CHAPTER (VANET) are likely to become the most

The number of vehicles on the road is increasing day by day which causes more accidents, more traffic jams, etc. To avoid these situations as well as to handle them better, vehicles should get road information (e.g. accident, jam, road surface condition) in a detailed way. Vehicular communication is a radio-based exchange of information between vehicles as well as between vehicles and infrastructure. Vehicular communication cannot only create an extended virtual information horizon, warning drivers early of dangers ahead and thereby avoiding accidents, but also allows for mitigation of unavoidable accidents by advanced short-range communication between the cars involved.

The new concept Car2X communication or vehicle to X communication has been introduced to solve these difficulties, where vehicles can communicate with other vehicles or infrastructures also known as V2V (Vehicle to Vehicle) and V2I (Vehicle to Infrastructure) communication 1. Considering the tremendous benefits expected from vehicular communications and the huge number of vehicles, it is clear that vehicular ad hoc networks (VANET) are likely to become the most relevant realization of mobile ad hoc networks. The appropriate integration of on board computers, roadmaps, and GPS positioning devices along with communication capabilities, opens tremendous opportunities, but also raises formidable research challenges.

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Vehicle and equipment manufacturers have recognised the opportunity of enhancing the surface transportation, by using the communication capabilities of the vehicular ad-hoc network (VANET) to offer an Intelligent Transportation System (ITS) to the drivers. 1 The major goal of this project is to improve the driver’s safety by informing them about dangers and situations that they cannot see. Recently, as vehicular communications have been identified as a key technology for enhancing road safety and transport efficiency, governments have started to allocate fixed portions of their communication spectrum to intelligent transport systems, IEEE 802.11p is an approved amendment to the IEEE 802.11 standard to add wireless access in vehicular environments (WAVE), a vehicular communication system which support intelligent transportation system (ITS) applications. It support data exchange between high speed vehicles and roadside infrastructure in the licensed ITS band of 5.9 GHz (5.85-5.925 GHz) frequency spectrum.

The Physical (PHY) and Medium Access Control (MAC) portions of the DSRC standard are currently being addressed by the IEEE 802.11p Task Group (IEEE 802.11 1999; IEEE P802.11p/D6.0 2009), which is widely considered as the leading technology for communication-based automotive applications. Major automotive Original equipment manufacturers (OEM), wireless device manufacturers, research institutions, public agencies, and private enterprises are conducting research on various topics pertaining to V2X communications, such as wireless channel modelling, mobility modelling, and routing protocols 1.

Every year globally the lives of approximately 1.25 million people are cut short as a result of road traffic crashes. Between 20 and 50 million people suffer fatal injuries, with many incurring permanent disabilities. Road traffic crashes (RTCs) cost countries approximately 3% of their gross national products; this rises to 5% in some low- and middle-income countries. Road traffic injuries have been neglected from the global health agenda for many years, despite being predictable and largely preventable. Evidence from many countries shows that dramatic successes in preventing road traffic crashes can be achieved through concerted efforts that involve, but not limited to the health sector.

Sustainable policies, strategies and special interventions have been adjudged to be effective in tackling challenges posed by road traffic crashes world over. It is in this light that the concept of education, enforcement, engineering and enlightenment has been vigorously applied by road corps in its determination to checkmate occurrence of road traffic crashes on Nigeria roads 2.

According to the Federal road safety corps (FRSC), report reveals the trend of crashes in Nigeria with details of occurrence in all states and federal capital territory of Nigeria. In year 2016, 9,694 RTCs were recorded out of which 2,638 were fatal, 5,633 were serious cases and 1,423 were minor and 5.043 persons killed. Generally, 56.6% (8,876) of the vehicles involved were commercial followed by private vehicles with 41.6% (6,521) while that of government and diplomatic were 1.7% (270) and 0.1% (15) respectively 2.

Figure 1.0: Accident statistics in Nigeria. FRSC 2
In order to address these challenges, expensive sensors, radars, cameras, and other state of-the-art technologies are currently integrated into vehicles to improve vehicle safety and driver comfort during travel. With Vehicular communication and efficient routing, road users can get first-hand information regarding the condition of the road, and even the vehicles before them. Efficient and safety mobility can be achieved through communication when the vehicle receives a hazard warning, the technology compares the vehicle’s position with the location of the hazard, and as soon as the vehicle approaches the danger spot, the driver is audibly and visually warned.

The main goal of vehicular networks is the safety of lives and property on the road, so as to allow information to be obtained from points far outside the driver’s field of vision, which is not the case with conventional sensors. Thus allowing the driver know of hazardous situations early on, by warning of potential collisions that might be possible due to driver’s negligence or lack of concentration. The safety network originates from a simple principle: every vehicle with vehicular communication technology can simultaneously and autonomously receive and send warnings. It also alert private and commercial vehicles of incoming emergency vehicles such as (Police and Ambulance). Networking makes the traffic not only safer, but more efficient as well.
The objectives of this project is to propose and validate a cost-effective VANET application and communication protocol that can be deployed efficiently on road networks. To accomplish this, the project has a major contribution which is the design of an all-IP network architecture, entirely based on 802.11, in which a new and enhanced MAC version is used at the Access Points so that an acceptable level of performance is obtained and a simulation software. These are the following objectives of the project:
Determination of existing infrastructure on selected road network.

To ensure anonymity of vehicles in the network.

To configure and deploy Safety applications such as PCN, EEBL and RHCN.

To evaluate and analyse test for speed limit broadcast done by the RSU in different scenarios such as damaged road, raining and traffic congestion.

To Survey the most relevant routing protocols for V2V implementation.

To overcome the actual problems and bring the intended contributions, a simulator will be used since it is not feasible to install Access points, Road side units (RSU) and have reproducible tests in order to compare the solutions. They are;
Road network street map importation using the openstreetmap project.

Safety applications such as post-crash notification (PCN), Road hazard control notification (RHCN), and Emergency electronic brake light (EEBL) deployment
Mix zones optimal deployment for protecting location privacy in the network.

A full simulation for four different routing protocols was done to select the best protocol for V2V Implementation.
The scope of this project is limited to safety and effective mobility and communication between vehicles, and synchronization with infrastructures. With vehicular networks communication protocols and scope, it does not alter the driver’s way of driving as this technology is not related to “self-driving cars”. The technology is only limited to safety and dialogue on the road between cars.

Recommendations for future project includes integration of an algorithm and AI to enable the car drives itself. If the VANET is not widely deployed, it may be difficult to assure connectivity. Thus, I believe that the commercial success of this technology is deeply related to the capacity of promoting their usage in a generalised way within a short period of time from the initial setup.

This chapter discusses in detail about the settings involved in vehicular ad-hoc network with numerous works concentrated by different authors. VANET (Vehicular Ad hoc Network) is a special sub class of MANET, where the vehicles are act as nodes. Unlike MANET the topology of VANET is highly dynamic and each node is acting as a router and node for sending and receiving messages within its range. Also vehicles are communicating with other fixed network infrastructure called RSU (Road Side Units). This section describes the high level architecture, communication mechanisms, routing protocols, security test cases and result analysis for each project carried out by authors.

2.1.1 Overview
Intelligent Transportation System (ITS) is a diverse and expanding subject, with some of its constituent parts converging or overlapping. For example, transport and travel information might be viewed under a Smart Cities agenda, and similarly connected cars are an articulation of Machine-to-Machine (M2M) Communications and the Internet of Things (IoT), Vehicular Ad-Hoc Network (VANET) networks is usually developed as a part of ITS. ITS are developing applications which, without embodying intelligence as such, target to provide innovative services relating to different modes of transport and traffic management and enable different users to be better informed and make safer, more coordinated, and ‘smarter’ use of transport networks. MANET is the short form of Mobile AdHoc Network. In ad-hoc networks all the nodes are mobile in nature and hence they can be interfaced dynamically in arbitrary fashion. VANET is the short form of Vehicular Adhoc Network, it is subclass of network of MANET type. The routing protocols of MANET are not feasible to be used in the VANET network, VANET is one of the main types of mobile ad hoc networks (MANETs). From the high level perspective, they are the same. However, some characteristics are specific for the VANETs that make them not similar to the MANETs. Compared with the other classes of mobile ad hoc networks, VANETs have unique characteristics. The main characteristics of the VANETs are as follows: heterogeneous communication range, mobility of the vehicles, geographically constrained topology, time varying vehicle density, frequently disconnected network, dynamic topology, and the vehicles being the components that build the network 1. The VANET routing protocols need to be designed considering factors such as the security, mobility and scalability of vehicular communication. The goal of VANET architecture is to allow the connection between vehicles or between vehicles and fixed road side units leading to the following three possibilities 1.

• Vehicle-to-Vehicle (V2V) ad hoc network: allows the direct vehicular communication without relying on a fixed infrastructure support and can be mainly employed for security, safety and dissemination applications.

• Vehicle-to-Infrastructure (V2I) network: allows a vehicle to communicate with the roadside unit mainly for information and data gathering apps.

• Hybrid architecture: combines both V2I communications and V2V. In this scenario, a vehicle can communicate with the roadside infrastructure either in a multi-hop or single hop fashion, depending on the distance, i.e. if it can or not access directly the roadside unit. It enables long distance connection to the Internet or to vehicles that are far away.

Vehicular Ad hoc Networks (VANETs) are group of vehicles with wireless communication enabled. Broadcasting is the task of sending a message from a source node to all other nodes in the network, which is repeatedly referred to as data dissemination. RSU is considered as wireless LAN access point and can provide communications with infrastructure. Also it can have higher range of communication up to 1,000 m 2.

The current ITS architecture is based on 4:
• Vehicle to Vehicle (V2V)
• Vehicle to Roadside (V2R)
• Vehicle to Infrastructure (V2I)
Figure 2.0 describes the high level structure of ITS solution based on V2V assisted V2I

Figure 2.0: Current V2V assisted V2I structure 3
There is a common factor in the wireless communication that it enables a large mobility and safety applications collection beside its assistance for V2V safety applications when mapped with RSU infrastructure, so V2V acts as the ITS program gateway because of being fully integrated status with the nearby nodes 1.

2.1.2 COOPERS (Co-operative Systems for Intelligent Road Safety)
The company AustriaTech coordinated the project COOPERS with 39 partners. A part of the 1st budget was contributed by the EU (European Union). The project started on February, 2006 and ended on July, 2010, which took a total of 54 months. The vision of COOPER’s project is to increase road safety and better traffic management for a specific road segment via wireless communication between vehicles and infrastructure. 3.
Figure 2.1 shows the high level architecture of the different traffic management systems, including the COOPERS based traffic management system. On the left side of the figure there is the conventional traffic management system where a traffic control centre directly communicates with the roadside system using VMS (Variable Message Sign) to show drivers different traffic and road conditions (e.g. speed limit, lane utilization etc.). The middle part of Figure 3 shows the designed high level architecture of the COOPERS project where they have introduced COOPERS Service Centre in between traffic control center, roadside system and vehicle. This chapter mainly focuses on the highlighted middle part. On the right side of the figure the future traffic management system proposed by COOPERS is illustrated where the so called COOPERS Service Centre will be integrated in the traffic control center.

Figure 2.1: Three models of traffic management system 4
The following section describes the functionalities of different entities of the above Figure 4.
Traffic Control Centre (TCC)
Source of traffic control related data as well as traffic information like road condition, weather condition etc.
COOPERS Service Centre (CSC)
The COOPERS service center collects traffic information (e.g. road works, traffic congestion, accidents, weather) and traffic control (speed limit, lane utilization) data from the Traffic Information Center and the Traffic Control Center respectively. CSC processes receive traffic related data and broadcast the data to OBU (also called Automotive PC) using TCP/IP via GPRS.
Roadside systems
Equipment installed on the roadside. This system can direct broadcast data acquired from traffic control center or broadcast data after further processing. The intended target is another roadside system and/or vehicles passing by.
The main and most important consumer of the traffic control data. Vehicles can receive traffic related/control data either from the traffic control center or roadside systems or other vehicles. Vice-versa, they can transmit traffic related data acquired by their sensors to the other instances mentioned above.

