**3. Wireless technologies for vehicular networks**

To support vehicle to vehicle (V2V) or vehicle to infrastructure (V2I) communication in adhoc and dynamic environments wireless technologies such as WiFi, WiMAX, 3G, ZigBee and Bluetooth among others, are available (Jain et al., 2009). All these technologies feature important differences in terms of transmission range, transfer data rate, geographical area of coverage, supported content types, etc. In a VANET environment different subsets of this type of technologies can be present at a same time and place; therefore, support for heterogeneous wireless technologies is important. For example, a tracking application may require GPRS connectivity, intersection collision avoidance may require of DSRC communication and text message application may require Bluetooth. The main features of these technologies are described as follows.

#### **3.1 WiFi (802.11p)**

The IEEE 802.11p protocol is also known as Wireless Access in Vehicular Environment (WAVE). This protocol was specifically designed operate in V2V and V2I settings, and

misbehaving or faulty nodes in the vehicular networks. Several works in the literature study this issue. For instance, in (Golle et al., 2004) authors proposed a heuristic approach, which consists in finding the best explanation for corrupted data. In reference (Xiao et al., 2006) authors proposed an approach to detect attacks based on radio signal strength analysis and use the idea that a vehicle cannot be on different places at the same time. In (Raya et al., 2007) authors proposed an approach that uses the Tamper Proof Devices (TPD) and assumed the existence of a honest majority on the attacker's neighborhood. TPD are used to

execute their protocol and revoke themselves if they detect that have been tampered.

two group signatures generated by a node cannot be linked (Calandriello et al.*,* 2007).

To support vehicle to vehicle (V2V) or vehicle to infrastructure (V2I) communication in adhoc and dynamic environments wireless technologies such as WiFi, WiMAX, 3G, ZigBee and Bluetooth among others, are available (Jain et al., 2009). All these technologies feature important differences in terms of transmission range, transfer data rate, geographical area of coverage, supported content types, etc. In a VANET environment different subsets of this type of technologies can be present at a same time and place; therefore, support for heterogeneous wireless technologies is important. For example, a tracking application may require GPRS connectivity, intersection collision avoidance may require of DSRC communication and text message application may require Bluetooth. The main features of

The IEEE 802.11p protocol is also known as Wireless Access in Vehicular Environment (WAVE). This protocol was specifically designed operate in V2V and V2I settings, and

**3. Wireless technologies for vehicular networks** 

these technologies are described as follows.

**3.1 WiFi (802.11p)** 

Vehicular networks require a mechanism to help authenticate messages, identify valid vehicles, and remove malevolent vehicles. Reference (Kargl et al.*, 2006)* explains that authentication ensures that a message is trustable by correctly identifying the sender of the message. With an ID authentication, the receiver is able to verify a unique ID of the sender. The ID could be the license plate or chassis number of the vehicle. In other cases receivers are not interested in the actual identity of nodes. They are satised if they are able to verify that the sender has a certain property. Property authentication is a security requirement that allows verifying properties of the sender, e.g. the sender is a car, a traffic sign. For applications using location information, location authentication allows verifying that the sender is actually at the claimed position, or that the message location statement is valid. Some protocols have been proposed for safety messages in vehicular networks. On the one hand, some of these protocols rely on the concept of pseudonymous authentication, also known as *Baseline Pseudonym* (BP). In this kind of protocols each vehicle generates its own pseudonyms, in order to eliminate the need of pre-loading, storing and relling pseudonyms and the corresponding private keys. In this way, the burden of key and pseudonym management is greatly reduced. Other protocols are based on *Group Signatures* (GS) for V2V communication (Lin et al., 2007). GS is more robust than pseudonymous authentication, as any

**2.4.3 Message authentication** 

makes use of spectrum band and channels allocated to the *Dedicated Short Range Communications* (DSRC) by the U.S. *Federal Communication Commission* (FCC) in 1999. The DSRC radio uses a 75 MHz spectrum at 5.9 GHz (Figure 2). The main aim of this standard is to provide support public safety applications that can save lives and improve traffic flow. The DSRC band is a free spectrum and is licensed by the FCC. The license regulates its usage and the technologies that make us of it, this is, all radio manufacturers, must fulfil FCC regulations (Jiang & Delgrossi, 2008). The DSRC band offers 7 licensed channels with a transmission range of up to 1000 meters and a transmission data rate between 6 to 27 Mbps, supporting speeds of up to 200 Km/h. The Department of Transportation of the United States and the automotive industry are strongly supporting the development of DSRC devices (i.e. on board units and road side units) and applications (Jiang et al., 2006).


Fig. 2. Available channels for DSRC.
