Realistic and Efficient Radio Propagation Model for V2X Communications

2013 KSII Transactions on Internet and Information Systems  
Multiple wireless devices are being widely deployed in Intelligent Transportation System (ITS) services on the road to establish end-to-end connection between vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) networks. Vehicular ad hoc networks (VANETs) play an important role in supporting V2V and V2I communications (also called V2X communications) in a variety of urban environments with distinct topological characteristics. In fact, obstacles such as big buildings, moving vehicles,
more » ... , moving vehicles, trees, advertisement boards, traffic lights, etc. may block the radio signals in V2X communications. Their impact has been neglected in VANET research. In this paper, we present a realistic and efficient radio propagation model to handle different sizes of static and moving obstacles for V2X communications. In the proposed model, buildings and large moving vehicles are modeled as static and moving obstacles, and taken into account their impact on the packet reception rate, Line-of-sight (LOS) obstruction, and received signal power. We use unsymmetrical city map which has many dead-end roads and open faces. Each dead-end road and open faces are joined to the nearest edge making a polygon to model realistic obstacles. The simulation results of proposed model demonstrates better performance compared to some existing models, that shows proposed model can reflect more realistic simulation environments. 1934 Khokhar et al.: Realistic and Efficient Radio Propagation Model to Handle Obstacles for Vehicle-to-X Communications Introduction Vehicular Ad hoc NETworks (VANETs) are emerging as a new promising field of wireless technology, which aims to deploy V2V and V2I communications (alco called V2X) for different applications such as roadway safety, dynamic routing planning, mobile sensing, incar entertainment, and even Internet access [1] . VANETs provide true ubiquitous communication networks with great features such as self configuration, infrastructureless, and rapidly deployable networks. Because of such promising applications and features, the automotive industry and the international standard organizations are paying special attention to VANETs research for obstacles handling [2, 3], security [4], routing protocols [5, 6, 7, 8, 9] , and mobility models [10] . But, in this paper we only focus on obstacles handling that is particularly challenging because the radio signals of high speed vehicles are obstructed by different static and moving obstacles. The antenna used in these vehicles have limited communication range and the signal may be weakened by these obstacles. Most widely used stochastic radio propagation models (e.g., Free Space [11], Two-RayGround Reflection [11], Rayleigh Fading model [12], Ricean Fading model [13], Shadowing model [14], Log-distance Path Loss [11], mix ones [15, 16, 17] ) rely on the overall statistical properties of the environment. Free Space model is not consider obstacles in city environments and the received signal power is based on three factors: the sender and receiver distance, antenna gains, and the transmitted power. Two-Ray Ground model demonstrates better performance than the Free Space model. Received signal strength can be predicted from long distance. However, two-ray is not concerned with the height and width of the nodes. It only assumes the received energy, which is the sum of direct LOS path and reflected path from the ground. In fact, there are different sizes of vehicles (i.e., cars, trucks, buses, and vans) on the roads. In Rayleigh Fading model, the indirect path between the transmitter and receiver nodes are taken into account in the Rayleigh model. Rayleigh Fading model is only suitable for wireless channels that have no LOS component. However multipath components may vary in amplitude and phase. The random multipath components are added to the LOS and can be seen as a Direct Current (DC) component in the random multipath in Rayleigh distribution. Similarly, the Ricean model only focuses on a single exact path and multiple reflected signals. Rayleigh and Ricean Fading are considering fast fading and caused by scattering while slow fading follows log-normal shadowing and occurs due to reflections of hill, building and obstacle. Similarly, in Shadowing model, the radio signals are set to some particular values, which make it not suitable for real urban environments. In general, these models are unable to provide satisfactory accuracy for distinctive urban vehicular environments as they do not consider any obstacle. Recent VANET research [2, 3] have confirmed that large moving vehicles also significantly affect vehicle-2-X communication in urban environments. The LOS between two communicating vehicles (cars) runs a high risk of interruption due to the presence of large vehicles such as buses and trucks. To develop a realistic radio propagation model for highly dynamic VANET is computationally challenging, and moving obstacles makes them more complicated. Cheng et al. [18] performed a narrow-band measurements of moving V2V radio propagation channel using 5.9 GHz frequency band. In this experiment, the authors used slope piecewise linear channel model and observed that large moving vehicles are the major cause of reduction in received signal power. The geometry-based stochastic models [19, 20, 21] are derived from a predefined stochastic distribution of effective scatterers by applying the fundamental laws of wave propagation. Such models can be easily adapted to different scenarios by changing the shape of the scattering region. However,
doi:10.3837/tiis.2013.08.011 fatcat:xucj26ag2nbp3nc3vuiluyik4i