Test case
The following table shows the different actions of test case for variable speed limit application 3
Table 1: COOPERS traffic management test result
Actions Expected Result
Speed limit information message creation on the roadside
Speed limit based on the current road condition and lane is received and presented to the user
Check on APC (Automotive PC) if the message is received and presented to the user, also note the time
Speed limit information is lost
Leave motor way and observe whether the speed limit information is lost or not
Speed limit shown on the HMI
Enter the motor way and observe the speed limit information
This is validated after testing the log data
Continue driving and note the variable speed limit information period
Message information is changed
Change the speed limit information message on the TCC and check whether the vehicle received the new variable speed limit information message
Speed limit information is terminated
Observe vehicle HMI if speed limit information is
lost Speed limit information is lost
Create one of them on the roadside: weather condition warning, traffic congestion warning, incident warning, accident warning, road work information and wrong way driving warning.
Speed limit information message is created after these warnings
Location privacy is also to be considered to offer authentication. The privacy quality among vehicular ad hoc networks (VANETs) is based on location privacy which crucial for VANETs to flourish completely. Frequent pseudonym changing presents capable solution for location privacy in VANETs, if changes are made to the pseudonyms in an improper time or location, the solution may become invalid. Hence, to overcome the problem, proposed a valuable pseudonym changing at mix zones, strategy to attain the provable location privacy. The mix zone where numerous vehicles may meet was introduced first of all, e.g., a road junction when the traffic light turns red or an open parking lot near a shopping mall. The anonymity set size is considered as the location privacy metric and two anonymity set analytic models are developed to significantly examine the location privacy that is obtained by the mix zone strategy. The current model tracks a vehicle in a spatial–temporal way; hence advanced technique is to be considered which should use more character factors to track a vehicle and to discover new location-privacy-enhanced techniques under such a stronger threat model. Still an enhanced method is needed to provide safety for vehicular communication. IEEE and ASTM accepted the dedicated short-range communication (DSRC) standard which is the primary method for the next generation of vehicular safety communications. Communication services based vehicle safety normally needs dependable and quick message delivery which generally appeals broadcast communications in vehicular ad hoc networks (VANETs). 5 designed and approved a distributive cross-layer method for the plan of the control channel in DSRC and three levels of broadcast services are involved that are serious to most possible vehicle-safety-related applications. The network parameters based on current traffic load and network conditions are to be identified using IEEE 802.11p for better performance and reliability, because that is not processed by the proposed method. Signature based privacy is to be provided for VANETs.

As the medium access control layer of DSRC is highly dependent on IEEE 802.11 distributed coordination function (DCF) 6, the random channel access based MAC cannot provide guaranteed Quality of service.. Hence it is much vital to understand the quantitative performance of DSRC, in order to design or incorporate decisions on adoption, control, adaptation, and improvement. This chapter proposes an analytical model to evaluate the DSRC-based inter vehicle communication. The investigation had much impact on the channel access parameters associated with the different services such as arbitration inter-frame space (AIFS), 6 7.
The proposed model AQVA, suggests successful message delivery ratio and minimal channel service delay for broadcast messages which supports multi route messaging method for conference, media streaming services. The system works as an adaptive mechanism to inspect and provide support for the suitability of DSRC with respect to QOS over AODV) 7 in inter-vehicle and road safety applications.

VANET classifies routing protocols in five different types 9: Topology, Position, Cluster, Geocast, and Broadcast methods. Each method has its own advantages and disadvantages. Advantage of proactive routing protocols is that it does not adopt any route discovery mechanism since destination route is stored in the background, while its disadvantage is that it provides low latency for real time service applications, as well leads to maintenance of unused data paths, which uses the available bandwidth. FSR 6 8 belong to this category.
Several studies have been published comparing the performance of routing protocols using different mobility models or performance metrics. One of the first comprehensive studies was done within the framework of the City Urban scenario 7 compared a larger number of VANET protocols. However, link level details and MAC interference are not modelled. Study by 8 compared the same protocols as the work by 9 yet for specific scenarios as the authors understood that random mobility would not correctly model realistic network behaviours, and consequently the performance of the protocols tested. In general, the survey summarizes that routing protocols of VANET needs improvement in (a) routing traffic load, (b) overall throughput, (c) end-to-end delay (d) control overhead (e) handoff and (f) session connectivity time.

2.1.5 Overview of vehicular communications
An important aspect of vehicular networking and intelligent transportation systems shows significant promise in wireless communication with cars. This communication could be between cars (V2V) or between cars and a fixed infrastructure (V2I) such as roadside units (RSUs). Vehicular ad hoc networks (VANET) should, upon implementation, collect and distribute safety information to massively reduce the number of accidents by warning drivers about the danger before they actually face it. Such networks comprise of sensors and on board units (OBU) installed in the car as well as roadside units (RSU). The data collected from the sensors on the vehicles can be displayed to the driver, sent to the RSU or even broadcasted to other vehicles depending on its nature and importance. To achieve safety in vehicular network management and to coordinate the diverse standards in the vehicular network, the recent developments in the wireless communication technology and ITS have been combined. The US department of Transportation (USDOT) and ETSI extending the worldwide harmonized standards for cooperative-ITS(C-ITS), these practices continue to emerge. Furthermore, countries such as Australia and South Korea want to follow this. With significant advances in alternative fuels and connected vehicles reworking automobile transportation, it is time to unify the association for nursing an intelligent future in transportation worldwide and engulf cross-disciplinary approach to shorten the considerable time required to promote transportation standards.

2.1.6 Vehicular Network System architecture and communication links
The comprehensive and seamless networking of vehicles and infrastructure represents a significant organizational and technological challenge. The sim™ architecture as presented by 10 is complex, as many different protocols and data formats are required and many stakeholders are involved. Figure 4 shows the system architecture from the perspective of the different components and domains as well as their interactions. In general, the system architecture is composed of two domains. In particular, these are:
• Vehicle domain, which comprises the hardware and software for the vehicular subsystem, and the
• Infrastructure domain, comprising the subsystems relevant for the infrastructure services.

The vehicles themselves are able to communicate with each other using dedicated short range (DSRC) communication technology based on IEEE 802.11p. Therefore, they are equipped with so-called ITS vehicle stations (IVS), which deploy the ITS applications on respective hardware. The sim™ scenario further includes RSUs, which are also integrated in the vehicular network and, are able to communicate with an IVS. A RSU can be connected to traffic light switches in order to control traffic signs in urban scenarios. Moreover, the RSUs are connected to the infrastructure domain in order to provide connectivity from vehicles to backend services. Besides 802.11p ad-hoc communication, as a key technology, vehicles are equipped with cellular communication hardware in order to have IP-based access to backend services and to route safety-related messages over long distances. If available, vehicles may use IEEE 802.11b/g for IP based connections via hotspots in inner city scenarios.
The communication between vehicles, or between a vehicle and an RSU is achieved through a wireless medium called WAVE (Wireless access for vehicular environment) otherwise known as DSRC (Dedicated Short Range Communication). This communication method provides a wide range of information to drivers and travellers in order to enhance road safety and provide comfortable driving. The architecture components are the application unit (AU), On board unit (OBU) and Road side unit (RSU). Basically, the RSU hosts an application that provides services and the OBU is a peer device that uses the services provided, then each vehicle is each vehicle is equipped with an OBU and a set of sensors and sophisticated cameras to collect and process the information, then send it on as a message to other vehicles or RSUs through the wireless medium 10.

Fig. 2.2 Vehicular communication architecture
The communications infrastructure to support V2V and V2I applications must meet the following requirements;
Dedicated licensed bandwidth
Low latency
Priority for safety applications
Security and Privacy
Fast network acquisition
High reliability
2.1.7 On board unit (OBU)
This is a wave device that is mounted on-board which is used for exchanging information with the RSUs and other vehicles with OBUs. It comprises of a resource command processor (RCP), and a read and write memory interface to store and retrieve information. There’s also a user interface to connect network device for short range wireless communication based on IEEE802.11p radio access technology. IEEE802.11a/b/g/n may be used for another network device for non-safety applications. The OBU also provides a communication services to the AU and forwards data on behalf of other OBUs on the network. The main functions of the OBU are wireless radio access, ad hoc and geographical routing, network congestion control, reliable message transfer, data security and IP mobility 12.

2.1.8 Application Unit (AU)
This device is equipped within the vehicle that executes applications provided using the communication capabilities of the OBU. The AU can be a dedicated device for safety applications or a normal device such as a smart device (IOS) or Google’s android device to run the Internet. The connection between the AU and the OBU is through a wired or wireless connection and may reside with the OBU in a single physical unit; the distinction between the AU and the OBU is logical.

The AU communicates with the network solely via the OBU which takes responsibility for all mobility, safety and networking functions. The figure below is the architecture and components of a connected vehicle 11.

Fig 2.3. Schematic diagram of connected vehicle
2.1.9 Road side unit (RSU)
The road side unit serve as an access point or base station which is usually fixed along the road or in dedicated locations such as junctions or near parking spaces. The RSU is equipped with sensors too that can detect conditions of the road such as when there is pothole or road construction going on, it is also equipped with network device for dedicated short range communication based on IEEE 802.11p radio technology.
The following are main functions of RSU;
Redistribution of information to other OBUs or equivalent equipped vehicles, by extending communication range of ad hoc network.

Fig 2.4. RSU extends range of ad-hoc network. 11.

Running safety applications such as road construction or work zone, accident warning by using vehicle to infrastructure communication (V2I).

Fig 2.5. RSU provides information source (running safety applications) 11 Provides internet access to the vehicles.

Fig 2.6. RSU provides internet access to the OBUs. 12

Fig 2.7. Basic vehicular communication scenario. 12
2.2.0 Wireless access technologies in VANET
It is safe to ask questions about the frequency spectrum VANET uses, the kind of wireless technology and how does it work. There are numerous wireless access technologies available today, which can be used to provide the radio interface required by the vehicles in order to communicate with each other, V2V communication, or to communicate with the RSUs, V2I communication. The wireless technology serve as a path or channel to transmit information for road safety, traffic efficiency and to provide driver and passenger comfort by enabling a set of safety and non-safety applications. Here, we take a brief look at wireless access technologies and the one VANET uses:
Cellular systems (2/2.5/3/3.5): The major objective of cellular spectrums is to reuse frequency. Which means the ability of the system to reuse limited frequency available for GSM service 14 GSM uses both frequency division multiple access (FDMA) and time division multiple access (TDMA) schemes. Global system for mobile (GSM) communication considered to be one of the cellular system standards that provides a data rate of a maximum of 9.6 Kbps and is characterised as a second generation (2G) 15. There are two frequency bands are available for GSM 890-916 MHz for uplink and 935-960 MHz for downlink, and they are divided into channels and capacity, where each channel is 200 kHz 14. General packet radio service (GPRS) also known as 2.5G 16 is an evolved version of GSM; GPRS is standardised by the European Telecommunications Standards Institute (ETSI) to accommodate data transmissions at high bandwidth efficiency, so as to enable a data rate of up to 170Kbps 16. It operates at 1710-1785 MHz for uplink and 1805-1880 MHz for downlink, Enhanced Data rates for GSM Evolution (EDGE); also known as 2.75G are an evolution of GPRS which provide a peak date rate of 384Kbps 17. To enable us transfer data at high speeds or rate, 3G came into existence. The universal mobile telecommunication system (UMTS), and it is evolved version the high-speed downlink packet access (HSDPA), provides a data rate of up to 2 Mbps. Another comparable cellular system is the CDMA2000 which provides 3 Mbps for downlink and 1.8 Mbps for uplink 15 respectively.

