Connected and Autonomous Vehicles in Smart Cities
Message Dissemination in Connected VehiclesAdvances in connected vehicles based on Vehicular Ad-hoc Networks (VANETs) in recent years have gained significant attention in Intelligent Transport Systems (ITS) in terms of disseminating messages in an efficient manner. VANET uses Dedicated Short Range Communication (DSRC) for disseminating messages between vehicles and between infrastructures. In general, DSRC uses a dedicated 5.9 GHz band for vehicular communication [1]. DSRC has one control channel responsible for sending critical messages like information on road accidents, traffic jams, roadblocks, and six service channels responsible for sending non-critical messages like personal messages. The DSRC bandwidth is composed of eight channels that consist of six 10 MHz service channels for non-critical communications, one 10 MHz control channel for critical communications, and one 5 MHz reserved channel for future uses. As a result, VANET emerged as a promising solution for of ensuring road safety.In a VANET environment, also known as connected vehicular environment, information is disseminated among the vehicles through messages. Two types of messages are disseminated among the vehicles: 1) periodic beacon messages and 2) event-driven messages [2,3]. Periodic beacon messages, also known as Basic Safety Messages (BSMs) include information like vehicle's position, speed, direction, acceleration, braking status, etc. Vehicles typically broadcast BSMs to all neighboring vehicles at an interval of 100ms to 300ms. The objective of broadcasting BSMs is to be aware of the neighboring vehicles. For example, in a high dense vehicular environment like a downtown region, every vehicle receives approximately 1000 BSMs per second. Event-driven messages are generated when a vehicle encounters an event such as accidents, traffic jam, roadworks, etc. [4].Three types of communication are possible in VANETs: 1) Vehicle to Vehicle (V2V) communication, 2) Vehicle to Infrastructure (V2I) communication , and 3) Infrastructure to Vehicle (I2V) communication . [5,6]. V2V and V2I communication depend on DSRC for disseminating messages among the vehicles. V2V communication is used when the vehicles are in the transmission range of each other where vehicles communicate with each other using a multi-hop technique . For example, when a vehicle encounters a dangerous situation such as road accidents, loss of traction, etc., messages are disseminated to the nearby vehicles using a multi-hop technique [7,8]. V2V communication is purely ad-hoc in nature since vehicles communicate with each other directly without any infrastructure. V2V is used for communication among vehicles. V2I is used for communicating with fixed infrastructure and long-distance communication. The components of V2I includes traffic lights, cameras, etc. V2I converts the available infrastructure into a smart infrastructure by incorporating various algorithms that use data exchange between vehicles and infrastructures. One such re...