## 1 Introduction  
Intelligent transport system (ITS) is an emerging type of information and communication technology (ICT) application, which is based on inter-vehicular communication (IVC). IVC enabled vehicles provide updated information regarding traffic conditions. ITS can be used to minimize road accidents, congestion, and improve traffic efficiency. ITS plays an important role in the economy of a country by reducing fuel consumption and efficient time management of individuals [1, 2]. Intelligent transport system stations (ITS-Ss) with the arrangement of wireless communication is a new growing area of research to reduce road accidents, congestion, and improve traffic efficiency [3]. Vehicular ad hoc network (VANET) is an important component of ITS. VANET uses ITS mechanisms to provide reliable information about vehicle's location, speed, heading, and road conditions. Increase in population and lack of seriousness in driving results in traffic congestions, road accidents and unnecessary delays in traveling [4]. Figure 1 shows one of the scenarios of un-seriousness in driving. For the betterment of society, there should be a positive use of technology in transport systems to reduce congestion, accidents, and unnecessary delays in traveling. In order to provide the best services to humanity, ITS is introduced to avoid congestion, traffic jams, and accidents, and to improve traffic efficiency [5]. ITS has a wide range of applications [6]. However, generally, ITS applications are classified into advanced driver assistance systems (ADAS), advanced traveler information systems (ATIS), and advanced traffic management systems (ATMS) [7]. ADAS, ATIS, and ATMS help ITS-Ss to communicate with each other, in order to provide road safety, traffic efficiency, and comfort as shown in Figure 2. ADAS applications include cooperative collision warning, slow vehicle indications, lane change messages, speed control, reverse parking assistance, and intersection collision warnings. Similarly, ATIS applications include public transport information, trip reservation, route planning, internet booking, local electronic commerce, and trip matching services. While ATMS applications include dynamic route information, dynamic lane assignment, hazardous location, deterioration detection, and incident detection. The most important component of ITS dissemination formation is ITS-S, as depicted in Figure 3. ITS-S consists of vehicles, road side units (RSUs) and servers. There is an on-board unit (OBU) in each ITS-S (vehicle). The OBU enables an ITS-S (vehicle) to communicate with other ITS-Ss (vehicles or RSUs). According to the European Telecommunication Standards Institute (ETSI) [8] ITS-S architecture as shown in Figure 4, consists of facilities layer, networking and transport layer and the access layer. ITS-S facilities layer resemble application, presentation, and session layers of the OSI model. Similarly, ITS-S networking and transport layers show a resemblance of transport and network layers of the OSI  
Figure 1: Scenario without intelligent transport system. Figure 2: Intelligent transport system scenario. model. ITS-S access layer provides the capabilities of data link and physical layers of the OSI model with improvement to ITS. To enable vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) wireless communication (known as 'V2X'), dedicated short range communication (DSRC) is used [9]. DSRC provides communication range from 100 to 1000 m, with the data communication rate of around 27 Mbps [10]. DSRC is known as wireless access in vehicular environment (WAVE), also called IEEE 802.11P standard [11; 12; 13]. DSRC requires low latency and high data rate to support short distance communication [14]. In ITS, DSRC is based on the access layer as discussed in IEEE 802.11P standard. Spectrum allocation for DSRC is from 5.85 GHz to 5.925 GHz as specified by United States (US) Federal Communication Commission (FCC) and European Electronic Communications Committee (ECC).