WiMAX: Which means (Worldwide interoperability for microwave access) is a family of wireless communication standard based on IEEE 802.16 set of standards. WiMAX forum published three licensed spectrum profiles: 2.3 GHz, 2.5GHz and 3.5GHz, in an effort drive standardisation and decrease cost. IEEE 802.16e provides a high data rate and covers a wide transmission range with reliable communications and high quality of service (QoS), which makes it suitable for those applications requiring these features such as multimedia, video and voice over internet protocol (VoIP) applications. WiMAX achieves a high data rate of up to 35 Mbps using multiple-input and multiple-output (MIMO), with an orthogonal frequency division multiplexing (OFDM) and covers a transmission range of 15 Km 18.

5G/MILLIMETER-WAVE Technology: The 5G/MMWAVE is mostly known as the technology for machines, it operates at between 60 and 64 GHz. It can fully support V2V communication, and there are other features involved in this technology as it is less affected by extreme weather conditions and also support line of sight communication. Furthermore, antenna size is a huge concern in VANET, the MMWAVE supports smaller antenna sizes that can be easily integrated in a vehicle in ITS environment 15. To conclude, this technology is best suited for high data rates. Therefore, the 5G/MMWAVE communication technology would be beneficial in different aspects or different modes of communication in the ITS environment.

Dedicated Short Range Communication (DSRC); VANET adopts DSRC which is a standard that aims to bring vehicular networks, the first generation of the Dedicated Short-Range Communication (DSRC) system operates at 915 MHz and has a transmission rate of 0.5 Mb/s. One example of a first generation DSRC application is EZ-Pass that is used for electronic toll collection. DSRC radio technology is based on IEEE 802.11p, which originated from IEEE 802.11a and was amended for low overhead operation in the DSRC spectrum 19. The second generation of DSRC started in 1997 when Intelligent Transportation System (ITS) America, requested that the Federal Communication Commission (FCC) allocate an additional 75 MHz of bandwidth. In October 1999, the FCC allocated the 75 MHz of bandwidth in the 5.9 GHz band for the second generation of DSRC, 20. The 75 MHz spectrum is divided into seven channels starting from channel number 172 ending with channel number 184; the capacity of each channel is 10 MHz Channel 178 is the control channel (CCH), which is used exclusively for safety communications; channels 172 and 184 are reserved for safety applications, while the other service channels (SCH) have for both safety and non-safety uses. It is expected that the 5.9 GHz DSRC must have a low cost and be very scalable, it should also require no usage fee from the users to access the network.

The whole DSRC protocol stack including IEEE 802.11p (MAC and PHY layers) standardized by the IEEE 1609 working group and called wireless access in a vehicular environment (WAVE) 19. The 5.9GHz DSRC overcomes many of the weakness associated with 915 MHz DSRC. To begin, 5.9 GHz DSRC supports high speed data transfers ranging from 6 Mb/s to 27 Mb/s. Under certain circumstances, the data rate can reach 54 Mb/s when two service channels are combined to form one 20 MHz channel. On the contrary, 915 MHz DSRC supports a data rate of only 0.5 Mb/s. Also, the transceivers or antenna used in vehicles required a reduced transmit power compared to 915MHz DSRC. In addition, the communication range is increased for 5.9 GHz DSRC. The interference potential of 5.9 GHz is much lower than for 915 MHz DSRC, the only interference in the 5.9 GHz band comes from sparsely located military radars and sparsely located satellite uplinks, whereas the 925 MHz suffers from considerable interference. Table contains a comparison between 925 MHz DSRC and 5.9 GHz DSRC.

Table 2: Comparison of DSRC technologies.

Parameters 902-928 MHz Band 5850-5925 MHz Band
Data Rate
Interference potential
Maximum Range
Minimum Separation
Channel Capacity
Downlink Power
Uplink Power 12 MHz
0.5 Mbps
One communication zone
300 ft.

1500 ft.

1 to 2 channels
Normally less than 40 dBmNormally less than 6 dBm75 MHz
6 Mbps-27 Mbps
Overlapping communication zones
50 ft.

7 channels
Normally less than 33 dBmNormally less than 33 dBm
DSRC also supports a number of different network protocols for interoperability in the hope of gaining widespread adoption. To begin, DSRC supports the long-established TCP/IP protocol, which allows IP based routing in DSRC. As a result of supporting TCP/IP, most of the traditional Internet applications are available in the VANET. Next, WAVE Short Message Application is used for the majority of vehicle-to-vehicle safety communications. The reason that IPv6 is not used for many of the safety applications is because of the size associated with IPv6 headers. Fig 2.8 Analyses the DSRC spectrum.

Fig 2.8. 75MHz DSRC spectrum 19
2.2.1 Channel Assignment
The 5.9 GHz spectrum is composed of six service channels which are of course 10 MHz each. Now the data rates possible for a 10 MHz channels are 6, 9, 12, 18, 24 and 27 Mb/s with a preamble of 3Mb/s. The modulation scheme employed here is Orthogonal Frequency Division Multiplexing (OFDM). Also, the DSRC doubles the guard period when comparing with IEEE 802.11a. The DSRC channel breakdown is illustrated in figure (2.9) below.

Fig 2.9. DSRC channels
The following list contains the channels of DSRC and the type of applications that are supported by the channel.

Channel 172 is dedicated for medium power safety applications.

Channel 174 is reserved for medium power applications that are shared by all.

Channel 175 is a combination of channels 174 and 176.

Channel 176 is also reserved for medium power applications that are shared by all.

Channel 178 is the control channel it support all power levels, safety application broadcasts, service announcements, and vehicle-to-vehicle broadcasts messages.

Channel 180 is reserved for low power configurations and provides little interference when units are separated by 50 ft. or more.

Channel 181 is a combination of channels 180 and 182.

Channel 182 is reserved for low power configurations and provides little interference when units are separated by 50 ft. or more.

Channel 184 is reserved for a high power service channel that is used to coordinate intersection applications.

2.2.2 DSRC Protocol stack and complementary Technologies
The wireless technologies were modified based upon how well they meet the requirements of DSRC. In the end, a modified version of 802.11a was chosen as the primary means of communication for DSRC. For example, both satellite systems and cellular systems offer a significant amount of bandwidth but have too high of latency to be considered useful for some applications of DSRC. In particular cellular technology which lack broadcast support, and the present time, both cellular and satellite technologies are expensive and the cost of wireless access for DSRC is free because the technology is based on Ad-hoc network. Also, infrastructure costs of DSRC are much cheaper than both cellular and satellite. The table below contains the comparison of wireless technologies.

Table 3: contains a comparison of wireless technologies
Parameters DSRC Cellular Satellite
Cost 100 1000 meters
200 µs
None Kilometres
1.5 to 3.5 s
Expensive Thousands of kilometres
10 to 60s
Very expensive
2.2.3 DSRC Protocol Stacks
DSRC has two distinct transport/network layer protocols, whereby a typical V2I communication would use TCP/UDP, such as accessing internet applications or location based services. Wave short message protocol WSMP, would also be used in V2V communication, most importantly for safety applications. The figure below is the DSRC protocol stacks for WSMP and TCP/IPV6. 21

Fig 2.10. Two DSRC protocol stacks (left) and TCP/IPV6 (right).

2.2.4 Antenna requirements
Traditionally, radio and mobile telephone antennas on cars have been vertical monopoles or collinear antennas with phasing coils. They tend to provide omnidirectional radiation pattern which is very versatile for vehicular communication due to the topology of the network 22. The finite size of the ground plane formed from metallic car surfaces causes the direction of the maximum gain to be tilted above the horizontal, These attributes are appropriate for these applications, since the road side unit could be in any direction, and is usually at an elevation considerably higher than the car. These traditional mobile antenna patterns are illustrated in Figure 13 , where (a) explains the omnidirectional pattern used by a traditional mobile antenna (dashed) and an elliptical pattern (solid) that would provide better down-road range while still providing adequate cross-road coverage, and (b) shows the vertical pattern for a quarter-wave monopole above a 1 m diameter ground plane at 5.9 GHz. Note that the gain in the horizontal direction is about 4.6 dB lower than the received peak gain 23.

Fig 2.11. Antenna pattern for vehicular networks on on board unit.

On moving vehicles, small-scale fading also results in fast variations in the signal amplitude with time. Multipath components arriving from different directions and infrastructure will be shifted in frequency by changing amounts owing to the Doppler Effect.

These components with slightly changing frequencies will go in and out of phase with each other, thereby causing the amplitude variations. The only specific way in which the amplitude changes is determined by the relative amplitudes and phases of the multipath components. The received signal with frequency is referred to as the Doppler spectrum 23 24. For the V2I case, a Gans spectrum 22 using a single speed parameter may be appropriate if the car is surrounded by dense scatterers. For most of the V2V communication, the shape of the spectrum is influenced by the respective speeds of both cars. A multipath model in which two cars are surrounded by an elliptical ring of scatterers has also been proposed, 23 but the Doppler spectrum was not discussed.

2.2.5 Vehicular Networks Applications Enabled by DSRC
V2I and V2V allows a number of unique applications standardized for DSRC, which provides a wide range of needful information to drivers and travellers. The goal of the standardization is to develop a set of applications protocols. Integration of on-board devices with the network interface, different types of sensors, camera and GPS receivers, grant vehicles the ability to collect, process and disseminate information about itself and its environment to other vehicles in close proximity to it. While there will be a common set of application protocol between OEMs, the automobile manufactures will be able to differentiate their products based on the user interface they provide to the driver. That has led to enhancement of road safety and the provision of passenger comfort 16 for example, a simple user interface may only give the driver visual feedback. On the contrary, a more advanced user interface may provide the driver with a touch screen mounted within the dashboard, allowing the driver a visual display of the road. To conclude, each vehicle has an OBU that follows the DSRC specification, but each automobile manufacturer is able design or customise interface of the OBU with a proprietary user interface.

VANET applications are classified according to their importance and purpose, DSRC is composed of safety, and non-safety applications. A sub category of non-safety applications is traffic management applications and comfort applications. Where the objective of the public safety applications is the improvement of overall safety of the transportation infrastructure. The latter increase the comfort of the driver and traffic management by adding value added services. Though safety applications are always given high priority over the non-safety applications.

2.2.6 Public Safety Applications
These applications use the wireless communication between vehicles or between vehicles and infrastructure, in order to improve, and protect the safety of life, health, or property. Safety applications have as an essential requirement for the ability to gather information through a vehicle’s sensors, and camera from other vehicles or both, in order to process and broadcast information in the form of safety messages to other vehicles or infrastructures depending on the application and its functions, and importance. A couple of safety applications are used in VANET, such as;
Road Hazard Control Notification (RHCN)
Post-Crash Notification (PCN)
Lane Change Assistance (LCA)
Emergency Electronic Brake-Light (EEBL)
Traffic Signal Violation Warning
Road Hazard Control Notification (RHCN); A vehicle detecting a road hazard (e.g. a pothole or ice) broadcasts warning messages to vehicles within the affected area. Approaching vehicles notify their drivers of the hazard. This application would be useful anytime a driver would benefit from forewarning of a potential hazard on the road. Potential hazards that might be addressed by this application include, but are not limited to the following:
Crashed or stopped vehicle
Roadway damage such as potholes
Fallen trees or objects in the roadway
The presence of animals on or near the roadway.

