This chapter describes different propagation scenarios in V2V communications based on practical Intelligent Transportation System applications. The intention is the study of propagation impairments for modeling purposes. It is important to consider the environmental characteristics of the scenario in order to choose the proper model to evaluate performance. The intention of this chapter is to explore how well current models fit the scenarios and to identify areas of opportunity for new model design. Many devices including sensors, transponders, and communication radios of different kinds co-exist in a typical urban scene. Interference among these devices and electromagnetic coupling with external waves is possible. Therefore, integration of the various technologies is imperative, and conditions for physical interaction of the radio waves needs to be provided. This is critical for the correct function of automatic systems that control safety sensible information. Very strict standard electromagnetic compatibility restrictions and regulations are applied to vehicles. These emissions and immunity tests need to be reengineered in the near future in order to consider new radio devices for communication among vehicles through sensors and transponders.
TopIntroduction
Car accidents represent a high cost in infrastructure, money, time, etc., but more important human lives. This situation grows in urban scenarios where thousands or millions of persons need, depending of their activities, to drive a vehicle several times during the day. During a trip, a lot of events could provoke a car accident: small distance between cars, crowded roads, mechanical failures, pavement conditions, weather, skills and concentration of the drivers, etc. The main idea behind Intelligent Transportation Systems (ITS) is to provide a safer environment for the drivers (also pedestrian, infrastructure, etc.) and help them to avoid collisions and accidents. But, to develop applications and inter-networking technologies for ITS face several issues: the travel scenario is continually changing; vehicles are moving at different speeds and directions; there are wave propagation limitations, etc. Additionally, a good communication channel is needed to support vehicle interaction.
Nowadays Vehicular Ad-Hoc Networks (VANET´s) deal with the mobility characteristics of vehicles treating them as nodes of a network. The set of VANET´s forms a reconfigurable network because one vehicle can join or leave the network depending on how far it is from the other members. VANET´s present opportunities to develop a variety of communication-based automotive applications that demand the characterization of different models for vehicle channel wireless communication.
The challenges:
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To provide efficient Hybrid Communications between V2V communication and Vehicle to infrastructure communication.
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To analyze different scenarios, like crash security modules and low bridge road crosses.
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To find the relationship between Bit Error Rate (BER) and Signal to noise ratio (SNR).
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To define the access mode usual Frames for vehicular communication.
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To get a simulation for different modulation schemes.
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To investigate about electromagnetic fields’ propagation, channel models and antenna configurations within the specific ITS scenarios.
In this chapter, we will focus primarily on three aspects. Initially, we will describe different scenarios in vehicle-to-vehicle communication (V2V) for high added value applications. These scenarios are subject to propagation impairments such as reflection, diffraction, Doppler Effect, among others. These impairments are partially mitigated by modulation and coding techniques. Therefore, different configurations need to be considered and compared, for instance, antenna diversity MIMO (Multiple Input Multiple Output) vs. SISO (Single Input Single Output). For these particular scenarios we will explore the most recent published work dealing with models built to measure performance. Finally, we will identify for the set of described scenarios opportunity areas in the channel models proposed in the literature.
TopBackground
Electronic devices and solutions considered to be part of what is called ITS scenarios are currently being developed for Dedicated Short Range Communication (DSRC technology). They support Vehicle to Vehicle and Vehicle to Infrastructure Communication where many applications have been identified for safety, security and commercial orientations. Frequency bands had already been allocated for these technologies and services. The US Federal Communication Commission (FCC) in 1999 allocated 75 MHz of bandwidth of the 5.9 GHz band to DSRC, according to the Institute of Electrical and Electronics Engineers (IEEE) 802.11p standard meant to operate in the 5.85 – 5.925 GHz frequency band supporting high vehicular speeds, while the IEEE 802.11a standard addresses low mobility in door wireless local area networks (WLAN) systems. In coordination with Europe and Japan the FCC has active programs based on DSRC in the 5.8 GHz band. In Japan, a standard for vehicle to infrastructure (V2I) communication was published in 2001, based on time division multiple access (TDMA), and targets a range of about 30m. The primary use is in electronic toll collection and more than 20 million on-board units were deployed with this system by 2008.
In (Popescu-Zeletin, 2010) some unfortunate traffic events are described which could have been prevented by using ITS technology. These are the result of situations described above. Some of the scenarios are hereby summarized: