Deterministic vehicular communications supported by the roadside infrastructure: a case study

Abstract

The development of wireless vehicular networks for cooperative Intelligent Transport Systems (ITS) opened the possibility of launching cooperative applications that can improve vehicle and road safety, passenger’s comfort and efficiency of traffic management. These applications exhibit tight latency and throughput requirements, for example safety critical services such as the Emergency Electronic Brake Light require guaranteed maximum latencies lower than 100 ms, while most infotainment applications require QoS support and data rates higher than 1 Mbit/s. Current wireless communication standards such as IEEE 802.11-2012 amendment 6 and ETSI-G5 have some drawbacks in what concerns their medium access control technique, which is based in CSMA/CA, particularly for high speed and high density environments. To deal with such environments, an infrastructured based TDMA protocol, the Vehicular Flexible Time Triggered protocol was proposed. In this chapter several protocol parameters are quantified, taking in account realistic scenarios and current wireless communication standards, that are applicable in these environments. To deploy such an infrastructured based network in an entire motorway might be expensive, therefore a concept of safety zone is used whenever there is a part of the motorway that is covered by road side units that implement the protocol. A worst case approach is used in order to prove that the V-FTT protocol has a bounded delay in what concerns the time occurred between a safety event detection and the instant of time of its reception by all vehicles travelling in the safety zone. With the exception of the lowest bit rate (3 Mbps), the V-FTT protocol has a guaranteed bounded delay under the maximum allowed latency of the most common safety vehicle applications.