Once hazards are reported, an algorithm running within the vehicle system would track reports and determine their validity. Once hazard was verified, the location of the hazard nearby vehicles would be used to issue appropriate notifications of the approaching hazard.

Post-Crash Notification (PCN): This application aims to prevent potential accidents before they happen, a vehicle which is disabled because of foggy weather or due to an accident sends a warning messages to other vehicles coming travelling in the same direction, therefore a vehicle involved in a crash broadcasts warning messages to approaching vehicles until the crash site is cleared. Approaching vehicles notify their drivers of the crash. This application does the work of a collision warning, we should think of a distracted driver in this scenario, who lost concentration while driving, and it happens another vehicle with DSRC enabled is few meters away from his vehicle. With the help of sophisticated sensors and camera’s, he will be audibly alerted by the OBU, and provided the driver fails to react at the expected time, the vehicle autonomously brakes itself to avoid a collision with the vehicle in front.

Lane Change Assistance; The lane change warning application is a vehicle-to-vehicle application where each vehicle receives periodic broadcast from the surrounding vehicles. Also, each vehicle maintains a table or database containing the vehicles in the immediate radar. For this application to be successful, the vehicle locations maintained in the table must be very precise. When the driver signals his or her intent to change a lane, the OBU uses the received data to determine if the road conditions are safe to perform a lane change. The main drawback of the lane change warning application is that it requires that a high percentage of vehicles are DSRC equipped. One means triggering the application is when the turn signal is applied by the driver, which then invokes the lane change algorithm. If the attempted lane change puts the driver in danger, a warning is generated. A very important scenario where the application is useful is during overtaking.

Emergency Electronic Brake light: This application provides a warning to a trailing vehicle or platoon. When a vehicle in front of it applies its brakes. It simply notifies the driver whenever a vehicle upfront applies a sudden brake. The emergency electronic brake light application is beneficial in situations where visibility is limited, such as poor weather conditions. Figure (2.12) illustrates a vehicle A broadcasting a warning message after applying its brakes. The data contained in vehicle A’s broadcast message is the deceleration rate and braking vehicle’s location. When vehicle B receives the warning, an algorithm is created to determine the importance of the message and whether or not the vehicle is endangered 26. If so, a warning message is sent to the driver. The emergency electronic brake light application significantly reduces accidents by giving the driver a warning before they are able to visually sense the danger.

Fig 2.12. Emergency Electronic Brake Lights
Traffic Signal Violation Warning: This application provides the greatest benefit in estimated functional-life years saved by the applications that could be implemented in the short-term. Passing through an intersection is one of the most dangerous activities that one encounters while driving. The goal of this application is to reduce collisions at intersections. In this scenario, a RSU is placed near an intersection that has a traffic light. Infrastructure-to-vehicle communication is used to warn approaching vehicles of the status of the traffic light and to alert drivers of a potential light violation. The data sent to approaching vehicles includes the status of the light, the time of light changes, the traffic light location, and the direction of the light signals. When a vehicle receives a traffic signal violation warning message, computation is performed on the received data to determine if the driver is at risk of inappropriately entering the intersection and if so a warning is issued to the driver. The traffic signal violation warning is a simple one-way application that provides the greatest safety benefits of the VANET applications. More complex variations of this scenario are used for applications such as left-turn assistance and stop sign movement assistance.

Fig 2.13. Traffic Signal Violation Warning
2.2.7 Comfort/entertainment applications
This category of VANET application is also referred to as non-safety applications the primary objective is to improve drivers passengers comfort level, and enhance traffic efficiency. Non-safety applications increase the overall comfort of the driver. Electronic toll collection is one possible non-safety application. Instead of a driver having to stop at a toll booth to make a payment, the payment is made electronically through the network. They can provide drivers or passengers with weather and traffic information, free parking spaces and detail the location of the nearest restaurant, petrol station or hotel and their prices. Passengers can play online games, access the internet and send or receive instant messages while the vehicle is connected to the infrastructure network 27. Applications such as these will probably not be implemented in DSRC in the foreseeable future because of the limited bandwidth and the fundamental focus on safety applications. The in-car entertainment application would surely consume a large amount of network resources. It is expected that commercial organizations will find numerous other uses for DSRC and the greatest innovation of DSRC will come from the non-safety applications. The table below list and categorise some applications of VANET.

Table 4: Applications of VANET
Safety Applications Traffic management Applications Comfort Applications
Slow/Stop Vehicle advisor
Work zone warning
Emergency electronic Brake-Light (EEBL) Electronic toll collection Contextual information
Post-Crash Notification (PCN) Approaching emergency vehicle File sharing
Road Hazard Control Notification
(RHCN) Optimal speed advisory Web browsing
Lane Change Assistance (LCA)
Enhanced route guidance and navigation Social networking
Blind Spot Warning
2.2.8 Message Dissemination in Vehicular Networks
Safety applications rely on exchanging messages disseminated to all or a selected portion of vehicles. The objective is to alert the drivers about a dangerous situation, an accident for instance. However, dissemination mechanisms may lead to bandwidth congestion and storm situation. As a result, a timely disseminated warning may help the driver to avoid an emergency stop or sometimes, a collision. The most promising applications of Vehicular Ad Hoc Networks (VANET) are safety applications, embedded systems, cameras and sensors are becoming ubiquitous and more often found in our vehicles and Data exchanged by these systems help the driver to take appropriate decisions. Safety applications can be more efficient if information from these sensors is exchanged between neighbouring vehicles. Communication between vehicles can also be used to alert the drivers about a dangerous situation, an accident for instance. As a result, a timely warning may help the driver to avoid an emergency stop or sometimes, a collision. All safety applications suppose that exchanging messages which are disseminated to all or part of the vehicles come from an infrastructure or from the vehicles themselves. Data dissemination generally refers to the process of spreading data or information over distributed wireless networks. From the networking point of view, it requires broadcast capabilities at the link layer, allowing a frame to be transmitted to all the vehicles in the radio scope. It also supposes implementation of network and transport mechanisms to disseminate the message in the whole network 28.

2.2.9 Wireless Transmission Acknowledgement
A unicast transmission is systematically acknowledged from the receiver with a specific frame (an ACK). However, for a broadcasted frame, it is not practical to receive an ACK from each node receiving this frame. Indeed, if the receptions are acknowledged, each vehicle receiving the frame will send, almost at the same instant, an ACK back to the transmitting node. This process may lead to a high collisions rate when multiple receivers coexist 18. This problem is known as the ACK explosion problem. Moreover, the sender is not supposed to have the list of the potential receivers. In the improbable case, where the sender knows the nodes/vehicles in its radio range, the use of ACK may be counter-productive. Assume that a vehicle is sending messages to 50 neighbours in its radio range. One of these vehicles is at the limit of the radio range and presents a high frame error rate (FER). When the sender sends its broadcast frame, it will be acknowledged 49 times. Since there is a missing ACK (from the vehicle with a high FER), the frame will be re-broadcasted again and again 25. Each time, there will be 49 receptions and 49 ACK until the 50th vehicle receives the frame or the maximum number of transmissions is reached. This scenario may produce a lot of collisions and may waste network and OBU resources. Consequently, acknowledgment should not be permitted for broadcasted frames.

2.3.0 Transmission Procedure and Frame Format
The frame broadcasting transmission procedures are different in vehicle-to-vehicle and in infrastructure mode. When the vehicle-to vehicle mode is used, the broadcast frame is directly sent by the source to the vehicles in the radio range. The destination address is then the medium access control (MAC) broadcast address (ff:ff:ff:ff:ff:ff) 29. Vehicles in the radio range of this source receive the frame directly. IEEE 802.11 p interface of a vehicle called on-board unit (OBU), has to be associated with the Roadside Unit along the road. When the OBU intends to broadcast a frame, it sends it to the RSU, which in turn broadcasts it.

Fig 2.14. VANET operation mode with ad-hoc versus infrastructure
From the figure above, Frames 1 and 2 correspond to a broadcast transmitted from a vehicle in infrastructure mode. Frame 1 is the frame sent from the vehicle OBU to the RSU. The first address is the destination address, i.e., the RSU MAC address. The second address is the source address, the OBU MAC address 28. The third address is the broadcast address (ff:ff:ff:ff:ff). When the RSU broadcasts this frame, it permutes these addresses. The destination address becomes the broadcast address, the source address becomes the RSU MAC address, and the third address becomes the OBU MAC address. The other fields of a frame are the Frame Control, Duration ID, Sequence Control, and frame check sequence (FCS). In vehicle-to-vehicle mode, the frame is directly broadcasted 30. The addresses are then the broadcast address and the MAC address of the source OBU. For the third address, the OBU MAC address is reused as there is no OBU. The Sequence Control is the frame number and the FCS is a field used to detect transmission errors.

Fig 2.15. Various frame formats 31
2.3.1 Broadcast Message Dissemination
Messages must be sent within the time specified by the application. Therefore, a protocol implemented at an upper layer is required to disseminate the message at several hops. This protocol must compensate the lack of reliability of the IEEE 802.11 p and guarantee a fast and efficient delivery of the messages 31. The service offered by the layer 2 simply consists in broadcasting a frame to the nodes in the radio range of the sender, at one hop. In IEEE 802.11 p, this service is unreliable. The sender does not know if its transmission has been received, and there is no retransmission in case of failure. However, safety applications rely on the dissemination of alert messages in a given area (limited by the number of hops or by geographical positions), not only at one hop. These messages are crucial as they contain important information on road safety. They need to be received by all the vehicles located in the area specified by the safety application. In other words, applications require a reliable dissemination of the messages. Delivery delay is also an important factor 22.

It should be noted there is a problem in broadcasting in ad hoc networks, which is referred to as broadcast storm. This problem occur when we are to use a basic flooding system which is also called blind flooding 33. Blind flooding work as follows. When a node receives a packet which needs to be disseminated within the network, it checks if it is the first reception of the packet. If yes, it broadcast it; otherwise it silently discard it.
Since each node forwards the packet, it leads to an important redundancy which depends on the network density: therefore a node will receive as many packets as it has neighbours in its radio range. In Fig. 18, comparison of the number of transmission and receptions with the blind flooding and an optimal broadcasting.

Fig 2.16. Example of a topology in VANET
In the figure above, the edges represent the wireless links between the nodes. We assume that node B wants to broadcast a message in the whole network. In the optimal case, we need only two broadcasts to reach all the nodes: B initially broadcasts the message and it is forwarded by C. The transmission from B reaches nodes A, C, E, and F. The transmission from C reaches D. All the nodes have received the message with only two transmissions. In case of a blind flooding, each node transmits the message once. There are six transmissions and each node receives the message as many times as it has neighbours: two times for A and D, four times for B, C, F, and E. this is the famous storm problem.

In vehicular networks, a node may have up to 100 m neighbours, where the radio range of the IEEE 802.11p may reach up to 1 km and the density of vehicles may reach more than 100 vehicles per kilometre 2131. Such coverage will lead to 100 receptions for each vehicle. A scenario like that will congest the network, causing packet transmissions to face heavy collisions, therefore wasting a lot of bandwidth and CPU resources in the OBU.

