# A Survey of Autonomous Vehicles: Enabling Communication Technologies and Challenges
## 3 System Architecture for Autonomous Vehicles  
An ordinary vehicle can be converted into an autonomous one by adding some additional components including sensors that allow the vehicle to make its own decisions by sensing the environment and controlling the mobility of the vehicle [12; 14; 37; 46]. Figure 4 illustrates the overall communication process/protocol in AVs and also lists the sensors, actuators, hardware and the software control required. The protocol architecture, explained below, is composed of four main stages and enables a Level 5 fully autonomous vehicle where all the users are passengers. 1. Perception: This stage involves sensing of the AVs surrounding through various sensors and also detecting its own position with respect to the surroundings. In this stage, some of the sensors used by the AV are RADAR, LIDAR, camera, real-time kinetic (RTK), etc. The information from these sensors is then passed to the \begin{table}
\begin{tabular}{p{142.3 pt} p{284.5 pt}} \hline \hline [PERSON] et al., 2016 [40] & DSRC experimental demonstration for truck platooning is done. Different dynamic and static tests revealed that on hilly and curved roads packet delivery ratio is affected. Lower delivery ratio on straight paths is achieved due to the reflection of the truck with nearby vehicles. \\ \hline [PERSON] et al., 2016 [30] & C-V2X and DSRC are combined together to produce a hybrid architecture. It is concluded that the combination of both technologies can produce useful results in V2X communications. \\ \hline [PERSON] et al., 2016 [41] & ZigBee technology was tested and implemented for Forward Collision Warning System (FCWS) in low speed vehicles. \\ \hline [PERSON] et al., 2017 [12] & Categorising the levels of automation by explaining each level according to the SAE standard. \\ \hline [PERSON] et al., 2018 [14] & Perception and planning stages can be improved by implementing two inner loops for simultaneously localising and mapping. To enlarge the detection and range of the sensors, they also developed an algorithm to detect and calculate the range of the system. \\ \hline [PERSON] et al., 2018 [42] & Demonstrations on various simulators such as SUMO and NS-2.35 to prove the capacity of DSRC technology. After conducting different experiments they concluded that the performance of DSRC is much better than the Wi-Fi for medium-range communications. \\ \hline [PERSON] et al., 2018 [31] & 3 GPP calibrated simulator to evaluate the performance of 5G-NR in V2X communication. An increase in sub-carrier spacing is suggested to boost the system protection against interference. \\ \hline [PERSON] et al., 2019 [43] & The physical fundamentals, principal functioning and electromagnetic spectrum of sensors that are used to gather the external information of the vehicle are presented. The sensors are analysed on spider charts in order to compare and highlight their weaknesses. \\ \hline [PERSON] et al., 2019 [44] & VANETs security, architecture and challenges are discussed for traffic management system for vehicular network from malicious nodes and fake messages. \\ \hline [PERSON] et al., 2019 [32] & IEEE 802.11\(bd\) and 5G-NR are developed to overcome the disadvantages of DSRC and C-V2X technology and satisfy the diverse needs for V2X applications. \\ \hline [PERSON] et al., 2020 [33] & Basic road safety, architecture, key technologies and the standards of C-V2X are introduced. Technical evolution path from LTE-V2X to NR-V2X is covered. \\ \hline [PERSON] et al., 2020 [18] & Fair allocation of resources is of prime importance in wireless networks [45]. Resource allocation in vehicular networks has been surveyed in [18] and references therein. \\ \hline \hline \end{tabular}
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Table 3: \(Cont.\)recognition modules which process this information. Generally, the AV consists of adaptive detection and recognition framework (ADAF), a control system, LDWS, TSR, unknown obstacles recognition (UOR), vehicle positioning and localisation (VPL) module, etc.