## 3 ITS Standards and Projects
### ITS Key Enabling Standards  
In order to address the increasing demand for intelligent transport system applications, the IEEE 802.11p task group [8] was formed in 2004 to provide amendments and enhancements to the IEEE 802.11 standard for the support of Wireless Access in Vehicular Environments (WAVE). The resulting IEEE 802.11p standard was published in 2010 (Draft v11) [8] and allows the use of the licensed ITS band  
Figure 6: Key technologies enabling autonomous cars. of 5.9 GHz to enable V2V communications between highly mobile vehicles and V2I communications between vehicles and RSUs. It should be noted that the IEEE 802.11p standard defines only the specifications for the basic physical (PHY) and medium access control (MAC) layers, as shown in Table 2.  
The IEEE 802.11p PHY layer is based on the orthogonal frequency division multiplexing (OFDM) schema with a channel bandwidth of 10 MHz, the support for various data rates (from 3 to 27 Mbps) and a maximal communication range of 1 km. The IEEE 802.11p MAC layer is based on an enhanced distributed coordination function (DCF) algorithm that is already in use in the existing IEEE 802.11 family of standards [32]. The enhanced algorithm is known as enhanced distributed channel access (EDCA) and introduces the concept of quality of service (QoS) to ensure a high priority for latency-sensitive messages, such as ITS safety messages. QoS is achieved through the definition of various access category (AC) levels based on the required traffic priority, e.g., best effort traffic, safety/emergency notifications or video/audio traffic. More recently, the IEEE working group 1609 [33] was formed to define additional higher layers (above the IEEE 802.11p PHY/MAC layers) and to complement the features of the IEEE 802.11p standard. As shown in Figure 7, the resulting IEEE 1609 family of standards include [7]: (i) IEEE 1609.1 for enhancing resource management; (ii) IEEE 1609.2 for enabling security services; (iii) IEEE 1609.3 for providing routing and addressing services; (iv) IEEE 1609.4 for supporting multi-channel operations; (v) IEEE 1609.5 for layers management; and (vi) IEEE 1609.6 for the application facilities management. The combination of the IEEE 802.11p and IEEE 1609 standards is generally known as Wireless Access in Vehic \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{Characteristics} & \multicolumn{3}{c}{Vehicular Communication Technologies} \\  & 802.11p (WAVE) & 802.11 a/b/g/n (Wi-Fi) & Cellular (3G, LTE) \\ \hline Mode of operation & _Ad hoc_, Infrastructure & _Ad hoc_, Infrastructure & Infrastructure \\ Communication type & V2V, V2I & V2I & V2I \\ Bit rate & Up to 27 Mbps & Up to 54 Mbps & Up to 2 Mbps \\ Communication range & Up to 1000 m & Up to 100 m & Up to 15,000 m \\ Support for mobility & High & Low & High \\ Frequency bands & 5, 86 to 5.92 GHz & [2.4, 5.2] GHz & [800, 900, 1800, 1900] MHz \\ Channel bandwidth & [10, 20] MHz & 1 to 40 MHz & 25 MHz (GSM), 60 MHz \\  & & & (UMTS\({}^{1}\)) \\ Related standards & IEEE, ISO, ETSI & IEEE & ETSI, 3 GPP\({}^{2}\) \\ \hline \hline \end{tabular} \({}^{1}\) UMTS: Universal Mobile Telecommunications System  
\({}^{2}\) 3 GPP: 3 rd Generation Partnership Project  
\end{table} 
Table 2: Key enabling vehicular communication technologies (MAC/PHY). WAVE, Wireless Access in Vehicular Environments; V2V, vehicle-to-vehicle; V2I, vehicle-to-infrastructure. Similar ongoing standardization activities are also being pursued in Europe within the European Telecommunications Standards Institute (ETSI) TC ITS working group [10].