2.3.2 Security Challenges for Vehicular Networks
Intelligent Transportation System (ITS) have been deployed in recent years for toll collection, fleet logistics and management, anti-theft protection, pay-as you- go insurance, telematics, traffic information, and active road-side signs32. In addition to entertainment services on board, the main aim is to improve road safety and driving conditions. A wireless network of intelligent vehicles can make a highway travel safer and faster. But can hackers use the system to cause accidents? By this question they mark the importance that automakers must give to VANETs security. It is essential e.g. that the vital information cannot be modified or deleted by an attacker. Securing VANETs systems must be also able to determine the responsibility of drivers while maintaining their privacy. Communications passing through a vehicular network as well as information about the vehicles and their drivers must be secured and protected to ensure the smooth functioning of intelligent transportation systems 32. The unique features of VC are a double-edged sword: a rich set of tools would be offered to drivers and authorities but a formidable set of abuses and attacks would become possible if the appropriate safeguards were not in place. An attacker could ‘contaminate’ large portions of the vehicular network with false information, announcing, for example, non-existent dangerous or congested road conditions, and thus misinform drivers and cause traffic jams. Alternatively, drivers could purchase software or hardware VC system ‘hacks’ or ‘upgrades’, just as they now often purchase police radar detectors or modify their cars for additional horsepower. Such VC system modifications could, for example, allow private vehicles to transmit messages as if they were an emergency vehicle (e.g. ambulance, police patrol, or road maintenance vehicle), or they could have unsuspecting drivers notified by their OBUs to slow down and yield, and in this way offer fast movement for some vehicles even in traffic jams 33. Again, receivers deployed in a city centre, at highway exits, or even in a celebrity’s neighbourhood could record transmissions from passing vehicles to be used later in tracing their location and inferring private information about their passengers.

From security point of view, the entities directly involved in the security of VANETs are:
The Vehicle (OBU); although it doesn’t reflect the actual reality. It basically refers to the vehicle itself and the driver. In a VANET network, we can distinguish two kind of vehicles: the normal vehicles that exist among network nodes and operate in a normal way, and the malicious vehicles.

Road Side Unit (RSU): As in the case of the OBU, we can distinguish normal RSU terminals, which operate in a normal way, and malicious RSU terminals.

The driver: definitely the driver is the most important element in the VANET safety chain because it is ubiquitous and he has to make vital decisions. In addition, all used cases currently scheduled for VANET applications make the driver as an interactive component with the driving assistance systems.
The attacker: In the context of VANET security, the attacker is one (or more) compromise entity that wants to violate successfully the security of honest vehicles by using several techniques to achieve his goal. An attacker can also be a group of vehicles that cooperate together. An attacker may be internal (an authentic vehicle of the VANET network) or an external vehicle. It can also be classified as rational (the attacker follows a rational strategy in which the cost of the attack should not be more than the expected benefit) or irrational (a suicide bomber is an example of irrational strategy) 33. An attacker can be either active or made his attack with an exposed manner or passive and his actions cannot be detected.

Third Parties: this involve all digital equivalents of stakeholders in a direct way in intelligent transportation system. Among these third parties, the regulator of transport, vehicle manufacturers, traffic police, and judges. They all have their respective secrets/public key pairs. These public keys can be integrated for example into the OBU which is supposed an inviolable device.

2.3.3 Classification of VANETS attacks
VC systems comprise network nodes, or, in other words, wireless-enabled computing platforms mounted on vehicles and RSUs. Like any other communication and data processing systems, VANETs are exposed to various types of threats and attacks. The absence of the energy problem and the ability of an OBU to accommodate dozens of microprocessors give the vehicle an important capacity of processing and computing. Due to the high mobility in Vehicular networks, the two mentioned advantages affect the feasibility of attacks. Thus, there are possible attacks in an ad hoc network that will be impossible for VANETs and vice versa. Given the diversity of VANETs possible threats and attacks, and in the interests of clarity and simplification, it is necessary to classify them from the Figure below.

Fig 2.17 Example of VANET threats and attacks. 33
2.3.4 Attacks on availability
Availability is a very important factor for VANETs. It guarantees that the network is functional, and useful information is available at any time. This critical security requirement for VANETs, which main purpose is to ensure the users’ lives, is an important target for most of the attackers. Several attacks are in this category, but the most famous are the Denial of Service attacks (DoS). The jamming attack, is a physical level of Denial of Service attack. Jamming in its basic definition is the transmission of a signal to disrupt the communications channel, it is usually intentional 32. For a successful adaptive jamming attack, the jammer must act at the same time that the activity of the useful signal to jam. It must also choose the most effective signal transmission model that merges the best the receiver. The Broadcast tampering attack: In this type of attack, the attacker tries to make and inject fake security alert messages in the network. This may hide the true safety messages to legitimate users, it can cause also accidents and seriously affect the overall network security 34. In general this type of attack is possible for a legitimate node.

2.3.5 Attacks on authenticity and identification
In vehicular networks, Authenticity is a major challenge of VANETs security. Any violation or attack involving the process of identification or authentication exposes all the network to a serious consequences as all existing stations in the network must authenticate before accessing available services. To ensure authenticity in a vehicular network is to protect the authentic nodes from outside or inside attackers infiltrating the network using a falsified identity 34. In Sybil attack the idea of the Sybil attack as presented for the first time in 37 is that a malicious entity can present multiple identities at once. One of the direct means by which two entities can convince a third that they are distinct is to run, at the same time, some tasks that one entity cannot do it alone. To ensure the identity of a node, several techniques have been proposed such as testing resources based on computational, storage and communication challenges. The Sybil attack is a dangerous attack in a VANET environment, given the disastrous consequences it can cause. The GPS spoofing/position faking attack: In a VANET, the position information is of crucial importance, it must be accurate and authentic 32. This attack consists on providing neighbours node a false location information. The exact location information can easily be obtained from a system such as GPS, hence the name of the attack: GPS spoofing. Each vehicle of is equipped with a positioning system (receiver), then the attack can be achieved using a transmitter generating localization signals stronger than those generated by the real satellites 35.

2.3.6 Attacks on confidentiality
Confidentiality is an important security requirement for VANETs communications, it ensures that data are only read by authorized parties 34 36 In the absence of a mechanism to ensure the confidentiality of the exchanged data between nodes in a vehicular network, exchanged messages are particularly vulnerable to attacks such as the improper collection of clear information 32. The information collected in the absence of a confidentiality mechanism may affect the privacy of individuals, since it is virtually passive and user currently is not aware of the collection. In wireless networks such as VANETs, Eavesdropping attack and listening to the media is an attack easy to carry out, an attack which is against confidentiality, it is without imminent impact on the network 33. In this attack, several types of useful information can be collected such as location data that can be used for tracking vehicles. The traffic analysis attack is a passive serious threat against confidentiality and privacy of the users. The attacker analyses collected information after a phase of listening to the network, it tries to extract the maximum of useful information for its own purposes.

2.3.7 Attacks on integrity and data trust
The purpose of integrity is to ensure that exchanged data have not been altered in transit. Integrity checks helps to protect information against deletion, modification, or addition attacks. In vehicular networks, the category target mainly V2V communication when compared to V2I communication simply because of their fragility. The main technique used to carry out this attack is the manipulation of in-vehicle sensors and cameras 36. In Masquerading attack, the attacker is hidden using a valid identity (called a mask), and tries to form a Black hole or produce false messages that have the ability of coming from an authentic node. For attacks, such as replay attack, it consists in replaying (broadcast) a message already sent to take the benefit of the message at the moment of its submission. Therefore, the attacker injects it again in the network packets previously received. Replay attack can be used e.g. to replay beacons frames 35, so the attacker can manipulate the location and the nodes routing tables.

2.3.8 Attacks on non-repudiation and accountability
Non-repudiation allows the sender and receiver the abilities to verify and authenticate they have respectively sent and receive the messages. The repudiation of data origin proves the data has been sent, and non-repudiation of arrival proves that they were received. In vehicular networking, the manipulation of data related to the safety and privacy of the users of the network. Loss of events traceability: Despite its importance, we have not seen any document that addresses this attack that we find quite feasible in a VANET environment 36. In fact, this non-repudiation attacks consists of taking action, allowing subsequently an attacker to deny having made one or more actions
2.3.9 Secure and Enhancing Privacy in Vehicular Communication
In order to provide both security and a degree of anonymity, long term keys and credentials are not used to secure communication. Rather, the integration of pseudonymity or pseudonymous authentication is widely used. Every vehicle is equipped with multiple certified public keys which are known as pseudonyms, which do not reveal the node or vehicle identity. The pseudonyms are obtained via a trusted third party, a Pseudonym Provider (PNP), by proving it is registered with a CA 37. Then the vehicle uses each pseudonym and private key for at most ? seconds (the pseudonym lifetime), before it switches to another, not previously used. Periodic single-hop broadcasting, beaconing, is typically used for the so-called cooperative awareness applications: beacons, typically sent ? times per second, contain information on the sender’s status such as vehicle position, speed, and heading. The frequency of beacons is expected to range from 10 Hz to 1 Hz. Beacon messages are digitally signed, and the signer’s certificate is attached 38. More precisely, after the beacon message assembly is complete and before submitting a message m to the data link layer for transmission, the sending node (V ) calculates a signature. Privacy and anonymity are major issues that needs to be addressed. Vehicle safety communication applications broadcast messages about a vehicles current location, speed and heading. It is desirable that users have their privacy in order to prevent their full identities from being disclosed. The following are potential tracking methods that can be employed to link two locations of a vehicle.

Simple tracking: here, the advisory obtains the target vehicle’s location, speed and the time and then estimates based on possible environment directions. The reachable area denoted by Ar around lknown, in which the vehicle’s actual location l1 at a future time t1 can lie.

Correlation tracking: in correlation tracking, the adversary uses a vehicles last known location lknown, speed, and direction at time t to estimate the entity’s location lest1 at a future time t1. In correlation tracking, the adversary uses a vehicles last known location lknown, speed, and direction at time t to estimate the entity’s location lest1 at a future time t1. The estimation is repeated till the maximum silent period is reached. Note that in both the tracking methods, it is assumed that the restricted mobility of vehicles prevents them from taking certain directions. Before evaluating the anonymity under the tracking methods by simulation, we first analytically evaluate the level of anonymity that can be achieved under the simple tracking method 38. When in silent period, a vehicle must remain silent and not broadcast any message for at least 1 sec to achieve average anonymity of 2. Hence, for vehicles participating in safety applications, this solution presents a trade-off between vehicle anonymity and vehicle safety.

In general, the challenges regarding privacy in VANET proposes several interesting solutions, such as Electronic License Plates (ELPs) that are unique cryptographically verifiable numbers equivalent to traditional license plates, and location verification based on verifiable multilateration as an approach to address liability requirements of VANET. From BMW research 37, privacy problems in VANET, and security of V2I communications for safety, particularly between vehicles and traffic lights.

2.4.0 Vehicular Communication Routing Protocols
In networking, routing is the process of finding a path from a source node to a destination node. Since each node (vehicle) has a limited transmission range, messages often have to be forwarded by other nodes (RSU) in a VANET. There are two general classes of routing protocols in VANET; topology-based routing and location-based routing 39.Topology-based routing protocols use the information about the links that exists in the network to perform packet forwarding. Whereby, location-based routing is the forwarding decisions and are based on a nodes location. They can be sub-divided into proactive and reactive approaches. Topology based routing protocols use links information to transmit the packets of data between nodes through the VANET While, Proactive routing protocols are commonly depending on algorithms related to shortest route. They save all the data related to the connected nodes in predefined tables which are the main mechanism in these routing protocols. High dynamic topology characteristics turn out the efficient VANET routing protocols design to be harder. The most popular sub categories under them is Dynamic Source Routing (DSR), UMB, OLSR, TORA, GRP and Ad Hoc On Demand Distance Vector (AODV) 40.

In location-based routing, forwarding decisions are based on the location of the forwarding node in relation to the location of the source and destination nodes. In contrast to purely topological ad-hoc routing approaches, no route set-up or route maintenance is needed with location-based routing approach since packets are forwarded “on the fly” 40. Location-based routing protocols consist of location services and geographic forwarding.

