, surveillance or combat purposes [3]

7 V2V COMMUNICATION-Cars are enable to communicate with each other via vehicle-to-vehicle (V2V) networks, and with infrastructure such as toll gates and traffic lights via vehicle-to-infrastructure (V2I) links. A new wireless standard called Dedicated Short Range Communication (DSRC),a sort of Wi-Fi for cars,provides high-speed data connections over distances of up to 200m, and safety and emergency communications at lower speeds over distances of up to a kilometer from one vehicle to another, and between vehicles and roadside transmitters. So far the technology is mainly used in electronic toll booths, but it has many other potential applications.

DSRC could be used, for example, to warn nearby cars of sudden breaking or an airbag deployment, thereby alerting cars out of visual range and preventing or limiting accidents. It could be used to set up ad hoc networks to pass data between cars

For example, signal icy spots on the road (many cars can detect ice as part of their skid-control systems) or groups of vehicles travelling closely together under automatic control. Other proposed uses include signalling the approach of emergency vehicles and ensuring that traffic lights give priority to buses and emergency vehicles the side mirror. If the turn signal is activated, a flashing amber light and gentle seat vibration on the side notifies the driver of a potentially dangerous situation [5]. Pile-ups on congested roads during rush hour due to a chain reaction rear-end collisions could be lessened. Using V2V, the vehicle monitors messages from other vehicles up to a quarter of a mile ahead. The trailing vehicle warns the driver first with visual icons and seat vibrations on the front and then automatically brakes if there is danger of a rear-end collision with the vehicle ahead.

8 SATELLITE NAVIGATION- The best known connected-car technology is satellite navigation, which uses the global-positioning system (GPS) in conjunction with a database of roads to provide directions and find points of interest. . In America there were fewer than 3m navigational devices on the road in 2005 nearly half of which were built in to vehicles. But built-in systems tend to be expensive, are not extensible, and may quickly be out of date. So drivers have been taking matters into their own hands of the more than 33m units on the road today, nearly 90% are portable, sitting on the dashboard or stuck to the windscreen.Many consumers are now adding internet connectivity to their cars in the form of another portable device: the "smart" phone. A two-way internet link allows for more elaborate forms of navigation, and also makes it possible to gather and aggregate information from large numbers of vehicles. Inrix, a provider of traffic data based in Seattle, has based its business model on this approach. It combines information from static sensors in the road with GPS information collected wirelessly from more than 1m fleet vehicles to provide real-time information about traffic flows. This information is piped in turn to navigation devices and smart-phones, in order to adjust a delivery route in response to an accident, for example. The company can also forecast traffic flows on a particular route at a particular time and date [5].

9 AUTONOMOUS VEHICLES-Autonomous vehicles seem to be a promising approach to both reducing traffic congestion and improving road safety. However, for such vehicles to coexist safely, they need to coordinate their behaviour to ensure that they do not collide with each other. This coordination is typically based on (wireless) communication between vehicles and needs to satisfy stringent real-time constraints.However, realtime message delivery cannot be guaranteed in dynamic wireless networks which means that existing coordination models that rely on continuous connectivity cannot be employed the coordination model builds on a real-time communication model for wireless networks that provides feedback to the entities about the state of communication.The coordination model uses this feedback to ensure that vehicles always satisfy safety constraints, by adapting their behaviour when communication is degraded. The model can be used to coordinate vehicles crossing an unsignalised junction [5].

An Example Autonomous Car-

http://superpositioned.com/files/stanley.jpg

Figure(9.0)[6] A car having navigation system ,equipped with sensors ,having cameras ,light detection and ranging system

10 PROBLEMS IN AUTONOMOUS VEHICLES-Autonomous vehicles are robotic cars that can perform desired tasks in unstructured environments without continuous human guidance. Many kinds of robotic cars have some degree of autonomy. vehicles can be autonomous in different ways. A high degree of autonomy is particularly desirable in fields such as avionics,in armed forces an under the seawater.Some modern factory robots are "autonomous" within the strict confines of their direct environment .A fully autonomous vehicle has the ability to

Gain information about the environment.

Move either all or part of itself throughout its operating environment without human assistance.

Avoid situations that are harmful to people, property, or itself unless those are part of its design specifications

The main problem that the autonomous vehicles have to face is whenever they stop moving ,a special assistance of human is needed so that he push the car and make it moveable .Researchers are working on this problem so that they can make a future autonomous car.

11 SECURITY OF VEHICULAR NETWORKS- Inter-vehicle communication among great deals of vehicles plays an important role in providing a high level of safety and convenience to drivers. Geographic routing protocol has been identified to be suited as a result of the special nature of vehicular ad hoc networks (VANETs), such as high dynamic mobility and large network size. Although there is considerable functional research about geographic routing, the security aspects have not been vastly concentrated on so far. While selecting every hop, the performance and security can be impacted severely by false position, because of the position information importance for geographic routing become a real technology that can guarantee public safety on the roads, vehicular networks need an appropriate security architecture that will protect them from different types of security attacks. Leveraging on the expertise of LCA in the domains of networking and security, we are exploring the different security aspects of vehicular networks, including

Threat model

Authentication and key management

Privacy

Secure positioning

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Figure(11.0) security of vehicular networks [6]

12 URBAN DRIVING CHALLENGE- Toyota's Researchers at several universities have built autonomous cars to complete an urban-driving challenge set Lane-Keeping Assist, for example, could easily do much of the driving on long stretches of highway, but the firm requires drivers keep their hands on the wheel-for now. A team led by Alberto Broggi at the University of Parma has built an autonomous car that will be set loose this summer to navigate Italian urban traffic by itself a formidable test. And Sven Beiker, the director of Stanford University's CarLab, says" automatic driving in some situations, such as stop-and-go traffic or smooth motorway driving, could be reliable enough for general use in a decade".[7]

CONCLUSION- In order to design an autonomous vehicle, one needs to make sure it'll incorporate all the senses, brains, and control abilities of the human driver, in order to maintain safety conditions on the road. This is achieved by applying various tools to the robotic car's mechanism, such as advanced sensors, computation, actuation and navigation systems. In this report we discussed Ad hoc networking is an emerging technology which has a very wide range of applications within the military environment, whether it be for combat or peace keeping operations. This innovative "Artificial Intelligence" approach aims to enable a human to "teach" the vehicle how to steer over weeks of training in an off-road environment .

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