Geographic forwarding takes advantage of a topological assumption that works well for wireless ad hoc networks: nodes that are physically close are likely to be close in the network topology and each node learns its own geographic position using a mechanism such as GPS, and periodically announces its presence, position, and velocity to its neighbours 41. So now each node maintains a table of its current neighbour’s identities and geographic positions. Until a node needs to forward a packet, it includes the destination nodes identity as well as its geographic position in the header of the packet. Each node along the forwarding path consults its neighbour table and forwards the packet toward the neighbour closest to the destination in terms of physical location, until the final destination is reached.

Fig 2.18 Describes the full chart of VANET routing protocols based on classification and mechanism
2.4.1 AODV
Ad Hoc on Demand Distance Vector routing protocol is a reactive protocol, which is dependent on a mechanism related to on demand approach which initiates a path when a VANET node transmits packets of data to another node. Like all reactive protocols, the philosophy in AODV, the information is only transmitted between nodes in an on demand mode. When a node wants to transmit traffic to the host node without a predefined route, it will create a (RREQ) route request message to be flooded to the other nodes in a limited way 42. Advantages include:
Any failure in the VANET links is handled in a prompt way by the AODV
Distance Sequence Number is providing recent route to the destination node
AODV can be used in large VANET networks
The route redundancy and excessive memory requirements are minimized.

The Destination Sequence Number is used by this protocol which is a unique feature not available in similar sub category routing protocols. It can be used in singular and multimode routing 42. Disadvantages include:
It expends extra bandwidth, because of proactive beaconing High control overhead is occurring when many route reply packets for a single path.

Compared to other approaches, high processing time is required for the connection initiation and the first attempt to set the path.

Route inconsistency may occurs when old entries are included in intermediate nodes
AODV uses the three control messages for route servicing, RREQ, RREP and RERR. If a route is unable to forward packet, it generates a RERR message. When the originator node receives the RERR, it then initiates a new route discovery for the given route. The figure below illustrates routing mechanism of the AODV protocol.

Fig 2.19 Illustration of the routing mechanism for AODV protocol
2.4.2 DSR
The DSR protocol utilizes source routing and maintains functional paths. It consists of route detection and route servicing. It is similar to AODV in that it forms a route on demand when transmitting node requests 43. However, it uses source routing instead of relying on the routing table at each intermediate node. It has only two phases, which are route discovery and route maintenance.
No proactive updates are desired in DSR
Compared to other approaches, extra overload is occurring on the VANET as it searches for the paths in a reactive approach
Beacon less
Cracked links can’t be reformed locally.

The performance is declining in highly dynamic VANET.

In high traffic VANET network which is an expected pattern, Byte overhead is occurring by the path data in the header
2.4.3. OLSR
It means optimized link state routing which means a routing protocol using the proactive category mode. In this, whenever any change in the topology occur, MPR (multipoint relay) are responsible to generate and forward the topology information to selected nodes 44. It is a proactive protocol based on the table-driven methodology. Since link-state routing requires the topology database to be synchronized across the network, OSPF and IS-IS perform topology flooding using a reliable algorithm. Such an algorithm is very difficult to design for ad hoc wireless networks, so OLSR doesn’t bother with reliability; it simply floods topology data often enough to make sure that the database does not remain unsynchronized for extended periods of time. From its name, the link-state scheme is used by this protocol in an enhanced way to circulate topology information. OLSR is using this mechanism also, but in order to maintain bandwidth the message overflow in OLSR is enhanced as the protocol works in wireless multi-hop scenarios 44.
Its major advantage in broadcast scenario, is that, it reduces the number of retransmission of packets. And a disadvantage is that large amount of bandwidth and CPU power is required to compute the optimal path. AS OLSR protocol based on tables, OLSR operation fundamentally consists of servicing and updating information in a set of tables. These tables are including data which is based on received control traffic, and control traffic is produced based on information returned from these tables. The tables are managing the route calculation itself as well 44.

2.4.4. GRP
Geographic routing protocol is classified as proactive routing protocol. In GRP the Global Positioning System is used to locate the location of node to collects network information at a source node with a small amount of control overheads. It is subdivided into two further techniques, which are geographic forwarding and greedy forwarding.
In Geographic Forwarding, the sender node rebroadcast the packet and this packet receives by nearer sensor node. When receiver receives the packet it also receive the time period, it will first store the packet in buffer. At the end of the transmission period and if the channel is clear, the packet at the head of the queue in the buffer will be transmitted 41.In order use the Greedy forwarding approach, the sender node determines the receiver node’s estimated location. The message is transmitted to the receiver node’s closest neighbour. Greedy forwarding algorithms perform varied optimization techniques to choose the next-hop node near a destination node 41.

Route discovery and management is not required

Suitable for high node mobility pattern
GPS device doesn’t work in tunnel because satellite signal is absent there.

It requires position determining services

3.1.0 Overview of Ilorin City Road Networks and Infrastructure for Traffic Simulation
The city of Ilorin is the state capital of Kwara in North central Nigeria, as of 2006 census, it is the 6th largest population in Nigeria, and has an Area of 765km2. Ilorin operates a relatively well-developed intra-city public transportation, and the major roads within the metropolis are very good except developing parts of the state. Ilorin’s central location makes it easily accessible to all parts of the country by air, and road. In Ilorin, There are three modes of transiting from place to place in the city, the most popular being the conventional taxis. Mass transit busses provided by the state government also provides access to limited number of places in the state. Furthermore, there are commercial motorbikes, commonly called “Okada”, and the more recent arrival on Ilorin’s roads of commercial tricycles, popularly called “Keke NAPEP”. Fig 3.0 is the map of the city.

Fig 3.0. Ilorin major road Streets map.

OpenStreetMap (OSM) is both the name of a project and the foundation supporting it, which aims to collect and provide freely available geodata, most notably geodata related to street maps. The maps will be imported to the preferred simulation software to achieve realistic traffic simulation of selected road networks in the city.

3.1.1 Overview of different simulators
As it is decided to develop the approach on a simulator, now it should be decided on which simulator it will be developed. Since it is not feasible to install RSU’s, vehicles with OBU’s and other components, it is necessary to check the performance of the network on a simulation software for vehicular networking. Here, we briefly discuss few simulation software’s and reasons for picking our preferred software. There are couple of network and traffic simulation software that are available. They are:
VanetSim3.1.2 SUMO
SUMO (Simulation of Urban MObility) 29 is an open source, highly portable, microscopic road traffic simulation package designed to handle large road networks. Its main features include collision free vehicle movement, different vehicle types, single-vehicle routing, multi-lane streets with lane changing, junction-based right-of-way rules, hierarchy of junction types, an openGL graphical user interface (GUI), and dynamic routing. However, since SUMO is a pure traffic generator, its generated traces cannot be directly used by the available network simulators, which is a serious shortcoming.

There are three mandatory files required for a SUMO simulation (configuration file, network file and routing file). The configuration file holds the path of the network and routing files. At the time of simulation SUMO only needs to know the path of the configuration file. The network file is generated by NETCONVERT from the node and edge file. Figure 23 shows the steps required to simulate road and traffic in SUMO.

Fig 3.1. SUMO simulation process.

3.1.3 MOVE
MOVE (MObility model generator for VEhicular networks) 28 rapidly generates realistic mobility models for VANET simulations. MOVE is built on top of SUMO. The output of MOVE is a mobility trace file that contains information of realistic vehicle movements which can be immediately used by popular network simulation tools such as ns-2 or GloMoSim. In addition, MOVE provides a GUI that allows the user to quickly generate realistic simulation scenarios without the hassle of writing simulation scripts as well as learning about the internal details of the simulator.

3.1.4 TraNS(Traffic and Network Simulation Environment) 17 Is a simulation environment that integrates both a mobility generator and a network simulator and it provides a tool to build realistic VANET simulations. TraNS provides a feedback between the vehicle behaviour and the mobility model. For example, when a vehicle broadcasts information reporting an accident, some of the neighbouring vehicles may slow down. TraNS is an open open-source project providing an application-centric evaluation framework for VANETs. TraNS is written in Java and C++ and works under Linux and Windows (trace-generation mode). TraNS v1.2 has several features, including: (a) support for realistic 802.11p, (b) automated generation of road networks from TIGER and Shapefile maps, (c) automated generation of random vehicle routes, (d) mobility trace generation for ns-2, SUMO and ns-2 coupling through the TraCI 19 interface, and (e) possibility to simulate road traffic events, e.g., accidents.

3.1.5 OMNeT++
OMNeT++ is introduced as a general purpose simulation engine in its website, which takes advantage of independently developed frameworks, also called packages, to support the simulation of communication networks. Aside from communication networks, OMNeT++ can also be used for modelling queuing networks, multiprocessors and distributed hardware systems and evaluating the performance of hardware and software architectures. The building blocks in OMNeT++ simulations are called simple modules. As in NS-2, these modules which form the lowest level of simulator hierarchy are written in C++. A number of simple modules can be integrated by the user to form a compound module. Subsequently, multiple simple and/or compound modules can be linked to form a model such as a protocol.

Fig 3.2. Omnet++ simulation process
3.1.6 VanetSimVANETsim is a lightweight, discrete event traffic and communications simulator that focuses on the analysis of security concepts, by modelling Inter- Vehicular Communication within a real street map based topography, it eases protocol design and in-vehicle deployment. It is developed to run on java programming language for most of its functions and entities. VanetSim modular architecture incorporates mobility, trip and message broadcast models over a variety of link and physical layer communication models. It concentrates on simulation of the application layer to reach high performance. VANETsim contains four main components: a GUI, the Scenario Creator, the Simulation Core, and the Post Processing Engine. VANETsim also allows to deploy RSUs that provide additional security mechanisms for vehicles, e. g., Pro-Mix Zones 22. Moreover, it facilitates the simulation of the effectiveness of special attacks, in which an adversary has gained control over single or multiple RSUs (Attacker Road-side-Units). Apart from exhibiting realistic behaviour on a microscopic level, the movement of vehicles is also modelled on a macroscopic level in VANETsim (navigation and vehicle routing). At its creation, each vehicle receives a list of at least two waypoints (start, destination, and, if applicable, any number of intermediate waypoints).
The waypoints are represented by their x and y coordinates on the map as well as a road identifier, which allows to differentiate between overlapping streets (e. g., due to bridges). The figure below is the architecture of VanetSim
Fig 3.3. Architecture of the VANETsim platform
3.1.7 Conclusion and preferred simulator
VanetSim has more rich simulation models than the other mentioned simulators. Considering this project, VanetSim has MIXIM simulation model for ad-hoc network, wireless sensor network, vehicular network. Based on this evaluation, VanetSim has been chosen for the development of this project due to its Simple UI, Integration of Network and Traffic Simulation, Ability to edit maps and import real city maps, Routing protocol extension and its security features.

3.1.8 Implementation of Mix Zone
The first stage in setting up the simulation environment is to download the street map for the city of Ilorin, maps are downloaded from the openstreetmap open source project. The map is saved with file exetnsion ‘osm’. The map file will be uploaded to VanetSim and on the map, traffc lights, road side units, vehicles and other configuration can be set.

The Privacy Modules of VANETsim contain ready-to-use implementations of a number of infrastructure-enabled privacy concepts. E.g. Mix Zones. All these concepts aim to provide a secure, unlinkable pseudonym switchover via radio silence or encryption. The following are the steps to enable privacy in a certain roadmap in the simulation environment.

Map Moduling: The downloaded Map is being imported into the simulator.

Fig 3.4. Map importation to simulation software
Now, the map will be created with parameters for easy navigation such as:
Width: 1,673,310 cm
Height: 2,391,233 cm
Width of region: 100,000 cm
Height of region: 100.00 cm
Selecting a road network: From the map, the Government Residential street leading towards challenge was selected, due to its flexibility and well-structured infrastructure inclusive traffic lights. It’s a double lane street with junctions at approximately every 300m.

Fig 3.5. Road network selection
Vehicles: The vehicles will be Wi-Fi enabled. That can read both location data and as well as event data and event data will have higher priority. In the vehicle configuration panel, we’ll have a total of 20 vehicles, 10 each on opposite directions. Vehicles colour, waypoints, speed and other parameters will be configured too.

RSU: It acts like Wi-Fi repeater and communication range is increased. During this simulation setup, it’s not really necessary, since the vehicles are not communicating far from each other.

Mix Zone: A mix zone is an anonymzing region that obfuscates the relation between entering and exiting vehicles. Here, each vehicle that drives into the mix zone has its pseudonym changed or let’s say a public key, so as to prevent tracking. In the simulation configuration, we deployed a mix zone in the junction of the road network. It has a coverage radius of 100m.

Fig 3.6. Vehicles leaving and approaching the mix zone from both directions of the road.
From the statistics:
Current time: 111,520ms
Active vehicles: 20
Average speed: 49.60 km/h
Average travel distance: 1,310.62 m
Average travel time: 102.52 s
WiFi vehicles: 20
Total ID changes: 20
From this, it can be deduced that all vehicles in the road network i.e. green and black vehicles all changed their ID immediately they entered the mix zone. Which brought about a total of 20 ID changes, and active vehicles remain 20 in the network.
For the first round of vehicle waypoints, it took 1.859 minutes to complete switching pseudonyms, and a reason for that short time is that all vehicles in the network travels at uniform speed.

3.1.9 Deployment of safety applications
Enabled by DSRC, these applications are the major reasons why vehicular communication is important. To begin, safety applications such as EEBL, RHCN and PCN will be deployed in the centre of the city. Deployment coordinates is 8.4799° N, 4.5418° E. Reasons why the central of the city was chosen for deploying safety applications is simply because of scenarios like Congested traffic, and practical presence of potholes. The table below is the simulation parameters that was configured.

Table 5. Simulation parameters for safety applications
Parameter Value
Total Simulation time 16min
Simulation area 3,960,82 x 3,104,233 cm
Total number of vehicles First scenario = 30 vehicles
Second scenario = 30 vehicles
Vehicles Mobility 10,20,30 ,40, 50, 60 km/h
Mobility model Selected waypoint model
IEEE 802.11 p data rate 1Mbps
Channel bandwidth 2Mbps
Packet size 512 bytes
Transmission range per hop 500m
Node processing delay 0.26s
Road Side Units 7
Number of event spot 3
Beacon interval 240ms
The programming tools are also required to perform the tasks of defining the state transition machine, vehicles mobility, defining network model, and the process module. As other network simulators, VanetSim also provides programming tools in java for users to define the packet format of the protocol. Figure 3.6 shows the map of the city center before simulation.

Fig 3.7. Ilorin city centerFrom the map, traffic lights has been set to various junctions and 7 road side unit are deployed. A total of 60 vehicles will be routed to selected waypoints in the map. These vehicles are differentiated by their colours. On each waypoint is a total of 20 vehicles which makes us have 3 waypoints in total. From the map in the figure below, Green vehicles move from point A to B, Blue vehicles will move from point C to D, and Black vehicles will move from point E to F. From the traffic and map module, road network G to H is a damaged road.

Fig 3.8. Vehicle waypoints
Next is deploying attacker vehicles, these attacker vehicles will try and attack the vehicles in the network either by fabricating the message beacon or spoofing. Along with the attacker is also mix zones.

Fig 3.9. Vehicles getting warning on damage roads.
After 16 minutes of simulation, from the reporting tab we derived the following statistics:
Current time: 1,000,000 msActive vehicles: 52
Average speed: 50.14 km/h
Average travel distance: 1,293.27 m
Average travel time: 93.64 s
WiFi vehicles: 52
Average known vehicles: 3.79
PCN: 97
EVA: 448
RHCN: 1,461
Throughput: 1,240 Kbps
PDR: 99%
Latency: 104 msEEBL: 25
Failed forward messages: 2
Total ID changes: 448
3.2.0 Variable speed limit implementation
Exceeding speed limit is a criminal offense in majority of the developed countries. In this project, Road side units were deployed to broadcast speed limit to vehicles under certain environmental conditions such as general scenario, raining, and accident scenario. When a RSU broadcast as new speed limit, all vehicles in range receive the speed limit and react on it. Based on the number of vehicles in range, the RSU sets a new speed limit and broadcasts it to the vehicles. Below is the code snippet for Road side unit and vehicle to handle the scenario.

Figure 3.9 illustrate the communication in a sequence diagram. At the beginning the Roadside Unit transmits the legal speed limit.
Then, based on the scenario and traffic congestion the RSU calculates the new speed limit and broadcasts it to approaching vehicles. This is a continuous process which runs every 3 seconds. For the simulation purpose, it runs on every 3 seconds so that when the simulation starts communication between roadside unit and vehicles are well understandable.

Fig 3.10. Sequence diagram of communication
Road network for general scenario:
Figure 3.2.0 shows the road network for the general scenario. The network has a straight road with two directions. Each direction has a single lane. There are two types of vehicles running in the road. In each direction a total of 90 vehicles of the same type are moving. The maximum speed is set to 100km/h.

Fig 3.11 Part of the general road scenario
Road Network for Raining Scenario:
Figure 3.2.1 shows the road network used by the icy scenario. This is a curvy road in direction to the bottom. The road network on the above diagram is used for the raining road condition. The other parameters like vehicle flow and speed, number of vehicles are the same as with the general road network.

Fig 3.12 Part of raining road scenario
Road network for accident scenario:
Figure 3.13 shows an accident scenario road network. This road is also a curvy road like in the raining scenario, except that the curve is going in top direction. The other parameters like vehicle flow and speed, number of vehicles are the same as with the general road network.

Fig 3.13 Part of the accident road scenario
3.2.1 Scenario integration in VanetSimThe road networks mentioned in section 3.2.0 are integrated as different scenarios in the main VanetSim project. Scenarios are configured in the ini file. When the simulation starts, a dialog box appears and asks the user to choose a scenario. In the general scenario, the maximum lane speed is set to 100km/h as well as the maximum vehicle speed. When RSU broadcasts the initial speed limit, the first RSU 1 broadcasts a speed limit of 60km/h for both directions and the second RSU 2 broadcasts a speed limit of 90km/h for both directions. The initial speed limit is set to ini file.
For the raining scenario, the maximum lane speed and the maximum vehicle speed are set as general scenario. But, the vehicle speed is set to 40km/h by the first RSU 1 and 90km/h by the second RSU 2.

As well as for accident event, the maximum lane speed and the maximum vehicle speed is the same as with general scenario. Assuming there is an accident on the reverse direction, initial vehicle speed is set to 90km/h (normal direction), 40km/h (reverse direction) by first RSU 1. The second RSU 2 sets the vehicle speed limit to 90km/h taking into the consideration that vehicles crossed the accident area.

3.2.2 Scenario Simulation
After implementation and integration of scenarios, it is necessary to simulate the scenarios on VanetSim. For each scenario, there are two RSUs. The first RSU 1 is placed on the top right and other RSU 2 is placed on the bottom left. Each RSU is broadcasting its speed limit on every 3 seconds. Each RSU transmits messages to vehicles of both directions. When the vehicles receive the speed limit, they react immediately.

3.2.3 General scenario simulation
Figure 3.14 shows the VanetSim simulation of the general scenario. As described in section the scenario has a straight road. So, the vehicles are driving straight in both directions, vehicles in green moving to the left, and vehicle in blue moving to the right. The black dots shows the positions of the RSU’s to the vehicles in its range. In both directions both RSU0 and RSU1 broadcast the legal speed limit. The RSU’s all have a radius of 500m.

Fig 3.14 General scenario simulation road network
3.2.4 Raining scenario simulation
Figure 3.15 shows the simulation of the raining scenario. As the scenario has a curve road on the lower direction, the vehicles are driving in the defined directions. At a certain time RSU1 broadcasts the message to the vehicles which is shown with the brown tiny lines. As described in section, the raining road area lies between RSU0 and RSU1. For this, RSU1 broadcast the new calculated speed limit for the normal direction vehicle. RSU0 does the same for reverse direction vehicles. Both RSU0 and RSU1 broadcast the legal speed limit based on the traffic congestion, and driving condition on a wet road for the other direction.

Fig 3.15 Rain scenario simulation
3.2.5 Accident Scenario Simulation
Like with the previous two simulations, Figure 3.16 shows the simulation behaviour of the accident scenario. The indication of an accident in the road is shown by a hazard symbol in the middle of the road. RSU0 broadcasts the speed limit by considering the accident ahead. As the accident area is in the reverse direction, only RSU0 broadcast the new calculated speed limit for the reverse direction.

Fig 3.16 Accident simulation
3.2.6 Expected results
The expected results of the simulation can be divided into several parts as follows:
After crossing the special area of the road (e.g., wet road surface, accident area) the corresponding vehicle should get the normal speed limit based on the traffic congestion only.

As a beacon is sent every 3 seconds, the vehicle counter (used for traffic congestion) should be reset every 3 seconds.
The main expectation is that the vehicle speed should be decreased if the number of vehicles increases in the roadside unit range. That means the vehicles should drive slowly. Vice versa, if vehicle density decreases, then the vehicle speed should be increased and the vehicles should drive faster.

The distance between vehicles should not be uniform.

The resulting analysis of the three different scenarios (general, wet and accident) shows that the simulation results conform to the expected results except the uniform distance between the vehicles. The vehicles in each scenario slow down when the traffic congestion is increased. Approaching the incident area, vehicles drive slowly and after leaving the area vehicles drives faster. Traffic congestion has been taken into account in both cases. For most of the cases the distance between two vehicles is the same as the distance between two other vehicles. For all three scenarios when the vehicles receive the new calculated speed limit, the application immediately slows down the car to the received speed. The maximum speed limit is set to 100 km/h. All the three scenarios received a new calculated speed limit every 3 seconds. For simulation the repetition of the broadcast by the roadside unit was set to 3 seconds.

3.2.7 Routing protocol survey for V2V implementation
For choosing the VANET routing protocol phase for V2V communication, nodes are randomly deployed in 9,000 × 1,000 m Area. Different nodes communicate via radio signals having a transmission range of 500 m. Channel bandwidth taken is 2 Mbps. Vehicles are allowed to move randomly with different speed. Four routing protocols examined are AODV, DSR, GRP, and OLSR. Simulation Parameters used in the simulation shown in the Table below:
Table 6. Simulation parameters for routing protocols
Parameter Value
Total simulation time 5 min
Simulation area 9000 x 1000m
Routing protocol AODV, DSR, GRP and OLSR
Vehicles Mobility Random waypoint model
Total number of vehicles 20
Data rate 1Mbps
Packet size 1,2,3,4,5,6 Kbytes (KB)
Total number of vehicles 20
Channel bandwidth 2Mbps
Transmission range 500m
4.0 Result and Discussion
This chapter emphasized and discussed the simulation results and analysis of each of simulation carried out. Each category or section of simulation activities are interpreted below.

4.1 Evaluation on Mix Zones
In section 3.1.8 during implementation of mix zones, the result of the simulation is evaluated as follow:
From the statistics:
Simulation time: 111,520ms
Active vehicles: 20
Average speed: 49.60 km/h
Average travel distance: 1,310.62 m
Average travel time: 102.52 s
WiFi vehicles: 20
Total ID changes: 20
From this, it can be deduced that all vehicles in the road network i.e. green and black vehicles all changed their ID immediately they entered the mix zone. Which brought about a total of 20 ID changes, and active vehicles remain 20 in the network. Average total distance from the simulation tab is 1.3km. For the first round of vehicle waypoints, it took 1.859 minutes to complete switching pseudonyms, and a reason for that short time is that all vehicles in the network travels at uniform speed. The table below interprets the pseudonym key changes for the first five vehicles for each vehicle type/colour.
Table 7: Detailed Pseudonyms change
Vehicle Type/Colour Initial ID New ID
Black bb1ad57319b89cd8 149546c2d4a214dc
Black 352cccfc0946b8f0 Be45c71047b85a70
Black f7be9d4b5f3o868k 7b528bf6134c9d4f
Black f27b5db0e9340cfc 93bcd7014d65be2a
Black Cd1f00a2e6cf481d
Green f10d13aada2a9684 262c10f162b9b174
Green f4f16d7c362f18b2 24ccfea5dcf2ff4f
Green baf7004b18f6b7e 57e79cf3e7c0cd1b
Green f3b65a055854b1b 2b911c637baddfc8
Green f26ac284bff605b 6aad47b1fe67554e
4.2 Evaluation of Safety Applications
After 16 minutes of simulation, from the reporting tab we derived the following statistics:
Current time: 1,000,000 msActive vehicles: 52
Average speed: 50.14 km/h
Average travel distance: 1,293.27 m
Average travel time: 93.64 s
WiFi vehicles: 52
Average known vehicles: 3.79
PCN: 97
EVA: 0
RHCN: 1,461
Throughput: 1,140 Kbps
PDR: 99%
Latency: 104 msEEBL: 25
Failed forward messages: 2
Total ID changes: 448
From the simulation, each vehicle is going to communicate with each other and vehicles approaching the damaged road (Waypoint G-F) are been alerted, so the vehicle get slow due to the RHCN notification that was received. Each vehicle relays the information to the other vehicles behind them. Now because there is too much road damages in waypoint (G-F), some vehicles are avoiding the road and taking a different route. Addition of mix zone as security and privacy mechanism has brought a total of 448 changed ID’s, So basically for a new vehicle that joins the network or topology, once it gets close to the damaged roadmap, the vehicle will be alerted which allows the driver to make decisions either to take another route or navigate through the damaged road. Therefore, a total of 1,461 RHCN safety and warning messages were disseminated in 16 minutes of simulation time. However, due to the increasing number of vehicles in the network, the channel access (Throughput) was plotted against the increasing number of vehicles in the network.

Fig 4.0 Number of vehicles vs. throughput
The post-crash notification application collision messages that was disseminated in the network is 97. Emergency electronic light break safety messages amounts to 25, all these figures shows little or no casualty in the roadmaps during vehicle navigation. Again, packet delivery ratio in the network is 99%, which means almost all packets and messages were delivered at the right time, and there were little packet loses. In conclusion, from the simulation and deployment of safety applications, it can be said that high safety will be achieved if there’s low latency and high throughput in the network.

4.3 Evaluation of variable speed limit
A. Speed limit for general scenario.

Table 8. Speed limit for general scenario
(no. of cars in transmission range) Normal direction speed limit (km/h) Reverse direction speed limit (km/h)
<=2 100 100 100 100
<=4 80 80 80 80
<=6 60 60 60 60
<=8 50 50 50 50
<=10 50 50 50 50
>10 40 40 40 40
From section 3.2.0, all the results are logged in a file after successful simulation. Generated result files (graph view) are described for each scenario in details. From each scenario only one vehicle is taken into account for the result analysis. The results are logged in both vector and scalar file. Vector result file describes the result in details considering the time frame. But, the scalar result file contains generic information (e.g. average distance covered by the vehicles, maximum speed in the whole journey, etc.

B. Evaluation of general scenario
Figure 4.1 illustrates the behaviour of a vehicle (vector analysis) on the road network in a graph

Fig 4.1. General result evaluation
As the maximum speed limit of vehicle and lane is set to 100km/h on the roadmap, the vehicle goes up to 100km/h before receiving any messages from the road side unit. Now Around 8 seconds the vehicle gets the legal speed limit of 100km/h from the RSU1 which is the same as the vehicle speed. Until 13.5 seconds the vehicle receives the same speed limit of 100km/h. At 13.5 seconds the vehicle receives a new speed limit of 80km/h from RSU1 based on the traffic congestion and applies the speed to the vehicle which starts driving slowly which is the same as the expected behaviour that vehicle speed is inversely proportional to traffic congestion. Until 19.5 seconds it receives the same speed limit of 80km/h. At 19.5 seconds it receives the new speed limit of 100km/h and increases the vehicle speed to 100km/h. The vehicle got the new speed limit on every 3 seconds as well as advised speed limit matched with the congestion-speed. The analysis indicates that simulation results conform to the expected results except the uniform distance between vehicles.

C. Evaluation of raining scenario
Table 9. Speed limit wet scenario
(no. of cars in transmission range) Normal direction speed limit(km/h) Reverse direction speed limit (km/h)
100 60 60 100
<=4 80 55 55 80
<=6 60 50 50 60
<=8 50 45 45 50
<=10 50 45 45 50
>10 40 40 40 40

Fig 4.2. Wet/raining scenario result evaluation in normal direction
It is assumed that the wet road is situated in between RSU0 and RSU1 in both directions. Figure 4.2 depicts the behaviour of a vehicle (vector analysis) which has started its journey in the normal direction. Like in the previous scenario, initially the vehicle goes to the max speed limit before receiving any speed limit message from the roadside unit. Around 10.5 seconds the vehicle receives an initial speed limit of 60km/h by RSU0, and slows down to the received speed limit. Around 16.5 seconds, based on the traffic congestion vehicle receives a different speed limit of 55km/h from the RSU0 and applies the received speed to the vehicle. As traffic congestion increases in the wet road area, it further slows down its speed to the advised speed, which implies that increase of traffic congestion results to drive slowly and hence satisfies the main expected result. Around 26 seconds the vehicle receives a new different speed limit of 100km/h from RSU1 and increases speed to 100km/h. At around 26 seconds the vehicle passed the wet road surface area and reached the range of RSU1, it receives the normal speed limit based on the congestion only. This result satisfies the expected behaviour of the reception of new speed limit after passing the special road area.

D. Evaluation of accident scenario
As explained before, it is assumed that the accident happens in the reverse direction of the road network between RSU0 and RSU1 which causes the partial blocking of the road. As with the other simulation scenarios at the beginning the vehicle goes to maximum speed of 100km/h. Around 8.5 seconds it gets the new speed limit of 55km/h because of the accident ahead which causes partial blocking of the road. At around 20 seconds the vehicle gets the new calculated speed limit of 50km/h based on the number of vehicles in the range of RSU0. The vehicle applies the new received speed limit and slows down to 50km/h. When a vehicle passes the accident area at around 29 seconds it receives a new speed limit of 100km/h.

From RSU1 and increases the speed to 100km/h. The simulation results comply with the expected behaviour. The minimum speed for a vehicle in both icy and accident scenario is almost the same. Additionally, the maximum speed is also the same in these two scenarios. For this reason, the scalar analysis is not shown for icy and accident scenario. Figure 4.3 shows the behaviour of a vehicle (vector analysis) which is running in the same direction where the accident occurred.

Fig 4.3. Accident scenario result evaluation
4.4 Simulation result for routing protocol
In this section, the performance of four different routing protocols was analysed, which are: OLSR, DSR, GRP and AODV for TCP traffic connections. Different size of packet size was analysed as performance parameter. In this analysis, the following measure parameters are considered: Packet Delivery Ratio, Average End to End Delay, and Average Throughput with respect to speed or different packet size.

Packet Delivery Ratio
In this scenario, routing protocols was examined over TCP traffic connection for the measured Parameter Packet Delivery Ratio versus speed as shown in the figure below. The results show that DSR and OLSR are more stable over different speeds compared to AODV and GRP routing protocols. It can be observed that for speed of 20 km/h the Packet Delivery Ratio of GRP is around 99.55 and it is around 99.8 for AODV. However, for speed of 30 km/h the Packet Delivery Ratio of GRP is around 99.95 and it is 99.85 for AODV.

Figure 4.4: Packet delivery ratio versus speed for TCP traffic connection
Packet delivery ratio with packet sizes.

Figure 4.5 below shows better results for DSR protocol than the other three protocols. AODV, GRP and OLSR show a decrease in the percentage of Packet Delivery Ratio when packet sizes increase. When using TCP traffic connection, the performance of DSR is around 99.9% while the other protocols have a lower Packet Delivery Ratio percentile.

Figure 4.5 Packet delivery ratio versus different packet size for TCP traffic connection
Average end to end delay:
Over different speeds of nodes, Figure 4.6 shows that AODV, GRP and DSR are more stable. They have acceptable delays (less than 300 ms) than OLSR protocol over the TCP traffic connection. Below figure is the average TCP connection.

Figure 4.6. Average end to end delay versus speed for TCP traffic connection
Average throughput
The figure below shows that DSR and GRP routing protocols have a constant average throughput with different speed values. Thus, their overall performance is the same with TCP traffic metrics. The figure shows an average throughput around 680 Kbps for DSR and GRP. However, OLSR shows a drop off the average throughput from 680 to 500 Kbps at around speed of 30 km/h. AODV shows a drop off the Average Throughput from 680 to 600 kbps at speed of 30 km/h.

Figure 4.7. Average throughput versus speed for TCP traffic connection
In the simulation, it was observed that DSR is more stable than the other three protocols for the measured parameter; Packet Delivery Ratio. In Average End to End Delay, DSR presents the best performance among the four routing protocols as it has the minimum delay. Finally DSR and GRP are more stable than OLSR and AODV for the measured parameter Average Throughput.
Therefore, it is recommended that DSR is suitable for communications in VANET based on the simulation results. It achieves the best performance for the three measured parameters; Packet Delivery Ratio, Average End to End Delay and Average Throughput.

5.0 Summary
The incorporation of computing, telematics, telecommunications (fixed and mobile), and various kinds of services are facilitating the deployment of different types of VANET technologies In carrying out this project, an attempt has been made on how connected vehicle technology or vehicular communication can help save lives and property on the roads. The efficient use of wireless technology, GPS, Sensors and other technology and devices coupled in the vehicle and roadsides can help the transportation sector and provide quality of services to users of the road networks at large. Increased safety, efficiency and fewer traffic jams are achieved through the implementation of cooperatives systems for communication of infrastructures, with motor vehicles and road users.

5.1 Conclusion
The main objectives of vehicular communication was accomplished through the deployment of certain safety applications. Applications such as Post crash notification (PCN), Road hazard control notification (RHCN), and Emergency electronic brake lights (EEBL) were deployed in the simulation environment. Certain roadmap topology was used for traffic simulation to achieve realistic mobility of vehicles. The result of the deployment from the simulation shows a high level of safety, and easy routing of nodes to alternative routes whenever there is a traffic jam or bad roads. Also location privacy of vehicles was achieved through the implementation of mix zones.

Analysis and the performance of DSR, AODV, GRP and OLSR routing protocols using TCP connections was also examined. The speed and packet size was considered as the controlled parameters in the experiments. DSR was selected as the best routing protocol based on the simulation result.

5.2 Recommendation
The importance and effectiveness of VANET in most travelling roads is a difficult task as vehicles and nodes are far apart with non-uniform speeds, which can degrade the quality and propagation of signals. Another factor is the implementation of safety technology in trucks and big vehicles which will make the network differentiated. So a platform can be setup to install the technology on existing vehicles, and roads. Also, to reduce cost and increase efficiency in the network, mobile base transceiver stations could be overlayed and integrated to allow access to the technology by installing necessary VANET sensors and Antennas on them.
Future research and works by academic scholars, bodies and individuals can help propel and solve the issues relating to the deployment and maintance of the technology most especially in travelling roads where most accidents are being recorded.

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